Chapter 12, A&P II

What is the resting membrane potential value (in mV) of a neuron?

- -70mV

Which high energy compound is used to drive the active Na+/K+ exchange pumps?

- ATP

Which neurotransmitter is released at adrenergic receptors?

Norepinephrine

There are two major categories of ion channels: leak channels and __________. inactive channels voltage-regulated channels passive channels active channels

active channels

Sensory receptors send sensory information to the Central Nervous System (CNS) using the ---- division of the PNS

afferent

The ________ division of the peripheral nervous system brings sensory information to the central nervous system. parasympathetic autonomic peripheral afferent somatic

afferent

Depolarization

any shift from the resting membrane potential toward a less negative potential (becomes more positive)

The simplest level of information processing takes place at the __________. axon terminals soma dendrites axon hillock

axon hillock

The site in the neuron where EPSPs and IPSPs are integrated is the dendritic membrane. chemical synapse. synaptic terminal. axon hillock. electrical synapse.

axon hillock

The movement of materials from the soma to the synaptic terminal is called __________. plasmolysis pinocytosis axoplasmic transport inactive transport

axoplasmic transport

Which of the following is NOT a neurotransmitter? norepinephrine dopamine nitrous oxide testosterone

testosterone

The Autonomic Nervous System (ANS) is divided into two parts

the Parasympathetic Nervous System and the Sympathetic Nervous System

At a(n) ________ synapse, a neurotransmitter is released to stimulate the postsynaptic membrane. osmotic electrical cell chemical gap

chemical

The ________ division of the nervous system carries motor commands to muscles and glands. spinal afferent efferent autonomic peripheral

efferent

the --- division sends motor commands from the CNS to effectors in the PNS

efferent

Which of the following glial cells can form a myelin sheath around axon fibers in the central nervous system? astrocytes oligodendrocytes microglia Schwann cells

oligodendrocytes

Hyperpolarization

the loss of positive ions

The minimum stimulus required to trigger an action potential is known as the summation. all-or-none response. threshold. potential. incentive.

threshold

What is the resting potential of a typical neuron? −136 mV −70 mV 0 mV +60 mV

−70 mV

Which of the following are NOT glial cells of the CNS? Schwann cells astrocytes microglial cells ependymal cells

Schwann cells

Small, wandering cells that engulf cell debris and pathogens in the CNS are called ependymal cells. oligodendrocytes. satellite cells. astrocytes. microglia.

microglia

The many functions of the astrocytes include which of the following? guiding neuron development repairing damaged nerve tissue controlling the interstitial environment All of the listed responses are correct.

All of the listed responses are correct.

The Extracellular Fluid (ECF) contains high concentrations ---- cations while the Intercellular Fluid (ICF) contains high concentrations of -- cations

Na+ and Cl- K+

SAME

S is for sensory, A is for afferent, M is for motor, and E is for efferent

The central nervous system consists of the __________. somatic and autonomic divisions brain and spinal cord sympathetic and autonomic divisions cranial and spinal nerves

brain and spinal cord

The decreased release of which neurotransmitter is the cause of Parkinson's disease?

dopamine

Norepinephrine (NE)

excitatory, depolarizing effect on the postsynaptic membrane

The presence of ________ dramatically increases the speed at which an action potential moves along an axon. a capsule glial cells plasma protein neurilemma myelin

myelin

The axon emerges from the soma at a thickened region called the __________. axon hillock Nissl bodies synaptic vesicle sarcoplasmic reticulum

axon hillock

Gamma-aminobutyric acid (GABA)

inhibitory; reduce activity

Compared with type C fibers, type A fibers have a larger diameter and can increase propagation __________ times faster. 120 30 60 15

120

What is the major anatomical difference between an anaxonic neuron and all other classified neurons?

