These notes for CBSE Class 11 Biology, Chapter 21, focus on Neural Control and Coordination. They define key terms like action potential, synapse, neurotransmitters, and describe the structure and function of the central and peripheral nervous systems. The notes explain the resting potential and action potential in neurons, detailing the ionic changes across the axonal membrane during impulse conduction. They also differentiate between electrical and chemical synapses, explaining neurotransmitter release and binding. Furthermore, the functions of various brain parts, including the cerebrum, thalamus, hypothalamus, midbrain, cerebellum, pons, and medulla oblongata, are outlined. These notes provide a comprehensive overview for students to revise the concepts of neural control and coordination for their exams.
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Action potential : A sudden change in the electrical 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 on ratina which is free from rods and cones and lack the ability for
vision.
Cerebrospinal fluid : An alkaline fluid present in between inner two layer of meninges.
Cerebellum : A part of hind brain that controls the balance and posture of the body.
Cochlea : A spirally coiled part of internal ear which is responsible for hearing.
Corpus callosum : A curved thick bundle of nerve fibres that joins two cerebral
hemisphere.
Depolarisation : A condition when polarity of the plasma membrane of nerve fibre is
reversed.
Endolymph : The fluid filled within membranous labyrinth.
Ecustachian tube : A tube which connect ear cavity with the pharynx.
Fovea : A area of highest vision on the ratina which contain only cones.
Meninges : Three sheets of covering of connective tissue wrapping the brain.
Grey Matter : This shows many convolutions which increase the amount of vital
nerve tissue.
Medula oblongata : Posterior most part of the brain which is continuous 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 junction between axon of one neuron and dendrite of next
neuron.
CNS ? Central neural system
PNS ? Peripheral neural system
ANS ? Autonomic neural system
Conduction of nerve impulse along axon
Polarised membrane/Resting Potential
In resting phase when neuron is not conducting an impulse, the axonal membrane
is called polarised. This is due to difference in concentration of ions across the axonal
membrane.
• Axoplasm inside the axon contain high conc. of K
and low
conc. of Na . • The fluid outside the axon contain low conc. of K + and high
conc. of Na . As a result the outer surface of axonal membrane is positively charged and inner + surface is negatively charged. The electric potential difference across the resting plasma
membrane is called resting potential.
Action Potential : When a nerve fibre is stimulated, the permeability of membrane
to Na + is greatly increased at the point of stimulus (rapid influx of Na
) and
hence polarity of membrane is reversed and now membrane is said to be depolarised.
The electric potential difference across the plasma membrane at that site is called
action potential, which infact termed as nerve impulse. Depolarisation is very rapid, so that conduction of nerve impulse along the entire
length of axon occurs in fractions of second.
(i) At electrical 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 impulse conduction along a single axon.
(ii) At chemical synapses : Here the membrane of pre and post-syneptic
neuron are separated by fluid filled space called synaptic cleft. Neurotransmitter are
involved here.
When an impulse arrives at the axon terminal, it stimulates the movement of the
synaptic vesicles towards membrane and they fuse with the plasma membrane and
release their neurotransmitter in the syneptic cleft.
These 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.
Cerebrum : Centre of intelligence, memory and imagination, reasoning,
judgement, 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.
Mid brain : Responsible to coordinate visual reflexes and auditory reflexes.
Cerebellum : Maintains posture and equilibrium of the body as well as
coordinates and regulates voluntary movement.
Pons varoli : Relays impulses between medulla oblongata and cerebral hemisphere
and between the hemisphere of cerebrum and cerebellum.
Medulla oblongata : Centre that control heart beat, breathing, swallowing,
salivation, sneezing, vomiting and coughing.
Neural Control and Coordination in Class 11 Biology deals with how the nervous system controls and coordinates bodily functions, including nerve impulse transmission and the roles of different brain parts.
An action potential is a sudden change in the electrical charges across the plasma membrane of a nerve fibre when it is stimulated, leading to the transmission of a nerve impulse.
Electrical synapses allow direct flow of current between neurons, while chemical synapses involve the release of neurotransmitters across a synaptic cleft to transmit the impulse.
The medulla oblongata controls vital functions such as heart rate, breathing, swallowing, salivation, sneezing, vomiting, and coughing.
The cerebellum maintains the body's posture and equilibrium, and coordinates and regulates voluntary movements.
A neurotransmitter is a chemical stored in synaptic vesicles that diffuses across the synaptic cleft to stimulate the next neuron.
The resting potential is the electric potential difference across the plasma membrane of a neuron when it is not conducting an impulse, with the outer surface positively charged and the inner surface negatively charged.
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