21

Q1. Which one of the following does not act as a neurotransmitter?  

• 1) Norepinephrine  
• 2) Cortisone  
• 3) Epinephrine  
• 4) Acetylcholine  

Solution

Cortisone is a hormone released by the adrenal glands.  

Q2. Nodes of Ranvier are found in  

• 1) Non-myelinated nerve fibres  
• 2) Myelinated nerve fibres  
• 3) Both 1 and 2 above  
• 4) None of the above  

Solution

Nodes of Ranvier are found in myelinated nerve fibres. These are the gaps between two adjacent myelin sheaths.  

Q3. The area where the medullary sheath is absent in the nerve fibre is called  

• 1) Nissl's granules  
• 2) Node of Ranvier  
• 3) Schwann cells  
• 4) Schwann nodes  

Solution

The area where the medullary sheath is absent in the nerve fibre is called Node of Ranvier. These are the gaps between two adjacent myelin sheaths.  

Q4. Distinguish between the yellow spot and the blind spot.

Solution

Yellow Spot Blind Spot It is located lateral to the blind spot at the posterior pole of the eye. Blood vessels enter and the optic nerve leaves the eye at this spot. Cone cells are densely packed in this region. Photoreceptor cells, i.e. rods and cones, are absent. It is the region of sharpest vision. No vision is formed at the blind spot.  

Q5. State the significance of pinna.

Solution

Pinna collects vibrations from the surroundings to generate sound.

Q6. Nerve cells do not divide because they do not have

• 1) Mitochondria
• 2) Nucleus
• 3) Golgi body
• 4) Centrosome

Solution

Nerve cells do not divide because they do not have a centrosome which helps in cell division by forming microtubule-organising centres.

Q7. Mark the vitamin present in Rhodopsin

• 1) Vitamin B
• 2) Vitamin A
• 3) Vitamin C
• 4) Vitamin D

Solution

Rhodopsin, a visual purple pigment, is a derivative of vitamin A.

Q8. One of the examples of the action of the autonomous nervous system is

• 1) Knee-jerk response
• 2) Pupillary reflex
• 3) Peristalsis of the intestines
• 4) Swallowing of food

Solution

Peristalsis of the intestines is an example of the autonomous nervous system as it is an involuntary activity of the body and is not according to the will of an organism.

Q9. Which cells are responsible for the twilight or scotopic vision?

Solution

Rods

Q10. The purplish red pigment rhodopsin contained in the rod type of photoreceptor cells of the human eye is a derivative of

• 1) Vitamin A
• 2) Vitamin D
• 3) Vitamin B₁
• 4) Vitamin C

Solution

Rhodopsin, a visual purple pigment, is a derivative of vitamin A.

Q11. Study the following figure and name A, B, C and D.  

Solution

A - Tectorial membrane B - Scala media C - Reissner’s membrane D - Organ of Corti

Q12. Nissl’s granules are present in

• 1) RBC
• 2) WBC
• 3) Both 1 and 2 above
• 4) Nerve cells

Solution

Nissl’s granules are present in the cytoplasm of the cell body and the dendrites of the neuron.

Q13. Colour blindness is due to a defect in  

• 1) Rhodopsin  
• 2) Rods  
• 3) Cones  
• 4) Rods and cones  

Solution

Colour blindness is the inability to see colours. Lack of one or more types of cone cells causes colour blindness.  

Q14. Iris is part of

• 1) Choroid and retina
• 2) Sclerotic and choroid
• 3) Choroid
• 4) Sclerotic

Solution

The iris consists of two layers—outer one in continuation with the choroid and inner one in continuation with the retina.

Q15. Name the external layer of the eyeball.  

Solution

Sclera  

Q16. Name the gap which exists between pre-synaptic and post-synaptic neurons.

Solution

Synaptic cleft

Q17. Corpora striata occur in  

• 1) Cerebellum  
• 2) Medulla  
• 3) Cerebrum  
• 4) Diencephalon  

Solution

Corpora striata is present in the ventrolateral walls of the cerebral hemisphere.  

