endocrine lectures Flashcards
neural communication?
neurotransmitters released act on post-synaptic cell
paracrine communication?
cell products diffuse in extracellular fluid to affect the same or neighbouring cells
endocrine communication?
hormones reach their target cells through blood circulation
ligand, source and target?
ligand = chemical messenger source = cells that produce the ligand target = cell with receptors to respond to ligand
lipophobic ligand?
not lipid soluble, but is water soluble. doesn’t easily cross the cell membrane, may need pumps or channels.
receptors on cell membrane. response often enzyme activation or membrane permeability changes
lipophilic ligand?
lipid soluble, not water soluble.
easily cross the cell membrane.
receptor usually located within the cell.
target response usually gene expression.
amines as chemical messengers?
most are lipophobic.
made or derived from amino acid.
example amine messengers?
catecholamines are derived from tyrosine - dopamine, epinephrine.
serotonin made from tryptophan
peptide/ protein messengers?
- most abundant type
- lipophobic
- made of chains of amino acids. (>50 is protein ligand,
steroid ligands?
- lipophilic
- derived from cholesterol
- all steroid ligands function as hormones.
lipophilic ligand synthesis and release?
synthesized on demand, released immediately.
lipophobic ligand synthesis and release?
synthesis is independent of demand. stored in vesicles until needed. released by exocytosis.
amine synthesis?
-produced in cytosol of source
amine product is dependent on enzymes present
transport of ligands?
- interstitial fluid if source and target are close. ligand then quickly degraded
- blood borne transport if source and target are a distance apart. lipophobic dissolve in plasma, lipophilic bind to carrier protein
half life of dissolved and protein bound messeengers?
dissolved relatively short
bound is relatively long
strength of ligand response depends on?
- concentration of ligands
- number of receptors on target cell
- receptor ligand affinity
down-regulation?
- receptor number on target decreases
- may result from excess messenger
- sensitivity to messenger decreases
- tolerance to messenger develops
up-regulation?
- receptor number on target increases
- may result from too little messenger
- sensitivity to messenger increases
agonist and antagonist?
agonist - chemical that binds to a receptor and mimics the normal response
antagonist - chemical which binds to a receptor but binding has no effect - it competes with the ligand.
enzyme linked membrane receptor?
receptor and enzyme are same protein - ligand binding activates the enzyme and target response occurs.
G protein linked receptor/ channel?
binding of ligand activates G protein which activates channel. this process is slow. change in transport of ions through the channel causes a target response.
second messenger systems?
binding of first messenger to a receptor leads to production of second messenger.
Gs activates amplifier enzyme
Gi inhibits amplifier enzyme
cholera and G proteins?
cholera toxin binds ganglioside in small intestine. G protein activates cAMP. protein kinases lead to increased secretion of chloride ions out of the cell and sodium follows then water and severe diarrhoea occurs
primary endocrine glands?
pineal gland, hypothalamus, pituitary gland, thyroid gland, parathyroid gland, thymus, adrenal gland, pancreas, ovaries, testes
secondary endocrine glands?
heart, stomach, liver, kidney, small intestine, skin
infundibulum?
stalk that connects pituitary to brain
posterior pituitary?
extension of the neural tissue
anterior pituitary
true endocrine of epithelial origin
2 hormones of the posterior pituitary?
ADH - water balance and osmolarity
oxytocin - milk ejection
tropic hormones?
affect the release of another hormone
hypothalamic tropic hormones?
1) blood with tropic hormones enters portal vein
2) hypothalamic tropic hormones access anterior pituitary secretory cells through capillary beds
3) anterior pituitary tropic hormone release altered
4) anterior P. tropic H’s enter bloodstream through capillary bed
5) travel to distant endocrine gland where they trigger releas
melatonin derivative and function?
tryptophan. secreted at night when we sleep, transmits information about light-dark cycles and governs bodies biological clock
pineal gland
secretes melatonin. believed to be involved in circadian rhythms.
two thyroid homrones?
T4, T3 regulate metabolism
calcitonin regulates calcium levels in the blood
parathyroid hormone?
regulates calcium levels in the blood
thyroid hormones made of?
iodine and tyrosine
thymosin?
regulates T cell function. is secreted by the thymus
location of adrenal gland?
on top of kidney
androgens?
sex hormones, secreted by adrenal gland, regulate reproductive function.
