Endrocrinology physiology Flashcards
Pituitary gland position
Hanging off hypothalamus connected to the infundibulum
Nuclei found in the posterior pituitary gland
Supraoptic nucleus
Paraventricular nucleus
What does the supraoptic nucleus secrete?
ADH/ Vasopressin
What stimulates the supraoptic nucleus in the hypothalamus
low blood volume
low blood pressure
high plasma osmolality
pain
What effect does alcohol have on the supraoptic nucleus
Inhibitory
What does the paraventricular nucleus secrete in the posterior pituitary gland
Oxytocin
What stimulates the paraventricular nucleus in the posterior hypothalmus
Birthing process
Suckling
Ejaculation
What is the hypophyseal portal system
2 capillary beds (primary & secondary capillary plexuses)
Connected in series through an intermediate portal vein
this is the anterior pituitary connection
The paraventricular nucleus secretes what in the anterior compartment of the pituitary gland
CRH: Corticotropin-releasing hormone
TRH: Thyrotropin-releasing hormone
Action of CRH
Stimulates genes in corticotrope.
Proopiomelanocortin gets broken down into Alpha Milano stimulating hormone (alpha MSH) and adrenocorticotropic hormone (ACTH)
Action of TRH
Stimulates thyrotrope to release TSH
What does the arcuate nucleus secrete
Growth Hormone releasing hormone
PIH or dopamine
The action of Growth Hormone releasing hormone
Causes stimulation of somatotrope to secrete growth hormone
The action of PIH or dopamine
Stimulates lactotrope to secrete Prolactin
Ganado tropen releasing hormone action
Stimulates Gonadotrope to secrete FSH LH
Depending on the frequency of GnRH: High frequency is LH, lower frequency is FSH
Somatostatin inhibits this
Nucleus present in anterior pituitary gland
Paraventricular nucleus
Arcuate nucleus
Preoptic nucleus
What does oxytocin bind to in the uterus?
smooth muscle of the myometrium
causing it to contract and therefore help during birthing process
Oxytocins involvement in lactation
Binds to the mammillary bodies of breasts send signals to the hypothalamus
Results in milk ejection during lactation
Stimulated by suckling
Oxytocin has a ____ half life
short
so regulated frequnetly
What receptor does ADH bind to the principal cell of the collecting tube
What receptor does ADH bind to in blood vessels
Vasopressin type 2 receptor
Vasopressin type 1 receptor
Steps of ADH activation
Stimulus sends receptors to the hypothalamus
The supraoptic nucleus causes ADH to be secreted
Binds to V2 receptors
Stimulates Gs protein which binds to GTP and gets activated
This then binds to adenyl cyclase and converts ATP into cAMP activating pKa
pKa then goes and inserts into vesicles containing aquaporin 2 into the apical membrane
increases H20 Permeability of collecting duct
Effects of stimulation of ADH
Stimulated by low blood pressure or high plasma osmolality
In blood vessels: Increase vasoconstriction and therefore peripheral resistance and therefore increase blood pressure
In kidneys: Causes the increase of plasma volume and therefore BP
Hormones of the anterior pituitary gland
FLAT PIG
FSH
LH
ACTH
TSH
Prolactin
GH
What nucleus secrete growth hormone
Arcuate nucleus
What inhibits/ stimulates prolactin
inhibits PIH or dopamine (arcuate nucleus)
stimulates: thyrotropin-releasing hormone (paraventricular nucleus)
Stimulates: oestrogen + breastfeeding
How does iodide enter from the blood into follicles of the thyroid gland
secondary active transport
What does thyroid peroxidase do?
Iodide oxidation: turns iodide ions into iodine
Iodination: puts I2 onto amino acids on tyrosine amino acids
Fuses DIT + DIT = T4 (Throxine)
Fuses MIT + DIT = triodothyronin
What is it called when a tyrosine amino acid has:
one iodide group
two iodide group
Monoiodotyrosine
Diiodotyrosine
What makes up the thyroid hormone?
T4 thyroxine +
T3 triiodothyronine
How is T3 + T4 made from tyrosine molecule
Tyrosine is broken down into T3 + T4 components via lysozyme enzymes
Thyroid synthesis steps
- TRH release from paraventricular nucleus from hypothalamus
- Anterior pituitary to release from TSH
- TSH stimulates follicle cells of the thyroid to synthesise thyroglobulin
- Iodide trapping
- Oxidation of iodide via thyroid peroxidase
- Iodination of tyrosine amino acids
- Couple of the DIT + MIT
- Endocytosis of thyroglobulin with T3 + T4
- Lysosomal enzymes cleave T3 + T4 out of thyroglobulin
- Exocytosis of T3 + T4 into blood plasma
How does T3 act
Inducing gene transcription and protein synthesis
What does the Thyroid hormone do?
Promotes normal bone growth + maturation
Promotes muscular function and development
Increase basal metabolic rate/ O2 usage
Promotes normal C.O
Promotes an increase in synapses/myelinations/dendrites
Promotes G.I motility + secretions
Promotes normal hydration of skin
What cell is stimulated by low calcium levels
Chief cells
What does it mean when there is low blood calcium
Stimulates the parathyroid to secrete parathyroid hormone
How does the Parathyroid hormone affect kidneys
Increases calcium reabsorption decreasing Ca2+ excretion
Excreting phosphates as well
The indirect effect of the parathyroid hormone
- When exposed to sunlight 7 dehydrocholesterol gets drawn into the blood and broken down into Cholecalciferol
- Goes into the liver to become 25-OH Cholecalciferol
- Parathyroid hormone stimulates an enzyme in the kidney which together with 25OH cholecalciferol becomes 1,25 diOH Cholecalciferol (calcitriol)
- Calcitriol is the active form of vitamin D
What makes up the adrenal cortex
Zona glomerulosa
Zona Fasiculata
Zona Reticularis
What stimulates the adrenal cortex
Angiotensin 2 (1st)
low Na+ or high K+ (2nd)
ACTH (3rd)
Both undergo GS protein mechanism e.t.c to produce pKa which phosphorylates cholesterol conversion of ….
What is aldosterone derived from and what type of hormone is it?
Cholesterol
Steroid hormone
What inhibits Zona glomerulosa
Atrial natriuretic peptide
What hormones are corticosteroids
steroid hormones produced in the adrenal cortex
Cholesterol is the Precursor
What does aldosterone do?
Increase Na+ absorption
Decrease K+
Increase H2O absorption
Where is aldosterone produced
Zona glomerulosa
Where is cortisol secreted
Zona fasciculata
What stimulates Cortisol secretion
ACTH
undergoes same action as with aldosterone
What is cortisol derived from?
cholesterol
Steroid hormones transported around blood
Steroid hormones need carrier proteins to travel within the blood
What does zona glomerulosa secrete
Mineral corticoids (Aldosterone)
What does zona fasiculata secrete
Glucocorticoids (Cortisol)