Cell Signaling and Homeostasis: Mechanisms and Types in Physiology

Cell signaling

Allows organisms to have responses to their environment that are appropriate and coordinated to the experience.

Endocrine signals

Released into the blood stream to provide system-wide coordination.

Hormones

Signal molecules of the endocrine system.

Nervous system signals

Released into a synapse that joins the neuron to its downstream cells.

Neurotransmitters

Signaling molecules of the nervous system.

Paracrine signals

Growth factors, cytokines, etc. released into local fluids to coordinate cells in the sender's vicinity.

Juxtacrine signals

Molecules bound to the surfaces of two cells in direct contact to coordinate the activity of both.

Direct exchange of cytosolic components

Coordinates the activities of two cells in direct contact through direct transfer of cytosolic contents.

Gap junction

A structure that allows direct exchange of cytosolic components between two cells.

Homeostasis

An automatic system for maintaining internal conditions in a changing external environment.

Homeostatic Receptors

Monitor the variable and respond to changes by sending signals to report increases/decreases.

Homeostatic Control Centers

Respond to reported changes by signaling for an appropriate action to return to present.

Homeostatic Effectors

Respond to control signals by bringing the variable back within the normal range.

Negative Feedback Loop

Process that slows or stops a physiological response.

Positive Feedback Loop

Process that quickens or increases a physiological response.

Hyperthermia

Core temperature above 104°F.

Hypothermia

Core temperature below 95°F.

Homeostatic Failure

Underlies many disease states and has tremendous clinical significance for organisms.

Inherited gene defect

A cause of homeostatic failure resulting in disease.

Acquired disease

A cause of homeostatic failure resulting in disease.

Diabetes

An example of a condition where homeostatic mechanisms may fail.