into to endo vallano Flashcards
hypothalamus
releases releasing factors which are usually excitatory: TRH, CRH, GnRH, GHRH.
Inhibitory: Somatostatin and dopamine
placenta
secretes: estriol, progesterone, HCG (human chorionic gonadotrophin- a peptide that stimulates corpus luteum to produce estrogen and progesterone early in pregnancy) and HPL (human placental lactogen- peptide with growth hormone and prolactin like actions)
properties of different classes of horomones
peptide, steroid, and amino acid hormones.
- peptide and amino acid (minus thyroid hormones) hormones are hydrophillic in blood so they can travel on their own.
- steroid hormones (and thyroid amino acid hormones) are hydrophobic so they need a carried to move around in blood.
- peptide hormones have a shorter half life and steroid hormones live longer bc theyre bound to something in plasma.
steroid vs peptide/amino acid hormones
- steroid hormones do not have as storage pool. they are produced on demand. thyroid hormones are exception. peptide and amine hormones are stored ins secretary vesicles.
- steroid hormones dont need to interact w/ the cell membrane bc it diffuses right through it and binds receptor in cytoplasm or in nucleus. peptide and amine hormones bind to receptor on the cell membrane.
- steroid hormones effect is to regulate gene transcription. it takes then hours to days to achieve their activity. peptide and amine hormones effect is exerted through signal transduction cascades and affect various cell processes. takes them seconds to minutes.
psuedohypoparathyroidism
promary disease is disease of the gland itself. secondary disease is when something is wrong in regulation. in pseudohypoparathyrodism, you have a defect in the alpha subunit of the g protein. impairs ability of the PTH to regulare calcium and phosphorus. you end up with low Ca level and high phosphate;; just like pateints with parathyroids that have been removed. if you look in their blood through, they have noral level of PTH so you know its a receptor problem.
hypothalamus and pituritary secrete hormones cyclically throught the day
- increase release of growth hormone (GH) under strenuous exercise and during the first couple hours of sleep.
- if you’re going to sample blood for a hormone, need to take several samples to find regular level.
anterior pituitary has vascular connections with the hypothalamus
hypothalamus in the median eminence has axons that synapse onto the a capillary plexus in the anterior pituitary. its a venous system that feeds the anterior pituitary, w 5 cell types and 6 types of hormones released.
hypothalamus makes neural connections with the posterior pituitary
so cell bodes are in the hypothalamus, but the axons are in the posterior pituitary.
-has 2 nuclei: paraventricular nucleus which releases mostly oxytocin and supraoptic which releases ADH/vasopressin.
hypothalamus anterior pituitary relationships
- GHRH is released from hypothalamus. it is inhibited by somatostatin. it triggers somatotroph cells in anterior pituitary to release GH.
- TRH from hypothalamus acts on thyrotroph cells in anterior pituitary to release TSH.
- CRH acts on corticotrophs to release ACTH.
- GnRH acts on gonadotroph to release FSH or FH.
- hypothalamus releases one tonic hormone, dopamine, that tonically inhibits lactotrophs from releasing PRL. soo, prolactin would always be secreted in not for dopamine.
hypophyseal portal circulation
the circulation between hypothalamus and anterior pituitary. hypothalamus can release hormones into there and it’ll go to anterior pituitary without having to go into general circulation.
-under a microscope, you can distinguish b/w the 5 cell types in anterior pituitary based on size and color. the territories are dynamic, they change size and activity based on input like pregnancy and lactotropes.
feedback
peptides that feedback on hypothalamic pituitary axis pass blood brain barrier.
- long loop feedback: feedback from peripheral glands onto hypothalamic pituitary axis
- short loop: anterior pituitary feeding back to hypothamus
- hormone to target gland can feedback on both the anterior pituitary AND the hypothalamus
- positive feedback: in late follicular and ovulatory phase in menstrual cycle, high estradiol level cause a greater secretion of hypothalamic releasing hormone and trophic hormonecauing a surge of pituitary hormone that causes ovulation midcycle
Prolactin-milk production. also promotes breast development in puberty and pregnancy and inhibits ovulation.
prolactin is different from other anterior pituitary hormones bc its under tonic inhibition by domapmine. so, circulating prolactin will increase if you break the stalk bc domapine wont be able to exert its affect.
- hypothalamus to anterior pituitary: releases dopamine which inhibits prolactin and TRH (thyroid hormone) which stimulates it.
- prolactin feedbacks to hypothamus and causes more dopamine relase.
- if pituitary stalk severed, or someone is taking a dopamine receptor antaginist, prolactin increases.
- excessive prolactin secretion is treated with dopamine agonist.
posterior pituitary hormones
are made from prepro hormones in large neuronal cell bodies in hypothalamus and stored in nerve terminals in posterior pituitary.
-you can meausure neurophysins as a marker to ADH or oxytocin release
oxytocin- promotes release of milk. prolactin is for production of milk
suckling is reflex. stimulates PVN paraventricular nuclei in hypothalamus (posterior pituitary).
-also releases with uterine contractions in response to dilation of cervix
ADH from supraoptic nuclei
- ADH secretion increases in response to dehydration/volume contraction and decreases with volume expansion
- V2 receptors in kidney for reabsortion.
- V1 for increasing peripheral resistance and contract smoothe muscle
- if posterior pituitary cant secrete ADH you gen central diabetes insipidus. lareg volume of dilute urine. concentrated body fluids.
