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Anouk Biology Decks > 5.1.1 - Communication and homeostasis > Flashcards

5.1.1 - Communication and homeostasis Flashcards

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1
Q

What does cell metabolism rely on and what do they need to work efficiently?

A
  • relies on enzymes

- enzymes need particular conditions inside their cells.

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2
Q

What are the set of conditions that all living things need to maintain inside their cells?

A
  • a suitable temp.
  • a suitable pH
  • an aqueous environment that keeps the substrates & products in solution
  • freedom from toxins and excess inhibitors.
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3
Q

What would happen if these conditions were not maintained?

A
  • the cells would become inactive and die.
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4
Q

What must the cells be able to do in multicellular organisms to coordinate their activities and why do they need to?

A
  • cells are specialised & rely on one another
    .˙.
    they need to communicate in order to coordinate their activities.
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5
Q

Define the term cell signalling:

A

the way in which cells communicate with each other.

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6
Q

What is a stimulus?

A

a change in the environment that generates (brings about) a response.

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7
Q

What is a response?

A

a change in an organism resulting from a stimulus.

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8
Q

Give an example of how the environment may change slowly and what is the outcome. (e.g. to the arctic fox)

A
  • seasonal changes
    > cause gradual response.
  • arctic fox has a much thicker white coat in winter
    > greater insulation & camouflage = survival
  • a thinner/brown coat in summer =
    animal does not overheat
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9
Q

Give two examples of how the environment may change more quickly.

A
  • appearance of a predator

- moving from a burrow into the sunlight.

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10
Q

How are the cells and tissues in multicellular organisms protected?

A
  • they are protected by epithelial tissues and organs such as skin or bark
  • in many animals: internal cells & tissues bathed in tissue fluid. This is the ENVIRONMENT OF THE CELLS.
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11
Q

What happens as cells undergo their various metabolic activities?

A
  • they use up substrates and create new products
  • some of these compounds are unwanted or toxic
  • these substances move out of the cells into the tissue fluid

> .˙. the activities of the cells ALTER their own environment.

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12
Q

What happens if carbon dioxide is allowed to build up in the tissue fluid outside cells?

A
  • it will alter tissue fluid pH
  • could disrupt action of enzymes & other proteins
  • accumulation of excess waste or toxins in this internal environment:
    > must act as a STIMULUS to cause removal of waste products so cells can survive!
  • reduced pH of blood stimulates greater breathing activity that expels CD. from body.
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13
Q

How might also happen if there is a lot of build-up of waste products in the tissue fluid?

A
  • the build-up may also act directly on the cells
    > they respond by reducing their activities so less waste is produced

this response may NOT be PRODUCTIVE for whole organism.

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14
Q

What is the composition of the tissue fluid maintained by?

A

the blood.

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15
Q

Outline how the blood maintains the internal environment.

A
  • blood travels around body & transports substances into and out of cells
  • any wastes or toxins collecting in the tissue fluid are likely to enter blood and be carried away
  • to prevent their accumulation in blood they must be removed from body by excretion.
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16
Q

Why is it important that the concentrations of waste products & other substances in blood are monitored closely?

A
  • to make sure body doesn’t remove too much of a useful substance
    > but removes enough waste products to maintain good health and stable environment.
  • ensures cells are provided with the substrates they require!
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17
Q

Why is a multicellular organism more efficient than a single-celled organism and what does this term mean?

A
  • its cells are differentiated

- its cells are specialised to carry out specific functions

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18
Q

What is a tissue?

A

A tissue is group of cells with a similar structure and function, which all work together to carry out a particular job.

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19
Q

What is an organ?

A

a group of different tissues, which all work together to do a particular job.

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20
Q

What is an organ system?

A

a group of different organs, which all work together to do a particular job.

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21
Q

How does the blood benefit from a good communication system?

A
  • the cells that monitor blood may be in a diff. part of body far away from source of waste product
  • may also be far away from tissue or organ specialised to remove the waste from body.
  • a good communication system = needed to ensure that these diff. parts of body work together efficiently.
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22
Q

A good communication system will:

A
  • cover the whole body
  • enable cells to communicate with each other
  • enable specific communication
  • enable rapid communication
  • enable both short-term and long-term responses.
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23
Q

Give a detailed definition of cell signalling.

A
  • process in which one cell will release a chemical that is detected by another cell
  • 2nd cell will respond to this signal
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24
Q

What are the two major systems of communication that work by cell signalling?

A
  • the neuronal system

- the hormonal system

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25
Q

What is the neuronal system?

A
  • network of neurones that signal to each other across synapses
  • cells in the nervous system communicate by secreting chemicals called neurotransmitters, which send signals to ADJACENT cells, such as other nerve cells or muscle cells.
  • neurones can secrete v quickly & enable rapid responses to stimuli that may be changing quickly.
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26
Q

What is the hormonal system?

A
  • a system that uses the blood to transport its signals
  • cells in an endocrine organ release the signal (a hormone) directly into blood
  • hormone is transported throughout body, but only recognised by specific target cells
  • hormones act as signals to DISTANT cells

> enables LONGER-TERM RESPONSES to be coordinated.