- Anaxonic neurons: small, have numerous dendrites, no obvious axons, not readily visible - Bipolar neurons: small, one dendrite (with dendritic branches), one axon, cell body located in between the two - Unipolar neuron: dendrites and axons are continuous/fused and the cell body lies off to one side; the initial segment lifes where the dendrites converge; rest is an axon (relatively long) - Multipolar neurons: two or more dendrites and a single axon (long axons)

Describe the function of acetylcholineasterase. (hint: remember that any word ending with "ase" is an enzyme. Most enzymes are proteins, but not all proteins are enzymes).

- Break down molecules of ACh (hydrolysis) into acetate and choline - Choline is absorbed by the axon terminal and is used to synthesize more ACh, using acetate provided by coenzyme A (CoA) - Acetate diffusing away from the synapse can be absorbed and metabolized by the postsynaptic cell or by other cells and tissues

What part of the neuron is clustered in masses called ganglion?

- Cell bodies of neurons in the PNS

What is the relationship between myelin and the propagation speed of an action potential?

- Conduction, suggests a flow of charge similar to that in a conductor Myelin increases resistance to the flow of ions across the membrane

Describe what a neurotransmitter is and explain its function

- Important in cell-to-cell communication - a chemical substance that is released at the end of a nerve fiber by the arrival of a nerve impulse - by diffusing across the synapse or junction, causes the transfer of the impulse to another structure

Which neuron classification is the most common neuron found in the CNS?

- Multipolar neurons - (ex: all the neurons that control skeletal muscles)

What are the small gaps located between internodes of myelinated axons called?

- Nodes (of Ranvier)

Due to the concentrations of Na+ and K+ in their respective compartments (intercellular or extracellular), a passive chemical gradient occurs. What type of channel is involved in passive chemical gradients?

- Potassium leak channels, sodium leak channels - Potassium moves out of the cell, Sodium moves in

List and describe the function of 2 types of neuroglial cells found in the PNS

- Satellite cells: regulate the interstitial fluid around the neurons, much as astrocytes do in the CNS - Schwann cells: myelinate axons; non-myelinating Schwann cells can enclose segments of several unmyelinated axons

Where are bipolar neurons located?

- Sense organs where they relay information about sight, smell, or hearing from receptor cells to other neurons

List and describe the function of 4 types of neuroglial cells found in the CNS

- Separate and protect neurons - Provide a supportive framework for nervous tissue - Act as phagocytes - Help regulate the composition of the interstitial fluid - CNS - Astrocytes: maintain blood brain barrier; provide structural support; regulate ion, nutrient, and dissolved gas concentrations absorb and recycle neurotransmitters; form scar tissue after injury - Ependymal cells: line ventricles (brain) and central canal (Spinal cord); assist in producing, circulating, and monitoring cerebrospinal fluid - Oligodendrocytes: myelinate CNS axons; provide structural framework - Microglia: remove cell debris, wastes, and pathogens by phagocytosis

Describe the anatomical difference between white and gray matter

- White matter: regions dominated by myelinated axons; whisks nerve impulses - Gray matter: areas containing neuron cell bodies, dendrites, and unmyelinated axons; great concentration of neuron cell bodies

Which neurotransmitter is released at cholingeric synapses?

- acetylcholine

Dopamine

- inhibitory or excitatory; prevents the overstimulation of neurons; "high"

Which neurotransmitter is affected by SSRI's such as Zoloft, Paxil and Prozac?

- serotonin

Which of the following statements about resting potential is true? It can be altered to produce either depolarization or hyperpolarization. It is stabilized by the activities of the sodium-potassium pump. In a typical neuron, resting potential is approximately −70 millivolts. All of the listed responses are correct.

All of the listed responses are correct.

Which of the following statements about facilitation is FALSE? Facilitation can occur as a result of spatial or temporal summation. Facilitation can occur by exposing a neuron to certain drugs in the extracellular fluid, such as nicotine and caffeine. Facilitation is said to have occurred when a neuron is brought closer to threshold at the initial segment of the axon. All of the listed responses are false; none is true.

