31 Years NEET Previous Year Questions: Neural Control & Coordination - 1 - NEET MCQ

• Statement I describes the corpus callosum, a structure in the brain. The corpus callosum is a large bundle of nerve fibers that connects the two cerebral hemispheres, allowing for communication between them. This statement is correct.
• Statement II mentions the brain stem and lists its components as the medulla oblongata, pons, and cerebrum. The error here is in including the cerebrum as part of the brain stem. In actuality, the brain stem consists of the medulla oblongata, the pons, and the midbrain, not the cerebrum. The cerebrum is part of the forebrain and is responsible for higher cognitive functions such as thinking, perceiving, planning, and understanding language. Therefore, Statement II is incorrect.

To match List I with List II correctly, we start by identifying the function of each brain region described in List I and match these descriptions to the corresponding functions stated in List II:

• Pons: The pons is part of the brainstem located between the midbrain and the medulla oblongata. It principally acts as a bridge connecting various parts of the brain, and it is also involved in controlling essential functions like sleep and respiration.
• Hypothalamus: The hypothalamus is a small portion at the base of the brain that plays a crucial role in hormone release and regulation of essential bodily functions, including temperature control, thirst, hunger, sleep, mood, and sexual behavior. It contains several neurosecretory cells that produce hormones.
• Medulla: The medulla oblongata, also part of the brainstem, primarily controls autonomic functions such as breathing, heart rate, and digestion (including gastric secretions).
• Cerebellum: The cerebellum is located at the back of the brain and is responsible for controlling motor skills, balance, coordination, and posture. It helps refine the movements dictated by the motor cortex.

Now, let's match these descriptions to those listed in List II:
A. Pons should match with "Connects different regions of the brain." - this corresponds to III.
B. Hypothalamus should match with "Neurosecretory cells." - this corresponds to IV.
C. Medulla should match with "Controls respiration and gastric secretions." - this corresponds to II.
D. Cerebellum should match with "Provides additional space for Neurons, regulates posture and balance." - this corresponds to I.

When we look at the given options:
Option A: A-II, B-III, C-I, D-IV (wrong)
Option B: A-III, B-IV, C-II, D-I (correct)
Option C: A-I, B-III, C-II, D-IV (wrong)
Option D: A-II, B-I, C-III, D-IV (wrong)

The correct answer is Option B: A-III, B-IV, C-II, D-I.

Option (a) is the correct answer because
(i) Fovea is the point of greatest visual acuity or resolution.
(ii) Iris is the visible coloured portion of the eye that regulates diameter of pupil.
(iii) Blind spot is the point where optic nerve leaves the eye-ball and photoreceptor cells are absent
(iv) Sclera is the external layer of eye formed of dense connective tissue.

• The limbic system, which includes structures such as the amygdala and hippocampus, plays a significant role in regulating emotions, including fear, pleasure, and anger. The hypothalamus, another component of the limbic system, is involved in various functions, including the regulation of sexual behavior and responses to pleasure and excitement. Therefore, option D is correct.
• Option (A), (B) and (C) are not correct because corpora quadrigemina is a part of the midbrain and consists of four round swellings. Corpus callosum is a tract of nerve fibres that connects right and left cerebral hemispheres. Thalamus is a major coordinating centre in the forebrain for sensory and motor signalling. Midbrain, pons and medulla oblongata together form the brain stem.

Option (c) is the correct answer as impulse transmission across an electrical synapse is always faster than that across a chemical synapse.

• Chemical synapses use chemicals for transmission which are known as neurotransmitters.
• The membranes of presynaptic and postsynaptic neurons are in close proximity in an electrical synapse.
• In an electrical synapse, the transmission of the impulse occurs in the form of an electrical current from one neuron to the next neuron.

Option (a) is the correct answer because
(a) Multipolar neurons are present in cerebral cortex.
(b) Bipolar neurons are found in the retina of the eye.
(c) Myelinated nerve fibres are found in spinal and cranial nerves
(d) Unmyelinated nerve fibres are commonly found in autonomous and somatic neural systems.

(a) Organ of corti is a structure located on the basilar membrane which contains hair cells that act as auditory receptors.
(b) Cochlea is the coiled portion of the labyrinth (fluid filled inner ear)
(c) Eustachian tube connects the middle ear cavity with the pharynx and helps in equalizing pressure of ear drums.
(d) Stapes is one of the ossicle of middle ear and is attached to oval window of cochlea.

• Option A: This statement is incorrect. The cornea is a transparent, avascular layer at the front of the eye that covers the iris, pupil, and anterior chamber.
• Option B: This statement is partially correct. The cornea is made up of a dense matrix of collagen fibers, but it is not the most sensitive portion of the eye. The most sensitive part of the eye is the conjunctiva, which is the thin, transparent layer that covers the white part of the eye and the inner surfaces of the eyelids.
• Option C: This statement is incorrect. The cornea is an external, transparent, and protective proteinaceous covering of the eye-ball.
• Option D: This statement is incorrect. The cornea is composed of dense connective tissue of collagen and cannot repair itself. Any injury to the cornea may result in permanent scarring or loss of vision.

