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Homeostasis

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preserved and coordinated by intercellular communication

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Nervous system

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fast; seconds (short-term) uses electrical impulses; synaptic communication (neurotransmitters) short lived bc broken down quickly effects specific muscles and glands

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Endocrine system

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slow; hours or decades (long-term) uses chemical messengers (hormones) sustained, long-term basis much broader effect

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Indirect communication

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involves release and receipt of chemical messengers; cells "talk" to each other by releasing chemicals into the extracellular fluid= paracrine communication/local hormones ex: prostaglandins which diffuse out of tissue

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Direct communication

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b/w 2 cells in direct physical contact -rarer (gap junctions)

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Neural communication

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immediate response (crisis management); short term effects delivery: at synapse by NT -> action potentials

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Endocrine communication

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slow response; long term effects; gradual (growth) delivery: in bloodstream by hormones (chemicals produced in one tissue w/ effects elsewhere..target cells w/ receptors)

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Paracrine communication

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release of factors (chem. structure not known) ex: interleukin 2- released by T cell that activates nearby immune cells

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NO (nitrous oxide)

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released by endothelial cells lining blood vessels; releases smooth muscle causing vasodilation. Drug- viagra or blood pressure drugs delivery: diffusion through extracellular fluid; limited to immediate areas

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Direct communication

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gap junctions allow passage of ions and small mol. (lipid soluble); limited to adjacent cells

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Similarities of endocrine and NS

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-both rely on release of chemicals that bind to specific receptors -share many of chem messengers; norepinephrine and epinephrine called hormones when released into bloodstream and neurotransmitters when released across synapse -controlled through neg feedback systems -preserve homeostasis by coordinating and reg activities of other cells, tissues, organs and systems

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Endocrine cells

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ductless secretions released into extracellular fluids (interstitial)-> blood -> target cell -> specific receptor 1. hormones ( long distance) 2. paracrine factors (short distance)

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Exocrine cells

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secretions occur through ducts; deposited where it needs to act: dig: salivary gland -> saliva sudoriferous glands, sebaceous glands, mucous glands

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hormones; endocrine communication

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release of chemicals that are released from one tissue and transported in the bloodstream to alter the activities of specific cells in other tissues

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hormone

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substance with effects outside its tissue of origin if its chemical structure is known

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factor

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if structure remains to be determined

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hormones

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have target cells that contain specific receptors that bind and "read" the hormonal message that alters the "behavior" of that cell

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Role of hormone receptors

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hormones only affects specific target cells by chemically binding to specific ptn receptors (only target cells for a given hormone have receptors that bind and recognize that hormone) target cells have 2000-100,000 receptors for particular hormone which are constantly being synthesized and broken down (turnover)

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Down-regulation

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if too much hormone is circulating, receptor numbers decrease (cell is less sensitive)

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Up-regulation

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if too little hormone is circulating, then makes more receptors making cell more sensitive to the hormone

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Drugs & hormones

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certain drugs act as synthetic hormones, blocking the receptors from a naturally occuring hormone Ex: mimic Ex RU486 induces abortion by binding to receptors for progesterone that prepares uterus for implantation of egg; taxol drugs mimic estrogen

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Hormone action

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hormones act as chem messengers that act on specific target tissue/cells to bring about a second type of internal coordination -bind strongly w/ specific ptns called receptors; presence or absence of diff receptors determines cells hormonal sensitivity and response

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Target cell specificity of hormones

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though a hormone reaches every part of the body, each hormone acts only on one type of target cell w/ specific protein receptors

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half life of hormone

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hormones released into blood, hormone remains active only for a short period; some last only few seconds, others up to a few hours at end of period is degraded by cellular enzymes, or by liver or kidney

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Mechanisms of hormone action

answer

hormones interact w/ appropriate receptor (ptn molecule) on membrane of target cell -every cell has receptors for responding to several different hormones but cells of diff tissues have diff combinations of receptors

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hormonal sensitivities

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hormones have differential effects on specific tissues

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Hormone receptors found on:

