Anatomy: Chapter 11 Homework

The period from when an action potential begins until another action potential could be initiated is known as the ________ period. depolarization absolute refractory repolarization hyperpolarization relative refractory

Absolute refractory

An action potential traveling along the entire length of an axon demonstrates ________ propagation. saltatory degraded relative continuous graded

Continuous

What type of conduction takes place in unmyelinated axons? Electrical conduction Saltatory conduction Synaptic transmission Continuous conduction

Continuous conduction

Extensive damage to oligodendrocytes in the CNS could result in a breakdown of the blood-brain barrier. loss of the structural framework of the brain. inability to produce scar tissue at the site of an injury. decreased production of cerebrospinal fluid. reduced speed of nerve impulses.

Reduced speed of nerve impulses.

How do action potential propagation speeds in myelinated and unmyelinated axons compare? -Propagation speeds are similar in both axon types. -Propagation is faster in myelinated axons. -Propagation is faster in unmyelinated axons. -Propagation in myelinated axons is faster over short distances, but slower over long distances.

Propagation is faster in myelinated axons.

________ monitor the position of skeletal muscles and joints. Exteroceptors Proprioceptors Somatic sensory receptors Interoceptors Special sensory receptors

Proprioceptors

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

Glutamate

Which of the following is not a function of the neuroglia? secretion of cerebrospinal fluid support maintenance of blood-brain barrier phagocytosis memory

Memory

After a stroke, what type of glial cell accumulates within the affected brain region? microglia satellite cells ependymal cells Schwann cells oligodendrocytes

Microglia

Which neurotransmitter is the most studied? epinephrine glutamate ACh serotonin

ACh

Where are action potentials regenerated as they propagate along an unmyelinated axon? at myelin at the nodes at every segment of the axon at the internodes

At every segment of the axon

________ line the brain ventricles and spinal canal. Astrocytes Ependymal cells Microglia Oligodendrocytes Satellite cells

Ependymal cells

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization? -Inactivation gates of voltage-gated Na+‎ channels close, while inactivation gates of voltage-gated K+‎ channels open. -Activation gates of voltage-gated Na+‎ channels close, while inactivation gates of voltage-gated K+‎ channels open. -Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open. -Activation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open.

Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open.

Saltatory propagation occurs in _________ axons, in which action potentials _________. Select the best answer. View Available Hint(s) -myelinated; move continuously along the axon toward the axon hillock -unmyelinated; move from one node of Ranvier to another -unmyelinated; spread by depolarizing the adjacent region of the axon membrane -myelinated; move from one node of Ranvier to another

Myelinated; move from one node of Ranvier to another

The concentration of ___ is higher outside than inside the cell.

Na+

Part complete The concentrations of which two ions are highest outside the cell. Na+ and A- (negatively charged proteins) K+ and Cl- K+ and A- (negatively charged proteins) Na+ and Cl-

Na+ and Cl-

Which of the following is a type of glial cell found in the peripheral nervous system? satellite cells microglia ependymal cells astrocytes oligodendrocytes

Satellite cells

A characteristic of graded potentials is __________. -the effect of the transmembrane potential increases with distance from the site of stimulation -the nature of the graded change in membrane potential is determined by the properties of the Nissl bodies of the neuronal cell involved -the stronger the stimulus, the smaller and more concentrated is the area affected -the effect spreads passively through local currents

The effect spreads passively through local currents

In an unmyelinated axon, why doesn't the action potential suddenly "double back" and start propagating in the opposite direction? -The previous axonal segment is refractory. -Positive charges only move in one direction. -The extracellular sodium concentration is too low around the previous axonal segment for an action potential to be (re)generated. -New action potential generation near the soma repels previously generated action potentials.

The previous axonal segment is refractory.

Why are CNS neurons that are lost to injury or disease seldom replaced? They lack mitochondria. They lack a cytoskeleton. They lack lysosomes. They lack centrioles.

