Chapter 6-7 Flashcards
hormones act on their target cells by
- controlling rates of enzymatic runs 2. controlling transport of ions/molecules across membranes 3. controlling gene expression –> protein synthesis
endocrine system acts __ than the nervous system
WAY SLOWER
Arnold Berthold
rooster castration experiment, demonstrated that the testes secreted something in the blood that affected male development
Charles Brown-Sèquard
injected ground up bull testicle into his blood to “reinvigorate his manhood” probably a placebo effect, but paved way for organotherapy
immune system “hormones”
cytokines
nervous system “hormones”
neurohormones
not all hormones are secreted into the blood
ectohormones are secreted in the external environment Pheremones are a prime example of this
traditionally it is thought that hormones are transported to a distant target, but….
growth factors are secreted and act more locally there are autocrine and paracrine factors
eicosanoids
lipid derived signaling molecules
hormones exert their effect at very low concentrations
nM and pM concentrations but some are at way higher concentrations- histamine
Hormones act by
binding to receptors = cellular mechanism of action
Insulin in the muscle and adipose tissue
alters glucose in transport proteins and exzymes for glucose metabolism
insulin in the liver
modulates enzyme activity, no effect on glucose metabolism
insulin in the brain
glucose metabolism is independent of insulin
body will terminate hormone effect by
limiting secretion removing or inactivating secreted hormone terminating activity in target cells
in the bloodstream, hormones are degraded by
liver and kidney enzymes, excreted in bile or urine
hormone half life ___ if bound to protein
increases
enzymatic degradation of hormones bound to receptor can occur
at the membrane or in lysosomes
peptide/protein hormones
composed of linked amino acids
steroid hormones
all derived from cholesterol
amino acid-derived hormones (amine)
modifications of either tryptophan or tyrosine
most hormones are __ or __
proteins or peptides
Preprohormone (inactive
peptide hormone plus signal sequence that directs the protein into the RER
Prohormone (inactive)
Signal sequence cleaved, enzymatic activity in secretory vesicles cleaves prohormone into active hormone + peptide fragments
Active hormone + fragments (active)
Secretory vesicles released into extracellular space
Clinicians measure ___ to monitor pancreatic insulin production
C peptide
proinsulin is processed to insulin and cleaves off C-peptide. if you have a measure of C-peptide, you know how much active insulin is in the blood.
Peptide hormone properties
water soluble dissolve easily in ECF usually have short half life for continued response must be continually secreted
peptide hormone mechanism of action
lipophobic, so they are unable to enter a target cell they use receptors and signal transduction many work through cAMP second messenger system some have tyrosine kinase activity, like insulin usually elicit a rapid response
Steroid hormone properties
made in smooth ER diffuse easily across membranes because are lipophilic synthesized as needed, not stored for later use produced only in adrenal cortex, gonads, skin, , placenta
steroid hormones in the blood
not soluble in plasma most bound to carrier molecules protects from degradation–> longer half life, but also blocks from entry into cell tiny amounts can have a large effect
dissociation constant
[P] [L]/ [PL] P= protein L=ligand the ratio of bound to unbound hormone stays relatively constant
Steroid hormone action
ultimate destination is the nucleus.
act as transcription factors, not a rapid onset (genomic effect)
act as signal transducers, more rapid effect (nongenomic effect)
Melatonin
made from tryptophan originates in pineal gland circadian rhythm
Catecholamines and thyroid hormone
made from tyrosine
Catecholamines as a group
act like neuro-hormones that bind to cell membranes like peptide homrones
Thyroid hormones as a group
behave more like steroid hormones with intracellular receptors
Simple reflex pathway
Stimulus Sensor (endocrine cell) input signal integration of signal (endocrine cell) output signal (hormone) targets response (usually negative feedback)
simple endocrine reflex, PTH
2 endocrine structures are incorporated into the anatomy of the brain
pineal gland and pituitary gland NS and endocrine system are intertwined
catecholamines
a neurohormone made by modified neurons in the adrenal medulla
posterior pituitary
Oxytocin ADH secretes hormones made in the hypothalamus hormones stored in axon terminals until a signal is received
“neurohypophysis”
Oxytocin
secreted by posterior pituitary affects uterine muscles and mammary glands
ADH
secreted by posterior pituitary acts on kidney tubules
Anterior pituitary
“adenohypophysis” TRUE endocrine gland derived from embryonic tissue that formed the roof of the mouth
Secretes: TSH ACTH FSH LH GH PRL Endorphins
TSH
secreted by ant. pit acts on thyroid
ACTH
secreted by ant. pit acts on adrenal cortex
FSH
secreted by ant pit acts on testes or ovaries
LH
secreted by ant pit acts on testes or ovaries
GH
secreted by ant pit acts on entire body
PRL
secreted by ant pit acts on mammary glands
endorphins
secreted by ant pit act on pain receptors in the brain
Feedback loops in the hypothalamic-pituitary pathway
Three integrating centers: -hypothalamus -anterior pituitary -endocrine target of the hormone feedback signal are the hormones themselves
two different kinds of negative feedback
