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B5 > Communication and homeostasis > Flashcards

Communication and homeostasis Flashcards

1
Q

What conditions need to be maintained inside cells ?

A
  • temperature
  • pH
  • aq environment that keeps substrates and products in solution
  • freedom from toxins and excess inhibitors
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2
Q

Features of a good communication system

A
  • covers the whole body
  • enables cells to communicate with each other
  • enable specific and rapid communication
  • enable both short-term and long-term responses
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3
Q

What’s cell signalling?

A

communication between cells

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4
Q

2 major systems of communication that work by cell signalling

A
  • hormonal system
  • neuronal system
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5
Q

Define homeostasis

A

MAINTAINING A CONSTANT INTERNAL ENVIRONMENT despite changes in internal or external factors

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6
Q

Define negative feedback

A

MECHANISM that reverses a change, bringing system back to the optimum

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7
Q

Define positive feedback

A

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

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8
Q

What’s a sensory receptor?

A

cells or sensory nerve endings that respond to a stimulus in internal/external environment of organism and creates action potentials

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9
Q

aspects maintained by homeostasis

A
  • body temperature
  • blood glucose conc
  • blood salt conc
  • water potential of blood
  • blood pressure
  • carbon dioxide conc
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10
Q

mechanism of homeostasis

A

stimulus –> receptor (sensory cell) –> cell signalling –> effector–> response

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11
Q

Where are thermoreceptors?

A
  • skin
  • brain
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12
Q

Will conditions remain perfectly constant as a result of negative feedback?

A

No. there will be fluctuation around the optimum as it may take time to respond and the response may overshoot slightly

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13
Q

What’s an endotherm?

A

organism that uses heat from metabolic reactions to maintain body temperature

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14
Q

What’s an ectotherm?

A

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

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15
Q

How do ectotherms try to absorb more heat when they’re not warm enough?

A
  • move into sunny area
  • lie on warm surface
  • expose a larger surface area to the sun
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16
Q

How do ectotherms avoid gaining more heat when they’re too hot?

A
  • move out of the sun
  • move underground
  • reduce body surface exposed to the sun
17
Q

Advantages of ectothermy?

A
  • less of their food is used in respiration
  • more energy and nutrients from food converted to growth
  • need to find less food
  • can survive long periods of time without food
18
Q

Disadvantages of ectothermy?

A
  • less active in cooler temperatures so increased risk of predation as they’re unable to escape
  • can’t take advantage of food available while they’re cold
19
Q

What’s the hypothalamus?

A
  • the part of the brain that coordinates homeostatic responses
  • detects change in core temperature
20
Q

What are exergonic reactions?

A

those that release energy in the form of heat

21
Q

How does the skin respond when the body is too hot?

A
  • vasodilation of capillaries directs blood to skin surface so more heat radiated from body
  • sweat released, heat from blood used to evaporate it.
  • hairs and feathers lie flat to reduce insulation and allow greater heat loss
22
Q

How does the skin respond when the body is too cold?

A
  • vasoconstriction of capillaries, blood diverted away from skin surface, less heat is lost
  • less sweat secreted, less evaporation, less heat loss
  • hairs and feathers stand erect to trap air, which insulates body
23
Q

How does the gaseous exchange system respond when body is too hot?

A
  • panting increases evaporation of water from surface of lungs and airways using heat from blood.
24
Q

How does the gaseous exchange system respond when body is too cold?

A
  • less panting so less heat lost.
25
Q

How does the liver respond when the body is too hot?

A
  • less respiration, less heat released
26
Q

How does the liver respond when the body is too cold?

A
  • increased respiration in hepatocytes, more energy from food converted to heat
27
Q

How do skeletal muscles respond when the body is too hot?

A
  • fewer contractions so less heat released
28
Q

How do skeletal muscles respond when the body is too cold?

A
  • shivering, releasing heat
29
Q

How do blood vessels respond when the body is too hot?

A

dilation to direct blood to extremities so more heat lost

30
Q

How do blood vessels respond when the body is too cold?

A

constriction to limit blood flow to extremities so blood is not cooled to much, may lead to frostbite in extreme cases

31
Q

behaviours of endotherms if they’re too hot?

A
  • hide away from sun in the shade
  • orientate body to reduce SA exposed to sun
  • remain inactive and spread limbs for greater heat loss
  • wet skin to use evaporation to cool body
32
Q

behaviours of endotherms if they’re too cold?

A
  • lie in the sun
  • orientate body towards sun to increase SA exposed
  • become active to generate heat in muscles
  • remain dry
33
Q

Advantages of endothermy

A
  • maintain fairly constant body temp regardless of external temperature
  • remain active even at low temps so can escape from predators and hunt
  • INHABIT COLDER PARTS OF THE PLANET
34
Q

Disadvantages of endothermy

A
  • use a lot of energy intake to maintain body temp in the cold so a lower proportion of energy and nutrients used for growth
  • need more food
  • overheat in hot weather
35
Q

How is the control of temperature regulated?

A
  • temperature receptors (thermoregulatory centre) in hypothalamus detect change
  • hypothalamus sends impulses. Output can be transmitted by the neuronal system for quick responses or hormonal system for longer term responses
36
Q

What does the hypothalamus cause when body temperature is too low?

A
  • changes to skin to reduce heat loss (vasoconstriction)
  • release of heat through extra muscle contraction
  • increased metabolism to release more energy from exergonic reactions
37
Q

What’s the role of peripheral temperature receptors?

A
  • peripheral temperature receptors in skin monitor temperature in extremities
  • info fed to the thermoregulatory centre in hypothalamus
  • brain initiates behavioural mechanisms to maintain body temp (move into shade)

B5 (8 decks)

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