Initiation and transmission of electrical signals. Neuron Spinal ganglion 3. Stratified squamous epithelium Simple cuboidal epithelium 4. Cells must have a stable environment . Maintaining a constant internal environment in spite of changes in the external environment.
Homeostasis is the central theme of physiology.
Negative feedback loop. When a change in the controlled variable triggers a response that opposes the change. Positive feedback loop. When a change in the controlled variable triggers a response that sustains or accelerates the change. A tentative and general explanation of a group of observations.