long loop and short loop short loop: prolactin, growth hormone, acth short- communication bw anterior pituitary and hypothalamus
synergism
frequently 2 or more hormones interact at their targets in a way that is more than additive
permissive homrone
allows another hormone to exert its full effect eg. thyroid hormone is permissive for reproductive system development Reproductive hormone w/o thyroid hormone= delayed development of repro. system
antagonistic hormones
have opposing effects usually when molecules compete for a receptor When one molecule binds the receptor but does not activate it = competitive inhibitor to the other molecule Functional antagonists if have opposing physiologic actions
hypersecretion
Exaggerates hormone’s effect cause: benign tumor cancerous tumor exogenous hormone, which can lead to atrophy of the endocrine gland that naturally produces the hormone
hyposecretion
Will see symptoms of hormone deficiency
Can occur anywhere along the pathway
Most common cause is atrophy of the gland due to disease
pineal gland
secretes melatonin to brain and other tissues to regulate circadian rhythm, immune function and acts as an antioxidant
hypothalamus
secretes tropic hormones to the anterior pituitary to release or inhibit pituitary hormones
posterior pituitary gland
secretes oxytocin and vasopressin to the breast and uterus and to the kidney to control milk ejection, L&D and to regulate water absorption
anterior pituitary
secretes prolactin, GH, ACTH, TSH, FSH and LH. has several primary targets and several functions
thyroid gland
secretes triiodothronine and thyroxine to many tissues to control matabolism, growth and development. secretes calcitonin to bone to regulate plasma calcium levels
parathyroid gland
secretes parathyroid hormone to the bones and kidneys to regulate blood calcium concentration and phosphate levels
thymus gland
secretes thymosin and thymopoietin to the lymphocytes to regulate lymphocyte development
heart
secretes atrial natriuretic peptide to the kidneys to increase Na+ excretion
liver
secretes angiotensinogen to the adrenal cortex and blood vessels to regulate aldosterone secretion and increase bp secretes insulin like growth factors to many tissues for growth
stomach and small intestine
secrete gastrin, secretin and others to the GI tract and pancreas to assist in digestion and absorption of nutrients
pancreas
secretes insulin, glucagon, somatostatin, pancreatic peptide to many tissues to regulate metabolism of glucose and other nutrients
adrenal cortex
secretes aldosterone to the kiddy for Na and K homeostasis secretes cortisol to many tissues to respond to stress secretes androgens to many tissues to regulate female sex drive
adrenal medulla
secretes epinephrine and norepinephrine to many tissues to regulate the fight or flight response
kidney
secretes erythropoeitin to bone marrow to regulate RBC production secretes calciferol to the intestine to increase calcium absorbtion
male testes
secrete androgens to many tissues to regulate sperm production and secondary sex characteristics secretes inhibin to the anterior pituitary to inhibit FSH secretion
female ovaries
secretes estrogen and progesterone to regulate egg production and secondary sex characteristics secretes inhibin to the anterior pituitary to inhibit FSH secretion
adipose tissue
secretes leptin, adiponectin and resistin to te hypothalamus to regulate food intake, metabolism and reproduction
most hormones are proteins or peptides
Preprohormone (inactive)
•peptide hormone plus signal sequence that directs the protein into the RER
Prohormone (inactive)
•Signal sequence cleaved, enzymatic activity in secretory vesicles cleaves prohormone into active hormone + peptide fragments
Active hormone + fragments (active)
•Secretory vesicles released into extracellular space
hypothalamus has direct control of __ by the nervous system
adrenal gland
hypothalamus has indirect control of tissues by the release of hormones to
the anterior lobe of the pituitary
anterior lobe of pituitary releases :
ACTH
TSH
GH
PRL
FSH
LH
hypothalamus has a direct release of hormones to ___
the posterior lobe of the pituitary
releases ADH and oxytocin
amine hormones/amino acid hormones
made from either tryptophan or trosine
insulin simple reflex pathway
anterior pituitary portal system
Portal system collects and concentrates hormones in anterior pit region and then are released to have a greater effect
Helps prevent them from being diluted or diverted away before the body can use them
Other portal systems are in the GI tract
anterior pituitary hormones control
growth, metabolism and reproduction
PRL and GH
only anterior pituitary hormones that have inhibitory proteins acting against them
Feedback loops in the hypothalamic-pituitary pathway
Three integrating centers:
–hypothalamus
–anterior pituitary
–endocrine target of the hormone
these feedback loops are complex and the feedback signals are the hormones themselves
control pathway for cortisol secretion
cortisol hypersecretion
trophic hormones can help to iosolate the location of the pathology
tertiary hypersectretion of cortisol happens in the hypothalamus (the sensor, the endocrine cell), have increased CRH
secondary hypersecretion of cortisol happens in the anterior pituitary (the integration center, the endocrine cell) , have increased ACTH
primary hypersecretion of cortisol happensin the adrenal cortex (the target), have increased cortisol.
This applies for substances other than cortisol.
