NCERT Solutions for Class 11 Biology Chapter 21 : Neural Control and Coordination
NCERT Solutions for Class 11 Biology Chapter 21 Neural Control and Coordination will help you to ace the unsolved problems in the Class 11 Science book prescribed by the NCERT for all the schools of CBSE. It presents the best alternative and a very interesting way to learn, which helps to enhance your abilities and help to get ready for CBSE Class 11 exams.
Biology Chapter 21 Neural Control and Coordination Class 11 Notes are prepared by our expert faculties to help you to prepare for your exams in a better way and enhance your score. These NCERT Solutions provide step by step solutions for the questions given in NCERT textbook as per CBSE Board guidelines and are also prepared according to the exam pattern. In case of doubts, we have a team of teachers who prove live doubt solving session only for you.
In NCERT Solutions for Class 11 Biology Chapter 21, you will understand about the neural system of human, mechanisms of neural coordination like transmission of nerve impulse, impulse conduction across a synapse and the physiology of reflex action, neural system, human neural system, neuron as structural and functional unit of neural system, central neural system, reflex action and reflex arc and sensory reception and processing.
Access NCERT Solutions for Class 11 Biology Chapter 21 : Neural Control and Coordination
Exercise Questions Page Number – 329
Briefly describe the structure of brain.
Brain is the main coordinating centre of the body. It is well protected by the skull. It is externally surrounded by three layers, together known as meninges. The tough outer layer is dura mater, a very thin middle layer is arachnoid and smooth inner layer is called pia mater. The brain is divided into three major parts: forebrain, midbrain and hindbrain.
Forebrain: It consists of cerebrum, thalamus, and hypothalamus.
(i) Cerebrum is the largest part of the brain and is divided into two cerebral hemispheres by cerebral fissure. It has four lobes/ functional areas- frontal, lateral, parietal and temporal.
(ii) Thalamus is the main centre of coordination for sensory and motor signalling.
(iii) Hypothalamus lies at the base of thalamus. It secretes ADH and oxytocin. It is the centre for thirst, hunger, love, affection.
Midbrain: It is located between the thalamus region of the forebrain and pons
Region of hindbrain. It consists of two parts- optic lobes and cerebral peduncle. It is concerned with the sense of sight and hearing.
Hindbrain: It consists of three regions- cerebellum, pons and medulla oblongata.
(i) Cerebellum is the second largest part of the brain. It is responsible for maintaining posture and equilibrium of the body.
(ii) Pons is a band of nerve fibre that lies between medulla oblongata and midbrain. It connects the lateral parts of cerebellar hemisphere together.
(iii) Medulla oblongata is the posterior part of the brain. It is located beneath the cerebellum and extends to form the spinal cord.
Compare the following.
(a) Central neural system (CNS) and Peripheral neural system (PNS)
(b) Resting potential and action potential
(c) Choroid and retina
|Central neural system || Peripheral neural system |
| 1. It is the main coordinating centre of the body.|| 1. It is not the main coordinating centre of the body.|
| 2. It includes brain and spinal cord.|| 2. It includes cranial and spinal nerves that connect central nervous system to different parts of the body.|
| Resting potential|| Action potential|
| 1. It is the potential difference across the nerve fibre when there is no conduction of nerve impulse.|| 1. It is the potential difference across nerve fibre when there is conduction of nerve impulse.|
| 2.The membrane is more permeable to K+ ions than to Na+ ions.|| 2. The membrane is more permeable to Na+ ions than to K+ ions.|
| Choroid|| Retina|
| 1. Choroid is the middle vascular layer of eye.|| 1. Retina is the innermost nervous coat of eye.|
| 2. It contains numerous blood vessels that provide nutrients and oxygen to retina and other tissues.|| 2. It contains photoreceptor cells, rods and cones that are associated with twilight and colour vision respectively.|
Explain the following processes:
(a) Polarisation of the membrane of a nerve fibre
(b) Depolarisation of the membrane of a nerve fibre
(c) Conduction of a nerve impulse along a nerve fibre
(d) Transmission of a nerve impulse across a chemical synapse
During resting condition, the concentration of K+ ions is more inside the axoplasm while the concentration of Na+ ions is more outside the axoplasm. As a result, the potassium ions move faster from inside to outside as compared to sodium ions. Therefore, the membrane becomes positively charged outside and negatively charged inside. This is known as the polarization of membrane or polarized nerve.
