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homeostasis Flashcards

1
Q

what is an effector?

A
  • receives signal from the control centre

- executes the changes needed

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2
Q

what is a hormone?

A

a molecule that acts as a

chemical messenger

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3
Q

what are the 4 different methods of cell communication?

A
  1. autocrine
  2. paracrine
  3. endocrine
  4. exocrine
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4
Q

describe autocrine communication

A
  • cell releases hormone into ECF
  • hormone then binds to cells own receptor
  • acts on itself
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5
Q

describe paracrine communication

A
  • hormones that travel short distances in the ECF ie. local cellular communication
  • eg. ACh
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6
Q

describe endocrine communication

A
  • travels in the BLOOD
  • long distance
  • not via a duct
    eg. HPA
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7
Q

describe exocrine communication

A
  • secretion via ducts into an organ

- eg. salivary glands

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8
Q

what is homeostasis?

A
  • the maintenance of a constant internal environment
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9
Q

what is the key difference between endocrine and paracrine?

A

paracrine: hormone travels in ECF
endocrine: hormone travels in blood

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10
Q

what are the 3 major types of hormone molecule?

A
  1. peptide
  2. steroid
  3. amino acid
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11
Q

what are peptide hormones synthesised from?

A

amino acid chains

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12
Q

what are steroid hormones synthesised from?

A

cholesterol (they are lipids)

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13
Q

what are amino acid hormones synthesised from?

A

tyrosine (a small amino acid)

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14
Q

which of the 3 hormones has the fastest rate of release?

A
  1. peptide - fast
  2. amino acid
  3. steroid - slow
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15
Q

which of the 3 hormones has the longest duration of affect?

A
  1. steroid - long
  2. amino acid - varies
  3. peptide - short
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16
Q

where are peptide hormones stored?

A
  • in vesicles

- released in response to stimuli

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17
Q

where are steroid hormones stored?

A
  • NOT stored

- immediately diffuse

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18
Q

where are amino acid hormones stored?

A
  • in endocrine cells
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19
Q

which hormones are polar and soluble in water?

A

peptide –> polar & soluble
steroid –> non-olar, non-soluble
amino acid –> varies (mainly similar to peptide)

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20
Q

how do peptide and Amino Acid hormones enact a response?

A

signal transduction cascade (bind to receptor, trigger response in cell)

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21
Q

how do steroid hormones enact a response?

A
  • diffuse across plasma membranes
  • bind to DNA in nucleus
  • alter gene transcription
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22
Q

how do each of the hormones travel to their target cell?

A

peptide - dissolves in blood
steroid - travel in blood bound to a protein carrier
AA - depends on solubility ( if can’t dissolve, needs a carrier protein)

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23
Q

give examples of peptide hormones

A

ADH
insulin
glucagon

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24
Q

give examples of steroid hormones

A

reproductie hormones

cortisol

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25
Q

give examples of amino acid hormones

A

adrenaline

thyroxine

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26
Q

what is a positive feedback loop?

A

when the signal is amplified eg. the clotting cascade

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27
Q

what is a negative feedback loop?

A

Increase or decrease in variable → response that moves variable in opposite direction

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28
Q

what type of problems can you have with a feedback loop?

A

PRIMARY - the problems is with the endocrine gland

SECONDARY - the problem is with the control centre

29
Q

what % of your bodyweight is water?

A

60%

30
Q

what electrolytes does the ICF mainly contain?

A

K+

31
Q

what electrolytes does the ECF mainly contain?

A

Na+ (most)
CL-
HCO3-
CA2+

32
Q

what are the 3 compartments of the ECF?

A
  1. interstitial fluid
  2. plasma
  3. transcellular
33
Q

define ISF

A

intersistial fluid

  • part of ECF
  • surrounds the cells
  • but doesn’t circulate
  • it is the fluid between the vessels and cells
34
Q

define plasma

A
  • intravascular
  • circulates in blood
  • part of ECF
35
Q

define transcellular fluid

A
  • part of ECF
  • doesn’t circulate or surround
  • makes up CSF,mucus etc.
36
Q

describe the water distribution for an average 70Kg male (total water of 42L)

A
  • ICF → 28L , (40%)

- ECF → 14L, (20%)

37
Q

describe the water distribution for an average 70Kg male (total water of 42L) WITHIN the ECF

A

ISF - 11L

plasma - 3L

38
Q

what is a general rule about the relationship between Na+ and H20?

