Chapter 4: Neuronal Physiology - Communication of Cells

Extracellular Chemical Messengers.
Responsible for communication within cell.
Chemical signals are ligands
Target cells respond to signals

Gap Junctions create a cytoplasmic bridge
Contact-dependent signals require cell-to-cell contacts
ECM diffuses through the extracellular fluid to act on nearby cells
Local communication uses autocrine and paracrine signals
Short term

Autocrine signals act on the same cell that secreted them.
Paracrine signals are secreted by one cell and diffuse to adjacent cells.

Uses chemical and electrical signals
Hormones, Neurotransmitters, Neurohormones
Endocrine signaling, long-distance signaling
ECMS is used in this kind of communication

ECMs bring about a response in the target cell by signal transduction
ECMs can often not cross the hydrophobic layer of plasma membrane
Binds to specific membrane receptor
Response can be opening or closing of ion channels

- Receptor-channel, ligand binding opens or closes the channel
- G protein-coupled receptor, ligand binding to a G protein-coupled receptor opens an ion channel or alters enzyme activity.
- Receptor-enzyme, Ligand binding to a receptor enzyme activates an intracellular enzyme
- Integrin receptor, Ligand binding to integrin receptors alters enzymes or the cytoskeleton.

Receptor enzymes and integrin receptor

Extracellular signal is the 1st messenger, activates protein kinases, and amplifies enzymes
Intracellular signals are second messengers, altering the gating of ion channels and increasing intracellular calcium change enzyme activity.