27
Q

What does cell signalling involve? (think receptors..)

A
  • cell signalling involves molecules that have a specific shape which is complementary to that of the cell surface receptor
  • essential to enable signals to be specific.
28
Q

What is homeostasis?

A

maintaining a constant internal environment despite changes in external and internal factors.

29
Q

Give 6 examples of aspects that may be maintained by homeostasis.

A
  • body temp.
  • blood glucose conc.
  • blood salt conc.
  • water potential of blood
  • blood pressure
  • CD. conc.
30
Q

What is the standard response pathway?

A

stimulus → receptor → communication pathway (cell signalling) → effector → response

31
Q

Give a brief definition of sensory receptors. Are receptors specific or unspecific?
Give two examples of receptors.

A
  • cells/sensory nerve endings that respond to a stimulus in the internal or external environment of an organism & can create action potentials.
  • receptors are specific - they only detect one particular stimulus e.g. light or pressure.
  • some receptors are cells:
    > e.g. photoreceptors: receptor cells that connect to nervous system
  • some receptors are proteins on cell surface membranes:
    > e.g. glucose receptors: proteins found in the cell membranes of some pancreatic cells.
32
Q

Outline the importance of receptors in the communication systems in the standard response pathway.

A

> sensory receptors e.g. temp. receptors

  • may be on surface of body, e.g. temp. receptors in skin.
    > monitor CHANGES in EXTERNAL ENVIRONMENT.

> other receptors are internal to monitor conditions inside body: e.g. temp. receptors in brain.

  • when one of these receptors detects a change it will be stimulated to send message to an effector.
33
Q

Outline the importance of the communication systems in the standard response pathway.

A
  • communication system e.g. neuronal system or hormonal system. Acts by SIGNALLING BETWEEEN CELLS.
  • used to transmit a message from the receptor cells → effector cells via a coordination centre: usually IN BRAIN.
  • messages from receptor → coordination centre are known as the INPUT.
  • messages sent → effectors are know as the OUTPUT.
34
Q

What is an effector?

A

a cell, tissue or organ that brings about a response (e.g. liver or muscle cells).

35
Q

What is the effect known as feedback?

A
  • effectors respond to output from coordination centre
  • they bring about response that will change bod. conditions
  • these changes will be detected by receptors
  • this will have an effect upon the response pathway & the input will change.
36
Q

What is negative feedback?

A

the mechanism that reverses a change, bringing the system (conditions) back to the optimum.

37
Q

Describe in detail what happens during negative feedback.

A

1) conditions change: receptors detect stimulus & send an input to coordination centre
2) coordination centre sends an output to effectors & effectors respond to this output.
3) effectors bring about a change that reverses the initial change in conditions, system moves closer to optimum & stimulus is reduced,
4) receptors detect the reduction in stimulus & reduce input to the coordination centre

5) output from coordination centre to effectors is also reduced, so effectors reduce their activity.
6) as system gets closer to the optimum, the response is reduced.

38
Q

For negative feedback to work, what 3 processes must occur?

A

1) A change to the internal environment must be detected.
2) The change must be signalled to other cells.
3) There must be an effective response that reverses the change in conditions.

39
Q

Will the internal environment always remain perfectly constant?

A

NO.
A negative feedback system can maintain a reasonably constant set of conditions.
> BUT, there will be some variation around the optimum condition. As long as this variation is not too great, conditions will remain acceptable.

  • conditions in an organism will remain within a relatively narrow range:
    > ‘warm’ enough to allow enzymes to continue functioning efficiently
    > ‘cool’ enough to avoid damage to body’s many other proteins.
40
Q

What is meant by the term exergonic?

A

biochemical reaction that releases energy.

41
Q

What is positive feedback?

A

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

42
Q

True or false: positive feedback is usually productive and helpful.

A

FALSE.

Positive feedback destabilises the system and is usually harmful.

43
Q

Give an example of a situation in which positive feedback is unhelpful.

A

1) below a certain core body temperature enzymes become less active and the exergonic reactions that release heat are slower and release LESS heat.
2) this allows body to cool further & slows the enzyme-controlled reactions even more.

3) this causes body temperature to spiral downwards.
(see diagram you drew).

44
Q

Give an example of a situation in which positive feedback is beneficial.

A

1) at the end of pregnancy to bring about dilation of the cervix.
2) as cervix begins to stretch, this causes the posterior pituitary gland to secrete the hormone oxytocin.
3) oxytocin increases the uterine contractions which stretch the cervix more, which causes secretion of more oxytocin.
4) once the cervix is fully dilated, the baby can be born. The birth ends the production of oxytocin.

45
Q

Give another example of a situation in which positive feedback is beneficial.

A

1) blood clot after an injury.
2) platelets become activated and release a chemical - this triggers more platelets to be activated, and so on.
3) platelets very quickly form a blood clot at the injury site.
4) the process ends with negative feedback, when the body detects the blood clot has been formed.

