ch 11 The Nervous System

Which membrane potential opens a sufficient number of the voltage-gated Na+ channels to cause a significant change in the membrane potential (making it much less negative).

-60 mV The membrane potential at which sufficient voltage-gated Na+ channels open is -60 mV.

A neuron has a resting potential of about _____ millivolts.

-70 This is the resting potential, the charge difference found across the plasma membrane of a "resting" neuron.

What is the value for the resting membrane potential for most neurons?

-70 mV the resting membrane potential for neurons depends on the distribution of both Na+ and K+ across the cell membrane. The potential is closer to the equilibrium potential of K+ because the cell is more permeable to K+.

What is the resting membrane potential of the neuron used in the experiment?

-80 mV The resting membrane potential for this neuron is the line, or portion of the line, at which there is no observable activity. For this particular neuron, we see this occurs right at -80 mV.

The sentences below describe a neuron at resting potential. Drag the terms on the left to the appropriate blanks to complete the sentences.

1. Using energy from ATP,sodium-potassium pumpsactively transport ions in both directions across the membrane. 2. Some potassium channelsare open, allowing certain ions to move out of the cell through them. 3. The sodium channels are closed, preventing certain ions from entering the cell through them. 4. The concentration of sodium ionsis higher outside the cell than inside. 5. The concentration of potassium ionsis higher inside the cell than outside.

What is the magnitude (amplitude) of an action potential?

100 mV the membrane goes from -70 mV to +30 mV. Thus, during the action potential, the inside of the cell becomes more positive than the outside of the cell.

Open the site in your browser and play the podcast. Think about whether you believe the information presented or whether you have doubts about some of it.

2-4 (somewhat trustworthy; want to check some things) Your answer represents your first impression of the trustworthiness of this source. Now you will answer some specific questions and reevaluate this score at the end.

What is the difference between a reflex and a reflex arc?

A reflex is an automatic response; a reflex arc is the neural circuitry. A reflex is any automatic nervous system response to a stimulus. The neurons making up the electrical circuit comprise the reflex arc.

Which of the following statements correctly characterizes an action potential?

Action potentials are initiated by depolarization of the membrane to threshold.

Based on current research, which of the following is most likely?

An increased amount of time using digital media causes an increased risk of developing depression and ADHD symptoms in teenagers.

How is an action potential propagated along an axon?

An influx of sodium ions from the current action potential depolarizes the adjacent area. the influx of sodium ions depolarizes adjacent areas, causing the membrane to reach threshold and cause an action potential. Thus, the action potential is regenerated at each new area.

The United States attorney's office in Massachusetts charged 14 people with crimes associated with the outbreak. Who ultimately will be held responsible for the unfortunate victims in crimes of second-degree murder?

An owner of the company and the company's head pharmacist.

Why are many muscles at the effector end of the reflex arc found in antagonistic pairs?

Antagonistic muscles have opposite actions. This is often needed for a reflex. In one reflex, one muscle must contract and another muscle must relax so that the reflex action can be complete. In another reflex, the muscle that was relaxed may now need to contract and the one that contracted in the first reflex must now relax.

Which of the following statements regarding infections of the nervous system is accurate?

Bacterial meningitis is generally more severe than viral meningitis.

What occurs when the action potential reaches the synaptic terminal?

Calcium ions rush into the presynaptic terminal. Calcium ions rush into the presynaptic terminal.

Which part of the brain is associated with conscious thought, memory, and personality?

Cerebral cortex The cerebrum is the largest of the four regions of the brain and is associated with the "higher functions" such as memory, language, thought, and personality.

At the time of the fungal meningitis outbreak that killed 64 people in nine states, what organization regulated the companies the created these injectable steroid compounds?

Compounding pharmacies were regulated by state boards of pharmacy.

Drag and drop each of the terms at the left to the correct statement at the right.