They lack centrioles

During depolarization, which gradient(s) move(s) Na+ into the cell? -only the electrical gradient -Na+ does not move into the cell. Na+ moves out of the cell. -both the electrical and chemical gradients -only the chemical gradient

both the electrical and chemical gradients

In the process of continuous propagation, all of the following are true except -depolarization of the axonal membrane only occurs at nodes. -local currents depolarize the region just adjacent to the active zone. -each step takes about one millisecond. -the action potential is triggered by graded depolarization of the initial segment. -at threshold, sodium channels begin to open rapidly.

depolarization of the axonal membrane only occurs at nodes.

Many medications introduced into the bloodstream cannot directly affect the neurons of the CNS because -Schwann cells form a capsule around neurons. -ependymal cells restrict the flow of interstitial fluid between the capillaries and the neurons. -the neurilemma is impermeable to most molecules. -oligodendrocytes form a continuous myelin sheath around the axons. -the astrocytes isolate the CNS by forming a blood-brain barrier.

the astrocytes isolate the CNS by forming a blood-brain barrier.

What is the value for the resting membrane potential for most neurons? -70 mV -90 mV +30 mV

-70 mV

Approximately how fast do action potentials propagate in unmyelinated axons in humans? 1 meter per second 0.1 meters per second 120 meters per second 12 meters per second

1 meter per second

The Na-K ion exchange pump actively transports -1 intracellular sodium ion for 2 extracellular potassium ions. -2 intracellular sodium ions for 1 extracellular potassium ion. -3 extracellular sodium ions for 2 intracellular potassium ions. -3 intracellular sodium ions for 2 extracellular potassium ions. -3 intracellular sodium ions for 1 extracellular potassium ion.

3 intracellular sodium ions for 2 extracellular potassium ions.

When the stimulus voltage is increased, _______. -a greater-than-threshold depolarization results and sodium permeability into the cell increases to overcome the potassium exiting. -a greater-than-threshold depolarization results -sodium permeability into the cell decreases -sodium permeability into the cell increases to overcome the potassium exiting

A greater-than-threshold depolarization results and sodium permeability into the cell increases to overcome the potassium exiting.

When the interval between the stimuli decreases, _______. -a second action potential is generated until the interval reaches the absolute refractory period -a second action potential is generated regardless of the stimulus and the interval -a second action potential is generated until the interval reaches the relative refractory period -a second action potential is generated as long as the stimulus is above threshold

A second action potential is generated until the interval reaches the absolute refractory period

The all-or-none principle states that -all stimuli great enough to bring the membrane to threshold will produce identical action potentials. -the greater the magnitude of the stimuli, the greater the magnitude of the action potential. -only sensory stimuli can activate action potentials. -only motor stimuli can activate action potentials. -all stimuli will produce identical action potentials.

All stimuli great enough to bring the membrane to threshold will produce identical action potentials.

Describe the all-or-none principle. (Module 11.10B) -Stimuli that do not bring the membrane to threshold can still generate an action potential if the stimuli are strong enough. -Stimuli that bring the membrane to threshold will generate a larger or smaller action potential depending on the size of the stimuli. -All stimuli that bring the membrane to threshold will generate identical action potentials. -All stimuli will generate an action potential or none will. -Stimuli that bring the membrane to threshold will generate a longer or shorter action potential depending on the timing of the stimuli.

All stimuli that bring the membrane to threshold will generate identical action potentials.

During the relative refractory period, _______. -the flow of potassium is also depolarizing the neuron. -a second action potential cannot be generated, no matter how strong the stimulus. -another action potential can be generated provided the stimulus is relatively smaller than the original stimulus. -another action potential can be generated provided the stimulus is large enough.

Another action potential can be generated provided the stimulus is large enough.

Oligodendrocytes: maintain the blood-brain barrier. assist in producing, circulating, and monitoring the CSF. are the myelin-producing glial cells in the PNS. are the myelin-producing glial cells in the CNS.

Are the myelin-producing glial cells in the CNS.

The glial cells in the central nervous system that form scar tissue after central nervous system injury are the oligodendrocytes. microglia. ependymal cells. satellite cells. astrocytes.

Astrocytes

Where are action potentials regenerated as they propagate along a myelinated axon? at myelin at the nodes at the internodes at every segment of the axon

At the nodes

The plasma membrane of an axon is called the axon terminal. axoplasm. axokaryon. axon hillock. axolemma.