When an electrical stimulus is received by a nerve fibre, an action potential is generated. The membrane becomes permeable to sodium ions than to potassium ions. This results in a positive charge inside and negative charge outside the nerve fibre. Hence, the membrane is said to be depolarised. The potential generated at this phase is known as the action potential. As the action potential reaches its maximum value, the membrane potential gets reversed and this state is known as repolarization.
Synapse is a small gap that occurs between the last portion of the axon of one neuron and the dendrite of next neuron. When an impulse reaches at the end plate of the axon, vesicles consisting of a chemical substance or neurotransmitter, such as acetylcholine, fuse with the plasma membrane. This chemical moves across the cleft and attaches to chemo-receptors present on the membrane of the dendrite of next neuron. This binding of chemical with chemo-receptors leads to the depolarization of membrane and generates a nerve impulse across nerve fibre.
Write short notes on the following:
(a) Neural coordination
(f) Ear ossicles
(h) Organ of Corti
(a) Neural coordination: The nervous system provides quick coordination of various parts of the body through electric impulses. These impulses are short lived but quick.
(b) Forebrain consists of the cerebrum, cerebral hemispheres, olfactory lobes and diencephalon (thalamus and hypothalamus). It helps in the interpretation of stimulus received by effector organs.
(c) Midbrain consists of tectum (visual and auditory stimuli) and tegmentum (contains nuclei for pain modulation, motor coordination and movement planning). It helps in the relay of impulse from effector organ to the forebrain.
(d) Pons, cerebellum and medulla together form the hindbrain. It helps to maintain the balance of body and body posture. It also has regulatory centres for controlling the involuntary actions.
(e) The retina is the innermost layer of the eyeball and contains photoreceptor rods and cones.
(f) Ear ossicles: Three small bones present between the tympanic membrane and oval window are collectively referred to as ossicles, they are namely malleus, incus and stapes. It increases the amplification of sound waves.
(g) Cochlea: Cochlea is a spiral hollow structure containing three fluid-filled canals. Organ of corti is located in middle cochlear canal and has hair cells (mechanoreceptors) on its basilar membrane. Thus, cochlea houses sensory system for hearing only and is not associated with balancing.
(h) Organ of corti: Organ of corti is located in middle cochlear canal and has hair cells (mechanoreceptors) on its basilar membrane. It generates the auditory impulse which is carried by auditory nerves.
(i) Synapse: Two neurons are never physically connected to each other and synapse is the region of close proximity between two neurons where information from one neuron is transmitted to the next one.
Give a brief account on:
(a) Mechanism of synaptic transmission
(b) Mechanism of vision
(c) Mechanism of hearing
(a) Synapse is a junction between two neurons. It is present between the axon terminal of one neuron and the dendrite of next neuron separated by a cleft.
There are two ways of synaptic transmission.
(1) Chemical transmission
(2) Electrical transmission
1. Chemical transmission: When a nerve impulse reaches the end plate of the axon, it releases a neurotransmitter (acetylcholine) across the synaptic cleft. This chemical is synthesized in the cell body of the neuron and is transported to the axon terminal. The acetylcholine diffuses across the cleft and binds to the receptors present on the membrane of next neuron. This causes depolarization of membrane and initiates an action potential.
2. Electrical transmission: In this type of transmission, an electric current is formed in the neuron. This electric current generates an action potential and leads to transmission of a nerve impulse across the nerve fibre. This represents a faster method of nerve conduction than the chemical method of transmission.
(b) Mechanism of vision
Retina is the innermost layer of the eye. It contains three layers of cells – inner ganglion cells, middle bipolar cells, and outermost photoreceptor cells. A photoreceptor cell is composed of a protein called as opsin and an aldehyde of vitamin A called as retinal. When light rays are focused on the retina through the cornea, it leads to the dissociation of retinal from opsin protein. This changes the structure of opsin. As the structure of opsin changes, the permeability of membrane changes, generating a potential difference in the cells. This generates an action potential in the ganglionic cells and is transmitted to the visual cortex of the brain via optic nerves. In the cortex region of the brain, the impulses are analysed and the image is formed on the retina.
