BIO 235 midterm 1 study guide/BIO 235 midterm 1 study guide, Exams of Biology

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CHAPTER 1 Anatomy – the science of body structures and the relationship among them Physiology – The science of body functions – how body parts work Dissection – careful cutting apart of body structures to study their relationships Levels of Structural Organization: Chemical (letters of alphabet) – most basic level that includes atoms and molecules atoms → smallest units of matter that participate in chemical reactions molecules → two+ atoms joined together Cellular – (words) – molecules combine to form cells (basic structural and functional units of an organism that are composed of chemicals) - smallest living unit in the human body Tissue – (words put together to make sentences) - groups of cells and the materials surrounding them - work together to perform a function - four basic types: epithelial, connective, muscular, nervous Organ – (sentences make paragraphs) - two or more different types of tissues are joined together to form organs - stomach, skin, lungs, bones. Heart, brain System – (chapter in our language) - consists of related organs with a common function - ex. Digestive system (mouth, salivary glands, pharynx,etc.) - pancreas is part of both digestive and endocrine system Organism (book) - any living individual - all body parts functioning together Systems of the Human Body 11 essential systems of the human body Integumentary System - COMPONENTS → skin and associated structures (hair, fingernails, toenails, sweat glands, oil glands) - FUNCTIONS → protects body, regulates body temp, eliminates some waste, makes vit D, detects sensations (warmth, pain) Skeletal System - COMPONENTS → bones and joints of the body and associated cartilages - FIUNCTIONS → supports and protects body, provides surface area for muscle attachments, aids body movements, houses cells that produce blood cells, stores minerals and lipids Muscular System - COMPONENTS → skeletal muscle tissue (muscle attached to bone) - FUNCTIONS → participates in body movements, maintains posture, produces heat Nervous System - COMPONENTS → brain, spinal cord, nerves, eyes and ears - FUNCTIONS → generates action potentialsto regulate body activities, detects changes in bodys internal and external environment, interprets changes and responds by causing muscular contractions or glandular secretions Endocrine System - COMPONENTS → hormone producing glands (pineal gland, hypothalamus, pituitary gland, thymus, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries and testes) - FUNCTIONS → regulates body activities by releasing hormones (chemical messengers transported in blood from endocrine gland to target organ) Cardiovascular System - COMPONENTS → blood, heart and blood vessels - FUNCTIONS → heart pumps blood through blood vessels, blood carries oxygen and nutrients to cells and CO2 and waste away from cells, regulates acid-base balance, temp and water content of body fluids, blood helps defend against disease and repairs damaged blood vessels Lymphatic System and immunity - COMPONENTS → lymphatic fluid and vessels (spleen, thymus, lymph nodes, tonsils, cells that carry out immune responses) - FUNCTIONS → returns proteins and fluid to blood, carries lipids from gastrointestinal tract to blood, site for B and T cell maturation (protect against disease causing microbes) Respiratoy System - COMPONENTS → lungs, pharynx (throat), larynx (voice box), trachea (windpipe), bronchial tubes - FUNCTIONS → transfers oxygen from inhaled air to blood and CO2 vice versa, regulates acid-base balance of body fluids, produces sound through vocal cords Digestive System - COMPONENTS → organs of gastrointestinal tract (mouth, pharynx, esophagus, stomach, small/large intestine, anus) and accessory organs that assist in digestion (salivary glands, liver, gallbladder, pancreas) - FUNCTIONS → physical and chemical breakdown of food, absorbs nutrients, eliminates solid wastes Urinary system - COMPONENTS → kidneys, ureters, urinary bladder, urethra - FUNCTIONS → produces, stores, and eliminates urine, eliminates wastes and regulates volume and chemical composition of blood, maintains acid-base balance of body fluids, maintains body mineral balance, regulates production of red blood cells Reproductive Systems - COMPONENTS → gonads (testes/ovaries) and associated organs (female: uterine tubes, uterus, vagina, mammary glands, male: epididymides, ductus deferens, seminal vesicles, prostate, penis) - FUNCTIONS → gonads produce gametes (sperm/oocytes) that unite to form a new organism, gonads release hormones that regulate reproduction, associated organs transport and store gametes, mammary glands produce milk Basic Life processes of Human Body (6) Metabolism - sum of all the chemical processes that occur in the body - two phases: - catabolism → breakdown of complex chemical substances into simpler components - anabolism → building up complex chemical substances Responsiveness - bodys ability to detect and respond to changes Movement - motion of whole body, individual organs, single cells and tiny structures inside cells Growth - Increase in body size that results from an increase in the size of existing cells, increase in number of cells, or both Differentiation - development of a cell from an unspecialized to specialized state - stem cells (precursor cells) can divide and give rise to cells that undergo differentiation Reproduction - formation of new cells for tissue growth, repair, or replacement, or the production of a new individual Homeostasis condition of equilibrium in the body's internal environment due to the constant interaction of the body's many regulatory processes - important aspect of homeostasis is maintaining volume and composition of body fluids - intracellular fluid (ICF) → fluid within cells - extracellular fluid (ECF) → fluid outside the body cells - interstitial fluid → ECF that fills narrow spaces between cells of tissues How stress affects homeostasis psychological stresses in our social environment cause homeostatic imbalances that are mild and temporary in most cases and the body cells quickly restore balance in the internal environment through negative feedback systems Feedback Systems Atom → smallest units of matter that retain the properties and characteristics of the elements - Nucleus → dense central core of an atom - Protons → positively charged particles inside the nucleus - Electrons → negatively charged particles that move around the large space surrounding the nucleus - Neutrons → uncharged particles inside the nucleus Isotopes → atoms of an element that have different numbers of neutrons and therefore different mass numbers Ions → an atom that has a positive or negative charge because it has an unequal number of protons and electrons - either gives up or gains electrons Molecules → formed when two or more atoms from the same elements share electrons (ex. O2) Compound → substance that contains atoms of two or more different elements (ex H20) Free Radical → atom or group of atoms with an unpaired electron in the outermost shell - unstable, highly reactive, and destructive to nearby molecules Chemical Bonds → the forces that hold together the atoms of a molecule or a compound - likelihood that an atom will form a chemical bond with another atom depends of the number of electrons on its outermost shell → this shell is called the valence shell Ionic Bonds → oppositely charged ions are attracted to each other, the force of attraction that holds these ions together is an ionic bond - cation → a positively charged ion - anion → a negatively charged ion - electrolyte → ionic compound