Functions and Characteristics of Skeletal, Smooth, and Cardiac Muscle Tissue, Study Guides, Projects, Research of Nursing

Download Functions and Characteristics of Skeletal, Smooth, and Cardiac Muscle Tissue and more Study Guides, Projects, Research Nursing in PDF only on Docsity! BIOS 252 Midterm Exam Study Guide Ch. 10 Characteristics of smooth and cardiac muscle tissue  Cardiac Muscle o Involuntary, intrinsically controlled, striated, branched, and single nucleated.  Smooth Muscle (Visceral) Involuntary, not striated, not branched, and singly nucleated. Functions of the 3 types of muscle tissue  Skeletal Muscle o Moves bones and other structures  Smooth Muscle o Contractions and relaxation of the autonomic nervous system, and walls of organs  Cardiac Muscle o Pump blood Characteristics of skeletal muscle: excitability, elasticity  Voluntary, striated, not branched, and multinucleated  Excitability: ability to respond to a stimulus, delivered from a motor neuron or a hormone.  Elasticity: ability to return to its original length & shape after contraction or extension. Components of a skeletal muscle cell  Myofibrils: cylindrical structures that extend along the complete length of the cell. Twitch contraction  Brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron. Layers of connective tissue holding skeletal muscle organs together (3 types)  Epimysium: outer layer, dense irregular connective tissue, surrounds muscle organs  Perimysium: middle layer, dense irregular connective tissue, contains nerves and vasculature; surrounds muscle fascicles.  Endomysium: interior layer, loose/elastic connective tissue, contains capillaries, nerves and stem cells, surround muscle fibers. Parts of the sarcomere  Z Discs: narrow, plate-shaped regions of dense material that separate one sarcomere from the next.  A Band: dark, middle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments.  I Band: lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments. A Z-disc passes through center of each I-Band.  H Zone: narrow region in center of each A Band that contains thick filaments but no thin filaments  M Line: region in center of H zone that contains proteins that hold thick filaments together at center of sarcomere. SR function  Store calcium ions (Ca2+) T tubule function  conduct the signal to contract throughout the entire fiber, are part of sarcolemma. Acetylcholine  ACh – neurotransmitter released at the Neuromuscular Junction. Functions in memory, waking up, attention and learning. The sliding mechanism theory  Myosin pulls on actin, causing thin filament to slide inward  Consequently, Z discs move toward each other and the sarcomere shortens  Whole muscle shortens > transfers force to tendon > movement Role of ATP in muscle contraction  ATP binds to myosin, moving myosin to its high-energy state, releasing the myosin head from the actin active site.  ATP can then attach to myosin, which allows the cross-bridge cycle to start again, hence muscle contraction can occur. The steps of muscle contraction (start at NMJ, ending with sarcomere shortening)  Action potential in a motor neuron triggers the release of Ca2+ ions from the sarcoplasmic reticulum  Calcium ions bind to troponin (on actin) and cause tropomyosin to move, exposing binding sites for the myosin heads  The actin filaments and myosin heads form a cross-bridge that is broken by ATP  ATP hydrolysis causes the myosin heads to swivel and change orientation  Swiveled myosin heads bind to the actin filament before returning to their original conformation (releasing ADP + Pi)  The repositioning of the myosin heads move the actin filaments towards the center of the sarcomere  The sliding of actin along myosin therefore shortens the sarcomere, causing muscle contraction Myosin and actin functions  Myosin : thick filament  Actin : thin filament  Interactions of actin and myosin are responsible not only for muscle contraction but also for a variety of movements of non-muscle cells, including cell division  Microglia (CNS) – remove cell debris, wastes, and pathogens by phagocytosis  Ependymal cells (CNS) – line ventricles (brain) and central canal (spinal cord); assist in producing, circulating, and monitoring of cerebrospinal fluid. Chemical and electrical synapses  Chemical synapses – one-way transfer of information from a presynaptic neuron to a postsynaptic neuron  Electrical synapse – gap junctions connect cells and allow the transfer of information to synchronize the activity of a group of cells EPSP vs IPSP  Excitatory postsynaptic potentials – depolarizing postsynaptic potential (opens Na+ channel)  Inhibitory postsynaptic potentials – hyperpolarizing postsynaptic potential (opens K+ or Cl- channel) Excitatory neurotransmitters function and one example  Increase the likelihood that the neuron will fire an action potential  Examples : epinephrine and norepinephrine Inhibitory neurotransmitter function and one example  Decrease the likelihood that the neuron will fire an action potential  Examples : serotonin and gamma-aminobutyric acid (GABA) Ligand-gated channels  transmembrane ion channels that open or close in response to the binding of a chemical messenger like a ligand.  