NCERT Exemplar Class 11 Biology Solutions Neural Control and Coordination
Multiple Choice Questions
1.Chemicals which are released at the synaptic junction are called
(c) cerebrospinal fluid
Solution. (b) : A typical synapse consists of a bulbous expansion of a nerve terminal called a pre-synaptic knob lying close to the membrane of a dendrite. The cytoplasm of the synaptic knob contains mitochondria, smooth endoplasmic reticulum, microfilaments and numerous synaptic vesicles. Each vesicle contains neurotransmitter (chemical substance) responsible for the transmission of the nerve impulse across the synapse.
2.Potential difference across resting membrane is negatively charged. This is due to differential distribution of the following ions
(a) Na+ and K+ ions
(b) C03++andCI ions
(c) Ca++ and Mg++ ions
(d) Ca+4 and Cl– ions.
3.Resting membrane potential is maintained by
(c) ion pumps
(d) none of the above.
Solution.(c): The concentration gradients across the resting membrane are maintained by the active transport of ions by the sodium- potassium pump which transports 3 Na+ outward for 2 K+ into the cell.
4.The function of our visceral organs is controlled by
(a) sympathetic and somatic neural system
(b) sympathetic and parasympathetic neural system
(c) central and somatic neural system
(d) none of the above.
Solution. (b) : Sympathetic and parasympathetic neural systems are the part of autonomic neural system. This system controls and coordinates the functions of visceral organs.
5.Which of the following is not involved in knee-jerk reflex? .
(a) Muscle spindle (b) Motor neuron (c) Brain (d) Inter neurons
6.An area in the brain which is associated with strong emotions is
(a) cerebral cortex (b) cerebellum (c) limbic system (d) medulla.
Solution.(c): Certain components of the cerebrum and diencephalon constitute the limbic system. It is sometimes called the “emotional brain” because it controls emotional behaviour expressed in the form of joy, sorrow, fear, fight, friendship, liking and disliking.
7.Mark the vitamin present in rhodopsin.
(a) VitA (b) VitB.
(c) VitC (d) VitD
Solution.(a) : Rhodopsin is a pigment present in the rod cells of the retina. It consists of two components-opsin and retinal (= retenene). Retinal is an aldehyde of vitamin A, absorbs light falling on the rod and changes its form and separates from the opsin component. This initiates the transmission of a nerve impulse to the brain. Rhodopsin allows vision in dim light (night vision).
8.Human eyeball consists of three layers and it encloses
(a) lens, iris, optic nerve
(b) lens, aqueous humour and vitreous humour
(c) cornea, lens, iris
(d) cornea, lens, optic nerve.
9.Wax gland present in the ear canal is called
(a) sweat gland
(b) prqstate gland
(c) Cowper’s gland
(d) sebaceous gland/ ceruminous gland.
Solution.(d) : Ear canal is lined by hairy skin and ceruminous glands (wax glands). These – glands secrete a waxy substance cerumen (ear wax) which prevents the foreign bodies entering the ear.
10.The part of internal ear responsible for hearing is
(a) cochlea (b) semicircular canal
(c) utriculus (d) sacculus.
Solution.(a) : Internal ear is a delicate, irregular organ called labyrinth, which consists of two parts; bony and membranous labyrinth. Membranous labyrinth consists of 3 parts : vestibule, semicircular canals and cochlea. Cochlea is the main hearing organ.
11.The organ of Corti is a structure present in
(a) external ear
(b) middle ear
(c) semicircular canal
Solution.(d) : Cochlea is the main hearing organ in the internal ear. Internally, it consists of three fluid filled chambers the upper scala vestibuli, lower scala tympani and middle scala media. Scala media bears an upper membrane the Reissner’s membrane, and a lower membrane, the basilar membrane. On the basilar membrane, the organ, of Corti is present.
Short Answer Type Questions
1.Rearrange the following in the correct order of involvement in electrical impulse movement- Synaptic knob. Dendrites, Cell body. Axon terminal. Axon.
Dendrites > Cell body > Axon > Axon terminal > Synaptic knob.
2.Comment upon the role of ear in maintaining the balance of the body and posture.
Solution. The crista and macula are the specific receptors of the vestibular apparatus of the internal ear responsible for maintenance of balance of the body and posture.
3.Which cells of the retina enable us to see coloured objects around us?
4.Arrange the following in the order of reception and transmission of sound wave from the ear drum:
Cochlear nerve.External auditoru canal, Ear drum, Stapes, Incus, Malleus, Cochlea.
External auditory canal, >Ear drum, > Stapes, > Incus, >Malleus, > Cochlea
5.During resting potential, the axonal membrane is polarised, indicate the movefnent of +ve and -ve ions leading to polarisation diagrammatically.
6. Name the structures involved in the protection of the brain.
Solution.The brain is protected by the skull. Inside the skull, the brain is covered by cranial meninges consisting of an outer layer called duramater, a very thin middle layer called arachnoid and an inner layer (which is in contact with the brain tissue) called pia mater.
7.Our reactions like aggressive behaviour, use of abusive words, restlessness etc. are regulated by brain, name the parts involved.
Solution. Inner parts of cerebral hemispheres and group of associated deep structures like amygdala, hippocampus and hypothalamus.
8.What do grey and white matter in the brain represent?