that breaks apart into positive and negative ions in solution Covalent bonds → two or more atoms share electrons rather than gain/lose them - can share 1,2, or 3 pairs of valence electrons - nonpolar covalent bond → when the two atoms share the electrons equally (bonds between two of the same types of atoms) - polar covalent bonds → sharing of electrons between two atoms is unequal (results in partial negative charge towards the atom that attracts electrons more) → this atoms has greater electronegativity Hydrogen Bonds → polar covalent bonds that form between hydrogen atoms with a partial positive charge and atoms with a partial negative charge (electronegative atoms) - result from positive and negative attraction of oppositely charged atoms rather than sharing of electrons (covalent) or gain/loss of electrons (ionic) - weakest type of bond Chemical Reaction → occurs when new bonds form or break between atoms - metabolism → all chemical reactions that occur in the body - body temp is too low for most chemical reactions to occur, so catalysts, chemical compounds that speed up chemical reactions by lowering the activation energy needed for a chemical reaction (ex. Enzymes) - catalysts also help orient particles so they collide at proper spots to make reactions occur Synthesis reaction (anabolism) when two or more atoms, ions, or molecules combine to form new and larger molecules - all the synthesis reactions in your body are called anabolism Decomposition reactions (catabolism) split up large molecules into smaller atoms, ions or molecules - all the decomp reactions in the body are called catabolism Exchange reaction reactions that consist of both synthesis and decomposition reactions ex. when compounds switch partners, they both decompose and synthesize Reversible Reaction Products can reverse to original reactants - indicated by two half-arrows pointing in opposite directions - some are reversible only under special conditions, which are written above or below the arrow Most chemicals in the body exist as either inorganic or organic compounds Inorganic compound → usually lack carbon and are structurally simple, have few atoms and cannot be used to perform complicated functions, and may have ionic or covalent bonds - includes water, salts, acids, and bases Water → most important/abundant inorganic compound in all living systems - most important property is its polarity (uneven valence electron sharing that creates electronegativity near oxygen atom and partial positive charge near hydrogen atoms) - water is a good solvent for ionized or polar substances due to its polar covalent bonds - solutes that are charged or contain polar covalent bonds are hydrophilic - molecules that contain nonpolar covalent bonds are called hydrophobic - water serves as a median in most chemical reactions and participates as a product or reactant in certain reactions - hydrolysis → enables dietary nutrients to be absorbed into body by decomposing large nutrients into smaller molecules by adding water molecules - dehydration synthesis reaction → two smaller molecules join to form a larger molecule and a water molecule is one of the products formed - water has a high heat capacity because it can absorb/release large amounts of heat with only a small change to its own temperature → this is due to the large number of hydrogen bonds in water - water is a major source of lubricating fluids throughout the body (needed in chest, joints, gastro) Mixture → elements or compounds that are physically blended together but not bound by chemical bonds Solution → a solvent dissolves a solute to make a solution Acid → substance that dissociates (separate into ions and become surrounded by water molecules) into one or more hydrogen ions (H+) and one or more anions - H+ is a single proton with one positive charge, therefore an acid is a proton donor - ex. HCl → H+ and Cl- Base → dissociates into one or more hydroxide ions (OH-) and one or more cations - removes H+from a solution, and is therefore a proton acceptor - ex. KOH → K+ and OH- Salt → when dissolved in water, dissociates into cations and anions, neither of which are H+ or OH- - acids and bases react with one another to produce salts - HCl + KOH → H+ + Cl- + K+ + OH- → KCl (salt) + H2O Homeostasis is maintained when intra and extracellular fluids contain balanced quantities of acids and bases - the more H+ is a solution, the more acidic it is - the more OH-, the more alkaline it is PH Scale → expresses the acidity or alkalinity of a solution - scale from 0 – 14 based on the concentration of H+ in moles/liter dissolved in a solution - ex. PH of 4 = 1x10^-7 moles/liter H+ - substance with pH of 7 (ex. Water) is neutral - substance with pH less than 7 is acidic, more than 7 is alkaline pH of fluids inside and outside of cells remains neutral due to buffer systems - convert strong acids or bases into weak acids or bases - chemical compounds called buffers do so by removing or adding protons (H+) carbonic acid-bicarbonate buffer system - important buffer system in the body as carbonic acid acts as a weak acid and bicarbonate acts as a weak base to provide or remove H+ in a solution as it enters the body Organic Compound → always contain carbon, usually contain hydrogen, and always have covalent bonds Carbohydrate function as a source of chemical energy for generating ATP needed to drive metabolic reactions - have 2:1 ratio of hydrogen to oxygen - include sugars, glycogen, starches and cellulose - carbon, hydrogen and oxygen are elements found in carbohydrates - three major groups → monosaccharides – simple sugars that contain 3-7 carbon atoms → end in “ose” (glucose, fructose, etc) → Disaccharides – simple sugars formed from the combination of two monosaccharides by dehydration sysnthesis → polysaccharides – from tens to hundreds of monosaccharides joined by dehydration synthesis → main polysaccharide is glycogen – made entirely of glucose monomers linked to one another by branching chains, stored in liver and skeletal muscles Lipids organic compounds that contain carbon, hydrogen and oxygen and have small proportion of electronegative oxygen atoms, resulting in fewer polar covalent bonds - most lipids are insoluble in water, only the smallest lipids can dissolve in blood plasma → lipoproteins – when lipids join with hydrophilic protein molecules to become more soluble in blood plasma - triglyceride → most plentiful lipids in the body that consist of two types of building blocks, one glycerol molecule and three fatty acid molecules → glycerol is a three carbon molecule that is the backbone of a triglyceride → three fatty acids removes water molecule during dehydration synthesis when forming triglyceride and attaches to carbons atoms on glycerol - Fatty acids → smallest lipids and are used to synthesize triglycerides and phospholipids → can be catabolized to generate ATP → can be either saturated (single covalent bond between carbon atoms which means they are saturated in H+) or unsaturated (contains 1+ double covalent bond between carbon atoms and has a kink at site of double bond) - Phospholipid → have a glycerol backbone and two fatty acid chains attached to first 2 carbons → third carbon contains a phosphate group that links a nitrogen, making it polar and can form hydrogen bonds with water molecules (known as polar head and is hydrophilic) - phospholipids are amphipathic because they contain polar and non-polar parts - Steroids → have four rings of carbon atoms and cells synthesize steroids from cholesterol → cholesterol, estrogens, testosterone, cortisol, bile salts and vit D are sterols → cholesterol – has large nonpolar region and is needed for cell membrane