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OCR A BIOLOGY > 5.1 Communication and homeostasis > Flashcards

5.1 Communication and homeostasis Flashcards

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1
Q

Define stimulus.

A

An environmental change.

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2
Q

Define response.

A

The way the organism changes its behaviour or physiology in response to a stimulus.

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3
Q

Define cell signalling.

A

The way in which S communicate with each other.

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4
Q

What’s an example of the external environment?

A

What is surrounding you such as air, water, or soil

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5
Q

What’s an example of an internal environment?

A

The tissue fluid surrounding cells.

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6
Q

What are the two systems used in cell signalling?

A
  1. nervous system
  2. endocrine system
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7
Q

What is the nervous system

A

An interconnected network of neurons that signal across synapses resulting in very quick, short term responses.

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8
Q

What is the endocrine system?

A

The transport of hormonal signals through the blood resulting in long-term specific responses.

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9
Q

Why do organisms need communication systems?

A

To maintain specific conditions for Enzymes in metabolic reactions to work efficiently.

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10
Q

Define Effector.

A

A cell tissue or organ that brings about a response.

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11
Q

Define homeostasis.

A

The maintaining of a constant internal environment, despite changes in external and internal factors

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12
Q

Define negative feedback.

A

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

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13
Q

Define positive feedback.

A

The mechanism that increases the change at taking the system further away from the optimum.

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14
Q

Define sensory receptors

A

cells or sensory nerve endings that respond to a stimulus.

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15
Q

What aspects are maintained by homeostasis?

A
  • Body temperature
  • body glucose concentration
  • Blood salt concentration
  • Blood water potential
  • blood pressure
  • Carbon dioxide concentration.
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16
Q

What specialised structures are required for the response pathway?

A
  • Sensory receptors
  • a communication system - effector cells
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17
Q

Outline the response pathway.

A

Stimulus –> receptor –> cell signalling –> effector
–> response.

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18
Q

What are examples of what negative feedback controls?

A
  • Temperature
  • blood glucose concentrations
  • water levels.
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19
Q

What are examples of thermoreceptors?

A

They could be found in the skin as an external thermoreceptor or in the brain as an internal thermoreceptor.

20
Q

Outline the process of negative feedback.

A
  1. Conditions move away from the optimum
  2. A change to the internal environment is detected by a receptor.
  3. The change is then signalled to other cells using a communication system.
  4. The effector carries out an effective response to reverse the change and bring the conditions back to optimum.
21
Q

What are examples of positive feedback?

A
  • dilation of the cervix at the end of pregnancy,
  • blood clots forming
  • Temperature continuing to drop.
22
Q

Outline the process of positive feedback.

A
  1. Change away from optimum
  2. receptor detects for change
  3. The communication system informs the effector.
  4. The effector reacts to increase the change.
23
Q

Define ectotherm.

A

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

24
Q

Define endotherm.

A

An organism that uses heat from metabolic reactions to maintain body temperature within strict limits.

25
Q

What are examples of ectotherms?

A
  • Lizard
  • Snake
  • Locust
  • Horned Lizard
  • Bees.
26
Q

What are the disadvantages of being an ectotherm?

A
  • At risk from predators while cold
  • can’t adapt to environmental changes.
27
Q

What are the advantages of being an ectotherm.

A

Less energy is used to regulate body temperature, so more can be used in metabolic reactions. This means they can survive longer without food so need to find less food. More energy and nutrients can be converted into growth.

28
Q

What may ectotherms do if they are too cold?

A
  • Bask in the sun
  • lie on a warm surface
  • Expose a larger surface area to the sun
  • At night, they may move underground because the sand is warmer.
29
Q

What may ectotherms do if they are too hot?

A
  • Move out of the sun.
  • Move underground.
  • Reduce body surface area exposed to the sun.
30
Q

What may bees do to control body temperature when in the swarm?

A

The bees that are too cold may move to the centre of the swarm. And then when they are too hot, they move to the outside.
They can also adjust air flows to help cool a swarm at.

31
Q

Why might cellular activity decrease if core body temperature gets too high?

A

Enzymes work best at their optimum temperature. Beyond this point, the enzymes will begin to denature. So we can no longer catalyse metabolic reactions as the active site changes shape, so it is no longer complementary to the substrate.

32
Q

What is the hypothalamus?

A

The part of the brain that coordinates homeostatic responses.

33
Q

what organs are involved in regulating body temperature.

A
  • skin
  • skeletal muscles
  • liver
  • gas exchange system
  • blood vessels.
34
Q

What is an exergonic reaction?

A

A reaction that releases energy.

35
Q

What is an example of an exergonic reaction?

A

Respiration.

36
Q

what Would be advantages of being an endotherm?

A
  • Body temperature remains fairly constant
  • remain active when it is cold.
  • Inhabit colder climates.
37
Q

what are disadvantages of being an endotherm.

A
  • More energy is used to maintain body temperature
  • less energy and nutrients for growth.
  • require more food.
38
Q

How is the temperature regulation controlled?

A
  1. Temperature receptors in the hypothalamus detect a change
  2. hypothalamus sends out impulses to cause a response in order to reverse a change
  3. nervous system is used for quick responses
  4. Endocrine system for long term responses.
39
Q

What are the muscles that control blood flow through the capillary?

A

Sphincter muscles.

40
Q

How is sweating used to cool down if you are too hot?

A

Water has a high specific latent heat of vaporisation. This means that it can use the heat from the blood to help it evaporate. So small amounts of sweat will use large amounts of energy.

41
Q

What happens during vasoconstriction?

A

The sphincter muscles contract, which reduces the blood flow to the extremities, so that less heat is lost.

42
Q

What happens during vasodilation?

A

The sphincter muscles relax, which increases the blood flow to the extremities. So more heat can be lost.

43
Q

Define piloerection.

A

Hairs standing up when you are too cold

44
Q

How to shivering help to generate heat when you are cold

A

Shivering means that there is increased muscle contraction so muuscle cells respire more, which is an exergonic reaction, so more heat is released.

45
Q

Why do hairs on the skin lie flat when you are too hot?

A

To reduce insulation so the air is not trapped against the skin.

46
Q

Why it has on the skin stand up when you are too cold.

A

It traps a layer of air against the skin, which acts as insulation as it is warmed.

47
Q
A

OCR A BIOLOGY (17 decks)

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