Free Coordination and Control MCQs with Answers

11. Transmission across a chemical synapse is one way because

• A. the postsynaptic membrane is thicker
• B. the neurotransmitter is released only from the presynaptic knob and receptors are only on the postsynaptic membrane
• C. the synaptic cleft is too wide for diffusion in the reverse direction
• D. the impulse loses all its energy at the synapse

Explanation: Vesicles of transmitter are stored on one side only and the matching receptors are on the other, so the signal cannot cross backwards even though diffusion itself has no preferred direction. This one way valve is what gives the nervous system its organised pathways. The cleft is only about 20 nanometres wide, so diffusion across it takes well under a millisecond.

12. The correct sequence of components in a spinal reflex arc is

• A. effector, motor neurone, spinal cord, sensory neurone, receptor
• B. receptor, motor neurone, spinal cord, sensory neurone, effector
• C. receptor, sensory neurone, interneurone in the spinal cord, motor neurone, effector
• D. sensory neurone, receptor, effector, motor neurone, spinal cord

Explanation: The stimulus is detected by the receptor, carried into the spinal cord by the sensory neurone through the dorsal root, passed to a relay neurone and then out along the motor neurone through the ventral root to the muscle or gland that responds. Sensory always means towards the central nervous system and motor always means away from it, which is enough to rule out the reversed options.

13. A reflex action such as withdrawing the hand from a hot object is fast because

• A. the impulses travel through the cerebrum first
• B. only one neurone is involved in the whole pathway
• C. hormones carry the message directly to the muscle
• D. the response is organised in the spinal cord without waiting for the brain

Explanation: The reflex arc is completed at spinal level, so the muscle contracts before the impulses climbing to the brain arrive and the pain is consciously felt, which is what makes the response protective. The brain is informed afterwards and can modify or suppress some reflexes, but it is not needed for the action itself. At least three neurones are involved, and hormones are far too slow for this.

14. In the spinal cord, unlike the cerebrum, the grey matter

• A. lies on the inside and the white matter surrounds it
• B. lies on the outside and the white matter is central
• C. is entirely absent
• D. contains only myelinated fibres

Explanation: The butterfly shaped core of grey matter contains the cell bodies and synapses, while the outer white matter is made of myelinated axons running up and down the cord, and myelin is what makes that region look white. In the brain the arrangement is inverted, with the grey cortex outside. Recognising the pattern is how a spinal cord section is identified under the microscope.

15. The part of the brain concerned with intelligence, memory and voluntary action is the

• A. cerebellum
• B. cerebrum
• C. medulla oblongata
• D. hypothalamus

Explanation: The cerebrum is the largest part of the human brain, and its folded cortex carries the sensory, motor and association areas responsible for thought, language, memory and conscious decision. Its folding increases the surface area enormously within the fixed volume of the skull. The cerebellum and medulla handle coordination and vital automatic functions and have nothing to do with conscious thought.

16. Damage to the cerebellum would most likely result in

• A. loss of memory
• B. failure of breathing
• C. loss of balance and jerky, poorly coordinated movement
• D. inability to see

Explanation: The cerebellum receives information from the muscles, joints and balance organs of the ear and smooths the commands sent by the cerebrum, so injury to it leaves movement clumsy and unsteady even though strength is normal. Alcohol depresses the cerebellum, which is why an intoxicated person staggers. Breathing is controlled by the medulla and vision is processed in the occipital lobe of the cerebrum.

17. Heart rate, breathing rate and the diameter of blood vessels are controlled by the

• A. cerebrum
• B. cerebellum
• C. corpus callosum
• D. medulla oblongata

Explanation: The medulla lies at the top of the spinal cord and contains the cardiac, respiratory and vasomotor centres, all of which work without conscious control, so an injury there is very quickly fatal. Because these centres monitor carbon dioxide and blood pressure and correct them, the medulla is a key homeostatic organ. The corpus callosum is only the bundle of fibres joining the two cerebral hemispheres.

18. The part of the brain that regulates body temperature, thirst and hunger, and controls the pituitary gland is the

• A. hypothalamus
• B. cerebellum
• C. medulla oblongata
• D. occipital lobe

Explanation: The hypothalamus is the meeting point of the nervous and endocrine systems: it monitors the temperature and water potential of the blood, generates thirst and hunger, and releases factors that control the anterior pituitary while making the hormones the posterior pituitary stores. Its small size is out of all proportion to its importance in homeostasis. The occipital lobe deals with vision alone.

19. Insulin lowers the concentration of glucose in the blood by

• A. converting glycogen in the liver into glucose
• B. increasing the uptake of glucose by cells and its storage as glycogen in the liver and muscle
• C. increasing the excretion of glucose in the urine
• D. stopping the digestion of carbohydrate in the gut

Explanation: Insulin from the beta cells of the islets of Langerhans makes cell membranes more permeable to glucose and stimulates the enzymes that build glycogen, so glucose leaves the blood. Glucagon from the alpha cells does the opposite, breaking glycogen down when blood glucose falls, and the two hormones form a negative feedback pair. Glucose in the urine is a symptom of untreated diabetes, not the way the hormone works.

20. A person whose diet lacks iodine may develop a goitre because

• A. iodine is needed to make insulin
• B. iodine destroys the thyroid gland directly
• C. the thyroid cannot make enough thyroxine and enlarges under continued stimulation by the pituitary
• D. excess iodine accumulates in the neck

Explanation: Thyroxine contains iodine, so a shortage means output falls, and the low blood level removes the negative feedback on the pituitary, which keeps releasing thyroid stimulating hormone until the gland swells visibly. This is why iodised salt is used to prevent goitre in areas where the soil is deficient. Insulin is made in the pancreas and contains no iodine at all.