structure - Eicasanoids → lipids derived from 20-carbon fatty acid called arachidonic acid-base → two subclasses: → prostaglandins – modify response to hormones, contribute to inflammatory response, regulate body temp → leukotrienes – participate in allergic and inflammatory responses Proteins large molecules that contain carbon, hydrogen, oxygen and nitrogem functions: (SRCITC) - form structural framework of body parts - hormones that regulate various physiological processes - allow contraction of muscle cells, which produces movements - boosts immunity against foreign substances - transports vital substances through body - catalyze biochemical reactions Amino Acids → 20 essential protein monomers that has hydrogen atom and amino group, acidic carboxyl group and a side chain attached to a central carbon atom - minimum 2 carbon and 1 nitrogen atom Peptide Bond → covalent bond joining each pair of amino acids → as peptide bond is formed, water molecule is removed (dehydration synthesis) → dipeptide = two amino acids combine → tripeptide = three amino acids combine → peptide = further amino acid additions (4-9) → polypeptide = 10-2000 amino acid additions Levels of structure in proteins primary → amino acids linked by covalent peptide bonds to form polypeptide chain secondary → repeated twisting/folding of amino acids in polypeptide chain tertiary → three-dimensional shape of polypeptide chain quaternary → arrangement of two or more polypeptide chains if a protein encounters an altered environment, it may unravel and lose its structural shape → denaturation Nucleic Acid organic molecules that contain carbon, hydrogen, oxygen, nitrogen and phosphorus - two types: → Deoxyribonucleic acid (DNA) – forms inherited genetic material inside each human cell → Ribonucleic Acid (RNA) – single stranded and relays info from genes to guide each cells synthesis of proteins from amino acids → sugar in RNA is called pentose ribose - nucleic acid is a chain of repeating monomers called nucleotides - each cell maintains different concentrations of certain substances on either side of the membrane → the difference in concentration is called the concentration gradient the combined influence these gradients have on movement of an ion is the electrochemical gradient → passive process – substance moves down electrical or concentration gradient using only its own kinetic energy → diffusion – random mixing of particles in a solution due to their kinetic energy, a solute which is in high concentration in one area of a solution will diffuse to an area of low concentration until it is at equilibrium → diffusion rate is affected by many factors including: → steepness of concentration gradient → temperature → mass of diffusing substance → surface area → diffusion distance types of diffusion (3): → simple diffusion – nonpolar and lipid-soluble substances move through the lipid bilayer without the help of proteins → facilitated diffusion – integral membrane protein helps the substance across the membrane. Can be either channel or carrier membrane protein → channel-mediated facilitated diffusion – membrane channel called an ion channel allows inorganic ions that are too hydrophilic to penetrate nonpolar interior of lipid bilayer (K+, Na+, CL-. Ca2+) → osmosis – diffusion of a solvent (water) through a permeable membrane → moves between phospholipid molecules via simple diffusion, or; → moves through aquaporins – integral membrane proteins that act as water channels → osmotic pressure is the pressure exerted by the water onto the membrane → tonicity – ability of a solution to alter a cell's shape by altering the cell's internal water volume → isotonic solution – maintains cell's water volume → hypotonic solution – contain lower concentration of non-penetrating solutes and water rushes in, causing the cell to burst (hemolysis) → hypertonic solution – contain higher concentration of non-penetrating solutes and sucks water out of cell, causing them to shrink (crenation) → active process – cellular energy is used to drive the substance “uphill” against its concentration or electrical gradient → cellular energy is in the form of ATP (adenosine triphosphate) → primary active transport – energy derived from hydrolysis of ATP changes the shape of a carrier protein which pumps a substance across a plasma membrane against the concentration gradient → most prevalent pump is sodium-potassium pump (Na+/K+ATPase) - K+naturally flows out of cell, Na+ naturally flows in so pump transports these ions against their cconcentration gradient to keep K+ concentration high and Na+ concentration low in the cytosol → secondary active transport – secondary proteins harness the energy of Na+ and change shape to allow Na+ and other substance back into the cell. Na+ goes down its gradient while the other substances go “uphill” → vesicular transport – substances are transported in sacs in between cell structures and out into extracellular fluid. → endocytosis – materials move into the cell in a vesicle formed from the plasma membrane - 3 types: → receptor-mediated endocytosis – vesicles form after receptor protein in plasma membrane recognizes and binds to a particle in extracellular fluid → phagocytosis – body cell (called phagocyte) engulfs large solid particles such as worn out cells or viruses by extending plasma projections (pseudopods) to engulf the particle → pinocytosis – tiny droplets of extracellular fluid are taken up by the plasma membrane which forms a vesicle on its own with no help exocytosis and transcytosis → exocytosis releases materials from the cell, the important cells being secretory cells (secretions) and nerve cells (neurotransmitters). In Transcytosis vesicles undergo endocytosis to get through one side of the cell and exocytosis once on the other side Cytoplasm all cellular contents between the plasma membrane and the nucleus → has two parts: cytosol and organelles cytosol → fluid portion of cytoplasm that surrounds organelles and is the site for many chemical reactions → cytoskeleton is a network of protein filaments that extend through the cytosol → microfilaments – thinnest element of cytoskeleton and provide mechanical support and generate movement. They contain microvilli which provides mechanical support for cell extensions → intermediate filament – strong filament that stabalizes the position of organelles → microtubules – largest filament that helps determine cell shape organelles → specialized structures in the cell that perform specific functions in cellular growth, maintenance and reproduction → centrosome – consist of two centrioles and pericentriolar material and play role in cell division → cilia and flagella – microtubes that move to cause steady fluid movement along cell's surface → flagella are longer and move an entire cell (ex. Sperm) → ribosomes – sites of protein synthesis → endoplasmic reticulum – rough ER and smooth ER are encolsed tubules/sacs that extend through cytoplasm → rough ER synthesize glycoproteins and phospholipids → smooth ER synthesize fatty acids and steroids →Golgi complex – 3-20 flat sacs with bulgy edges that take proteins from rough ER and modify/sort/transport them and discharge them into extraceullular fluid → lysosomes – membrane-enclosed vesicles that form from the golgi complex and perform autophagy (digest worn-out cells) → peroxisomes – contain enzymes that can oxidize organic substances → proteasomes – continuous destruction of unneeded, damaged or faulty proteins → mitochondria – generate ATP through aerobic cellular respiration and play a role in apoptosis (genetically programmed death of a cell) Nucleus spherical or oval-shaped structure that is most prominent