Chapter 12

Compared to type A axons, type C axons are __________.

The neurotransmitter glutamate opens channels that are permeable to sodium ions. What effect does glutamate produce on a postsynaptic neuron?

The ________ nervous system is composed of the brain and spinal cord.

The ________ nervous system controls the skeletal muscles.

The part of the peripheral nervous system that carries sensory information to the CNS is designated

The efferent division of the peripheral nervous system innervates ________ cells.

The nervous tissue outside of the central nervous system composes the ________ nervous system.

The ________ division of the peripheral nervous system brings sensory information to the central nervous system.

The ________ division of the nervous system carries motor commands to muscles and glands.

The ________ nervous system provides involuntary regulation of smooth muscle, cardiac muscle, and glandular activity.

________ carry motor information to peripheral effectors.

________ nerves are nerves that connect to the spinal cord

________ nerves are nerves that connect to the brain.

The afferent division of the PNS __________.

Which division of the PNS would contain sensory nerve fibers from special sensory receptors?

The axon hillock is a region between what two general regions of a neuron?

The axoplasm of the axon contains which of the following?

Which of the following is not a recognized structural classification for neurons?

The most abundant class of neuron in the central nervous system is

The cytoplasm that surrounds the nucleus of a neuron is called the

Clusters of RER and free ribosomes in neurons are called

The axon is connected to the soma at the

Branches that may occur along an axon are called

Axons terminate in a series of fine extensions known as

The site of intercellular communication between a neuron and another cell is the

Neurons that are rare, small, and lack features that distinguish dendrites from axons are called

Neurons in which dendritic and axonal processes are continuous and the soma lies off to one side are called

Neurons that have one axon and one dendrite, with the soma in between, are called

Neurons that have several dendrites and a single axon are called

Sensory neurons of the PNS are

________ are the most numerous type of neuron in the CNS.

________ monitor the position of skeletal muscles and joints.

________ carry sensory information to the CNS.

________ provide information about the external environment.

________ monitor the digestive, respiratory, cardiovascular, urinary, and reproductive systems.

The plasma membrane of an axon is called the

The basic functional unit of the nervous system is the

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

Most CNS neurons fall into which structural category?

Which neuroglia myelinate CNS axons and which neuroglia myelinate PNS axons?

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

Which of the following is not a function of the neuroglia?

Which of the following is a type of glial cell found in the peripheral nervous system?

The largest and most numerous of the glial cells in the central nervous system are the

Functions of astrocytes include all of the following except

The neuroglial cells that participate in maintaining the blood-brain barrier are the

The myelin sheath that covers many CNS axons is formed by

________ line the brain ventricles and spinal canal.

Small, wandering cells that engulf cell debris and pathogens in the CNS are called

The neurilemma of axons in the peripheral nervous system is formed by

Glial cells that surround the neurons in ganglia are

Damage to ependymal cells would most likely affect the

The tiny gaps between adjacent Schwann cells are called

In the peripheral nervous system, Schwann cells participate in the repair of damaged nerves by

Which of the following is not a function of astrocytes?

Neuroglia perform all of these functions EXCEPT __________.

Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?

The plasma membrane is much more permeable to K+ than to Na+. Why?

The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors.

What prevents the Na+ and K+ gradients from dissipating?

Which of the following is not true regarding the establishment of a neuron's resting membrane potential?

At the normal resting membrane potential of a typical neuron, its sodium-potassium exchange pump transports

Ion channels that are always open are called ________ channels.

Opening of sodium channels in the axon membrane causes

Voltage-gated channels are present

The sodium-potassium ion exchange pump

________ open or close in response to binding specific molecules.

________ channels open or close in response to physical distortion of the membrane surface.

Any stimulus that opens a ________ ion channel will produce a graded potential.

If the permeability of a resting axon to sodium ion increases,

Which of the following is not involved in creating the resting membrane potential of a neuron?

If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur except

Graded potentials

When potassium channels open and the ions diffuse through the membrane,

Ions can move across the plasma membrane in which of the following ways?

Voltage-gated sodium channels have both an activation gate and a(n) ________ gate.

Raising the potassium ion concentration in the extracellular fluid surrounding a nerve cell will have what effect?

If acetylcholine (ACh) causes inhibition of a postsynaptic neuron, to what type of membrane channel did the ACh bind?

A movement of charges in response to a potential difference is called

The sum of the electrical and chemical forces acting on an ion is known as its

A shift of the resting transmembrane potential toward 0 mV is called

The equilibrium potential of potassium is

The equilibrium potential of sodium is

The sodium-potassium exchange pump stabilizes resting potential of the neuron membrane at about __________.

The most abundant intracellular cation is __________, while the most abundant extracellular anion is __________.

Which type of ion channel is always open?

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

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+ __________.

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

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

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

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?

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

In a neuron, sodium and potassium concentrations are maintained by the sodium-potassium exchange pump such that __________.