Q18. Colour perception in man is due to  

• 1) Rhodopsin pigment in cone cells  
• 2) Iodopsin pigment in rod cells  
• 3) Iodopsin pigment in cone cells  
• 4) Rhodopsin pigment in rod cells  

Solution

Colour perception in man is due to iodopsin pigment in cone cells. In the retina, there are three types of cones which respond to red (erythropsin), green (chloropsin) and blue light (cyanopsin). Other colours are detected by simultaneous stimulation of more than one type of cone cell.  

Q19. In human brain, the corpus callosum connects  

• 1) Two optic lobes  
• 2) Two lobes of the pituitary gland  
• 3) Two cerebral hemispheres  
• 4) Bone and muscle  

Solution

Two cerebral hemispheres are interconnected by a thick band of transverse nerve fibres called the corpus callosum.  

Q20. The human hindbrain comprises three parts, one of which is the

• 1) Corpus callosum
• 2) Hypothalamus
• 3) Spinal cord
• 4) Cerebellum

Solution

Cerebellum, pons and medulla oblongata are the three parts of the hindbrain.

Q21. Which part of the nervous system controls the reflex activity of the body?

• 1) Pons
• 2) Corpus callosum
• 3) Vermis
• 4) Spinal cord

Solution

The spinal cord controls the reflex activity of the body as it is a spontaneous automatic response to a stimulus. So, it reduces the work load of the brain.

Q22. State the function of the ear ossicles.

Solution

Ear ossicles increase the efficiency of the transmission of sound waves to the inner ear.

Q23. Chemicals which are released at the synaptic junction are called

• 1) Hormones
• 2) Lymph
• 3) Cerebrospinal fluid
• 4) Neurotransmitters

Solution

Neurotransmitters are the chemicals released from a presynaptic neuron which interact with specific receptor sites of a postsynaptic neuron.

Q24. Study the figure given below. Identify A, B, C and D.  

Solution

A - Fovea B - Cornea C - Retina D - Optic nerve

Q25. The myelin sheath is derived from  

• 1) Schwann cells  
• 2) All of the above  
• 3) Neuroglial cells  
• 4) Nerve cells  

Solution

In myelinated nerve fibres, the myelin sheath is derived from Schwann cells. It is present around the axon.  

Q26. Which layer of the eyeball contains more number of blood vessels?

Solution

Choroid layer

Q27. The wax gland present in the ear canal is called

• 1) Sweat gland
• 2) Prostate gland
• 3) Sebaceous gland/ceruminous gland
• 4) Cowper's gland

Solution

Wax glands present in the ear canal are called sebaceous glands or ceruminous glands. They secrete a brownish, semisolid, fatty substance called wax or cerumen.

Q28. Telescopic vision is found in

• 1) Frog
• 2) Rabbit
• 3) Birds
• 4) Dog

Solution

Telescopic vision is found in birds, i.e. they have the ability to see distant objects clearly.

Q29. How many pairs of spinal nerves are there in man?

• 1) 15
• 2) 31
• 3) 21
• 4) 10

Solution

There are 31 pairs of spinal nerves in man. These are classified into five groups: Cervical nerves - 8 pairs Thoracic nerves - 12 pairs Lumbar nerves - 5 pairs Sacral nerves - 5 pairs Coccygeal - 1 pair

Q30. The thermoregulatory centre in the body of a homeothermal animal and man is found in the

• 1) Cerebellum
• 2) Cerebrum
• 3) Hypothalamus
• 4) Medulla oblongata

Solution

The thermoregulatory centre is found in the hypothalamus of a homeothermal animal and man. It maintains homeostasis, i.e. it regulates the temperature of the body.

Q31. The mammalian brain differs from an amphibian brain in possessing

• 1) Hypothalamus
• 2) Cerebellum
• 3) Corpus callosum
• 4) Olfactory lobes

Solution

The mammalian brain has a corpus callosum which an amphibian brain does not possess. The corpus callosum is a large, curved tract of myelinated axons present at the bottom of the cerebral hemispheres.

Q32. The electrical potential difference between outside and inside of a nerve axon before excitation is known as

• 1) Activation potential
• 2) Reaction potential
• 3) Spike potential
• 4) Action potential
• 5) Resting potential

Solution

The electrical potential difference across the resting plasma membrane is called a resting potential.

