Coordination — Nervous and Endocrine Systems — Practice

Question 1

Name the four parts of the human brain and state ONE function of each.

Accepted Answer

Step 1 — Cerebrum.
  Function: THINKING, reasoning, voluntary movement, memory, speech, and sensory perception (sight, hearing, touch).

Step 2 — Cerebellum.
  Function: COORDINATION and BALANCE — ensures voluntary movements are smooth and coordinated. You can ride a bicycle without thinking because of your cerebellum.

Step 3 — Medulla Oblongata.
  Function: Controls INVOLUNTARY (automatic) functions — heartbeat, breathing, blood pressure, swallowing, vomiting. Damage is usually fatal.

Step 4 — Hypothalamus.
  Function: HOMEOSTASIS centre — regulates body temperature, hunger, thirst, and sleep. Also LINKS the nervous and endocrine systems by controlling the pituitary gland.

✦ Answer: Cerebrum (thinking/voluntary), Cerebellum (coordination/balance), Medulla oblongata (involuntary actions), Hypothalamus (homeostasis/links nervous-endocrine).

Question 2

A person accidentally touches a hot iron and immediately withdraws their hand. Explain the reflex arc involved. Why is this response faster than a voluntary action?

Accepted Answer

Step 1 — Identify this as a SPINAL REFLEX.
  This reflex involves the SPINAL CORD — it does NOT wait for the brain.

Step 2 — Trace the five components.
  (1) STIMULUS: Heat from the hot iron.
  (2) RECEPTOR: Pain/heat receptors (thermoreceptors) in the skin detect the stimulus.
  (3) SENSORY NEURON (afferent): Carries the nerve impulse FROM the skin TO the spinal cord.
  (4) RELAY NEURON (interneuron): In the GREY MATTER of the spinal cord — connects sensory to motor neuron.
  (5) MOTOR NEURON (efferent): Carries the impulse FROM the spinal cord TO the hand muscles.
  EFFECTOR: Arm muscles CONTRACT → hand is WITHDRAWN.

Step 3 — Why it is faster than a voluntary action.
  In a voluntary action, the signal travels: hand → spinal cord → BRAIN → spinal cord → hand (long circuit).
  In a reflex, the signal travels: hand → spinal cord → hand (short circuit). This shorter path means LESS TIME for the impulse to travel → FASTER response → LESS INJURY.
  The brain is INFORMED later — you FEEL the pain AFTER pulling away.

✦ Answer: Spinal reflex arc: Stimulus → receptor → sensory neuron → spinal cord relay neuron → motor neuron → effector (muscle contracts). Faster because it bypasses the brain — shorter neural pathway.

Question 3

Tabulate any FOUR endocrine glands with their hormone(s), one main function, and one deficiency disease.

Accepted Answer

Step 1 — Construct the table.

Step 2 — Key note.
  The pituitary is called the 'MASTER GLAND' because it controls other glands through its tropic hormones (TSH → thyroid, ACTH → adrenal, FSH/LH → gonads).

✦ Answer: Table with four glands, hormones, functions, and deficiency diseases as above.

Question 4

Compare the nervous system and endocrine system on four points: speed, type of signal, target, and duration of effect.

Accepted Answer

Step 1 — Prepare the comparison.

Step 2 — Examples.
  Nervous: pulling hand from fire (milliseconds).
  Endocrine: growth during puberty (months to years).

✦ Answer: The nervous system is faster, more specific, and shorter-lasting (like a text message). The endocrine system is slower, more widespread, and longer-lasting (like a newsletter).

Question 5

What is goitre? How can it be prevented?

Accepted Answer

Step 1 — What is goitre?
  GOITRE is the abnormal enlargement of the THYROID GLAND in the neck. It appears as a visible swelling.

Step 2 — Cause.
  Caused by IODINE DEFICIENCY. The thyroid needs iodine to produce THYROXINE (the metabolic hormone). Without sufficient iodine, the thyroid works harder to compensate → it ENLARGES → goitre forms.

Step 3 — Prevention.
  IODISED SALT (sodium iodide or potassium iodide added to common salt). This is the most effective prevention — the Indian government mandated iodised salt for all food purposes.

✦ Answer: Goitre = enlarged thyroid due to iodine deficiency. Prevention = iodised salt.

Question 6

Describe how a nerve impulse travels from one neuron to the next. What is the role of neurotransmitters? Why is the synapse important?

Accepted Answer

Step 1 — Impulse along a single neuron.
  A STIMULUS at the receptor generates an ELECTRICAL IMPULSE (action potential) that travels along the DENDRITE → CELL BODY → AXON.
  The MYELIN SHEATH (made by Schwann cells) insulates the axon and speeds up conduction.

Step 2 — At the synapse.
  When the impulse reaches the AXON TERMINAL, it CANNOT jump the gap (synaptic cleft) electrically. Instead:
  (1) The electrical impulse causes release of CHEMICAL NEUROTRANSMITTERS (e.g., acetylcholine, dopamine) from vesicles into the synaptic cleft.
  (2) Neurotransmitters DIFFUSE across the cleft.
  (3) They BIND to receptors on the NEXT NEURON's dendrite.
  (4) This generates a NEW ELECTRICAL IMPULSE in the next neuron.

Step 3 — Conversion.
  The synapse converts: Electrical → Chemical → Electrical. This is the only way signals pass between neurons.

Step 4 — Importance of synapses.
  (a) Allow ONE-WAY transmission of signals (neurotransmitters are released only from axon terminals, not dendrites).
  (b) Allow INTEGRATION — a neuron receives signals from many neurons; the synapse allows it to 'decide' whether to fire.
  (c) Drugs, alcohol, and many toxins act at synapses — disrupting neurotransmitter release or blocking receptors.

✦ Answer: Impulse travels electrically along the neuron; at the synapse it becomes chemical (neurotransmitters); a new electrical impulse is generated in the next neuron. Synapses ensure one-way transmission and allow signal integration.

Practice — Coordination — Nervous and Endocrine Systems

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