Component 3.5 - Components Of The Nervous System And Reflex Arc

Question 1

What is a stimulus

Answer 1

A detectable change in the internal or external environment that produces a response in the organism

Question 2

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

Answer 2

• The brain and the spinal cord
• The CNS processes information provided by the stimulus
• Peripheral nervous system - carries impulses from receptors to CNS

Question 3

Name the 7 steps in a reflex arc

Answer 3

1) Stimulus
2) Receptor
3) Sensory neurones
4) Relay neurone in CNS
5) Motor neurone
6) Effector
7) Response

Question 4

What are the pros of a reflex arc?

Answer 4

• They do not involve the decision-making areas of the brain (involuntary)
• Some reflex arcs do not involve a relay neurone (rapid)
• Protective actions that can increase chance of survival (protective)

Question 5

Describe the pupil reflex

Answer 5

• Light (stimulus)
• Photosensitive cells in retina (sensory receptor)
• Optic nerve (sensory neurone)
• Brain (CNS)
• Carries impulse to muscle of iris (motor neurone)
• Iris muscles relax or contract altering the diameter of the pupil (response)

Question 6

What are the two ways information can be taken from a receptor to an effector?

Answer 6

Via the nervous system or as hormones in the blood