Week 2 - Cell Communication - Physiology

what are 2 types of physiological signals

• electrical signals

• chemical signals

what are electrical signals

• changes in the membrane potential of a cell

what are chemical signals

• secreted by cells into extracellular fluid ECF

• responsible for most communication in the body

• ligands

• target cells respond to signals

what type of signal is responsible for most communication within the body

• chemical signals

what are proteins of chemical signals subject to when binding

• specificity

• affinity

• competition

• saturation

what is local communication (short distance)

1. gap junctions create cytoplasmic bridges between adjacent cells

2. contact dependent signals require cell-to-cell contacts

   1. cell adhesion molecules CAMS

3. chemicals diffuse through ECF to act on nearby cells

what does long distance communication use

• chemical and electrical signals

what does local communication use

• paracrine and autocrine signals

what are cytokines

• peptides

• synthesized and secreted by all nucleated cells in response to stimuli

what are the families of cytokines

• interferons

• interleukins

• colony-stimulating factors

• growth factors

• tumor necrosis factors

• chemokines

how do cytokines functions in development and differentiation

• as autocrine or paracrine signals

how do cytokines function in stress and inflammation

• acts on relatively distant targets

how do cytokines differ from classical hormones

• Any nucleated cell can produce (cytokines) vs. just specialized epithelial cells produce hormones

• Made on demand vs made in advanced and stored

• Intracellular pathways differ

when would a cell respond to a particular chemical signal

• only if the target has a receptor

what is the signal pathway

1. The chemical signal (first messenger) is a ligand that binds to receptor protein

2. Ligand-receptor binding activates the receptor

3. The receptor activates one or more intracellular signal molecules

4. The last signal molecule modifies existing proteins or initiates the synthesis of new proteins

what are 4 types of membrane receptors

• receptor-channel

• G-protein coupled receptor

• catalytic receptors

  • receptor enzyme

  • integrin receptor

how do membrane proteins facilitate signal transduction

• transducer converts a signal from one form to another

• extracellular signal is the first messenger

  • activates proteins kinase and amplifier enzymes

• intracellular signal is the second messenger

  • alter gating of ion channels

  • increase intracellular calcium

  • change enzyme activity

• cascades of activation steps

• signal amplification of signals

  • amplifier enzyme

what is the first messenger in signal transduction

• extracellular signal

what does the extracellular messenger do

• activates proteins kinase and amplifier enzymes

what is the second messenger in signal transduction

• intracellular signal

what does the intracellular messenger do

• alter gating of ion channels

• increase intracellular calcium

• change enzyme activity