PHYSIOLOGY HELP Membrane Potential 1. Which are true regarding membrane potentia
ID: 3477375 • Letter: P
Question
PHYSIOLOGY HELP
Membrane Potential 1. Which are true regarding membrane potential? Circle all correct or none if none correct. (5 pts)
a. If a neuron increases in permeability to Cl-, the cell will hyperpolarize and Vm will decrease.
b. Only excitable cells have a resting membrane potential difference.
c. Potassium has the greatest effect on Vm because it is the major intracellular ion.
d. Only permeant ions can directly affect Vm. e. Inhibition of the Na+/K+ ATPase immediately eliminates resting membrane potential difference.
4. a. Are pancreatic beta cells excitable? Circle one: yes no sometimes (2 pts)
b. Give a brief mechanistic explanation of what makes a tissue excitable. ( 15 words) (4 pts)
Extra credit (1 pt) If ECF concentration of Na+ increases 10x without a corresponding increase in ICF concentration, what will be the effect on ENa? Answer:
Briefly explain.
Extra credit (1 pt): What specific part of the brain is the integrating center for digestive functions (or malfunctions) such as swallowing and vomiting?
2. Compare and contrast cardiac pacemaker and contractile cells. Use the distribution of ions given in the tables in order to answer some of the questions. Circle P for pacemaker, C for contractile, B for both, N for neither. (8 pts Pacemaker [ECFl mM ICF mMPi Na+ Contractile[ECFI mM ICFl mMPi 0.5 75 0.5 142 0.6 Na+ 142 142 142 12 Cl 145 a. have hyperpolarization-activated channels b. resting Vn close to Ek+ c. hypothetical resting potential~- 14 mV d. propagation of potential is due to calcium influx e. refractory period of 200 msec or more f. regenerative potential threshold is - 40 mV g. excitable cells h. neurogenicExplanation / Answer
1. Resting membrane potential is the potential generated across membrane when the cell is at rest. It is ar ound -70mv. It is only present in resting cells. All cells including excitable cells will have a resting potential.
When chloride ions, enter the cells, the membrane will hyperpolarize due to effects on sodium ions. Hence, the membrane potential Vm will decrease.
Voltage dependent gating is dependent on permeant ions. Permeant ions are those ions that can pass through a semipermeable membrane. Permeant ions such as sodium and potassium pass through the neuron membrane through voltage gated channels.
Potassium is the major intracellular anion. Movement of potassium outside the cell hyperpolarizes the membrane generating a negative membrane potential.
The sodium potassium ATPase pump maintains overall concentrations of ions across the membrane. When this pump is blocked, the movement of ions will reduce. Movement of sodium and potassium ions requires ATP that is provided by the pump. Sodium ion concentration increases within the cell, while K+ levels fall in the cell. This induces depolarization of the resting membrane potential. The membrane potential will slowly decrease from 70 to 0. This effect is not immediate. The cell will have a resting potential for hours.
Options b and e.
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