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plasma membrane (outer surface= extracellular receptors) catecholamines (E, NE, dopamine)- peptide hormones; not lipid soluble, unable to penetrate plasma membrane -inside the cell (inner surface= intracellular receptors)- eicosanoids

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Hormones

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alter the operations of target cells by changing type, quantities, or activities of important enzymes and structural proteins in many cells simultaneously

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Hormone function

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-synthesis of an enzyme or structural protein not present by activating genes in nucleus -increase or decrease rate of synthesis of protein or enzyme by changing the rate of transcription or translation -turn an existing membrane channel or enzyme channel "on" or "off" by changing its shape or structure

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Pheromones

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effect other people through olfactory mechanism

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Prostaglandins

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effect the next cell (paracrine); stimulate contractions in smooth muscle tissue (intestines, uterus, female reproductive tract, ductus deferens (ejaculation of semen), stimulates homeostasis= blood clotting, stimulates inflammation response, vasodilation, capillary permeability)

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NSAIDs- nonsteroid anti-inflammatory drugs

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inhibit prostaglandins synthesis by binding to the prostaglandins 1. Ibuprofen= motrin, nuprin, advil 2. aspirin 3. naproxen= aleve 4. ketoprofen= arudis KT

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Amino acid derivatives

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small molecules structurally related to amino acid- catecholamines synthesized from amino acid

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Tyrosine- aa derivative

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1. thyroid hormones; insulin 2. epinephrine, norepineprine, dopamine

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Trytophan- aa derivative

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melatonin and serotonin

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Peptide hormones

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chains of aa that are inactive (prohormones) -> active hormones glycoproteins: 200+ aa w/ carb side chain - TSH- thyroid stimulating hormone (glycoprotein) - LH- luteinizing hormone - FSH- follicle stimulating hormone

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Short peptide chains

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ADH: antidiuretic hormone oxytocin GH- growth hormone PRL- prolactin

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Lipid derivatives

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eicosanoids- 20 C fatty acid w/ 5 C ring at one end 1. leukotrienes- released by WBC in response to injury or disease 2. prostaglandins- coordinates cellular activities steroids- derived from cholesterol; in blood bound to specific transport ptns which liver removes released by reproductive organs -androgens by testis -estrogen and progesterone by ovaries by suprarenal glands (coricosteroids), by kidneys

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Freely circulating hormones

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remain functional for less than one hour and sometimes as little as 2 minutes

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Thyroid and steroid hormones

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circulate the longest bc get attcahed to special transport proteins

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Inactivation occurs:

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-diffuse out of bloodstream and bind to target cells - breakdown by enzymes in the plasma or interstitial fluid - absorption and breakdown by liver or kidney

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Amino acid based hormones

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hydrophilic- can't cross the cell membrane unless there is a membrane bound receptor

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Steroid hormones

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hydrophobic- CAN cross the cell membrane by using a cytoplasmic receptor

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2 diff ways 2 groups of hormones influence target cell chemistry:

answer

1. by using second messenger 2. by direct gene action

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Amino acid based hormones cont.

answer

do not enter target cells, instead bind extracellular, with receptors on plasma membrane of target cells 1. made of single aa (glycine, glutamate) 2. short chain of aa (peptide hormones) 3. long chain of aa (insulin, growth hormone)

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Steroid hormones cont.

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derived from cholesterol and as they are lipid soluble, can enter target cells by diffusion and bind w/ intracellular receptors of target cells

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these 2 hormones alter target cell chemistry:

answer

1. changing membrane potential, and causing ion flow into or out of target cells 2. activating or deactivating cellular enzymes 3. inducing ptn synthesis in target cells 4. inducing secretory activity of target cells 5. initiating mitotic division

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Hormone activity

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hormones that bind to receptors on plasma membrane must use an intracellular intermediary to effect the cell - first messenger->second messenger-> activates enzyme, acts as inhibitor or cofactor, changes rate of various metabolic rxns

