Neural and Chemical Coordination — Practice

Question 1

The part of a neuron that carries impulses away from the cell body is the:
(a) axon (b) dendrite (c) cell body (d) synapse

Accepted Answer

(a) axon.

Dendrites receive impulses and carry them toward the cell body; the single long axon carries impulses away from the cell body toward the next neuron or effector.

Question 2

The resting membrane potential of a neuron is about:
(a) −70 mV (b) +30 mV (c) 0 mV (d) −30 mV

Accepted Answer

(a) −70 mV.

At rest the inside of the axon is about −70 mV relative to the outside, maintained by the Na⁺/K⁺ pump and the membrane's greater permeability to K⁺.

Question 3

For each cycle, the sodium–potassium pump moves:
(a) 3 Na⁺ out and 2 K⁺ in (b) 2 Na⁺ out and 3 K⁺ in (c) 3 Na⁺ in and 2 K⁺ out (d) equal Na⁺ and K⁺

Accepted Answer

(a) 3 Na⁺ out and 2 K⁺ in.

The pump exports 3 Na⁺ for every 2 K⁺ it imports, keeping the outside Na⁺-rich and the inside K⁺-rich and helping maintain the resting potential.

Question 4

The depolarisation (rising) phase of the action potential is caused by the:
(a) inflow of Na⁺ (b) outflow of K⁺ (c) inflow of K⁺ (d) outflow of Na⁺

Accepted Answer

(a) inflow of Na⁺.

A stimulus opens voltage-gated Na⁺ channels; Na⁺ rushes in, reversing the potential from −70 mV toward +30 mV. The subsequent outflow of K⁺ then repolarises the membrane.

Question 5

Release of neurotransmitter at the axon terminal is triggered by the entry of:
(a) Ca²⁺ (b) Na⁺ (c) K⁺ (d) Cl⁻

Accepted Answer

(a) Ca²⁺.

When the impulse reaches the axon terminal, Ca²⁺ enters and causes synaptic vesicles to fuse and release neurotransmitter (e.g. acetylcholine) into the cleft.

Question 6

A nerve impulse crosses a chemical synapse in one direction only because:
(a) transmitter is released pre-synaptically and receptors are post-synaptic (b) the cleft is too wide (c) Na⁺ flows only one way (d) the axon is myelinated

Accepted Answer

(a) transmitter is released pre-synaptically and receptors are post-synaptic.

The neurotransmitter is stored and released only from the pre-synaptic terminal, and receptors lie only on the post-synaptic membrane, making transmission unidirectional.

Question 7

Balance of the body and coordination of muscular movement are controlled by the:
(a) cerebellum (b) cerebrum (c) medulla oblongata (d) hypothalamus

Accepted Answer

(a) cerebellum.

The cerebellum (hindbrain) maintains posture, balance and the fine coordination of movement. The cerebrum handles thought and voluntary action.

Question 8

The vital centres controlling heart rate, breathing and blood pressure lie in the:
(a) medulla oblongata (b) cerebrum (c) cerebellum (d) thalamus

Accepted Answer

(a) medulla oblongata.

The medulla oblongata of the hindbrain contains the cardiac, respiratory and vasomotor centres — the 'vital centres' that keep basic life processes going.

Question 9

The gland called the 'master gland' because it controls several other endocrine glands is the:
(a) pituitary (b) thyroid (c) adrenal (d) pancreas

Accepted Answer

(a) pituitary.

The pituitary secretes TSH, ACTH, FSH and LH that regulate other glands, so it is the master gland — though it is itself directed by the hypothalamus.

Question 10

Excess secretion of growth hormone in an adult causes:
(a) acromegaly (b) gigantism (c) dwarfism (d) cretinism

Accepted Answer

(a) acromegaly.

Excess GH in adulthood, after the long bones have stopped growing, thickens the bones of the hands, feet and face — acromegaly. Excess in childhood causes gigantism; deficiency in childhood causes dwarfism.

Question 11

The element essential for the synthesis of thyroxine is:
(a) iodine (b) iron (c) calcium (d) sodium

Accepted Answer

(a) iodine.

Thyroxine (T₄/T₃) requires iodine. Dietary iodine deficiency prevents its synthesis and enlarges the thyroid, causing goitre — the reason for iodised salt.

Question 12

Which pair correctly matches hormone to its effect on blood calcium?
(a) calcitonin lowers Ca²⁺, PTH raises Ca²⁺ (b) calcitonin raises Ca²⁺, PTH lowers Ca²⁺ (c) both raise Ca²⁺ (d) both lower Ca²⁺

Accepted Answer

(a) calcitonin lowers Ca²⁺, PTH raises Ca²⁺.

Calcitonin from the thyroid lowers blood calcium, while parathormone (PTH) from the parathyroid raises it. They are an antagonistic pair.

Question 13

The 'fight-or-flight' emergency hormone secreted by the adrenal medulla is:
(a) adrenaline (b) cortisol (c) aldosterone (d) insulin

Accepted Answer

(a) adrenaline.

The adrenal medulla secretes adrenaline (and noradrenaline), which raise heart rate, blood pressure and blood glucose to meet emergencies — the fight-or-flight response. Cortisol and aldosterone come from the cortex.

Question 14

Insulin, which lowers blood glucose, is secreted by the:
(a) β-cells of the islets of Langerhans (b) α-cells of the islets (c) adrenal cortex (d) anterior pituitary

Accepted Answer

(a) β-cells of the islets of Langerhans.

The β-cells of the pancreatic islets secrete insulin, which lowers blood glucose; its lack causes diabetes mellitus. The α-cells secrete glucagon, which raises blood glucose — the antagonist of insulin.

Question 15

ADH and oxytocin are:
(a) made by the hypothalamus, stored/released by the posterior pituitary (b) made and released by the posterior pituitary (c) made by the anterior pituitary (d) made by the adrenal cortex

Accepted Answer

(a) made by the hypothalamus, stored/released by the posterior pituitary.

Both hormones are synthesised in the hypothalamus and merely stored and released by the posterior pituitary, which does not manufacture them.

Practice — Neural and Chemical Coordination

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