Q33. The autonomic nervous system affects  

• 1) None of the above  
• 2) Sensory organs  
• 3) Reflex actions  
• 4) Internal organs  

Solution

The autonomic nervous system controls the functioning of involuntary visceral organs. It is formed of the sympathetic nervous system and the parasympathetic nervous system. Both these systems are antagonistic to each other.  

Q34. The corpus callosum is formed between two

• 1) Kidneys
• 2) Cerebral hemispheres
• 3) Auricles
• 4) Ventricles

Solution

The corpus callosum is a large, curved tract of myelinated axons present at the bottom of the cerebral hemispheres.

Q35. Where in the neural system are the multipolar neurons found?

Solution

Cerebral cortex

Q36. The sensitive pigmented layer of the eye is

• 1) Iris
• 2) Retina
• 3) Sclerotic
• 4) Cornea

Solution

The retina consists of a pigmented layer and a nervous tissue layer.

Q37. Name the system which transmits impulses from the central neural system to the skeletal muscles.  

Solution

Somatic neural system  

Q38. The supporting and nutritive cells found in the brain are  

• 1) Ependymal cells  
• 2) Oligodendrocytes  
• 3) Astrocytes  
• 4) Microglia  

Solution

Astrocytes are star-shaped glial cells present in the brain. These are supporting and nutritive cells and also maintain ionic balance in the brain.  

Q39. Name the membrane present above the hair cells in the cochlea.

Solution

Tectorial membrane

Q40. Name the fluid present outside the membranous labyrinth.

Solution

Perilymph

Q41. Which of the cells are phagocytic as well as scavengers?  

• 1) Oligodendrocytes  
• 2) Neurons  
• 3) Astrocytes  
• 4) Microglia  

Solution

Astrocytes, oligodendrocytes and microglia are three types of neuroglia. Astrocytes provide mechanical support to the neurons. Oligodendrocytes form myelin sheaths around the axon and microglia are phagocytic and scavengers. They engulf microbes and cellular debris.  

Q42. Name the visible coloured portion of the eye.

Solution

Iris

Q43. Which part of the brain controls intellectual ability?

• 1) Occipital lobe
• 2) Frontal lobe
• 3) Temporal lobe
• 4) Parietal lobe

Solution

In the frontal lobe of the cerebral hemisphere, thoughts and actions are monitored and creative ideas occur, so it controls all intellectual ability.

Q44. One of the following examples of an action of the autonomic nervous system is  

• 1) Knee jerk reflex  
• 2) Pupillary reflex  
• 3) Swallowing of food  
• 4) Peristalsis of intestine  

Solution

Peristalsis of intestine is an example of an action of the autonomic nervous system (ANS). ANS controls the function of visceral organs.  

Q45. Where are the non-myelinated neurons present in the neural system?  

Solution

Autonomic and somatic neural systems  

Q46. Name the two membranes of cochlea.

Solution

The two membranes of the cochlea are Reissner’s and basilar membranes.

Q47. Acute vision is present in

• 1) Shark
• 2) Bat
• 3) Vulture
• 4) Frog

Solution

Acute vision is found in birds like vulture.

Q48. What is reflex action? Explain the reflex pathway.

Solution

An involuntary response on stimulation of the peripheral nervous system which requires the involvement of a part of the central nervous system is called reflex action. The afferent neuron receives a signal from a sensory organ. It then transmits the impulse to the spinal cord via the dorsal root. The spinal cord sends the processed signal to the effectors through the efferent neuron forming a reflex arc.

Q49. The junction between the axon of one neuron and the dendrite of the next is called

• 1) Junction point
• 2) A joint
• 3) Synapse
• 4) Constant bridge

Solution

The junction between the axon of one neuron and the dendrite of the next is called a synapse. Depending on the nature of transfer of information, there are two types of synapses - chemical synapses and electrical synapses.

Q50. Name the ions to which the axonal membrane is more permeable during the resting potential.

Solution

Potassium ions

Q51. Which one of the following pairs of structures distinguishes a nerve cell from other types of cells?

