E1 Stimulus and Response

Question 1

Define stimulus

Answer 1

A change in the environment (external or internal) that is detected by a receptor and elicits a response

Question 2

Define response

Answer 2

A change in an organism (an action) resulting from a stimulus

Question 3

Define reflex

Answer 3

A response that is rapid and involuntary (unconscious)

Question 4

Describe the role of receptors in the response of animals to stimuli

Answer 4

Detect stimuli and transform them into electrical nerve impulses

Question 5

Describe the role of sensory neurons in the response of animals to stimuli

Answer 5

Relay the nerve impulse to the central nervous system (via the dorsal root of the spinal cord)

Question 6

Describe the role of relay neurons in the response of animals to stimuli

Answer 6

Transmit nerve impulses within the CNS

Question 7

Describe the role of motor neurons in the response of animals to stimuli

Answer 7

Receive nerve impulses from the CNS (via the ventral root) and relays the signal to an effector

Question 8

Describe the role of effectors in the response of animals to stimuli

Answer 8

Produce a response to the stimulus (can be muscles or glands)

Question 9

Describe the role of synapses in the response of animals to stimuli

Answer 9

The junctions between two nerve cells and transmission of a signal across these junctions require chemical neurotransmitters

Question 10

Explain how hedgehog behaviour has been affected by natural selection

Answer 10

• Hedgehogs exhibit different self-defensive responses to danger across different populations: curing into a ball to expose spines which create a shield for skin body and limbs, or running away
  
  • In areas where there are vehicles and roads, hedgehogs that run away when faced with danger (oncoming vehicles) will be favoured over ones which curl into a ball, as the spines will not protect against oncoming vehicles
  • Thus hedgehogs which run away are selected for by the environment