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biology module 5 > homeostasis > Flashcards

homeostasis Flashcards

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1
Q

homeostasis definition

A

the maintenance of internal environments within restricted limits through physiological control systems

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2
Q

why is homeostasis important

A

ensures the maintenance for optimal conditions for enzyme action and cell function

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3
Q

give 6 examples of factors controlled by homeostasis

A
  • core body temperature
  • metabolic waste e.g. CO2,urea
  • blood ph
  • blood glucose conc
  • blood water potential
  • conc of respiratory gases in blood, e.g.CO2, O2
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4
Q

what are the 3 main factors controlled by homeostasis

A

temperature
ph
blood glucose conc

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5
Q

what are the effects of temperature being too high or low

A

if temp is too high enzymes denature as heat breaks peptide bonds so less enzyme substrate complexes formed

if temp is too low enzymes are too slow as they don’t have enough energy so less enzyme substrate complexes formed

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6
Q

what are the effects of ph being too high or low

A

at ph extremes enzymes denature because excess OH-/H+ causes peptide bonds to break so active site shape changes so less enzyme substrate complexes formed

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7
Q

what are the effects of blood glucose conc being too high or low

A

if blood glucose conc is too high it can have a large impact on water potential of blood and can lead to crenation/bursting of cells

if blood glucose conc is too low there may not be enough glucose for respiration

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8
Q

ectotherm definition

A

an animal that is dependent on external sources of heat and behaviourally thermoregulates

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9
Q

endotherm definition

A

an animal that can internally generate heat and physiologically thermoregulates

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10
Q

thermoregulation definition

A

the ability of an organism to keep its body temp within specific limits

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11
Q

hypothalamus definition

A

a region of the brain which controls homeostatic systems + nervous systems + pituitary gland

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12
Q

what makes up the nervous system

A

CNS - central nervous system, consists of brain + spinal cord - and PNS - peripheral nervous system, consists of the rest of the nerves in the body

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13
Q

outline the function of the nervous system

A

it allows us to detect + respond to surrounding stimuli and coordinate + regulate bodily functions

this is done by sending information through nerve impulses

responses are instant

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14
Q

nerve impulse definition

A

electrical signals that pass along nerve cells/neurones

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15
Q

nerve definition

A

a bundle of neurones

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16
Q

outline the function of neurones

A

neurones coordinate the activity of sensory receptors and decision making centers in CNS and effectors

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17
Q

hormone definition

A

a chemical substance produced by an endocrine gland and carried in the blood

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18
Q

outline the function of a hormone

A

hormones transmit information within an organism and bring about a change by altering the activity of one or more target organs

they are used to control functions that don’t need instant responses

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19
Q

gland definition

A

a group of cells that produce + secrete substances + hormones

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20
Q

cell signalling definition

A

the process by which cells communicate with eachother

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20
Q

what makes the nervous and endocrine system effective communication systems

A
  • they cover the whole body
  • enable both long and short term responses
21
Q

why is cell signalling important

A

it allows multicellular organisms to control and coordinate their bodies and respond to their environments

22
Q

outline the process of cell signalling

A
  • stimulus is received by receptor cell
  • stimulus is converted into a signal (a chemical) through transduction
  • signal is transmitted to a target cell (effector) that can detect it via receptors on the cell surface membrane
  • an appropriate response is made
23
Q

what are the 3 types of cell signalling pathways

A

paracrine, endocrine, neuronal signalling

24
Q

pacrine signalling vs endocrine signalling

A

paracrine signalling is signalling between cells that are close together, with cytokines that diffuse through tissue fluid and are either taken up by cells or regraded by enzymes

endocrine signalling is signalling between cells that are far apart via circulatory system

25
Q

what is a cell signalling molecule

A

these are the signal molecules transported around in the process of cell signalling

can be proteins, glycoproteins, amino acids, lipids, etc - e.g. in endocrine signallign it is always hormones, either peptide or lipid

should be small for easy transport across cell membranes

26
Q

what are receptor molecules

A

receptor molecules allow target cells ot detect the signalling molecules so a specific change or reaction can be carried out

receptors can be either proteins or glycoproteins, and can be on the cell surface membrane or in the cell cytoplasm

27
Q

negative feedback definition

A

when the body responds to a change by reversing the change or reducing the initial effect of the stimulus