Depolarization: Sodium ions are moving in, and the membrane potential is becoming less negative than the resting membrane potential. Repolarization: Potassium ions are moving out, and the membrane potential is becoming more negative as it moves back toward the resting membrane potential. Hyperpolarization: Potassium ions are moving out, and the membrane potential is becoming more negative than the resting membrane potential.

True or false. An individual who has suffered a stroke, which has caused damage in his cerebrum, and is now having problems with his hearing, has probably suffered damage to his occipital lobe.

False The occipital lobe processes visual information from the eyes; the temporal lobe is involved in processing auditory information.

Your friend exhibits symptoms of ADHD. Which of the following is true?

He may or may not be diagnosed with ADHD.

Consider the neurotransmitters norepinephrine and acetylcholine. Which statement is generally true?

In general, the neurotransmitter of the sympathetic nervous system is norepinephrine, and the neurotransmitter of the parasympathetic nervous system is acetylcholine. Correct. Norepinephrine is the neurotransmitter of the sympathetic nervous system, and acetylcholine is the neurotransmitter of the parasympathetic nervous system

Which of the following is true of the peripheral nervous system (PNS)?

It includes a sensory division and a motor division.

Which of the following is NOT an important function of the myelin sheath around axons?

It prevents saltatory conduction in the neuron. Myelin sheaths promote saltatory conduction, which speeds the propagation of impulses. The myelin sheath causes action potentials to jump from node to node, which speeds the transmission of impulses.

Which statement accurately describes the myelin sheath?

It speeds up the conduction of nervous impulses. A myelin sheath speeds up conduction of nervous impulses by allowing saltatory conduction.

The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.

K+; Na+ more K+ moves out of the cell than Na+ moves into the cell, helping to establish a negative resting membrane potential.

Match the words in the left column to the appropriate phrases on the right. Make certain each word is matched with a phrase before submitting your answer.

Membrane potential of −70 mV Membrane potential of − 70 m V : The resting membrane potential of the cell : The resting membrane potential of the cell Membrane potential of −90 mV Membrane potential of − 90 m V : The point at which there is no net movement of K + into or out of the cell : The point at which there is no net movement of K+ into or out of the cell K+ permeability K + permeability: The primary determinant of the resting membrane potential : The primary determinant of the resting membrane potential Na+ permeability N a + permeability: Although it plays a role, it is not a primary determinant of the resting membrane potential : Although it plays a role, it is not a primary determinant of the resting membrane potential

The concentrations of which two ions are highest outside the cell.

Na+ and Cl- both Na+ and Cl- are in higher concentrations outside the cell.

The concentrations of which two ions are highest outside the cell?

Na+ and Cl−

The Na+-K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?

Na+ is pumped out of the cell and K+ is pumped into the cell. Na+ is pumped out of the cell against its electrochemical gradient and K+ is pumped into the cell against its concentration gradient.

Arrange the following events in the correct order, from left to right, with respect to the function of the channels, ion permeability, and changes in membrane potential.

Opening of voltage-gated Na+ channels Opening of voltage-gated N a Superscript+ channels Na+ ion flow into the neuron increases N a Superscript+ ion flow into the neuron increases Depolarization of the membrane to +30 mV Depolarization of the membrane to +30 m V K+ ion flow out of the neuron increases K Superscript+ ion flow out of the neuron increases Repolarization of the membrane

What does saltatory conduction mean?

Saltatory conduction means that the nerve impulse seems to jump from one node to the next—and is regenerated as it speeds along.

When speaking of myelinating glial cells, we can correctly say that ________.

Saltatory conduction means that the nerve impulse seems to jump from one node to the next—and is regenerated as it speeds along. Saltatory conduction does mean that the impulse jumps.

What type of cell makes up the myelin sheath of a motor neuron?

Schwann cells Myelin sheaths are formed when Schwann cells wrap around the axons of motor neurons.

You are a mental health specialist looking to expand on this research. Which of the following would be best for you to study?

Separate out the different types of digital media.

Which of the following events is the first to occur during an action potential?

Sodium channels open. Sodium channels open at the start of an action potential.