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Important second messengers

answer

cyclic AMP (cAMP)- derivative of ATP clyclic GMP (cGMP) calcium ions

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G-protein

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link b/w first messenger and second messenger usually involves this protein which binds GTP - 80% prescription drugs target G protein-coupled receptors

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amplification

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binding of small number of hormone molecules to mem receptors may lead to appearance of many thousands of second messengers in cytoplasm

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receptor cascade

answer

release of more than one kind of second messenger produces a linked sequence of enzymatic rxns

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G-protein activation

answer

when water-soluble hormone molecule (most amino-acid based hormones, cept thyroid hormones) binds with receptor on plasma membrane of target cell

question

adenylate cyclase

answer

activated when G-protein is activated; acts on ATP in target cell and releases cAMP which acts as a second messenger and initiate variety of cehm changes in target cell

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Protein kinases

answer

perform protein phosphorylations which can open ion channels inducing and regulating diff types of chem rxns that ultmately result in formation of millions of new molecules inside target cell

question

G proteins can also effect:

answer

Ca++ ions influx either from intracellular stock piles or by opening Ca++ channels G ptn activates phospholipase C (PLC) -> DAG & IP3= -> PKC (ptn kinase C) -> phosphorylation of ca ++ channels -> inc Ca++ calmodulin -> necessary stimulation by epinephrine or noradrenaline (or oxytocin)

question

Direct gene action

answer

steroid hormones; lipid-soluble; enter target cell to bind w/ intracellular receptors bind w/ intracellualr receptors, these hormones induce ptn synthesis, binding to DNA initiating transcription and translation of specific genes

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Endocrine activity triggered by:

answer

1. humoral stimuli: changes in composition or entracellular fluid 2. hormonal stimuli: arrival or removal of specific hormone 3. neural stimuli: arrival of neurotransmitter at neuro-glandular junctions

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Control of endocrine activity

answer

endocrine activity regulated by changing amount of hormone secreted and pattern of hormone release (pulses vs continuous) through neg feedback

question

Humoral stimuli

answer

humor means fluid; changes in composition of body fluid act as stimuli inducing endocrine gland to release hormone Ex: increase in blood sugar from optimum- relase of insulin; decrease in blood calcium level causes release of PTH

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Neural stimuli

answer

nerve stimulus directly causes release of hormones Ex: under stress, sympathetic nerve endings stimulate adrenal medulla to release epinephrine and norepinephrine

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Hormonal stimuli

answer

a hormone of one gland stimulates another endocrine gland Ex: thyroid stimulating hormone from anterior pituitary gland stimulates thyroid gland to release thyroid hormone

question

Main endocrine glands

answer

-pituitary gland (hypophysis cerebrii) -hypothalamus- neuroendocrine center -thyroid glands -parathyroid glands -adrenal glands: thymus gland, pineal gland, gonads

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Contain ells that secrete hormones

answer

hypothalamus, thymus, islets of langerhans in pancreas, ovaries, testis, kidneys, stomach, liver, small intestine

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Pituitary and hypothalamus

answer

"master gland"- hypothalamus: 9 diff hormones pituitary: secretes seven -play major role in reg of all aspects of growth, dev, metabolism, and homeostasis

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Pituitary gland

answer

suspended from hypothalamus by stalk called infundibulum, located in sella turcica of sphenoid bone

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Neurohypohysis

answer

posterior lobe; non secretory part, made of glial cells and nerve fibers -stores neuro-hormone produced by hypothalamus

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Adenohypophysis

answer

anterior lobe; made of endocrine cells that produce # of hormones

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Hormones by anterior pituitary lobe

answer

1. growth related hormones 2. tropic hormones or tropins 3. prohormone (POMC) from which a few active hormones are derived -all are amino acid-based hormones

question

Growth hormone/Somatotropin

answer

released when growth hormone releasing hormone (GHRH) from hypothalamus stimulates endocrine cells in anterior pituitary lobe hypothalamus->releases GHRH->stimulates anterior pituitary->releases GH->acts on growth plate->stimulates cartilage cells to divide and increase in number= longitudinal bone growth

question

growth hormone inhibiting hormone (GHIH)/somatostatin

answer

growth hormone production is stopped

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GH function

answer

promotes body growth by ptn synthesis; promotes fat utilization by body cells

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Somatomedins

answer

produced by muscles, bones, liver; GH reg aa metabolism and sulfur intake and use by cartilage cells

