Unit 3

Question Answer
The resting membrane potential is maintained by Na K pumps that actively transport ___ into and ____ out of the cell. KNa
In RMP the concentration of ___ is higher inside than outside the cell. K
In RMP the membrane is more permeable to ____. K
In RMP the concentration of ___ is higher outside than inside the cell Na
EPSPs and IPSPs summate at the _____ __________. axon hillock
Most CNS neurons fall into which structural category? Multipolar
Which cell produces myelin and is located in the PNS? schwann cells
What cell produces myelin in the CNS? oligodendrocytes
Demyelination disorders such as Multiple Sclerosis and Guillain-Barre Snydrome are particularly dangerous because they do what? decrease the speed of action potential transmission
The sodium-potassium exchange pump stabilizes resting potential of the neuron membrane at about _____. -70 mV
The most abundant intracellular cation is _________ while the most extracellular anion is _____________. Potassium Chloride
Where do most action potentials originate? Initial segment
What opens first in response to a threshold stimulus? voltage gated Na channels
What characterizes depolarization, the first phase of the action potential? the membrane potential changes from a negative value to a positive value
What characterizes depolarization, the second phase of the action potential? Once the membrane depolarizes to a peak value of +30mV, it repolarizes to its negative resting value of -70mV
What event triggers the generation of an action potential? The membrane potential must depolarize from the resting voltage of -70 30mV to a threshold value of -55mV
What is the first change to occur in response to a threshold stimulus? Voltage-gated Na channels change shape, and their activation gates open.
What type of conduction takes place in unmyelinated axons? continuous conduction
An action potential is self-regenerating because__________. depolarizing currents established by the influx of Na flow down the axon and trigger an action potential at the next segment
Why does regeneration of the action potential occur in one direction, rather than in two directions? The inactivation gates of voltage-gated Na channels close in the node, or segment, that had just fired as action potential.
What is the function of the myelin sheath? The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
What changes occur to voltage-gated Na and K channels at the peak of depolarization? Inactivation gates of voltage-gated Na channels close, while activation gates of voltage-gated K channels open
In which type of axon will velocity of action potential conduction be the fastest? Myelinated axons with the largest diameter
What is an example of a presynaptic cell? a neuron
What separates the presynaptic and postsynaptic cells at a chemical synapse? synaptic cleft
What role does calcium have in synaptic activity? Calcium influx into the synaptic terminal causes vesicle fusion with the plasma membrane in the release of neurotransmitter.
What is the role of neurotransmitter at a chemical synapse? Neurotransmitter binds to receptors on the postsynaptic cell membrane
What is the primary role of the enzyme AChE At a cholinergic synapse? Ache degrades Ach in the synaptic cleft
If a nerve cell receives many IPSPs In different locations at the same time ____. It will show spatial summation
The neurotransmitter GABA blocks presynaptic voltage-gated calcium channels. Consequently, GABA produces _______.

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