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NPLEX I 2024 > Endocrine Physiology > Flashcards

Endocrine Physiology Flashcards

1
Q

What is another name for somatostatin?

A

Growth hormone inhibiting hormone

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2
Q

what is another name for prolactin inhibition factor?

A

dopamine

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3
Q

what hormones are released from the hypothalamus?

A

TRH
CRH
GhRH
GhIH (somatostatin)
GRH
PIF (dopamine)

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4
Q

what hormones are released from the anterior pituitary?

A

GH
TSH
prolactin
adrenocorticotropic hormone
FSH
LH

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5
Q

what hormones are released from the posterior pituitary?

A

ADH (vasopressin)
oxytocin

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6
Q

what hormones are released from the thyroid?

A

T3
T4
calcitonin

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7
Q

what hormones are released from the adrenal cortex?

A

cortisol
aldosterone

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8
Q

what hormones are released from the adrenal medulla?

A

epi/norepi

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9
Q

what endocrine hormones are released from the pancreas?

A

insulin
glucagon

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10
Q

composition of hormones in the body

A

polypeptides (<100 AA)
proteins (>100 AA)

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11
Q

where in the cell are most hormones synthesized? what is the process of hormones being stored and released?

A

synthesized on rough ER > prohormones (inactive) transferred to Golgi to be packaged in secretory vesicle

inc cytosolic Ca conc (from PM depolarization) > exocytosis

OR

(secondary messenger system)

stimulation of cell surface receptors > inc cAMP > activates protein kinases > initiaties hormone secretion

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12
Q

explain the following for steroid hormones: synthesis, storage, solubility, binding

A

synthesized from cholesterol
not stored
lipid soluble

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13
Q

explain the following for amine hormones: synthesis, storage, solubility, binding

A

derived from tyrosine

thyroid + adrenal medullary hormones

thyroglobulin incorporates thyroid hormones in thyroid gland

thyroxine binding globulin binds in plasma

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14
Q

how are hormones cleared from plasma?

A

metabolic destruction by tissues

binding by tissues

excretion by liver > bile

excretion by kidneys > urine

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15
Q

what is the metabolic clearance rate?

A

rate of removal of hormone from blood (mL/min)

rate of disappearance of hormone from plasma / conc of hormone

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16
Q

what types of hormone receptors are in or on the surface of the cell membrane?

A

protein, peptide, catecholamine hormones

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17
Q

what types of hormone receptors are in the cell cytoplasm?

A

steroid hormones

(they’re lipid based so can get into the cell)

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18
Q

what types of hormone receptors are in the cell nucleus?

A

thyroid hormones

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19
Q

how are hormone receptors down-regulated? what does this mean about their function change/how fast it occurs?

A

receptor proteins are inactivated/destroyed DURING their function and thus can change from day to day or minute to minute

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20
Q

what are some scenarios that would result in down regulation of hormone receptors?

A

inactivation of receptor molecules

inactivation of intracellular protein signalling molecules (GMP, cAMP, etc)

temporary seqeuestration of receptor to inside of cell (away from site of action of hormones that interact w it)

destruction of receptors by lysosomes after they’re interalized

dec production of receptors

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21
Q

what are the two most common types of hormone receptor complexes?

A

ion channel linked receptor
G protein linked receptors*
enzyme linked receptors
IC hormone receptors

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22
Q

describe an ion channel linked hormone receptor complex

A

all NT substances combine w receptors in postsynaptic membrane
>
change in structure of receptor (opening/closing ion channel; Na, K, Ca, etc)

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23
Q

describe a G protein linked hormone receptor complex

A

activates receptors that indirectly regulate activity of target proteins by coupling with groups of cell membrane proteins (GTP (G) binding proteins)
> Heterotrimeric guanosine triphosphate
>7 transmembrane segments

inhibitory and stimulating G proteins

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24
Q

describe an enzyme linked hormone receptor complex

A

proteins that pass through the membrane only once

hormone binding site EC and catalytic/enzyme binding site IC

ex: tyrosine kinase > leptin receptor

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25
Q

describe an IC hormone receptor complex

A

activation of genes

adrenal and gondal steroid hormones, thyroid hormones, vit D, retinoid hormones; bind with protein receptors within cell (lipid soluble, pass thru plasma membrane)

activated complex binds with regulatory (promotor) sequence of DNA (hormone response element) > activation/repression of transcription of genes and mRNA