(c) Mechanism of hearing
The pinna of the external region collects the sound waves and directs it towards ear drum or external auditory canal. These waves strike the tympanic membrane and vibrations are created. Then, these vibrations are transmitted to the oval window, fenestra ovalis, through three ear ossicles, named as malleus, incus, and stapes. These ear ossicles act as a lever and transmit the sound waves to internal ear. These vibrations from fenestra ovalis are transmitted into the cochlear fluid. This generates sound waves in the lymph. The formation of waves generates a ripple in the basilar membrane. This movement bends the sensory hair cells present on the organ of Corti against tectorial membrane. As a result of this, sound waves are converted into nerve impulses. These impulses are then carried to the auditory cortex of brain via auditory nerves. In cerebral cortex of the brain, the impulses are analysed and the sound is recognized.
(a) How do you perceive the colour of an object?
(b) Which part of our body helps us in maintaining the body balance?
(c) How does the eye regulate the amount of light that falls on the retina?
a) Photoreceptors are cells that are sensitive to light. They are of two types – rods and cones. These are present in the retina. Cones help in distinguishing colours. There are three types of cone cells – those responding to green light, those responding to blue light, and those responding to red light. These cells are stimulated by different lights, from different sources. The combinations of the signals generated help us see the different colours.
b) The inner ear is part of an ear is responsible for maintaining the body balance. The vestibular apparatus and the semicircular canal is responsible for maintaining the balance of the body.
c) A pupil is like an aperture in an eye. It dilates in low light and constricts in intense light when the light falls on the retina.
Explain the following.
(a) Role of Na+ in the generation of action potential.
(b) Mechanism of generation of light-induced impulse in the retina.
(c) The mechanism through which a sound produces a nerve impulse in the inner ear.
Sodium ions play an important role in the generation of action potential. When a nerve fiber is stimulated, the membrane potential decreases. The membrane becomes more permeable to Na+ ions than to K+ ions. As a result, Na+ diffuses from the outside to the inside of the membrane. This causes the inside of the membrane to become positively charged, while the outer membrane gains a negative charge. This reversal of polarity across the membrane is known as depolarization. The rapid inflow of Na+ ions causes the membrane potential to increase, thereby generating an action potential.
b) In the eye, retina have photopigments like retinal and opsin. Light dissociates the retinal from opsin which changes the structure of opsin and generates an action potential.
c) When sound falls over the eardrum, it is then transmitted to the inner ear by ear ossicles. The vibrations are passed through the oval window onto the fluid of the cochlea, where they generate waves in the lymph. These waves induce the hair cell. As a result nerve impulses are generated in the associated afferent neurons and transmitted to the auditory cortex of the brain via auditory nerves.
(a) Myelinated and non-myelinated axons
(b) Dendrites and axons
(c) Rods and cones
(d) Thalamus and hypothalamus
(e) Cerebrum and cerebellum
(a) A myelinated neuron is a neuron whose axon is covered by the myelin sheath (myelin means white). The conduction of nerve impulse is faster in this neuron than non-myelinated neuron due to the presence of myelin sheath over the axon. Myelin sheath avoids the loss of impulse during conduction.
Whereas non-myelinated neuron is the neuron whose axon is not covered by the myelin sheath. The conduction of nerve impulse in this neuron is slow than myelinated neuron due to the absence of myelin sheath. There are more chances of loss of impulse during conduction.
(b) Axon is a single long, thick neurite structure in the neuron. It contains neurofibrils. It is the efferent component of the impulse. Whereas dendrites are multiple short and thick neurites in the neuron. It is the branched structure which contains both neurofibrils and Nissl's granules. It is the afferent components of the neurons.
(c) Rods are the photoreceptor cells of the retina that are sensitive to dim light. They have the visual purple pigment called as rhodopsin.
Whereas cones are the photoreceptor cells of the retina that are sensitive to bright light. They have the visual violet pigment called as iodopsin.
