lecture exam 1 (a&p2)

two systems that maintain homeostasis

nervous & endocrine system

endocrine system

regulates long term processes & uses chemical messengers to relay info & instructions between cells

long term processes

growth, development, & reproduction

intercellular communications

direct, paracrine, autocrine, endocrine, and synaptic communication

direct communication

exchange of ions & molecules between adjacent cells across gap junctions. only happens between two cells of the same type. coordinates cilia in epithelial & cardiac cells, & eletrical synapses

paracrine communication

chemical signals transfer info from cell to cell within single tissue, the most common form of intercellular communication, chemicals are known as local hormones (doesn’t go in blood, only tissue). examples are growth factors, tissue factors, and clotting

autocrine communication

messages affect the same cells that secrete them

endocrine communication

endocrine cells release chemicals (hormones) into bloodstream, alters metabloic activites of many tissue & organs, target cells, & hormones

target cells

specific cells that possess receptors needed to bind and “read” hormonal messages

hormones

stimulate synthesis of enzymes or structural proteins, increase or decreases rate of synthesis of the cell, turns existing enzyme or membrane channel “on” or “off”, can alter the activity of multiple tissues, function in coordinating cell, tissue and organ activites for long periods of time. continual regulation of water balance & regulation of growth

synaptic communication

neurons release nerotranssmitters at a synapse, leads to action potentials (nerve impulse) that are propagates along axons, & allows for high speed “messages” to reach specific destinations

comparison of endocrine & nervous communication

rely on release of chemicals that bind to specific receptors on target cells, share many chemical messengers (norepinephrine & epinephrine), regulated mainly by negative feedback, function to preserve homeostasis by coordinating & regulating activities

class of hormones

amino acid derivatives, peptide hormones, & lipid derivatives

amino acid derivatives

small molecules structurally related to the amino acids, tyrosine, & tryptophan, are derivatives of tyrosine, & derivatives of tryptophan

derivatives of tyrosine

thyroid hormones & catecholamines

catecholamines

epinephrine, norepinephrine, & dopamine

derivatives of tryptophan

serotonin & melatonin

peptide hormones

are chains of amino acids, most are synthesized as prohormones, & has two divisions

prohormones

hormones produced, not activated

two divisions

glycoproteins & short polypeptides/ small proteins

glycoproteins

proteins (>200 amino acids) with carbohydrates side chains

short chain polypeptides

less than 10 amino acids. antidiuretic hormone (ADH) and oxytocin (OXT) are each 9 amino acids long

small proteins

insulin (51 amino acids), growth hormone (GH) (191 amino acids), prolactin (PRL) (198 amino acids)

lipid derivatives

contains eicosanoids & steroid hormones

eicosanoids

derivative of arachidonic acid (20 carbon fatty acid)

paracrines know how to

coordinate cellular activities and affect enzymatic processes

paracrines have various roles in

inflamation, fever, regulation of blood pressure, blood clotting, immune system modulation, control of reproductive processes and tissue growth, and regulation of the sleep/wake cycle

types of eicosanoids

leukotrienes, thromboxanes, & prostaglandins

steroid hormones

derived from cholesterol & bound to specific transport protein in the plasma that remains in the circulation longer than peptide proteins

steroid hormones includes

androgens from testes in males, estrogens & progesterone from ovaries in females, corticosteroids from adrenal cortex, & calcitrol from the kidneys

transport & inactivation of hormones

hormones may circulate freely or travel bound to special carrier proteins. includes free hormones & longer lasting hormones

free hormones

remain functional for less than 1 hour and are inactivated when they: diffuse out of bloodstream and bind to receptors on target cells, are absorbed and broken down by the liver or kidneys, & are broken down by enzymes in plasma or interstitial (in between) fluids

longer lasting hormones

thyroid & steroid hormones. remain functional much longer, more than 99% become attached to special transport proteins in the blood, equilibrium state exist between free & bound forms, & bloodstream contains substantial reserve of bound hormones

mechanisms of homrone action

binding of a hormone at the target cell, hormone receptor, down regulation, & up regulation

binding of a hormone at the target cell may

alter genetic activity, alter rate of protein synthesis, & change membraine permeability

hormome receptor

is a protein molecule to which a particular molecule binds strongly, different tissues have different combinations of receptors, and presence or absence of specific receptor determines hormonal sensitivity of a cell

down regulation

hormone triggers decreases in the number of hormone receptors

up regulation

hormone triggers an increase in the number of hormone receptors

hormones & plasma membrane receptors

catecholamines and peptide, steroid & thyroid hormones, hormone & extracellular receptors

catecholamines & peptide hormones

are not lipid soluble, unable to penetrate plasma membrane, bind to receptor proteins at outer surface of plasma membrane (extracellular receptors)

steroid & thyroid hormones

a lipid soluble & diffuses across plasma membrane to reach receptor proteins on inner surface of plasma membrane (intercellular receptors)

hormone & extracellular receptors

first & second messenger, amplification, g protein, g proteins & cAMP, g proteins & calcium ions

first messenger

hormone that binds to a extracellular receptor & promotes release of second messenger in the cell

second messenger

intermediary molecule that appears due to hormone-receptors interaction, may act as an enzyme activator, inhibitor, or cofactor; results in change in rates of metabolic reactions. examples: cAMP, cGMP, & Ca2+

amplification

when a small number of homone molecules binds to extracellular receptors, thousands of second messengers may appear. magnifies effect of hormone on target cell

g protein

protein binds GTP (hence the name G protein), linking the first & second messenger

