Homeostasis Flashcards by Nathan Hansen

Living orgs must maintain a

Internal enviro composed of

Homeostasis is the dynamic ____ of the internal enviro

steady state

physiological variables that fluctuate around a set point

Body temp, blood volume, Bp

constancy

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Small changes are _____ taking place ot correct ____ that threaten normal fxn

loss of homeostasis leads to

Input signal sent from, detects

Controller usually is

Purpose

Output signal sent by

Returns variable to

constantly, distruptions

sensor/receptor, change

nerve/endocrine cell

evaluate info, initiate a response

effector cells

homeostatic range

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Homeostatic values have

achieve steady state over

requires

Homeostasis maintained by

____ variable when too high

_____ variable when too low

set range of physio values

long term

energy

Negative feedback loops

dec

inc

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Neg feedback control of BP

occurs via ___

changes in

Mediated by

hormone alteration (RAAS)

peripheral vasoconstriction
and urine output (blood volume)

aldosterone from AC

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Neg feedback control of glucose

Insulin ___ glucose levels when exceed homeostatic range

Glucagon ____ glucose levels when they fall below homeostatic range

Endocrine signals reach target via (ex)

Neural signals reach target via (ex)

Neuroendocrine combo of _____, ex

these are ____ responses

dec

inc

blood (glucose/insluin)

nerves (Knee jerk reflex)

neural/endocrine (hypothalamic AP axis)

distant

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Local responses

Paracrine signals reach

Autocrine signals affect

Signals can act at

such as

neighboring cells via ISF

cell generating the signal

multuple levels

cortisol- affects cell it is made in, nearby cells, distant targets

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Feedforward regulation is

No ____ required

_____ response

Minimizes

anticipatory (proactive)

deviation

accelerates

fluctuation

circadian rhythms, salivation

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Neg feedback is a ____ reflex

Feedforward regulation ___ speed of homeostatic response

Positive feedback ___ signal

Not a

Requires ____ to terminate

example

homeostatic

increases

amplifies

homeostatic control mech

external factor

parturition

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Endocrine system fxn unit

chemical messenger

mode of transmission

Rxn time

gland cell

hormone

circulation

Min- day

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General fxn of hormone

maintain ___ of internal enviro

adapt to changes in

control processes involving multiple tissues such as

internal environment

external enviro (food availability, response to stress)

Ion/fluids, energy metabolism, digestion, growth, repro

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Hormones are secreted by

released into

Regulate, do not ___, fxn in

Exert effects at

Regulate things such as

At molecular level, can inflence

specific cells

bloodstream in small amounts

initiate, target cells

cellular level

cell division, differentiation, ativation, motility, secretion

gene trxn, protein synthesis, enzyme activity, protein interactions

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Chemical signalling types

a single gland can

hormones can be produced by

types of hormones

autocrine, paracrine (AC), endocrine, Neuroendocrine (hypothalamic hormones regulating AP)

secrete multiple hormones (AP)

more than 1 gland (somatostatin)

Tyrosine derivative, steroids, proteins, peptide

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Tyrosine derivatives

catecholamines produced by adrenal medulla and CNS

iodothyronines produced by thyroid gland

DA, NE, Epi

T3, T4

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Steroid hormones

AC- A, C, A

Gonads T, E, P

Placenta P, E

Kidney, C (aka)

Aldo, Cortisol, Androstenedione

Testosterone, Estradiol, Progesterone

Progesterone, Estrogens

Calcitriol (VD3)

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Characteristics of Steroid hormones

derived from

water _____, transported in blood when

____, so cross membranes

Receptors located

Gland storage ____, bc

can be administered

cholesterol

insolubule, bound to protein

lipophilic, easily

minimal, diffuse easily out of cells

orally

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Protein hormones

Hypothalamic releasing G, C

Pancreatic islet hormones

P____
C_____
Placental, such as

GHRH, CRH

Glycoproteins (alpha/beta subunits, beta for specificity)- LH/FSH/TSH
GH, PRL, ACTH

insulin, glucagon

PTH
Calcitonin

hCG

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Peptide hormones

Hypothalamic releasing/inhibit hormones G, T, S, G

Posterior pituitary hormones O, A

Others

GnRH, TRH, Somatostatin, GHIH

Oxytocin, ADH

Angiotensin, MSH

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Characteristics of peptide/protein hormones

Synthesized on, as

Stored inside cells in

Often circulate

relatively

Receptors are

Cannot be administered, bc

ribosomes, prehormones/pre-prohormones

membrane bound granules

unbound

polar

orally, digested

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Protein/peptide hormones life cycle