Hypothalamus is thermoregulatory centre. Hence it is called “thermostat” of the body. It keeps body temperature at roughly 37°C by means of a complex thermostat system.

Nissl granules are composed of free ribosomes and RER. They are responsible for protein synthesis.

In the human eye, the lens is held in its place by suspensory ligament attached to the ciliary body.

• Medulla oblongata possess important centres for : Respiration, Cardiovascular reflexes, Gastric secretions.
• Corpus callosum : It is a tract of nerve fibres by which the hemispheres are connected with each other.
• Hypothalamus : It is centre for body temperature, urge for eating(hunger) and drinking (thirst).
• The limbic system (emotional motor system) is responsible for the experience and expression of emotion but not movement. It is located in the core of the brain and includes the amygdala, hippocampus and hypothalamus.

Myelin sheath wrapped around the nerve axon. Oligodendrocytes are neuroglial cells which produce myelin sheath in central nervous system while Schwann cell produces myelin sheath in peripheral nervous system.

• Vitamins A derivatives are formed from carotene which is a type of pigment that is found in certain foods, such as carrots, sweet potatoes, and spinach. The body converts carotene into vitamin A, which is essential for good vision.
• Retinal is a derivative of vitamin A and it is a light-absorbing part of all the visual photopigments. Photopigments are embedded in the membrane discs of the inner segment of the rod and cone cells in the retina.

Therefore, options (1), (3), and (4) are correct.

Pre-synaptic membrane is involved in the release of neurotransmitter in the chemical synapse. The receptors sites for neurotransmitters are present on postsynaptic membrane of neuron.

Photoreceptors in human eye are unique because they are only type of sensory cells that are relatively depolarised (about –35mV) when it is at rest (i.e., in the dark), and hyperpolarised (to about – 70mV) in response to adequate light stimulus. Nociceptors respond to potentially damaging stimuli that result in pain. Meissner’s corpuscles are a type of mechanoreceptor, responsible for touch sensitivity. Receptors generally produce graded potentials called receptor potentials.

The rods contain a photosensitive pigment called the rhodopsin. Rhodopsin is composed of opsin and retinene. The opsin is a protein and is called scotopsin in rhodopsin. The retinene is an aldehyde of vitamin A and is called retinal.

The anterior horns of spinal cord contains cells with fibres that form the anterior (motor) root end and are essential for the voluntary and reflex activity of muscles they innervate. If the anterior horn motor cells are destroyed, the nerves cannot regenerate and muscles are never useful again.

Vestibular apparatus has specific receptors called crista and macula to maintain the balance and posture of body.

Cerebellum maintains the balance and body posture. It is not concerned with logical part.

A small oval, yellowish area of the retina lying exactly opposite the centre of the cornea is named the macula lutea or yellow spot which has at its middle a shallow depression, the fovea centralis. The fovea centralis has cone cells only. It is devoid of rods and blood vessels. The fovea centralis is the place of most distinct vision.

Retinal is a derivative of vitamin A. Retinal is a polyene chromophore, and bound to proteins called opsins, is the chemical basis of animal vision. Bound to proteins called type 1 rhodopsins, retinal allows certain microorganisms to convert light into metabolic energy.

The hypothalamus is a highly complex structure in the brain that regulates many important brain chemicals. The hypothalamus is responsible for hormone production. The hormones produced by this area govern body temperature, thirst, hunger, sleep, circadian rhythm, moods, sex drive, and the release of other hormones in the body. This area of the brain controls the pituitary gland and other glands in the body.

In the given figure, A, B, C and D are axon, neurotransmitters, receptors and synaptic vesicles respectively.

Cerebrum is the first and most developed part of fore brain. It makes 2/3 part of total brain. Pons is a small spherical projection, which is situated below the midbrain and upper side of the medulla oblongata. It acts as a relay centre among different parts of brain. B and D are thalamus and spinal cord respectively.

A-Receptor, C-Synaptic vesicles B  is synaptic cleft. A synapse is  formed by the membranes of a synaptic neuron and post synaptic neuron, which may or may not separated by a gap called synaptic cleft. It is filled by fluid called neurotransmitter which are involved in transmission of impulse at these synapses.

The most abundant intracellular cation is K⁺.

Epinephrine and norepinephrine are secreted by adrenalmedulla in response to stress of any kind and during emergency situations and are called emergency hormones or hormones of flight, or fight.

Vestibular apparatus is a part of inner ear which has no role in hearing but responsible for the maintenance of balance of the body and posture.

The human hind brain comprises of pons, cerebellum and medulla oblongata.