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Pituitary gigantism/ acromegaly

answer

oversecretion of GH

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Pituitary dwarfism

answer

hyposecretion of GH

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Prolactin

answer

stimulates female milk glands after child birth and in other vertebrates stimulates reproductive organs

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TSH/thyroid stimulating hormones or thyrotropins (tropic hormone)

answer

stimulates thyroid glands TRH(from hypothalamus)->stimulates AP->releases TSH->stimulates thyroid glands= releases thyroid hormones

question

ACTH/adrenocorticotropic hormone or corticotropin (tropic hormone)

answer

stimulates adrenal cortex CRH(from hypothalamus)->stimulates AP->releases ACTH->stimulates adrenal cortex-= releases corticosteroid hormones

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Gonadotropins

answer

stimulates primary sex organs (testis and ovaries)

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FSH-follicle stimulating hormone (gonadotropin)

answer

stimulates sex cell production by testis/ovary at puberty

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Luteinizing hormone (LH) (gonadotropin)

answer

intiates sex hormones production released by testis and ovary; testis produces testosterone and ovary produces estrogen and progesterone; LH help reg ovulation in females GnRH-> stimulates AP->releases FSH and LH-> stimulates ovary/testis=sperm and ovum prod. and release of testosterone/estrogen + progesterone at puberty

question

POMC

answer

large protein based molecules

question

Pro-hormone POMC (pro opiomelanocortin)

answer

may yield as many as 10 biologically active peptides involved in diverse cellular functions

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ACTH: adrenocorticotropic hormone

answer

binds to mem receptors activating G protein; cAMP that stimulates secretion of cortisol from adrenal cortex

question

MSHs: melanocyte-stimulating hormone

answer

different tissues (hypothalamus, placenta, epithelium); all cleavage sites may be used, giving rise to peptides with pain and energy homeostasis, melanocyte stimulation, immune modulation

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Melanocytes

answer

unicellular glands, located in stratum basal of epidermis, produce melanin (pigment) stim by UV rays that act on hypothalamus

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Endorphins

answer

body's natural pain killers; same effect as opiates during stress and exercise

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Lipotrophins

answer

bind to receptors on adipose mem causing lipid breakdown and release of FA into blood

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Hypothalamus

answer

part of brain, neurohypohysis; control pituitary gland; acts as nerve center for hormone fxns; produces ADH and oxytocin

question

ADH

answer

released when water content in body decreases; causes more water absorption at kidneys, results in reduced urine volume; may also cause increase blood pressure (vasopressin)

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Oxytocin

answer

effects smooth muscles, uterine contractions, ejaculation; "let down" reflex by which milk is ejected from milk glands; "cuddling hormone" plays role in pair bonding and affectionate behavior; sexual arousal

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T4- tetra-iodo thyronine/thyroxine

answer

has thyroglobulin and 4 atoms of iodine

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T3 or tri-iodothyronine

answer

has thyrogloblin and 3 atoms of iodine

question

Thyroid hormones

answer

called metabollic hormones; help reg cell metabolism by reg oxygen and nutrient use by most body cells

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Hypothyroidism

answer

in adults leads to myxedema- edema, lethargy, sluggishness, obesity; if caused by iodine deficiency- goiter; can lead to cretinism in children

question

Hyperthyroidism

answer

in adults leads to Grave's disease (autoimmune disorder)

question

parafollicular cells of thyroid glands (c-cells)

answer

produce second hormone called calcitonin -released when blood calcium level increases; inhibits osteoclasts and stimulates osteoblasts to promote bone formation; important in starvation and late stages of preg.