Found in electrically excitable cells like neurons. Voltage-gated channels  Opens in response to a change in membrane potential.  Participate in the generation and conduction of action potentials in the axons of all types of neurons. Electrically excitable cell types  Are used for transmitting signals between different parts of a cell. Signals are generated by opening or closing of ion channels at one point in the membrane, producing a local change in the membrane potential.  Neurons and muscle cells. Depolarization, hyperpolarization, repolarization  Depolarization (less -)  Hyperpolarization (more -)  Repolarization (return to -70) The steps required for a muscle contraction to occur starting with events at the NMJ and ending with the cross-bridge formation cycle  Neuron action potential arrives at end of motor neuron  ACh is released  ACh binds to receptors on motor end plate  Permeability of sarcolemma changes (Na rushes in)(an action potential is produced)  Muscle action potential sweeps into the T Tubules triggering  Release of Ca from the cisternae of the sarcoplasmic reticulum  Ca binds to troponin  Troponin changes shape and shifts tropomyosin to expose binding sites of actin  Myosin binds to actin (cross bridge is formed)(ADP released from myosin)  Myosin head pivots (pulling actin)  Myosin releases from actin (cross bridge is broken)(another ATP binds to myosin)  Myosin re-extends into “ready” position (ATP>ADP+Pi)(ADP is bound to myosin) Ch. 13 Functions of posterior, lateral and anterior horns of gray matter  Posterior: receive sensory information that enters the spinal cord via the dorsal roots of the spinal nerves.  Lateral: present primarily in the thoracic region and contain the preganglionic visceral motor neurons that project to the sympathetic ganglia.  Ventral: contain cell bodies of motor neurons that send axons via the central roots of the spinal nerves to terminate on striated muscle. Tracts in the spinal cord and specific examples  Highways of information up and down spinal cord.  Ex: Spinothalamic: carries sensory info (pain, temp, itch, pressure) from spinal cord to thalamus for processing.  Ex: Lateral Corticospinal: carries info from cerebral cortex to spinal cord, eventually causing voluntary muscle movement through action of motor neurons in spinal nerves Parts of a reflex arc  Sensory receptor: responds to a stimulus by producing a generator or receptor potential  Sensory neuron: axon conducts impulses from receptor to integrating center  Integrating center: one or more regions within CNS that relay impulses from sensory to motor neurons  Motor neuron: axon conducts impulses from integrating center to effector  Effector: muscle or gland that responds to motor impulses Reflex arcs (spinal withdrawal, crossed extensor reflex)  Spinal Withdrawal (flexor reflex) – causes withdrawal of a part of the body in response to a painful stimulus.  Crossed Extensor Reflex – causes contraction of muscles that extend joints in the limb opposite a painful stimulus.  Tendon Reflex – causes relaxation of the muscle attached to the stimulated tendon organ  Stretch Reflex – causes contraction of a muscle that has been stretched. Anatomical organization of the spinal cord  Four regions: cervical, thoracic, lumbar, and sacral  31 pairs of spinal nerves  C1-C8 ; T1-T12 ; L1-L5 ; S1-S5 ; Co1  Cord has three meninges; dura is tough outer sheath, the arachnoid lies beneath it, and the pia closely adheres to the surface of the cord. Lumbar enlargement  Widened area of the spinal cord that gives attachment to the nerves which supply the lower limbs. It commences about the level of T11 and ends at S2, and reaches its maximum circumference, of about 33mm. Nerves that supply the muscles of the thigh/leg  Femoral nerve : anterior portion of the thigh/leg  Sciatic nerve : posterior portion of the thigh/leg  Obturator nerve : medial component of the thigh/leg