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Normal animal exam 3 > endocrine physiology > Flashcards

endocrine physiology Flashcards

1
Q

components of the endocrine system

A

hormones, organs, metabolites/metabolic products

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2
Q

hormone communication

A

produced in one area, transported by blood, affect cells in another area, act in low concentration

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3
Q

paracrine communication

A

produced in one cell, transported in extracellular fluid to adjacent cells, affect those.
some overlap with hormones: prostaglandins, cytokines, somatomedins

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4
Q

neurotransmitters type of communication

A

paracrine but special

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5
Q

autocrine communication

A

produced by and affect same cell

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6
Q

2 main classes of hormones

A

proteins (polypeptides)
steroids

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7
Q

protein hormone synthesis

A
  1. pre pro hormone made in ribosome
  2. ‘pre’ part attaches to RER leaving a prohormone
  3. pro hormone put into cytoplasmic vesicles and lose ‘pro’
  4. hormone is stored in coalesced granules until release
  5. secretion mediated by ATP, Ca2+
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8
Q

steroid hormone synthesis

A

formed as needed, not stored

mostly made from cholesterol (cholesterol is made in the liver and can be stored)

can be built from scratch from acetate

formed in the mitochondria and other cell components

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9
Q

protein hormone transport

A

proteins are mostly hydrophilic, simply dissolve in blood

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10
Q

steroid hormone transport

A

lipophilic

associate with specific binding proteins that are hydrophilic

binding proteins are very specific to the hormone

also non specific binding to albumin for transport

binding and unbinding is in equilibrium (unbound is 1%)

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11
Q

protein hormone receptors

A

on cell surface

trigger a cascade of activations of enzymes

eventually signal to the nucleus

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12
Q

steroid hormone receptors

A

in cytosol or nucleus

(steroid can diffuse into cell)

shorter pathway to upregulate the nucleus

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13
Q

degredation of protein hormones

A

cleaved by peptidases

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14
Q

degredation of steroid hormones

A

steroid hormones are reduced, conjugated with sulfates or glucuronides.

then they are water soluable and can be excreted in urine

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15
Q

what do hormones do?

A

regulate metabolism, mineral balance, water balance, energy production and maintenance, reproductive control

most hormones only target one function

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16
Q

negative feedback loop

A

most feedback is negative, in the sense that an adequate concentration turns off some stimulatory sequence

negative feedback keeps hormonal levels from increasing to abnormal levels

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17
Q

how to pinpoint a failure in a feedback loop

A

measure the hormone

measure the metabolite

measure any stimulatory hormone

this pinpoints the failure

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18
Q

posterior pituitary

A

pars nervosa

cell bodies are in the hypothalamus, axons go to posterior pituitary

hormones are released from there

  1. oxytocin
  2. vasopressin
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19
Q

posterior pituitary

A

pars nervosa

cell bodies are in the hypothalamus, axons go to posterior pituitary

hormones are released from there

  1. oxytocin
  2. vasopressin
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20
Q

oxytocin

A

milk letdown

smooth muscle contraction during parturition

maternal behavior and bonding

from posterior pituitary

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21
Q

vasopressin

A

same as antidiuretic hormone

reclaims water from urine to increase blood volume

constricts arterioles to decrease functional blood volume (increase BP)

moderate behavior effects (maternal behavior and bonding)

absence leads to diabetes insipidus (too much unconcentrated urine)

from posterior pituitary

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22
Q

anterior pituitary

A

glandular, not nervous

complicated embryonic region (lots of things can go wrong)

several distinct cell types, each a specialist for one hormone

Growth hormone

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23
Q

growth hormone

A

from ant pituitary

negative feedback from somatomedin

stim growth of bones (length if epiphysis open, width if epiphysis closed)

causes gluconeogenesis (can cause moderate hyperglycemia)