• 1) Nucleus and mitochondria
• 2) Flagellum and medullary sheath
• 3) Vacuoles and fibres
• 4) Perikaryon and dendrites

Solution

Perikaryon and dendrites are present in a neuron. Perikaryon is a cytoplasm surrounding the nucleus. Dendrites are shorter, tapering and branched processes present in the cell body.

Q52. Describe the structure of a neuron.

Solution

Structure of neuron: Neuron is composed of cell body, dendrites and axon. The cell body contains cytoplasm. The cytoplasm consists of Nissl’s granules which are also present in dendrites. Dendrites are the short cytoplasmic branches given out by the cell body. Dendrites carry nerve impulse towards the cell body. Axon is the longest process given out by the cell body. In case of myelinated neuron, axon is covered with a myelinated sheath formed by Schwann cells. The gap between the two adjacent myelinated regions is called Node of Ranvier. The distal end of the axon called axon-terminal has bulb like structures call synaptic knobs which contain neurotransmitters.

Q53. Retina is most sensitive at

• 1) Optic disc
• 2) Fovea centralis
• 3) Macula lutea
• 4) Periphery

Solution

Macula lutea is a small area on the retina which lies opposite to the optical axis of the lens. It has a depression (the fovea centralis) in the middle. It is the area of most distinct day vision.

Q54. State the three types of neurons on the basis of number of axons and dendrites present. Also, state the number of axons and dendrites present and their location in the neural system.

Solution

The three types of neurons on the basis of number of axons and dendrites are Multi-polar neuron Bipolar neuron Unipolar neuron Multi-polar neuron: It has one axon and two or more dendrites. It is found in the cerebral cortex. Bipolar neuron:It has one axon and one dendrite. It is found in the retina of the eye. Unipolar neuron: It has a cell body with only one axon. It is found during embryonic development.

Q55. Name the ossicle which is attached to the oval window.

Solution

Stapes is attached to the oval window.

Q56. Nissl's granules are absent in the  

• 1) Dendron  
• 2) Axon  
• 3) Schwann cells  
• 4) Cyton  

Solution

The cyton and dendrites contain Nissl's granules. The axon does not have Nissl's granules. In myelinated nerve fibres, Schwann cells form a myelin sheath around the axon.  

Q57. The Nissl's granules of nerve cell are made up of

• 1) ribosomes
• 2) protein
• 3) RNA
• 4) DNA

Solution

Nissl's granules are the groups of ribosomes and rough endoplasmic reticulum. They are involved in synthesis of proteins.

Q58. What is the organ of Corti?

Solution

The organ of Corti comprises the structures which are present on the basilar membrane of the cochlea and which bear auditory receptor hair cells.

Q59. The decoding and interpretation of visual information are carried by the  

• 1) Frontal lobe  
• 2) Parietal lobe  
• 3) Temporal lobe  
• 4) Occipital lobe  
• 5) Cerebellum  

Solution

The cerebral hemisphere is divided into four lobes - anterior frontal lobe, middle parietal lobe, posterior occipital lobe and lateral temporal lobe.     The decoding and interpretation of visual information, shape and colour are carried by the occipital lobe.  

Q60. Which of the following is not involved in knee-jerk reflex?

• 1) Inter neurons
• 2) Muscle spindle
• 3) Brain
• 4) Motor neuron

Solution

The brain is not involved in the knee jerk reflex action as it is a spontaneous, automatic mechanical response to a stimulus without the will or thinking, of an organism.

Q61. State the name of the anterior thick part of the choroid layer.  

Solution

Ciliary body  

Q62. Name the pigment present in rod cells

Solution

Rhodopsin (visual purple)

Q63. Where is the vitreous chamber present?

Solution

The vitreous chamber is present between the lens and the retina.

Q64. The sense of smell is perceived by

• 1) Olfactory lobe
• 2) Pituitary
• 3) Cerebrum
• 4) Hypothalamus

Solution

The anterior part of the brain is formed by a pair of short club-shaped structures, the olfactory lobes. Olfactory lobes are concerned with the sense of smell.

