Chapter-21
Neural Control and Coordination
- Points to Remember
- Coordination : Process through which two or more organs interact and complement the functions of one another surroundings the brain.
- Action potential : A sudden change in the electrial charges in the plasma membrane of a nerve fibre.
- Aqueous humour : The thin watery fluid that occupy space between lens and cornea in eye.
- Blind spot : A spot or retina which is free from rods and cones and lack the abililty for vision.
- Cerebrospinal fluid : An alkaline fluid present in between inner two layer of meninges, surroundings the brain and spinal cord.
- Cochlea : A spirally coiled part of internal ear which is responsible for hearing.
- Corpus callosum : A curved thick bundle of nerve fibres that joins tow cerebal hemisphere.
- Endolymph : The fluid filled within membranous labyrinth.
- Eustachian Tube : A tube which connect ear cavity with the pharynx.
- Fova : An area of highest vision on the retina which contain only cones.
- Meninges : Three sheets of covering of connective tissue wrapping the brain.
- Grey Matter : This shows may convolutions which increase the amount of vital nerve tissue.
- Medula oblongata : Posterior most part of the brain which is continous with spinal cord and control respiration, heart rate, swallowing, vomiting.
- Pons : Thick bundles of fibres on the ventral side of brain below cerebellum.
- Foramen magnum : A big aperture in the skull posteriorly through which spinal cord emerges out.
- Spinal cord : A tubular structure connected with medulla oblongata of brain and situated in the neural canal of the vertebral column covered by meninges.
- Synaptic cleft : A narrow fluid filled space which separates two membranes of the two neurons at the synapse.
- Synaptic Vesicles : These are membrane bound vesicles in the axoplasm of the axon terminal and these store neurotransmitter.
- Neurotransmitter : These are chemicals stored in synaptic vesicles, diffuse to reach the membrane of next neuron for its stimulation.
- Synapse : A physiological juction between axon of one neuron and dendrite of next neuron.
- CNS - Central Neural System
- PNS - Perispheral Neural System
- ANS - Automic Neural System
- Visceral Nervous System : Whole complex of nerves, fibres, ganglia and plexuses by which impulses travel form CNS to the viscera and form viscera to CNS.
Conduction of Nerve Impulse :
- Polarization : Resting Potential
- Before stimulation axoplasm contain -vely high concentration of K+ and low concentration of Na+ Inner surface is -vely charged.
- Fluid outside axon - low concentration of K+ and high concentration of Na+. Outside the membrane is +vely charged.
- Most membrane channels are closed.
- Depolarization : Action Potential
- Stimulation of merve.
- Permeability of membrane to Na+ increase.
- Na+ channels opens allowing Na+ to diffuse into the cell quickly.
- As a result inside become +ve and outside -ve.
- Repolarization : Normalising
- K+ gates open in order to allow k+ to diffuse out of the axon. This restores teh membrane. (+ve outside -ve inside)
Transmission of Impulses at Synapse :
- (i) At Elecrical Synapses : Here the membrane of pre and post-syneptic neuron are in very close proximity. Electric current can flow directly from one neuron into other across these synapses, like impule conduction along a single axon.
- (ii) At Chemical Synapses : Here the membrane of pre and post-syneptic neuron are separated by fluid space called synaptic cleft. Neurotransmitter are involved here.
- When an impulse arrives at the axon terminal, it stimulates teh movement of the synaptic vesicles towards membrane and they fuse with the plsama membrane and release their neurotransmitter in the syneptic cleft. The chemicals bind to specific receptors, present on the post-syneptic membrane. Their binding opens ion channels and allow the entry of ion which generate new potential in post synaptic neuron.
- Human Brain : Human brain is the major portion of central neural system. Which is well protected by the skull.
- The brain is surrounded by three canial meninges--
- (i) Duramater -- Outer layer
- (ii) Arachnoid -- Middle layer
- (iii) Piameter -- Inner layer-remain incontact with brain
Functions of Parts of Brain :
- Cerebrum : Centre of intelligence, memory and imagination, reasoning, judgementm expression of will power.
- Thalamus : Acts as relay centre to receive and transmit general sensation of pain, touch and temperature.
- Hypothalamus : Centre for regulation of body temperature, urge for eating and drinking.
- Midbrain : Responsible to coordinate visual reflexes and auditory reflexes.
- Cerebellum : Maintains posture and equilibrium of the body as well as coordinate and regulates voluntary movement.
- Pons : Relays impulses between medualla oblongata and cerebral hemisphere and between the hemisphere of cerebrum and cerebellum. It also helps to regulate breathing.
- Medulla oblongata : Centre that control heart beat, breathing, swallowing, salivation, sneezing, vomitting and coughing.
- Reflex action :It is spontaneous, autonomic and mechanical response to a stimulus that occurs at the level of spinal cord, without involvement of brain.
- Reflex are : The flow of nerve along the specific during reflex action, It consist of:-
- (a) A receptor
- (b) An Afferent neuron (sensory neuron)
- (c) An inter neuron
- (d) An efferent neuron (motor neuron)
- (e) An effector organ.
Organ of Eye-Sight
Organ of Hearing-Ear :
Organ to smell -- Nose (Factor Organ) :
