Ls 2 Lecture 8

Front 1

hormones

Back 1

long range chemical messengers secreted into bloodstream by endocrine (ductless) glands in response to an appropriate signal, carried in the blood to other sites in the body where they exert their effects on target cells

Front 2

Paracine signals

Back 2

(local mediators)

released by cells into the extracellular medium in their neighborhood and act locally

eg. histamine (swelling, inflammation makes capillaries more leaky, get wbc's in to fight infection)

Front 3

Neurotransmitters

Back 3

diffuse across synapses

Front 4

Hormones act on ____________ which must have appropriate ________ to bind to hormone and bring about physiological response

Back 4

target cells...receptors

Front 5

endocrine generally regulates activities that require _____, rather than speed

Back 5

duration

Front 6

Types of hormones (3)

Back 6

peptides
amines
steroids

Front 7

peptides

Back 7

most hormones

secreted by hypothalamus, anterior and posterior pituitary, pancreas, parathyriod

amino acids linked together

Front 8

amines

Back 8

derived from amino acid, tyrosine

secreted by the thyroid gland, adrenal medulla

adrenomedullary hormones are called catecholamines

Front 9

steroids

Back 9

neutral lipids derived from cholesterol;

secreted by the adrenal cortex, ovaries, testes

steroid and thyroid hormones are lipid soluble (lipophillic)

Front 10

Water soluble vs. lipid soluble hormones

Back 10

water soluble transported dissolved in plasma
eg. peptides and catecholamines. bind to specific plasma membrane receptors

lipophillic transported largely bound to plasma proteins

eg. steroids and thyroid hormones- bind to intracellular receptors

Front 11

True of False: a hormone acting on a target cell receptor produces a characteristic response in the target cell, which is different for different hormones, and differs between different target cells responding to the same hormone

Back 11

true

adrenal medullary catecholamine epinephrine
-contraction of vascular smooth muscle (constricts radial smooth muscle)
-relaxation of respiratory airway smooth muscle (dilates the radial smooth muscle)
-breakdown of liver glycogen

Front 12

how to hormones affect their target cells?

Back 12

by altering activity of proteins within the cell

hydrophilic hormones bind to cell surface receptors, produce a second messenger molecule within the target cell (hormone is the 1st messenger), ex. cyclic amp is 2nd

some hydrophilic hormones following binding to cell surface receptors, alter cell permeability by opening or closing particular ion channels

lipophilic hormones, through binding to intracellular receptors, activate specific genes (through transcriptional regulation within the nucleus) leading to the formation of new intracellular proteins which produce a characteristic physiological effect

Front 13

Types of cell surface receptors

Back 13

ligand-gated ion channels
-eg. acetylcholine receptor
-important in nervous system

G protein linked receptors (give you sight, smell)
-guanyl nucleotide binding proteins (G proteins) act as molecular switches, active when GTP is bound, inactive with GDP due to action of intrinsic GTPase

Enzyme Linked Receptors
-eg. insulin receptors

Front 14

G unit protein

Back 14

3 subunits, two alpha, one beta

alpha binds to GTP or GDP and has intrinsic enzyme activity

receptors=molecule switches
GTP bound="on"
GDP bond= "off"

build in timer is GTpase GTP --> GDP

G proteins relay info -->alpha subunits shuttle across to effector
-->GTPase inactivates G protein

when g protein is bound to receptor, GDP released and GTP binds "on". alpha unit with GTP separates from B and alpha and bind with enzyme to perform an action

see figures in lecture 8

Front 15

Cyclic AMP- second messenger

Back 15

formed from ATP by adenylyl cyclase, and enzyme that is activated by a G protein

effects involve binding to and activating cAMP dependent protein kinase (PKA) which phosphorylates specific proteins on serine or thronine residues, leading to some physiological change

Front 16

Glycogenolytic Cascade

Back 16

liver cells respond to epinephrine by activating G proteins, which in turn activate cAMP sythesis

cAMP activates a kinase cascade whcih releases glucose from glycogen (glycogenolytic cascade)

glycogen synthesis is inhibited

kinase cascade amplifies the epinephrine signal

release of glucose is a key part of "flight or fight"

Front 17

Inositol Lipid Signaling Pathyway

Back 17

after receptor activation of a G protein, phosphatidylinositol 4,5-biphoasphate is cleaved by phospholipase C and forms 2 intracellular messengers:

diacylyglycerol- activates protein kinase C

inosital triphosphate (IP3)- releases calcium from the endoplasmic reticulum

Front 18

Calcium as intracellular messenger

Back 18

Ca2+ concentration in cytoplasm is usually only .1 uM.

kept low via active transport, both out of cell and into ER

IP3 causes CA channels to open *other things do as well

once triggered to open., Ca concentration rapidly rises up to 100 resting concentration

calcium ions bind to a calcium binding protein called CALMODULIN which can activate Ca 2+ dependent protein kinases

Front 19

nitric oxide signal transduction

Back 19

nitric oxide (NO) intracellular messenger that links the effects of acetylcholine to the relaxation of smooth muscles of the blood vessels

ach acting on endothelial cells, stimulates the IP3 pathway to produce influx of Ca, which stimulates NO synthase to produce NO from arginine

NO diffuses o the underlying smooth muscle, where is stimulates guanylyl cyclase which produces another intracellular messenger, cGMP

this messenger stimulates a kinase cascade leading to muscle relaxation

*viagra keeps cyclic GMP for longer, muscle does not relax