Q65. Which of the following nerves is purely a motor nerve?  

• 1) Abducens  
• 2) Trigeminal  
• 3) Vagus  
• 4) Facial  

Solution

Abducens is a motor nerve which controls the movement of the eyeball. Vagus, facial and trigeminal are mixed nerves.  

Q66. Name the region in the eye where the photoreceptor cells are absent.

Solution

Blind spot

Q67. Name the pigment which is the derivative of vitamin A.

Solution

Rhodopsin is the derivative of vitamin A.

Q68. The organ of Corti is a structure present in the

• 1) Cochlea
• 2) Semicircular canal
• 3) External ear
• 4) Middle ear

Solution

The organ of Corti is a structure present in the cochlea on its basilar membrane.

Q69. The satiety centre of the brain is present in the  

• 1) Cerebral hemisphere  
• 2) Medulla oblongata  
• 3) Cerebellum  
• 4) Hypothalamus  

Solution

The centre of satiety, i.e. the feeling of being satisfied, is present in the hypothalamus of the brain.  

Q70. Cells of Schwann are associated with

• 1) Skeleton muscle
• 2) Cardiac muscle
• 3) Cartilage tissue
• 4) Connective tissue
• 5) Nervous tissue

Solution

The nervous tissue comprises a cell body (neuron) and neurites (dendrites and axon). In myelinated nerve fibres, Schwann cells form a myelin sheath around the axon.

Q71. Name the neurons which are found only during the embryonic stage.

Solution

Unipolar neurons

Q72. The sequence of ear ossicles from the outside to inside is

• 1) Stapes incus malleus
• 2) Incus stapes malleus
• 3) Malleus incus stapes
• 4) Malleus stapes incus

Solution

The sequence of ear ossicles from outside to inside is Malleus  incus  stapes. Human ear bones or ossicles are incus, malleus and stapes. The outer ossicle is hammer-shaped and is called the malleus. The inner ossicle is stirrup-shaped and is called the stapes. The middle ossicle is anvil-shaped and is called the incus.

Q73. Where are the eyes located?

Solution

Eyes are located in socket-like structures called orbits of the skull.

Q74. Name the two parts which form the outer ear.  

Solution

Pinna and external auditory meatus form the outer or external ear.  

Q75. At the resting potential, the inner axonal membrane contains K⁺ ions and negatively charged proteins and the fluid outside the membrane contains Na⁺ ions. What would be the charge present on the outer surface of the membrane during the action potential?

Solution

Negative charge

Q76. Name the two parts of the bony labyrinth formed due to the cochlea.  

Solution

Two parts of the bony labyrinth formed due to cochlea are     Upper scala vestibule   Lower scala tympani  

Q77. Name the region of the brain which analyses the image formed on the retina.  

Solution

The visual cortex of the brain analyses the image formed on the retina.  

Q78. The pigment iodopsin is contained in

• 1) Cone cells
• 2) Rod cells
• 3) Amacrine cells
• 4) Horizontal cells

Solution

Cone cells contain a visual violet pigment called iodopsin which is sensitive to bright day light.

Q79. Explain the structure of the cochlea.

Solution

The cochlea is a spiral structure present in the inner ear. Reissner’s membrane and the basilar membrane divide the bony labyrinth into the scala vestibuli and scala tympani which are filled with perilymph. The scala media is filled with endolymph. The organ of Corti is the sensory structure present in the cochlea. It is located on the basilar membrane and contains sensory hair cells which act as auditory receptors. These hair cells are present in rows, and their apical parts bear stereo cilia. A tectorial membrane which is thin is present above the rows of sensory hair cells.

Q80. What is the function of the association areas?  

Solution

Association areas are responsible for functions such as memory, communication and intersensory association.  

Q81. Apart from the skull, name the covering which protects the brain. Write the names of the three layers which form this protective covering.  

Solution

Cranial meninges.     It is made of the following three layers:     Outer dura mater   Middle arachnoid   Inner pia mater  

Q82. Describe the conduction of a nerve impulse through an axon.  