Axolemma

Which part(s) of the neuron can conduct an action potential? dendrites and cell body cell body and axon dendrites and telodendria dendrites axon and telodendria

Axon and telodendria

In which part of a neuron does Wallerian degeneration occur? (Module 11.5B) axons of PNS neurons cell bodies of PNS neurons cell bodies of CNS neurons dendrites of the PNS neurons axons of CNS neurons

Axons of the PNS neurons

Neurons that have one axon and one dendrite, with the soma in between, are called anaxonic. unipolar. bipolar. tripolar. multipolar.

Bipolar

Name the effectors of the ANS. (Module 11.1C) -skeletal muscle only -skeletal muscle, cardiac muscle, and smooth muscle -cardiac muscle, smooth muscle, glands, and adipose tissue -glands and adipose tissue -cardiac muscle and smooth muscle

Cardiac muscle, smooth muscle, glands, and adipose tissue

Functions of astrocytes include all of the following except conducting action potentials. responding to neural tissue damage. maintaining the blood-brain barrier. forming a three-dimensional framework for the CNS. absorbing excess neurotransmitter.

Conducting action potentials.

An action potential is self-regenerating because __________. -depolarizing currents established by the influx of K+‎ flow down the axon and trigger an action potential at the next segment -repolarizing currents established by the efflux of Na+‎ flow down the axon and trigger an action potential at the next segment -depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment -repolarizing currents established by the efflux of K+‎ flow down the axon and trigger an action potential at the next segment

Depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment

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

Forming a cellular cord that directs axonal regrowth.

In contrast to the internodes of a myelinated axon, the nodes __________. only occur at the beginning and end of the axon have lower membrane resistance to ion movement are wrapped in myelin have higher membrane resistance to ion movement

Have lower membrane resistance to ion movement

Which of the following is defined as a graded hyperpolarization of the postsynaptic membrane? equilibrium potential IPSP resting potential EPSP

IPSP

Action potential propagation begins (is first generated at) what region of a neuron? initial segment node myelin dendrite

Initial segment

________ are the most numerous type of neuron in the CNS. Unipolar neurons Interneurons Bipolar neurons Sensory neurons Motor neurons

Interneurons

________ monitor the internal environment. Interoceptors Endoceptors Special sensory receptors Sensory ganglia Exteroceptors

Interoceptors

If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur except that the -membrane will slowly lose its capacity to generate action potentials. -intracellular concentration of sodium ions will increase. -neuron will slowly depolarize. -inside of the membrane will have a resting potential that is more positive than normal. -intracellular concentration of potassium ions will increase.

Intracellular concentration of potassium ions will increase.

________ monitor the digestive, respiratory, cardiovascular, urinary, and reproductive systems. Proprioceptors Somatic sensory receptors Interoceptors Special sense receptors Exteroceptors

Introceptors

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron, -ion channels in the plasma membrane of the sending neuron open. -vesicles in the synaptic terminal fuse to the plasma membrane of the sending neuron. -the receiving neuron becomes more positive inside. -the receiving neuron becomes more negative inside. -ion channels in the plasma membrane of the receiving neuron open.

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

The concentration of ___ is higher inside than outside the cell.

K+

The membrane is more permeable to ___

K+

The resting membrane potential is maintained by Na+-K+ pumps that actively transport ___ into and ___ out of the cell.

K+, Na+

The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____. K+; Cl- Na+; K+ Na+; Cl- K+; Na+

K+; Na+

The resting membrane potential exists mainly due to passive ________ channels. active mechanically-gated voltage-gated chemically gated leak

Leak

Define membrane potential. (Module 11.6A) -Membrane potential is the maximum times a cell can be stimulated by electrical impulses. -Membrane potential is the maximum speed a cell can propagate electrical impulses. -Membrane potential is the maximum ability of a cell to generate electrical impulses. -Membrane potential is the unequal charge distribution between the inner and outer surfaces of the plasma membrane. -Membrane potential is the ability of a cell to become excitable.

Membrane potential is the unequal charge distribution between the inner and outer surfaces of the plasma membrane.

