MEH - Hypothalamic Pituitary Axis Flashcards
Why isn’t the post pituitary a true gland?
As it releases hormones that have been synthesised by the hypothalamus not synthesised itself
What hormones does the hypothalamus make (6+2)?
Oxytocin
ADH
TRH GHRH GHIH - somatostatin PIH - Dopamine GnRH - stimulates FSH/LH CRH
What is a tropic vs trophic hormone?
Tropic hormones have other endocrine glands as their target organ. Hypothalamus and anterior pituitary secrete tropic hormones.
Trophic hormones are growth hormones - ones that affect hyperplasia/hypertrophy
Where are oxytocin and ADH made and how do they travel to the posterior pituitary?
Both made in supraoptic and paraventricular nuclei of hypothalamus and travel to posterior pituitary by nerve cell axons. Post pituitary then releases them into the blood to act directly on target tissues
Are the anterior and pituitary similar or separate entities? Where are they derived from embryologically? Which is directly connected to the hypothalamus?
Embryologically distinct
Ant pituitary - from primate gut tissue
Post pituitary - from primitive brain tissue
Post pituitary is physically connected to the hypothalamus
What 6 hormones does the Ant pituitary secrete?
TSH Growth Hormone FSH LH ACTH Prolactin (inhibited by PIH stimulated by TRH)
Explain how the anterior pituitary is autocrine, paracrine endocrine and neurocrine
Auto and paracrine - ant pituitary hormones affect self and neighbouring cells
Neurocrine - from hypothalamus
Endocrine - via blood to target tissues
What is the stalk of the pituitary called? What pathology can occur here?
Infundibulum
Tumours
What is the hypothalamus known as the link between?
Neural and endocrine
How do hormones travel from the hypothalamus to the anterior pituitary?
Via nerves in the hypothalamus to the median eminence (blood vessels at base of brain) then via hypopophyseal portal system (blood vessels) to the anterior pituitary
What is the median eminence used for?
Storage of hormones before travelling to ant pituitary
What is the role of negative feedback in the body?
To maintain homeostasis - to keep levels of chemicals in the body within physiological ranges
What are 8 functions of hormones that have come from the hypothalamus and pituitary gland?
Body growth Sex hormones - Reproduction Stress response Milk production Lactation Puberty Adrenal gland function Thyroid gland function Water homeostasis (ADH)
What does GHRH stimulate and where (2)?
Goes to liver (and skeletal muscle) which is stimulated to produce IGFs. IGFs stimulate growth (main action is via IGFs)
GHRH also stimulated growth directly in many tissues
Where do LH and FSH target?
Ovaries and testes - sex hormone production