structure of a cell - nuclear envelope seperates nucleus from cytoplasm - nuclear pores are circle arrangement of proteins around a large opening that control substance movement between nucleus and cytoplasm - nucleus contains most of the cell's genes → controls cellular structure → directs cellular activities → produces ribosomes in nucleoli - genes are arranged along chromosomes which are made up of a threadlike complex called chromatin Protein Synthesis protein synt requires transcription of a gene's DNA into RNA and translation of RNA into a sequence of amino acids Transcription → DNA gives genetic info and it is copied into a sequence of codons in the nucleus → 3 types: messenger RNA, ribosomal RNA, Transfer RNA Translation → mRNA molecule binds to ribosome and a nucleotide sequence specifies the amino acid sequence of a protein Cell Division process by which cells reproduce themselves Somatic Cell Division - cell undergoes interphase (when the cell doesnt divide), nuclear division (mitosis – where the cell divides and gains a genome) and a cystoplasmic division (cytokinesis) to produce two genetically identical cells, each with same chromosomes as original cellular → interphase has 3 stages: → G1 phase – cells duplicate organelles and components and chromosome replication begins → S phase – replication of DNA and centrosomes → G2 phase – cell growth continues and chromosome replication is complete → mitosis has 4 stages: → prophase – chromatin fibers condense and shorten into chromosomes → metaphase – mitotic spindle aligns centromeres chromatid pairs → anaphase – centromeres split and move towards opposite poles of the cell → telophase – nuclear envelopes and chromosomes resume chromatin form → cytokinesis – cytoplasm divides into 2 equal portions Reproductive cell division each new organism is the result of fertilization, one gamete from each parent - meiosis → reproductive cell division in gonads produces gametes with ½ amount of chromosomes so the union doesn't double the amount → known as haploid cells → 2 phases of reproductive cell division, meiosis I and meiosis II → each have prophase, metaphase, anaphase, telophase (labelled accordingly, I and II) → single diploid cell undergoes meiosis I and II to produce 4 haploid cells → genetically different from the diploid cellular Cell diversity - size and shape of cells can vary significantly - measured in micrometers - may be round, oval, flat, cubed, etc Cancer - group of diseases characterized by uncontrolled or abnormal cell division - attack basement membrane of tissue Chapter 4 Tissue → group of cells that have a common origin and function together to carry out specific activities 4 different types Epithelial tissues → covers body surfaces and line hollow organs, body cavities and ducts. They form glands and allow the body to interact with internal and external environment Connective tissues → protect and support the body and organs. Bind organs together, store energy reserves as fat and provide immunity to disease-causing organisms Muscular tissues → composed of cells specialized for contraction and generation of force. Generate heat for the body Nervous tissue → detects change in and out of body and responds by generating nerve impulses that activate muscular contractions and glandular secretions Cell junctions → contact points between the plasma membranes of tissue cells 5 different types tight junctions → weblike strands of transmembrane proteins that seal off passageways between cells Adherens junctions → contain dense layer of proteins on inside of plasma membrane called plaque that attach to membrane proteins and cystoskeleton. Transmembrane proteins called cadherins join the cells and make adhesion belts Desmosomes → have plaque and cadherins that attach cells to one another, but the plaque attaches to intermediate filaments which are made of keratin exocrine glands → secretions are released into ducts that empty onto surface of lining epithelium, such as skin surface → structurally classified as either unicellular or multicellular → functionally classified based on how their secretions are released → merocrine glands – synthesized on ribosomes, processed sorted and packed by golgi complex, and released from the cell in secretory vesicles → apocrine glands – accumulate their secretory product at the surface and pinch off → holocrine glands – accumulate secretory product in cytosol and then mature cell ruptures and becomes secretory product. Cell is then replaced through cell division Connective Tissues - consist of extracellular matrix and cells → extracellular matrix – material located between cells and consists of protein fibers and ground substances → Cells → contain immature class of cells called fibroblasts (large flat cells with branching processes, most common in connective tissues) that retain the capacity for cell division and secrete the extracellular matrix that is characteristic of the tissue → macrophage – irregular shape with short branching projections and engulf bacteria and cellular debris → plasma cells – secrete antibodies (proteins that attack or neutralize foreign substances in the body) → mast cells – produce histamine which dilates small blood vessels as part of an imflammatory responses → adipocytes – cells stored in tryglycerides → white blood cells – migrate from blood to connective tissue in certain conditions ground substances → component of connective tissue between the cells and fibers → may be fluid, gelatinuous or calcified → supports and binds cells, stores water and provides medium for exchange fibers → collagen fibers, elastic fibers and reticular fibers function to strengthen and support connective tissues → collagen fibers – strong and resist pulling forces but are also flexible (bone, cartiledge, tendons, ligaments → elastic fibers – smaller than collagen and branch together to form a fibruous network (skin, blood vessels, lung tissue) → reticular fibers – consist of a bundle of collagen and provide support in the walls of blood vessels Types of connective tissues loose connective tissue → mature connective tissue with loosely arranged fibers between cells → areolar tissue – fibers arranged randomly and different cells embedded in semifluid ground substance → located in every body structure and provide strength, elasticity and support → adipose tissue – cells that are derived from fibroblasts and store triglycerides → located wherever areolar tissues are and reduces heat loss, serves as energy reserves and protects organs → reticular tissue – interlacing network of reticular fibers and reticular cells → located in framework (stroma) of liver, spleen, lymph nodes and forms framework of organs while binding smooth muscle tissue cells Dense connective tissue → contains more fibers which are thicker and more densely packed → dense regular tissue – collagen fibers regularly arranged in bundles and are not living (damaged tendons take long to heal) with many fibroblasts → forms tendons, ligaments and aponeuroses and provides strong attachment between structures → dense irregular tissue – collagen fibers irregularly arranged with few fibroblasts → occurs in sheets such as tissue beneath skin and around muscles and provides pulling strength in many directions → elastic connective tissue – elastic fibers with fibroblasts between fibers → located in lung tissue, walls of elastic arteries, trachea, bronchial tubes and allows stretching of various organs and is strong and can be recoiled cartiledge → dense network of collagen fibers and elastic fibers firmly embedded in chondroitin sulfate → can endure most stress compared to other connective tissues → has few cells and large amounts