Trxn/processed in

TRxn factors bind to

Processing can occur

Processed mRNA enters

nuclues

DNA at specific sequences encoding a hormone

post transcriptional

cytoplasm

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Processing of peptide/proteins occurs in, stored in

stage, mRNA in ribosomes binds peptide chain, directed to lumen by

enzyms in ER chop off _____, creating

prohormone goes through ER to _____, where ___ occurs

Secretory vesicles then bud off _____, enzymes cleave _____ into active _____

when signal for release occurs, secretory vesicles relase via ___, itno

hormone then goes to

ER/Golgi, secretory vesicles

(preprohormone),signal sequence

signal sequence, inactive prohormone

Golgi, final processing/glycoslyation

Golgi, promhormone, hormone

exocytosis, EC space

target

Life cycle of steroid hormone

Synthesized via

Rate limiting enzyme is, converts ____ to pregnenolone

Similarity of structures leads to

defect in one enzyme can result in

cholesterol, special enzymes

side chain cleavage enzyme (P450), cholesterol

cross reactivity at pharm levels

dramatically altererd hormone products

Hormone life cycle

Secretion for Proteins/Peptide
Steroids/Thyroid

Transport of catecholamines/proteins/peptides

exception is, transpoted when boudn to

Steroid/thyroid hormones are ____, circulate when

Only ____ portion is biologically active

Exocytosis
Diffusion

Free/unbound (hydrophilic)

GH/IGF, proteins

lipophilic, binding proteins

free

Binding proteins synthesized and sec by, circulate in

binding affinity of these proteins is ____ than albumin, rendering

concentration of bound hormone, free hormone, binding protein exist in

dec in free hormone results in

bound hormone serves as ___ of readily avaliable hormone

bound hormone is not ____ for metabolism, thus binding protein _____ hormone’s half life

Liver (CBG, TBG, SSBG), plasma

equilibrium

release of bound hormone from binding protein

pool

available, inc

Inc in binding protein in pregnancy due to

results in ____ bound hormone

briefly ____ amount of free hormone

rapidly returns via, resulting in

elevated estradiol levels

inc

dec

NFM, no net change

Chronic inc of plasma binding protein ____ in bound/total hormone no change in _____ bc of most assays measure ____ hormone level

inc free, NFM total

Receptors have ____ binding sites for homones this confers _____ as many hormones circulate in blood Protein/peptide hormone receptors are, bound to Protein/peptide hormones transmit signal via Signal transduction pathway

high affinity specificity EC, CM signal pathway hormone binds, induces conf change release IC 2nd messenger activates effector proteins, resulting in action

Signalling pathways ___ steps amplyify _____ activate multiple pathways of multiple cell fxns from Rapid action s in slower actions in antagonism by

multiple initial hormone/receptor binding one hormone bidning event cytoplasm nucleus constitutive and regulated NFM

IC messengers cyclic nucleotides such as, bind to released from Ions that lead to Lipid messengers DAG, which activates IP3 to inc both come from

cAMP, effector kinases (PKA/ion channels) AC/GC actication direct/indirect regulation of effector proteins PKC IC Ca Phospholipase C

GPCR (protein hormone receptor) Gs stimulates Gi inhibits Gq activates can affect result in release of

AC AC Phospholiapse C ion channels, enzyme activity, trxn PTH, LH, FSH, TSH, ACTH

Protein hormne receptors can Activate enzymes such as Tyrosine Kinases GF subtype Cytokine subtype Other type

gate channels (affect Ca) kinases/phosphatases receptor is tyrosine kinase receptor associated with kinase (JAK) serine/threonine

Steroid receptors are ___ acting than protein hormones, bc can be found on ____ for rapid actions structure included in Steroid receptors on ER/PR/GR/MR/AR suttle bw Thyroid/VD3/RA/PPAR are ___ bound in absence of hormone

IC, act as Trxn factors slower, action utilizes trxn/trsn PM nuclear receptors- bind DNA cytoplasm/nucleus nucleus to reponse elements gene trxn is inhibitied

Action of steroid receptors Hormone receptor complex binds to can activate/dec trxn by

specific DNA sequence called the hormone response element to alter trxn recruiting coactivators/corepressors

At the receptor, hormones inactivated via in plasma in kidney Half life is ____ correlated with metabolic clearance rate

enzyme degredation, dec conc of Ca, confomrational change in receptor, endocytosis enzyme degradation in blood/liver/kidney excreted negatively

Hypothalamic pituitary axis works via Estradiol induction of preovulatory gonadotropin surges works via

