signal transdruction and hypothalamus/pituitary Flashcards
3 types of cellular signalling pathways
physical/chemical signals, signal transduction, signal amplification/response
what is extracellular domain
binding site for hormones/other molecules
what is transmembrane domain
anchors receptor in cell membrane
what is ion channel linked receptors
membrane is impermeable to ions, channels open and ions flood in, rapid response, specific for sodium, potassium, calcium, chlorine ions
what is intracellular domain
effectors domains, transduce the signal
what do GPCRs do
G protein coupled receptors, can regulate ion channels, channels opened or closed by g protein, slow acting
how do enzyme linked receptors works
mostly tyrosine kinase, hormone binds to enzyme linked receptors, conformational changes induced, enzyme activity activated
signal amplification steps
1 messenger binds to 1 receptor, multiple G proteins activated, each G protein activates an adenylate cyclase, and each adenylate cyclase generates hundreds of cAMP molecules which activates a protein kinase A, each protein kinase A phosphorylates hundreds of proteins
messenger–>receptor–>G proteins–>adenylate cyclase–>cAMP–>protein kinase A–>phosphorylates hundreds of proteins
5 major second messenger molecules
cAMP, cGMP, DAG, IP3, calcium
other types of signalling molecules
neurotransmitters, cytokines, neurohormones, eicosanoids
what is endocrine axis
independent glands working together to control body functions
master regulators (hypothalamic pituitary axis)
thyroid, adrenal cortex, gonads
features of hypothalamic pituitary axis
pineal gland, hypothalamus, pituitary gland, spinal chord
what is autocrine signalling
bind receptors on the same cell
what is paracrine signalling
targets neighbouring cell
what is endocrine signalling
targets distant cells via bloodstream
what is neuroendocrine signalling
neurons target distant cells via bloodstream
what is the hypothalamus
small brain region, grey matter, contains multiple neural centres and neural fibres, connects to other brain regions
what does the hypothalamus control
hunger, thirst, body temp, blood pressure, childbirth, emotion, sex drive, social bonding, circadian rhythms
what is the pituitary
neural and vascular connections
describe the structure of hypothalamus and pituitary
hypothalamus, pituitary stalk, anterior pituitary, posterior pituitary (balls lmao)
two hormones secreted by the posterior pituitary and the role of them
antidiuretic hormones (ADH)- regulates water reabsorption in kidney
oxytocin- regulates birth and lactation
where is antidiuretic hormones produced
neurons in paraventricular nucleus
where is oxytocin produced
neurons in supraoptic nucleus
describe how the posterior pituitary works
neuronal centres in hypothalamus receive neural signals, neuroendocrine cells release peptide hormones by exocytosis at axon terminals, neurohormones permeate into capillary beds, no blood brain barrier
what connects the hypothalamus and anterior pituitary
hypothalamic-pituitary portal system
what does the hypothalamic pituitary portal system consist of
two capillary beds in series
how does the anterior pituitary work
neuronal centres in hypothalamus release peptide hormones by exocytosis at axon terminals, hormones enter first capillary bed and carried through portal vein to anterior pituitary, pituitary endocrine cells stimulated to release other tropic hormones which act on tissues/endocrine glands
list some tropic hormones produced by the hypothalamus
PRH- prolactin releasing hormone
PIH- prolactin inhibiting hormone
TRH- thyrotropin
CRH- corticotropin
GHRH- growth hormone
GHIH- growth hormone
GNRH- gonadotropin
name some tropic hormones released by the anterior pituitary
prolactin
TSH- thyroid stimulating hormone
ACTH- adrenocorticotropin
GH- growth hormone
FSH- follicle
LH- luteinising hormone
what are pituitary tumours
hyper/hyposecretion of hormones, common, benign, slow growing
symptoms of pituitary tumours
visual disturbances, headaches, endocrine disturbances
types of feedback loosp
short and long loop negative/positive feedback
what is the thyroid gland
butterfly shaped gland on trachea, produces thyroid hormones and calcitonin
what does calcitonin do
lowers serum calcium ions and promotes calcium ion deposition in bones
what do thyroid hormones T3 and T4 do
regulate metabolism and basal metabolic rate
what are parathyroid glands
4 small glands on the back of the thyroid gland, secretes parathyroid hormone
what do parathyroid hormones do
regulate calcium ion and phosphate levels in blood, promote release of calcium ions from bones, promote ca2+ reabsorption in kidney
antagonistic action to calcitonin and vitamin D to balance ca2+ and maintain phosphate levels
molecular structure of T4
2 molecules of L-tyrosine and 4 iodide ions
where are thyroid hormones produced
follicles of thyroid gland
difference between T3 and T4 hormones
T3 is 5 fold more active, T4 is more abundant
both lipophilic hormones
where are T3 and T4 generated
thyroglobulin
what do thyroid hormones do
increase metabolic activity in most tissues, stimulate fatty acid metabolism/gluconeogenesis/glycogenolysis
what are thyroid hormones needed for
growth and development, development of neonatal brain, visual system/retinal function
what is a colloid
viscous protein rich fluid which acts as a store of thyroid hormone precursors in glycoprotein form and iodide ions
how is T3 and T4 synthesised in follicle cells
thyroid hormone precursors stored as a form of glycoprotein and iodide ions in colloid, enzyme generates iodinated tyrosine and combine the iodotyrosines and they get converted into T3/T4 in follicular cells
describe the structure of thyroid gland follicles
(on one note) inside area is colloid, surrounding is follicular cells
what produces calcitonin
parafollicular cells
how many iodide ions in T3
3
how is the storage of T3 and T4 increased
follicular cells take up iodide ions via Na+ channel receptor, iodide ions transported to colloid, Tg released into colloid by exocytosis, TPO stimulates Tg iodination and conjugation of MIT and DIT, store of T3 and T4 increased
how is the release of T3 and T4 stimulated
serum levels of T3/4 decrease, hypothalamic pituitary axis produce TSH, TSH leave capillary and binds to receptors on follicular cell to activate channel receptor and signal cascade, endocytosis of Tg-T3-T4 which gets broken down into lysosomes, T3 and T4 released into capillary
what regulates the synthesis and release of thyroid hormones from thyroid follicles
serum TSH and T3/4 levels
