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A Level (A2) OCR Biology > Unit 5.1- Communication and Homeostasis > Flashcards

Unit 5.1- Communication and Homeostasis Flashcards

1
Q

Cell signalling definition:

A

The way in which cells communicate to each other

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2
Q

Reasons cells signal to each other:

A
  • 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
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3
Q

Features of a good communication system:

A
  • Covers the whole body
  • Enables cells to communicate with each other
  • Enables specific communication
  • Enables both short-term and long-term responses
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4
Q

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

A
  • Neuronal system

- Hormonal system

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5
Q

What is the neuronal system:

A

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

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6
Q

What is the hormonal system?

A

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

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7
Q

Effector definition:

A

A cell, tissue or organ that brings about a response

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8
Q

Homeostasis definition:

A

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

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9
Q

Negative feedback definition:

A

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

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10
Q

Positive feedback definition:

A

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

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11
Q

Sensory receptors definition:

A

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

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12
Q

What does homeostasis control?

A
  • Body temperature
  • Blood glucose concentration
  • Blood salt concentration
  • Water potential of blood
  • Blood pressure
  • Carbon dioxide concentration
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13
Q

What is the mechanism of homeostasis?

A
  • Stimulus
  • Receptor
  • Communication pathway (cell signalling)
  • Effector
  • Response
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14
Q

What are sensory receptors?

A

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
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15
Q

What are communication systems?

A
  • Neuronal or hormonal systems
  • Acts by cell signalling
  • Usually goes via a coordination centre which is usually in the brain
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16
Q

What processes must occur for negative feedback to occur?

A
  • 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
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17
Q

What is the mechanism for positive feedback?

A
  • 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
18
Q

When is positive feedback used?

A
  • Body temperature spiraling downwards

- Dilation of the cervix during pregnancy

19
Q

How does positive feedback cause temperature to spiral downwards?

A
  • Enzymes become less active
  • The exogenic reactions that release heat become slower and release less heat
  • This allows the body to cool further
20
Q

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

A
  • 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
21
Q

Ectotherm definition:

A

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

22
Q

Endotherm definition:

A

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

23
Q

How do ectotherms warm themselves up?

A
  • Move into a sunny area
  • Lie on a warm surface
  • Expose a larger surface area to the sun
24
Q

How do ectotherms cool down?

A
  • Move out of the sun
  • Move underground
  • Reduce the body surface exposed to the sun
25
Q

Advantages of ectothermy:

A
  • 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
26
Q

Disadvantages of ectothermy:

A
  • 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
27
Q

Hypothalamus definition:

A

The part of the brain that coordinates homeostatic responses

28
Q

Behavioural adaptations of endotherms if it’s too hot:

A
  • Go into shade
  • Reduce surface area of body exposed to sun
  • Remain inactive
  • Spead out limbs
  • Lick themselves or spray water over bodies
29
Q

Behavioural adaptations of endotherms if it’s too cold:

A
  • 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
30
Q

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

A
  • Sweat
  • Hairs and fathers lie flat
  • Vasodilation
31
Q

How does the skin respond to warm an endotherm up?

A
  • Less sweat
  • Hairs and feathers stand up
  • Vasocontriction
32
Q

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

A

Panting

33
Q

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

A

Less panting

34
Q

How does the liver respond to cool an endotherm down?

A

Less respiration in liver cells

35
Q

How does the liver respond to warm an endotherm up?

A

Increased respiration in the liver cells

36
Q

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

A

Fewer contractions

37
Q

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

A

Spontaneous muscle contractions (shivering)

38
Q

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

A

Dilation to the extremities so more heat can be lost

39
Q

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

A

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

40
Q

What are the advantages of endothermy?

A
  • 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
41
Q

What are the disadvantages of endothermy?

A
  • 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
42
Q

Where in the brain are the temperature receptors?

A

Hypothalamus

A Level (A2) OCR Biology (13 decks)

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