Chapter 8: Neurons and Action Potentials

The resting potential of a neuron is ________

-70 mV

The diagram below depicts an action potential, during which phase is the cell depolarizing?

B

In the diagram below, when is Na+ moving out of the cell?

D

T or F: An action potential will diminish (lose strength) over time

False

If a hyperpolarizing graded potential and a depolarizing graded potential of similar magnitudes arrive at the trigger zone at the same time, what is most likely to occur? -Nothing. They will cancel each other out. -An action potential is fired off more quickly than usual. -The cell becomes easier to excite because it depolarizes. -The cell dies. -The cell becomes hyperpolarized.

Nothing. They will cancel each other out.

T or F: A graded potential will diminish (lose strength) over time

True

Action potentials are begin at the _____________.

axon hillock

The ion necessary to initiate the release of acetylcholine into the synaptic cleft is -potassium -calcium -chloride -zinc -sodium

calcium

The pattern of synaptic connectivity where a large number of presynaptic neurons provide input to a single postsynaptic neuron, is known as -divergence -saltatory conduction -integration -convergence

convergence

Neurotransmitters are usually released into synapses by __________. -simple diffusion -protein-mediated transport -active transport -exocytosis

exocytosis

In order to signal a stronger stimulus, action potentials become

more frequent only

Spatial summation refers to -electrical signals reaching neurons from outer space. -suprathreshold potentials triggering action potentials that are extra-large. -repeated graded potentials reaching the trigger zone one after the other -multiple graded potentials arriving at one location.

multiple graded potentials arriving at one location.

During the relative refractory period follwing an action potential a stimulus _____________________ -will usually not trigger another action potential -will always trigger another action potential -must be larger than normal to trigger another action potential -will never trigger another action potential

must be larger than normal to trigger another action potential

These are the sites where saltatory conduction occurs in an action potential

nodes of Ranvier

Cells in the CNS that form mylein are called ________________

oligodendrocytes

Inhibitory postsynaptic potentials (IPSPs) -result in depolarizations -result in hyperpolarizations. -decrease potassium ion exit from the cells. -increase membrane permeability to sodium ions -decrease calcium ion exit from cells

result in hyperpolarizations.

You were hired to work on a research project to design a drug. Which of these drug mechanisms would decrease the amount of neurotransmitter in the synaptic cleft? -decreasing diffusion -inhibiting enzymes (like MAO) that break down neurotransmitters -blocking receptors with an antagnoist -stimulating uptake

stimulating uptake

The space between the presynaptic neuron and the postsynaptic neuron is called the -synaptic void -soma -synapse -synaptic cleft

synaptic cleft

When a second EPSP arrives at a single synapse before the effects of the first have disappeared, what occurs? -hyperpolarization -spatial summation -inhibition of the impulse -decrease in speed of impulse transmission -temporal summation

temporal summation

The total amount of neurotransmitter released at the axon terminal is directly related to the -length of the axon -amplitude of the graded potential -amplitude of the action potential. -total number of action potentials

total number of action potentials