In this experiment, which stimulus causes the membrane potential to reach the threshold value?

Stimulus 3 Threshold is achieved when a neuron is stimulated strongly enough to trigger an action potential.

Which of the following statements is true about the interaction of sympathetic and parasympathetic nerve fibers?

Sympathetic and parasympathetic nerve fibers may innervate the same organs, but they have generally opposite effects. Sympathetic and parasympathetic nerve fibers usually have antagonistic effects on the same organ.

This study indicated which of the following?

Teens who use excessive amounts of digital media have an increased chance of exhibiting symptoms of ADHD

Which part of the brain functions as a relay station for information to the limbic system and the cerebral cortex?

Thalamus The thalamus is a processing center that relays sensory information from the body to the limbic system and cerebral cortex.

Why does the action potential only move away from the cell body?

The areas that have had the action potential are refractory to a new action potential. Yes, sodium channels are inactivated in the area that just had the action potential.

What causes an action potential to be conducted along a neuron's axon?

The change in charge difference across the membrane spreads from open sodium channels, causing sodium channels farther along the axon to open. As the change in charge difference across the membrane spreads from open sodium channels, the sodium channels farther along the axon open, starting an action potential farther along the axon.

When the neurotransmitter crosses the synapse, what happens?

The neurotransmitter causes the channel to open, and this can cause a depolarization of the postsynaptic membrane. The neurotransmitters bind to the postsynaptic ion channels, causing them to open. If the synapse is excitatory, the postsynaptic membrane will depolarize

Which of the following characteristics of the neuron cell membrane contributes to the maintenance of the resting membrane potential?

The sodium-potassium pump transports three sodium ions out of the cell for every two potassium ions it pumps into the cell. This movement of ions helps to maintain the resting membrane potential

Which statement most accurately describes the relative physical position of the ganglia of the sympathetic and parasympathetic nervous systems?

The sympathetic ganglia are located in chain-like fashion near the spinal cord. The parasympathetic ganglia are located closer to their target organs. Correct. The sympathetic ganglia are located in chain-like fashion near the spinal cord. The parasympathetic ganglia are located closer to their target organs.

Think of the heart in the tutorial. Now, picture yourself being chased by a herd of wild elephants. What are the sympathetic and parasympathetic actions on your heart?

The sympathetic nervous system will cause the heart rate to speed up. The parasympathetic nervous system will be "overridden." The sympathetic nervous system is active in crisis situations. The parasympathetic nervous system is overruled by the sympathetic response.

Which of these statements best describes a synapse?

The synapse includes the space between the presynaptic membrane and the postsynaptic membrane. The synapse includes the presynaptic membrane, the postsynaptic membrane, and the space between them.

Which of the following is true regarding psychoactive drugs?

They affect the release, action, or reuptake of neurotransmitters in some way. They affect the release, action, or reuptake of neurotransmitters in some way.

Which of the following is characteristic of psychoactive drugs?

They alter levels of neurotransmitters.

What do multiple sclerosis and ALS (amyotropic lateral sclerosis) have in common?

They both damage the myelin sheath, slowing action potential transmission.

Which of the following is NOT a method for clearing neurotransmitters from a synapse?

They can be taken up into the postsynaptic neuron. Neurotransmitters are not taken up by the postsynaptic neuron.

You spend a lot of time using social media on a daily basis. This research indicates which of the following?

Your sleep may be disturbed.

How can you know if the person or organization providing the information has the credentials and knowledge to speak on this topic? One clue is the type of web site it is--the domain name ".gov" tells you that this is a government web site.

a researcher from the National Centers for Disease Control and Prevention The researcher's name is Dr. Chris Taylor, so he is either an M.D. or a Ph.D., or possibly both. What does this indicate about his expertise on the subject of brain injuries? Another thing to look for is how recently the information on the site was posted or updated. A well maintained, authoritative web site should be updated or reviewed often.

The velocity of the action potential is fastest in which of the following axons?

a small myelinated axon the myelination acts as insulation and the action potential is generated only at the nodes of Ranvier. Propagation along myelinated axons is known as saltatory conduction.