question

Parathyroid glands

answer

-2 pairs of small glands on posterior side of thyroid glands -produces PTH -released when blood calcium level decreases -stimulates osteoclasts and causes bone resorption -causes calcium absorption from kidneys and intestine -activates Vit D to enhance calcium absorption

question

Adrenal cortex

answer

made of endocrine cells that produce number of steroid hormones called corticosteroids

question

inner adrenal medulla

answer

consists of modified sympathetic neurons which together produce 2 important amino-acid based hormones called catecholamines

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Addison's disease

answer

hyposecretion of glucocorticoids and aldosterone (majority autoimmune disorders where antibodies cause adrenal cortex destruction/ block ACTH to receptors)

question

Mineralocorticoids

answer

help reg electrolytes (mineral salt) conc. in body fluids, esp Na+ and K+

question

Aldosterone

answer

most important mineralocorticoid; promotes sodium absorption from kidneys and intestine; sodium reg coupled w/ potassium ion reg; as sodium ions absorbed, potassium ions excreted from body also reg bicarbonate ion, hydrogen ions, and chloride ions

question

Glucocorticoids

answer

cortisol= most important glucocorticoid; helps reg blood glucose level on 24 hr cycle and induces hyperglycemia

question

stress hormone

answer

high blood glucose level; when body is under stress; increases blood pressure causing vasoconstriction; cortisol helps resist stress

question

Gonadocorticoids

answer

similar to male sex hormones produced by sex glands; supposed to help in dev. of sex organs before onset of puberty

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Adrenal medulla

answer

responds to short-term stress by releasing catecholamines epinephrine and norepinephrine

question

Epinephrine

answer

makes up 80% adrenal medulla secretion; increases heart rate and rate of blood flow; dilates air passage in lungs; helps increase level of activity of most organs

question

Norepinephrine

answer

causes vaso-constriction of peripheral arterioles; increases bp

question

Fight or flight system

answer

quickly mobilizes body resources against danger (brings glucose and O2 to organs); inhibits dig (reduces blood to kidney, release renin)

question

Eventual exhaustion

answer

eventual wasting of muscles, suppression of immune system, ulceration of gastrointestinal tract, failure of pancreatic beta cells-> disease

question

Exocrine, acinar cells

answer

in pancreas; produce dig enzymes poured into small intestine through pancreatic duct

question

Endocrine cells

answer

in pancreas; organized as small plated islands, in b/w lobes of acinar cells, called islets of langerhans consist of: alpha cells, beta cells, delta cells

question

alpha cells

answer

produce glucagon

question

beta cells

answer

produce insulin

question

delta cells

answer

produce somatostatin

question

Polyuria

answer

increased urine volume; kidneys use large volumes of water to remove unused glucose from blood; body also loses large quantities of sodium and potassium ions

question

Polydipsia

answer

water loss from kidneys leads to dehydration and intense thirst

question

Polyphagia

answer

acute hunger; as body cells can't use blood glucose in absence of insulin

question

Pineal gland

answer

contain neurons, neuroglial and pinealocytes which synthesize melatonin from molecules of neurotransmitte serotonin

question

fxn of pineal gland

answer

melatonin plays role in timing of human sexual maturation; protects against damage by free radicals; setting of circadian rhythms

question

Thymus gland

answer

large lymphoid organ w/ some endocrine cells; produce thymosins; hormones that reg maturation of T-lymphocytes

question

Granulocytes

answer

neutrophil- make up 70%, eosinophils, basophils

question

Agranulocytes

answer

monocytes, lymphocytes

question

B cells

answer

responsible for antibody mediated immunity= humoral immunity

question

T cells

answer

responsible for cell mediated immunity

question

Gonads

answer

produce sex hormones (steroid hormones)

question

Estrogen

answer

female hormone that reg maturation of reproductive organs and secondary sexual traits of females at puberty

question

Progesterone

answer

pregnancy hormone that reg all changes in female body during preg

question

Testosterone

answer

reg maturation of male sex organs and male secondary sexual traits

A;P- CH 18 Endocrine System – Flashcards

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