Unit 5.1- Communication and Homeostasis

Question 1

Cell signalling definition:

Answer 1

The way in which cells communicate to each other

Question 2

Reasons cells signal to each other:

Answer 2

• To keep a suitable temperature and PH
• To keep an aqueous environment that keeps the substrates and products in solution
• To keep freedom from toxins and excess inhibitors
• Coordination of different organs

Question 3

Features of a good communication system:

Answer 3

• Covers the whole body
• Enables cells to communicate with each other
• Enables specific communication
• Enables both short-term and long-term responses

Question 4

What are the major communication systems that work by cell signalling in the human body?

Answer 4

• Neuronal system

- Hormonal system

Question 5

What is the neuronal system:

Answer 5

Interconnected network of neurones that signal to each other across synapse junctions. The neurones can conduct a signal very quickly and enable rapid responses to stimuli that may be changing quickly

Question 6

What is the hormonal system?

Answer 6

Uses the blood to transport signals. Cells in an endocrine organ release the hormone directly into the blood. The hormone is transported all over the body but only recognised by certain target cells. The hormonal system allows longer-term responses to be coordinated

Question 7

Effector definition:

Answer 7

A cell, tissue or organ that brings about a response

Question 8

Homeostasis definition:

Answer 8

Maintaining a constant internal environment despite changes in external and internal factors

Question 9

Negative feedback definition:

Answer 9

The mechanism that reverses a change bringing the system back to the optimum

Question 10

Positive feedback definition:

Answer 10

The mechanism that increases a change, taking the system further away from the optimum

Question 11

Sensory receptors definition:

Answer 11

Cells/ sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials

Question 12

What does homeostasis control?

Answer 12

• Body temperature
• Blood glucose concentration
• Blood salt concentration
• Water potential of blood
• Blood pressure
• Carbon dioxide concentration

Question 13

What is the mechanism of homeostasis?

Answer 13

• Stimulus
• Receptor
• Communication pathway (cell signalling)
• Effector
• Response

Question 14

What are sensory receptors?

Answer 14

Monitor changes in the environment

• Sensory receptors on the surface of the body monitor changes in the external environment
• Sensory receptors inside the body e.g. the brain detect internal changes

Question 15

What are communication systems?

Answer 15

• Neuronal or hormonal systems
• Acts by cell signalling
• Usually goes via a coordination centre which is usually in the brain

Question 16

What processes must occur for negative feedback to occur?

Answer 16

• A change in the internal environment must be detected
• The change must be signalled to other cells
• Effective response that reverses the change in conditions

Question 17

What is the mechanism for positive feedback?

Answer 17

• Optimum condition
• Change away from optimum
• Receptor detects change
• Communication system informs effector
• Effector reacts to increase change further
• Changes away from optimum further and cycle repeats

Question 18

When is positive feedback used?

Answer 18

• Body temperature spiraling downwards

- Dilation of the cervix during pregnancy

Question 19

How does positive feedback cause temperature to spiral downwards?

Answer 19

• Enzymes become less active
• The exogenic reactions that release heat become slower and release less heat
• This allows the body to cool further

Question 20

How does positive feedback cause the cervix to dilate in pregnancy?

Answer 20

• As the cervix begins to stretch, oxytocin is secreated
• This increases the contractions which allows the cervix to stretch more
• This causes secretion of more oxytocin
• The birth ends the production of oxytocin

Question 21

Ectotherm definition:

Answer 21

An organism that relies on external sources of heat to maintain body temperature

Question 22

Endotherm definition:

Answer 22

-An organism that uses heat from metabolic reactions to maintain body temperature

Question 23

How do ectotherms warm themselves up?

Answer 23

• Move into a sunny area
• Lie on a warm surface
• Expose a larger surface area to the sun

Question 24

How do ectotherms cool down?

Answer 24

• Move out of the sun
• Move underground
• Reduce the body surface exposed to the sun

Question 25

Advantages of ectothermy:

Answer 25

• Less energy from food needed for respiration
• More energy and nutrients gained from food can be converted to growth
• Don’t need to find as much food
• Can survive for long periods of time without food

Question 26

Disadvantages of ectothermy:

Answer 26

• Less active in cooler temperatures
• Therefore at risk from predators in cooler temperatures
• Cannot take advantage of food available to them while they are cold

Question 27

Hypothalamus definition:

Answer 27

The part of the brain that coordinates homeostatic responses

Question 28

Behavioural adaptations of endotherms if it’s too hot:

Answer 28

• Go into shade
• Reduce surface area of body exposed to sun
• Remain inactive
• Spead out limbs
• Lick themselves or spray water over bodies

Question 29

Behavioural adaptations of endotherms if it’s too cold:

Answer 29

• Lie in sun
• Increase surface area of body exposed to sun
• Move about to generate heat
• Roll into a ball o reduce surface area and heat loss
• Remain dry

Question 30

-How does the skin respond to cool an endotherm down:

Answer 30

• Sweat
• Hairs and fathers lie flat
• Vasodilation

Question 31

How does the skin respond to warm an endotherm up?

Answer 31

• Less sweat
• Hairs and feathers stand up
• Vasocontriction

Question 32

How does the gaseous exchange system respond to cool down an endotherm?

Answer 32

Panting

Question 33

How does the gaseous exchange system respond to warm an ectotherm up?

Answer 33

Less panting

Question 34

How does the liver respond to cool an endotherm down?

Answer 34

Less respiration in liver cells

Question 35

How does the liver respond to warm an endotherm up?

Answer 35

Increased respiration in the liver cells

Question 36

How do the skeletal muscles respond to cool an endotherm down?

Answer 36

Fewer contractions

Question 37

How do the skeletal muscles respond to warm an endotherm up?

Answer 37

Spontaneous muscle contractions (shivering)

Question 38

How do the blood vessels respond to cool an endotherm down:

Answer 38

Dilation to the extremities so more heat can be lost

Question 39

How do the blood vessels respond to warm an endotherm up?

Answer 39

Constricted blood flow to the extremities. This can lead to frostbit in extreme conditions

Question 40

What are the advantages of endothermy?

Answer 40

• Maintain a fairly constant temperature whatever the temperature externally
• Remain active even when temperatures are low- they can take advantage of prey in cold temperatures
• Inhabit colder parts of the planet

Question 41

What are the disadvantages of endothermy?

Answer 41

• Use a significant part of their energy intake to maintain body temperature in the cold
• Need more food
• Use a lower proportion of energy and nutrients for growth
• May overheat in hot weather

Question 42

Where in the brain are the temperature receptors?

Answer 42

Hypothalamus