The mechanism by which the neurotransmitter is returned to a presynaptic neuron's axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?

acetylcholine acetylcholine is broken down by acetylcholinesterase before being returned to the presynaptic neuron's axon terminal.

Which of these causes the release of neurotransmitter molecules?

an action potential reaching the end of the axon. When an action potential reaches the end of an axon, vesicles fuse with the plasma membrane and release neurotransmitter into the synaptic cleft.

During an action potential, when does sodium ion permeability begin to significantly decline?

at the peak of depolarization

An action potential moves along a(n) _____.

axon An axon is the only portion of a neuron capable of generating an action potential.

Where in the neuron is an action potential initially generated?

axon hillock this region (first part of the axon) receives local signals (graded potentials) from the soma and dendrites and has a high concentration of voltage-gated Na+ channels.

The part of the nerve cell responsible for origination of the nerve impulse is the ________.

axon hillock, because this is the specific area of the nerve cell that generates the electrical impulse that travels along the axon The axon hillock is the part that generates the electrical impulse.

Name the three principal parts of the nerve cell.

axon, dendrites, cell body The three principal parts are the cell body, the axon, and the dendrites.

A nerve impulse moves away from a neuron's cell body along _____.

axons Axons conduct a nerve impulse away from the cell body

An __________ neurotransmitter causes __________ of the postsynaptic membrane.

both excitatory; depolarization and inhibitory; hyperpolarization are correct

During depolarization, which gradient(s) move(s) Na+ into the cell?

both the electrical and chemical gradients. a positive ion is driven into the cell because the inside of the cell is negative compared to the outside of the cell, and Na+ is driven into the cell because the concentration of Na+ is greater outside the cell.

Which of the following influence(s) the speed of an action potential?

both the presence of a myelin sheath and the diameter of the axon

A neuron's nucleus is located in its _____.

cell body The cell body is the region of a neuron where the nucleus is found.

The brain and spinal cord make up the __________.

central nervous system

The coordination necessary for a musician to play the piano depends on control exerted by the __________.

cerebellum

Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.

chemically gated; postsynaptic the neurotransmitter is a chemical released from the presynaptic membrane, so it would open chemically gated channels on the postsynaptic membrane.

A nerve impulse moves toward a neuron's cell body along _____.

dendrites Dendrites conduct an impulse from a synapse toward the cell body. Oligodendrocytes, also known as Schwann cells, produce the myelin sheath.

With the exception of sensory neurons, the role of a neuron's __________ is to carry information toward the cell body, whereas the role of the __________ is to carry information away from the cell body.

dendrites; axon The dendrites receive information and the axon transmits information.

Binding of the neurotransmitter to its receptor causes the membrane to __________.

either depolarize or hyperpolarize the neurotransmitter can cause the postsynaptic membrane to either depolarize or hyperpolarize, depending on which ion channels are opened.

Which set of words can correctly be used to describe interneurons?

excitatory and inhibitory Excitatory and inhibitory describe interneurons. These are functional descriptions.

Which of the following would occur in a neuron if calcium could NOT enter the axon bulb?

inability to release neurotransmitters Calcium is required in the axon bulb for the release of neurotransmitters.

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,

ion channels in the plasma membrane of the receiving neuron open.

An action potential __________.

is self-propagating An action potential is self-propagating because its depolarization of the membrane brings the next region of the axon to threshold.

Which part of the brain is responsible for regulating the heart and respiratory rates and blood pressure?

medulla oblongata

Axons insulated by a(n) _____ are able to conduct impulses faster that those not so insulated.

myelin sheath Myelin sheaths, formed when Schwann cells wrap around an axon, allow such neurons to conduct impulses more rapidly than unmyelinated axons.

White matter of the spinal cord contains __________, whereas gray matter contains __________.

myelinated nerves; unmyelinated cell bodies Myelin gives nerves a white appearance, whereas unmyelinated nerves appear gray, thus the names white and gray matter.

