L2 hypothalamic pituitary axis Flashcards
what is the hypothalamus responsible for (5)
ANS, body temp, hunger, learning, breastfeeding, memory, circadian rhythm, emotional response, sexual arousal, growth, thirst, stress response
hormones from hypothalamus carried to what
anterior pituitary gland, via hypothalamic portal vein
pituitary gland size and location
pea sized, located in hypophyseal fossa in sphenoid bone
regions and functions of anterior pituitary
1 pars distalis (hormone production)
2 pars tuberalis (reception of endocrine signal)
3 pars intermedia (sheath between posterior and anterior)
regions and functions of posterior pituitary
1 pars nervosa (oxytocin and ADH)
2 infundibular stalk (bridge between hypothalamus and pituitary gland)
what hormone does somatotrope secrete
growth (GH)
what hormone does corticotrope secrete
adrenocorticotropin (ACTH)
what hormone does thyrotrope secrete
thyroid stimulating (TSH)
what hormone does gonadorope secrete
luteinizing (LH) and follicle stimulating (FSH)
what hormone does lactotrope secrete
prolactin
what are the inhibiting (statin) hormones released from hypothalamus
dopamine and somatostatin
what are the releasing/ stimulating (liberins) hormones released from hypothalamus
thyrotropin releasing (TRH), corticotropin releasing (CRH), gonadotropin releasing (GnRH), growth hormone releasing (GHRH)
inhibition/ stimulation of dopamine causes inhibition of
prolactin (Pr)
inhibition/ stimulation of thyropin (TRH) stimulates release of
prolactin (Pr) and TSH
inhibition/ stimulation of somatosin inhibits release of
TSH and growth hormone
inhibition/ stimulation of growth hormone releasinf hormone (GHRH)
stimulates release of GH
inhibition/ stimulation of gonadotropin releasing (GnRH)
stimulates release of FSH (follicle stim) and LH (luteinizing)
inhibition/ stimulation of corticotropin releasing (CRH)
stimulates release of adrenocorticotropic (ACTH)
effects of thyroid disorders due to thyrotropin releasing hormone (TRH)
1 metabolism issues due to changes in T3 and T4 levels
2 changes in activity levels
causes of thyroid disorder
1 changes in hormone concentration
2 tumours
what are the adrenocortical hormones
1 cortisol: carbohydrate metabolism and stress response
2 aldosterone: regulates salt and water homeostasis
3 androgen: male secondary sex characteristics, virilisation in female
pathway of corticotropin releasing hormone (CRH)
CRH produced in the paraventricular nucleus of hypothalamus into the anterior pituitary. stimulates corticotropes to release adrenocorticotropic hormone (ACTH). ACTH stimulates synthesis or cortisol, glucocorticoids, and mineralocorticoids.
what are the physiological actions of cortisol
- released in diurnal rhythm
- linked to light dark patterns and sleep
- important to seasonal breeding animal
increases synthesis of enzymes involved in hepatic gluconeogenesis - break down of fat and skeletal muscle to give energy
- FFAs (free fatty acid) released are used as substrate in liver for gluconeogenesis.
- NET RESULT: rise in glucose (hyperglycemia)
Cushings syndrome
a disorder of cortisol levels, caused by pituitary tumor, adrenal tumor, ectopic (lung tumor) or other external causes
what is aldosterone
it is a primary mineralocorticoid (influences salt and water balance) which controls the concentration and movement of Na+ K+ out of target epithelial cells. Stimulates active transport of Na+ in the epithelial cells of the DCT
Aldosterone’s mechanism of action
aldosterone increases the number of Na channels in the apical membrane and increases the number of Na-K ATPase molecules
what are the aldosterone induced proteins
SgK: serum and glucocorticoid-inducible kinase
CHIF: corticosteroid hormone-induced factor
Ki-Ras: Kirsten Ras
what do the aldosterone do
increase the activity and/or number of transport protein during the early phase of action
what happens during the late phase of aldosterone action
expression levels of transport proteins increase.
what is addisons disease
an aldosterone disorder caused by inadequate mineralocorticoids are produced, leading to symptoms like low BP, hyperpigmentation of the skin
gonadotrophin release
released from adrenals as weak precursors that are translated into more potent hormones by secondary endocrine glands. a very small amount is produced in comparison to the size of the gonadal tissue.
growth hormone
synthesized by somatotropin cells in the anterior pituitary
what is the indirect actions of growth hormones
secretion of IGF-1 from liver which stimulated bone growth, lipolysis, and protein synthesis in muscle.
what is the direct action of growth hormone
diabetogenic - opposes insulin ie lipolytic in fat and gluconeogenic in muscle
what are some growth factors
- epidermal growth factor (EGF)
- fibroblast growth factor (FGF)
- platelet derived growth factor (PDGF)
- erythropoietin (Epo)
- Interleukins
- nerve growth factor (NGF)
- insulin-like growth factor (eg IGF-1, IGF-2)
epidermal growth factor (EGF)
promotes epithelial cell growth
develops lungs, keratinisation of skin and mitogenic factor in breast milk
fibroblast growth factor (FGF)
angiogenesis (dev of new blood vessels), heparin binding, mitogenic
platelet derived growth factor (PDGF)
released during platelet activation, chemotactic, inflammatory and mitogenic
erythropoietin (Epo)
made in the kidneys, erythropoiesis in bone marrow
interleukins
approx 15 proteins acting in intercellular comms
nerve growth factor (NGF)
nerve growth and maintenance, critical for survival of sensory neurons, induces axon growth in nearby nociceptors
insulin-like growth factor
mediates the action of growth hormones, recreated from liver after stimulation by GH. insulin as an anabolic hormone, low levels lead to enhanced protein catabolism and amino acid uptake into muscle is inhibited.
growth hormone disorder
excessive: acromegaly - overgrowth of bony areas
lacking: dwarfism
where is ADH (vasopressin) synthesized
paraventricular and supraoptic neurons, axons project into posterior pituitary, median eminence, spinal cord and other areas of CNS.
where are ADH receptors found
kidney, pituitary, brain, blood vessels, platelets, liver, gonads, tumours
what is neurophysin II
a carrier protein that transport ADH to posterior pituitary
actions of ADH in reabsorption
kidney: affects ability of renal tubules to reabsorb water
receptors mainly in ascending loop of Henle and collecting ducts
no ADH: collecting ducts impermeable to water leading to diabetes insipidus
actions of ADH in blood pressure
BP: regulates blood volume
pressure sensors in carotid sinus, aortic arch and left atrium
afferent signals to brain stem via vagus and glossopharyngeal nerves
other actions of ADH, excluding BP and reabsorption
- causes ACTH release: significance unknown
- causes TSH release as much as TRH and can inhibit TRH release, may be part of negative feedback loop
- liver: glycogenelytic
- brain: memory and may social behavior
subtypes of ADH receptors
V1A: mediates glycogenolysis, platelet aggregation, cell proliferation, and release of coagulation factors
V1B: mainly in anterior pituitary, mediates release pop ACTH, beta-endorphin and prolactin
V2: only in kidney, defect results in nephrogenic diabetes insidious.
where is oxytocin synthesized
in the paraventricular and supraoptic nuclei.
functions of oxytocin
parturition and milk ejection, maternal behavior also shown in experiment
what is parturition
contraction of smooth muscle of uterine myometrium. (increasing ratio of estrogen to progesterone may stimulate oxytocin receptor synthesis)
what is milk ejection
suckling response, oxytocin binds to my-epithelial cells, causing contraction. sounds of baby crying may cause milk ejection
