Endocrine System Flashcards
what is the endocrine system?
all the organs and tissues that release hormones
what is an endocrine gland
system of ductless glands that make hormones
why are endocrine glands ductless
secretions are released into blood straight away
give an example of an organ that secretes hormones
pancreas
give example of pure endocrine gland
Pituitary/Pineal/Thyroid/Parathyroid/Adrenal with 2 glands medulla and cortex
give examples of endocrine cells in other organs
Pancreas/Thymus/Gonads/Hypothalamus
what is the difference between purely endocrine glands and endocrine cells in other organs?
pure endocrine just endocrine whereas endocrine cells in other organs mean they serve both endocrine and exocrine
what is the difference between endocrine and exocrine
endocrines do not have ducts whereas exocrines do, endo just release hormones whereas exocrine release sweat enzymes and mucus
endocrine products released directly into blood stream whereas exocrine are released into an internal organ or external surface through a duct
give examples of endocrine
thyroid,parathyroid,pituitary/adrenal
give examples of exocrine
saliva/liver/oesophageal glands
describe the 3 elements of endocrine system
chemical which mean hormones are sent to messengers/ remote communication system/control a huge no of physiological processes
what are the components of the endocrine system
endocrine glands and hormones
what are endocrine glands
ductless glands, comprised of endocrine cells, releasing blood directly into blood stream
what are pheromones
hormones outside of the body signalling to others of same species
what do pheromones relate to in animals
alarm/food/sex
what are hormones
organic chemical messengers made by endocrine cells secreted into blood stream
how do hormones work
hormones regulate/integrate and control physio functions
how do hormones travel in body
circulate in blood, theyre long distance messengers, and act on distant target cells
whats the difference between autocrine and paracrine
autocrine activates same cell, whereas paracrine activates neighbouring cells
what is autocrine and paracrine signalling
when a cell acts as a self regulator or regulates neighbouring cells
what are target cells
cells that contain a specific receptor for a particular hormone
where are hormone receptors
on target cells
where can hormone receptors be found
surface,cytoplasm,nucleus
how are target cells activated
when specific hormones bind to them
what happens if a hormone cannot bind or does not bind to receptor
no physiological results
how do hormones work
activate a specific response in a specific target cell
give the stages of the programmed response of target cells
bind to receptor=receptor hormone complex / enters nucleus / acts as a trasncription factor binding to DNA/ activates or represses one or more genes / forms a cell type specific
what is a cell type specific
specific phenological/ morphological functions
give different actions of hormones
fetal growth/cell growth and cancer/metabolism/cardiovascular function/renal function/skeletal function/reproductive function/immune function/cns function
describe the 3 hormone classifictaions
peptide / amino acids derivatives/ steroid hormones
what are lipophilic hormones
non polar hormones that are fat soluble that bind to intracellular recptors
give examples of lipophilic hormones
steroid and thyroid hormones
why can lipohillic hormones bind to intracellular receptors
can pass the lipid bilayer of cells
what is a hydrophillic hormone
polar watre soluble hormone
give examples of hydrophobic hormones
all other hormones that are not steroid or thyroid
where do hydrophillic hormones bind to
extra cellular receptors
what are peptide hormones
hormones comprimised of amino acids
where are peptide hormones synthesized
ribosomes on the rough endoplasmic reiticulum
where can peptide hormones be stored
in vesicles
why cant peptide hormones readily pass through cell membrances
because theyre water soluble
where are peptide hormone receptors found
cell surface of target cells
why do peptide hormones bind to receptors on surface target cell
theyre not lipid soluble
what are the 3 amino acid derivatives
tyrosine/thyroid hormones/tryptophan
give examples of tyrosine derivatives
catecholamines eg epinephrine/norepinephrine/dopamine
give examples of thyroid hormones
t4 thyroxine / t3 triidothyronine
give examples of trytophan derivatives
melatonin
What are steroid hormones produced by?
