Untitled Quiz

Study Notes

Physiology is the study of the normal functioning of living organisms and their parts.
Levels of organization from smallest to largest: atoms → molecules → cells → tissues → organs → organ systems → organism.

Homeostasis is the maintenance of a relatively stable internal environment despite external changes.
Homeostasis is a dynamic steady state, not equilibrium.
Disease or sickness occurs when homeostasis is disrupted for long periods.
Negative feedback: Reverses a change to return to a set point (e.g., regulating body temperature).
Positive feedback: Amplifies a change, moving the system further from the set point (e.g., childbirth).
Feedforward control: Anticipates changes and activates mechanisms in advance (e.g., salivation before eating).

Osmotic Equilibrium: The total solute concentration is equal on both sides of the cell membrane.
Chemical Disequilibrium: Different solutes have uneven distributions across the cell membrane (e.g., sodium higher outside, potassium higher inside).
Electrical Disequilibrium: Ions create a charge difference across the membrane (resting membrane potential, typically around -70 mV). This is maintained by ion channels and pumps (e.g., Na+/K+ ATPase).

Simple Diffusion: Passive movement of molecules down their concentration gradient (e.g., oxygen and carbon dioxide).
Protein-Mediated Transport:
- Facilitated Diffusion: Passive transport using carrier proteins (e.g., glucose transporters).
- Active Transport: Requires energy (ATP) to move molecules against their concentration gradient (e.g., Na+/K+ pump).
  - Direct active transport uses ATP directly.
  - Indirect active transport uses the energy from an existing gradient.
- Ion Channels: Allow specific ions to pass through the membrane (e.g., voltage-gated Na+ channels) - passive due to electrochemical gradient.
Vesicular Transport: Active transport involving vesicles (e.g., endocytosis, exocytosis, and phagocytosis).

Channels:
- Passive movement of ions or water.
- Selective based on size and charge.
- Fast, allowing many ions to pass simultaneously.
Facilitated Diffusion Carriers:
- Passive, binds specific molecules.
- Slower than channels, undergoes conformational changes for each molecule.
- Example: GLUT transporters.
Active Transport Carriers:
- Require ATP or other energy sources.
- Moves molecules against their gradients.
- Example: Na+/K+ ATPase pump (3 Na+ out, 2 K+ in).

Specificity: Carriers are specific to certain molecules or closely related molecules (e.g., glucose transporters).
Competition: Similar molecules can compete for the same carrier.
Saturation: There is a maximum transport rate (Tmax) for carriers at high substrate concentrations.
Ion Permeability and Membrane Potential: Changes in ion permeability alter membrane potential (e.g., increased Na+ permeability depolarizes the membrane).

Insulin secretion (beta cells), requiring the understanding of glucose levels impacting the permeability of various membrane proteins like K+ ATP and voltage gated calcium channels, to influence insulin secretion.