28
Q

what 3 parts are involved in a negative feedback cycle

A

receptor - to detect stimuli

coordination system - to transfer information, e.g. endocrine or nervous

effector - to carry out response

29
Q

give 2 examples of processes managed by negative feedback cycles

A

ADH secretion
blood glucose regulation

30
Q

positive feedback cycle definition

A

when the body responds to a change by enhancing the initial effect

31
Q

give 2 examples of positive feedback cycles

A

cervical contractions in labour - due to oxytocin
blood clotting

32
Q

what is the optimum core body temp in humans

A

37C

33
Q

what does it mean if body temp is too high or low

A

above 38C can indicate fever

below 35C can indicate hypothermia

34
Q

give 2 examples of endotherms

A

mammals, birds

35
Q

how do endotherms detect temperatures

A

through peripheral receptors - found in skin + mucous membranes, receptors for both hot and cold - these receptors communicate with the hypothalamus to bring about a physiological response to changing external temperatures

the hypothalamus also detects body temp by monitoring the temp of the blood flowing through it

36
Q

give 2 examples of ectotherms

A

replites, fish

37
Q

give an example of how ectotherms heat up and cool down

A

to heat up they seek out the sun or warm surfaces, and rest or bask until their body temp has been sufficiently raised

to cool down they seek shade or water

38
Q

outline some advantages and disadvantaged of being an endotherm or an ectotherm

A

the behaviour of ectotherms is more limited by environmental temps, so they cannot easily colonise habitats that are very hot or very cold

endotherms require much more energy to maintain body temps so much greater food requirements, so they cannot survive as well in environments where food is limited

39
Q

what is the difference between environments on land and in water

A

on land temperature can vary greatly across seasons or in a single day - this means terrestrial ectotherms may experience lots of difficulty maintaining their stable environment

however water is a stable environment and has a very high specific heat capacity so temp of water is much less variable - aquatic ectotherms have little difficulty maintaining a stable internal environment

40
Q

give 3 examples of cooling mechanisms in endotherms

A

vasodilation
sweating
flattening of hairs

41
Q

describe how vasodilation aids in thermoregulation

A
  • heat exchange occurs at skin surface due to short distance between blood and external environment
  • arterioles have muscles in walls so can relax to dilate lumen allowing them so carry higher volumes of blood
  • supplying capillaries in skin with a higher volume of blood increases heat loss by radiation
42
Q

describe how sweating aids in thermoregulation

A
  • sweat is secreted by sweat glands + cools the skin by evaporating off it, which uses heat energy from the body
  • this is less effective in high humidity due to shallower water potential gradient
43
Q

describe how flattening of hairs aids in thermoregulation

A
  • hair erector muscles in skin relax so hairs lie flat
  • this stops an insulative layer of air from forming and so heat can leave body through skin via radiation
44
Q

give 4 warming mechanisms in endotherms

A

vasoconstriction
boosting metabolic rate
shivering
erection of hairs

45
Q

describe how vasoconstriction aids in thermoregulation

A
  • arteriole wall muscles contract to constrict lumen, so vessels can only carry smaller volumes of blood
  • this causes blood to be diverted to shunt vessels further from skin surface, increasing diffusion distance
  • this means there is a lower volume of blood near the skin to less heat loss via radiation
46
Q

describe how boosting metabolic rate aids in thermoregulation

A
  • most metabolic reactions are exothermic so release heat, so increase body temp
  • body secretes thyroxine to increase basal metabolic rate and increase heat production in body
47
Q

describe how shivering aids in thermoregulation

A
  • a reflex action in response to decrease in core body temp
  • nervous system response
  • muscles are effectors - they rapidly contract and relax
  • metabolic reactions needed to generate energy for this movement are exothermic so generate heat so increase body temp
48
Q

describe how erection of hairs aids in thermoregulation

A
  • hair erector muscles in skin contract and cause hairs to stand up
  • this forms an insulating layer over skins surface by trapping air between hairs, so stops heat loss via radiation
49
Q

some insects are also endotherms - give 2 reasons why would it be more difficult for insects to thermoregulate than mammals or birds

A
  • mammals/birds have thicker insulation
  • insects have higher SA:Vs so heat generated is lost more easily

biology module 5 (7 decks)

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