The smallest neuroglia of the CNS that act as phagocytes are the astrocytes. oligodendrocytes. tanycytes. ependymocytes. microglia.

Microglia

Which neuroglia appear in increased numbers in a person with a brain infection? (Module 11.4B) astrocytes microglia oligodendrocytes ependymal cells satellite cells

Microglia

Why is a CNS neuron not usually replaced after it is injured? (Module 11.2D) -Most CNS neurons are not replaced because we have an abundance of neurons and it is not necessary to replace any that are injured. -Most CNS neurons are not replaced because it is not possible to replace any injured cell in the body. -Most CNS neurons are not replaced because they lack centrioles so they cannot divide. -Most CNS neurons are not replaced because they contain Nissl bodies which prevents the cell from undergoing cellular division. -Most CNS neurons are not replaced because the PNS neurons just take over the functions of any injured CNS neurons.

Most CNS neurons are not replaced because they lack centrioles so they cannot divide.

Neurons that have several dendrites and a single axon are called anaxonic. unipolar. bipolar. tripolar. multipolar.

Multipolar

The most common neurons in the CNS, including the motor neurons that control skeletal muscles, are __________. multipolar neurons bipolar neurons anaxonic neurons unipolar neurons

Multipolar neurons

In which type of axon will velocity of action potential conduction be the fastest? Myelinated axons with the largest diameter Myelinated axons with the smallest diameters Unmyelinated axons with the largest diameter Unmyelinated axons of the shortest length

Myelinated axons with the largest diameter

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? Both Na+ and K+ are pumped into the cell. Na+ is pumped out of the cell and K+ is pumped into the cell. Both Na+ and K+ are pumped out of the cell. K+ is pumped out of the cell and Na+ is pumped into the cell.

Na+ is pumped out of the cell and K+ is pumped into the cell.

A molecule that carries information across a synaptic cleft is a synapse. synaptic cleft. sending neuron. receiving neuron. neurotransmitter.

Neurotransmitter

Which neurotransmitter is located in most neuromuscular and neuroglandular junctions of the sympathetic division of the ANS? norepinephrine glutamate serotonin GABA

Norepinephrine

What produces the brief hyperpolarization during the action potential? -Potassium ions enter the cell until all the potassium channels have closed. -Potassium ions continue to leave the cell until all the potassium channels have closed. -Sodium ions rush into the cell. -The stimulus that initiates the action potential causes voltage-gated sodium channels to open.

Potassium ions continue to leave the cell until all the potassium channels have closed.

The separation of plus and negative charges across the membrane creates a ________ difference, or voltage. gradient potential graded concentration kinetic

Potential

Compare presynaptic and postsynaptic cells. (Module 11.2C) -Presynaptic cells are usually found in the peripheral nervous system and postsynaptic cells are usually found in the central nervous system. -Presynaptic cells are sensory neurons and postsynaptic cells are motor neurons. -Presynaptic cells can be a neuron or another type of cell, such as a skeletal muscle fiber or a gland cell and postsynaptic cells are usually neurons. -Presynaptic cells are motor neurons and presynaptic cells are sensory neurons. -Presynaptic cells are usually neurons and postsynaptic cells can be a neuron or another type of cell, such as skeletal muscle fiber or a gland cell.

Presynaptic cells are usually neurons and postsynaptic cells can be a neuron or another type of cell, such as skeletal muscle fiber or a gland cell.

Which of the following statement is false when comparing neurons and muscle tissue? -Muscle tissue and neurons both have refractory periods. -Muscle tissue and nerves are both excitable. -Action potentials last longer in muscle tissues compared to neurons. -Resting membrane potentials are greater (more positive) in muscle compare to neurons. -Muscle tissue and neurons both have a resting membrane potential.

Resting membrane potentials are greater (more positive) in muscle compare to neurons.

