BIOL 2160 Chapter 5

channels formed between 2 cells, we do not need receptors because these cells are so close together, direct electrical and metabolic coupling, common in smooth and cardia muscle

gap junctions

receptors are very _____ for certain chemical messengers

specific

functional classification of chemical messengers:

Paracrines

Autocrines

Neurotransmitters

Hormones

Neurohormones

Cytokines

released by cell, moves to target cell by diffusion, act on neighboring cells, 3 examples: histamine, testosterone, and prostaglandins

paracrines

released with tissue damage and causes dilation of local blood vessels, clotting factors

histamine

moves from the Leydig cells into the seminiferous tubules

testosterone

act locally, very potent in small amounts, regulate cellular responses to hormones, activate or inhibit adenylate cyclase (controls cAMP production and alters cell's response to hormones), wide variety of functions, first found in semen (so they named it after the prostate - but the prostate doesn't actually make it)

prostaglandins

self, acts on cells that release it

autocrine

messengers of the nervous system, released from neuron by exocytosis, large molecules, diffuses to very close target cell across a synapse

neurotransmitter

messenger of the endocrine system, released from endocrine gland into blood, transported in blood to target cell

hormones

cells in body with receptors specific to the hormone

target cell

hormones released from the axons of neurons in the hypothalamus (in your brain), ADH & Oxytocin in posterior pituitary, inhibiting and releasing hormones into the portal system going to the anterior pituitary

Neurohormones

peptides or proteins, can be transported in blood, released by most cell types, involved in cell development, differentiation and IMMUNE RESPONSE, often act on a wide range of target

cytokines

chemical _______determine mechanism of transport and mechanism of action on target cell

class

can cross plasma membrane (2 terms that can be used interchangeably), phospholipids, these have to go through the blood stream with a transporter - any steroids have to be transported

Lipophillic/Hydrophobic

can dissolve in plasma or ISF, cant go through the cell membrane so they can dissolve in the blood stream - don't need a carrier (2 terms that can be used interchangeably)

Lipophobic/Hydrophillic

chemical classes of messengers

amino acids, amines, peptides, steroids, and eicosanoids

all function as neurotransmitters (glutamate, aspartate, glycine, GABA (gamma-amino butyric acid)

Lypophobic - have to have a receptor on the surface of the cell membrane

Amino Acid Messengers

derived from amino acids and contain amine group (know 6 of them)

Amine Messengers

type of amine messenger derived from tyrosine (dopamine, norepinephrine, and epinephrine)

Catecholamines

type of amine messenger derived from tryptophan (histamine, and thyroid hormones), lipophobic except for thyroid hormones

Serotonin (5 DTH)

most abundant class of chemical messengers, chains of amino acids including peptides and proteins, many are hormones, lipophobic (receptors on cell membrane)

Peptide/Protein Messengers

derived from cholesterol, all hormones, lipophilic

Steroid Messengers

has receptor mediated endocytosis because it is so big and there are many different types of it, come can pass right through, and some need a receptor

Cholesterol

derived from a plasma membrane phospholipid, lipophilic

Eicosanoids

synthesis depends on chemical _____

class

diffusion, released upon synthesis, regulate release by regulating rate of synthesis

Lipophillic Messengers

exocytosis, stored in vesicles prior to release, regulate rate of exocytosis

Lipophobic Messengers

how many amino acids are in your body and used by proteins?

20

how many amino acids are essential? (meaning we have to get them from our diet - we cannot make them)

9

how many amino acids can be synthesized in the body (made in body)

11

how many of the 11 amino acids synthesized in our body are neurotransmitters?

