Bio 1220- Cell to cell communication

Electical signals

Change in cell’s membrane potential

Chemical signals

Molecules secreted into extracellular fluid

Gap junctions

Good for transfer of ions and small molecules

Cell-to-cell contact

Multiple cell in contact allowing for signalling

Paracrine signaling

Acts on cells in proximity of the cell secreting signal

Autocrine signaling

Acts on the cell that secreted it

Long distance signalling ways

Hormones dumped into blood stream, electrical current in nervous system

Why do only some cells respond to chemical signals

Target cells have specific receptor protein

Signaling pathways are

Very complex

One ligand can

Have multiple receptors

Specificity and competition meaning in signaling pathways

Different ligands with similar structures may be able to bind to the same receptor

Agonist

Occupy binding site and activates receptor

Antagonist

Occupy binding site but does activate them

Homeostatic reflex

Reflex pathway following the same seven steps to maintain homeostasis

Stimulus

Disturbance or change

Sensor

Senses change in environment

Input signal

Signal brought into integrating center

Intergrating center

Interpret and initiate a response

Output signal

Signal leaving integration center

Target

Cells or tissue that carry out the response

Response

Cellular response takes place in target cell