Hypothalamic Flashcards
(44 cards)
What is the endocrine system
A collection of glands that produce hormones that regulate metabolism, growth and development
What does the hypothalamus and pituitary (HP axis) do?
Regulates the function of the thyroid, adrenal and reproductive glands
Controls somatic growth, lactation, milk secretion and water metabolism
The anatomy of the pituitary?
Lies in a pocket of bone at the base of the brain (just below the hypothalamus)
Contains two lobes: posterior and anterior
The anterior pituitary characteristics?
It has a unique blood supply
Release factors into the anterior
2 neurosecetory cells that secrete releasing hormones.
The posterior characteristics?
Portal system
Direct hormonal secretion into posterior.
3 neurosecetory cell bodies.
What does the posterior do?
Role in body fluid homeostasis and reporudctive function.
Magnocellular neurons in paraventricular and supraoptic neurones secrete oxytocin and vasopressin into the posterior lobe.
Vasopressin for water reabsorption
Oxytocin: lactation and labour
ADH (vasopression) and oxtoycin is synthesised where?
In the cell bodies of the hypothalamic neurones
ADH: by the supoaptic nucleus
Oxytocin: by paraventricular nucleus
Synthesis process of ADH and oxytocin
Both are synthesised as pre-prohormones
Processed into 9 amino acid peptides.
Released from axonal termini in response to AP.
Axonal swelling due to storage of secretory granules are termed Herring bodies.
Difference between ADH and oxytocin in structure?
Both are nonapeptides (9AA)
Differ in 2 amino acids.
Cys- Tyr- Phe/Gln-Gln-Asn-Cys-Pro-Arg/Leu-Gly-NH2
Use of ADH
Water reabsorption in the kidney.
Contraction of smooth muscle
Maintance normal osmolarity of body fluids.
Use of oxytocin
Contraction of uterine smooth muscle
Childbirth
Primary target of ADH
Cells lining the distal renal tubule.
Principle cells of the collecting ducts of the kidneys.
How does ADH bring about its action?
Binds to vasopressin 2 receptors on basal side of renal cells.
Vasopressin-2 receptors is a GPCR linked to the Gs-cAMP-PKA pathway.
V2R signalling boosts insertion of aquaporin2 into apical membrane (causing water to be taken in).
Causing more water to be reabsorbed.
In the presence of ADH what happens into urine flow and osmolarity (conc)?
Urine flow decreases
Urine osmolarity increases
In the absence of ADH what happens to urine flow and osmolarity?
Urine flow increases
Urine osmolarity decreases
ADH is released in response to?
Increase in extracellular fluid osmolarity
Decrease blood volume and pressure
Increased osmolarity stimulates the magnocellular cells to release ADH
Cardiovascular volume receptors stimulate these cells when there is a drop in blood volume.
Oxytocin mechanism?
Stimualtes contraction
Stretching of the cervix stimulates oxytocin release.
Postive feedback causing a stimulation of stretching causing more oxytocin release.
At birth, stretching is weakened and no postive feedback
Anterior pituitary?
Connected to hypothalamus by hypophyseal-portal circulation.
Made up of hormone producing glandular cells.
Produces 6 peptide hormones
Name the 6 peptide hormones the anterior pituitary produces?
Prolactin
Growth hormone
Thyroid stimulating hormone
Adenocarticotorphic hormone
Follicle-stimulating hormone
Lutenising hormone
The connection between hypothalamus and anterior pituitary?
Parvicellular neurosectory cells secrete releasing factors into capillaries of the pituitary portal system.
Factors are transported to the anterior pituitary to regulate secretion of pituitary hormones.
Anterior pituitary control?
From hypothalamus to pituitary is controled by hypothalamic releasing hormone.
From pituitary to end organ is controlled by putuitary hormone.
The end hormone is controlled by the end organ hormone.
Name the 7 hypothalamic releasing hormones and what do each of them do?
**CRH: **stimualtes ACTH secretion.
**TRH: **stimulates TSH secretion.
**GHRH: **stimulates GH secretion.
**Somatostatin: **inhibits GH secretion.
**GnRH: **stimulates LH and FSH secretion.
**PRH: **Stimulates PRL secretion.
**PIH: **inhibits PRL secretion.
Name the 6 hormones produced by the anterior pituitary?
**Thyrotrophin: **thyroid gland regulation.
ACTH: adrenal cortex regulation.
FSH: Ovulation in females and spermatogensis in males.
LH: Regulates testersterone in males and ovulation in females.
Growth hormone: Regulation of metabolic processes for growth.
Prolactin: mammary development & lactation.
Feedback regulation of the H-P axis?
Ability of hypothalamic releasing hormones to provide negative feedback.
