lecture 6: Metablism 4 (endocrine system 1) Flashcards
what’s the primary aim of the endocrine system?
to maintain a stable and balanced internal environment (homeostasis)
what’s the difference between the nervous and endocrine system in terms of responses
NS releases fast acting neurotransmitters, while the endocrine system releases slower acting hormones into the bloodstream and interstitial fluid
what do exocrine glands do? what are the exocrine glands?
secrete products (not hormones) into ducts and are expelled outside of the body
sudoriferous (sweat) glands
sebaceous (oil) glands
mucous glands
digestive glands
exocrine hormones do not secrete ____?
hormones!!!
what’s the overall method of both endo and NS?
to have signals
neurotransmitters in the NS
hormones in the endocrine system
how do hormones/neurotransmitters initiate a response?
they bind to receptors on target cells
how does signaling by hormones differ from signaling by neurotransmitters?
hormones circulate around but target specific cells
- receptor shape is specific to the hormone
NT act on cells (in and around)
where do hormones bind?
they target specific organs/tissues where they bind to specific protein receptor cells which are molecules embedded in the membrane or cytoplasm of cell
what do the activated cells do
they develop and act in certain ways based on the signal transmitted by the hormone
what do hormones determine?
- the development if sexual characteristics in puberty
- regulate how the body grows and develops
- how the body controls fluid, salt and sugar levels in the body
if men and women have both estrogen and testosterone, then what determines the secondary sex characteristics?
the level of these hormones
- depends on the amount of receptors that accept the release
what are the three main pathways hormones have for action
travel in blood and act on distant target cells (circulation hormones; endocrines)
act on neighbouring cells (paracrines)
act on the same cell that secreted them (autocrines)
what is a good example of autcrocrines?
the immune system:
- needs local regulation to bring WBC (cell to cell communication)
what are the lipid soluble hormones? What is their role?
steroid, and thyroid hormones, nitric oxide
- circulate bound to transport portines
- diffuse across the plasma membrane
- bind to receptors within target cells
- activate genes to allow ribosomes to synthesize specific proteins
what are the water soluble hormones, what do they do?
cannot pass thru the membrane so they bind to receptors on the membrane:
amine hormones, peptide and protein hormones, eicosanoid hormones)
- circulate freely in the plasma
- activate a secondary messenger to phosphorylate cellular proteins
what does it mean to phosphorylate
turn receptors “on” or “off”
- activates (excitatory)
- inactivates (inhibitory)
what happens when a receptor is activated?
it results in the production of proteins through a chain reaction
how can hormone regulation be controlled
through alterations to the receptors themselves
how can receptors be up-regulated/down-regulated? what does this mean
up-regulated - become more sensitive in the presence of low concentrations of hormone (more receptors)
down-regulated - become less sensitive in the presence of high concentrations of hormone
why would we want receptors to be upregulated/down-regulated?
tissues get different levels of hormone because this allows them to have a more invidiulaistc regulation
- we want one tissue to be up-regulated and another to be down-regulated
the response of a target cell to a
hormone is based on…
- hormone/s [] in the blood
- the # of hormone receptors on the target cell
- and influences exerted by other hormones
how would a hormone exert its influence on another hormone?
synergistic effect
antagonistic effect
t/f hormones are released all at once
f they’re released in short bursts, to prevent over/underproduction of the hormone
how is hormone secretion regulated?
- chemical changes in the blood
- signals from the nervous system
- other hormones
the ES relies on feedback systems to recluse hormone production/secretion
mist endocrine glands are under which feedback control? what does this allow
negative.
prevents deviation from a set point in the body
positive feedback mechanisms control?
self-perpetuating events
- release of stimulus builds upon itself so you need an external break to stop the pathway
positive feedback encourages a response ___ the body’s set point
away from
positive feed back are much less common. what is an example of them?
release of oxytocin during childbirth
what is one of the most important functions of the hypothal. what are its most important roles
to link the nervous and endocrin systems
controls homeostasis for body temp, blood glucose levels and osmotic pressure
how many hormones are leased by the hypo. what do they basically do
TRH, CRH, GnRH, PRH, GHRH (aka. somatocrinin)
they drive the ES by telling the pituitary glans which hormones to release
why do we have releasing hormones? couldn’t the hypo. just directly secrete hormones to the target organs/tissues?
hormones are separated from systemic circulation; they are controlled by the release into the pituitary gland without immediate dilution into the bloodstream
- similar to the blood brain barrier, the brain is protected from hormonal fluctuations that could disrupt its function
hormones released from the hypothalamus can also be inhibiting hormones. what are examples of inhibiting hormones? what does they do?
GHIH (somatostatin), and PIH (dopamine)
tells pit. not to release hormones
The hypothalamus
and pituitary gland
are connected by the ____. how do hormones reach the pit.
infundibulum (stalk)
via the hypophyseal portal system
ant. pit. aka ____, makes up —-7. of the weight of pit. how many cells are within it and how many hormones does it release
adenohypophysis
75%
5 types of cells and they secrete seven hormones
what are the ant. pit. hormones and what are they secreted by?
hGh secreted by somatotrophs
PRL secreted by lactotrophs
TSH secreted by thyotrophs
FSH & LH secreted by gonadotrophs
ACTH & MSH secreted by corticotrophs
what’s the most plentiful hormone released by ant. pit.? what does it do? what is it controlled by?
hGh; aids in growth of muscles and bones
controlled by 2 hyp. hormones:
- GHRH
- GHIH
if one was giving Gh what parts of the body will grow bigger out of proportion?
nose and ears cuz they’re made of cartilage not bone
what’s the role of TSH? what’s it controlled by? what abt prolactin?
stimulates the production of thyroid hormones from the th gland and is controlled by TRH
PRL with other hormones initiates and maintains milk secretion by the mammary glands
role of FSH & LH
in females FSH initiates follicle development and secretion of estrogens in the ovaries
in males, FSH stimulates sperm production in the testes
LH in females stimulates the secretion of estrogens by ovarian cells to result in ovulation and stimulates formation of the corpus luteum and secretion of progesterone
in males, stimulates interstitial cells of testes to secrete testosterone
roles of acth
controls the production and secretion of glucocorticoids by context of adrenal gland
what is the posterior lobe, aka ___, made of? what does it do?
neurohypophsyis
made of neural tissue
does not release any hormones, but stores:
- OT, and ADH
what is the role of oxytocin? when is it released
released in response to stretch placed on the cervix during childbirth
- it enhances contractions of mother’s uterus
- stimulates milk production by the mammary glands in response to suckling
- in males, aids in the dopamine-OT-NO pathway for erections
the amount of ADH secreted varies with ___ ____? what are its roles
osmotic pressure
ADH decreases urine output as part of a negative fb loop where osmoreceptors in the hypothalamus monitor blood OP
and incr./decr. in bv does what to ADH
incr = in bv causes a decr in ADH secretion
decr in bv cause an increase in ADH secretion
what is the relationship between alcohol and ADH
alcohol inhibits adh - acts on the hormone not the kidneys causing you to produce more urine
