Physiology Chapter 1 Quiz

Study Notes

Physiology is the study of the normal functioning of a living organism and its parts.
Levels of organization range from atoms to molecules, cells, tissues, organs, organ systems, and finally, the organism.

Homeostasis is maintaining a stable internal environment, despite external fluctuations.
Homeostasis is a dynamic steady state, not static equilibrium.
Sickness or disease occurs when homeostasis is disrupted for an extended time.
Negative feedback: Reverses a change to return to a set point.
- Example: Regulating body temperature; when body temperature rises, sweating occurs to cool you down.
Positive feedback: Amplifies a change, pushing the system further away from a set point.
- Example: Childbirth, where oxytocin release triggers uterine contractions, which cause more oxytocin release.
Feedforward control: Anticipates changes and activates mechanisms to prevent deviations.
- Example: Salivation before eating.

Osmotic Equilibrium: The total solute concentration is the same on both sides of the cell membrane, preventing net water movement.
Chemical Disequilibrium: Ions and other solutes have unequal concentration across cell membranes.
Electrical Disequilibrium: An uneven distribution of ions creates a difference in electrical charge across the cell membrane, creating a resting membrane potential (typically -70 mV). This is maintained by ion channels and pumps.
Example of a primary active transport carrier: Sodium-potassium ATPase pump (Na+/K+ ATPase).
- This pump moves 3 sodium ions out of the cell and 2 potassium ions into the cell, using energy from ATP.

Simple Diffusion: Passive movement of molecules down their concentration gradient. Examples include oxygen and carbon dioxide.
Protein-Mediated Transport:
- Facilitated Diffusion: Passive transport with carrier proteins.
- Active Transport: Requires energy to move molecules against their concentration gradient, using carrier proteins or pumps.
- Ion Channels: Passive transport allowing specific ions to pass based on electrochemical gradient.
Vesicular Transport: Active transport involving vesicles for moving large molecules or substances, like in exocytosis (releasing molecules) and endocytosis (taking molecules into the cell structures).

Channels: Passive, fast, have selectivity based on size and charge.
Facilitated Diffusion Carriers: Passive, slower, conformational changes involved.
Active Transport Carriers: Active, requires energy, usually moves molecules against their concentration gradient.

Changing ion permeability alters membrane potential.
- Increased Na+ permeability depolarizes the membrane (e.g., during action potential).
- Increased K+ permeability repolarizes the membrane
- Increased Cl- permeability may also depolarize the membrane.