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26
Q

briefly describe the adenylyl cyclase-cAMP second messenger system

A

hormone (1st messenger) binds receptor EC> coupling of receptor to a G protein IC

g protein activates (or inhibits), effector enzyme adenylyl cylase (membrane bound enzyme) > converts ATP to cAMP (2nd messenger) inside the cell

activates cAMP dependent protein kinase > phosphorylates other proteins

enzyme cascade is activated

small amount of hormone = large effect

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27
Q

briefly describe the phospholipase C second messenger system

A

enzyme catalyzes breakdown of phospholipids in cell membrane

hormone activated G protein activated an effector enzyme (phospholipase C) which then splits membrane protein PIP2 into two second messengers:

  • inositol triphosphate (IP3) > releases Ca ions from mitochondria and ER
  • diacylglycerol (DAG) > activates enzyme protein kinase C
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28
Q

briefly describe the thyroid hormone hormone receptor system

A

T3 and T4 directly bind to receptor proteins in nucleus

> control function of gene promoters
activate genetic mechanisms for synthesizing many types of IC proteins

(receptors = activated TFs within chromosomal complex)

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29
Q

what are some differences between the endocrine and nervous systems?

A

nervous:
- fast response (directly into blood)
- short duration
- act via AP and NTs
- Act over very short distances
- act at specific locations determined by axon pathways

endocrine:
- slow response (2nd messenger systems)
- longer duration
- act via hormones
- act over long distances
- diffuse target locations

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30
Q

what is the difference between exocrine and endocrine glands?

A

exocrine glands
- produce nonhormonal substances (sweat, saliva)
- have ducts to carry secretion to membrane surface

endocrine glands
- produce hormones, lack ducts

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31
Q

what organs have exocrine AND endocrine functions?

A

pancreas, gonads, placenta

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32
Q

what other tissues/organs produce hormones besides endocrine glands?

A

adipose cells
thymus
cells in small intestine, stomach, kidneys, heart

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33
Q

what glands are endocrine glands?

A

pituitary
thyroid
parathyroid
adrenal
pineal

*hypothalamus is NEUROendocrine gland

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34
Q

autocrines vs paracrines vs hormones

A

hormones: long distance chemical signals that travel in blood or lymph

autocrines and paracrines are local messengers; not part of endocrine system

autocrines: chemicals that exert effects on same cells that secrete them

paracrines: locally acting chemicals that affect cells other than those that secrete them

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35
Q

main classes of hormones

A

amino acid based: AA derivatives, peptides, proteins

steroids (from cholesterol): gonadal and adrenocortical hormones

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36
Q

hormone action on target cells may be done in order to:

A

alter PM permeability and/or MP by opening/closing ion channels

stimulate synthesis of enzymes or other proteins

activate/deactivate enzymes

induce secretory activity

stimulate mitosis

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37
Q

what are the types of hormone actions and what determines them?

A

determined by chemical nature and receptor location

water-soluble hormones (all AA based hormones except for thyroid hormone):
-act on PM receptors
-act via G protein 2nd messengers
-cannot enter cell

lipid soluble hormones (steroid and thyroid hormones):
- act on IC receptors that directly activate genes
- can enter cell

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38
Q

what are the types of endocrine gland stimuli?

A

humoral - changing blood levels of ions and nutrients directly stimulate hormone secretion

neural - nerve fibers stim hormone release

hormonal - hormones stim other endocrine organs to release their hormones

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39
Q

what connects the hypothalamus and pituitary gland?

A

infundibulum (a stalk)

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40
Q

what is the hypophysis? neurohypophysis? adenohypophysis?

