Exam 1 Flashcards
Hormone
produced by endocrine glands
acts on cells, tissues, or organs
facilitates/inhibits a physiologic process
broader level-whole body
endocrine gland
secretes within the body
usually into blood or lymph but there are some exceptions
endo=within
exocrine gland
secretes externally
has ducts to carry molecules to the exterior (ex: sweat, urine, mucous, etc…)
what purpose do hormones serve
integration purpose
how long does a neural pathway take
seconds
how long does an endocrine pathway
can range from minutes to hours and maybe even days
neuro-endocrine system
full integration of the two systems (nervous and endocrine)
examples of hormones regulating body functions
growth-growth hormone lactation-oxytocin estrous cycle-estradiol ovulation-luteinizing hormone parturition-oxytocin, relaxin
basic structures in the reproductive endocrine system
brain (hypothalamus and pituitary gland)
repro tract (female=uterus, ovaries; male=penis, urethra, testis)
HORMONES CONNECT BRAIN AND REPRO TRACT
three things to consider when looking at types of hormones
- site of production
- stimulatory or inhibitory
- structure (protein or lipid/small or large)
differences between a protein and a lipid
a lipid can directly enter a cell through a bilayer. Lipid hormones, like steroids, have to be carried through on carrier proteins. Cannot be released as free floating molecules to get to the next location. EX: testosterone and estradiol
A protein needs help passing through the cell bilayer by using a receptor. Hydrophilic molecules that can be released as free floaters to get to their next location. EX: luteinizing hormone
glycosylation
when a molecules is glycosylated it means sugars are added
glycos=sugar
glycosylated hormones increase the half-life in circulation. Happens with proteins. Sugars are added to the protein between the ER and the Golgi Apparatus to make the protein glycosylated. Happens within the cell that is producing the hormone
why does it matter if hormones are large or small?
large tend to stay in circulation longer and have biological effects
small are easily degraded
describe the location of the hypothalamus and the pituitary glands
they are very small and are in the part of the brain that is very protected
describe the structure of the pituitary gland
it has two sections: the posterior pituitary and the anterior pituitary
posterior pituitary=made up of true neuroendocrine tissue. AKA neurohypophysis
anterior pituitary=made up of vascularized tissue which means it is rich in blood supply. It has a capillary plexus which is a closed capillary network. AKA adenohypophyis
located above the rook of the pharynx and is completely encased by bone (sphenoid bone) to protect it
describe the structure of the hypothalamus
located above the pituitary gland
made up of many different areas. We will focus on three:
PON: Pre-Optic Nucleus. Nucleus=cluser of neurons within the hypothalamus. GnRH surge control center.
ARC: arcuate nucleus. Nucleus=cluster of neurons within the hypothalamus. GnRH tonic control center/
ME: Median Eminence. Region of hypothalamus where a lot of neurons and their axons converge just before they make their way to the pituitary gland. Has a capillary plexus
master neuroendocrine gland
blood brain barrier
it prevents certain molecules from making their way from axons into the bloodstream or from the bloodstream into neural tissue (brain tissue)
prevention of moment starting in brain into bloodstream or vice versa
median eminence is one location where there is a lack of blood brain barrier. This is why when the neurons terminate the ME they can literally dump their contents into the bloodstream-which is what happens. GnRH dumps its contents into the bloodstream at the level of the median eminence
functions of the hypothalamus include
appetite thirst body temperature vasomotor activity emotion use of body nutrient reserves activity of intestine sleep sexual behavior production and secretion of reproduction releasing hormone. Releasing hormones are going to find a target tissue and stimulate the secretion of something else.
hypothalamic hormones
site of production=hypothalamus-GnRH
GnRH=gonadotropin releasing hormone. Action is to affect downstream hormones to release them.
GnRH=stimulatory
Growth inhibitory someone (somatostatin)=inhibitory
structure and size: short chain polypeptides (3-44 amino acids). Polypeptides=protein hormones. Small=shorter half life, won’t remain in circulation for long before destroyed
why did pharmaceuticals create synthetic GnRH hormones
natural GnRH hormones have an easily degraded structure (at sites 5-6 and 10). The synthetic hormone fixes this problem and makes them less vulnerable to degradation. The synthetic GnRH are more potent and last longer and has stimulatory affects on ovulation
follicle stimulating hormone
stimulates the ovary and testis
luteinizing hormone
stimulates ovulation in the ovaries and steroid production in the ovary and testis
Glycosylation of FSH and LH
FSH and LH makes sense tone glycosylated because they have to travel father to the ovary and testis and need to last in the body to reach and affect
FSH and LH are heterodiemers. what does heterdiemer mean?
