Endocrine System Flashcards
what does the endocrine system include
-all endocrine cells and tissues that produce hormones or paracrine
-endocrine organs are scattered throughout the body
-endocrine cells and tissues produce about 30 different hormones
-hormones control and coordinate body processes
where do endocrine cells release secretions
-into extracellular fluid
-exocrine cells do not release into extracellular fluid
endocrine organs and tissues of the head and neck
endocrine cells and tissues of the trunk
mechanisms of intercellular communication
-direct
-paracrine
-autocrine
-endocrine
direct communication
-excahneg of ions and molecules between adjacent cells across gap junction
-occrs between two cells of the same type
-highly specialized and relatively rare
autocrine communication
-messages affect the same cells that secrete them
-chemicals involves are autocrines
e.g: prostaglandins secreted secreted by smooth muscle cells cause the same cells to contract
endocrine communication
-endocrine cells release hormones that are trasnported in bloodstream
-alters metabolic activities of many organs
target cells
have receptors needed to bind and read hormonal messages
hormones
-changes types, quantities or activities of enzymes and proteins in target cells
-can alter metabolic activites of multiple tissues and organs at the same time
-affect long term processes like growth and development
similarities between endocrine and nervous system
-rely on release of chemicals that bind to specific receptors on target cells
-share many chemical messengers
-are regulated mainly by negative feedback
-function to preserve homeostasis by coordinating and regulating activities
classes of hormones table
amino acid derivatives
-small molecules
-related to AA
-derivatives of tyrosine include thyroid hormones, and caecholamins like epi, norepi, and dopamine
-derivatives of tryptophan include serotonin and melatonin
peptide hormones
-chains of AA
-most are inactive converted to active hormones before or after they are secreted (prohormones)
-glycoproteins = >200 AA and have carbohydrate side chains (TSH, LH, FSH)
-short polypeptides and small proteins are ADH and OXT (9AA)
-small proteins include insulin, GH, Prolactin
-all hormones secreted by hypothalamus, heart, thymus, GI, pancreas, posterior pit,
Lipid derivatives
-eicosanoids
-steroid hormonez
eicosanoids
-derived from arachidonic acid (20C FA)
-paracrines that coordinate cell activities and affect enzyme activity
-some eicosanoids act as hormones as well
-prostglands coordinate local cellular activities
steroid hormones
-include: androgens, esteogens and progesterone, corticosteroids, calcitriol
-bound to specific transport proteins in the plasma and remain in criculation longer than peptide hormones
catecholamines and peptide hormones
-not lipid solible
-cannot penetrate plasma membrane
-bind to receptor proteins on outer surfacee of plasma membrane
notes abotu steroid and thyroid hormones
-lipid soluble
-diffuse across plasma membrane and bind to receptors inside cell
free hormones
-remain functional for less than an hour and are inactivated when they:
-diffuse out of bloodstream and bind to target
-are absorbed or broken down by liver or kidneys
-are broken down by enzymes
thyroid and steorid hormones transport and activation
-remain functional much longer
-more than 99% become attached to special transport proteins in blood
-equilibirum state exists between free and bound forms
-bloodstream contains substantial reserve of bound hormones
binding of hormone may:
-alter genetic activity
-alter rate of protein synthesis
-change membrane permeability
hormone receptor
-a protein molecule to which a particular molecule binds strongly
-different tissues have different combinations of receptors
-presence or absence of specific receptor determines hormonal sensitivity of cell
down regulation
-presence of hormone triggers decrease in the number of hormone receptors
-when levels of a particular hormone are high, cells become less sensitive to it
up-regulation
-absence of hormone triggers increase in the number of hormone receptors
-when levels of a particular hormone are low, cells become more sensitive to it
first messenger
-hormone that binds to extracellular receptor
-promotes release of second messenger