A

water travels in the direction of increasing sodium concentration viaosmosis

39
Q

what are examples of sensible water loss?

A

pee

- things you can measure

40
Q

what are examples of insensible water loss?

A

sweat , breath, faeces, vaginal secretions

- immeasurable

41
Q

in short, what happens if you are fluid deficient?

A
  1. osmolality increased
  2. water exits cells and enters plasma
    (osmosis)
  3. stimulates osmoreceptors cells
  4. increase in ADH & alderstone release
  5. kidneys retain more fluid
  6. urine output falls
42
Q

in short, what happens if your fluid levels are excessive?

A
  1. increase in plasma vol
  2. osmolality of plasma all reduce
  3. water moves into osmoreceptor cells
  4. suppression of ADH & alderstone release
  5. less fluid retained by kidney
  6. urine vol increases
43
Q

what are the 3 regulating hormones involved in water homeostasis?

A
  1. ADH
  2. alderstone
  3. atrial natriuretic peptide
44
Q

what is the definition of an Osmole?

A

= unit of osmotic pressure

45
Q

what is the definition of osmosis?

A

= net movement of water from an area of low solute concentration to an area of high solute concentration through a semipermeable membrane

46
Q

what is the definition of osmolality?

A

= the concentration of body fluids measured in terms of the amount of dissolved substances per unit mass of water

47
Q

what is the definition of osmotic pressure?

A

= pressure by which water is drawn into a solution through the semipermeable membrane

48
Q

what is ADH?

A
  • antidiuretic hormone
  • peptide
  • aka. vasopressin
  • regulates retention of water in kidneys
49
Q

where is ADH synthesised and stored?

A
  • made in hypothalamus

- stored in posterior pituitary gland

50
Q

what are the 2 main factors that promote the release of ADH?

A
  1. change in plama osmotic pressure

2. change in volume

51
Q

what hormone promotes ADH inhibition? where and why is this hormone released?

A
  • atrial natriuretic peptide, ANP
  • released by stretched atria
  • in response to increase in BP, alcohol or medications
52
Q

what factors influence osmotic pressure?

A

changes in plasma volume –> affects plasma osmality -> affects osmotic pressure

53
Q

what is hypovolemia?

A

a state of abnormally low extracellular fluid in the body

54
Q

what is hypervolemia?

A

too much water in body

55
Q

what action does ADH undergo in regards to aquaporin-2 channels?

A

ADH acts through a G-protein coupled receptor to increase the transcription and insertion ofAquaporin–2 channels to the apical membrane of the DCT and CD cells. this increases their permeability

56
Q

what is hydrostatic pressure?

A

the pressure difference between capillary blood and interstitial fluid

because its higher in capillaries, it forces water and solutes from plasm to ISF

57
Q

what is oncotic pressure?

A

osmotic pressure caused by difference in protein conc between the ISF and plasma

58
Q

what protein is retained in the capillaries?

A

albumin

59
Q

what is RAAS?

A

= the Renin-angiotensin-aldosterone system

60
Q

which cells sense a decrease in BP + blood volume (as a result of dehydration or Na + deficiency) ?

A

the macula densa cells

61
Q

how is angiotensin I synthesised?

A
  • angiotensinogen produced in liver

- cleaved by renin

62
Q

how is angiotensin II synthesised?

A
  • angiotensin converting enzyme (ACE) produced in lungs

- converts angiotensin I to II

63
Q

what inhibits renin release?

A

atrial natriuretic peptide(ANP)

64
Q

what are the actions of angiotensin II?

A
  • cause efferent and afferent arteriole constriction
  • increases Na+ reabsorption in PCT
  • increases thirst sensation
65
Q

what stimulates the release of aldosterone?

A
  • angiotensin II acts on adrenal cortex

- adrenal cortex releases aldosterone

66
Q

what is aldosterone? what cells does it act on ?

A
  • steroid hormone

- acts of principal cells in the collecting ducts of the nephron

67
Q

how does alderstone affect Na+ channels?

A
  • increases their expression

- therefore increases sodium reabsorption

68
Q

what movement does K+ undergo in the RAAS?

A
  • K+ is exchanged for Na in the sodium/potassium pump

- K therefore moves into the nephron and is excreted in the urine

69
Q

what are ACE inhibitors?

A
  • treat hypertension and heart failure

- by stopping ACEs producing angiotensin II

1 IMMS (4 decks)

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