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8 Cards in this Set
- Front
- Back
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Describe negative feedback, positive feedback, and feed forward systems. |
Negative feedback: react to changes in a physiological variable to cause the variable to RETURN to the NORMAL values.
Positive feedback: when there is a deviation of the controlled variable from the set point, the integrator sends a signal to the effector to move the controlled variable FARTHER away from the set point (normal value).
Feed forward: a control system that responds in ANTICIPATION of a change. |
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List intracellular and extracellular concentrations of Na+, K+, Ca++ and Cl- |
Intracellular: Na+ = 15mM, K+ = 150, Ca++ = .0001, Cl- = 7
Extracellular: Na+ = 145mM, K+ = 5, Ca++ = 1, Cl- = 110 |
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List functions of membranes. |
1. Regulate passage of substances into and out of the cell- form selective barrier.
2. Detect chemical messengers arriving at cell surface.
3. Recognition of "self" (immune function)
4. Link cells to the extracellular matrix
5. Link adjacent cells together by membrane junctions. |
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List the characteristics of passive transport systems |
1. Does not require energy.
2. Solutes move across the membrane down their concentration gradient. (high concentration to low concentration)
3. Simple diffusion: diffusion of solutes across membranes through the lipid bilayer
4. Pores: integral proteins that are always open. Ex=aquaporins
5. Channels: transmembrane proteins that allow flow of ions, can be opened or closed. Ex: ligand-gated, voltage-gated, & mechanosensitive channels.
6. Facilitated diffusion: transports large non polar molecules via a carrier protein. Ex. glucose and urea.
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List variables that affect diffusion of solutes across membranes and know how changes in those variables affect diffusion of solutes |
1. Concentration gradient: increasing gradient increases the magnitude; decreasing the gradient decreases the magnitude.
2. Temperature: increasing the temperature increases the magnitude.
3. Mass of solute: increasing the mass (heavier solute) DECREASES the magnitude
4. Surface area of diffusion: increasing the surface area increases the magnitude.
5. Physical medium: gas > liquid > solid
6. Permeability factor (pores and channels): pores will allow solutes to diffuse faster than channels since they are always open. Using a carrier protein is the slowest since transport occurs by cycling and only a few solutes can be transported per cycle. |
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List which types of solutes can cross the membrane by simple diffusion and what types of solutes require transport system to pass across membranes |
-Gasses and small lipophilic, hydrophobic molecules [fatty acids, steroids, ethanol], and unionized form of free acids&bases can cross the membrane by simple diffusion. -Water needs an aquaporin to cross membranes -Ions need channels to cross membranes -Glucose and urea need a carrier protein to cross the membrane
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List the types of channels and describe their characteristics |
1. Ligand-gated channels: are activated by chemical messengers (ligands). Ex of ligands: neurotransmitters, hormones, paracrines and drugs.
2. Voltage-gated channels: are activated by changes in membrane potential.
3. Mechanosensitive channels (stretch receptors): are activated by changes in the shape of the plasma membrane (stretch). These channels are involved in multiple sensory systems including touch, sensing blood pressure and osmolarity. |
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List characteristics of facilitated diffusion |
Facilitated diffusion: transport mechanism for large, non polar molecules (glucose and urea). A carrier protein is required due to the size and charge of molecules. Transport occurs via cycling and only one or two solutes can be transported across the membrane per cycle. [Facilitated diffusion via carrier proteins is SLOW] |