second messenger
-inteermediary molecule that appears due to hormone receptor interaction
-may act as enzyme activator, inhibitor or cofactor
-results in change rates of metabolic reactions
-e.g cAMP, cGMP, Ca2+
G proteins and second messengers photo
steps in increasing cAMP level, which accelerates metabolic activity of cell
- activated G protein activates adenylate cyclase
- adenylate cyclase converts ATP to cyclic AM
3.cyclic amb functions as a second messenger
4, generally cyclic AMP activates kinases hat phosphorylates protein
-
enzyme that converts cAMP to AMP
-phosphodiesterase
-acts quickly - increased cAMP levels short lived
G proteins and calcium ions
-G protein activates phospholipase C (PLC)
-triggers receptor cascade beginning with production of DAG and Inositol triphosphase (IP3) from phospholipids
-IP3 diffuses into cytoplasm and triggers release of CA2+ from intracellular reserves
-calcium ion channels open due to activation of protein kinase C and CA enters cell
-Ca binds to calmodulin
hormones and intracellular receptors
-steroid hormones can alter rate of DNA transcripstion in nucleus
-alterations in synthesis of enymes or structural protein directly affect activity and strucutre of target cell
-thyroid hormones bind to receptors within nucleus and on mitochondria activationg genes or changing rate of trasncription, increasing rate of ATP production
steroid hormones photo
thyroid hormones photo
hormone secretion
-mainly controlled by negative feedback
-can be triggered by: humoral stimuli, hormonal stimuli, or nueral stimuli
humoral stimuli
-change in extracellular fluid
control of hormone secretion
-may involve only one hormone
-humoral stimuli controls hormone secretion by heart, pancreas, parathyroid gland and GI
-hormonal stimuli may involve one or more intermediary steps and have two or hore hormones involved
-nueral stimuli
Orientation and anatomy of the pit gland photo
blood supply to pit gland photo
the hypothalamus
-regulates functions of the pituitary gland
-synthesises ADH and OXT and transports them to posterior pit for release
-secretes regulatory hormones that control secretory activity of anterior pit
-contains autonomic centers that exert control over adrenal medulla
releasing hormones diagram
5 hormones of anterior pit
-TSH
-ACTH
-PRL
-GH /somatotropin
-Gonadotropins
gonadotropins
-FSH
-LH
-GnRH
hypogonadism
caused by low production of gonadotropins
LH functions
-in females induces ovulation and stimulates secretion of estrogens and progesteron
-males stimulates production of androgens
hormones diagram
PIH and PRL interaction photo
growth hormone stimulates
-liver cells to release somatomedins that stimulate tissue growth
-stem cells in epithelia and connectibe tissues to divide
-breakdown of triglycerides in adipocytes which leads to glucose sparingn effect
-break down of glycogen by liver cells. causing diabetogenic effect
somatomedins
-cause skeletal muscle fibers and other cells to increase uptake of AA
production of growth hormone refulated by
-growth hormone releasing hormone
-growth hormone inhibiting hormone
pars intermedia
-secretes melanocyte stimulating hormone
-virtually nonfunction in adults excpeti in pregnant women and those with certain diseases
posterior lobe of pit gland
-called nuerohyphysis
-contains unmyelinated axons of hypothalamic nuerons
-supra-optic manufactures ADH
-paraventricular nuclei manufactures OXT
oxytocin
-stimulates contraction of uterus during labour
-promotes ejection of milk after delivery
thyroid gland
-lies inferior to thyroid cartilage of larynx
-two lobes connected by isthmus
-c cells or parafollicular cells
thyroid follicles
-hollow spheres lined by cuboidal epithelium
-surrounded by capillaries
-cells absorb iodied ions from blood
-follicle cavity contains viscous colloid
thyroglobulin
globular potein synthesized by follicle cells
-secretes into colloid of thyroid follicle
-contains tyrosine
two thyroid hormones
-thyroxine contains four idoine atoms
-triiodothyronine contains three idoine atoms
thyroid gland photo
syntehsis storage and secretion of steorid hormones
homeostasis of t3 and t4 concentration
thyroid hormones effects
-elevate oxygen and energy consumption
-may cause rise in temp in children
-increase HR and force of contraction
