Unit 2 - A & P Module - Organization Electrical Potentials and Signaling Flashcards
Neurons that innervate smooth muscle (such as the lining of blood vessels or the GI tract) belong to the __________ nervous system.
peripheral and autonomic
How do refractory periods contribute to the properties of an action potential?
Directionality, all or none, and coding of stimulus strength by frequency
The resting membrane potential of a cell is produced by ion movements through __________.
potassium leak channels and sodium leak channels
In sodium channels at the resting membrane potential, the activation gate is __________ and the inactivation gate is ________.
closed; open
Put the following events of an action potential in the correct order, starting with depolarization:
a. Na+ permeability > K+ permeability
b. K+ permeability > Na+ permeability
c. mV approaches EK+
d. mV approaches ENa+
(mV =membrane potential; EK+ =equilibrium potential for potassium; ENa+ =equilibrium potential for sodium)
a, d, b, c
Action potentials propagate down the axon like __________.
a row of falling dominoes, by current flow through the intra- and extracellular fluid around sequential areas of axonal membrane, and by current flow through electronic conduction
Schwann cells are located in the __________ and are a type of _____ cell.
peripheral nervous system; glial
Outside the central nervous system, clusters of neuron cell bodies are called __________, and axons travel together in bundles called __________.
ganglia; nerves
The positive feedback loop during the depolarization phase of the action potential is “turned off” during repolarization because __________.
inactivation gates on Na+ channels are closed and K+ channels open
In neurons that generate many action potentials, why don’t the ion gradients across the neuron’s cell membrane dissipate?
The Na+/K+ ATPase helps reestablish the gradients by actively transporting ions back across the neuronal membrane and even though the membrane potential can change dramatically, very few ions actually move across the neuronal membrane during each action potential.
Graded potentials and action potentials are similar in that they both __________.
incorporate voltage-gated sodium channels, are “all or none,” can diminish with distance, and code stimulus strength by amplitude
The resting membrane potential depends directly or indirectly on __________.
the ion permeability of the cell membrane, the concentration gradients of ions across the cell membrane, the Na+/K+ ATPase pump
In contrast to almost all other cell types in the body, neurons __________.
can change their membrane potential and the permeability of their plasma membranes
If the Na+/K+ ATPase were turned off, what would happen to the membrane potential?
It would become less negative.
The Na+/K+ ATPase is responsible for producing that concentration gradient across the neuron cell membrane via active transport. Without it, Na+ and K+ would diffuse along their concentration gradients, eventually reaching equilibrium. This would cause the membrane potential to move towards zero, thus become less negative.