Solution

At resting potential, the outer surface of the axon has a positive charge and the axoplasm has a negative charge.     When a stimulus is received by the axon at resting potential, say at site A, the axonal membrane becomes freely permeable to Na⁺ ions.     This causes the rapid influx of Na⁺ ions which makes the outer surface of the membrane negatively charged, and the axoplasm is positively charged. Hence, the action potential is achieved.     The region ahead of the region, site B, which is the action potential will be still in the resting potential. Due to this, the current from site A flows to site B on the inner surface, and it flows from site B to site A on the outer surface.     This results in the reverse of polarity, and hence, the action potential is generated at site B.     This sequence is repeated along the length of the axon till the impulse reaches the axon terminal.  

Q83. Explain the mechanism of hearing in humans.

Solution

The pinna receives sound waves and directs them to the ear drum. The ear drum vibrates, and the vibrations are sent to the ear ossicles in the middle ear. The ear ossicles further transmit the vibrations to the oval window. The oval window passes the vibrations to the fluid of cochlea and causes vibrations in it. The vibrations induce a ripple in the basilar membrane which bends the hair cells, which are pressed against the tectorial membrane. This causes the generation of the nerve impulse which is transmitted to the brain via the auditory nerve. The impulses are analysed, and the sound is recognised or heard.

Q84. Draw a diagram showing the parts of an eye. Label any six parts.

Solution

 

Q85. The part of the brain concerned with muscular movements is

• 1) Hippocampus
• 2) Temporal lobe of cerebrum
• 3) Thalamus
• 4) Cerebellum

Solution

The cerebellum controls rapid muscular activities such as walking, running, typing, jogging etc.

Q86. Represent diagrammatically the conduction of an impulse through the axon.

Solution

The conduction of an impulse through axon:  

Q87. The receptor absent in the tongue is  

• 1) Photoreceptor  
• 2) Thermoreceptor  
• 3) None of the above  
• 4) Gustatoreceptor  

Solution

Thermoreceptors (for temperature) and gustatoreceptors (for taste) are present in the tongue. Photoreceptors (for light) are present in the eye but absent in the tongue.  

Q88. Name the three ossicles present in the ear.

Solution

Three ossicles present in the ear are malleus, incus and stapes.

Q89. Name the two structures of the external ear and state their functions.

Solution

The two structures of the external ear are pinna and external auditory meatus. The pinna collects vibrations from the surroundings to generate sound. The external auditory meatus connects the pinna to the tympanic membrane and carries vibrations to the tympanic membrane.

Q90. Name the ridge of the ampulla which is projected and contains hair cells.  

Solution

Crista ampullaris  

Q91. Draw a well-labelled diagram showing the sectional view of the cochlea.

Solution

 

Q92. How many sodium ions move outwards per two potassium ions during the conduction of nerve impulse?

Solution

Three sodium ions

Q93. Where is the endolymph present?

Solution

Endolymph is present in the membranous labyrinth and the scala media of cochlea.

Q94. Name the pigment spot present at the posterior pole of the eye.  

Solution

Macula lutea  

Q95. Name the space between the cornea and the lens.

Solution

Aqueous chamber

Q96. Name the two photoreceptor cells present in the eye.

Solution

Rods and cones

Q97. Resting membrane potential is maintained by  

• 1) None of the above  
• 2) Hormones  
• 3) Ion pumps  
• 4) Neurotransmitters  

Solution

The resting membrane potential is maintained by a sodium-potassium pump.  

Q98. Explain the conduction of the nerve impulse at a chemical synapse.  

Solution

Pre-synaptic and post-synaptic neurons are separated from each other by a synaptic cleft filled with a fluid.           When the impulse reaches the axon terminal of the pre-synaptic neuron, it stimulates the movement of synaptic vesicles containing neurotransmitters towards the axon terminal to fuse with the plasma membrane.     When synaptic vesicles fuse with the plasma membrane, they release neurotransmitters.     These neurotransmitters travel through the synaptic cleft and bind to the receptors present on the post-synaptic membrane.     This binding opens the channels on the post-synaptic membrane which allows the entry of ions.     The entry of ions into the post-synaptic neuron generates a new potential.  

