2 - Hypothalamo-adenohypophysial System Flashcards
What is the anatomy of the anterior pituitary gland?
- derived from buccal cavity
- pars distalis is body
- pars tuberalis wraps around pituitary stalk
What are the labels of the anterior pituitary?
- hypothalamic nuclei
- hypothalamic neurones
- pars tuberalis
- region of median eminence
- adenohypophysis anterior pituitary (secretory cells)
- neurohypophysis posterior pituitary (nerve axons and terminals)
- pars distalis
What is the blood flow through the anterior pituitary?
- blood arrives in superior hypophyseal artery entering primary capillary plexus in median eminence
- blood drains from median eminence to second capillary plexus in anterior pituitary (portal network)
- blood flows out of capillaries to carvernous sinus and back to heart
What is the neuronal pathway associated with the anterior pituitary and what does it achieve?
- short hypothalamic neurones terminate at median eminence on surface of primary capillary plexus
- allows for neurosecretion to reach anterior pituitary
- neurosecretions exert effects when stimulated (stimulate hormones here)
What are the labels for the hypothalamic portal circulation?
- median eminence
- superior hypophyseal artery
- cavernous sinus (then out via jugular veins)
- primary capillary plexus (fenestrated)
- long portal veins
- secondary capillary plexus (fenestrated)
- anterior pituitary
What are the adenohypophysial hormones and which cells are they produced from?
- growth hormone (somatotrophin): somatotroph cells
- prolactin: lactotroph cells
- thyroid stimulating hormone (TSH, thyrtrophin): thyrotroph cells
- luteinising hormone (LH) and follicle stimulating hormone (FSH): gonadotroph cells
- adrenocorticotrophic hormone (ACTH, cortotrophin): corticotroph cells
Which hormones stimulate and inhibit somatotrophin?
- stimulate: growth hormone releasing hormone (GHRH)
- inhibit: somatostatin
Which hormones stimulate and inhibit prolactin?
- stimulate: thyrotrophin releasing hormone (TRH)
- inhibit: dopamine (DOMINANT SIGNAL)
Which hormone stimulates thyrotrophin?
thyrotrophin releasing hormone (TRH)
Which hormone stimulates LH and FSH?
gonadotrophin releasing hormone (GnRH)
Which hormones stimulates ACTH?
- corticotrophin releasing hormone (CRH)
- vasopressin
What is the mechanism of action of somatotrophin?
- targets body tissues and liver
- binding onto receptors on hepatocytes causes somatomedin production (IGF-1 and 2)
- somatomedins have indirect effect on metabolic actions and negative effect on GH
What are the metabolic actions of somatotrophin?
- stimulation of amin acid transport
- protein synthesis
- lipolysis (increased FA production)
- increased gluconeogenesis
- increased cartilaginous growth
- increased somatic cell growth
What stimulates the release of somatotrophin?
- sleep
- stress
- oestrogens
- exercise
- hypoglycaemia
- amino acids
- ghrelin
What is the mechanism of action of prolactin?
- targets breasts in lactating women
- tactile receptors on nipples associated with afferent neural pathway to hypothalamus
- efferent endocrine pathway from brain forms neuro-endocrine reflec arc
- acts as natural contraceptive (inhibits LH release, upregulates LH receptors in gonads and decreases sexual behaviour)
What are the labels of the brain?
- brain
- 3rd ventricle
- hypothalamus
- optic chiasm
- mamillary body
- anterior lobe
- posterior lobe
- pituitary gland