of extracellular matrix, but doesn't have nerves or blood vessels in extracellular matrix → cells are called chondrocytes and they are a cartilaginous cell that secretes a gel-like matrix that surrounds and imprisons the cartiledge → hyaline cartiledge – contains a resilient gel as a ground substance and appears as bluish-white substance located in lacunae (little lakes) → most abundant cartiledge in body, located at ends of bones, ribs, nose, bronchi → provides smooth surface for movement at joints, flexibility and support → fibrocartiledge – chondrocytes scattered among thick bundles of collagen fibers, lacks perichondrium → located in intervertebral discs, menisci, pubic anterior → strongest type of cartiledge and provides support in joining structures together → elastic cartiledge – chondrocytes in a thread-like network of elastic fibers within extracellular network, contains perichondrium → located in epiglottis, outer ear, audio tubes → provides strength and elasticity and maintains shape Bone tissue basic unit of a compact bone is called osteon or Haversian system has 4 parts: → lamellae – concentric ring that consist of mineral salts and give bone its hardness/strength → lacunae – small spaces between lamellae that contain oseocytes (mature bone cells) → canalicuni – tiny canals for the process of osteocytes → central canal – contains blood vessels and nerves Blood tissue connective tissue with liquid extracellular matrix and formed elements has 4 parts: → blood plasma - extracellular matrix that is pale yellow and contains mostly water and all other parts of blood tissue → red blood cells – transport oxygen to body cells and take CO2 away → white blood cells – performs phagocytosis (engulfing particle to form a vesicle), and helps with immunity and allergic reactions → platelets – participate in blood clotting lymph extracellular fluid that flows in lymphatic system and is a connective tissue → similar to blood but has much less protein MEMBRANE flat sheets of pliable tissue that cover or line a part of the body Epidermial membrane are types that have an epithelial layer and underlying connective tissue layer: 3 types: → mucous membrane (mucosa) – lines a body cavity that opens directly to the exterior - line entire digestive system, respiratory, reproductive and urinary tracts → serous membrane (serosa) – lines a body cavity that does not directly open to the exterior (thoracic or abdominal cavity) and the organs that lie within them - have two layers: parietal layer (lines cavity wall) and visceral layer (lines organs) - serous membrane lining the thoracic cavity and lungs is called pleura - serous membrane lining the heart cavity is called pericardium - serous membrane lining abdomen organs is called peritoneum → cutaneous membrane (skin) – covers entire surface body and consists of superficial layer called epidermis and a deeper portion called the dermis - synovial membrane lacks epithelium and is therefore not an epidermial membrane → they line joint cavities and consist of synoviocytes (layer of discontinued cells) and connective tissue (areolar and adipose) → secrete synovial fluid which lubricates cartiledge at joints and removes joint debris MUSCULAR TISSUE muscle fibers or myocotes which use ATP to generate force and produce body movement, maintain posture, and provide protection - 3 types: → skeletal muscle tissue – long cylindrical striated fibers with multiple nuclei on exterior that are considered voluntary because it can contract or relax through conscious control → attached to bones by tendons → functions in motion, posture, heat control → cardiac muscle tissue - branched striated fibers with only one nucleus - attached together by intercalated disc, which is transverse thickenings of plasma membrane that contain desmosomes and gap junctions. Desmosomes strengthen tissues and hold fibers together during contractions and gap junctions provide route for quick muscle action potentials → located in the heart wall and pumps blood to entire body involuntary → smooth muscle tissue – involuntary non-striated fibers that are spindle-shaped, tapered at ends and have one central nucleus. - connected by gap junctions and provide powerful contractions when pumping in unison - can contract individually when gap junctions are not present → found in intestines, iris of eye, urinary bladder, airway to lungs, blood vessels → function in motion of pushing food, etc. down a tube NERVOUS TISSUE only consists of two types of cells: neurons and neuroglia Neurons – nerve cells that convert stimuli to electrical signals called nerve action potentials and conduct these action potentials to other neurons, muscle tissues and glands - consist of three parts: cell body, dendrites and axon → cell body – contains nucleus and other organelles → dendrites – tapering, highly branched extensions of the cell body that are the receiving/input portion of a neuron → axon – single, thin long process that provides the output to other neurons or tissues Neuroglia – do not generate or conduct nerve impulses but have supportive functions Homeostatic imbalances in tissues tissues each have a different recovery system which is used to restore homeostasis when there is an imbalance, such as a wound or thinning/ weakening tissues. Epithelial tissues have a constant capacity for renewal, while connective, muscle and nervous tissues have a decreasingly poorer capacity for renewal and homeostatic balance - main cause of homeostatic imbalance is disorders, which for epithelial tissues are usually specific to an organ - main connective tissue disorder is an autoimmune disease → ex rheumatoid arthritis - attacks synovial membrane of joints → SLE (lupus) – chronic inflammatory disease of connective tissue Atrophy → a decrease in the size of cells, which results in a decrease of the organ or tissue Hypertrophy → increase in the size of a tissue because its cells enlarge without undergoing division - cells of these glands release sweat into hair follicles or onto the skins surface through pores - two main types, eccrine or apocrine glands → eccrine sweat gland – simple, coiled, tubular glands that are most common and help regulate body temp through evaporation → called thermoregulatory sweating → sweat that evaporates from the body before it is perceived as moisture is called insensible perspiration → sweat that is perceived as moisture is called sensible perspiration → apocrine sweat glands – simple coiled tubular glands that secrete a milky colour sweat in armpits and genitals and occurs during sexual activity, emotional stress and cause body odour when mixed with skin bacteria → ceruminous gland – sweat glands in the external ear that produce a waxy lubricant which opens up into the sebaceous glands, and when the lubricants from both glands mix together they produce cerumen, also known as earwax → impedes the entrance of foreign substances and waterproofs the ear NAIL plates of tightly packed, dead keratinized epidermal cells that form over the digits and consist of a nail body, free edge, and nail root → nail body – visible portion of the nail → free edge – part of nail that extends past the digits → nail root – portion of nail that is embedded in a fold of skin → lunula – crescent-shaped white area that has thicker epithelium close to nail root → hyponychium – stratum corneum located under free edge and secures nail to fingertip (aka nail bed) → eponychium – stratum corneum that extends from the nail wall (aka cuticle) → nail matrix – part of nail under root and body that produces new nail cells FUNCTIONS OF THE SKIN thermoregulation → homeostatic regulation of body temp → skin does this in 2 ways: