4.1 Cell Communication

Cell Communication

cell-to-cell communication(signaling) is critical for the function and survival of cells

responsible for the growth and development of multicellular organisms

involves the transmission of signal from a sending cell to a receiving cell

cells communicate by direct contact and local or long distance signaling

Direct Contact

communication by cell-cell contact

2 types are direct channels of communication and cell-cell recognition

Direct channels of communication

signaling substances exchange directly between the cytoplasm of two adjacent cells via channels

animal cells: gap junctions

plants: plasmodesmata

Cell-Cell recognition

complementary cell-surface molecules between adjacent cells can interact and bind to each other

ex. receptor/antigen interaction in immune system

Local Signaling

includes paracrine, synaptic, and autocrine signaling

Paracrine signaling

a signaling cell will release chemical messages(local regulators/ligands) that travel a short distance through the extracellular fluid and cause a response in a nearby target cell

ex. when exposed to allergens, mast cells release histamine that signal for an inflammatory response in nearby cells

synaptic signaling is a special type of paracrine signaling

Synaptic signaling

occurs in animal nervous system (a special type of paracrine signaling)

neurons secrete neurotransmitters(signaling molecules) that diffuse across the synaptic gap/cleft (space between the nerve cells and the target cell) and bind to receptors, causing a chemical change inside the receiving cell

Autocrine signaling

a cell signals to itself

cell releases a ligand that binds to receptors on the same cell to initiate signaling

allows the cell to regulate itself through positive and/or negative feedback

ex. macrophage cells release cytokines that can signal to the macrophage itself to regulate activity

Long-Distance Signaling

animals and plants use long-distance signaling molecules called hormones to produce a response in target cells that may be far from the signaling cell

plants release hormones that travel in the plant vascular tissue(xylem,water and phloem,food) or through the air to reach target tissues

animals use endocrine signaling-specialized cells release hormones into the circulatory system where they reach target cells ex. insulin

insulin is released by the pancreas into the bloodstream where it circulates through the body and binds to target cells