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24
Q

deficiency of growth hormone

A

dwarfism, complicated with other syndromes with other hormone problems

25
Q

hypersecretion of growth hormone before maturity

A

gigantism

26
Q

hypersecretion of growth hormone after maturity

A

acromegaly

usually cats

diabetic from exhaustion of beta cells

27
Q

thyroid stimulating hormone (TSH)

A

stimulates growth and activity of thyroid follicular cells

from ant pituitary

follicular cells make mostly tetraiodothyronine (T4) and also triiodothyronine (T3)

T4 is placed into colloid into follicular lumen attached to thyroglobulin (high affinity, high specificity)

when needed, it is absorbed, split from the thyroglobulin, and secreted into bloodstream. Lipophilic, so attached to thyroid binding globulin

28
Q

T3 and T4

A

follicular cells make mostly tetraiodothyronine (T4) and also triiodothyronine (T3)

T4 is placed into colloid into follicular lumen attached to thyroglobulin (high affinity, high specificity)

when needed, it is absorbed, split from the thyroglobulin, and secreted into bloodstream. Lipophilic, so attached to thyroid binding globulin

T4 is the main product, but metabolized to T3 by kidney and liver. T4 and T3 are both metabolically active

T3 and T4 interact with receptors in the nucleus, NOT on the cell surface

29
Q

thyroid functions

A

several actions to increase metabolism

increase O2 uptake and use, enhance heat production

increase glucose absorption from gut, enhance movement of glucose into cells (partly by insulin)

facilitate growth along with growth hormone

enhance lipolysis and can lead to hypercholesterolemia

enhance neural function and cardiac function

30
Q

overstimulation by TSH

A

due to iodide deficiency or poisoning of enzymes. T3 and T4 cannot be made

31
Q

hypersecretion of T3/T4 from hyperplastic region in cats

A

autonomous secretion, so ↑ T3/T4, ↓TSH (neg feedback)

32
Q

adrenal glands

A

2 independent glands:

cortex – comes from mesodermal coelomic epithelium, produces steroid hormones

medulla – comes from neurectoderm, produces vasoactive catecholamines

33
Q

adrenal glands cortex

A

comes from mesodermal coelomic epithelium, produces steroid hormones

34
Q

adrenal gland medulla

A

comes from neurectoderm, produces vasoactive catecholamines

basic action is similar to a postgangionic sympathetic neuron

release catecholamines into the blood stream instead of into a neuronal synapse

fight or flight

  • epinephrine and norepinephrine with a1 a2 b1 b2 b3 receptors
35
Q

zona glomerulosa

A

adrenal cortex

mineralocorticoids, not pituitary dependent

36
Q

zona fasciculata

A

adrenal cortex

glucocorticoids, pituitary dependent (ACTH)

37
Q

zona reticularis

A

adrenal cortex

glucocorticoids and sex steroids, pituitary dependent

38
Q

temporary fetal zone in adrenal cortex

A

helps with estrogen production during pregnancy and soon after parturition. regresses postpartum

39
Q

steroid hormones

A

all inter-related

production depends on specific enzymes that are localized to specific cells

some overlap of function

40
Q

glucocorticoids (transport, function, examples)

A

transported with proteins in blood, both specifically and nonspecifically

  • bind to receptors in cytosol, then go to nucleus and affect transcription

function:

  • metabolic: gluconeogenesis, lipolysis, protein catabolism, increased water excretion
  • inflammatory: decreased in general, suppressed immunity

Examples:

  • cortisol is mainly metabolic
  • corticosterone is mainly anti-inflammatory

they each overlap, and also overlap with mineralocorticoids

highest in day, lowest at night

synthetic mimics are common as therapeutic drugs, mainly for anti-inflammatory properties