A

hypophysis - pituitary gland

neurohypophysis - posterior lobe + infundibulum

adenohypophysis - anterior lobe

41
Q

differences between the lobes of the pituitary gland

A

posterior: composed of neural tissue from a downgrowth of brains > secretes neurohormones

anterior: glandular tissue

42
Q

explain the neural connections and hormones released by the posterior pituitary

A

post pituitary has neural connection to hypothalamus via hypothalmic-hypophyseal tract (arises from neurons in paraventricular and supraoptic nuclei); runs through infundibulum

secretes oxytocin and ADH (stored in axon teerminals and released in blood when neurons fire)

43
Q

oxytocin actions

A

stimulates uterine contractions during childbirth

hormonal trigger for milk ejection

^ both pos feedback mechanisms

NT in brain (uses PIP Ca 2nd messenger system)

44
Q

ADH (antidiuretic hormone) actions

A

targets kidney tubules to reabsorb more water or inhibit/prevent urine formation

high concentrations cause vasoconstriction (hence other name of vasopressin)

45
Q

how is the release of ADH stimulated/inhibited?

A

hypothalamus contains osmoreceptors that monitor solute concentrations

if conc too high > post pit secretes ADH

release also triggered by pain, low BP, drugs

inhibited by alcohol, diuretics

46
Q

describe the derivation of the anterior lobe of the pituitary as well as its connection to the hypothlamus

A

ant lobe derived from an outpocketing of oral mucosa

vascularly connected to hypothalamus via hypophyseal portal system (primary capillary plexus, hypophyseal portal veins, secondary capillary plexus)

hypothalamus secretes releasing and inhibiting hormones to anterior pituitary to regulate hormone secretion

47
Q

anterior hormone hormones

A

all 6 are peptide hormones

all but GH activate target cells via cAMP 2nd messenger sys

all but two are tropic hormones/tropins (besidesGH and PRL) that regulate secretion of other hormones

GH
TSH
ACTH
FSH
LH
PRL

48
Q

GH production and actions

A

also called somatotropin as it is produced by somatotropic cells

direct actions on metabolism
indirect actions on growth

49
Q

GH actions on metabolism

A

DIRECT actions on metabolism
- glucose sparing: dec rate of cellular glucose uptake and metabolism (anti insulin)
- triggers liver to breakdown glycogen > glucose
- inc blood levels of FAs for use as fuel, encourages cellular protein synthesis

50
Q

GH actions on growth

A

INDIRECT actions on growth

  • triggers liver, skeletal muscle, and bone to produce insulin like GFs (IGFs)
  • IGFs stimulate:
    1. cellular uptake of nutrients to synthesize DNA and proteins needed for cell divison
    2. formation of collagen and deposition of bone matrix
    -GH stim most cells to enlarge and dividie, but major targets are bone and skeletal muscle
51
Q

TSH hormone type, release, inhibition, action

A

tropic hormone also called thyrotropin as it is produced by thyrotropic cells

stimulates normal development and secretory activity of thyroid

release triggered by TRH from hypothalamus

inhibited by rising blood levels of thyroid hormones that act on both pituitary and hypothalamus - also inhibited by GHIH

52
Q

ACTH hormone type, release, inhibition, action

A

corticotropin; secreted by corticotropic cells

stimualtes adrenal cortex to release corticosteroids

release is triggered by hypothalmic CRH in daily rhythm (highest in morning)

release also affected by fever, hypoglycemia, and stressors

53
Q

whats a precursor to corticotropin?

A

pro-opiomelanocortin

54
Q

what cells secrete FSH/LH?

