Deck 21: Nerve Cells

Question 1

How do researchers measure ion movements through single channels?

Answer 1

Patch clamping is a technique that measures the electric current caused by the movement of ions across a small patch of the plasma membrane.The membrane is electrically depolarized or hyperpolarized and maintained (clamped)at that potential by an electronic feedback device.The inward or outward movement of ions across a patch of membrane can be quantified from the amount of electric current needed to maintain the membrane potential at the designated "clamped" value.

Question 2

Why are nongated channels important in the generation of an inside-negative electric potential (voltage)of 50-70 mV across the plasma membrane of cells?

Answer 2

If there is no ion movement across the membrane,there is no membrane potential.This is true even if there is a difference in ion concentrations on either side of the membrane.The presence of K⁺ channels that are usually open allows for ion movement from the inside of the cell to the outside and the creation of a negative membrane potential inside the cell.

Question 3

During a knee jerk reflex,which of the following steps occurs first?

A)stretch receptor is activated
B)interneuron sends an inhibitory signal to the hamstring muscle
C)motor neuron stimulates the quadriceps muscle
D)action potential travels along a sensory neuron

Answer 3

A

Question 4

The resting potential of a typical neuron is:

A)−60 mV.
B)0 mV.
C)20 mV.
D)50 mV.

Question 5

Which cells produce myelin?

A)oligodendrocytes
B)Schwann cells
C)astrocytes
D)Schwann cells and oligodendrocytes
E)all of the above

Question 6

Action potentials are propagated in only one direction,down the axon.Explain how the absolute refractory period of the voltage-gated Na⁺ channels and the brief hyperpolarization resulting from K⁺ efflux produces this outcome.

Question 7

During an action potential,which happens first?

A)opening of voltage-gated Na⁺ channels
B)closing of voltage-gated Na⁺ channels
C)opening of voltage-gated K⁺ channels
D)closing of voltage gated K⁺ channels

Question 8

The resting membrane potential in animal cells depends largely on nongated _____ channels.

A)Ca²⁺
B)H⁺
C)K⁺
D)Na⁺

Question 9

Action potentials:

A)vary in intensity
B)vary in frequency and timing
C)result in a decrease in resting potential
D)all of the above

Question 10

Action potentials are:

A)pulses of ion flow along axons.
B)brief local voltage changes within a neuron from inside-negative to inside-positive.
C)transmembrane potentials that result from the action of the Na⁺/K⁺ ion pump.
D)electrical signals used by glial cells to transmit information.

Question 11

In a human brain,the number of glial cells is:

A)about 1/10 the number of neurons.
B)about the same as the number of neurons.
C)about 10 times the number of neurons.
D)about 100-200 times the number of neurons.

Question 12

The birth of new neurons in the adult brain occurs in:

A)the dentate gyrus.
B)the brainstem.
C)olfactory bulb.
D)neural tube.

Question 13

Where are voltage-gated Na⁺ channels concentrated?

A)spaced uniformly along the axon membrane
B)clustered at the nodes of Ranvier
C)clustered at the axon terminus
D)embedded within the myelin sheath

Question 14

Fruit flies carrying the shaker mutation have motor neurons with an abnormally long action potential because of:

A)a defect in the Na⁺/K⁺ pump.
B)a defect in voltage-gated Na⁺ channels.
C)a defect in non-voltage-gated K⁺ channels.
D)a defect in voltage-gated K⁺ channels.

Question 15

Repolarization during the refractory period is largely due to the:

A)opening of non-voltage-gated K⁺ channels.
B)opening of voltage-gated K⁺ channels.
C)opening of voltage-gated Na⁺ channels.
D)action of the Na⁺/K⁺ pump.

Question 16

Which of the following is NOT a function of astrocytes?

A)stimulate blood vessels in the brain to maintain tight junctions
B)provide growth factors to neurons
C)produce extracellular matrix
D)excite muscle cells

Question 17

Which of the following represents a correct structure-function relationship for neurons?

A)cell body - sends signal to another cell
B)axon - contains the nucleus of the cell
C)dendrite - forms synapses with other neurons
D)axon termini - receive incoming signals

Question 18

What starts an action potential in a post-synaptic neuron?

Question 19

How are most voltage-gated channels inactivated?

A)by ligand binding
B)by changes in membrane potential
C)through interaction with other membrane proteins
D)by closing spontaneously soon after opening

Question 20

Which cells produce myelin sheaths?

