IPHY3430 Exam 2 [endocrine] Flashcards
Endocrine system
- communication system
- coordinates body function: hormones & endocrine glands/tissues
Endocrinology
someone who studies the endocrine system
Major Glands
- adrenal gland(cortex and medulla)
- gonads (ovaries and testes)
- pancreas
- parathyroid glands
- pineal gland
- pituitary gland
- thyroid gland
Tissues and organs
Not their actual function, but can help/ have a role in the endocrine system •adipose tissue cells •endothelial cells •gastrointestinal tract •heart•kidneys •leukocytes & macrophages •liver •placenta •skin
What can Hormones control
- Rates of enzymatic reactions
- transport of ions or molecules across cell membrane
- Gene expression & synthesis of proteins
Hormone transduction pathways
-cell membrane receptors
•G-protein coupled receptors
•adenylyl cyclase (cAMP) – e.g, glucagon, ACTH, LH, FSH,..
•guanylate cyclase (cGMP)– e.g, ANP, NO,…
•phospholipase C (IP3-Ca++) – e.g, vasopressin, GnRH,TRH,CRH,…
•tyrosine kinase receptors– e.g, insulin, IGF, GH,…
- cytoplasmic/nuclear receptors– e.g, TH, cortisol, E, P, T, …
Endocrine sys function
-Endocrine system has a regulatory effect on basically every other body system.
-Some processes that fall under endocrine system (hormonal) control:
•appetite•blood glucose levels & blood calcium levels•blood pressure & heart rate•growth of bones & tissues•metabolism•reproductive function•water balance & blood volume
Is the endocrine fast or slow
slow
Features of Endocrine sys & hormones
- A single gland/tissue may secrete multiple hormones.
- A single cell typically makes a single type of hormone.
- A particular hormone may be produced by more than one type of endocrine gland/tissue.
- A chemical messenger may be a hormone when secreted by one cell type or neurocrine when secreted by another.
can a hormone exert effects at low concentration
yes, picomole(10^-9) to nanomole(10^-12) = 1 molecule per billion/trillion
Terminating hormone signals
half-life of hormone. but you still need to get rid of it to get rid of all the effects.
- 2 main organs that get rid of hormones:
1) liver: breaks them down
2) kidneys: flushes them out
Function of hormone
endocrine organ secretes hormones, bind to target cell, they can change rate of enzymatic reactions, alter gene expression & synthesis of proteins.
Hydrophilic peptides & catecholamines half- life
t1/2 = fes sec/min
lipophilic hormones half- life
t1/2 = hours/up to a week
3 classes of hormones
peptide, steroid, amine
Peptide hormones
most common; you make them like any other protein: mRNA -> Rough endoplasmic retic -> golgi
Pre-hormone -> prohormone -> hormone
example: insulin
how do hormones vary?
- when synthesized & organelles involved
- how/whether stored & secreted
- half-life & how transported in plasma
- location of receptors, cell signaling mechanism & effects
- timing & duration of effects
peptide hormone characteristics
- water soluble
- bind to surface membrane receptors; many activate cAMP 2nd messenger system(GPCR)
- short half-life; typically seconds to few min
- rapid, short-lived effects: gate ion channels, modify enzymes or transporters
Steroid hormones chracteristics
cholesterol- delivered (lipophilic)
-cant be stored; synthesized on demand- smooth ER & mitochondria
Made only in a few organs: ex; adrenal glands, gonads.
ex hormones: cortisol, estrogen, progesterone, testosterone, estrogen.
Steroid hormones
- all are derived from cholesterol.
- released immediately- rate of synthesis determines rate of release.
- They can just diffuse out of membranes
- cytoplasmic or nuclear receptors (some GPCR or receptor enzymes)
- slower acting, longer effects: typically genomic effects- gene activation -> DNA transcription & protein synthesis
Steroid hormones traveling in the bloodstream
protein carriers:
- what gives steroid hormones such a long half-life. the protein blocks degradation.
Amine hormones
derived from one of two amino acids. (tryptophan or tyrosine)
- act either peptide like or steroid like.
Amine hormones: Tyrosine vs. Tryptophan
tryptophan: converted into melatonin(made in pineal gland)
tyrosine: 1) catecholamines: (peptide like: take a pill)dopamine, epinephrine, norepinephrine
2) Thyroid hormone: (steroid like: take a shot) thyrothyamine
General control of hormone release
Pathway: stimulus -> sensor cell/receptor -> input(afferent) signal -> integration center processes signal -> output(efferent) signal (hormone) -> affector/target -> physiological effect
*signals can be electrical &/or chemical
Simple endocrine pathway
endocrine cell directly senses stimulus, integrates, and responds by secreting its hormone.