A

gonadotropic cells of anterior pituitary (they are also called gonadotropins)

55
Q

FSH and LH actions

A

FSH stim production of gametes (eggs/sperm)

LH promotes production of gonadal hormones (in females = matures egg follicles, triggers ovulation and release of estrogen/progesteorne, males stimulates testosterone production)

56
Q

regulation of LH/FSH release

A

triggered by GnRH during/after puberty (LH/FSH not present in prepubertal blood)

suppressed by gonadal hormones (feedback)

57
Q

prolactin secretion, action, and regulation

A

secreted by prolactin cells of anterior pituitary

stim milk production

regulation primarily controlled by PIH/dopamine; prevents release of PRL until needed

inc estrogen levels and suckling can also stimualte PRL

58
Q

is iodine transfer from blood to cell for thyroid hormone synthesis passive or active?

A

active

59
Q

composition of units T3 and T4

A

T4 = DIT + DIT
T3 = DIT + MIT

60
Q

explain the formation of thyroglobulin

A

ER + golgi > thyroglobulin (70 tyrosine AA)

T4/T3 formed from tyrosine in thyroglobulin molecule remain part of molecule during synthesis of thyroid hormones and after in follicular colloid

61
Q

explain thyroid hormone formation

A

iodine converted via oxidation with peroxidase and hydrogen peroxide

iodine binds with thyroglobulin molecule (organification)

storage within thyroid gland; can store 2-3 months of hormone

62
Q

explain the iodide pump

A

sodium iodide symporter (iodide trapping)

transports iodides from blood > thyroid cells/follicles where the basal membrane of thyroid pumps iodide into the cell

symporter cotransports 1 iodide ion and 2 sodium ions

energy from Na/K ATPase pump > pumps Na out of cell giving low IC Na and a gradient for facilitated Na diffusion into cell

63
Q

where is iodide located in the thyroid gland?

A

cytoplasm of follicular cells

64
Q

thyroid peroxidase functions

A

oxidation
organification of iodine
coupling of MIT and DIT

65
Q

explain the conversion of T4 > T3 in peripheral tissue

A

follicles of thyroid 5-deiodinase converts T4>T3 in peripheral tissue

peripheral conversion inhibited by glucocorticoids, beta blockers, propylthiouracil (PTU)

reverse T3 = metabolically inactive byproduct of peripheral conversion of T4 and its production is increasd by GH and glucocorticoids

66
Q

how is T4/T3 released from the thyroid gland?

A

cleaved from thyroglobulin molecule > free hormones released

pinocytic vesicles enter thyroid cell > lysosomes fuse with vesicles > proteases digest thyroglobulin and release T4/T3 > diffuse through base of thyroid cell to capillaries

67
Q

explain the transport of T4/T3 to tissues

A

once in blood, bound to plasma proteins (synthesized in liver) > thyroxine binding globulin

released slowly to tissue cells > bind with IC proteins and stored or used

slow onset and long duration of action (max rate after 10-12 days)

68
Q

T3 functions

A

7 Bs
Brain maturation

Bone growth (synergistic w GH)

B adrenergic effects (inc B1 receptors in heart > inc CO, HR, SV, contractility)

BMR (via inc Na/K ATPase > inc O2 consumption, RR, body temp)

Blood sugar (through glycogenolysis and gluconeogenesis)

Break down lipids (through lipolysis)

Babies (stim surfactant synthesis)

69
Q

effect of thyroid functions

A

increase transcription of genes
inc cellular metabolic activity
effects on growth
effects on certain body functions

70
Q

what is the role of the thyroid in transcription?

A

most t4 > t3 prior to acting on genes to inc genetic trasncription

thyroid hormone receptors are attached to DNA genetic strands OR located in proximity to them

thyroid hormone receptor forms a heterodimer with retinoid X receptor (RXR) at specific parts of DNA

71
Q

what thyroid hormone is more active? why?

A

T3; IC thyroid receptors have a higher affinity for T3 and it more readily binds

72
Q

how do thyroid hormones increase cellular metabolic activity?

