Free Coordination and Control MCQs with Answers

71. Which part of the brain contains central chemoreceptors that monitor CO2 levels in blood?

• A. Pons
• B. Midbrain
• C. Hypothalamus
• D. Medulla oblongata

Explanation: The respiratory centre of the medulla carries chemoreceptors that detect the fall in pH caused by rising carbon dioxide and increase the rate and depth of breathing until the excess is blown off. Oxygen level is monitored elsewhere, by peripheral receptors in the aorta and carotid arteries, and acts only as a weak backup stimulus. This is why holding the breath becomes unbearable from carbon dioxide build up rather than from lack of oxygen.

72. Which component of a reflex arc connects the sensory neuron to the motor neuron within the spinal cord?

• A. Receptor
• B. Effector
• C. Muscle fiber
• D. Associative neuron

Explanation: The associative or relay neurone sits in the grey matter of the spinal cord and passes the impulse straight from the sensory to the motor neurone, which is what allows the response to happen before the brain is even informed. The receptor detects the stimulus at the start of the arc and the effector, usually a muscle or gland, produces the response at the end. A muscle fibre is part of the effector rather than a link in the pathway.

73. Nissl granule is a specialized structure in neuron formed by modification of:

• A. Golgi bodies & Smooth ER
• B. Peroxisome & Mitochondria
• C. Lysosome & Vacuole
• D. Ribosome & Rough ER

Explanation: Nissl granules are dense stacks of rough endoplasmic reticulum studded with ribosomes, which is why they stain so darkly and why they are concentrated in the cell body where protein synthesis for the whole neurone takes place. Smooth ER carries no ribosomes and handles lipid synthesis instead. Their disappearance after injury, called chromatolysis, is a standard sign of nerve cell damage.

74. Which of the following is the auditory relay Centre and Centre that controls reflex movement of eyes?

• A. Forebrain
• B. Cerebellum
• C. Midbrain
• D. Cerebellum

Explanation: The midbrain carries four swellings, the corpora quadrigemina, of which the upper pair handle visual reflexes such as turning the eyes and head towards a movement and the lower pair relay auditory information. The cerebellum coordinates balance and fine movement but relays neither sound nor visual reflexes. Note that options (b) and (d) were printed identically in the original paper, which is a misprint in the paper itself and does not affect the correct answer.

75. Which of the following is the correct pathway of nerve impulse?

• A. Receptors to CNS to Effectors
• B. Effectors to Receptors to CNS
• C. CNS to Effectors to Receptors
• D. Effectors to CNS to Receptors

Explanation: A receptor detects the stimulus, a sensory neurone carries the impulse into the central nervous system, and a motor neurone carries the instruction out to the effector that responds. The direction is fixed by the one way nature of the synapse, since transmitter is released on one side only and receptors sit on the other. Any pathway beginning at the effector reverses the whole logic of the reflex.

76. The neurotransmitters are secreted by the neuron from:

• A. Axon ends
• B. Dendrite end
• C. Nissl's granules
• D. Cell body

Explanation: Vesicles of transmitter are stored in the swollen endings of the axon and released into the synaptic cleft when the impulse arrives. Dendrites carry the receptors that detect the transmitter on the other side of the synapse, which is why they are the tempting answer. This arrangement, with release on one side and reception on the other, is exactly what makes transmission one way.

77. Hippocampus plays an important role in the:

• A. Formation of short-term memory
• B. Formation of image on retina
• C. Formation of long-term memory
• D. Formation of emotions

Explanation: The hippocampus consolidates experiences into long term memory, which is why damage to it leaves a patient able to hold a conversation yet unable to form any lasting new memory. Short term working memory depends mainly on the prefrontal cortex, and emotion is handled largely by the amygdala nearby. Image formation on the retina is optical and involves no part of the brain at all.

78. Left and right cerebral hemispheres are connected with each other by:

• A. Corpus luteum
• B. Corpus callosum
• C. A band of dendrites
• D. Dorsal and ventral nerve roots

Explanation: The corpus callosum is a thick band of myelinated axons carrying traffic between the two hemispheres so that they work as one. The corpus luteum is the very similar sounding structure in the ovary that secretes progesterone after ovulation, and it is the deliberate trap here. Dorsal and ventral roots belong to the spinal nerves, not the brain.

79. Which part of the neuron typically receives incoming signals from other neurons?

• A. Axon
• B. Dendrites
• C. Myelin sheath
• D. Synaptic knob

Explanation: Dendrites are the short branched processes that carry receptors for neurotransmitter and conduct the resulting signal towards the cell body. The axon carries impulses away, and its synaptic knobs are where transmitter is released rather than received. Myelin is an insulating sheath that speeds conduction and plays no part in reception.

80. Olfactory receptors are the type of:

• A. photoreceptors
• B. mechanoreceptors
• C. thermoreceptors
• D. chemoreceptors

Explanation: Smell depends on molecules dissolving in the mucus and binding receptor proteins in the nasal epithelium, so olfactory receptors respond to chemicals and are chemoreceptors, as are the taste buds. Photoreceptors detect light in the retina and mechanoreceptors detect pressure, touch and sound. Classifying a receptor means asking which form of energy or signal it transduces.