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homeostasis Flashcards

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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
give examples of amino acid hormones
adrenaline | thyroxine
26
what is a positive feedback loop?
when the signal is amplified eg. the clotting cascade
27
what is a negative feedback loop?
Increase or decrease in variable → response that moves variable in opposite direction
28
what type of problems can you have with a feedback loop?
PRIMARY - the problems is with the endocrine gland | SECONDARY - the problem is with the control centre
29
what % of your bodyweight is water?
60%
30
what electrolytes does the ICF mainly contain?
K+
31
what electrolytes does the ECF mainly contain?
Na+ (most) CL- HCO3- CA2+
32
what are the 3 compartments of the ECF?
1. interstitial fluid 2. plasma 3. transcellular
33
define ISF
intersistial fluid - part of ECF - surrounds the cells - but doesn't circulate - it is the fluid between the vessels and cells
34
define plasma
- intravascular - circulates in blood - part of ECF
35
define transcellular fluid
- part of ECF - doesn't circulate or surround - makes up CSF,mucus etc.
36
describe the water distribution for an average 70Kg male (total water of 42L)
- ICF → 28L , (40%) | - ECF → 14L, (20%)
37
describe the water distribution for an average 70Kg male (total water of 42L) WITHIN the ECF
ISF - 11L | plasma - 3L
38
what is a general rule about the relationship between Na+ and H20?
water travels in the direction of increasing sodium concentration via osmosis
39
what are examples of sensible water loss?
pee | - things you can measure
40
what are examples of insensible water loss?
sweat , breath, faeces, vaginal secretions | - immeasurable
41
in short, what happens if you are fluid deficient?
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
in short, what happens if your fluid levels are excessive?
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
what are the 3 regulating hormones involved in water homeostasis?
1. ADH 2. alderstone 3. atrial natriuretic peptide
44
what is the definition of an Osmole?
= unit of osmotic pressure
45
what is the definition of osmosis?
= net movement of water from an area of low solute concentration to an area of high solute concentration through a semipermeable membrane
46
what is the definition of osmolality?
= the concentration of body fluids measured in terms of the amount of dissolved substances per unit mass of water
47
what is the definition of osmotic pressure?
= pressure by which water is drawn into a solution through the semipermeable membrane
48
what is ADH?
- antidiuretic hormone - peptide - aka. vasopressin - regulates retention of water in kidneys
49
where is ADH synthesised and stored?
- made in hypothalamus | - stored in posterior pituitary gland
50
what are the 2 main factors that promote the release of ADH?
1. change in plama osmotic pressure | 2. change in volume
51
what hormone promotes ADH inhibition? where and why is this hormone released?
- atrial natriuretic peptide, ANP - released by stretched atria - in response to increase in BP, alcohol or medications
52
what factors influence osmotic pressure?
changes in plasma volume --> affects plasma osmality -> affects osmotic pressure
53
what is hypovolemia?
a state of abnormally low extracellular fluid in the body
54
what is hypervolemia?
too much water in body
55
what action does ADH undergo in regards to aquaporin-2 channels?
ADH acts through a G-protein coupled receptor to increase the transcription and insertion of Aquaporin–2 channels to the apical membrane of the DCT and CD cells. this increases their permeability
56
what is hydrostatic pressure?
the pressure difference between capillary blood and interstitial fluid because its higher in capillaries, it forces water and solutes from plasm to ISF
57
what is oncotic pressure?
osmotic pressure caused by difference in protein conc between the ISF and plasma
58
what protein is retained in the capillaries?
albumin
59
what is RAAS?
= the Renin-angiotensin-aldosterone system
60
which cells sense a decrease in BP + blood volume (as a result of dehydration or Na + deficiency) ?
the macula densa cells
61
how is angiotensin I synthesised?
- angiotensinogen produced in liver | - cleaved by renin
62
how is angiotensin II synthesised?
- angiotensin converting enzyme (ACE) produced in lungs | - converts angiotensin I to II
63
what inhibits renin release?
atrial natriuretic peptide (ANP)
64
what are the actions of angiotensin II?
- cause efferent and afferent arteriole constriction - increases Na+ reabsorption in PCT - increases thirst sensation
65
what stimulates the release of aldosterone?
- angiotensin II acts on adrenal cortex | - adrenal cortex releases aldosterone
66
what is aldosterone? what cells does it act on ?
- steroid hormone | - acts of principal cells in the collecting ducts of the nephron
67
how does alderstone affect Na+ channels?
- increases their expression | - therefore increases sodium reabsorption
68
what movement does K+ undergo in the RAAS?
- K+ is exchanged for Na in the sodium/potassium pump | - K therefore moves into the nephron and is excreted in the urine
69
what are ACE inhibitors?
- treat hypertension and heart failure | - by stopping ACEs producing angiotensin II

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