A

inc mitochondira size, number, and activity
- inc membrane SA
- inc ATP production

inc active transport of ions through cell membranes
- Na/K ATPase enzyme inc
- inc rate of transport of Na and K through cell membranes
- inc body heat
- cell membrane = leaky to Na ions

73
Q

thyroid metabolic actions

A

stimulates carb and fat metabolism

inc BMR

dec body weight

inc blood flow and cardiac output

inc vitamin requirement

effect on plasma and liver fats

74
Q

how does thyroid hormone stimulate carb metabolism

A

rapid glucose uptake by cells
inc glycolysis
inc insulin secretion

75
Q

how does thyroid hormone stimulate fat metabolism

A

lipids mobilized rapidly from fat tissue, dec fat stores in body

76
Q

thyroid hormone effect on plasma and liver fats

A

inc thyroid hormone = dec conc of cholesterol, phospholipids, and TGs, but INC free FAs

77
Q

how does thyroid hormone lead to an increased vitamin requirement?

A

inc quantities of body enzymes; vitamins are a part of/cofactors for many of these enzymes

too much thyroid = vitamin def

78
Q

how does thyroid hormone inc CO?

A

inc tissue metabolism > inc oxygen use > vasodilation > inc blood flow > inc CO

79
Q

functions of TSH

A

inc proteolysis of thyroglobulin

inc activity of iodide pump

inc iodination of tyrosine

inc size, secretory activity, and number of thyroid cells

80
Q

describe the thyroid hormonal pathway

A

TRH (hypothalamus) > TSH (ant pit) > T3/T4 (follicular cells)

81
Q

how do t3/t4 become inactive?

A

being bound; usually by thyroxine-binding globulin (TBG)

82
Q

what secondary messenger system is used in TSH regulation

A

Cyclic adenosine monophosphate (cAMP)

83
Q

how does TRH regulate the secretion of TRH?

A

TRH binds with receptors on pituitary cell membrane > activates phospholipase 2nd messenger system >

large amts phospholipase C produced > 2nd messengers including Ca > release of TSH

84
Q

how does cold exposure affect TRH?

A

cold exposure inc TRH (excitation of hypothalmic centers for body temp control)

inc TSH > BMR 15-20% higher

85
Q

how does leptin input affect TRH?

A

TRH neurons in PVN receive input from leptin neurons in arcuate nucleus that regulate energy balance

prolonged fasting dec plasma leptin > dec POMC activity > INC NPY/AGRP neuronal activity

dec leptin > indirectly inhibits TRH > dec thyroid hormone secretion

86
Q

how do things like excitement/anxiety affect TSH secretion?

A

excitement/anxiety stim SNS > dec in TSH secretion

87
Q

what is the wolff-chaikoff effect

A

protective autoregulation

sudden exposure to excess iodine (chemoreceptors notice) > temp turns OFF thyroid peroxidase > dec t3/t4 production

(why ppl take iodine when around radiation to avoid it coming into the thyroid)

88
Q

what is most commonly supplemented in hypothyroidism?

A

T4, unless body has conversion issue from T4>T3

both can be used

89
Q

what happens in graves dz?

A

ab produced that stim TSH receptors and keep producing thyroid hormone with low TSH still; “mimicry of TSH”

90
Q

hormones that directly activate genes are classified as

A

lipid soluble

91
Q

oxytocin is produced where

A

hypothalamus (then stored in post pituitary)

92
Q

in what region of the adrenal gland is aldosterone produced?

A

adrenal cortex (zona glomerulosa)

93
Q

hormones are secreted in response to what types of stimuli

A

neuronal
humoral
hormonal

NOT up regulation > that just increases receptors

94
Q

the ant pituitary stimulates other endocrine organs by secreting a group of hormoness called

A

tropic hormones - target other endocrine organs

95
Q

which endocrine gland is tiny, yellow-brown and arranged in thick, branching cords?

A

parathyroid gland

96
Q

what are the effects of PTH?

A

inc osteoclast activity

inc ca reabsorption in kidney

inc ca absorption in intestine

97
Q

most of the AA based hormones affect the target organs using

A

intracellular second messengers (theyre too big and non lipid based, cant go directly into cell)

98
Q

a person with endemic goiter suffers from

A

hypofunctioning thyroid gland (iodine def)

99
Q
A

NPLEX I 2024 (23 decks)

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