All of the listed responses are false; none is true.

Which of the following statements comparing action potentials and graded potentials is INCORRECT? Action potentials show an all-or-none phenomenon, but graded potentials do not. The effect of a graded potential diminishes with increasing distance from the site of stimulation, whereas an action potential's effect is constant with distance traveled. Graded potentials occur only in excitable membranes, whereas action potentials occur in most cell membranes. Spread of a graded potential occurs by passive local current, whereas spread of an action potential occurs by propagation as one depolarized site brings the adjacent site to threshold.

Graded potentials occur only in excitable membranes, whereas action potentials occur in most cell membranes.

CNS neurons cannot be replaced if lost to injury or disease. Why can't they be replaced?

Most neurons lack centrioles, important organelles that help to organize the cytoskeleton and the microtubules that move chromosomes during mitosis. Thus, typical CNS neurons cannot divide; for this reason, they cannot be replaced if lost to injury or disease.

Which of the following statements about motor neurons is true? Motor neurons form the afferent division of the CNS. Motor neurons form the efferent division of the CNS. Motor neurons form the efferent division of the PNS. Proprioceptors are a major category of motor neurons.

Motor neurons form the efferent division of the PNS.

During the initiation of an action potential in an area of excitable membrane, which of the following does NOT occur? Potassium channels open to increase the level of depolarization attained by the membrane. Voltage-regulated sodium ion channels open as threshold is reached. A graded potential raises the transmembrane potential toward threshold. All of the listed events occur during the initiation of an action potential.

Potassium channels open to increase the level of depolarization attained by the membrane.

Which of the following statements about synaptic transmission is INCORRECT? Synaptic delay is greater at synapses of myelinated neurons than at those of unmyelinated neurons. About half the acetylcholine released at a synapse is broken down before it reaches the postsynaptic receptors. Under intense stimulation, a neuron may run out of neurotransmitter and suffer synaptic fatigue. The axon terminal is not totally dependent on the Ach synthesized in the cell body and delivered by axoplasmic transport.

Synaptic delay is greater at synapses of myelinated neurons than at those of unmyelinated neurons.

When you take a pain reliever, which of the following best describes, in general terms, how this affects the threshold of neurons? Taking a pain reliever does not affect the threshold of neurons. Taking a pain reliever increases the threshold. Taking a pain reliever decreases the threshold. Taking a pain reliever affects the all-or-none principle of neurons. So, neurons reaching threshold send an action potential at 50%.

Taking a pain reliever increases the threshold.

Which of the following statements about neural organization is INCORRECT? The somatic nervous system controls voluntary muscle contractions. The sympathetic division is part of the autonomic division. The peripheral nervous system includes the cranial nerves and the spinal nerves. The afferent division is also known as the visceral motor system.

The afferent division is also known as the visceral motor system.

Puffer fish poison blocks voltage-gated sodium channels like a cork. What effect would this neurotoxin have on the function of neurons? The axon would be unable to generate action potentials. Neurons would depolarize more rapidly. Action potentials would lack a repolarization phase. The absolute refractory period would be shorter than normal. None, because the chemically gated sodium channels would still function.

The axon would be unable to generate action potentials.

Which of the following statements about gated channels is INCORRECT? Voltage-regulated channels, such as sodium ion channels, open in response to changes in the transmembrane potential. The binding of ACh on the axon hillock triggers the opening of voltage-gated channels. An ACh receptor on the dendrite of a postsynaptic cell is an example of a chemically gated channel. A firm grasp on the forearm triggers the opening of mechanically gated channels.

The binding of ACh on the axon hillock triggers the opening of voltage-gated channels.

What is the implication of a mature neuron's having no centrioles? The neuron is not able to receive or transmit impulses. The cell is not able to produce proteins. The cell is not able to produce ATP. The cell is not able to divide.

The cell is not able to divide.