Q99. In frog, "fenestra ovalis" is

• 1) the air-filled cavity of the middle ear
• 2) the opening in the auditory capsule which separates the middle ear from internal ear
• 3) the external opening of the tympanic cavity which is covered by the tympanic membrane
• 4) the communication between the pharynx and the tympanic cavity

Solution

"Fenestra ovalis" is an oval aperture through which tympanic cavity is connected with auditory capsule which houses the internal ear.

Q100. When is the sensation of white light produced?  

Solution

When the cones responsible for different colours are stimulated equally, white light is produced.  

Q101. How is the action potential achieved by a neuron?  

Solution

When a stimulus is received by the axon which is in the resting potential at certain site, say at site A, the axonal membrane becomes freely permeable to Na⁺ ions.     This causes the rapid influx of Na⁺ ions which makes the outer surface of the membrane negatively charged, and the axoplasm is positively charged.     The changes in the permeability of the membrane and influx of Na⁺ ions reverse the polarity of the membrane, and thus, the action potential achieved by the axon.  

Q102. Name the layer of cranial meninges which is in direct contact with the brain tissue.

Solution

Pia mater

Q103. In mammals, the brain centre which regulates body temperature is situated in the

• 1) Hypothalamus
• 2) Cerebellum
• 3) Cerebral lobe
• 4) Medulla oblongata

Solution

In mammals, the hypothalamus maintains homeostasis, i.e. it regulates body temperature.

Q104. Differentiate between aqueous chamber and vitreous chamber.

Solution

Aqueous Chamber Vitreous Chamber It is the space between the cornea and the lens. It is the space between the lens and the retina. It is filled with a fluid called the aqueous humour. It is filled with the vitreous humour.  

Q105. Differentiate between myelinated nerve fibres and non-myelinated nerve fibres.  

Solution

Myelinated Nerve Fibres     Non-myelinated Nerve Fibres     These nerve fibres have a myelinated sheath made of Schwann cells.   These nerve fibres are enclosed by Schwann cells, but they do not form a myelinated sheath around the nerve fibres.   They are found in spinal and cranial nerves.   They are found in the autonomic and somatic nervous systems.      

Q106. What is the significance of the corpus callosum?

Solution

The corpus callosum connects the two cerebral hemispheres.

Q107. Which part of the human brain is the largest?

• 1) Thalamus
• 2) Cerebellum
• 3) Medulla
• 4) Cerebrum

Solution

The cerebrum or cerebral hemisphere forms the largest part of the brain. It constitutes four-fifths of the brain weight.

Q108. Name the photosensitive compounds present in the photopigments.

Solution

The photosensitive compounds present in the photopigments are Opsin - a protein and retinal (an aldehyde of vitamin A).

Q109. What is the other name for the ear drum?

Solution

The other name for the ear drum is tympanic membrane.

Q110. Name the pigment present in the photopigments.

Solution

Opsin

Q111. Name the canal which passes through the midbrain.  

Solution

Canal aqueduct  

Q112. Protein found in the eye lens is  

• 1) Collagen  
• 2) Rhodopsin  
• 3) Opsin  
• 4) Crystallin  

Solution

Crystallin is a water-soluble protein present in the eye lens and cornea of the eye.  

Q113. Name the two structures of the brain which form the limbic system.  

Solution

Amygdala and hippocampus  

Q114. Differentiate between rods and cones.

Solution

Rods Cones Rods are responsible for daylight and colour vision. Cones are responsible for the twilight or scotopic vision. Rods contain a purple-red pigment called rhodopsin. Cones contain a pigment called iodopsin.  

Q115. Name the ossicle to which the tympanic membrane is attached.

Solution

Malleus

Q116. What are the two nerve fibres of PNS?

Solution

The two nerve fibres of PNS are Afferent fibres Efferent fibres

Q117. Name the cells which form a myelinated sheath around a myelinated nerve fibre.

Solution

Schwann cells

Q118. Distinguish between axon and dendrite.

Solution

Axon Dendrite It is the longest fibre given out by the cell body of a neuron. Dendrites are small branches given out by the cell body. It carries impulses away from the cell body. It carries impulses towards the cell body.  

