5. Homeostasis and Response (homeostasis, the nervous system, required practical 7)

Question 1

What is homeostasis?

Answer 1

The maintenance of a constant internal environment in order to maintain optimal conditions for enzyme and cellular functions

Question 2

Why does homeostasis occur?

Answer 2

To maintain optimal conditions for enzyme action and all cell functions

Question 3

What does homeostasis control in the human body?

Answer 3

• blood glucose concentration
• body temperature
• water levels

Question 4

What is nervous and hormonal communication involved in?

Answer 4

the automatic control systems, which detect changes and respond to them

Question 5

What 3 components do all control systems have?

Answer 5

• receptors
• coordination centres
• effectors

Question 6

What are receptors?

Answer 6

Cells that detect stimuli

Question 7

What is a stimulus?

Answer 7

changes in the environment

Question 8

What are coordination centres?

Answer 8

Organs that receive and process information from receptors

Question 9

Give 3 examples of a coordination centre?

Answer 9

• brain
• spinal cord
• pancreas

Question 10

What does the nervous system allow for?

Answer 10

Humans to react to their surroundings and coordinate their behaviour

Question 11

What can the response of effectors be?

Answer 11

• muscles contracting
• glands secreting hormones

Question 12

What are reflexes?

Answer 12

automatic and rapid responses to a stimulus, which do not involve the conscious part of the brain

Question 13

Why are reflex actions important?

Answer 13

they aid survival by preventing harm to the body

Question 14

Where does information travel in reflexes?

Answer 14

down a pathway called the reflex arc

Question 15

What is the difference between a reflex pathway and a conscious pathway?

Answer 15

• within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord (an unconscious part of the brain)
• in a conscious pathway, the coordination centre is in the conscious part of the brain

Question 16

What are examples of reflex arcs?

Answer 16

• Pupils getting smaller to avoid damage from bright lights
• Moving your hand from a hot surface to prevent damage

Question 17

What are synapses?

Answer 17

The gaps between two neurones

Question 18

What is a neurotransmitter?

Answer 18

A chemical that diffuses across the synapse

Question 19

How do electrical impulses travel between neurones?

Answer 19

1. When the impulse reaches the end of the first neurone, a chemical is released into the synapse, these chemicals are called neurotransmitters
2. This chemical diffuses across the synapse
3. When the chemical reaches the second neurone, it triggers the impulse to begin again in the next neurone

Question 20

What is reaction time?

Answer 20

How long it takes you to respond to a stimulus

Question 21

How can reaction time be measured?

Answer 21

With a ruler drop test

Question 22

What makes up the CNS?

Answer 22

• brain
• spinal cord

Question 23

What two types of responses are used in body control systems?

Answer 23

nervous and chemical

Question 24

What are effectors?

Answer 24

muscles or glands that bring about responses to stimuli

Question 25

What sequence of events describes how the nervous system works?

Answer 25

stimulus –> receptor –> coordinator –> effector –> response

Question 26

How does a stimulus lead to a response being carried out by the body?

Answer 26

1. stimulus is converted into an electrical impulse by the receptors
2. the electrical impulses passes along sensory neurones to the central nervous system
3. the CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector, which carries out the response

Question 27

Describe how a reflex action occurs via a reflex arc

Answer 27

1. the stimulus is detected by a receptor
2. an electrical impulse passes along a sensory neurone to the spinal cord
3. At a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone
4. The same process occurs at a synapse between a relay neurone and a motor neurone.
5. Impulses are sent along the motor neurone until the effector is reached
6. At the effector, an appropriate response is carried out

Question 28

State what muscles and glands as effectors do?

Answer 28

muscles - contract
glands - secrete hormones