gonads, adrenal cortex and kidneys
what are steroid hormones derived from
cholestrol
can steroid hormones be stored in vesicles in the endo system that produce them
no
are steroid hormones lipid soluble
yes
where are steroid hormones receptors located
inside their target cell
what are the two types of steroid hormones
adrenal and sex hormones
what is homeostasis
process of keeping inside body steady and balanced
what happens to blood vessels when body temp rises
blood vessels open= heat is lost to outised environment, sweat glands seceret fluid = heat lost = body temp decreases= normal body temp
what happens when temperature of body falls
blood vessels get smaller = heat is not lost body starts to shiver= produces heat and so temp rises
what is the process of fine regulation
constant monitoringof homeostasis and adjustments in neural and endocrine control
what is negative feedback
body turns off signal in response to change in body
is negative feedback homeostatic or not
its homeostatic
what is positive feedback
signal starts another signal
give and example of positive feedback
childbirth
give an example of negative feedback
regulation of thyroid levels
what happens in the negative feedback cycle
level of hormones control its own production/ secretion
what are the 3 examples of neurohormones
neurotransmitters/hormones produced by neurons/releasing hormones
what are neurotransmitters
neurohormones that are released into blood by chromaffin cells
where are chromaffin cells found
medulla of adrenal glands
give an example of hormones produced by neurons
oxytocin and vasopressin produced in the hypothalamus, transported to the posterior pituitary
give examples of releasing hormones
growth hormone releasing which is produced in the hypothalamus and travels to anterior pituitary
what do releasing hromones stimulate
a gland instead of a target organ
what are the three mechanisms of hormone release and explain them
humoral- response to changing levels of ions or nutrients in blood
neural -stimulation by nerves
hormonal- stimulation recieved by other hormones
what does the endocrine system comprise of
primary and secondary endocrine organs
what are hormones
chemical signals that enter blood and act as distant target sites
what are the two main regulators of the endocrine system
hypothalamus and endocrine system
what is the normal pathway of hormones
hypothalamus- activate pituitary gland= pituitary release hormone = activate end organ
what 2 mechanisms control hormone release
+/- feedback
where is the pituitary gland located
underneath brain, behind bridge of nose
what is another name for pit gland
hypophysis
what is the name for the anterior pit gland
adenohypophysis
what is the name for the posterior pit gland
neurohypophysis
what is the posterior pit gland attached to?
hypothalamus
describe the anterior pit gland
true endocrine gland, pit gland composed of 6 distinctive endocrinocytes, under control by the hormones released by hypothalamus, portal veins carry blood from hypothalamus to pituitary
what is the hypophyseal portal system
communicates the HYPO AND ANTERIOR PITUITARY, hyp secrete hormones=start/stop secretion of anterior pit
where are pepride hromones synthesised
cell body of hypothalamic neuros
in neurohypophysis, where are the hormones released
into the hypophyseal vein
what hormones does the anterior gland release
tsh/adrenocorticotropic hormone/fsh/lh/prolactin/growth hormone
what does the posterior gland release
adh( antidiuretic hormone) and oxytocin
what is the role of prolactin
breast development and milk production, found in low levels in Both males and females
what is the role of growth hormone
growth and puberty/ levels decrease through life span
what is the role of the adrenocorticotrophic hormone
stimulates adrenal glands to release corticosteroids, responding to stress
what is the role of thryoid stimulating hromone
stimulates thyroid release, involved in regulating metabolism
what is the role of leutinizing hormone
ovulation and stimulates androgen release by testis
what is the role of fsh
growth and oestrogen production from ovary and stimulates sperm follicle production
what does adh control
water retention and vesse constriction
what does oxytocin control
uterine contraction and breast feeding
what does the hypo secrete
releasing hormone- stimulate the making and releasing of 1 or more hormones in ant pit gland
inhib hormone- prevent synth and release of hormones by ant pit gland
where does the hyp recieve input from
cortex/thalamus/limbic system
what does dopamine inhibit
prolactin
what would happen if the pit glands fail
diabetes=too little ADH
Acromegaly=too much GH in Adulthood
Gigantism= too much GH in childhood
what are the causes and symptoms of gigantism and acromegaly
too much GH made=bigger thicker broader bones= anterior pit tumours
where is the thyroid gland located and what is its role
anterior neck trachea,two lobes and an isthmus,
produces two hormones T3/T4 ,
Calcitonin = calcium and phosphorus metabolism
explain structure of thyroid gland
follice cells which produce thyroglobulin forming a colloid lumen
parafollicular c cells produce calcitonin
Explain the production of T3/T4
Follicular cells make enzymes and thyroglobulin for colloid cells
Iodine is co transported into cell with na to reach colloid
iodine + thyroglobulin= t3/t4
thyroglobuln taken back into cell
intracellular enzymes separate t3/t4 from protein
t3/t4 free to enter blood stream
in Binding selectivity, what do nuclear receptor for TH prefer to bind to and why
T3 because it is more potent
what does T3 deficeincy cause
hypothyroidism
whats the role of t4
pro hormone
what is a prohormone
precursor of a hormone,
doesnt make much of aneffect by itself, travelling in blood in inactive form
what does t4 act as
a reservior
compare half lives of t3 and t4
t3 half life very short, t4 5-7 more stable than t3
what are the action of t3 + t4?
