Ch 6: Membrane Communication

Physiological Signals

Electrical

Chemical

changes in a cell membrane's "potential".

molecules secreted by cells into the extracellular fluid

Target cells- cells that respond to both types

most chemical signals

Cell-Cell Communication

Long-Distance Cell Communication

Local Cell Communication

Gap Junction

cytoplasmic transfer of electrical and chemical signals between adjacent cells linked by membrane proteins

Contact-dependent signals

surface molecules on one cell membrane binding to surface molecules of another cell membrane

Direct Communication

Paracrine Signal

chemical secreted by a cell that acts on nearby cells

combinations of electrical via nerve cells and chemical via blood to target systems; nervous and endocrine respectively

Ligand

Ligand-ion or molecule stuck to a metal atom

Autocrine Signal

local chemical signal that acts on the secreted cell

Neurocrine Molecules- molecules secreted by a nerve cell

Neurotransmitter

Neuromodulator

Neurohormone-

chemical signal released by a neuron to affect its target cell

chemicals alter the response of a neuron; slower than neurotransmitter

hormone that is made and secreted by a neuron

bridge the gap between NS and ES, medium between the two

Cytokine

peptides that alter and make an immune response

associated with immune response (inflammation)

Cell Development and Differentiation

autocrine and paracrine signal

Stress and inflammation

act on relatively distant targets and transported via circulation like hormones

Made on demand; long or local distance signals

Ex) interferons, interleukins, colony-stimulating factors, growth factors, tumor necrosis factors, chemokines

Signal Pathways (Refer to drawing and steps)

Messengers are classified by chemical Properties

either be

Lipophilic

lipophobic

bind to cystolic or nuclear receptors

bind to cell membrane receptor since they can't enter the cell via simple diffustion

activates intracellular receptors to turn on a gene and make the nucleus craft mRNA

bind to receptor proteins;fast response time

slow response

suppress/repress gene activity

Types

Steroids

Eicosanoids

hormone

paracrine

Types

Amino Acids

Amines

Peptides/Proteins

Paracrine, neurotransmitter, hormones

functions as a neurotransmitter

Signal Transduction- sending info from one side of a membrane to another side using membrane proteins.

Transducer- device that converts a signal from one form into a different form

Change the function of a target cell

Messengers interact with the target cell by binding to receptors on or in the target cell (first messenger by bringing info to target cell).

receptors change enzyme activity or alter channel function/cell function.

Properties of Receptors

ligand-receptor binding activates receptor

Receptor activates 1+ intracellular signal molecules

last signal molecule in the pathway modifies existing proteins or starts making new proteins

specificity (Target Response)

Number of Interactions (Greater Responses) can be affected by

messenger concentration

Number of receptors present

Receptor affinity

Messenger Receptor Responses

Intracellular Mediated Responses

Membrane-Bound Receptor-Mediated Responses

Receptors are either cytosol (cytoplasm) or nuclear (nucleus)

use of Lipophilic molecules and thyroid hormones

Responses includes gene inhibition or activation

lipophobic messengers

receptors are from the cell membrane

Types

Receptor-Channels

Receptor-Enzyme

G-protein coupled receptors

Integrin Receptors

Ion channels (simplest

Ligand binding opens/closes the channel and alters ion flow across the membrane (Ion movement)

Membrane Proteins that binds ligands on the extracellular side and activates enzymes on the intracellular side

Inactive until a messenger molecule is attached

receptor enzymes results in intracellular enzymes to be activated

large, complex family of membrane-spanning proteins

G-protein- cytoplasmic tail of the receptor protein

messenger molecule acts on the receptor and activates the G proteins which acts on another protein found in the cell membrane

Most signal transduction mechanisms

bonding ligands include hormones, growth factors, olfactory molecules, visual pigments, and neurotransmitters.

enzyme include adenyl cyclase and phospholipase C

role in blood clotting, wound repair, cell adhesion, immune response recognition, and cell movement during development

aka enzyme receptors with additional properties

ligand

Second Messenger System

intracellular molecule produced by or entering into the target cell in response to an extracellular messenger

triggered by the first messenger (ligand) activating the G-protein-coupled receptor

Common 2nd messenger are calcium ions or Cyclic Amp

Signal Amplification

process by which a signal molecule can generate multiple intracellular effector molecules

exponentially increases number of molecules made: 1 -> multiple

Signal Molecules

Nitric Oxide

Hydrogen Sulfide

Calcium

Roles

  1. alters enzyme/transporter activity or the gating of ion channels ex) binding to the protein calmodulin
  1. Binding to regulatory proteins and alters movement of contractile or cytoskeletal proteins ex) calcium binding to troponin to make muscle contractions in a skeletal muscle cell
  1. Binding to regulatory proteins to trigger exocytosis ex) release of insulin from pancreatic beta cells in response to calcium
  1. Direct binding to ion channels to alter gating states example) Calcium and potassium channel in nerve cells

diffuses into target cells where it binds to intracelular proteins

made by endothelial cells that line blood vessels

causes muscles to relax and dilate blood vessels

neurotransmitter and neuromodulator in the brain

acts in the cardiovascular system to relax blood vessels

garlic has H2S

explains why eating foods with garlic has + heart effects