2.5 Homeostasis & Nervous System

Question 1

Define Homeostasis

Answer 1

Homeostasis is the regulation of the internal conditions of a cell or organism, in order to maintain the optimum conditions for function, in response to internal and external changes

Question 2

Homeostasis maintains the optimal conditions for ____________ and all ____________

Answer 2

Homeostasis maintains the optimal conditions for enzyme action and all cell functions

Question 3

What are 3 conditions controlled by homeostasis?

Answer 3

• Body Temperature
• Water levels (in body)
• Blood Glucose concentration

Question 4

What happens if the body temperature is too high?

Answer 4

If the body temperature is too high, enzymes would denature, which would cause many reactions to stop

Question 5

What happens if the body temperature is too low?

Answer 5

If the body temperature is too low, enzyme activity would slow down

Question 6

What happens if the water levels are not controlled?

Answer 6

If the water levels are not controlled, cells could gain or lose water by osmosis, causing the cells to swell or shrink

Question 7

What happens if the blood glucose concentration falls?

Answer 7

If the blood glucose concentration falls, less glucose will be available for respiration so less energy is available for cell activities (like active transport)

Question 8

What are automatic control systems?

Answer 8

Automatic Control Systems is the way the body detects and responds to changes in the external environment

Question 9

Name 2 Automatic Control Systems

Answer 9

• Nervous System
• Endocrine System

Question 10

What do all biological control systems include?

Answer 10

• Receptors
• Coordination Centres
• Effectors

Question 11

What is a stimulus?

Answer 11

A stimulus is a change in the environment

Question 12

What are Receptors?

Answer 12

Receptors are the cells that detect stimuli

Question 13

What are Coordination Centres?

Answer 13

Coordination Centres are the areas that recieve and process the information from the receptors

Question 14

What are Effectors?

Answer 14

Effectors are the muscles or glands that carry out responses to restore the body conditions to optimum levels

Question 15

What does the nervous system enable humans to do

Answer 15

The nervous system enables humans to:
- React to their surroundings
- Coordinate their behaviour

Question 16

What are the 2 parts of the nervous system?

Answer 16

• CNS - Central Nervous System
• PNS - Peripheral Nervous System

Question 17

What does the CNS consist of?

Answer 17

The brain and the spinal cord

Question 18

What does the PNS consist of?

Answer 18

All of the nerves in the body

Question 19

Give 2 adaptations of the structure of the nervous system

Answer 19

• Neurones have a very long axon which makes it faster and more efficient compared to having multiple neurone cells
• The axon is insulated by a fatty myelin sheath which allows electrical impulses to travel quickly and efficiently

Question 20

Explain the pathway of the nervous system

Answer 20

1. When the stimulus is detected, the information from the receptors is sent along the neurones as electrical impulses
2. It travels along the neurones until it reaches the CNS, which is the brain or the spinal cord
3. The CNS coordinates a response and sends it to the effectors, which is a muscle or gland that carries out the response

Question 21

Reflex actions are ____________ and ______

Answer 21

Reflex actions are automatic and rapid

Question 22

Why are reflex actions automatic and rapid?

Answer 22

They do not involve the conscious part of the brain

Question 23

Why do reflex actions happen rapidly?

Answer 23

Reflex actions happen rapidly to help minimise or avoid danger or harm

Question 24

Explain the stages in the Reflex Arc

Answer 24

1. The stimulus is detected by a receptor
2. The sensory neurone sends electrical impulses to the CNS, which is the spinal cord via the relay neurone
3. The relay neurone connects the sensory and motor neurones and is found in the CNS
4. An electrical impulse is carried along the motor neurone to the effector

Question 25

What are synapses?

Answer 25

Synapses are the junctions or gaps between neurones

Question 26

Size of synapses

Answer 26

Synapses are incredibly small

Question 27

What are neurotransmitters?

Answer 27

Neurotransmitters are chemical messengers that are released from the vesicles

Question 28

What do neurotransmitters do?

Answer 28

Neurotransmitters diffuse across the synaptic gap and bind with the receptor molecules on the postsynaptic membrane