Which of the following cell types makes up the majority of cells in the nervous system?

neuroglial cells

A molecule that carries information across a synaptic cleft is a

neurotransmitter. Neurotransmitter molecules carry information across a synaptic cleft.

An impulse relayed along a myelinated axon "jumps" from _____ to _____.

node of Ranvier ... node of Ranvier In myelinated neurons the impulse jumps from node of Ranvier to node of Ranvier.

Graded potentials __________.

occur in a local area of the membrane

The transmission of a nerve impulse first triggers the _____.

opening of voltage-gated sodium channels and the diffusion of sodium ions into the neuron

Let's consider a scenario in which the resting membrane potential changes from −70 mV to +70 mV, but the concentrations of all ions in the intracellular and extracellular fluids are unchanged. Predict how this change in membrane potential affects the movement of Na+. The electrical gradient for Na+ would tend to move Na+ __________ while the chemical gradient for Na+ would tend to move Na+ __________.

out; in If the inside of the cell is positively charged compared to the outside, the electrical gradient will favor movement of positively charged sodium ions out of the cell.

Parkinson's disease primarily affects __________.

physical ability Parkinson's disease affects the coordination of muscle movement.

In a synapse, neurotransmitters are stored in vesicles located in the __________.

presynaptic neuron neurotransmitters are stored in the axon terminals of the presynaptic neuron.

Which of the following is the correct sequence for the electrical transmission of a nerve impulse?

presynaptic neuron, synapse, postsynaptic neuron The impulse comes from the presynaptic neuron, crosses the synapse, and stimulates the postsynaptic neuron.

Sodium-potassium pumps

restore the distribution of ions inside and outside a neuron's membrane following an action potential. Following an action potential, sodium-potassium pumps restore the distribution of ions back to their levels at resting potential.

You touch a hot stove and your hand quickly jerks away. What is the path of the nerve impulses that are responsible for this reflex?

sensory neuron to interneuron to motor neuron. A sensory neuron receives information from a sensory receptor and passes it along through an interneuron to a motor neuron, which sends a message to the effectors (muscles) that must respond.

Neurons of the PNS that transmit information to the CNS are __________.

sensory neurons Sensory neurons carry information from the body to the CNS.

Which component of a reflex arc carries information to the central nervous system?

sensory neurons Sensory neurons respond to signals from receptors in both the internal and external environments. The sensory neurons then carry the message to the spinal cord.

Information coming into the central nervous system arrives via __________, while information going from the central nervous system to the muscles, glands, and organs travels via __________.

sensory neurons; motor neurons

Hyperpolarization results from __________.

slow closing of voltage-gated K+ channels the slow closing of the voltage-gated K+ channels means that more K+ is leaving the cell, making it more negative inside.

A stimulus has opened the voltage-gated sodium channels in an area of a neuron's plasma membrane. As a result, _____ rushes into the neuron and diffuses to adjacent areas; this in turn results in the _____ in the adjacent areas.

sodium ... opening of voltage-gated sodium channels This describes part of the process by which an action potential travels along an axon.

If your heart rate and blood pressure increase in response to a crisis, you are experiencing the immediate effects of the __________ nervous system (NS).

sympathetic The sympathetic NS will trigger an increase in heart rate and blood pressure during a crisis.

Which of the following would cause an acceleration of heart rate, an increase in blood pressure, and a slowing of digestive processes?

sympathetic division of the autonomic nervous system

The space between an axon of one neuron and the dendrite of another neuron is called a(n) _____.

synaptic cleft "Synaptic cleft" is the name given to the space between two neurons that meet at a synapse.

The small space between the sending neuron and the receiving neuron is the

synaptic cleft. The synaptic cleft is the small space between the sending neuron and the receiving neuron.

What part of a neuron relays signals from one neuron to another neuron or to an effector?

synaptic terminal Synaptic terminals contain neurotransmitter molecules that relay the nerve impulse across a synapse.

