B10 - The Human Nervous System

Question 1

What is a stimulus?

Answer 1

A change in the environment.

Question 2

Explain how negative feedback helps to maintain a stable internal environment.

Answer 2

=> RECEPTOR detects STIMULUS - level = too high/low
=> COORDINATION CENTRE receives info; coordinates a response
=> EFFECTOR produces response; counteracts change; restores optimum level - level decreases/increases

Question 3

What makes up the the central nervous system and what does it do?

Answer 3

• CNS = brain and spinal cord

- CNS is a coordination centre (recieves info. from receptors, coordinates response for effectors)

Question 4

What is a synapse?

Answer 4

• The connection between two neurones.

- Chemicals released to transfer nerve signal across gap

Question 5

What is the purpose of a reflex action?

Answer 5

Reflexes are rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain - they can reduce the chance of being injured.

Question 6

What is a reaction time?

Answer 6

The time it takes to respond to a stimulus.

Question 7

Give one thing the cerebral cortex is responsible for

Answer 7

• Consciousness
• Intelligence
• Memory
• Language

Question 8

Give three methods used by scientists to study the brain?

Answer 8

• Studying patients with brain damage
• Electrically stimulating the brain
• MRI scans

Question 9

Explain the role of the cornea

Answer 9

• Transparent outer layer found at the front of the eye

- Refracts light into the eye

Question 10

Explain the role of the iris

Answer 10

• Contains muscles that allow it to control the diameter of the pupil
• Controls how much light enters eye

Question 11

Explain the role of the lens

Answer 11

Focuses light into the retina

Question 12

Describe the iris reflex. Why is it needed?

Answer 12

Very bright light can damage the retina.
=> Light receptors in eye detect very bright light
=> reflex triggered that makes pupil smaller
=> CIRCULAR MUSCLES contract
=> RADIAL MUSCLES relax
(for dim light the opposite happens)

Question 13

What is the medical term for short sightedness? Explain this condition.

Answer 13

• Myopia
  (unable to focus on distant objects)
  => LENS is too strong - refracts light too much
  => Image brought into focus in front of retina
  => CONCAVE (curves inwards) lens corrects this
  (long sightedness - hyperopia - is the opposite)

Question 14

What is the reflex arc?

Answer 14

stimulus
- Receptor
- Sensory neurone
(synapse)
- Relay neurone (CNS)
(synapse)
- Motor neurone
- Effector
response