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

Saltatory propagation

Which glial cells are found only in the PNS? ependymal cells Schwann cells microglia oligodendrocytes

Schwann cells

Are unipolar neurons in a tissue sample of the PNS more likely to have a sensory or a motor function? (Module 11.3C) sensory function motor function

Sensory funtion

Which of the following is important in emotional states? glutamate glycine gamma aminobutyric acid serotonin noradrenalin

Serotonin

The movement of what ion is responsible for the local currents that depolarize other regions of the axon to threshold? sodium (Na+) Potassium (K+) voltage-gated sodium (Na+) channels calcium (Ca2+)

Sodium (Na+)

Why does the threshold increase when the interval between the stimuli decreases? Calcium is flowing out the cell. Some sodium channels have been inactivated and cannot be reopened immediately. Sodium is flowing out of the cell. Potassium is flowing into the cell.

Some sodium channels have been inactivated

The site of intercellular communication between neurons is the telodendria. synaptic knob. synapse. collateral branch. hillock.

Synapse

The small space between the sending neuron and the receiving neuron is the synaptic cleft. neurotransmitter. synaptic terminal. calcium channel. vesicle.

Synaptic cleft

Part complete Compare the central and peripheral nervous system. (Module 11.1A) -The central nervous system consists of the brain and it integrates, processes, and coordinates sensory data and motor commands. The peripheral nervous system consists of the spinal cord, and sensory and motor divisions. -The central nervous system consists of all the nervous tissue outside the enteric nervous system. The peripheral nervous system consists of the brain and spinal cord and it integrates, processes, and coordinates sensory data and motor commands. -The central nervous system consists of the brain and spinal cord and it integrates, processes, and coordinates sensory data and motor commands. The peripheral nervous system consists of all the nervous tissue outside the central and enteric nervous systems.

The central nervous system consists of the brain and spinal cord and it integrates, processes, and coordinates sensory data and motor commands. The peripheral nervous system consists of all the nervous tissue outside the central and enteric nervous systems.

Why does regeneration of the action potential occur in one direction, rather than in two directions? View Available Hint(s) -The inactivation gates of voltage-gated K+‎ channels close in the node, or segment, that has just fired an action potential. -The activation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just depolarized. -The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential. -The activation gates of voltage-gated K+‎ channels open in the node, or segment, that has just depolarized.

The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential.

What is the function of the myelin sheath? -The myelin sheath decreases the resistance of the axonal membrane to the flow of charge. -The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals. -The myelin sheath decreases the speed of action potential conduction from the initial segment to the axon terminals. -The myelin sheath increases the insulation along the entire length of the axon.

The myelin sheath increases the speed of action potential

When calcium ions enter the synaptic terminal, -they cause an action potential in the sending neuron. -they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron. -the inside of the receiving neuron becomes more positive. -the inside of the receiving neuron becomes more negative. -neurotransmitter molecules are quickly removed from the synaptic cleft.

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

Most sensory neurons of the PNS are of which type? anaxonic neurons bipolar neurons unipolar neurons multipolar neurons

Unipolar neurons

Neurotransmitter for release is stored in synaptic mitochondria. telodendria. neurosomes. vesicles. knobs.

Vesicles

The generation of an action potential in a neuron requires the presence what type of membrane channels? Select the best answer. leakage channels chemically gated channels voltage-gated channels membrane channels are not required

Voltage-gated channels

Most CNS neurons lack centrioles. This observation explains -why CNS neurons grow such long axons. -why CNS neurons cannot divide. -the ability of neurons to generate an action potential. -the ability of neurons to communicate with each other. -the ability of neurons to produce a resting potential.

Why CNS neurons cannot divide.

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? View Available Hint(s) -Without myelin, the internode membrane resistance increases, preventing local currents from reaching adjacent nodes. -Without myelin, the internode membrane is depolarized more easily. -Without myelin, the node membrane more easily becomes refractory. -Without myelin, the internode membrane resistance decreases, preventing local currents from reaching adjacent nodes.

Without myelin, the internode membrane resistance decreases, preventing local currents from reaching adjacent nodes.

If a signal from a sending neuron makes the receiving neuron more negative inside, View Available Hint(s) -the sending neuron becomes more positive inside. -the receiving neuron is less likely to generate an action potential. -the receiving neuron immediately generates an action potential. -the receiving neuron is more likely to generate an action potential. -the sending neuron becomes more negative inside.

the receiving neuron is less likely to generate an action potential.