Which of these is not a characteristic of an action potential?
Each normal action potential for a given cell type looks identical, depolarizes to the
... [Show More] same potential, and
repolarizes back to the same resting potential.
An action potential at one site causes depolarization at adjacent sites, bringing those adjacent sites to
threshold.
If an excitable cell is depolarized to threshold in a normal manner, then the occurrence of an action
potential is inevitable. On the other hand, if the membrane is not depolarized to threshold, no action
potential can occur.
Action potentials always occur following an increased conductance of chloride ions.
Question 2
1 / 1 pts
Which of these statements about refractory period is not true?
During the refractory periods, excitable cells are incapable of producing normal action potentials
The basis for the absolute refractory period is closure of the inactivation gates of the Na + channel in
response to depolarization.
The basis for the relative refractory period is the higher K + conductance than is present at rest.
Because the membrane potential is closer to the K + equilibrium potential, more inward current is
needed to bring the membrane to threshold for the next action potential to be initiated.
When a nerve or muscle cell is depolarized rapidly, the usual threshold potential may lead to an action
potential having been fired. This process is called accommodation.
Question 3
1 / 1 pts
Which of these pH values of the ECF will most favor the formation of the lipophlic form of lidocaine if its
pKa is 7.9?
7.2
7.4
7.45
7.15
IncorrectQuestion 4
0 / 1 pts
Which of these is not a correct criterion for defining neurotransmitters?
The substance must be enzymatically degradable
The substance must be released by the presynaptic cell on stimulation
If the substance is applied exogenously to the postsynaptic membrane at physiologic concentration, the
response of the postsynaptic cell must mimic the in vivo response.
The substance must be synthesized in the presynaptic cell
Question 5
1 / 1 pts
The active tension developed in a muscle is proportional to the number of cross-bridges that cycle.
True
False
Question 6
1 / 1 pts
As the afterload on the muscle increases, the velocity will be decreased because cross-bridges can cycle
less rapidly against the higher resistance.
True
False
Question 7
1 / 1 pts
Which of these correctly describes osmosis?
Osmosis is the flow of water across a semi-permeable membrane due to a difference in solute
concentration
Under physiologic conditions, the reflection coefficient of albumin is 0 because it does not cross the cell
membrane
The reflection coefficient of urea is 1 because it is freely permeable
Two solutions with the same osmolarity and are isosmotic will necessarily be isotonic.
Question 8
1 / 1 pts
Which of these accurately describes the effect of acetylcholine in neuromuscular impulse transmission?
Acetylcholine binds to a muscarinic receptor on the motor-end-plate
Binding of acetylcholine to its receptor on the motor-end-plate generates an action potential
immediately
Binding of acetylcholine to its receptor on the motor-end-plate increases the permeability of the motor
end plate to both Na + and K + .
Binding of acetylcholine to its receptor on the motor-end-plate increases the permeability of the motor
end plate to both Na + but not K + .
Question 9
1 / 1 pts
Which of these ions has a higher intracellular to extracellular concentration ration in humans? [Show Less]