Hetero=two different kind of subunits (one is alpha and one is beta)
Diemers=two subunits combined
FSH and LH have the same alpha subunit but they differ in their beta subunits which gives them their specificity by targeting with receptors within the tissue to cause specific responses
how does GnRH travel to the anterior pituitary to release LH and FSH?
GnRh from the pre optic nuclei in the hypothalamus gets dumped into the blood supply at the median eminence through axons and makes its way to the anterior pituitary causing the release of LH and FSH by affecting the cells that release LH and FSH
gonadal steroids refer to
estrogen
progesterone
testosterone
importance of the superior hypophyseal artery
capillary plexus found in the median eminence
coming from the general circulation and bringing oxygen and nutrients to this whole system
importance of the hypophyseal portal vessels
still have oxygenated blood and nutrient blood
this blood makes its way to the secondary capillary plexus
consists of enzymes (endopeptidases and carboxypeptidases) both have the net affect of degrading proteins that are in the blood supply
How do Oxytocin and ADH reach the posterior pituitary?
the cluster of neurons that provide hormones to the posterior pituitary are the supraoptic nuclei and the paraventricular nuclei. they travel all the way into the posterior pituitary and dump their contents (oxytocin and ADH) directly into the circulation via the capillary plexus
cholesterols synthesis to estradiol
once cholesterol enters the gonads it goes through a sequence of enzymatic modifications to give us either estrogen/progesterone/testosterone
Step 1: cell obtains cholesterol from circulation. The rate limiting step for a cell producing steroids is for the cholesterol to make its way from the cytoplasm of the cell into the mitochondria. The STAR (steroid acute regulatory protein) molecule is responsible for the rate-limiting step and bringing cholesterol from the cytoplasm into the mitochondria key step for steroid synthesis
Step 2: start of enzymatic changes. Notice you go from a 27-C cholesterol to a 21-C Pregnenolone. The side chain gets clipped off by the enzyme P450 side chain cleavage (P450scc).
Step 3: Thehis is the conversion of 21-C pregnenolone to 21-C progesterone. 3 beta hydroxy steroid dehydrogenase (3B-HSD) takes the three position hydroxyl group and pulls it off converting it to a veto group.
(Pulling the hydrogen off is performed by the 3B-HSD)
Step 4: 21-C progesterone to 19-C testosterone. The steroids here are not important but know that this is a step.
Step 5: the 19-C testosterone is converted to an 18-C estradiol. The P450 aromatase enzyme (P450arom) takes the testosterone ring resulting in an aromatic ring to form in the spot
what steps of cholesterol steroid synthesis occur in the mitochondria?
cholesterol and pregnenolone
enzyme P450scc present here
what steps of cholesterol steroid synthesis occur in the smooth ER?
Progesterone, testosterone, and estradiol;
enzymes 3B-HSD and P450arom are present here
prostaglandins
another type of lipid derived hormone
all cells have the capability to create prostaglandins if they have the proper enzymes because they can make it within their membrane
PGE2 and PGF2
net effects of PGE2
vasodilation
maintain CL
ovulation
implantation
net effects of PGF2
vasoconstriction CL regression ovulation parturition sperm transport
protein hormones
hydrophilic
when they reach a target it needs to interact with a receptor on the cell-surface in order to have a downstream effect within the cell
the outer portion of receptor has sugars added onto it which react with the sugars on the glycoprotein hormone (LH/FSH) and when they interact they perform specificity and downstream effects for the receptor
broad ligament
connective tissue sheet
massive structure
supports and suspend the reproductive tract-suspended from the dorsal wall (back of animal) and reproductive tract hangs from this ligament
mesometrium
supports uterus
mesosalpinx
supports oviduct
mesovarium
supports ovary
ovary
primary sex organ
(bovine ovary=about 5-6 cm large)
hormonal=produce steroid and protein hormones
steroid: estrogen and progesterone
protein: anti-mullerian hormone, inhibit, activin
gametogenic: oocyte=egg=ova
follicles
found on ovaries
blister like projections
hormones secrete estrogen
houses the oocyte/egg and it is released from follicle during ovulation
corpus luteum
“yellow body”
lutein molecule gives it a yellowish tint
secretes the steroid progesterone which is responsible for maintaining pregnancy if an animal becomes pregnant
medulla
innermost region of the ovary
where there is nerve and blood supply
cortex
outermost region of the ovary
where follicles are found in various stages of growth and where the corpus lute is found
hilus
portion that connects to the mesovarium. blood and nerve supply goes through this to get to the ovary