Neural Control & Coordination Class 11 Notes Biology Chapter 21

 Page 1


Points To Remember
Coordination : Process through which two or more organs interact and 
complement the functions of one another surrounding the brain.
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, surrounding the brain and spinal cord.
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 : An 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.
Page 2


Points To Remember
Coordination : Process through which two or more organs interact and 
complement the functions of one another surrounding the brain.
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, surrounding the brain and spinal cord.
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 : An 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 o n 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
Neural System
       Central neural System Peripheral neural System
   Brain               Spinal cord Cranial nerve Spinal nerve
12 pairs 31 pairs
Nerve fibres of PNS
Afferent fibres Tansmit impulse Efferent fibres Transmit impulse
  from Tissue/organ to CNS from CNS to Peripherel tissue/organ
Division of PNS
    Somatic neural System Automatic neural system Transmit
 Relays impulse from CNS impulse from CNS to involuntary
     to Skeletal muscle Organ and smooth muslces
Page 3


Points To Remember
Coordination : Process through which two or more organs interact and 
complement the functions of one another surrounding the brain.
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, surrounding the brain and spinal cord.
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 : An 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 o n 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
Neural System
       Central neural System Peripheral neural System
   Brain               Spinal cord Cranial nerve Spinal nerve
12 pairs 31 pairs
Nerve fibres of PNS
Afferent fibres Tansmit impulse Efferent fibres Transmit impulse
  from Tissue/organ to CNS from CNS to Peripherel tissue/organ
Division of PNS
    Somatic neural System Automatic neural system Transmit
 Relays impulse from CNS impulse from CNS to involuntary
     to Skeletal muscle Organ and smooth muslces
Cell body =  Cytoplasm with nucleus, cell organelles and
Nissl’s granules
Parts of Neuron    Dendrites = Short fibres which branch rapidly and project
out of cell
 Axon =      Single, long fibre, branched at distal endit
(Refer fig. 21.1, page 317, NCERT - Biology, Class-XI)
Multipolar = : One axon and two or more dentrites
 : Found in cerebral Cortex
Neuron             Bipolar =   : One axon and one dendrite
 : Found in ratina of eye
Unipolar = : Cell body with axon only
: Found usually in the embryonic stage
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.
At Rest :
? 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.
Page 4


Points To Remember
Coordination : Process through which two or more organs interact and 
complement the functions of one another surrounding the brain.
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, surrounding the brain and spinal cord.
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 : An 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 o n 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
Neural System
       Central neural System Peripheral neural System
   Brain               Spinal cord Cranial nerve Spinal nerve
12 pairs 31 pairs
Nerve fibres of PNS
Afferent fibres Tansmit impulse Efferent fibres Transmit impulse
  from Tissue/organ to CNS from CNS to Peripherel tissue/organ
Division of PNS
    Somatic neural System Automatic neural system Transmit
 Relays impulse from CNS impulse from CNS to involuntary
     to Skeletal muscle Organ and smooth muslces
Cell body =  Cytoplasm with nucleus, cell organelles and
Nissl’s granules
Parts of Neuron    Dendrites = Short fibres which branch rapidly and project
out of cell
 Axon =      Single, long fibre, branched at distal endit
(Refer fig. 21.1, page 317, NCERT - Biology, Class-XI)
Multipolar = : One axon and two or more dentrites
 : Found in cerebral Cortex
Neuron             Bipolar =   : One axon and one dendrite
 : Found in ratina of eye
Unipolar = : Cell body with axon only
: Found usually in the embryonic stage
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.
At Rest :
? 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.
207
Transmission of Impulses at Synapse
(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 impule 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 plsama 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.
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 cranial meninges—
(i) Duramater—outer alyer
(ii) Arachnoid—middle layer
(iii) Piamter—Inner layer-remain incontact with brain
Parts of Brain
Fore brain Mid brain Hind brain
(a) Cerebrum (a) Cerebellum
(b) Thalamus (b) Pons
(c) Hypothalamus (c) Medulla oblongata
Functions of pars of brain :
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.
Midbrain : Responsible to coordinate visual reflexes and auditory reflexes.
Cerebellum : Maintains posture and equilibrium of the body as well as 
coordinates and regulates voluntary movement.
Page 5


Points To Remember
Coordination : Process through which two or more organs interact and 
complement the functions of one another surrounding the brain.
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, surrounding the brain and spinal cord.
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 : An 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 o n 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
Neural System
       Central neural System Peripheral neural System
   Brain               Spinal cord Cranial nerve Spinal nerve
12 pairs 31 pairs
Nerve fibres of PNS
Afferent fibres Tansmit impulse Efferent fibres Transmit impulse
  from Tissue/organ to CNS from CNS to Peripherel tissue/organ
Division of PNS
    Somatic neural System Automatic neural system Transmit
 Relays impulse from CNS impulse from CNS to involuntary
     to Skeletal muscle Organ and smooth muslces
Cell body =  Cytoplasm with nucleus, cell organelles and
Nissl’s granules
Parts of Neuron    Dendrites = Short fibres which branch rapidly and project
out of cell
 Axon =      Single, long fibre, branched at distal endit
(Refer fig. 21.1, page 317, NCERT - Biology, Class-XI)
Multipolar = : One axon and two or more dentrites
 : Found in cerebral Cortex
Neuron             Bipolar =   : One axon and one dendrite
 : Found in ratina of eye
Unipolar = : Cell body with axon only
: Found usually in the embryonic stage
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.
At Rest :
? 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.
207
Transmission of Impulses at Synapse
(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 impule 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 plsama 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.
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 cranial meninges—
(i) Duramater—outer alyer
(ii) Arachnoid—middle layer
(iii) Piamter—Inner layer-remain incontact with brain
Parts of Brain
Fore brain Mid brain Hind brain
(a) Cerebrum (a) Cerebellum
(b) Thalamus (b) Pons
(c) Hypothalamus (c) Medulla oblongata
Functions of pars of brain :
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.
Midbrain : Responsible to coordinate visual reflexes and auditory reflexes.
Cerebellum : Maintains posture and equilibrium of the body as well as 
coordinates and regulates voluntary movement.
208
Pons : Relays impulses between medulla oblongata and cerebral hemisphere 
and between the hemisphere of cerebrum and cerebellum. It also heps 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 arc : 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
Sensory neuron
Stimulus Receptor
(REFLEX - ARC)                                                Inter neuron of spinal cord
Response Effector organ
motor neuron
Organ of Sight-Eye
Layer Component Function
1.External layerSclera Protects and maintain shape of the
eye ball
Cornea Outermost transparent portion of 
eye which allows light to enter
2. Middle layer Choroid Absorb light and prevent light from
being reflected within the eye ball.
Ciliary body Holds lens, regulate shape of the  
lens.
Iris Control amount of light entering.
3. Inner layer Retina Vision in dim light, colour vision,
vision in bright light. Sends the 
image to brain through optical  
nerves.
(Refer-Fig. 21.6, Page 323 NCERT-Biology, Class XI)