Homeostasis Flashcards
Living orgs must maintain a
Internal enviro composed of
ex
Homeostasis is the dynamic ____ of the internal enviro
steady state
physiological variables that fluctuate around a set point
Body temp, blood volume, Bp
constancy
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
dz
sensor/receptor, change
nerve/endocrine cell
evaluate info, initiate a response
effector cells
homeostatic range
Homeostatic values have
achieve steady state over
requires
Homeostasis maintained by
____ variable when too high
_____ variable when too low
Ex
set range of physio values
long term
energy
Negative feedback loops
dec
inc
BP
Neg feedback control of BP
occurs via ___
changes in
Mediated by
hormone alteration (RAAS)
peripheral vasoconstriction
and urine output (blood volume)
aldosterone from AC
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
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
Feedforward regulation is
No ____ required
_____ response
Minimizes
Ex
anticipatory (proactive)
deviation
accelerates
fluctuation
circadian rhythms, salivation
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
Endocrine system fxn unit
chemical messenger
mode of transmission
Rxn time
gland cell
hormone
circulation
Min- day
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
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
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
Tyrosine derivatives
catecholamines produced by adrenal medulla and CNS
iodothyronines produced by thyroid gland
DA, NE, Epi
T3, T4
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)
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
IC
minimal, diffuse easily out of cells
orally
Protein hormones
Hypothalamic releasing G, C
AP
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
Peptide hormones
Hypothalamic releasing/inhibit hormones G, T, S, G
Posterior pituitary hormones O, A
Others
GnRH, TRH, Somatostatin, GHIH
Oxytocin, ADH
Angiotensin, MSH
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
EC
orally, digested
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
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