A)Schwann cells and oligodendrocytes
B)astrocytes
C)afferent neurons
D)interneurons

Question 21

Botulinum toxin acts on:

A)SNARES to promote vesicle fusion.
B)AMPA receptors to inhibit LTP.
C)calcium receptors to increase acetylcholine release.
D)VAMP to prevent fusion with SNARE complexes.

Question 22

Acetylcholine receptor loss is observed in people with:

A)schizophrenia.
B)drug addiction.
C)myasthenia gravis.
D)all of the above

Question 23

Reception of taste causes:

A)an action potential that travels along the axon of a taste cell.
B)release of neurotransmitters that are detected by adjacent neurons.
C)an increase in cGMP that inactivates ligand gated Na⁺/Ca⁺² channels.
D)activation of TRPV1,which is a ligand gated Na⁺/Ca⁺² channel.

Question 24

Electrical synapses depend on:

A)neurotransmitters and receptor proteins.
B)calcium channels.
C)gap junction channels.
D)all of the above

Question 25

How does opening and closing of voltage-gated cation channels occur?

Question 26

Botulinum toxin inhibits nerve transmission by targeting:

A)the acetylcholine receptor.
B)VAMP.
C)dynamin.
D)synaptotagmin.

Question 27

Which of the following proteins is NOT part of a four-helix complex that mediates fusion of synaptic vesicles with the plasma membrane?

A)NSF
B)SNAP-25
C)syntaxin
D)VAMP

Question 28

Touch receptors are:

A)non-gated cation channels.
B)gated cation channels.
C)calcium ion pumps.
D)G protein-coupled receptors.

Question 29

Evidence that synaptotagmin is the Ca²⁺ sensor for exocytosis of neurotransmitters includes:

A)Ca²⁺ binding by synaptotagmin.
B)partial loss-of-function mutations of synaptotagmin in Drosophila and C.elegans that result in neurons that are defective in Ca²⁺-stimulated vesicle exocytosis.
C)uncoordinated embryonic muscle contractions in Drosophila and c.elegans mutants that lack synaptotagmin.
D)all of the above

Question 30

How does the nicotinic acetylcholine receptor function as a ligand-gated ion channel at nerve-muscle synapses?

Question 31

Myelinated axons have the conduction velocity of much larger axons (unmyelinated of course)because of all the following reasons,except:

A)voltage channels are only present at the nodes of Ranvier.
B)saltatory conduction.
C)more ion channels are present in myelinated axons.
D)insulation.

Question 32

Two signaling proteins,agrin and neuregulin,have been identified in studies of neuromuscular junction development.In the absence of neuregulin:

A)Schwann cells die.
B)postsynaptic structures do not form in muscle cells.
C)the acetylcholine receptor protein is not synthesized.
D)all of the above

Question 33

Why do chili peppers seem hot?

Question 34

During the development of specialized postsynaptic structures at a neuromuscular junction,preexisting AChR proteins on the surface of the uninnervated muscle are induced to aggregate by:

A)agrin,a signal released from the neuron.
B)the muscle membrane protein,MuSK.
C)the cytosolic protein,rapsyn.
D)all of the above

Question 35

Neurotransmitters are stored in:

A)the cell body.
B)the dendrite.
C)the axon hillock.
D)synaptic vesicles.

Question 36

Explain how the expression of the H⁺/acetylcholine antiporter and the choline acetyltransferase enzyme are coordinated.

Question 37

Signaling at synapses is usually terminated by:

A)calcium influx.
B)potassium influx.
C)inhibitory neurotransmitters.
D)degradation or reuptake of neurotransmitters.

Question 38

How are neurotransmitters packaged at synaptic endings for quantal release?

Question 39

Describe the common features of the GABA,norepinephrine,dopamine,and serotonin transporter proteins.

Question 40

Taste receptors are either channel proteins or:

A)sodium ion pumps.
B)potassium ion pumps
C)calcium ion pumps
D)G protein-coupled receptors.

Question 41

Long-lasting memories:

A)are formed in the subventricular zone.
B)trigger a loss of CAMKII alpha activity.
C)do not require protein expression to be potentiated.
D)trigger increases in AMPA receptors postsynaptically.

Question 42

Silencing of the gene encoding FMRP:

A)decreases translation of mRNAs near the dendrites.
B)is associated with Huntington's disease.
C)results in less spatiotemporal regulation of neuron-specific protein expression.
D)causes mice to solve mazes more quickly.

Question 43

Long-lasting effects of habituation involve:

A)stimulation of sensitizing interactions.
B)decreasing numbers of connections between sensory and motor neurons.
C)movement of the Golgi apparatus out into the dendrites.
D)rewiring of neurons in the spinal cord.