homeostasis (intro to physiology)

Question 1

Cannon’s Four Postulates

Answer 1

• Sates of maintaining a “similar condition”
  1. The nervous system has a role in preserving the “fitness” of the internal environment (for normal function)
  2. Some systems are under tonic control (turning up or down the volume)
  3. Some systems are under antagonistic control (paired factors with opposing effects, controlled by nervous and/or endocrine regulation)
  4. One chemical signal can have different effects in different tissues (different receptors)

Question 2

The hormone epinephrine has multiple effects in mediating the body’s response to short term stress

Answer 2

• different receptors = different cell responses
  - epinephrine will cause vessel constriction in an intestinal blood vessel that has alpha receptors while it was cause skeletal muscle blood vessels with beta receptors to dilate
• in a liver cell, this will cause glycogen break down and glucose release from the cell due to different intracellular proteins to create different cell responses
• signal transduction pathway dictates cellular response too

Question 3

general model of homeostasis

Answer 3

deviation in controlled variable –> detected by sensor –> informs the integrator –> sends instructions to the effectors –> bring about compensatory response –> results in controlled variable restored to normal –> leads to negative feedback to shut off the system responsible for the response