frees sweat at surface (released by eccrine glands), and adjusts the flow of blood in the dermis (dilates or constricts blood vessels) protection → keratin protects underlying tissues → lipids inhibit evaporation of water from skins surface → sebaceous glands release oil to protect skin from drying cutaneous sensations → sensations that arise in the skin such as touch, pressure, vibration and pain Excretion and absorption → excretes 400 mL of water per day as well as salts, CO2, ammonia and urea → lipid-soluble materials are absorbed into skin, such as fat-soluble vitamins (A,D,E,K), heavy metal salts (lead, mercury) Synthesis of Vitamin D → the synthesis of Vitamin D requires the skin to activate a precursor molecule through UV rays of sun (10-15 min 2X a week) SKIN WOUND HEALING Epidermal wound healing – wound that only has slight damage to epidermal cells → basal cells surrounding the wound break contact with the basement membrane → they enlarge and migrate across the wound until they meet the opposite side → upon meeting a cellular response called contact inhibition happens, which stops the migration deep wound healing – injury that extends to dermis and subcutaneous layer → 4 phases: → inflammatory phase – blood clot forms in wound to unite edges → migratory phase – clot becomes a scab and epithelial cells migrate beneath the scab to bridge the wound → granulation phase – the tissue then fills the wound → proliferative phase – extensive growth of epithelial cells beneath the scab and continued blood vessel growth → maturatiuon phase – scab peels off once epidermis is back to normal thickness Skin Cancer - excessive exposure to UV radiation from sun or tanning 3 types: → basal cell carcinomas – tumors from cells in stratum basale of epidermis (most common) → squamous cell carcinomas – tumors arise in cells of stratum spinosum → malignant melanomas – arise from melanocytes and kill within months Burns tissue damage caused by excessive heat, electricity, radioactivity, or chemicals that break down proteins in the skin → first-degree burn – involves only the epidermis → second-degree burn – destroys epidermis and part of the dermis → third-degree burn – destroys epidermis, dermis and subcutaneous layer - seriousness of a burn is determined by depth and extent of area involved, as well as age and health of victim Cold sore → lesion in oral mucuos membrane caused by type I herpes. Triggered by hormonal changes, UV light, stress eczema → inflammation of skin characterized by patches of red, blistering, itchy skin hives → reddened elevated patyches of skin that are often itchy. Caused by infections, trauma, stress, allergies wart → mass produced by uncontrolled growth of epithelial cells caused by a papillomavirus Chapter 6 Bone tissue makes up 18% of human body weight Main functions of the skeletal system → support – structural framework of the body that supports soft tissues and provides attachment points for tendons → protection – protects the most important internal organs from injury → assistance in movement – skeletal muscles contract and pull on bone to create movement → mineral homeostasis (storage and release) – bone tissue stores many minerals and tissues (calcium and phosphorus) which contribute to bone strength. On demand these minerals are released into the blood by bone to maintain homeostasis → blood cell production – connective tissue called red bone marrow produces red blood cells, white blood cells and platelets. This process is called hemopoiesis. Red bone marrow is located in pelvis, ribs, sternum, vertabrae, skull, humerus, and femur → triglyceride storage – as we age, red bone marrow turns into yellow bone marrow. Yellow bone marrow consists of adipose cells, which store triglycerides. Triglycerides are chemical energy reserves PARTS OF A LONG BONE → diaphysis – the bones shaft or body → epiphysis – proximal and distal ends of the bone → metaphyses – regions between the disphysis and the epiphysis → contains a epiphyseal plate which is a layer of hyaline cartiledge that allows the diaphysis of bone to grow → articular cartiledge – thin layer of hyaline cartiledge (thin seethrough cartiledge) covering part of the epiphysis where the bone forms a joint with another bone → reduces friction and absorbs shock at free-moving joints → periosteum – tough connective tissue sheath that surrounds the bone surface wherever it is not covered by articular cartiledge → medullary cavity (marrow cavity) – hollow cylindrical space within diaphysis that contains fatty yellow bone marrow nd reduces weight of the bone → endosteum – thin membrane that lines the medullary cavity that contains bone-forming cells and small amount of connective tissue HISTOLOGY OF BONE TISSUE - bone tissue is 55% crystallized mineral salts, the most abundant being calcium phosphate. It combines with another mineral salt called calcium hydroxide to form crystals of hydroxyapatite - hydroxyapitite continues to form with other mineral salts and crystallize in the extracellular matrix, hardening the tissue. This is called calcification - collagen fibers are needed for this calcification to occur as the mineral salts harden in the spaces around the fibers Four types of cells are present in bone tissue: → osteogenic cells - unspecialized bone stem cells that are unique in that they undergo cell division. The resulting cells develop into osteoblasts → osteoblasts – bone-building cells that secrete collagen fibers needed to build the extracellular matrix. They also initiate calcification. They surround themselves with extracellular matrix and turn into osteocytes → osteocyte – main cells in bone tissue and maintain daily metabolism → osteoclast – huge cells derived from fusion of many monocytes and are concentrated in endosteum. They perform resoprtion, the breakdown of bone extracellular matrix compact bone tissue → contains few spaces and is the strongest form of bone tissue - found beneath the perisoteum and makes up the majority of the diaphyses of long bones - provides protection and support and resists stress → composed of repeating structural units called osteons or haversian systems → osteons consist of a concentric lamellae (circular plates of mineralized extracellular matrix that surround a small network of blood vessels) that are arranged around a central (haversial) canal → between the concentric lamellae are small spaces called lacunae which contaion osteocytes → canaliculi are small channels filled with extracellular fluid that radiate from the lacunae - this sytem provides routes for nutrients and oxygen to reach osteocytes and remove waste Spongy bone tissue → do not contain osteons and is located in the interior of a bone - consists of lamellae that are arranged in irregular patterns of thin columns called trabeculae - trabeculae are precisely oriented along lines of stress and support and protect red bone marrow so hemopoiesis can occur BLOOD AND NERVE SUPPLY OF BONE - blood vessels (abundant in bones containing red bone marrow) pass into bones from the periosteum → nutrient foramen – hole in compact bone where the nutrient artery and vein can enter near the center of the diaphysis → nutrient artery – passes through the nutrient foramen, splits into proximal and distal branches and supply the inner compact bone tissue, spongy bone tissue, and red bone marrow with nutrients → nutrient vein – 1-2 veins accompany the nutrient artery and exit through the diaphysis BONE FORMATION → ossification – the process by which bone forms - occurs in 4 situations: → initial formation of bones in a fetus → bone growth during infancy until adulthood → remodeling of bone → repair of fractures - ossification in