Adrenal medulla?
chromaffin cells are the secretory cells.
- 80% epinephrine
- 20% noradrenaline
Addisons disease?
The inability to produce adrenaline. caused by a mutation leading to a defective adrenal medulla.
endocrine function of pancreas?
islets of langerhans: -alpha cells - glucagon -beta cells - insulin delta cells- somatostatin -F cells - pancreatic polypeptide
testes hormones?
testosterone
androstenedione
ovaries hormones?
estradiol
progesterone
suprachiasmatic nucleus?
part of hypothalamus
sites of hormone metabolism?
target cell, blood, liver.
primary and secondary secretion disorders?
primary - abnormality in endocrine organ secreting hormone
secondary - abnormality in tropic hormone
exogenous medication issue?
replaces and exceeds normal, causes atrophy of gland.
permissiveness?
one hormone needed for another to exert its effects
glycogen?
stores glucose
energy output?
heat - 60%
work - 40%
metabolic rate?
energy expended per unit time
basal metabolic rate?
rate of energy expenditure or a person awake, resting, lying down and fasted for 12 hours.
represents minimum energy necessary to maintain body functions
absorptive state?
energy input> output as nutrients have been absorbed.
glucose is the primary energy source for the cell
excess nutrient storage in absorptive state?
liver and muscle store glycogen
adipose tissue stores triglycerides
postabsorptive state?
energy input
insulin?
peptide hormone
secreted from beta cells of islets of langerhans (pancreas)
promotes synthesis of energy storage molecules (anabolic)
promotes glucose uptake by body cells
glucagon?
peptide hormone
secreted from alpha cells of islets of langerhans (pancreas)
promotes breakdown of energy storage molecules
promotes sparing of glucose for nervous system by diverting body cells to utilizing other energy sources
type 1 diabetes?
plasma glucose levels rise, but no insulin is released.
type 2 diabetes?
accounts for 90% of all diabetes
insulin resistance
therapy is diet and exercise as well as some drugs.
3 blood glucose states and levels?
normal - 70-100mg/dL
hyperglycemia > 140mg/dL
hypoglycemia
hormones of growth?
growth hormone
somatomdins (insulin like growth factors)
insulin
thyroid hormones
sex hormones
hypertrophy and hyperplasia?
increase in cell size and increase in cell number respectively
somatomedins (insulin-like growth factors)?
GH stimulates IGF release from liver
IGFs have direct effect on target cells as hormones and paracrines.
growth hormone secretion?
GHRH in hypothalamus stimulates GH release from anterior pituitary.
GH inhibition?
GHIH (somatostatin) inhibits GH release from anterior pituitary
Bone is?
calcium phosphate crystals
bone makers, bone breakers and bone maintainers?
osteoblasts
osteoclasts
osteocytes
formation of bone?
osteoblasts lay down osteoid which then undergoes calcification (depositing of calcium phosphate).
osteoblast becomes immobilised then becomes osteocyte, this maintains the surrounding osteoid
resorption of bone?
osteoclasts secrete acid and enzymes
acid dissolved the calcium phosphate crystals
enzymes degrade osteoid
calcium + phosphate released into blood
increase in bone width?
osteoblasts lay down osteoid on outer surface meanwhile osteoclasts resorb bone in inner surface of cavity to minimize weight gain
increase in bone length?
osteoblasts lay down osteoid at epiphyseal plates
epiphyseal plate?
cartilage between the epiphysis and diaphysis
long bone growth?
chondrocytes produce new cartilage at epiphyseal plate, this widens so bone grows.
chondrocytes then die and osteoblasts replace and lay down bone.
at puberty epiphyseal plates close and no further length increase is possible
acromegaly?
increased GH secretion in adults
thyroid hormones (T4 and T3)?
T4 most abundant, last active, provides long loop negative feedback
T3 not as much made, more active at target tissue.
exopthalmus?
caused by hypertrophy of tissues in the eye socket, it is a sign of hyperthyroidism
treating excess thyroid hormone secretion?
surgical removal of portion of oversecreting thyroid gland
treatment with radioactive iodine - gets concentrated in thyroid gland and selectively destroys thyroid tissue
anti-thyroid drugs
cortisol?
hormone of stress
mobilises energy stores
suppresses immune system
hypersecretion of glucocorticoid?
cushing’s syndrome - protein depletion.
