Control and Coordination- Nervous system and endocrine system in plants and animals.., Study notes of Biology

Download Control and Coordination- Nervous system and endocrine system in plants and animals.. and more Study notes Biology in PDF only on Docsity! CONTROL and Cc0-ORDINATION ele CL abscisic acid Oca INTRODUCTION % " % " % e % e % e Control and coordination help to maintain a steady state within an organism. The mechanism of maintaining internal steady state is called homeostasis. The vital activities of an organism are controlled by endocrine system and nervous system. In animals both hormones and neurons are involved in regulating and co-coordinating the various vital activities. In plants only chemical co-ordination (via phytohormones) is present. HOMEOSTASIS b. Induced or Paratonic movements(also called Tactic movements): - These movements take place in whole small plants, e.g., Chlamydomonas or small free ciliated organs, e.g., gametes. - These movements occur due to external factors like light, temperature or chemicals and are of the following types : - Chemotactic Movements or Chemotaxism : Many bacteria move towards oxygen. Male gametes of Bryophytes move towards archegonia under the influence of sugars produced by neck canal cells and also in Pteridophyta male gametes move towards archegonia due to the malic acid produced by disintegration of neck canal cells and ventral canal cell. - Phototactic Movements or Phototaxism : Many algae move from darkness to medium light and from high intensity of light to medium light. Movements of chloroplasts of the leaf cells in light and darkness takes place. - Thermotactic Movements or Thermotaxism: Many algae, e.g., Chlamydomonas move from cold water to medium warm water and from very hot water to medium temperature. 2. Movements of Curvature In these movements, organs of plants move in one or the other direction i-e., curvature occurs. These movements are of the following types : Autonomous Movements: These movements are of two types : In Indian Telegraph plant (Desmodium gyrans) a member of Papilionaceae, the leaf has a terminal leaflet and two lateral leaflets. During day time the lateral leaflets move up and down due to variation in turgidity. https://www.youtube.com/watch?v=vN4BIGIb-DQ Movements of Growth: Occur due to unequal growth in different parts of an organ. These are of the following types: Nutation: Apex of a branch or an organ, e.g., tendril becomes spiral due to more growth on the outer side. Hyponasty: When abaxial or morphologically lower surface grows more than the upper surface, resulting in folding of leaves, closing of flowers. Epinasty: When a leaf or petal shows more growth on the adaxial or morphologically upper surface the organ curves downwards. It is this type of curvature that occurs in unfolding of leaves, opening of flowers. Paratonic or Induced Movements: These movements are of the following types: Tropic Movements (Directive Movements) Nastic Movements (Non-directive Movements) Phototropism : Light Geotropism: Gravity Chemotropism: Chemical Hydrotropism: Water Thigmotropism: Touch (e) Chemotropism: When the curvature takes place due to a chemical stimulus, e.g., movement of pollen tube towards ovary or movement of fungal hyphae towards sugars and peptones. (f) Thermotropism: Curvature of plant towards normal temperatures from very high or very low temperatures. Thermotropic responses to cold temperatures may be seen in the shoots of many common weeds. (B) Nastic Movements - Such movements are due to stimulus of light, temperature or contact, but the direction of response is prefixed (not determined by the direction of stimuli and inherent in the tissues). Nastic movements are of the following types: (a) Seismonastic Movements : Eg. Mimosa Pudicaa. If the flowerpot is moved or leaf or any other organ of the plant is touched, the stimulus reaches the base of the leaf. Owing to this stimulus, the turgor of lower half of pulvinus is lost and the leaf droops. After sometime the cells of the lower half of pulvinus become turgid again and the leaf attains its erect position. (b) Nyctinastic (Sleeping) Movements: The diurnal (changes in day and night) movements of leaves and flowers of some species which take up sleeping position at night are called nyctinastic movements. Nastic movements Leaflet folded Decrease of ——, turgor in parenchyma cols calls retaining turgor Cross-sectional views % od % od % od aRWN = Plant Hormones Chemical substances produced by plants naturally, which are capable of regulating one or more physiological processes when present in low concentration. Some hormones stimulate plant growth while other act as growth inhibitors, therefore plant hormones are also called as growth hormones. There are five major types of plant hormones. Auxins Cytokinins Gibberellins Ethylene Abscisic acid % “ Inhibition Of Abscission Formation of an abscission layer at the base of petiole of pedicel results in shedding of leaves, flowers or fruits. But auxins inhibits abscission, as they prevent the formation of abscission layer. Parthenocarpy Formation of fruit without pollination and may be fertilization is done with the help of hormones. This results in the formation of seedless fruits. Auxins play an important role in the development of seedless fruits Light B , Auxin i. Auxin spreads equally down both sides of the plant Auxin collects on the shady side Cytokinins (CK) Class of plant growth substances (plant hormones) that promote cell division. They are primarily involved in cell growth, differentiation, and other physiological processes. Cytokinin concentration is highest in meristematic regions and areas of continuous growth potential such as roots, young leaves, developing fruits and seeds. Helps in breaking the dormancy of seeds and buds, and regulates the phloem transport. Delays ageing of leaves and promotes the opening of stomata. Ethylene Mainly produced in the cells of higher plants, it’s a gaseous hormone. It induces ripening of fruits. Ethylene stimulates abscission of various plant parts. % od Gibberellins (GA) Gibberellins (GAs) are plant hormones that regulate growth and influence