Which of the following statements about electrical synapses is FALSE? Connexons allow the passage of ions and thus the passage of current from one cell to another. Presynaptic and postsynaptic membranes are connected at gap junctions. They are located in both the CNS and PNS, in areas such as the brain and eye. The connections between presynaptic and postsynaptic cells allow neurotransmitters such as ACh and dopamine to travel directly from one cell to another.

The connections between presynaptic and postsynaptic cells allow neurotransmitters such as ACh and dopamine to travel directly from one cell to another.

Which of the following statements about graded potentials is INCORRECT? The most affected area is the site of stimulation, and stimulatory effects decrease as distance increases from the point of stimulation. A graded potential could result in a hyperpolarization of the cell membrane, thus moving the area away from threshold. A graded potential could result in depolarization of the cell membrane, thus moving the area toward threshold. The effect of graded depolarization is spread actively as ATP is required to open channels.

The effect of graded depolarization is spread actively as ATP is required to open channels.

Which of the following statements about the nervous system is FALSE? The efferent division of the peripheral nervous system contains sensory and motor neurons. The autonomic nervous system is part of the efferent division of the peripheral nervous system. The sympathetic and parasympathetic divisions of the autonomic nervous system often have antagonistic effects. Most of the neural tissue of the body is located in the brain and spinal cord, which compose the central nervous system.

The efferent division of the peripheral nervous system contains sensory and motor neurons.

Which of the following statements about neural function and information processing is INCORRECT? If the axon hillock remains depolarized for an extended time, a new action potential will be generated as soon as the absolute refractory period of the previous one has ended. Extracellular chemicals other than neurotransmitters and neuromodulators can cause facilitation or inhibition of function in neurons. The rate of action potential generation at a postsynaptic membrane is constant for each particular synapse. When an EPSP or IPSP occurs at an axonal synapse, there can be presynaptic inhibition or presynaptic facilitation of neurotransmitter release from the synaptic knob.

The rate of action potential generation at a postsynaptic membrane is constant for each particular synapse.

Which one of the following statements about the transmembrane potential is correct? Only passive forces are involved in the generation of the transmembrane potential. The cell membrane is freely permeable to all negative ions but selectively permeable to positive ions. The resting negative charge on the interior of the plasma membrane is due mainly to charges on proteins. The main cation of the intracellular fluid is Na+.

The resting negative charge on the interior of the plasma membrane is due mainly to charges on proteins.

Which of the following statements about action potentials and their propagation is INCORRECT? An action potential always moves away from the site of its generation, not back toward it. Each action potential moves few ions compared to the vast number on each side of the cell membrane. The smaller the diameter of an axon, the more rapidly it can conduct an action potential. Because ions cannot cross an axolemma where the membrane is covered with myelin, only the nodes can respond to a depolarizing stimulus.

The smaller the diameter of an axon, the more rapidly it can conduct an action potential.

How does blocking retrograde axoplasmic transport in an axon affect the activity of a neuron? The neuron becomes unable to depolarize when stimulated. The neuron becomes unable to produce action potentials. The neuron becomes unable to produce neurotransmitters. The soma becomes unable to respond to changes in the distal end of the axon. The soma becomes unable to export products to the synaptic terminals.

The soma becomes unable to respond to changes in the distal end of the axon.

Deteriorating changes in the distal segment of an axon as a result of a break between it and the soma is called ________ degeneration. peripheral neural Wallerian central conduction

Wallerian

Continuous propagation (unmyelinated axons):

action potential appears to move across the surface of the membrane in a series of tiny steps; for a second action potential to occur at the same sight, a second stimulus must be applied

Graded potentials __________. are found in many cell types are produced only in response to chemical stimuli are all the same size and shape occur only in nerves and muscles

are found in many cell types

IPSPs (inhibitory postsynaptic potentials) are local hyperpolarizations. block the efflux of calcium ions. increase membrane permeability to sodium ions. are local depolarizations. block the efflux of potassium ions.