Neurons store neurotransmitter molecules in vesicles located within _____.

synaptic terminals Vesicles within synaptic terminals contain neurotransmitter that may be released into the synaptic cleft.

A spinal reflex requires the participation of each of the following, EXCEPT __________.

the cerebral cortex

During an action potential

the inside of the neuron becomes positively charged relative to the outside. The inside of a neuron becomes positively charged relative to the outside during an action potential.

All of the following are associated with storage of long-term memory, EXCEPT __________.

the limbic system

The repolarization phase of an action potential results from __________.

the opening of voltage-gated K+ channels Yes, as the voltage-gated K+ channels open, K+ rushes out of the cell, causing the membrane potential to become more negative on the inside, thus repolarizing the cell.

When discussing the origins of the sympathetic and parasympathetic divisions of the autonomic nervous system, we can most correctly state that ________.

the parasympathetic nerves arise from the brain and part of the spinal cord, and all of the sympathetic nerves arise from the spinal cord. Nerves of the parasympathetic division emerge from the brain stem (cranial nerves) and the sacral segment of the spinal cord; all of the sympathetic nerves emerge from the thoracic and lumbar spinal cord.

If a signal from a sending neuron makes the receiving neuron more negative inside,

the receiving neuron is less likely to generate an action potential. If the receiving neuron is more negative inside, it is less likely to generate an action potential.

During an action potential, the rapid decrease in sodium ion permeability and the simultaneous and rapid increase in potassium ion permeability is responsible for __________.

the repolarization phase The repolarization phase of the action potential occurs just after the action potential peaks. Repolarization is caused by two simultaneous events: 1) a rapid decrease in sodium permeability as the inactivation gates of voltage-gated Na+ channels close and 2) an increase in potassium permeability as the activation gates of voltage-gated K+ channels open. With less Na+ entering the cell and more K+ leaving, the membrane potential returns to a negative value.

At rest, which of these plays a role in establishing the charge differential across a neuron's plasma membrane?

the sodium-potassium pump moving sodium ions out of the neuron and potassium ions into the neuron The sodium-potassium pump moves more sodium ions out of the cell than potassium ions into the cell; this net loss of positive ions establishes a charge differential across the plasma membrane.

If a neurotransmitter is known to have either excitatory or inhibitory effects, what is the most likely factor that determines which effect this neurotransmitter will have at a postsynaptic membrane?

the type of receptor to which the neurotransmitter binds in the postsynaptic membrane. Some neurotransmitters may be excitatory or inhibitory depending on the type of receptor that they bind to on the postsynaptic membrane.

Current nervous system research includes exploring which of the following to treat spinal cord injuries?

the use of stem cells to replace damaged cells The use of stem cells is a promising area of research in the treatment of spinal cord injuries.

When a neuron is at its resting potential

there are more potassium ions inside the neuron than outside. Sodium-potassium pumps actively transport sodium ions out of the cell and potassium ions into the cell. The result is that the neuron has more potassium ions and fewer sodium ions inside the cell.

When calcium ions enter the synaptic terminal,

they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

Next, can you identify what the source is trying to accomplish by providing this information? As you listen to the podcast, think about what the doctor's agenda might be with regard to head injuries.

to inform the public about brain injuries

An action potential releases neurotransmitter from a neuron by opening which of the following channels?

voltage-gated Ca2+ channels opening of these channels causes calcium to move into the axon terminal. Calcium inside the neuron causes the vesicles to merge with the membrane and release the neurotransmitter via exocytosis into the synaptic cleft.

The depolarization phase of an action potential results from the opening of which channels?

voltage-gated Na+ channels Yes, when the voltage-gated Na+ channels open, Na+ rushes into the cell causing depolarization.

All of the following are directly involved in synaptic transmission, EXCEPT __________.

voltage-sensitive ion channels on the postsynaptic membrane

Long-term memory occurs __________.

when neurons are permanently changed During the formation of long-term memory, neurons undergo permanent chemical or physical changes.