3.4.1 Control Systems Involve Stimulus and Response

Question 1

What do receptors do?

Answer 1

Detect stimuli

Question 2

What can receptors be?

Answer 2

Cells or proteins on cell surface membranes

Question 3

What are effectors?

Answer 3

Cells that bring about a response to stimulus to produce an effect

Question 4

Give examples of types of effectors cells

Answer 4

Muscle cells and cells found in glands e.g. pancreas

Question 5

How do receptors communicate with effectors?

Answer 5

Via nervous system and/or hormonal system

Question 6

Name 3 types of neurones

Answer 6

1. Sensory neurones
2. Motor neurones
3. Intermediate/relay neurones

Question 7

What do sensory neurones do?

Answer 7

Transmit electrical impulses from receptors to the CNS - the brain and spinal cord

Question 8

What do motor neurones do?

Answer 8

Transmit electrical impulses from CNS to effectors

Question 9

What do relay neurones do?

Answer 9

Transmit electrical impulses between sensory neurones and motor neurones

Question 10

State the 5 stages of a response to a stimulus

Answer 10

Question 11

What the central nervous system (CNS) made up of?

Answer 11

Brain and spinal cord

Question 12

What is the peripheral nervous system (PNS) made up of?

Answer 12

Neurones that connect the CNS to the rest of the body

Question 13

What does the somatic nervous system control?

Answer 13

Conscious activities e.g running and playing video games

Question 14

What does the autonomic nervous system control?

Answer 14

Controls unconscious activities e.g. digestion

Question 15

What does the sympathetic nervous system do?

Answer 15

Gets the body ready for action - ‘flight or fight’ system

Question 16

What does the parasympathetic nervous system do?

Answer 16

Calms the body down - ‘rest and digest’ system

Question 17

What is a reflex?

Answer 17

When body responds to stimulus without making a conscious decision to respond

Question 18

What is a reflex arc?

Answer 18

Pathway of neurones linking receptors to effectors in a reflex

Question 19

Describe the simple reflex arc for a hand-withdrawal response to heat

Answer 19

1. Thermoreceptors in skin detect heat stimulus
2. Sensory neurone carries impulses to relay neurone
3. Relay neurone connects to motor neurone
4. Motor neurone sends impulses to effector
5. Muscle contracts to withdraw your hand and stop it being damaged

Question 20

What does it mean if there’s a relay neurone involved in a simple reflex arc?

Answer 20

It’s possible to override the reflex

e.g. your brain could tell your hand to withstand the heat

Question 21

Explain how nervous communication is localised

Answer 21

When electrical impulse reaches end of neurone = neurotransmitters are secreted directly onto target cells

Question 22

Explain how nervous communication is short-lived

Answer 22

Neurotransmitters are quickly removed once they’ve done their job

Question 23

State the 2 types of responses that simple mobile organisms have to keep them in a favourable environment

Answer 23

• Tactic (taxes)
• Kinetic (kineses)

Question 24

Define taxes

Answer 24

Organisms move towards or away from a directional stimulus e.g. light

Question 25

Define kineses

Answer 25

Organisms’ movement is affected by non-directional stimulus e.g. humidity

Question 26

Give an example of taxes

Answer 26

• e.g. woodlice show tactic response to light (phototaxis)
• Move away from light source
• Helps them to survive ∵ it keeps them concealed under stones during the day (where they’re safe from predators) & keeps them in damp conditions (reduces water loss)

Question 27

Give an example of kineses

Answer 27

• e.g. woodlice show kinetic response to humidity
• High humidity = move slowly and turn less often = so they stay where they are
• Air gets drier = move faster and turn more often = move into new area
• Response increases chance woodlouse will move to area with higher humidity
• Improves survival chances of organisms = reduces their water loss & keeps them concealed

Question 28

Explain the importance of relfex actions (3)

Answer 28

• Automatic / involuntary
• Prevents injury
• Role in homeostasis