Control basal metabolism rate = increasing oxygen and energy consumption at rest
in fetal development, promotes protein synthesis growth and skeletal maturation
what can a deficiency in t3/t4 lead to
cns damage if not corrected by mid gestation
list some effects of t3/t4 deficiencies
tremors/nervousness hyperactivity/decrease in blood cholesetrol / increased temperature
describe the effects of calcitonin in regulating calcium levels
secreted from thyroid parafollicular c cells = slows down the calcium releasing activity of osteoclasts in bone
what is a goitre
swelling of thyroid gland= lump in neck, caused by iodine deficiency= hyper/hypo thyroidism
what is hyperthyroidsim
overactive thyroid, too much thyroid
causes unexplained, unplanned weight loss nervousness and anxiety, hyperactivity
what is the cause of graves disease
IgG antibodies produced against the thyrotropin receptor= mimc action of tsh=stimulation of gland= uncontrolled production of t3/t4
what are the cellular changes related to grave’s disease
hypertrophy/hyperplasia
what effect do autoantibody receptors have on hormone synthesis
unregulated/overproduction of thryoid hormones
what are the causes of hypothyroidism
surgery of glands and inflammation of thyroid gland
explain what is meant by inflammation of thyroid gland
large percent of cells damaged or dead= not enough hormone produced
what is hashimoto’s thyroiditis
auto immune thyroiditis= thyroid inflamed as aresult of immune system attacking itself
what are some symptoms of hyperthyroidism
muslce fatigue, problems sleeping,nervousness
what are the treatments for hyperthyroidism
antithyroid methimazole +propylthiouracil = stop thyroperoxidase which is required for addition of iodine to tyrosine
radioactive iodine
beta blockers for symptome control
surgery= thyroidectomy
what are some symptoms of hypothyroidism
depression, cold intolerance , tiredness
what are the treatments for hypothryoidism
levothyroxine, manufactured form of t4
where are parathyroid glands located
on posterior surface of thyroid gland
what is the function of cheif cells
produce PTH (parathyroid hormone and peptide hormone)
what type of cells are in parathyroid glands
chief and oxyphil cells
what is the function of PTH
maintains blood conc of ca2+,
when blood calcium is low, stimulates osteoclats to release ca2+ from bone = lower secretion of ca2+ by kidney= activates vitamin d which stimulates uptake of ca2+ from intestine
what is the main cause of hypoparathyroidism
low calcium and low pth
what is the cause of hyperparathyroidism
low calcium, high levels of PTH
what is the cause of Independent Hypercalcemia
high calcium levels, low PTH levels
what is the cause of hyperparathyroidism
high calcium and PTH
where are adrenal glands located
top of kidney
what is the difference between adrenal cortex and medulla
cortex=outer
medula = inner
what is aldosterone
steroid hormone synthesised in adrenal cortex in response to a decline in either blood volume or blood pressure
where is the the action site for aldosterone
principal cells of the cortical distal tubules and collecting duct
what is the effect of aldosterone
kidneys retain na+ and water reabsorption
k+ secretion
what is the mechanism of action for aldosterone
a combines with cytoplasmic receptor
starts transcription in nucleus
new protein channels and pumps made
aldosterone induced proteins modify existing proteins
= increased na reabsorption and k+ secretoion
explain the hormone cortisol
glucocorticoid, essential for life, helps body deal with stressful situations within minutes
regulates cardiovascular, metabolic, immunologic and homeostatic body function
what is the role of cortisol on the brain
keeps glucose levels high enough to support brain activity
forces other body cells to switch to fats and amino acid for energy
catabolic=breakdown protein
how does cortisol affect immune system
redirects circulating lymphocytes to lymphoid and peripheral tissues
can depress immune and inflammatory response = therapeutic use
what happens in the stress cycle
hypo releases CRH anterior releases ACTH
ACTH goes to adrenal cortex= glucocorticoid secretion
DHEA converted in peripheral tissues to testosterone and estrogen + steroid hormones
what is a cause of excess secretion of cortisol
cushings syndrome, caused by ACTH secreting pit tumour
what happens when cortisol production reduced
addisons disease = low cortisol, aldosterone, blood glucose and sodium
what are the symptoms of cushing syndrome
red round face, obesity,skin ulcers, muslce wasting
what are the symptoms of addisons diseas
hyperpigmentation, low blood sugar, adrenal crisis