- ex; adipose tissue, gastrointestinal tract, heart, kidney, parathyroid glands, pancreas(insulin, glucagon), pineal gland(melatonin)
can be simple neural reflex or simple endocrine reflex , or they can work together
simple neural reflex
stim -> sensory neuron -> CNS -> efferent neuron -> target cell
simple endocrine reflex
stim -> endocrine cell -> blood -> target cell -> response
what do endocrine cells sense when deciding to release Insulin
pancreatic endocrine cells evaluate 3 input signals when deciding whether and how much insulin to secrete.
- blood glucose (humoral)
- stretch in gut(neural)
- glucose in gut (humoral)
complex endocrine pathways: hypothalamic - pituitary (HP) axes
3 integrating centers:
- hypothalamus(neural)
- pituitary; master controller of ES
- endocrine glands; (endocrine target of pituitary hormone) ex: adrenal cortex, thyroid gland,liver, gonads, kidneys
Hypothalamus
Major integrating center:
- links Ns to ES
- receives info about internal well- being of body temp, water balance, hunger.
- much of this is info is used to control secretions of pituitary hormones
Pituitary Glands
pituitary gland is split into 2 different glands: (anterior and posterior)
anterior: epithelials( true endocrine gland)
posterior: neural, extension of the neural tissue
posterior pituitary
stimuli: osmoreceptors; aka “shrink” receptors- mechanically gated
neural tissue: extension of the hypothalamus
secretes: vasopressin, oxytocin
Anterior pituitary
secretes 6 tropic hormones:
prolactin, growth hormone, thyroid,(thyrotropin), adrenocorticotropic( corticotropin), gonadotropins(- luteinizing hormone, follicle-stimulating hormone)
tropic = hormone that controls secretion of another hormone
Hypothalamic neurons secrete releasing hormones that control anterior pituitary
hypothalamic neurons secrete releasing hormones:
•Thyrotropin RH (TRH) -> thyrotropin (TSH)
•Growth Hormone RH (GHRH) -> GH
•Gonadotropin RH (GRH/GnRH) -> gonadotropins (LH, FSH)
•Prolactin Releasing Factors (PRF) -> prolactin
•Corticotropin RH (CRH) -> corticotropin (ACTH)
- to avoid dilution, a portal system(capillary sys) connects the hypothalamus and anterior pituitary
Hypothalamic pituitary axes
Hypothalamus -> releasing hormones(TRH, GHRH, CRH, GRH) -> anterior pituitary gland -> tropic hormones(TSH, GH, ACTH, LH & FSH) -> endocrine cells (thyroid, liver, adrenal cortex, gonads) -> hormone(thyroid hormone, insulin- growth hormone, cortisol, sex hormones) -> cellular response
how are hormone levels kept within desired range?
long-loop feedback; hormone to hypothalamus
short loop feedback; tropic hormone to hypothalamus
control pathway for cortisol secretion (HPA axis)
physical circadian rythm or stress -> hypothalamus -> CRH -> Anterior pituitary(first set of feedback) -> ACTH -> adrenal cortex -> cortisol (last set of feedback) -> to target tissue
Adrenal Gland characteristics
adrenal cortex: outer section, secretes 3 major types of steroid hormones[mineralocorticoids(aldosterone), glucocorticoids(cortisol), sex hormone(a little)]
adrenal medulla: secretes catecholamines (mostly epinephrine) - due to sympathetic nervous system
Hormone interaction types
Cells may be influenced by more than one hormone:
synergism: wehn effects of hormone additive; 1+1=4, greater effect than you expect
Permissiveness: when you need a hormone to get the full effect of another hormone
Antagonism: hormones that have opposite effects
Endocrine pathologies(3 basic things)
1) hypersecretion - hormone excess[tumors/cancer, autoimmune diseases]
2) hyposecretion: hormone deficiency; decreased synthesis, or atrophy of gland [ damage, autoimmune diseases]
3) abnormal reponsivness of target tissue to hormone;changes in receptors or 2nd messenger pathways
cushing’s disease vs addison’s disease
addisons: hypocortisol(anorexia)
cushing’s: hypercortisol(excess fat)
Growth hormone pathologies
Dwarfism: hypo-growth hormone
Hypersecretion:
- in children; leads to gigantism
- in adults; leads to acromegaly(loong face, arms, feet)
*difference is due to growth plates closing.
hypo- vs. hyperthyroidism
-regulates metabolic rate & body temp
- requires for; normal growth & development, protein synthesis, carbohydrate & fat breakdown
THERE ARE A LOT OF THINGS THAT ARE AFFECTED BY HYPO AND HYPERTHYROIDISM
Classification of endocrine pathologies
primary pathology; dysfunction of endocrine gland
secondary pathology; dysfunction of pituitary
tertiary pathology; dysfunction of hypothalamus