The sodium-potassium exchange pump transports potassium and sodium ions in which direction(s)?

Leak channels allow the movement of potassium and sodium ions by what type of membrane transport?

The electrochemical gradient for potassium ions when the transmembrane potential is at the resting potential (-70 mV) is caused by what?

What is the electrochemical gradient of an ion?

In a typical neuron, what is the equilibrium potential for potassium?

The electrochemical gradient for sodium ions in a neuron when the transmembrane potential is at the resting potential is caused by what?

Compared to the electrical gradient for sodium at rest, the electrical gradient for potassium at rest is __________.

In a typical neuron, what is the equilibrium potential for sodium?

At rest, why is the transmembrane potential of a neuron (-70 mV) closer to the potassium equilibrium potential (-90 mV) than it is to the sodium equilibrium potential (+66 mV)?

Where do most action potentials originate?

What opens first in response to a threshold stimulus?

What characterizes depolarization, the first phase of the action potential?

What characterizes repolarization, the second phase of the action potential?

What event triggers the generation of an action potential?

What is the first change to occur in response to a threshold stimulus?

What type of conduction takes place in unmyelinated axons?

An action potential is self-regenerating because __________.

Why does regeneration of the action potential occur in one direction, rather than in two directions?

What is the function of the myelin sheath?

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?

In which type of axon will velocity of action potential conduction be the fastest?

The all-or-none principle states that

The following are the main steps in the generation of an action potential. 1. Sodium channels are inactivated. 2. Voltage-gated potassium channels open and potassium moves out of the cell, initiating repolarization. 3. Sodium channels regain their normal properties. 4. A graded depolarization brings an area of an excitable membrane to threshold. 5. A temporary hyperpolarization occurs. 6. Sodium channel activation occurs. 7. Sodium ions enter the cell and depolarization occurs. What is the proper sequence of these events?

Which of the following statements about the action potential is false?

How would the absolute refractory period be affected if voltage-regulated sodium channels failed to inactivate?

During repolarization of a neuron

A threshold stimulus is the

How would a chemical that prevents the opening of voltage-regulated Na+ channels affect the function of a neuron?

Which of the following is true about threshold for an action potential?

Rapid impulse conduction from "node" to "node" is called

Which of the following does not influence the time necessary for a nerve impulse to be transmitted?

Which of the following types of nerve fiber possesses the fastest speed of impulse propagation?

Type ________ fibers have the largest diameter axons.

Sensory information from skeletal muscles travels over ________ fibers.

In which of the following would the rate of impulse conduction be the greatest?

The minimum stimulus required to trigger an action potential is known as the

The ________ principle states that the size and speed of the action potential are independent of the stimulus strength.

The period during which an excitable membrane cannot respond to further stimulation is the ________ period.

The period during which an excitable membrane can respond again, but only if the stimulus is greater than the threshold stimulus, is the ________ period.

The presence of ________ dramatically increases the speed at which an action potential moves along an axon.

Below are the events that occur during continuous propagation of action potential. Select the correct order in which the events occur. 1. Adjacent membrane segment depolarizes. 2. Local current spreads to adjacent voltage gated channel. 3. Threshold is met. 4. Local current develops due to sodium moving in the cytosol.

What happens just after an axon is depolarized to threshold?

During propagation of the action potential, __________.

During the action potential, when does sodium permeability initially DECREASE?

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

Where in the neuron is an action potential initially generated?

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

The repolarization phase of an action potential results from __________.

Hyperpolarization results from __________.

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

How is an action potential propagated along an axon?

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

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

Where on the neuron is the action potential initiated?

Which of the following channels is most directly responsible for the properties of the axon that lead to action potential generation?

Which answer best describes the relative refractory period in the neuron?

During an action potential of a neuron, what directly causes the different channels to open and close?

What is the typical duration of a nerve action potential?

Around what transmembrane potential does threshold commonly occur?

What ion is responsible for the depolarization of the neuron during an action potential?

What type of membrane transport causes the depolarization phase of the action potential in neurons?

During an action potential, after the membrane potential reaches +30 mV, which event(s) primarily affect(s) the membrane potential?

What ion causes repolarization of the neuron during an action potential?

What causes repolarization of the membrane potential during the action potential of a neuron?

What is primarily responsible for the brief hyperpolarization near the end of the action potential?

Where are action potentials regenerated as they propagate along an unmyelinated axon?

The movement of what ion is responsible for the local currents that depolarize other regions of the axon to threshold?

In an unmyelinated axon, why doesn't the action potential suddenly "double back" and start propagating in the opposite direction?

Approximately how fast do action potentials propagate in unmyelinated axons in humans?

In contrast to the internodes of a myelinated axon, the nodes __________.

Where are action potentials regenerated as they propagate along a myelinated axon?

The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________.

How do action potential propagation speeds in myelinated and unmyelinated axons compare?

