Revision lecture Hypothalamic pit axis Flashcards
What is the function of the posterior pit?
storage of hormones synthesised in the hypothalamus and transported to the posterior pit via the inferior hypophyseal artery.
Ready for later release
Give two examples of hormones released from the posterior pit?
Also a bit on what each hormone does
Oxytocin- Aids lactation, sexual excitement, uterine contractions etc..
ADH: Increased reabsorption of water from the collecting ducts of the kidneys
Also vasoconstriction
What is the stimulus for ADH release
High blood osmolality
Why does alcohol lead to increase urine output
Inhibits ADH release, so less water reabsorption
Name 4 hormones synthesised and released from the anterior pit?
TSH- Stimulates thyroid hormone release
Prolactin- Increased breat milk production
ACTH- Cortisol release from the adrenals
GH- Stimulates inssulin release ad growth factor release from the liver. Also growth effects
From where is growth hormone secreted? and what stimulates growth hormone release? What inhibits growth hormone production
Anterior pituitary
GHRP from the hyppothalamus stimulates
Somatostatin inhibits its production
What causes the release of growth hormone?
Deep sleep
Stress (trauma, surgery)
Exercise
fall in glucose or FAs
4 actions of growth hormone?
Hypertrophy and hyperplasia
increased protein synthesis
increased lipolysis
decreased glucose uptake
Describe the negative feedback of GH secretion
Long loop-
IGFs, secreted in the liver have three effects, two on hypothalamus one on anterior pit gland
inhibit release of GHRH+stimulate release of somatotropin
inhibit release of GH from ant pit
Short loop- GH from the ant pit causes stimulation of somatostatin release from the hypothalamus
What is the result if in childhood you are GH deficient?
pituitary dwarfism
delayed sexual development
What is the result of growth hormone excess? in childhood and adulthood
Gigantism in childhood
acromegaly in adults
How do GHs exert their effects on cells?
GH receptors activate Janus kinases–>activation of signalling pathways–>transcription factor activation and IGF production
What four things does Insulin like growth factor cause?
Hypertrophy
Hyperplasia
Increased rate in protein synthesis
Increased rate of lipolysis in adipose tissue
What is the name of the bony socket that the pit glands sit in?
Sella turcica
how is the hypothalamus connected to the pit glands
the infundibulum
where in the hypothalamus are oxytocin and ADH produced?
supraoptic nuclei
paraventricular nuclei
Describe how the hormones that are synthesised in the hypothalamus and stimulate the anterior pit gland travel from the hypothalmus to the ant pit gland
hormones synthesised in the hypothalamus–>transported down axons–>stored in median eminence–>released into the hypophyseal portal system–>stimulation of endocrine cells in the ant pit gland
Define tropic hormone
A hormone that affects the release of another hormone from a target tissue
name 5 tropic hormones that are released from the hypothalamus and stimulate the ant pit gland and what each stands for
TRH- thyrotropin releasing hormone GnRH- Gonadotropin releasing hormone CRH-Corticotropin releasing hormone GHRH- GH releasing hormone GHIH- Growth hormone inhibiting hormone (Somatostatin)
Define trophic hromone
hormone that affects growth
name 6 hormones released by the ant pit
TSH- Thyroid stimulating hormone ACTH-Adrenocorticotropic hormone LH FSH PRL-Prolactin GH
How does growth hormone mainly have its effects via?
Insulin like growth factors
where are insulin like growth factors produced and secreted?
liver and skeletal muscle
in children, what effects do IGF and GH have?
GH- Long bone growth
IGF- Bone and cartilage growth
In adults what do IGF and GH do?
help maintain muscle and bone mass and heal and repair and also modulate metabolism and body composition