(d) Thalamus and hypothalamus are both names of structures in the brain. While the hypothalamus is cone-shaped, the thalamus consists of two connected lobes, one located in each hemisphere. The hypothalamus regulates the body's vital metabolic processes, affecting temperature, blood pressure, hunger, thirst and sleep. It controls the endocrine system by affecting the pituitary gland's production of hormones. The thalamus takes information from a number of different areas of the brain and relays it to the cerebral cortex, the outer layer of gray matter where higher level brain functions take place.
(e) The cerebrum is the part of the forebrain that controls voluntary functions. It is the place where intelligence, will power, memory, etc., reside. It is the largest part of the brain, forming four fifths of its weight. Whereas cerebellum is the part of the hindbrain that controls voluntary functions and controls the equilibrium. It is the second largest part of the brain, forming one eight of its mass.
NCERT Solutions for Class 11 Biology Chapter 21 : Neural Control and Coordination
NCERT Solutions for Class 11 Biology Chapter 21 Neural Control and Coordination – Brief Overview
21.1 – Neural System
In this, you will study the neural system which provides an organized network of point to point connection for quick coordination.
21.2 – Human Neural System
In this, you will study the human nervous system includes the coordination between the brain, spinal cord, nerves and body organs, human nervous system divided into two-part Central nervous system and peripheral nervous system.
21.3 – Neuron as Structural and Functional Unit of Neural System
In this, you will study about neuron which is a very important part of the human nervous system.
21.3.1 – Generation and Conduction of Nerve Impulse
In this, you will study the generation and conduction of nerve impulse by changing ion.
21.3.2 – Transmission of Impulses
In this, you will study the transmission of the nerve impulse by forming a synapse.
21.4 – Central Neural System
In this, you will study the central nervous system which consists of the brain and spinal cord.
21.4.1 – Forebrain
In this, you will study forebrain consists of the cerebrum, thalamus, and hypothalamus.
21.4.2 – Midbrain
In this, you will study midbrain which is located between hypothalamus and pons of the hindbrain, involved in relay of impulses back and forth between cerebrum, cerebellum, pons, and medulla.
21.4.3 – Hindbrain
In this, you will study hindbrain consists of pons, medulla oblongata and cerebellum.
21.5 – Reflex Action and Reflex Arc
In this, you will study about reflex action which is a spontaneous autonomic mechanical response to a stimulus without the will of the organism, reflex arc.
21.6 – Sensory Reception and Processing
In this, you will study about sensory reception means receiving the impulse and process them.
21.6.1 – Eye
In this, you will study about eye and its function, mechanism of vision.
21.6.2 – The Ear
In this, you will study about ear and its function, mechanism of hearing.
Frequently Asked Questions on NCERT Class 11 Biology Chapter 21 : Neural Control and Coordination
Q1. Are the NCERT Solutions for Class 11 Biology Chapter 21 Neural Control and Coordination from Toppr sufficient for the annual exam preparation?
Answer: The NCERT Solutions for Class 11 Biology Chapter 21 are framed based on the textbook content. The concepts are explained in simple and understandable language to help students grasp them easily and quickly. Relevant analogies are used wherever required to boost the final exam preparation of students. Neatly labelled diagrams for each concept are created to involve students in visual learning. Tables and pointers are used wherever necessary to help students learn new concepts effortlessly.
Q2. List out the topics which are important for the board exam in Chapter 21 of NCERT Solutions for Class 11 Neural Control and Coordination.
In NCERT Solutions for Class 11 Biology Chapter 21 you will learn about generation and conduction of nerve impulse, transmission of impulses, components of the central nervous system, forebrain, midbrain, hindbrain, spinal cord, autonomic nervous system, peripheral nervous system and sense organs like ears and eyes, structure, location and function of various organs of the human nervous system like brain, spinal cord, nerves.
- 21.1 – Neural System
- 21.2 – Human Neural System
- 21.3 – Neuron as Structural and Functional Unit of Neural System
- 21.4 – Central Neural System
- 21.5 – Reflex Action and Reflex Arc
- 21.6 – Sensory Reception and Processing