Q119. Define coordination in living organisms. Why is it necessary? Give any one example.

Solution

Coordination is the process in which one or more tissues or organs interact and complement the function of each other to maintain the homeostasis of the body. During physical exercise, there is always increased energy demand. To fulfil this demand, the supply of oxygen to the cells in concern increases. To provide more oxygen, our respiration rate, heartbeat and blood flow increase.

Q120. What are synapses?

Solution

Synapses are the nerve junctions at which nerve impulses are transmitted from one neuron to another neuron.

Q121. Draw a well-labelled diagram to explain the transmission of the nerve impulse at a synapse.

Solution

Transmission of nerve impulse at synapse:  

Q122. Describe the mechanism of the formation of vision or image.

Solution

The light rays of the visible length are focused on the retina through the cornea and the lens. This light generates impulse in the rods and cones which contain photosensitive pigments composed of opsin and retinal. The light brings about the dissociation of retinal from opsin which brings about changes in the structure of opsin. The change in the structure of opsin causes changes in membrane permeability which generates an action potential in the ganglion cells through the bipolar cells. Once the change in action potential is transmitted to the brain through the optic nerve, the brain sends the signals back to the eye forming the image of the retina.

Q123. Name the region where the cone cells are densely packed.

Solution

At the fovea, the cone cells are densely packed.

Q124. Name the two main divisions of the peripheral neural system.

Solution

Two main divisions of the peripheral neural system are Somatic neural system Autonomic neural system

Q125. Name the middle layer of the cranial meninges.

Solution

Arachnoid

Q126. Name the structure which connects the middle ear and the pharynx. Also state its function.

Solution

The Eustachian tube connects the middle ear and the pharynx. It equalises the pressure on either side of the tympanic membrane or the ear drum.

Q127. Draw a well-labelled diagram of the sagittal section of the human brain.

Solution

Human brain:  

Q128. Draw a labelled diagram of a neuron.

Solution

Neuron:  

Q129. Cornea transplantation is outstandingly successful because

• 1) Cornea is easily available
• 2) Cornea is easy to preserve
• 3) The technique involved is very simple
• 4) Cornea is not linked with blood vascular and immune systems

Solution

Cornea is non-vascular. So, its transplantation is successful.

Q130. In which parts of the neural system are the myelinated nerve fibres found?

Solution

Spinal and cranial nerves

Q131. Eyes are the most important sense organs in animals without which it would have been difficult to experience the beauty of life. Name the photoreceptor cells and their pigments present in the retina. Name the compounds present in the photopigments. State the functions of rods and cones. What values do you learn from questions (a) and (c)?

Solution

Cones and rods. Iodopsin is present in cone cells, and rhodopsin is present in rid cells. Opsin and retinal are present in photopigments. Rod cells are responsible for coloured and daylight vision, while cones are responsible for twilight vision. In team work, to achieve success in any task, synchronisation in the work of team members is of utmost importance.

Q132. Name the granular bodies present in the cytoplasm of neurons.

Solution

Nissl’s granules

Q133. Draw a labelled diagram of the ear.

Solution

Ear:  

Q134. Write the significance of the autonomic neural system.

Solution

The autonomic neural system transmits nerve impulses from the central neural system to the involuntary organs and smooth muscles of the body.

Q135. Which types of neurons are found in the retina of the eye?

Solution

Bipolar neurons

Q136. State the significance of the cone cells.

Solution

Cone cells are responsible for colour vision and photopic vision.

Q137. Name the three cells present in the retina of the eye.  

Solution

Three cells present in the retina of the eye are ganglion cells, bipolar cells and photoreceptor cells.  

Q138. Name the structures which constitute the vestibular apparatus.  

Solution

Semicircular canals and the otolith organ constitute the vestibular apparatus.  

Q139. State the two main parts of the human neural system.

Solution

Two main parts of the human neural system are Central Neural System (CNS) Peripheral Neural System (PNS)

Q140. Name the region of the brain responsible for controlling body temperature.

Solution

Hypothalamus

Q141. At the action potential, what charge is present on the inner surface of the axonal membrane?

Solution

Positive charge

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