3

1 gamma amino acid =

neurotransmitter

after ______, neurotransmitters are transported into secretory vesicles and stored in vesicle until a stimulus comes and releases it

synthesis

cytosol by sequence of enzyme catalyzed reactions, stored in vesicles until stimulus releases it, synthesized in cytosol by sequence of enzyme catalyzed reactions

Amine Synthesis

pre-hormone, maintains our pregnancy

progesterone

once _______ is converted to estrogen, that is where it stays forever - it cannot be converted back

testosterone

when men take too much testosterone, the brain turns it into ______

estrogen

all are membrane proteins, often more than one type of receptor for one messenger, one cell may have receptors for different messengers, or even different types of receptors for one messenger

receptor properties

______ of receptor to messenger (one receptor might mean dilation while another might mean constriction)

specificity

magnitude of response depends on ____ of receptors with messenger bound (concentration of messenger, number of messengers, and affinity of receptor for messenger)

number

can occur when excess messenger is present, target cell decreases number of receptors for messenger (ex: tolerance to a drug)

down regulation

no longer works in your body (ex: if you're a drug head you up your dosage to still be able to feel an effect)

tolerance

can occur when too little messenger is present, target cell increases number of receptors for messenger, develop hypersensitivity

up regulation

such as allergic reactions - at first it takes a lot to set off a reaction, but THEN just the tiniest bit of it causes you to have a severe reaction

hypersensitivity

binds to a receptor mimicking normal response

agonist

binds to a receptor producing no response, competes with normal messenger

antagonist

endogenous opiate, binds to mu opiate (mind altering drug) receptors producing analgesia

Beta-endorphin

an example of an analgesia

aspirin

mu receptor agonist, administration of naloxone blocks morphine or beta-endorphin produced analgesia

morphine

mu receptor antagonist, administration of naloxone blocks morphine or beta-endorphine produced analgesia, people are given this drug when they are hooked on morphine to help them get off of it eventually

Naloxone

process by which messenger binding to receptor produces response in target cell, mechanism differs based on whether messenger is lipophillic or lipophobic

signal transduction

receptor inside cell, bind to receptor in cytoplasm or nucleus, alters transcription

lipophillic messenger

receptor on plasma membrane

lipophobic messenger

opens/closes ion channels in response to messenger (ligand) binding

channel linked

messenger always = ______ no matter what kind of messenger

ligand

most are tyrosine kinase

enzyme linked

most complex

G-protein linked

gated ion channels can _____ and _____

open and close

when a gated ion channel is open

ion can move through

when a gated ion channel is closed

ion cannot move through

ion movement has 2 effects:

1. Change electrical properties of the cell (cell charge on the membrane = -70mV)

2. Interact with proteins in cytosol to induce: contraction, secretion or altered transport

messenger that binds to receptor/channel, open channels correspond to increased permeability

ligand

receptor and channel are same protein

fast channels

receptor coupled to channel by G protein

slow channels

cytoplasm doesn't like _____

calcium

calcium has a _____ charge

2+

changes electrical properties of cell, induces muscle contraction, induces secretion by exocytosis, binds to CALMODULIN

role of calcium in signal transduction

Ca-calmodulin complex ______ protein kinase, protein is phosphorylated, response in cell

activates

calcium ______ by binding with proteins in cytosol - doesn't recognize them as calcium anymore

sequestration

Binding of _______ messenger changes activity of a G protein that functions as a coupler

extracellular

G proteins =

regulatory proteins

G proteins linke ECF messenger to _____ enzyme or ion channel --> so one messenger can create a thousand different things in the cell, the receptor is what determines its path

amplifier enzyme (makes it bigger)

binding of first messenger to receptor leads to production of ____________ in the cytosol

second messenger

an intracellular messenger produced by binding of an extracellular messenger to a receptor

second messenger

second messenger system involves ____ proteins

G

stimulates amplifier enzyme

Gs

inhibits amplifier enzyme

Gi

what is the purpose of the second messenger system?

amplification

small amounts of ligand can cause a huge response in target, each step recruits

Signal amplification cascade

kinase helps in ____

phosphorylation

1 messenger leads to several G proteins amplified -->

adenylate cyclase

each adenylate cyclase generates hundreds of ____

cAMP

each cAMP activates a protein kinase A which phosphorylates hundreds of _______

proteins

enzyme that degrades cAMP

Phosphodiesterase

______ inhibits cAMP phosphodiesterase leading to prolonged response

caffeine

nervous system, endocrine systems (signal transmission in neurons and signal transmission in endocrine system) endocrine gland releases hormone into blood, travels to distant target cells

long distance communications