Quiz 9
What is the correct order for the events of neurotransmitter release from the synaptic terminal? 1 - Extracellular Ca2+ enters terminal and binds to sensor protein in the cytoplasm 2 - Exocytosis of neurotransmitter into synaptic cleft 3 - Action potential reaches axon terminal 4 - Ca2+-protein complex stimulates fusion of the docked synaptic vesicle with the plasma membrane 5 - Voltage-gated Ca2+ channels open
3, 5., 1, 4, 2
The voltage-gated Na⁺ channels ____________ when the cell reaches +30mV.
CLOSE
Resting membrane potential is created as a result of a greater net flow of positive charges from the ____________ .
ICF to the ECF
When K⁺ diffuses out of the cell, the cell becomes ____________ depolarized.
LESS
The cell membrane immediately adjacent to an action potential depolarizes because of
Local Currents
K⁺ diffusing out of the cell has a ____________ feedback effect on the initial polarization.
NEGATIVE
The voltage-gated Na⁺ channels ____________ when the cell membrane reaches threshold level as a result of a stimulus.
OPEN
What type of cells produce the myelin sheath in the central nervous system (CNS)?
Oligondendroctyes
Have central and peripheral processes
Unipolar neurons
What is produced when depolarization of a cell membrane reaches threshold?
a new action potential is produced
Pain receptors in the skin send signals to the CNS for processing. These pain receptors are an example of ____________ neurons.
afferent
In order to maintain the electrochemical gradients for sodium and potassium, ATPase pumps move these ions ____________ their respective gradients.
against
No axons are present
anaxonic neurons
Only produce local potentials
anaxonic neurons
One dendrite and one axon
bipolar neuron
Have one axon and one dendrite
bipolar neurons
The diffusional movement of sodium and potassium across the membrane is driven at all times by the ____________ .
electrochemical gradient
On a graph of an action potential, the small depolarizations that lead to threshold are from
excitatory postsynaptic potentials (EPSPs).
In neurons, protein pumps allow substances to move passively down their concentration gradients.
false
When Na⁺ diffuses into the cell, the cell becomes ____________ depolarized.
more
Depolarization is initiated by a stimulus that makes the membrane potential
more positive
Depolarization of a cell membrane occurs because
more sodium ions diffuse into the cell than potassium ions diffuse out of it.
Many dendrites and a single axon
multipolar neuron
Most common type of neuron
multipolar neuron
Have many dendrites and one axon
multipolar neurons
The absolute refractory period assures that action potential propagation is
only in one direction
A depolarizing graded potential can cause an action potential.
true
Graded potentials can result from mechanical stimulation or temperature changes.
true
Graded potentials can result from voltage across the plasma membrane.
true
Activation gates in the cell membrane for voltage-gated sodium ion channels open into the
extracellular fluid
Na+ diffusing into the cell causes more Na+ gates to open, which is a ___________
positive feedback loop
When sodium enters the neuron via chemically gated sodium channels, the membrane will depolarize. Therefore, the membrane potential will become more
postitive
Though potassium and sodium both leak through the membrane at rest, there is a greater diffusional flow of ____________ at rest.
potassium
The electrical and chemical gradients for ____________ are both high during resting membrane potential which results in a very high electrochemical gradient toward the inside of the cell.
sodium
Increased permeability of the membrane to sodium results in depolarization.
true
On a typical neuron, the axon is usually longer in length than the dendrites.
true
The effects produced by one graded potential can be added onto the effects of another graded potential.
true
The leakage of potassium plays a more significant role in the resting membrane potential than the leakage of sodium.
true
the potential change can vary from small to large depending on the stimulus strength or summation.
true
One process with two branches; one extending to the CNS, one extending to the periphery
unipolar neuron