Solution.The cerebral cortex is referred to as the grey matter due to its greyish appearance because of the colour provided by neuron cell bodies. The inner part of the cerebral hemisphere consists of fibres of the tracts covered with myelin sheath. They give an opaque white appearance to the tissue and hence is called the white matter.
9. Where is the hunger centre located in human brain?
10.Which sensory organ is involved in vertigo (sensation of oneself or objects spinning around)?
11.While travelling at a higher altitude, a person complains of dizziness and vomiting sensation. Which part of the inner ear is disturbed during the journey?
12.Complete the statement by choosing appropriate match among the following.
Solution. (a) – (iii), (b) – (iv), (c) – (ii), (d) – (i)
Short Answer Type Questions
1.The major parts of the human neural system is depicted below. Fill in the empty boxes with appropriate words.
2 What is the difference between electrical transmission and chemical transmission?
Solution.Differences between electrical transmission and chemical transmission are:
3.Neural system and computers share certain common features. Comment in five lines. (Hint: CPU, input-output devices).
Solution. Neural system consists of sensory organs that detect changes in the external environment and sensory nerves carry sensory impulses from these organs to CNS. These sensory organs and sensory nerves can be compared to input devices of computer. This information is processed in CNS which can be compared to CPU of computer. Then, motor nerves carry motor impulses from CNS to target tissues / organs which then act accordingly. These motor nerves and target tissues / organs can be compared to output devices of computer.
4.If someone receives a blow on the back of neck, what would be the effect on the person’s CNS?
Solution. If someone receives a blow on the back of the neck, then his medulla oblongata would get hurt, as this is the place where it is located. The person might die as medulla controls respiration, cardiovascular reflexes and gastric secretions.
5.What is the function ascribed to Eustachian tube?
Solution. Eustachian tube connects the middle ear cavity with the pharynx. It helps in equalising the pressures on either sides of the ear drum.
6.Label the following parts in the given diagram using arrow.
(a) Aqueous chamber
(e) Vitreous chamber
(f) Blind spot
Long Answer Type Questions
1.Explain the process of the transport and release of crneurotransmitter with the help of a labelled diagram showing a complete neuron, axon terminal and synapse.
Solution. Chemicals called neurotransmitters are involved in the transmission of impulses at chemical synapses. The axon terminals contain vesicles filled with these chemicals. When an impulse arrives at the axon terminal, it stimulates the movement of the synaptic vesicles towards the membrane where they fuse with the plasma membrane and release their neurotransmitters in the synaptic cleft. The released neurotransmitters bind to their specific receptors, present on the post-synaptic membrane. This binding opens ion channels allowing the entry of ions which can generate a new potential in the post-synaptic neuron.
Fig.: Diagram showing neuron, axon terminal and synapse
2.Name the parts of human forebrain indicating their respective functions.
Solution. The forebrain consists of cerebrum, thalamus and hypothalamus. The cerebrum contains motor areas, sensory areas and large regions that are neither clearly sensorv nor motor in function. These regions known as the association areas are responsible for complex functions like intersensory associations, memory and communication. Thalamus is a major coordinating centre for sensory and motor signaling. The hypothalamus contains a number of centres which control body temperature, urge for eating and drinkings It also contains neurosecretory cells which secrete hypothalamic hormones. The inner parts of cerebral hemisphere and a group of associated deep structures like amygdala, hippocampus etc. form a complex structure called the limbic system. Hypothalamus and limbic system are involved in the regulation of sexual behaviour, expression of emotional reactions and motivation.
3.Explain the structure of middle and internal ear with the help of diagram.
Solution.Middle ear : The middle ear contains three ossicles called malleus (hammer shaped), incus (anvil shaped) and stapes (stirrup shaped) which are attached to one another in a chain – like fashion. The malleus is attached to the tympanic membrane and the stapes is attached to the oval window of the cochlea. The function of the ear ossicles is to increase the efficiency of transmission of sound waves to the inner ear.
Inner ear : The fluid filled inner ear called labyrinth is divided into two parts, the bony labyrinth and the membranous labyrinth. The bony labyrinth is a series of channels, inside which lies the membranous labyrinth. It is surrounded by a fluid called perilymph. The membranous labyrinth is filled with a fluid called endolymph. The coiled portion of the labyrinth is called cochlea. Reissner’s membrane and basilar membrane constituting cochlea, divide the perilymph filled bony labyrinth into an upper scala vestibule and a lower scala tympani. The space within cochlea called scala media is filled with endolymph.
At the base of the cochlea, the scala vestibuli ends at the oval window, while the scala tympani terminates at the round window which opens to the middle ear. A structure called organ of corti located on the basilar membrane contains hair cells that act as auditory receptors. The basal end of the hair cell is in close contact with the afferent nerve fibres. Stereo cilia, the processes project from the apical part of each hair cell. Above the rows of the hair cells is a thin elastic membrane called tectorial membrane. Located above the cochlea in a complex system called vestibular apparatus. The vestibular apparatus is composed of three semi-circular canals and the otolith organ consisting of the saccule and utricle. Each semi-circular canal lies in a different plane at right angles to each other. The base of canals is swollen and is called ampulla, which contains a projecting ridge called crista ampullaris which has hair cells. A projecting ridge called macula is present in the saccule and utricle. The crista and macula are responsible for maintenance of balance of the body and posture.