Topic 6—A: Stimuli and Responses- 2. Nervous communication

Question 1

Definition of receptors

Answer 1

• A cell or protein on a cell surface membrane that detects a stimulus

Question 2

Examples of types of receptors

Answer 2

• Baroreceptors- type of receptor that detects changes in blood pressure
  (Receptors are specific to one type of stimulus)

Question 3

Definition of effectors

Answer 3

• A cell that brings about a response to a stimulus, to produce an effect

Question 4

Examples of effectors

Answer 4

• muscle cells
• cells found in glands e.g pancreas

Question 5

How do receptors communicate with effectors?

Answer 5

• via the nervous system or the hormonal system or sometimes using both

Question 6

What is the nervous system made up of?

Answer 6

• A complex network of cells called neurones

Question 7

What are the three main types of neurone?

Answer 7

1. Sensory neurone
2. Motor neurone
3. Relay neurone

Question 8

Sensory neurone

Answer 8

• These transmit electrical impulses from receptors to the central nervous system (brain/spinal cord)

Question 9

Motor neurone

Answer 9

• Transmit electrical impulses from the central nervous system to effectors

Question 10

Relay neurone

Answer 10

• Transmit electrical impulses between sensory neurones and motor neurones

Question 11

Nervous communication

Answer 11

• stimulus is detected by receptor cells and an electrical impulse is sent along a sensory neurone
• When an electrical impulse reaches the end of a neurone chemicals called neurotransmitters take the information across the gap called a synapse to the next neurone where another electrical impulse is generated
• The CNS processes the information and sends impulses along motor neurones to an effector

Question 12

Example

Answer 12

• stimulus: you see a friend waving
• receptors: light receptors (photoreceptors) in your eyes detect the wave. The electrical impulse is carried by a sensory neurone to CNS.
• CNS: processes information and send an electrical impulse along a motor neurone
• effectors: muscle cells are stimulated by the motor neurone
  Response- muscles contract to make your arm wave

Question 13

The nervous response

Answer 13

• when an electrical impulse reaches the end of a neurone chemical messengers called neurotransmitters are secreted directly onto cells e.g muscle cells – so the nervous response is localised
• neurotransmitters are quickly removed once they’ve done their job so the response is short-lived
• Electrical impulses are really fast so the response is usually rapid
• This allows animals to react quickly to stimuli

Question 14

Simple reflexes

Answer 14

• it is a rapid involuntary response to a stimulus
• The pathway of communication goes through the spinal cord but not through conscious parts of the brain so the response happens automatically
• Because you don’t have to spend time deciding on how to respond information travels really fast from receptors to effectors
• they are protective- they help organisms to avoid damage to the body because the response happens so quickly

Question 15

Reflex arc

Answer 15

• The pathway of neurones linking receptors to effectors in a simple reflex is called a reflex ark.
• three neurones are involved
• Sensory
• Relay
• Motor