-increase sensitivity to sympathetic stimulation
-maintain normal sensitivity of respiratory centers to [O2] and [CO2]
-stimulate red blood cell formation
-stimulate activity in other endocrine tissues
-accelerate turnover of minerals in bone
where do thyroid hormones bind
-in cytoplasm
-on surfaces of mitochondria
-in nucleus
why are thyroid hormones essential in children
-essential to normal development of skeletal muscualr and nevrous system
C cells
-thyroid
-produce calcitonin
calcitonin
-helps regulate concentration of Ca2+ in body fluids
-stimulates Ca2+ excretion by kidneys
-prevents Ca2+ abdosrption by digestive tract
thryoid hormones involvement in glycolysis and ATP production
-results in calorgenic effect - increased energy consumption and heat generation of cells
-responsible for strong immediate, and short lived increased rate of cellular metabolism
parathyroid glands
-two pairs
-embedded in posterior surface of thyroid gland
-all four glands together weigh 1.6g
parathyroid hormone
-secretes by paraythroid (principle) cells in response to low concentrations of Ca2+ in blood
-antagonist for calcitonin
-stimulates osteoclasts (turnover of bone, Ca2+ release)
-enhances reabsorption of Ca2+ by kidneys reuding urine losses
-stimulates formation and secretion of calcitrol by kidneys
homeostasis of blood calcium photo (increased blood ca)
homeostasis of blood calcium (decreased blood ca)
superifical adrenal cortex
-storage of lipids especially cholesterol and fatty acids
-manufactures steroid hormones
inner adrenal medulla
-secretory activities controlled by sympathetic division of AND
-produces epi and norepi (catecholamines)
adrenal cortex
-subdivided into three zones
-outer z. glometulosa, middle zona fasiculata, inner zona reticularis
zona glomerulosa
-outer region of cortex
-produces aldosterone
aldosterone
-stimulates conservation of sodium ions and elimation of potassium ions
-increases sensitivity of salt receptors in taste buds
-secreted in response to drop in blood sodium, blood volume, or blood pressure, rise in blood K
zona fasiculata
-produces glucocorticoids (cortisol, corticosterone, cortisone)
glucocorticoids have inhibitory effect on production of
-corticotropin-releasing hormone in hypothalamus
-ACTH in anterior pituitary
zona reticularis
-branching network of endocrine cells
-forms narrow band bordering each adrenal medulla
-produces small quantities of androgens under stimulation by ACTH some converted to estrogens, and they stimulate the devvelopment of pubic hair before puberty
adrenal medulla
-two types of secretory cells: one producing epi (75-80% secretion), other produces norepinephrine (20-24%)
results of activation of adrenal medulla
-in skeletal muscles, E and NE trigger mobilization of glycogen reserves and accelerate breakdown of glucose
-in adipose tissue, stored fats are broken down into fatty acids
-in the liver, glycogen molecules are broken down
-in heart stimulation of B1 receptors speeds and strengthens cardiac muscle contraction
adrenal hormones chart
pineal gland
-lies in posterior portion of roof of third ventricle
-contains pinealocytes that synthesize melatonin
functions of melatonin
-influence circadian rhymthms
-inhibit repro functions
-protect against damage by free radicals
exocrine pancreas
-consists of clusters of gland cells called pancreatic acini and their attached ducts
-takes up 99% of pancreatic volume
-gland and duct cells secrete alkaline enzyme rich fluid to go to the digestive tract
endocrine pacreas
-consists of pancreatic islets:
-alpha cells produce glucagon
-beta cells produce insulin
-delata cells produce peptide hormone identicle to GH-IH
-pancreatic polypeptide cells produce pancreatic polypeptide
flucutation of blood glucose results
-beta cells secrete insulin stimulating transport of glucose into target cells
-when blood glucose level decreases alpha cells secrete glucagon stimulating glycogen breakdown. and glucose release by liver
increased blood glucose photo
decreased blood glucose level photo
insulin
-peptide hormone released by beta cells
-accelerate glucose uptake
-accelerate glucose use and enhance ATP production
-stimulate glycogen formation
-stimulate AA absorbtion and protein synthesis
-stimulate triglyceride formation in adipocytes
glucagon
-released by alpha cells
