Human nervous system 5.2

Question 1

What is the function of the nervous system?

Answer 1

The nervous system allows the body to react to its surroundings and coordinate and appropriate response

Question 2

How does a stimulus lead to a response being carried out by the body?

Answer 2

• Stimulus is converted into an electrical impulse by the receptors
• The electrical impulse passes along sensory neurones to the central nervous system (CNS)
• The CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector, which carries out the response

Question 3

What sequence of events describes how the nervous system works?

Answer 3

Stimulus → receptor → coordinator → effector → response

Question 4

What is a reflex action?

Answer 4

A reflex action is an automatic and rapid response which does not involve any conscious input from the brain

Question 5

Why are reflex actions important?

Answer 5

Reflex actions aid survival by preventing harm to the body

Question 6

Describe how a reflex action occurs via a reflex arc

Answer 6

• The stimulus is detected by a receptor
• An electrical impulse passes along a sensory neurone to the spinal cord (part of the CNS)
• At a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone
• The same process occurs at a synapse between a relay neurone and a motor neurone
• At the effector, an appropriate response is carried out

Question 7

What is the difference between a reflex pathway and a conscious pathway?

Answer 7

Within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/unconscious parts of the brain. In a conscious pathway, the coordination centre is in the conscious part of the brain

Question 8

How is temperature monitored by the body?

Answer 8

Thermoregulatory centre has receptors sensitive to blood temperature
- Skin has receptors sensitive to skin temperature - sends impulses to thermoregulatory centre

Question 9

What physiological changes occur when the body temperature is too high?

Answer 9

• Vasodilation - blood vessels near the surface of the skin dilate - more heat is radiated away
• Sweating - evaporation of water takes away heat energy from the surface of the skin

Question 10

What physiological changes occur when the body temperature is too low?

Answer 10

• Vasoconstriction - blood vessels near the surface of the skin constrict - less heat radiated away
• Shivering - respiration allows muscles to contract. It is an exothermic process, so heat energy is released.
• Sweating stops