Grade 8 Science Assessment 2 – Unit 2 Nervous System

Notes Science Grade 8 Unit 2 Nervous System

Q1: What is the nervous system?

A: The nervous system is an organ system that carries messages between body parts and coordinates body functions.

Q2: What are the two main parts of the nervous system?
A: The Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

Q3: What makes up the Central Nervous System (CNS)?
A: The brain and spinal cord.

Q4: What is the function of the Peripheral Nervous System (PNS)?
A: It connects the CNS to all body parts through a network of nerves.

Q5: What is a neuron?
A: A neuron is the basic structural and functional unit of the nervous system.

Q6: Name the three main parts of a neuron.
A: i. Cell body (contains nucleus) ii. Dendrites (receive messages)

iii. Axon (conducts messages away from the cell body)

Q7: What is a nerve?
A: A bundle of axons enclosed in a common sheath that transmits messages.

Q8: Name the three types of neurons based on function.

· Sensory neurons (carry impulses from sense organs to CNS)

· Motor neurons (carry impulses from CNS to muscles/glands)

· Interneurons (link sensory and motor neurons in CNS)

Q9: Name the three main parts of the brain.

· Forebrain (largest part, includes cerebrum, thalamus, hypothalamus)

· Midbrain (receives sensory information)

· Hindbrain (controls balance, heartbeat, breathing)

Q10: What is the function of the cerebrum?
A: Controls thinking, speech, memory, and voluntary actions.

Q11: What does the cerebellum do?
A: Maintains body balance and controls precise movements.

Q12: What is the role of the medulla oblongata?
A: Controls heartbeat, breathing, and digestion.

Q13: What is the function of the spinal cord?

Connects the brain to the body.
Controls reflex actions.

Q14: What is the Peripheral Nervous System (PNS)?
A: A network of nerves connecting the CNS to the rest of the body.

Q15: How many cranial and spinal nerves are there in humans?

· 12 pairs of cranial nerves (from the brain)

· 31 pairs of spinal nerves (from the spinal cord)

Q16: What are voluntary actions? Give examples.
A: Actions controlled consciously (e.g., walking, talking, writing).

Q17: What are involuntary actions? Give examples.
A: Actions not controlled consciously (e.g., heartbeat, digestion, blinking).

Q18: What is a reflex action?
A: An immediate and involuntary response to a stimulus (e.g., pulling hand away from hot objects).

Q19: What is a reflex arc?
A: The pathway of nerve impulses in a reflex action:
Receptor → Sensory neuron → Spinal cord (interneuron) → Motor neuron → Effector (muscle/gland)

Q20: Why are reflex actions important?
A: They help the body react quickly to avoid danger.

Q21: Why should a motorcyclist wear a helmet?
A: To protect the brain (part of CNS) from injury in case of an accident.

Q22: If a person forgets his name after an accident, which part of the brain is likely damaged?
A: The cerebrum (controls memory and thinking).

Q23: What happens if a nerve connection breaks?
A: Messages cannot be sent properly, leading to loss of movement or sensation.

Q24: How does the nervous system help when you get hurt?
A: It sends pain signals to the brain, and the brain directs the hand to touch the injured area for protection.

Q25: What is the role of the thalamus?
A: It controls sensory functions like relaying signals from sense organs to the cerebrum.

Q26: What does the hypothalamus control?
A: Body temperature, hunger, thirst, and emotions.

Q27: How fast can nerve impulses travel?
A: Up to 150 meters per second (very fast) or as slow as 0.2 meters per second.

Q28: What happens at the terminal ends of an axon?
A: They transmit messages to the next neuron or effector (muscle/gland).

Q29: Why are interneurons important?
A: They process information in the brain/spinal cord and link sensory & motor neurons.

Q30: Which part of the brain controls creativity and music skills?
A: The right cerebral hemisphere.

Q31: What is the function of the pons?
A: Controls sleep, swallowing, taste, and equilibrium (balance).

Q32: Why does the medulla oblongata keep working even during sleep?
A: Because it controls vital functions like breathing and heartbeat, which must never stop.

Q33: How does the spinal cord help in reflexes?
A: It processes quick reflex actions without waiting for the brain (pulling hand from fire).

Q34: What is a stimulus? Give examples.
A: A change in the environment detected by receptors (e.g., heat, cold, sound).

Q35: What are receptors?
A: Special cells/tissues (e.g., skin thermoreceptors) that detect stimuli.

Q36: Name two effectors in the body.
A: Muscles (move body parts) and glands (release hormones/enzymes).

Q37: Why is a reflex action faster than a voluntary action?
A: Because it bypasses the brain and is processed directly in the spinal cord.

Q38: What would happen if reflex actions didn’t exist?
A: The body would react too slowly to dangers (e.g., burning hand before pulling it away).

Q39: Why does a doctor check knee-jerk reflexes with a hammer?
A: To test if the spinal cord and nerves are working properly.

Q40: If a person’s cerebellum is damaged, what problems might they face?
A: Loss of balance, clumsy movements, and difficulty in precise tasks (e.g., writing).