endocrine- basics Flashcards
endocrine vs exocrine
exocrine - secretes out a duct to lining outside of the body or inside the body (lining of organ)
endocrine-no ducts, secrete into EXTRACELLULAR FLUID and act on TARGET cells ->hormones (chemical messengers- to remote parts of body)
what is the manner in which most endocrine cells secrete their hormones? why does this matter for checking hormone levels?
Usually pulsatile in manner- something messes up homeostasis and they are secreted to restore it
—> so ordering random hormone level is useless.
which endocrine gland is the only one that does NOT secrete in a pulsatile manner?
thyroid
what causes secretion of hormones? what causes inhibition of hormone secretion?
secretion: Disruption of homeostasis
inhibition: Restoration of homeostasis (reduction of stimulus) AKA “Negative feedback”
what are the two ways in which hormones can circulate? how is the majority of it circulating?
free (biologically active)
or protein bound (majority)
what does “trophic” mean?
the hormone stimulates a target cell and activates secretion of ANOTHER hormone from that gland
(AKA induces second messenger secretion)
what are the three types of hormones?
proteins (peptides)
steroids
amines
protein hormones: water or lipid soluble?
make up the majority of hormones
-are water soluble
steroid hormones: what are they derived from? water or lipid soluble?
derived from parent molecule: cholesterol
- all lipids
what is the significance of steroid hormones all being lipids?
CAN cross cell membrane, but don’t dissolve in plasma well- need carriers for plasma
amine hormones: what are they derived from? water or lipid soluble?
Derived from amino acid- tyrosine
tyrosine has ring that makes it resemble lipid, so these are relatively lipid soluble.
what two groups are included in the amine hormones?
thyroid hormone + catecholamines
which hormones act on intracellular receptors?
Steroid (& thyroid) : b/c pass through membrane easily
which hormones act on membrane receptors?
Protein & amine (except thyroid): b/c can’t pass through membrane
Require second messenger system- (change what goes on inside the cell = effect)
how does the 2nd messenger system work?
- Hormone (first messenger) does not enter cell - acts on membrane receptor
- Hormone-receptor binding triggers increase in an intracellular molecule/ion (second messenger)
- Second messenger orchestrates cellular effects, generally rapid
2nd messenger system: 1st + 2nd messenger- Linked by _____ in cell membrane
G-proteins
what are two 2nd messenger systems that we care about? and the other two?
cAMP (most common for h2o soluble hormones)
Phospholipase C
(also tyrosine kinase + cGMP)
what is the most commonly used 2nd messenger?
cAMP
what are the steps of the cAMP system? (7)
- Hormone binds receptor
- Receptor activates G protein
* 3. Activated G protein activates adenylate cyclase
* 4. Adenylate cyclase converts ATP to cAMP
* 5. cAMP activates protein kinase A - Protein kinase A phosphorylates cellular proteins
- Phosphorylated proteins alter metabolic activity of cell
cAMP system: Increase in cAMP level is usually short or long? _______ converts cAMP to AMP?
- short-lived
- Phosphodiesterase (PDE)
what does the word “kinase” indicate?
phosphorylation (adding a phosphate group)
what are the steps of the phospholipase C system? (8)
- Hormone binds receptor
- Receptor activates G protein
* 3. Activated G protein activates phospholipase C
* 4. Phospholipase C cleaves PIP2 into DAG & IP3
* 5. IP3 causes Ca+2 release from endo(sarco)plasmic reticulum
* 6. DAG & Ca+2 activate protein kinase C - Protein kinase C phosphorylates cellular proteins
- Phosphorylated proteins alter metabolic activity of cell
steroid and thyroid hormones diffuse into target cell, then bind to what 3 possible receptors?
steroid: Bind to nuclear + cytoplasmic
thyroid: bind nuclear + mitochondrial
what are the actions of steroid + thyroid hormones once bound to cytoplasmic, nuclear or mitochondrial receptors?
cytoplasmic + nuclear: binds DNA, alters transcriptions- mRNA translated into new proteins
mitochondrial: alters mitochondrial activity = increased ATP
what is different from the effects of steroid and thyroid hormones compared to other hormones (that use 2nd messengers) ?
steroid + thyroid: Effects take longer to occur BUT the effects last longer as a result
how does the tyrosine kinase system work?
same as cAMP and phospholipase C system…
2nd messenger system- phosphorylation of intracellular proteins = effect on target cell.
what are the two types of activity that hormones receptors may have with tyrosine kinase? (examples of each?)
Some hormone receptors have intrinsic tyrosine kinase activity (i.e. Insulin)
Some hormone receptors are associated with tyrosine kinase enzymes (i.e. Growth hormone)
mutated tyrosine kinase often result in what?
cancer.
think of growth hormone that is assoc. with tyrosine kinase enzyme
negative feedback may be ____ or ____, may involve ____ or _____ mechanisms
Can be direct or indirect
May involve neural or humoral mechanisms
define “up-regulation”
Up-regulation: increase in receptor number, usually in response to decreased hormone levels
–> Increases sensitivity to hormone
define “down-regulation”
Down-regulation: decrease in receptor number, usually in response to increased hormone levels
–>Decreases sensitivity to hormone
what are the 3 mechanisms of endocrine control that the hypothalamus initiates?
- Produces & transports hormones to posterior pituitary gland for secretion
- Secretes regulatory hormones that control activity of anterior pituitary gland
- Contains cell bodies of sympathetic neurons that stimulate adrenal medulla
what are the two anatomic relationships of the hypothal. to the pituitary ? both course through where?
neural and vascular
- both course through infundibulum
what is the neural relationships of the hypothal. to the pituitary? which lobe?
Neuron cell bodies in supraoptic & paraventricular “nuclei” (groups of cell bodies)
-Posterior lobe
what is the vascular relationship of the hypothal. to the pituitary? which lobe?
Hypothalamic-hypophysial portal system of capillaries
-Anterior lobe
Neuron cell bodies in supraoptic nucleus primarily produce what hormone?
Neuron cell bodies in paraventricular nucleus primarily produce what hormone?
- supraoptic (produces ADH/vasopressin)
- paraventricular (produces oxytocin)
a collection of cell bodies in the CNS is called what? (weeds)
“nucleus”
post. vs anterior pituitary: which is an actual gland?
post pituitary not an actual gland- just contains the nerve endings from the hypothal -neuronal relationship
ant pituitary - gland - hormonal relationship (hormones travel in portal system via veins)
ADH/oxytocin transported via ___ for secretion into where?
via axons, secretion into hypophyseal veins in posterior pituitary.
Hypothalamic neurosecretory neurons produce what two kinds or hormones? where are they released into?
releasing hormones (RH) and release-inhibiting hormones (RIH) BOTH into hypothalamic-hypophysial portal capillaries
RH and RIH from hypothalamic neurosecretory neurons have what function?
Control secretory function of anterior pituitary endocrine cells