are local hyperpolarizations

The largest and most numerous of the glial cells in the central nervous system are the ependymal cells. microglia. astrocytes. oligodendrocytes. satellite cells.

astrocytes

When a person has a stroke, blood leaks into the brain tissue. Which type of neuroglia cells would make structural repairs to the damage? ependymal cells oligodendrocytes satellite cells astrocytes

astrocytes

Relative refractory period

begins when the sodium ion channels regain their normal resting condition, and continues until the membrane potential stabilizes at the resting level. Another action potential can occur during this period if the membrane is sufficiently depolarized (however, requires a larger than normal stimulus).

Which ion triggers synaptic vesicles to discharge neurotransmitter into the synaptic cleft? magnesium calcium sodium potassium

calcium

Saltatory propagation (myelinated axons):

carry action potentials along an axon much more rapidly than does continuous propagation; uses less energy because there is less surface area and fewer sodium ions pumped out of the cytoplasm

Most neurons lack ________ and so are permanently blocked from undergoing cell division. a nucleus ribosomes endoplasmic reticula cytoplasm centrioles

centrioles

The ventricles of the brain and the central canal of the spinal cord are filled with __________. water intracellular fluid normal saline cerebrospinal fluid

cerebrospinal fluid

In order to communicate with multiple cells at the same time, an axon may branch along its length, producing side branches called __________. initial segment collaterals axon terminal telodendria

collaterals

Which of the following is NOT one of the three classes of mechanisms by which neurotransmitters function? compounds that prevent inactivation of neurotransmitter at the synaptic cleft compounds that have an indirect effect on membrane potential by means of second messengers lipid-soluble gases that can diffuse into the cell and bind to enzymes inside the cell compounds that have a direct effect on membrane potential by affecting chemically regulated channels

compounds that prevent inactivation of neurotransmitter at the synaptic cleft

A shift of the resting transmembrane potential toward 0 mV is called potential difference. repolarization. polarization. hyperpolarization. depolarization.

depolarization

Part complete Opening of sodium channels in the axon membrane causes depolarization. inhibition. hyperpolarization. increased negative charge inside the membrane. repolarization.

depolarization

EPSPs (excitatory postsynaptic potentials) occur when extra sodium ions enter a cell. chloride ions enter a cell. hyperpolarizations occur. more calcium ions than usual leak out of a cell. more potassium ions than usual leak out of a cell.

extra sodium ions enter a cell

Part complete Damage to ependymal cells would most likely affect the formation of ganglia. formation of myelin sheaths. transport of neurotransmitters within axons. repair of axons. formation of cerebrospinal fluid.

formation of cerebrospinal fluid

In the peripheral nervous system, Schwann cells participate in the repair of damaged nerves by forming a cellular cord that directs axonal regrowth. clearing away cellular debris. producing more satellite cells that fuse to form new axons. regenerating cell bodies for the neurons. producing new axons.

forming a cellular cord that directs axonal regrowth

Absolute refractory period

from the moment the voltage-gated sodium ion channels open at threshold until sodium ion channel inactivation ends, the membrane cannot respond to further stimulation because all the voltage-gated sodium ion channels are either already open or inactivated (lasts .4-1 msec)

The refractory period occurs __________. when the cell is depolarizing from the time an action potential begins until the normal resting potential has stabilized during the time between the stimulus and the response when the cell is hypersensitive to stimuli

from the time an action potential begins until the normal resting potential has stabilized

Which of the following is the most important excitatory neurotransmitter in the brain that is important in learning and memory? gamma aminobutyric acid serotonin glutamate noradrenaline glycine

gluatmate

Saltatory transmission __________. occurs in myelinated neurons occurs at the nodes of Ranvier is faster than continuous propagation has all of the listed characteristics

has all of the listed characteristics

Serotonin

inadequate serotonin produces decreased attention and emotional state, may be responsible for severe chronic depression