Neg feedback Pos feedback

Hormone action change in response via down regulation leads to up regulation leads t changes in sensitivity vua dec in sensitivity shifts DRC to changes can be, ie they can affect own/other hormone receptors

receptor number dec receptor number (result of high levels of hormone), downward shift of curve inc receptor number, inc shift of DRC receptor affinity right (more hormone required for response) homologous, heterologous

Endogenous parameters affecting hormone conc Most hormones manifest can be serum binding proteins an alter

multiple superimposed rhythms on secetory pattern diurnal, ultradian(pulsatile), responsive total hormone conc

Exogenous parameters affecting hormone conc act via Circadian rhythms rhythm occurs over even in constant conditions Normal period is Stress elevates blood levels, changing feedback set point to effect is superimposed on level of hormone is ______, but does not effect ______

CNS 24 hrs 24 hr HPA hormone release pattern inc, pattern of release

Neuroendocrinology is the interaction bw pituitary gland is the master bc structure includes

nervous/endocrine systems has so many endocrine reflexes anterior, endocrine lobe and posterior, neural lobe

PP is ___ tissue Comprised of ____ of the peptidergic neurosecretory neurons in the innervation is direct via ______ comosed of axons of ____ nucleus project down the ____ and terminate in ____ ___ and ____ hormones receives direct ____ bloody supply releases hormones into

axons/terminals, hypothalamus hypothalamohypophyseal tract supraoptic and paraventricular pituitary stalk, PP store/release (no synthesis) arterial systemic circ

Hormones of PP ADH released in response to Oxtyocin released in response to released into systemic circ via the targets are detectable in

hypothalamic osmoreceptors and CV volume receptors neural afferent input triggered by stretch of cervix at parturition, suckling of mammary glands venous drainage of PP distant peripheral blood

AP hormones Glycoproteins beta is GH/prolactin family POMC Family POMC is the _____ cleaved to become released w skin melanocytes cleave ACTH into

TSH, FSH, LH (alpha/beta subunits) unique GH, prolactin prohormone ACTH/ gamma lipotropin/ B endodorhin in anterior lobe aCTH A MSH (very similar to ACTH)

AP is glandular tissue N ____ innervation, ______ blood supply hormone release controlled by released at terminals near _____ in the median eminence at top of pituitary stalk transported to AP via Diffuse from secondary capillary plexus in AP to HH are ____ detectable in peripheral blood

direct, arterial HR and IH primary capillary plexus stalk portal capillaries target cells not

If pituitary stalk is cut, bc no other blood supply AP hormones will Prolactin (normally under chronic negative control) will if AP is transplanted and revascularizes what happens LH, FSH, TSH, GH, ACTH PRL AP gland is under constant

dec in blood inc until cells die/necrose frome lack of blood dec Inc negative feedback control

Panhypopituitarism leads to caused by can be if complete, plasma levels of hormones are HR hormone synthesis/sec will ___ due to lack of still will not be detected in

loss of all AP fxn destroyed gland- hemorrhage/adenoma partial/complete undetectable inc, negative feedback peripheral blood

Isolated PH deficiency loss of ____ hormone fxn Kallmans syndrome leads to

one GnRH neurons do not migrate from olfactory placode early in life absence of GnRH, dec LH, FSH, hypogonadism, anosmia

Sheehans syndrome results from portal capillaries operate at ____, thus are susceptible to low blood pressure Plasma levels of AP hormones will ____ due to Prolactin would initially ______, and eventually dec as cells die PP hormone levels would be ___ bc there is

postpartum hemorrhage low pressure, clotting/infarct/shock dec, loss blood supply of pars disalis inc unaffected, direct arterial blood supply

Pituitary gland found in, below, connected to brain via tumors can compress OC leading to Whiplash injuries sever complete stalk severing leads to Also leads to Lose

Sella turcica, optic chiasm, pituitary stalk HA/bilateral hemaniopsia stalk dec blood supply to AP- necrosis (no AP fxn- hypopituitarism) lost fxn of PP Oxytocin (asx), ADH (DI)

Tumors of somatotrophes (excess GH) Tumors of lactotrophes (excess prolactn) Tumors of corticotrophes (excess ACTH) Tumors of thyrotropes (Excess TSH) Tumors of gonadotropes (excess of gonadotropins) Tumor inc target hormone (inc Neg feedback, dec HR hormone syn)

Acromegaly/gigantism infertility, galatorrhea Pituitary Cushing's (hypercortisol) Hyperthyroidism in kids, precocious puberty tumors dont respond to negative feedback or dec in HRH