Physiology Chapter 6 - Communication and Homeostasis

What are electrical signals regarding cell to cell communication?

Changes in a cell's membrane potential

What are chemical signals regarding cell to cell communication?

Molecules secreted by cells into the extracellular fluid

What are the different types of local communication?

Gap junctions

Contact dependent signals

Long distance communication

What are gap junctions?

Allow material to move by diffusion

Allow direct cytoplasmic transfer of electrical and chemical signals between adjacent cells

What are contact dependent signals?

Occur when surface molecules on one cell membrane bind to surface molecules on another cell's membrane

What are long distance communications regarding cell to cell local communications?

Uses a combination of chemical and electrical signals carried by nerve cells and chemical signals transported in the blood

What is a paracrine signal?

A chemical that acts on cells in the immediate vicinity of the cell that secreted the signal

What is an autocrine signal?

A chemical signal that acts on the cell that secreted it

What is the general process of a signal pathway?

Signal molecule, binds to

Membrane receptor protein, activates

Intracellular signal molecules, alter

Target proteins, create

Response

What does it indicate if receptors are present on the outer cell membrane?

The signal molecule is lipophobic or hydrophilic because it cannot diffuse through the membrane therefore resulting in the receptor being present on the outside surface of the cell

What is the ultimate effect caused by a lipopilic pathway?

The receptors are on the inside of the cells in the cytosol or the nucleus.

The effect is to alter the activity of some specific gene in the nucleus which therefore changes transcription and alters the rate of protein synthesis

What is a signal transduction?

The process by which an extracellular signal molecule activates a membrane receptor that in turn alters intracellular molecules to create a response

What is the general flow of a signal transduction pathway?

External signal

Receptor

Transducer

Amplifier

Response (after phosphorylation)

What is a transducer?

A device that converts a signal from one form into a different form

What is true about the relationship between first and second messengers in a signal transduction pathway?

For every first messenger there are several second messengers creating multiple targets which increases the amplification

Why is it important for one ligand to amplify into so many intracellular molecules?

Generates a response without using up too many

What are the two most common second messengers?

cAMP and calcium

Where does amplification take place first?

G protein being broken down because there are multiple G proteins on each receptor

What is down regulation?

Decrease in receptor number

example: this is what causes the withdrawal symptoms

What is up regulation?

Increase in receptor number