Chapter 15 — Nervous System: Multiple Choice Questions
1. The structural and functional unit of the nervous system is ______.
Answer
(a) Brain (b) Spinal cord (c) Neuron (d) Nerve
✅ Answer: (c) Neuron
ExplanationThe neuron (nerve cell) is the basic structural and functional unit of the nervous system. A neuron consists of: cell body (soma), dendrites (receive impulses from other neurons), and axon (transmits impulses to other neurons or effectors). Neurons communicate via synapses.
2. The part of the brain that controls balance and coordination is ______.
Answer
(a) Cerebrum (b) Cerebellum (c) Medulla oblongata (d) Hypothalamus
✅ Answer: (b) Cerebellum
Explanation
- Cerebrum: Thinking, memory, voluntary movement, speech, consciousness (largest part)
- Cerebellum: Balance, coordination of voluntary movements (smaller, at back)
- Medulla oblongata: Controls involuntary actions — breathing, heartbeat, swallowing
- Hypothalamus: Temperature regulation, hunger, thirst, hormones
3. A reflex arc involves which of the following in order?
Answer
(a) Effector → Sensory neuron → Spinal cord → Motor neuron → Receptor (b) Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector (c) Motor neuron → Receptor → Brain → Sensory neuron → Effector (d) Brain → Sensory neuron → Receptor → Motor neuron → Effector
✅ Answer: (b) Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector
ExplanationReflex arc path: Receptor (detects stimulus) → Sensory neuron (afferent) → Spinal cord (relay neuron) → Motor neuron (efferent) → Effector (muscle/gland responds)
Note: The spinal cord, not the brain, coordinates reflex actions (for speed).
4. Involuntary actions like heartbeat are controlled by ______.
Answer
(a) Cerebrum (b) Cerebellum (c) Medulla oblongata (d) Pons
✅ Answer: (c) Medulla oblongata
ExplanationThe medulla oblongata (brainstem) controls vital involuntary functions:
- Heartbeat rate
- Breathing rate
- Blood pressure
- Swallowing, vomiting, sneezing, coughing
Damage to the medulla oblongata is life-threatening because it controls these critical functions.
5. The junction between two neurons is called ______.
Answer
(a) Axon (b) Dendrite (c) Synapse (d) Node of Ranvier
✅ Answer: (c) Synapse
ExplanationA synapse is the junction between the axon terminal of one neuron and the dendrite of the next. Signals are transmitted across the synaptic gap by neurotransmitters (chemical messengers like acetylcholine, dopamine, serotonin). This chemical transmission allows neural circuits to be regulated.
6. The myelin sheath around axons is produced by ______.
Answer
(a) Schwann cells (b) Neurons (c) Astrocytes (d) Microglia
✅ Answer: (a) Schwann cells
ExplanationSchwann cells (in PNS) wrap around the axon to form the myelin sheath — a fatty insulating layer that speeds up impulse conduction. Gaps in the myelin sheath are called Nodes of Ranvier. In the CNS, oligodendrocytes form the myelin sheath.
7. Which part of the nervous system controls fight-or-flight response?
Answer
(a) Somatic nervous system (b) Parasympathetic nervous system (c) Sympathetic nervous system (d) Enteric nervous system
✅ Answer: (c) Sympathetic nervous system
ExplanationThe sympathetic nervous system prepares the body for emergency/stress ("fight or flight"): increases heart rate, dilates pupils, increases blood flow to muscles, releases adrenaline. The parasympathetic system calms the body ("rest and digest"): slows heart rate, promotes digestion.
8. The cranial nerves arise from ______.
Answer
(a) Spinal cord (b) Brain (c) Both brain and spinal cord (d) Peripheral ganglia
✅ Answer: (b) Brain
ExplanationHumans have 12 pairs of cranial nerves arising directly from the brain (especially the brainstem). They innervate structures of the head, neck, and some thoracic/abdominal organs. 31 pairs of spinal nerves arise from the spinal cord.
9. The large outer part of the brain responsible for higher mental functions is the ______.
Answer
(a) Cerebellum (b) Cerebrum (c) Thalamus (d) Corpus callosum
✅ Answer: (b) Cerebrum
ExplanationThe cerebrum is the largest part of the brain (~85% of brain mass). Its surface (cerebral cortex) has folds (gyri) and grooves (sulci) that increase surface area. It controls: thinking, reasoning, memory, language, voluntary movement, and sensory perception. Divided into left and right hemispheres.
10. Adrenaline is secreted in response to ______.
Answer
(a) Normal body temperature (b) Sleep (c) Fear, stress, or excitement (d) Eating a meal
✅ Answer: (c) Fear, stress, or excitement
ExplanationThe adrenal medulla releases adrenaline (epinephrine) in response to stress, fear, or excitement (triggered by sympathetic nervous system). Adrenaline causes: increased heart rate, rapid breathing, increased blood sugar, dilated pupils — prepares body for "fight or flight."
Quick Revision — Brain Parts and Functions
| Part | Function |
|---|
| Cerebrum | Thinking, memory, voluntary movement, speech |
| Cerebellum | Balance, coordination |
| Medulla oblongata | Heartbeat, breathing, involuntary functions |
| Hypothalamus | Temperature, hunger, thirst, hormone control |
| Thalamus | Relay station for sensory information |
| Pons | Connects cerebrum and cerebellum, controls breathing rhythm |
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