41
Q

glucocorticoid ACTH feedback

A

stress upregulates ACTH secretion

ACTH stimulates production of glucocorticoids

glucocorticoids inhibit ACTH secretion

chronic stress is a major stimulation

42
Q

using glucocorticoids as clinical therapeutics

A

main use is anti-inflammatory

pathways to upregulate or downregulate are slow and delicate

exogenous products work quickly

once removed the body responds slowly

taper exogenous sources slowly to allow endogenous system to recover

43
Q

mineralocorticoids

A

aldosterone is the main one

affects distal renal tubules, also salivary glands, sweat glands.

moves Na+ from cell to interstitium, water follows

this also loses K+ , H+ so can cause metabolic alkalosis

44
Q

aldosterone production

A

renin is an enzyme from kidney, upregulated by ↓ blood pressure

renin activates angiotensinogen to angiotensin I which goes to angiotensin II

angiotensin II stimulates aldosterone production

45
Q

mineral balance

A

many factors interact

electrolytes are essential for fluid homeostasis as well as cell functions

46
Q

control mechanisms (angiotensin/renin/aldosterone system) in heart failure

A

↓ heart function

↓ blood pressure (this is all the renin-angiotensin-aldosterone system actually sees and responds to)

↑ renin ↑ angiotensin II ↑ aldosterone

↑ fluid retention, further overloading heart which cannot raise blood pressure, further stimulating renin

47
Q

epinephrine/norepinephrine

A

from adrenal medulla, fight or flight

shunt blood from viscera to muscle

raise blood glucose

increase heart rate and stroke volume

considerable overlap between function and receptors

48
Q

pancreatic islets

A

endocrine pancreas

⍺ cells - glucagon

β cells - insulin

D cells - somatostatin

F cells –pancreatic polypeptide

48
Q

pancreatic islets

A

endocrine pancreas

⍺ cells - glucagon

β cells - insulin

D cells - somatostatin

F cells –pancreatic polypeptide

49
Q

insulin

A

highly conserved sequence across all species

from pancreatic β cells

it is essential for moving glucose, fatty acids, and amino acids from the blood into cells (liver) where they are transformed into their storage forms:

  • glycogen
  • triglycerides
  • proteins

mostly released in response to high blood glucose

interacts with a host of other hormones as well

this provides for fairly tight control over BG levels

50
Q

glucogon

A

most from pancreas ⍺ cells, also from intestinal cells

decreases glycogen synthesis

increases glycogenolysis

increases gluconeogenesis

therefore – raises blood glucose

51
Q

somatostatin

A

pancreatic D cells

many different sites of production

inhibits secretion of other islet hormones

diminishes gut motility

52
Q

pancreatic polypeptide

A

pancreatic D cells, islets are the only source

increases gut motility

53
Q

gastrointestinal hormones

A

from isolated cells in the gastrointestinal mucosa

not a localized site

many different hormones with slightly different effects

54
Q

calcium homeostasis

A

Ca2+ is a very important ion.

Functions

  • cell membranes
  • muscle contractility.

It MUST be maintained within a narrow range… or you die.

Hypocalcemia is more immediately threatening than hypercalcemia

three main players:

  • parathormone
  • calcitonin
  • vitamin D
55
Q

parathormone

A

from the parathyroid

secreted:

  • in response to low [Ca2+]
  • in a diurnal rhythm, highest right after waking.

resorbs Ca2+ from bone

increases resorption in kidney

decreases renal resorption of PO4-

upregulates activation of vitamin D

56
Q

calcitonin

A

from the parafollicular cells (also called C-cells) of the thyroid.

lowers [Ca2+], thereby increasing [P04-]

[Ca2+] and [P04-] exist in inorganic chemistry equilibrium. the product is usually about 40, with [Ca2+] 10 and [P04-] 4.

at a product level of 70, Ca2P04 simply precipitates out

57
Q

vitamin D

A

functions as a hormone

produced in skin, ultraviolet light essential for synthesis

inactive form goes to active form by sequential steps in liver and kidney

enhances absorption of Ca2+ from intestine.

high [P04-] induces a pathway that leads to inactive vit D

Normal animal exam 3 (17 decks)

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