Physiology

_______ are released by axon terminals of neurons into synaptic junctions and act locally to control cell fxn

neurotransmitters

_________ are released by glands into blood and influence fxn of target cells at another location

endocrine hormones

__________ are secreted by neurons into blood and influence fxn of target cells at another location

neuroendocrine hormones

__________ are secreted by cells into extracell fluid and affect neighbouring target cells

paracrines

_________ are secreted by cells into the extracellular fluid and affect the functionof the same cells that produced them

autocrines

____________ are peptides secreted by cells into the extracellular fluid and can function as autocrines, paracrines, or endocrine hormones

cytokines

hypothalamic neuroendocrine neurons produce

hormones

role thyroxine

increases rate of chem rxns of all cells

________ rests upon hypophyseal fossa of sphenoid in middle cranial fossa, surrounded by sella turcica and covered by dural fold

pituitary gland

3 parts pituitary gland

adenohypophysis, int lobe (secretes MSH), neurohypophysis

hormones of ant pituitary

ACTH, FSH, GH, LH, TSH

_______ stimulates protein synthesis and overall growth of most cells and tissue

GH

__________ stimulates synthesis and secretion of thyroid hormones (thyroxine andtriiodothyronine)

tsh

__________ stimulates synthesis and secretion of adrenocortical hormones (cortisol,androgens, and aldosterone

ACTH

_______ promotes development of the female breasts and secretion of milk

PRL

___________ causes growth of follicles in the ovaries and sperm maturation in Sertolicells of testes

FSH

___________ stimulates testosterone synthesis in Leydig cells of testes; stimulatesovulation, formation of corpus luteum, and estrogen and progesteronesynthesis in ovaries

LH

hormones acting on ant pituitary

TRH (→ TSH, PRL), CRH (→ ACTH), GHRH (→GH), somatostatin (inhibits GH), dopamine (inhibits PRL), GnRH (→ FSH, LH)

post pituitary hormones

ADH, oxytocin

_____ increases water, reabsorption by the kidneys and causes vasoconstriction and increased blood pressure, maintaining plasma osmolality

ADH

_______ stimulates milk ejection from breasts and uterine contractions

oxytocin

_____ increases the rates of chemicalreactions in most cells, thus increasing body metabolic rate

t4 and t3

_____________ promotes deposition of calcium in the bones and decreasesextracellular fluid calcium ion concentration, decreases osteoclasts

calcitonin

hormones of thyroid

T4, T3, calcitonin

_______ controls serum calcium ion concentration byincreasing calcium absorption by the gut and kidneys, and releasing calciumfrom bones

PTH

adrenal hormones

cortisol, aldosterone, adrenal androgens

_______ has multiple metabolic functions: metabolism of proteins, carbohydrates, and fats, has anti-inflammatory effects

cortisol

______ increases renal sodium reabsorption, potassium secretion, and hydrogen ion secretion

aldosterone

_________ are steroid hormones with weak androgenic activity –play arole in in both sexes before puberty

adrenal androgens

what hormones have same effects as sympathetic stimulation

nor and epi

__________ promotes development of male reproductive system and malesecondary sexual characteristics

testosterone

_______ promotes growth and development of female reproductive system,female breasts, and female secondary sexual characteristics

estrogens

_______ Stimulates secretion of the uterine endometrial glands andpromotes development of secretory apparatus of breasts

progesterone

pancreatic hormones

insulin (b cells), glucagon (a cells), PP polypeptide, somatostatin, gastrin, bombestin

___________ promotes glucose entry in many cells, and in this wayinduce HYPOGLYCEMIA

insulin

__________ increases synthesis and release of glucose from the livermuscle and kidney - HYPERGLYCAEMIA

glucagon

3 classes hormones

1. proteins and polypeptides - by pituitary, pancreas (insulin, glucagon), pth, calcitonin
2. steroids - by adrenal (cortisol, ald), ovaries + placenta (estr, prog), testes (testosterone)
3. tyrosine derivatives - by thyroid (t3,t4) and adrenal (epi, nor)

______ are made on ER and are water soluble

peptide hormones

evolution peptide hormones

start as preprohormones, cleaved to prohormones in ER → secretory vesicles in Golgi, release by exocytosis

Peptide hormone-secreting cells are distinguished by

large amounts rER, golgi, secretory granules

___________ are all made from cholesterol, w/ common core structure

steroids

usually there is very little _______ is steroid producing endocrine cells

hormone storage

steroid secreting cells have visible _____ in their cytoplasm, mitochondria and sER

lipid droplets

___________ do not require a specific secretory mechanism and just diffuse out the cell

steroid hormones

__________ Are derived from amino acids, and formed by the actions of enzymes in thecytoplasmic compartments of glandular cell

amine hormones

4 major amine hormones

ctch (epi and nor), dopa, serotonin

thyroglobulin

in colloid follicles, store thyroid hormones

set point regulation

type of hormone secretion pattern, rare, maintenance of a hormone secretion and concentration toa stable set level

