The hypothalamic-pituitary axis Flashcards
What is the basic structure and anatomy of the hypothalamic-pituitary axis
Anterior and posterior pituitary glands.
Has a hypophyseal portal system
Paraventricular nucleus
Supraoptic nucleus
Describe how anterior pituitary differs from posterior pituitary
Anterior- primary plexus and secondary plexus blood supply, hypophyseal portal system
posterior- Capillaries- blood supply, Paraventricular nucleus, Supraoptic nucleus
What is Neurohypophysis and adenohypophysis
Neurohypophysis= down-growth of the forebrain
Adenohypophysis = oral ectoderm of the roof og the stomatodeum
What are the 5 cell types in the anterior pituitary?
Somatotropes
Corticotropes
Thyrotropes
Gonadotropes
Lactotropes
What is neural tissue responsible for
Transport and storage of secretory granules of hormones manufactured in the hypothalamus
What are the supraoptic and para ventricular nuclei responsible for releasing?
Supraoptic- ADH
Paraventricular- Oxytocin
What does ADH regulate
Blood pressure
By reducing urine output and triggering vasoconstriction
What stimulates ADH secretion?
Increased plasma osmolarity, Decrease in blood volume, stress, pain
Describe the physiological effects of ADH
Increases the permeability of the final 1/3 of the distal convoluted tubules and the entirety of the collecting duct to water.
This leads to increased movement of water from tubular fluid into the interstitial fluid in the kidney, leading to an increase in plasma volume and blood pressure.
It also induces vasoconstriction on arterioles.
Can cause bradycardia and a reduction in cardiac output.
What can abnormally high and low levels of ADH lead to
High= high urine osmolarity, oedema, low plasma osmolarity
Low= Diabetes insipidus
What is oxytocin responsible for?
Stimulates secretion of breast milk from lactating females
May also contribute to parturition of a foetus
How is oxytocin secretion stimulated
Suckling, vaginal/cervical stimulation during labour
Crying
What are the physiological effects of oxytocin?
Oxytocin initiates myopeithelial cell contraction and milk letdown.
Prolactin increases milk production
what are the symptoms of a pituitary tumour
headache, visual field defects, hypopituarism
