Lecture 19: Hypothalamic-Pituitary Function Flashcards
what is the most common means of intercellular communication
chemical signalling
what cells do paracrine chemical messengers affect
neighbouring cells only
what cells do autocrine chemical messengers affect
secreting cells only
how are chemical messengers distributed
diffusion
what do neurotransmitters affect
nerves, muscles or glands
give examples of paracrine messengers
- histamine
- NO
- some growth hormones
give examples of neurotransmitters
- ACh
- amines e.g. noradrenaline
- amino acids e.g. glutamate
- neuropeptides
- NO
where are hormones secreted into and by what
into the blood by endocrine cells
where are neurohormones secreted and by what
into the blood by neurosecretory neurons
give examples of hormones
- thyroid hormone
- adrenaline
give examples of neurohormones
- ADH
name the 4 hormone classes and give examples of each
- amine
- -> norepinephrine
- -> dopamine
- -> thyroid hormone
- peptide
- -> oxytocin
- -> ADH
- -> neurohormones
- -> glucagon
- protein
- -> human growth hormone
- -> insulin
- -> calcitonin
- -> parathyroid hormone
- steroid
- -> testosterone
- -> progesterone
- -> oestrogen
- -> mineralocorticoids
- -> glucocorticoids
- -> activated Vit D
name some stimuli for hormone release
- direct neural innervation
- releasing hormones
- plasma levels
how can hormones be transported in blood
free or bound to plasma protein
which hormones are transported free
most amine, protein and peptide hormones
which hormones are transported bound
steroid (as they’re hydrophobic) and thyroid hormones
what types of plasma proteins bind to hormones for transport
majority globulins and albumin
describe the genomic/non-genomic effects a hormone can have
genomic –> alter protein synthesis so alter cell behaviour
non-genomic –> alter protein function
where can hormone receptors be found (cell)
- on cell surface membrane
- in cytoplasm
- nucleus
function of hypothalamic-pituitary axis
stimulates secretion of a number of hormones e.g. thyroid
what connects the hypothalamus to the pituitary
infundibulum - has nerves and small bv
what cavity does the pituitary gland sit in
hypophyseal fossa
what can a bi-temporal hemianopia be a symptom of and what is it
- symptom of pituitary tumour (can impinge on optic chiasma)
- loss of peripheral vision
what is the optic chiasma
where optic nerves of both eyes cross over
name the lobes of the pituitary gland and describe the tissue each lobe is made of
- posterior (neurohypophysis) –> brain tissue
- anterior (adenohypophysis)
- -> glandular tissue
describe how each lope of pituitary is connected to the hypothalamus
- posterior –> neural pathway (axons)
- anterior –> vascular pathway
what system do posterior pit. and hypothalamus form and what hormones does that system secrete
- neuroendocrine system
- secretes ADH and oxytocin
where do the cell bodies of the axons linking the hypothalamus to post. pit. lie
- in two discrete nuclei
1. paraventricular nucleus
2. supraoptic nucleus
where are ADH and oxytocin manufactured
in the cell bodies of the neurones connecting hypothalamus with post. pit. (then stored in axon terminals)
which nuclei contains most the neurones that secrete oxytocin
paraventricular nucleus
which nuclei contains most of the neurones that secrete ADH
supraoptic nucleus
what is the function of oxytocin
stimulates uterine contraction (stimulates birth) and milk ejection
- also known as love hormone
what is the function of ADH (vasopressin)
- vasoconstrictor –> increases vascular resistance and BP
- increases H2O permeability and absorption in renal collecting ducts
what type of hormones are secreted by anterior pituitary, give the 7 examples
primarily tropic hormones
- growth hormone
- thyroid stimulating hormone
- adrenocorticotrophic hormone (ACTH)
- Prolactin (not tropic)
- follicle stimulating hormone
- luteinising hormone
- melanocyte stimulating hormone (not tropic)
what is a tropic hormone
- hormones that influence/ regulate the secretion of hormones from another endocrine gland
- stimulate and maintain endocrine target tissue
what is the function of ACTH
stimulates adrenal gland to secrete corticosteroids
which brain region regulates hormone secretion from pituitary gland
hypothalamus
which hormones are secreted by neurohypophysis
ADH and oxytocin
what are the two most important factors that regulate ant. pit. hormone secretion
- hypothalamic hormones (hypophysiotropic)
- feedback by target gland hormones
what connects the hypothalamus and ant. pit.
hypothalamic-hypophyseal portal system
what is the importance of a portal system between hypothalamus and ant. pit.
- venous blood so doesn’t enter systemic circulation
- concentrated hormones can move from hypothalamus to ant. pit. w/o being diluted
- rapid response to release of hypothalamic hormones –> direct travel
decreased secretion of which hormone results FROM damage to hypothalamic-hypophyseal portal system…
- ADH
- Prolactin
- Oxytocin
- PTH
- TSH
answer = TSH
- ant. pit. affected therefore rule out 1, 3 and 4
- prolactin has two hypothalamic hormones governing its secretion –> releasing and inhibiting –> damage means there’s less inhibition so prolactin secretion can increase moderately
what are the 3 hormones/ levels for hypothalamic pituitary target gland secretion regulation
- hypothalamus / neurohormone
- pituitary gland / tropic hormone
- peripheral gland / peripheral target-endocrine gland hormone
describe long loop negative feedback
inhibits both pituitary gland secretion and hypothalamus secretion
describe short loop negative feedback
hormone secreted by pituitary inhibits hypothalamus secretion
what is important to consider when measuring hormone levels
diurnal and circadian rhythms
describe primary hyposecretion
too little hormone is secreted due to abnormality within secreting gland itself
name some cause of primary hyposecretion
- genetic
- dietary (e.g. lack of iodine)
- chemical or toxic
- autoimmune
- cancer
- iatrogenic
describe secondary hyposecretion
gland is normal but too little hormone is secreted due to deficiency of tropic hormone –> assc w/ deficiency in ant. pit.
describe tertiary hyposecretion
gland is normal but too little hormone is secreted due to deficiency of hypothalamic releasing hormone
what is pan hypopituitarism
production and secretion of all pituitary hormones are reduced both ant. and post.
name a cause of hypersecretion
tumours –> ignore normal regulatory input and continuously secrete excess hormone
describe primary hypersecretion
abnormality within gland
describe secondary/ tertiary hypersecretion
excessive stimulation from outside the gland (2nd = pituitary, 3rd = hypothalamus)
outline some consequences of hypersecretion (in terms of ant. pit. hormones)
- ^ ACTH –> corticosteroid excess –> Cushing’s
- ^ prolactin –> impaired reproductive function
- ^ ADH –> fluid retention and low plasma osmolality
- ^ TSH –> Grave’s disease
- ^ hGH (children) –> gigantism
- ^ hGH (adults) –> acromegaly