-mobilizes energy reserves
-stimulate breakdown of glycogen in skeletal muscle fibers adn liver cells
-stimulate breakdwon of triglycerides in adipocytes
-stimulate production and release of glucose in liver cellsh
hyperglycemia
-abnormally high glucose levels in blood
diabetes mellitus
-high glucose concentration that overwhelm reabsorbtion capibilities of kidneys
-glucose in urine
-polycuria - high urine volume
type I diabetes mellitus
-inadequate insulin produced by beta cells
-patients require daily injectiosn or continous infusion of insulin
-5% of cases
-children and young adults
type II diabetes mellitus
-most common
-usually normal amounts of insulin are produced at least initially and tissues develop resistance
-associated with obesity
-weight loss effective treatment
complications of untreated or poorly managed diabetes mellitus
-kidney degenration
-retinal damage (diabetic retinopathy)
-early heart attacks
-peripheral nerve problems (diabetic neuropathies)
-peripheral tissue damage due to reduced blood flow
intestines secondary endocrine functuon
-release hormones that coordinate digestive activities
kidney secondary endocrine function
-release the hormones calcitriol and eryhtropoietin
-release renin
renin
-converts angiotensin to angiotensin I
-in lungs angiotensin converting enzyme. onverts angiotensinI to angiotensin II
production of calcitriol photo
decreasing blood pressure and volume homesostatic mech
secondary endocrine function of heart
-production of ANP and BNP
-blood volume becomes excessive
-actions oppose angiotensin II
-results in lower blood volume and pressure
secondary endocrine function of thymys
-thymosin
-promote development and maturation of lymphocytes
secondary endocrine function of adipose tissue
-leptin
-feedback control of appetite
-maintains normal levels of GnRH and gonadotropin synthesis
secondary endocrine function of testes
-androgens by intersitial endocrine cells
-nurse/sertoli cells secrete inhibin and support sperm
secondary endocrine function of ovaries
-estrogens
-follicle cells reorganize into CL and release estrogens and progesterone
four outcomes when cell recieves instructions from two hormones at same time
-antagonistic effect - result depends on balance between two hormones
-synergistic effect - additive effect
-permissive effect - one hormone is needed for another to produce effect
-integrative effect - hormones produce different but complementary result
hormones important to growth
-growth hormone
-thyroid hormone
-insulin
-PTH
-calctriol
-repro hormones
growth hormone in children and in adults
-child: muscular and skeletal developmetn
-adult: maintain blood glucose concetration, movilize lipid reserve
result of thyroid hormone absent during fetal development or dor first year after birth
-nervous system failure to develop
-development delay results
-if T4 concentration decline before puberty normal skeletal development does not continue
insulin in growth
allows passgae of glucose and AA across plasma membrane
-important for growing cells
PTH and calcitriol in growth
promote absorbtion of calcium salts from bloodstream for deposition in bone
-inadequate levels result in weak flexible bones
reproductive hormones in growth
-stimulate growth and differentiation in target tissues
-produce gender differences in skelton and secondary sex characteristics
stress
-any condition that threatens homeostasis
general adaptation syndrome
-stress response
-how body responds to stress causing factors
three phases: alarm, resistance, exhaustion
alarm phase oef GAS
-immesdiate response
-symapthetic division of AND
-energy reserves are mobilized
-body prepares for fight or flight
-epinephrine is domiannt
resistant phase of GAS
-stress longer than few hours
-weeks or months
-glucocrticoids are dominant
-lipids and AA are mobilized for energy
-glucose is conserved for use for nervous tissue
exhaustion phase of GAS
-begins when homeostatic regulation breaks down
-drop in K levels due to aldosteron produce in resistance phaw
-failure of one or more organ systems will be fatal
hormone changes can effect
-behaviour
-intellectual capacilities
-memory
-learning
-emotional states
age relatd wchanges
-repro hormones decline in concentration
-some endocrine tissues become less responsive to stimulation