embryo/fetus occur in two different methods: → intramembranous ossification – bone forms directly within mesenchyme 4 steps: Chapter 7 two bone divisions in the human body: axial and appendicular axial → 80 bones that lie around a longitudinal axis that goes down the center of the body - cranium, face, sternum, vertebrae, ribs appendicular – 126 bones that consist of the upper and lower limbs and the bones forming the girdles that connect the limbs to the axial skeleton TYPES OF BONES long bones → greater length than width, consist of a shaft and a variable nukber of extremities, and are slightly curved - consist of compact bone in diaphysis and spongy bone in epiphysis short bones → somewhat cube shaped and equal in length and width - consist of spongy bone tissue except at the surface, which has a thin layer of compact bone tissue flat bones → thin and composed of two parallel plates of compact bone tissue enclosing a layer of spongy tissue - provide lots of protection and extensive areas for muscle attachment irregular bones → have complex shapes and cant be grouped (ex. Vertebrae) sesamoid bones → develop in tendons where there is considerable friction, tension, and physical stress - not always ossified and are very small, except for patellae in knees - protect tendons from excessive wear and tear sutural bones → small bones located in joints between certain cranial bones BONE MARKINGS 2 major types: → depressions and openings – allow the passage of soft tissue or form joints - blood vessels, nerves, ligaments , tendons - fissure → narrow slit between adjacent parts of bones which blood vessels or nerves passes through - foramen → opening through which blood vessels or nerves pass - fossa → shallow depression - sulcus → furrow along bone which accommodates nerve, blood vessel or tendon - Meatus → tube-like opening → processes – outgrowths that form joints or serve as attachment points for connective tissue - ligaments and tendons - condyle → large round protuberance with smooth articular surface at end of bone - facet → smooth, flat, slightly concave or convex articular surface - head → rounded articular projection supported on neck of bone - crest → prominent ridge or elongated projection - epicondyle → roughened projection above condyle - line → long narrow ridge or border, less prominent than a crest - spinous process → sharp, slender projection - trochanter → very large projection - tubercle → variable sized rounded projection - tuberosity → variably sized projection with rough bumpy surface BONES OF THE SKULL cranial bones stabalize the brain, blood vessels, and nerves through attachment to membranes - frontal bone (83) - supraorbital margin (top of eye socket) - parietal bones x2 – (78) - temporal bones x2 – (58) - zygomatic arch (4) - zygomatic bone (75) - external auditory meatus (posterior to sphenoid) - mastoid process (60) - internal auditory meatus (71) - occipital bone (24) - foramen magnum (21) - occipital condyles (25) - sphenoid bone (37) - optic foramen ( - ethmoid bone (90) - nasal conchae (93) - maxilla (97) - lacrimal bone (94) - lacrimal fossa (17) - palatine bones (106,107) - mandible (114) - ramus (128) - angles (129) - coronoid process (133) - condylar process (132) - alveolar process (126) - nasal septum (12) Nasal septum → bone and cartilage that divides right and left side of nasal cavity 3 components: → vomer (96) → septal cartilage (12) → perpendicular plate of the ethmoid bone (90) Orbit → seven bones of the skull join to form each orbital cavity, or eye socket - 3 cranial bones: → frontal (83) → sphenoid (37) → ethmoid (90) - four facial bones: → palatine (106,107,103) → zygomatic arch (4), zygomatic bone (108,112,4) → lacrimal (94) → maxilla (97) 1. frontal and sphenoid bones → roof 2. zygomatic and sphenoid bone → lateral wall 3. maxilla, zygomatic, palatine → floor 4. maxilla, lacrimal, ethmoid, sphenoid → medial wall frontal bone forms the forehead (anterior part of cranium), roofs of the orbits, and most of the anterior part of the cranial floor → 7 bones join to form an orbit, which each eye has → frontal, sphenoid, ethnoid bones → palatine, zygomatic, lacrimal, matrix → 5 openings in each orbit → optic foramen, superior orbital fissure, inferior orbital fissure, supraorbital foramen, and lacrimal fossa SUTURES a suture is an immovable joint in an adult that holds bones together → coronal suture – holds the frontal bone and both parietal bones → sagittal suture – unites two parietal bones on the superior midline of the skull → lamboid suture – unites two parietal bones to the occipital bone → squamous sutures x2 – unite parietal bones and temporal bones on the lateral part of skull SINUSES - paranasal sinuses → cavities within certain nasal and cranial bones near the nasal cavity Chapter 8 Pectoral/shoulder girdles → clavicle – 155 → sternal end – 155c → acromial end → scapula – 154 → spine of scapula – 154a → acromial – 154b → glenoid cavity → scapular notch – 154n → lateral border – 154g → medial border – 154 → superior angle – 154e → inferior angle – 154f → coracoid process – 154k → supraspinous fossa – 154c → infraspinous fossa – 154d → subscapular fossa Upper limbs → each limb has 30 bones humerus → 156 humerus head → 156a glenohumeral joint → connects glenoid cavity of scapula and humerus head anatomical neck → surrounds the humerus head greater tubercle → 156d lesser tubercle → 156e intertubercular sulcus → 156f deltoid tuberosity → 156g capitulum → connects to ulna and radius radial fossa → groove that articulates with head of the radius when bent trochea → articulates with trochlear notch of ulna coronoid fossa → receives coronoid process of ulna when bent olecran fossa → receives olecran of ulna when arm is straightened ulna → 157 olecranon → 157a coronoid process → head of ulna that articulates wioth coronoid fossa of humerus when arm is bent trochlear notch → inside head of ulna and articulates with trochlea when flexion radial tuberosity → point of attachment for tendons of bicep muscles Carpals - 8 small bones joined together by ligaments sphenoid is most easily injured Pelvic (hip) girdle - consists of two hip bones called coxal that unite anteriorly at the pubic symphysis joint ansd posteriorly at the sacroiliac joints -complete ring including two coxals, pubic symphysis, and sacrum forms the bony pelvis - bony pelvis supports vertebral column and lower abdominal organs - each hip bone consists of ilium, pubis, and ischium which fuse at age 23 coxal bone → 171 pubic symphysis → catrilage joint seperating pubis bones bony pelvis → entire unit pubis ilium → 172 anterior superior iliac spine – 175d anterior inferior iliac spine – 175e iliac fossa – 176 ischium – 174 greater sciatic notch – 184 lesser sciatic notch – 185 ischial tuberosity – 182 obturator foramen – hole in between pubis and ischium pelvic inlet – opening between sacrum and pubis along pubic crest, divides bony pelvis into superior and inferior portions false (greater pelvis) – portion of pelvis superior to pelvic brim true (lesser) pelvis – portion of pelvis inferior to pelvic brim pelvic outlet – opening inferior to the pelvic brim LOWER LIMB - has 30 bones femur – strongest bone in the body, head articulates with the acetabelum of the hip bone → angled medially and therefore knee joint is closer to the midline than the hip joint, especially in women because their hips are broader greater trochanter lesser trochanter gluteal tuberosity linea aspera medial condyle lateral condyle medial epicondyle lateral epicondyle patella tibia lateral condyle medial condyle tibial tuberosity medial malleolus fibula lateral malleolus tarsal bones → 7 tarsal bones tarsal