2 patterns of episodic secretion hormones

random (isolated episodes maintain set point), bursts

duirnal variation

pattern of hormone secretion, predictable daily pattern by SCN in hypothalamus’s ‘body clock’

pattern of hormone secretion of GH, cortisol, melatonin and ACTH

diurnal variation

pattern of hormone secretion of LH

positive feedback

how is cortisol secreted

hypothalamus → CRH released → ant pituitary → ACTH secreted → adrenal cortical cells → cortisol synthesized

how is cortisol feedback regulated

cortisol inhibited CRH and ACTH

__________ are dissolved into plasma to target tissue

water soluble hormones (peptides + ctch)

_______ circulate bound to plasma proteins

steroid and thyroid hormones

2 factors modifying conc hormone in blood

rate of hormone secretion, metabolic clearance rate

how are hormones cleared from plasma

metabolic destruction by tissues, tissue binding, excretion by liver or kidneys

types of hormones with types of receptor locations

surface - protein + ctch

cytosol - steroid

nucleus - thyroid

Almost without exception, a hormone affects its target tissues by first forming a

hormone receptor complex

ion channel linked hormone receptors are specific for

neurotransmitters

________ are proteins that pass through the membraneonly once, in contrast to the seven-transmembrane G protein–coupledreceptors

enzyme-linked receptors

moa of steroids

diffuse into cytoplasm, binds to receptor → nucleus, on dna, translation at ribosomes → new proteins formed

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The thyroid hormones thyroxine T4 and triiodothyronineT3 have similar pathways as

steroids

feature thyroid hormone fxn in nucleus

activate genetic mechanisms for intracell proteins, prolonged activity

pituitary gland is connected to hypothalamus by

pituitary stalk

parts of pituitary

adeno/ant, neuro/post, pars intermedia

2 embryological sources of pituitary

ant from endoderm, post from ectoderm

anterior pituitary function

secreting cells controlled by hypothalamic hormones, secreted within hypothalamus and conducted to vessels thru hypothalamic-hypophysial portal vessels,

posterior pituitary fxn

hormone release int magnocell neurons, controlled by nerves signals from hypothalamus

_____ is secreted by somatotrop cells and is the msot abundant pituitary hormone

GH

release pattern of GH

pulsatile, stimulated by deep sleep and high in newborns

GH moa

by itself and by somatomedins (insulin-like)

GH vs IGF I

GH is released rapidly, IGF I is released slowly

GH effects

increased rate protein synthesis, use of fatty acids from fat, decreased rate glucose use

_________ maintains skeletal architecture and bone mass

GH stimulating IGF-I

GH regulation

stimulated by GHRH, inhibited by SST + neg feedback of GH and IGF-1

regulation prolactin

inhibited by dopamine, increased in nipple stimulation, TRH, estrogen

effects somatostatin

inhibits GH, TSH, insulin, glucagon, gi hormones

reduces gastric acid and pancreatic secretion

high prolactin causes

lactation (fall progesterone) or inhibited gonadotropin (infertility)

signaling pathways of adh

osmoreceptors in AVP, baroreceptors in aorta and carotid

stimuli adh

increase plasma osmolality, hypovolemia, stress/cortisol

how do thyroid hormones act

bind to nuclear receptors and regulate transcription of cell proteins (they are steroid like, not peptides)

how are iodides ingested

orally, absorbed from git (similarly to chlorides)

thyroid hormone formation

1. iodide trapping - (by high TSH), transported by pendrin thru na+-iodide symporter of thyroid cell, also bind to thyroglobulin
2. iodide oxidation → iodine, by peroxidase
3. iodination of tyrosine “organification” of thyroglobulin - bidning iodine with thyroglobulin
4. coupling - iodination of tyrosine causes T4 (by DIT joined), T3 (by MIT + DIT), RT3 (DIT + MIT)

why does thyroid hormone synthesis stoppage only can be observed after several months

stores of thyroid hormones in follicles for a few months

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effects thyroid hormones

* growth (skeletal, brain)
* increased BMR - carb, protein, fat metabolism stimulation
* vasodilation (→ increased CO, HR), increased respiration
* increased digestive juices and motility
* increased cerebration rapidity
* mineral, CTCH and vitamin metabolism stimulation

Thyroid hormones, attached to Tg inthe follicular lumen remain inactiveuntil

the iodinated Tg is hydrolyzed

_____ are not released into blood, released as free hormones only when cleaved from thyroglobulin

t4, t3

secretion t4 vs t3

t4 mostly secreted, but in a few days t4 deiodinated → t3 in tissue

tbg, albumin and ttr are

thyroid binding hormones

Only___________ in the circulation is responsible for the actions of the thyroid hormones on their target tissue

unbound/free hormones

which thyroid hormones binds more strongly at tissue level with intracell proteins

t4

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Increased onset latency and the prolonged period of action of thyroid hormones are caused by

protein binding in plasma and tissue cells

slow release

why does t3 have greater biological activity

* t4 bound more tightly to plasma proteins
* target cells convert some t4 to t3
* TR in nucleus has more affinity for t3

3 levels of thyroid control

hypothalamus, pituitary, thyroid

_________ is a peptide which is synthesized by neurons in the paraventricular nucleus(PVN) of the hypothalamus and secreted from their nerve endings in themedian eminence of the hypothalamus → adenohypophysis

TRH

TSH effects on thyroid

increased thyroglobulin proteolysis, activity of iodide pump, iodination of tyrosine, secretory activity of thyroid cells, # of thyroid cells