steps for increasing cAMP levels, accelerates metabolic activity of cell

1) activated g protein activates an enzyme, adenylate cyclase. 2) adenylate cyclase converts ATP to cyclic AMP (cAMP). 3) cAMP functions as a second messenger (can open ion channels & activate enzymes). 4) generally, cAMP activates kinases that phosphorylate proteins

increase in cAMP level is usually

short lived

phosphodiesterase (PDE) converts cAMP to

AMP. (which is going to decrease metabolic rate)

activated G proteins trigger

1) g protein activates phospholipase C (PLC). 2) triggers receptor cascade beginning w/ production of diacylglycerol (DAG) and inositol triphosphate (IP3) from phospholipids. 3) IP3 diffuses into cytoplasm & triggers release of Ca2+ from intracellular reserves (er or ser). 4) calcium ion channels open due to activation of protein kinase C (PKC), and Ca2+ enter cells. 5) Ca2+ binds to calmodulin, activating enzymes

intercellular receptors

are targeted by thyroid hormones & steroid hormones

steroid hormones

bind to receptors in the cytoplasm or nucleus (can alter rate of DNA transcription)

thyroid hormones

bind to receptors within nucleus and on mitochondria

control of hormone secretion

mainly controlled by negative feedback

hormone secretion can be triggered by

Humoral, Hormonal, & Neural Stimuli

humoral stimuli

changes in the composition of the ECF, controls hormone secretion by heart, parathyroid gland, & digestive tract)

hormonal stimuli

arrival or removal of a specific hormone

neural stimuli

arrival of neurotransmitter at the neuroglandular synapse

the pineal gland

produces melatonin & contains melatonin hormone

melatonin hormone’s stimulus for release

nightime

melatonin hormone’s target

nervous system & reproductive organs

melatonin hormone’s action

day-night patterns (sleep), may play a role in the timing of sexual maturation, & antioxidant

the pituitary gland (hypophysis)

lies within sella turcica, hangs inferior to hypothalamus (connected by infundibulum [pituitary stalk], & releases nine important peptide hormones (binds to extracellular receptors & uses cAMP as second messenger)

the hypothalamus

regulates functions of the pituitary gland, synthesizes ADH & OXT & transports them to posterior pituitary gland for release & secretes regulatory homrones that control secretory activity of anterior pituitary gland

hormones of the anterior lobe

thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), gonadotropins, prolactin (PRL), growth hormone (GH), & melanocyte stimulating hormone (MSH)

thyroid stimulating hormone (TSH)’s stimulus for release

cold, pregnancy, or low T4

thyroid stimulating hormone (TSH)’s target

thyroid gland

thyroid stimulating hormone (TSH)’s action

stimulate production of thyroid hormones (T3 & T4 [thyroxine], and stimulates growth and development of thyroid gland

adrenocorticotropic hormone (ACTH)’s stimulus for release

environmental stress

adrenocorticotropic hormone (ACTH)’s target

adrenal gland (specifcally the adrenal cortex

adrenocorticotropic hormone (ACTH)’s action

stimulates production of corticosteroids (especially glucocorticoids)

glucocorticoids are

stress hormones

gonadotropins have two hormones called

Follicle Stimulating Hormone (FSH) & Luteinizing Hormone (LH)

follicle stimulating hormone (FSH)’s stimulus for release

the hypothalamus

follicle stimulating hormone (FSH)’s target (female)

ovaries

follicle stimulating hormone (FSH)’s target (male)

testes

follicle stimulating hormone (FSH)’s action (female)

stimulates development of ovarian follicles & oocytes & stimulates secretion of estrogen

follicle stimulating hormone (FSH)’s action (male)

stimulates production of sperm

luteinizing hormone (LH)’s stimulus for release

the hypothalamus

luteinizing hormone (LH)’s target (female)

ovaries

luteinizing hormone (LH)’s target (male)

testes

luteinizing hormone (LH)’s action (female)

induces ovulation

luteinizing hormone (LH)’s action (male)

stimulates secretion of testosterone

prolactin (PRL)’s stimulus for release

the hypothalamus

prolactin (PRL)’s target

mammary glands

prolactin (PRL)’s action

stimulates production of milk by mammary glands

growth hormone (GH)’s stimulus for release

the hypothalamus

growth hormone (GH)’s target

mainly bones & skeletal muscles

growth hormone (GH)’s action

liver cells to release somatomedins that stimulate tissue growth, breakdown of triglycerides in adipocytes & breakdown of glycogen to release ATP (releases glycogen)

Melanocyte Stimulating Hormone (MSH)’s stimulus for release

the hypothalamus

Melanocyte Stimulating Hormone (MSH)’s target

melanocytes in epidermis

Melanocyte Stimulating Hormone (MSH)’s action

increased melanin secretion in the epidermal cells & virtually nonfunctional in adults except in pregnant women

hormones of the posterior lobe

Antidiuretic hormone (ADH) & Oxytocin (OXT)

Antidiuretic hormone (ADH)’s stimulus for release

low blood pressure, increased sodium, & pain (retains water)

Antidiuretic hormone (ADH)’s target

kidney & blood vessels

Antidiuretic hormone (ADH)’s action

reabsorption of water, elevation of blood volume & blood pressure, & constriction of blood vessels

Oxytocin (OXT)’s stimulus for release

stretching of cervix and baby suckling on breast

Oxytocin (OXT)’s target (female)

uterus & mammary glands

Oxytocin (OXT)’s target (male)

ductus deferens & prostate gland

Oxytocin (OXT)’s action (female)

smooth muscle contraction of the uterus during labor, ejection of breastmilk & during intercourse may stimulate smooth muscle contractions of uterus and vagina to promote movement of sperm towards fallopian tubes