Questions: The Nervous System

Question 1

What is the correct path of a nerve signal when you touch something hot?

• A. Brain → spinal cord → hand
• B. Hand → sensory nerve → brain → motor nerve → muscles
• C. Muscles → brain → sensory nerve → hand
• D. Brain → muscles → sensory nerve → spinal cord

Answer: (B)

When you touch something hot, sensory receptors in your hand detect the heat and send a signal along sensory nerves to the spinal cord and brain. The brain interprets the signal as pain and sends a response signal along motor nerves to your arm muscles, which pull your hand away. The signal path goes: stimulus → sensory nerve → brain → motor nerve → response.

Question 2

The spinal cord's mainly job is to support the backbone.

• T. True
• F. False

Answer: False

The spinal cord is a bundle of nerves, not a bone. Its job is to carry nerve signals between the brain and the rest of the body. It also coordinates some reflexes on its own — the knee-jerk reflex, for example, is processed in the spinal cord without the signal ever reaching the brain. The backbone (spine) protects the spinal cord, but they are different structures.

Question 3

Explain what a reflex is and why it is faster than a normal response.

Model answer: A reflex is an automatic, rapid response to a stimulus that does not require the brain to make a decision. It is faster because the signal travels only to the spinal cord and back, skipping the brain. For example, when a doctor taps your knee, the signal goes to the spinal cord, which immediately sends a signal back to the leg muscle to kick — no thinking required.

Reflexes are a survival mechanism — they protect the body from harm before the brain even registers what happened. The shorter signal path (sensory nerve → spinal cord → motor nerve, bypassing the brain) is why reflexes are faster than deliberate responses.