Free Coordination and Control MCQs with Answers

1. Which organ produces insulin in the human body?

• A. Liver
• B. Pancreas
• C. Thyroid gland
• D. Adrenal gland

Explanation: Insulin is produced by the beta cells of the islets of Langerhans in the pancreas, and it lowers blood glucose. The alpha cells of the same islets produce glucagon, which raises it.

2. The receptors of the retina that allow vision in dim light are the

• A. cones
• B. rods
• C. ganglion cells
• D. cells of the blind spot

Explanation: Rods contain the pigment rhodopsin, which is broken down by very low light intensities, and several rods share one sensory neurone so their effects add up, making them extremely sensitive. The price of that pooling is poor detail and no colour discrimination, which is why night vision is grey and blurred. Cones need bright light and give sharp colour vision instead.

3. Visual acuity is greatest at the fovea because it contains

• A. only rods, packed very closely
• B. no photoreceptors at all
• C. densely packed cones, each with its own connection to the optic nerve
• D. the point where the optic nerve leaves the eye

Explanation: At the fovea the cones are crowded together and each has a private line to the brain, so two nearby points of light stimulate two separate pathways and are seen as separate. Rods share connections, which improves sensitivity but destroys detail. The place with no photoreceptors is the blind spot, where the optic nerve leaves, and nothing falling there is seen at all.

4. A receptor is best described as a structure that

• A. detects a change in the environment and converts it into a nerve impulse
• B. carries impulses from the spinal cord to a muscle
• C. produces a hormone in response to a stimulus
• D. connects two sensory neurones together

Explanation: Receptors are transducers: each responds to one kind of stimulus, such as light, sound, pressure or a chemical, and converts that energy into the electrical signal the nervous system can carry. A structure that carries impulses to a muscle is a motor neurone, and a structure that produces a hormone is a gland. The receptor is therefore always the first component of any reflex pathway.

5. In a neurone, impulses are carried away from the cell body by the

• A. dendrites
• B. dendrons
• C. nucleus
• D. axon

Explanation: Each neurone has one long axon that conducts the impulse away towards the next cell, and many short branched dendrites that collect signals and carry them towards the cell body. The direction of travel is what defines the two, not the length. The axon ends in swellings that release neurotransmitter into a synapse or onto a muscle fibre.

6. A myelinated neurone conducts impulses faster than an unmyelinated one because

• A. the impulse jumps from one node of Ranvier to the next
• B. myelin conducts electricity better than cytoplasm
• C. myelinated axons are always much thinner
• D. myelin increases the number of sodium channels along the whole axon

Explanation: Myelin is an insulator, so ions can cross the membrane only at the gaps between Schwann cells, and depolarisation therefore leaps from node to node in what is called saltatory conduction. This can raise conduction speed above 100 metres per second, against a few metres per second in an unmyelinated fibre of the same diameter. Loss of myelin in multiple sclerosis slows or blocks conduction.

7. The resting potential of about minus 70 millivolts across the membrane of a neurone is maintained mainly by

• A. the free diffusion of sodium into the cell
• B. the sodium potassium pump, which moves three sodium ions out for every two potassium ions in
• C. the opening of voltage gated sodium channels
• D. the release of neurotransmitter at the synapse

Explanation: The pump uses ATP to move more positive charge out than it brings in, and since the membrane is far more permeable to potassium, which leaks back out, the inside is left negative relative to the outside. Voltage gated sodium channels are shut at rest and open only when the threshold is reached, which is what produces the action potential rather than the resting state.

8. The rapid depolarisation phase of an action potential is caused by

• A. potassium ions rushing out of the axon
• B. chloride ions entering the axon
• C. sodium ions rushing into the axon through voltage gated channels
• D. the sodium potassium pump reversing direction

Explanation: When the membrane is depolarised to threshold, voltage gated sodium channels open and sodium floods in down both its concentration and its electrical gradient, driving the potential to about plus 40 millivolts. Those channels then close and potassium channels open, so potassium leaves and the membrane repolarises. The pump restores the original ion distribution afterwards but is far too slow to create the spike itself.

9. The all or none law of nerve impulse conduction states that

• A. a stronger stimulus produces a larger action potential
• B. an impulse can travel in either direction along the axon
• C. every stimulus produces an impulse regardless of its strength
• D. any stimulus at or above threshold produces an action potential of the same size

Explanation: Once threshold is reached the sodium channels open fully, so the size of the spike is fixed by the ion gradients and not by how strong the stimulus was. Stimulus intensity is coded instead by the frequency of impulses and by how many neurones are firing. A stimulus below threshold produces no impulse at all, so it is not true that every stimulus produces one.

10. During the refractory period a neurone

• A. cannot be stimulated again, which keeps the impulse travelling in one direction
• B. conducts impulses at double speed
• C. releases neurotransmitter continuously
• D. reverses its resting potential permanently

Explanation: For a brief interval after an action potential the sodium channels are inactivated and cannot reopen, so the region just passed cannot fire again and the impulse can only move forwards. The same period also sets an upper limit on how many impulses a second an axon can carry, which limits how strong a sensation can be coded. The membrane returns fully to its resting state afterwards.