A stimulus causes a neuron's membrane potential to rise to −60 mV. Which of the following is NOT going to occur? opening of sodium channels action potential inhibition of action potential due to hyperpolarization depolarization

inhibition of action potential due to hyperpolarization

List 3 types of sensory receptors.

interoceptors, exteroceptors, and proprioceptors

Presynaptic facilitation __________. is activity at an axoaxonal synapse that increases the amount of neurotransmitter released when an action potential arrives at the synaptic terminal is the release of an inhibitory neurotransmitter at an axoaxonal junction that limits the release of neurotransmitter when an action potential arrives at the synaptic terminal does not incorporate the use of serotonin can be caused by preventing calcium channels from opening at the synaptic terminal

is activity at an axoaxonal synapse that increases the amount of neurotransmitter released when an action potential arrives at the synaptic terminal

Which type of ion channel is always open? voltage-gated leak mechanically-gated chemically-gated

leak

________ account for roughly half of the volume of the nervous system. Axons Neuroglia Efferent fibers Dendrites Synapses

neuroglia

Which of these neurotransmitters does NOT bind to a plasma membrane receptor? serotonin nitric oxide GABA norepinephrine

nitric oxide

The tiny gaps between adjacent Schwann cells are called axolemma. nodes of Ranvier. terminals. vesicles. neurillema.

nodes of Ranvier

The myelin sheath that covers many CNS axons is formed by oligodendrocytes. astrocytes. ependymal cells. satellite cells. microglia.

oligodendrocytes

Multipolar neurons have __________. one axon and several dendrites no axons and several dendrites several axons and one dendrite one axon and one dendrite

one axon and several dendrites

What type of sensory neurons would Amy, a gymnast, use to inform her brain of the position of her skeletal muscles and joints? proprioceptors exteroceptors interoceptors None of the listed responses is correct.

proprioceptors

Gated channels may be __________. mechanically regulated chemically regulated voltage regulated regulated in any of the listed ways

regulated in any of the listed ways

The movement of substances from the synaptic terminal to the soma is called __________. bulk flow anterograde flow synaptic fatigue retrograde flow

retrograde flow

Rapid impulse conduction from "node" to "node" is called divergent propagation. synaptic transmission. spatial propagation. continuous propagation. saltatory propagation.

saltatory propagation.

Which of the following glial cells surround cell bodies in the PNS and regulate levels of oxygen and carbon dioxide around ganglionic neurons? astrocytes ependymal cells satellite cells microglia

satellite cells

Which neurotransmitter has widespread effects on a person's attention and emotional state? dopamine norepinephrine serotonin GABA endorphins

serotonin

Summation that results from the cumulative effect of multiple synapses at multiple places on the neuron is designated spatial summation. inhibition of the impulse. temporal summation. hyperpolarization. impulse transmission.

spatial summation

The site of intercellular communication between a neuron and another cell is the axolemma. synapse. telodendria. hillock. collateral. Submit

synapse

Axons terminate in a series of fine extensions known as collaterals. dendrites. terminals. telodendria. synapses.

telodendria

The speed at which an action potential is transmitted depends on __________. the strength of the stimulus the length of the axon the myelination and diameter of the axon the weather

the myelination and diameter of the axon

Which of the following does NOT describe a synapse? the point at which neurotransmitters are released into the synaptic cleft the point where neurotransmitters are assembled a place where the axon of a neuron and a muscle cell may interact the point where the axon of one neuron interacts with the dendrite or cell body of another axon

the point where neurotransmitters are assembled

A neuron that receives neurotransmitter from another neuron is called the postsynaptic neuron. the presynaptic neuron. an oligodendrocyte. the motor neuron. a satellite cell.

the postsynaptic neuron.

Repolarization

the process of restoring the normal resting membrane potential after depolarization

The transmembrane potential found in all living cells is maintained by __________. gamma amino butyric acid the sodium-potassium pump acetylcholine Schwann cells

the sodium-potassium pump