calcaneus navicular cuboidal third cuneiform (lateral) second cuneiform (intermediate) first cuneiform (medial) metatarsals I-V phalanges (proximal, middle, distal) hallux Arches of the foot → Longitudinal – arch from posterior to anterior of foot → medial part – rises from calcaneous → tarsal → navicular → 3 cuneiforms → head of 3 medial metatarsals → larteral part – starts at calcaneus → cuboidal → 2 lateral metatarsals → transverse arch – goes from medial to lateral aspect of foot origination at navicular, 3 cuneiforms, base of metatarsals KNEE JOINT - modified hinge joint that consists of three joints within a single synovial cavity 1. lateral tibiofemoral joint – between lateral condyle of femur, lateral miniscus, and lateral condyle of tibia 2. medial tibiofemoral joints – between medial condyle of femur, miniscus and tibia 3. intermediate patellofemoral joint – between patella and patellur surface of femur tibial collateral ligament → flat ligament on medial surface of joint that extends from medial condyle of femur to medial condyle of tibia Fibular collateral ligament → rounded ligament on lateral side of joint that extends from lateral condyle of femur to lateral side of fibula head anterior cruciate ligament (ACL) → extends posteriorly and laterally from the middle of the knee back to the medial surface of the lateral condyle of the femur. Limits hyperextension of knee and is most common injury, especially in males posterior cruciate ligament (PCL) → anteriorly it is behind the ACL. Prevents posterior sliding of tibia when knee is flexed. Important for walking down stairs Medial/lateral meniscus → semi-circular fibrocartilage attached to tibia and are connected by the transverse ligament of the knee DISORDERS rheumatism and arthritis → any painful disorder of supporting structures in the body not caused by infection or injury. Arthritis is when the joints are stiff swollen and painful osteoarthritis → degenerative joint disease where joint cartilage is lost - combo of age, wear and tear, obesity rheumatoid arthritis → autoimmune disease where body attacks its own cartilage and joint linings - inflammation, swollen - effects both wrists Gouty arthritis → excessive or minimal uric acid excretion causes salt called sodium urate and crystallizes in joint Chapter 10 - 3 types of muscular tissue Skeletal → skeletal muscles move bones → they are striated – alternating bands of light and dark protein bands → they are voluntary muscles cardiac → only found in the heart, forms most of the heart wall → striated, and actions are involuntary due to autorhythmicity → built in pacemaker that controls contractions smooth → found in hollow internal structures like blood vessels, airways → has no striations and is involuntary due to hormonal and neuron control FUNCTIONS OF MUSCULAR TISSUE 1. producing body movements 2. stabalizing body positions 3. storing and moving substances in the body 4. generating heat PROPERTIES OF MUSCULAR TISSUE 1. electrical excitability → ability to respond to stimuli by producing action potentials → received from autorhythmic electrical signals and chemical stimuli 2. contractility → ability of muscle tissue to contract when stimulated by an action potential 3. extensibility → the ability of a muscle to be stretched without being damaged CONNECTIVE TISSUE COMPONENTS - each skeletal muscle is composed of thousands of cells called muscle fibers - fascia is a dense sheet of irregular connective tissue that surrounds muscles, allowing free movement and carries nerves, blood vessels and lymphatic vessels - between the epidermis and the fascia lie the subcutaneous tissue (hypodermis) which seperates muscle from skin → the next layer is called the Epimysium → encircles the entire muscle → next is perimysium → surrounds groups of 10-100 fibers and seperates them into bundles called fascicles → lastly is the endomysium → seperates individual muscle fibers from one another → all three (epi,peri,endo) form tendons that attach muscle to periosteum to bone NERVE AND BLOOD SUPPLY - neurons that stimulate skeletal muscle to contract are somatic motor neurons - capillaries bring in O2 and remove CO2 ANATOMY OF SKELETAL MUSCLE FIBER - diameter of skeletal muscle fiber ranges from 10-100 micrometres - length is 10-30 cm - sarcolemma is the plasma membrane of skeletal muscle cell - sarcolemma is surrounded by small tunnels called transverse tubules which are filled with interstitial fluid and carry muscle action potentials along the muscle fiber → this guarantess that action potentials excite the entire muscle at the same time - the sarcoplasm is in the sarcolemma, which contains glycogen, myoglobin and myofibrils → myoglobin is a protein that binds O2 moluecules and releases them for ATP production → myofibrils are the contractile organelles of skeletal muscle - sarcoplasmic reticulum encircles each myofibril and contains terminal cisterns → SR stores calcium ions and releases them through the terminal cisterns to trigger muscle contraction - within myofibrils are structures called filaments, which are involed in the contractile process and classified as thick filaments or thin filaments - thick filaments → composed of protein myosin - thin filament → double the quantity of thick filaments, composed of protein actin - filaments are arranged in compartments called sarcomeres which are the basic functional units of a myofibril MUSCLE PROTEINS - myofibrils are built from 3 kinds of proteins → contractile protiens → these generate force during contraction → the two contractile proteins are myosin and actin. Myosin binds with actin during contraction → regulatory proteins → proteins that switch muscle contraction processes on and off → tropomyosin and troponin in thin filaments (block myosin-binding sites on actin molecules → structural protein → proteins that keep thick and thin filaments in proper alignment → titin is 3rd most abundant protein in body, connects z disc to M-line SLIDING FILAMENT MECHANISM - thin filaments slide past thick ones and the filaments overlap, causing shortening of the sarcomere, shortening of muscle fibers and shortening of the entire muscle contraction cycle → ATP hydrolysis – myosin heads in thick filaments hydrolyze ATP and become energized → myosin heads bind to actin in thin filaments → myosin cross-bridges rotate toward center of the sarcomere → myosin heads bind to ATP and detaches from actin → cycle continues until full contraction excitation-contraction coupling - Ca2+ is released into sarcoplasm after signalled by a muscle action potential, due to the opening of Ca2+ release channels - calcium combines with troponin, causing it to change shape and move tropomyosin away from the myosin binding sites in actin - once the binding sites are free the myosin heads bind to the actin length-tension relationship → maximal tension during contraction occurs when the sarcomere length is 2-2.4 micrometres - if muscles are stretched too long, myosin heads cant make contact with actin sites, and if the muscle is too short thick filaments crumple and myosin heads cant make contact with thin filaments neuromuscular junction - they are the synapse between a somatic motor neuron and skeletal muscle fiber - synapse – region where communications occur between two neurons-→ seperated by synaptic cleft - somatic motor neurons – neurons that stimulate skeletal muscle to contract - neurotransmitter is a chemical released by a cell to communicate an action potential - synaptic vesicle are membrane enclosed sacs that hold acetylcholine (Ach) - opposite the synaptic vesicle is motor end plate, the muscle fiber part of the neuromuscular junction thsat has Ach receptors