THE ACTIVITY OF NEURONES ALSO RELIES ON POSITIVE FEEDBACK.

46
Q

What is an ectotherm?

A

an organism that relies on external sources of heat to maintain body temperature.
> (temp. fluctuates with the external temp)

47
Q

What is an endotherm?

A

an organism that uses heat from metabolic reactions to maintain body temperature.
> (controls body temp. within v strict limits)

48
Q

How does body temp. affect the activity of cell processes. (hint: energy and tertiary structure)

A

1) as temp. rises - more kinetic energy - move about more quickly & collide more frequently - essential chemical reactions occur more quickly.
> in cooler conditions - opposite. Chemical reactions slow down.

2) structure of proteins can be affected by increase in body temp. - any change in shape of enzyme’s active site will affect enzyme’s ability to function normally.
> if temp. increases too much, enzymes change shape and their function is lost.

49
Q

How is body temperature decrease an example of positive feedback? Explain in detail.

A
  • some enzymes are v sensitive to temp. change
  • if body temp. drops by 10 degrees, the rate of enzyme-controlled reactions falls by half.
  • many reactions in cells release heat, which can help to maintain the temp., but if the temp. drops and reactions slow down, less heat is released. Allows body to cool further.
  • as body cools, organism is less and less able to function normally.

THE CORE TEMP. IS IMPORTANT FACTOR as all vital organs are found in the centre of bod.

50
Q

Give examples of ectotherms and endotherms.

A

Ectotherms - e.g. reptiles, fish

Endotherms - e.g. mammals, birds

51
Q

How do ectotherms control their body temp.?

A

Ectotherms control their body temp. by changing their behaviour.
> behavioural responses can alter amount of heat exchanged with the environment

> e.g. once they are active: muscle contractions will generate some heat from increased respiration.

52
Q

If ectotherms are not warm enough, they try to absorb more heat from the environment. They may:

A
  • move into a sunny area
  • lie on a warm surface
  • expose a larger surface area to the sun
53
Q

If ectotherms are too hot they try to avoid gaining more heat and try to increase heat loss to the environment. They may:

A
  • move out of sun
  • move underground
  • reduce body surface exposed to sun
54
Q

What are the advantages of ectothermy?

A

They do NOT use up energy to keep warm.
.˙.
> less of their food is used in respiration
> more of the energy & nutrients gained from food can be converted to growth
> need to find less food
> can survive for long periods without food.

55
Q

What are the disadvantages of ectothermy?

A

Less active in cooler temps.
.˙.
> are at risk from predators while cold - unable to escape
> cannot take advantage of food that is available while they are cold.
> they have a variable metabolic rate - generate v little heat themselves.

56
Q

How do endotherms control their body temp?

A

Endotherms can use physiological adaptations & behavioural means to control their body temp.
> their temp. regulation relies on effectors in skin & muscles.

Many PHYSIOLOGICAL adaptations to control body temp. involve skin.
> changes that take place in skin alter amount of heat being lost to environment.
> e.g. directing blood towards or away from skin.

Chemical reactions
> many of these in bod. are exergonic - release energy in the form of heat.
> they can increase respiration in muscles& liver simply to release heat - using up energy intake to stay warm.

57
Q

What are the advantages of endothermy?

A

They can:
> maintain a fairly constant body temp. whatever the temp. externally
> remain active even when external temps. are low. which means they can take advantage fo prey that may be available or escape from potential predators
> inhabit colder parts of the planet

58
Q

What are the disadvantages of endothermy?

A

They:
> use significant part of their energy intake to maintain body temp. in the cold
> need more food
> use for growth a lower proportion of the energy and nutrients gained from food
> may overheat in hot weather.

59
Q

What part of the brain coordinates homeostatic responses?

A

The hypothalamus.

60
Q

How does the hypothalamus control body temp. in mammals?

A

The hypothalamus receives information about temp. from thermoreceptors.

Thermoreceptors in the hypothalamus detect internal temp. (temp. of blood).

The hypothalamus then sends out impulses via the neuronal system to cause different responses that will reverse the change.

61
Q

If the core temp. is too low, what will the hypothalamus do?

A

Will bring about:

  • changes in the skin to reduce heat loss
  • release of heat through extra muscular contraction
  • increased metabolism in order to release more heat from exergonic reactions.
62
Q

What happens if the core temp. rises above the optimum? What is the name of this process/mechanism?

A

The hypothalamus will bring about the opposite changes. (Negative feedback)

63
Q

What is the role of peripheral temp. receptors?

A

Peripheral temp. receptors in the skin monitor the temp. in the extremities.
This info is then fed to thermoregulatory centre in hypothalamus.

  • if centre detects v cold or v hot, brain can initiate behavioural mechanisms for maintaining body temp. e.g. moving into shade.
64
Q

Why are peripheral temp. receptors helpful?

A

They help the hypothalamus to respond more quickly and reduce variation in the core body temp.

Anouk Biology Decks (24 decks)

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