Exam 1 Quiz Qs 1-3 Flashcards
In a voltage clamp, which of the following is measured?
Magnitude and direction of the ionic current
How does a voltage clamp work?
It holds the voltage of a neuron constant by injecting current equal to the ionic current passing across the cell membrane.
What is the main contributor to the absolute refractory period following the onset of an action potential?
Inactivation of voltage-gated sodium channels
Which cells form myelin sheets in the central nervous system?
Oligodendrocytes
What is the name of the periodic interruptions of myelin sheets along nerve fibers?
Nodes of Ranvier
Which factors make propagation of electrical signals in dendrites more complex than in axons?
Dendrites contain a wide variety of different voltage-gated ion channels
What drives primary active transport?
The hydrolysis of ATP
What drives secondary active transport?
Ion flux down their electrochemical gradient
Why is the sodium–potassium exchange pump said to be electrogenic?
Because it transports unequal numbers of sodium and potassium ions across the membrane
How can ion exchange mechanisms be made to run backwards?
By altering one or more of the ion gradient involved in the exchange
The neuronal connections in the nervous system can be
convergent, divergent, recurrent, or parallel
Which scientist defined the neuron as the single cell unit of the nervous system?
Ramon y Cajal
The signal intensity is encoded by which property of the action potential?
Frequency
Local graded potentials encode the intensity of a signal by
size of the membrane potential change
are arranged with their polar, hydrophilic heads facing outward and their hydrophobic tails extending to the middle of the layer.
Plasma membrane lipid molecules
Channel “activation” is a(n)
increase in the frequency of channel opening
Hyperpolarization occurs when the membrane potential
becomes more negative
Which is true of the potassium equilibrium potential?
It is the membrane potential where electrical forces and concentration gradients are equal and opposite
In a model cell at rest, what is the relative concentration of potassium inside the cell?
Higher than the concentration of potassium outside the cell
The action of the sodium-potassium exchange pump is electrogenic. What does this mean?
The exchange pump produces an electrical charge.
The signal intensity is encoded by which property of the action potential?
Frequency
Local graded potentials encode the intensity of a signal by
size of the membrane potential change
Channel “activation” is a(n)
increase in the frequency of channel opening
In a voltage clamp, which of the following is measured?
Magnitude and direction of the ionic current
How does a voltage clamp work?
It holds the voltage of a neuron constant by injecting current equal to the ionic current passing across the cell membrane.
The late current observed in voltage clamp experiments contributes to which of these phases of the action potential?
Repolarization
Which of the following ions is responsible for the late current following a voltage step in a voltage clamp experiment?
Potassium
Which of the following can be attributed to the flow of sodium ions across the membrane?
Early current
When Hodgkin and Huxley recorded from a neuron under voltage clamp at +52 mV, which of the following describes what they observed?
No early current and an outward late current
When triethanolamine (TEA) is applied to a neuron in a voltage clamp experiment, what results are observed?
An inward early current followed by no late current
