ES 2 - Hypothalamus, Pituitary Gland and GH

pituitary gland anatomy, hypohtalamic-hydrophyseal portal system, hypothalamic hormones and growth hormone

where is anterior pituitary located (relative to hypothalamus, what bone)

underneath hypothalamus in the sella turcica (depression in the sphenoid bone)

anterior pituitary 2nd name

adenohypothesis

hormones of ant. pit. gland

TSH (thyroid), ACTH (adrenocorticotrophin), FSH (follicle stimulating), LH (luteinising) GH (growth hormone), PRL (prolactin), MSH (melanocyte)

posterior pituitary 2nd name

neurohypothesis

ant. pit structure

derived from epithelial tissue/oral cavity, composed of pars distalis and pars tuberalis (wraps around infindibulum)

post. pit structure

derived from neural tissue/neuroectoderm, composed of pars nervosa and infindibulum

posterior pituitary gland hormones

ADH (antidiuretic) and oxytocin (OXT)

pars intermedius summary

sometimes MSH, mostly remnant from fetal development

different neuron groups in hypothalamus (and functions)

neurosecretory - control secretion of ant. pit. via RH and RIH in bloodstream
PVN and SON - synthesise and control secretion of post. pit hormones via. APs
preganglionic sympathetic - directly controls secretion of adrenal medulla hormones via nerves

hypothalamic-hypophyseal portal system

hypothalamus hormone released into mediance eminence into primary capillary network
portal veins to secondary network
ant pit cells release hormones into blood supplied by superior hypophyseal artery
leave through hydrophyseal veins

hypothalamus and post. pit connection

SON and PVN produce ADH and OXT that are packaged into secretory vesicles, moved down axon and stored in terminals
APs sent down neurons cause release of hormones into capillary network around post. pit.
blood enters through inferior hypophyseal artery and leaves with hormones through hypophyseal vein

oxytocin summary

peptide hormone synthesised mostly in PVN triggered for release by stretching of cervix and infant suckling during breastfeeding

antidiuretic hormone summary

peptide hormone synthesised mostly in SON

milk letdown reflex

OXT released acts on myoepithelial cells that surround milk glands and contract to force milk along ducts into lactiferous sinus (milk resevoirs)

ADH triggers for release

increase in ECF osmolarity releases ADH causing reabsorbtion of more water by collecting ducts in kidneys and dilution of ECF
decrease causes inhibition of ADH secretion causing less absorption, concentrating ECF

types of diabetes indipidus and causes

neurogenic (damage to hypothalamus, insufficient ADH secretion)
nephrogenic (genetics, medication or diseases, no response to ADH from kidneys)
both result in dehydration

hypothalamic releasing and inhibiting hormones

TRH (thyrotropin), CRH (corticotropin), GHRH and GHIH/somatostatin (growth), GnRH (gonadotropin), PRH and PIH (prolactin)

negative feedback loops of hypothalamus and ant. pit.

signals sent to hypothalamus (long) or ant. pit (short) when enough hormone has been released

how are the effects of hGH (human growth hormone) produced?

indirectly through somatomedins/insulin-like growth factors made in the liver

hGH growth effects

increased size and number of muscle, bone and cartilage cells
maintenance of muscle and bone mass
promotes repair

hGH metabolic effects

increased growth and protein synthesis
switches cell metabolism to lipids (raises blood glucose and saves glucose for brain)
weakens effects of insulin

GH secretion regulation

GHRH (released if low blood glucose) and GHIH (released if high blood glucose)

GH disorders

insufficient GH during childhood may result in dwarfism
excessive GH before (gigantism) or after (acromegaly) epiphyseal plates close

ant. pit secretory cells

somatotrophs (GH), thyrotrophs (TSH), gonadotrophs (FSH and LH), corticotropes (ACTH), lactotropes (PRL)

SIADH (syndrome of inappropriate ADH secretion)

MDMA (and other substances) can cause excessive ADH secretion and interfere with thermoreceptors resulting in overconsumption and retention of water

how does SIADH cuase brain swelling

water moves via osmosis from diluted ECF to brain cells causing swelling