Multiple sclerosis (MS) is a disease that stops action potential propagation by destroying the myelin around (normally) myelinated axons. Which of the following best describes how MS stops action potential propagation?

Which part of an acetylcholine (ACh) molecule undergoes reuptake by the axon terminal to be reused in another acetylcholine molecule?

A neuron that receives neurotransmitter from another neuron is called

Which type of synapse is most common in the nervous system?

The ion that triggers the release of acetylcholine into the synaptic cleft is

Cholinergic synapses release the neurotransmitter

The following are the steps involved in transmission at a cholinergic synapse. What is the correct sequence for these events? 1. Chemically-gated sodium channels on the postsynaptic membrane are activated. 2. Calcium ions enter the synaptic terminal. 3. Acetylcholinesterase hydrolyzes acetylcholine. 4. An action potential depolarizes the synaptic terminal at the presynaptic membrane. 5. The pre-synaptic terminal reabsorbs choline. 6. Acetylcholine is released from storage vesicles by exocytosis. 7. Acetylcholine binds to receptors on the postsynaptic membrane. 8. Calcium ions are removed from the cytoplasm of the pre- synaptic terminal.

If the chemically gated sodium channels in the postsynaptic membrane were completely blocked,

The effect that a neurotransmitter has on the postsynaptic membrane depends on the

When cholinergic receptors are stimulated,

What triggers the release of acetylcholine from a synaptic terminal?

At a(n) ________ synapse, a neurotransmitter is released to stimulate the postsynaptic membrane.

In a(n) ________ synapse, current flows directly between cells.

At a synapse the 0.2-0.5 milliseconds it takes for calcium influx and neurotransmitter release is called

Synaptic delay is caused by

Which ion triggers synaptic vesicles to discharge neurotransmitter into the synaptic cleft?

What most directly causes the exocytosis of Ach in synaptic vesicles?

When a neuron communicates with another at a synapse on a dendrite, this is called an __________ synapse.

Resynthesis of ACh occurs in the __________.

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

A molecule that carries information across a synaptic cleft is a

When calcium ions enter the synaptic terminal,

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

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

Adrenergic synapses release the neurotransmitter

Which of the following is the most important excitatory neurotransmitter in the brain that is important in learning and memory?

After acetylcholinesterase acts, the synaptic terminal

A deficiency in which neurotransmitter would cause Parkinson's-like symptoms?

Which neurotransmitter has a direct effect on opening chloride channels?

Which neurotransmitter has widespread effects on a person's attention and emotional state?

Which of the following neurotransmitters is a dissolved gas?

Which of the following neurotransmitters are known to bind to G-protein coupled receptors?

The molecule responsible for making cyclic AMP is called

Which of the following is the primary second messenger in G-protein coupled post-synaptic cells?

Which of these substances is considered a neuromodulator?

Which of these neurotransmitters does NOT bind to a plasma membrane receptor?

Which of these neurotransmitters is released at CNS adrenergic synapses?

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

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

Binding of the neurotransmitter to its receptor causes the membrane to

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?

Which of the following best describes the role of calcium in synaptic activity?

What is the role of neurotransmitter at a chemical synapse?

What mechanism releases neurotransmitter from presynaptic neurons?

What type of channel in the postsynaptic membrane binds neurotransmitter?

What is the primary role of the enzyme acetylcholinesterase (AChE) at a cholinergic synapse?

Events that occur at a cholinergic synapse are listed here, but they are arranged in an incorrect order. Choose the correct order of these events below. (a) Calcium influx triggers exocytosis of ACh. (b) An action potential depolarizes the synaptic terminal. (c) ACh is removed by AChE. (d) ACh binds to receptors on the postsynaptic membrane.

A postsynaptic neuron will have an excitatory postsynaptic potential (EPSP) when

The site in the neuron where EPSPs and IPSPs are integrated is the

EPSPs (excitatory postsynaptic potentials) occur when

IPSPs (inhibitory postsynaptic potentials)

When a second EPSP (excitatory postsynaptic potential) arrives at a single synapse before the effects of the first have disappeared, what occurs?

Summation that results from the cumulative effect of multiple synapses at multiple places on the neuron is designated

A neuron whose membrane potential shifts closer to threshold is said to be

In ________, activity at an axoaxonic synapse increases the amount of neurotransmitter released when an action potential arrives at the axon terminus.

In one form of presynaptic inhibition the release of ________ inhibits the opening of voltage gated calcium channels in the axon terminus.

The release of GABA and subsequent inhibition of voltage gated calcium channels is associated with

If a nerve cell receives many IPSPs in different locations at the same time, __________.

The simplest level of information processing takes place at the __________.

The neurotransmitter GABA blocks presynaptic voltage-gated calcium channels. Consequently, GABA produces __________.

If EPSPs summate to a sustained value above threshold, then the initial segment will __________.