Human Physiology (Biol 236)
Exam Outline

Chapter 2, part 2 Outline (updated 9/92022)
Transport Across Cell Membranes
• What is the difference between permeable and selectively permeable membrane?

Know the 4 types of passive transport:
1. Simple diffusion (gases like O2 and CO2 can do this)
2. Facilitated diffusion
- facilitated diffusion with ion channels (such as ion channels for Na+, Ca+2, K+, or Cl-)
- facilitated diffusion with protein carriers (they are like a revolving door on cell membrane)
3. Osmosis (know how water moves across cell membranes when a cell is in a hypertonic, hypotonic, and isotonic solution)
4. Filtration (or dialysis) - this is how arterial blood gets filtered by kidney nephrons.

Know the two categories of active transport:
• Primary active transport (Ca+2, H+, and Na+/K+ pumps - and where you would find these types of pumps)
• Secondary active transport (co-transport and counter transport)
• Regarding co-transport of Na+ and glucose, what is its significance with respect to oral rehydration therapy? Why does this co-transport help hydrate patients having diarrhea? See online reading: Oral Rehdyration Therapy and counter-transport
• For bulk transport:
- What is endocytosis? (phagocytosis, pinocytosis, and receptor-mediated endocytosis)
- What is exocytosis?

Cell Membrane Potential and Depolarization of Cell Membranes (action potentials)
• What is the normal resting cell membrane potential? (-70mv)
• What are the steps for formation of an action potential (depolarization) and return to resting state (repolarization) in a cell?
1. stimulus occurs above the membrane threshhold
2. Opening of Na+ channels and inward movement of Na+ ions, which causes membrane potential to go to +30mv & causes depolarization (an action potential that stimulates a cell)
3. Opening of K+ channels and outward movement of K+ ions = repolarization or rest of a cell (but often causes membrane potential to go too low (-80mv), called hyperpolarization.
4. Na+/K+ pumps pump 3 Na+ out of cell for every 2 K+ pumped into cell. This brings membrane potential back to -70mv.
• Why can hyperkalemia result in cardiac arrest or death? See clinical app on hyperkalemia

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