various developmental processes including stem elongation, germination, dormancy, flowering, sex expression, enzyme induction and leaf and fruit senescence. Stimulate stem elongation by stimulating cell division and elongation. Stimulates bolting/flowering in response to long days. Breaks seed’s dormancy in some plants which requires light to induce germination. Induces maleness in dioecious flowers (sex expression). Can cause parthenocarpic (seedless) fruit development. Can delay senescence in leaves and citrus fruits. Abscisic Acid (ABA) Growth inhibitor which reverses the growth promoting effects of auxins and gibberellins. Causes dormancy of seeds, tubers and bulbs. Promotes falling of leaves and ripening of fruit ¢ Divisions of Nervous System: (i) Central Nervous System: It lies along the main (longitudinal) axis of the body. Consists of the brain and the spinal cord. The brain is covered by cranium & spinal cord is covered by vertebral column, both are also surrounded by three membrane of the connective tissues called meninges. (ii) Peripheral Nervous System: It consists of nerves, which extends between the central nervous system and the sense organs or body’s effectors (muscles, glands, etc.) or both. It enables to control the voluntary activities of the body. It includes cranial nerves (that arise from or join the brain) and spinal nerves(that arise from spinal cord). There are 12 pairs of cranial nerves and 31 pairs of spinal nerves in humans. (iii) Autonomic Nervous System: It consists of nerves which connect the visceral receptors and effectors with the CNS through the cranial and spinal nerves. It controls involuntary activities of internal organs such as heart, blood vessels, glands and smooth muscles of alimentary canal and uterus. It is subdivided into: (A) Sympathetic nervous system (B) Parasympathetic nervous system Most of the organs receive nerves from both sympathetic and parasympathetic nerve fibres. They have opposite effects on the organs; if one is stimulatory, the other is inhibitory. HUMAN NERVOUS SYSTEM e o ce Ss e © Structure of Neuron: Each neuron consists of a cell body called cyton and a number of branches arising from the cyton. Neuron does not divide. Cyton contains a nucleus within the cytoplasm and Nissl’s granules (formed of RER) and fine thread like fibres, called neurofibrils. Dendrites: These are short, several, much branched & contain granules. They carry impulses towards the cyton. Axon: It is a large, single structure. It has no Nissl’s granules. It carries impulses from cyton to the effector organs like glands, muscles etc. Synapse is a very fine gap between two neurons. Types of Neurons or Nerve Fibres: Motor: It carries impulses from brain and spinal cord to effector organs. Sensory: These transmit impulse from sensory receptors to central nervous system. Mixed nerves: These carry both sensory and motor fibres. Eg. a spinal nerve Synapse: Synapse is a point of contact between the terminal branches of the axon of a neuron with the dendrites of another neuron separated by a fine gap. The impulse reaches the terminal end of an axon; here, a chemical ‘acetylcholine’ is released. This chemical sets a new impulse in the dendrites of the adjacent neuron. Thus, a microscopic gap between a pair of adjacent neurons over which nerve impulses pass when going from one neuron to the next is called synapse. They actually act like one-way valves. https://www.youtube.com/watch?v=OvVI8rOEncE Structure of Brain: Brain is covered by 3 membranes called meninges. Outer Membrane = Duramater > Tough, collagenous fibrous layer, inserted in periosteum of cranium. Middle Membrane = Archnoid layer > Comparatively soft but non-vascularized, also called ‘spider web’. Inner Membrane = Piamater > Highly vascularized, most soft of all. The space between the membranes is filled with a fluid called cerebrospinal fluid that protects the brain from mechanical shocks. cerebellum The Human Nervous System Peripheral Nervous System(P.N.S.) EI Autonomic Somatic N.S N.S _¥ — Vv Sympathetic N.S. Fore Brain Mid Brain Hind Brain Cerebrum Optic Lobes Parasympathetic N S Garebral Cerebellum Cortex Pons Olfactory Lobes Medulla Diencephalon Oblongata A midsagittal view showing the inner boundaries of the lobes of the cerebral cortex (Structures outside of the cerebrum are labeled in italics.) Precentral gyrus Central sulcus Postcentral gyrus Limbic lobe Parietal lobe 'Z Parieto-occipital sulcus ¢ Occipital lobe Thalamus ] Hypothalamus Optic chiasm Frontal lobe Corpus callosum Corpora quadrigemina Aqueduct of the midbrain Fourth ventricle Temporal lobe Cerebellum Mamillary body Medulla oblongata © 2011 Pearson Education, inc. % e Spinal Cord: It lies in the vertebral column. Starts from medulla oblongata and extends downward. Protected by three meninges and cerebrospinal fluid. It also acts as a centre for spinal reflexes. Reflex Action : It is a rapid, automatic response to a stimulus by an organ or a system of organs, which does not consult the will of brain for its initiation. A reflex action is an unconscious (without will) and involuntary response to effectors (muscles or glands) to a stimulus. Mammals show a wide range of reflexes which can be broadly classified into two types : unconditioned and conditioned reflexes. SPINAL CORD Spinal reflex \ _ Afferent sensory : information \ - . Eas Spinal Dorsal zone ganglion nferen, root Posterior Grey matter median fissure Grey matter White matter Spinal Interneuron A nerve Spinal > nerve g Anterior median fissure 4/\ Ventral root Bjere* Difference between the conditioned and unconditioned reflexes U litioned Conditioned . Inborn, inherited reactions 4, Acquired as a result of . Species-specific . Stable . Has definite receptive field . Can be without brain.cort. . Most of them for all life “life experience” 2. Individual 3. Unstable 4. Different receptive field 5. Need brain cortex 6. Temporary, can disappear (extinguish) 7. Are built on the basis of unconditioned reflex “* Electroencephalogram (EEG): The activity of brain is recorded as electrical potentials, such a record is called Electroencephalogram(EEG). Electroencephalogram (EEG)