Anatomy Homework Questions (Chapter 11)

What are the ciliated CNS neuroglia that play an active role in moving the cerebrospinal fluid called?

Ependymal cells

The diffusion of what ion across the neuronal membrane is responsible for the local currents that depolarize regions of the axon to threshold?

Na+

In what way does the interior surface of a cell membrane of a resting neuron differ from the external environment? The inferior is ________.

Negatively charged and contains less sodium (Na+)

What are bundles of neurofilaments that are important in maintaining the shape and integrity of neurons?

Neurofibrils

Simple reflex arc

Stimulus -> receptor -> sensory neuron -> integration center -> motor neuron -> effector -> response

In myelinated axons the voltage-regulated Na+ channels are concentrated at the nodes of Ranvier. (True/False)

True

Large diameter nerve fibers conduct impulses much faster than small diameter fibers. (True/False)

True

Opening K+ or Cl- channels in postsynaptic membrane would produce an inhibitory postsynaptic potential. (True/False)

True

The Na+ concentration is higher outside the cell compared to inside. The K+ concentration is higher inside the cell compared to outside. (True/False)

True

The oligodendrocytes can myelinate several axons. (True/False)

True

The synaptic cleft prevents an impulse from being transmitted directly from one neuron to another. (True/False)

True

An action potential releases neurotransmitter from a neuron by opening which channel?

VG Ca2+ channels

What is an excititory neurotransmitter secreted by motor neurons innervating skeletal muscle?

acetylcholine

Which of the following neurotransmitters is broken down by an enzyme before being returned?

acetylcholine

Which of the following electrical events occurs when a certain threshold is reached?

action potential

Where in the neuron is an action potential initially generated?

axon hillock

Neurons can be classified structurally by the number of processes extending from their cell bodies. Which of the following is the most common neuron type in humans?

multipolar

An impulse from one nerve cell to communicated to another nerve cell via the _______.

synapse

The nodes of Ranvier are found only on myelinated, peripheral neurons processes. (True/False)

False

This neuron is most depolarized at ______

+30mV

This cell reaches threshold at approximately ____ msec.

0.6

Sequence at the chemical synapse.

1. Action potential sweeps down presynaptic axon 2. Calcium channels open in axon termial 3. Synaptic vesicles fuse and exocytize neurotransmitter 4. Diffusion of neurotransmitter into extracellular fluid separating two neurons membranes 5. Graded potential at postsynaptic membrane

List in order the events of an action potential.

1. Activation gates on Na+ channels open; Na+ enters cell. 2. Cell depolarizes 3. Inactivation gates on Na+ channels close and activation gates on K+ channels open; K+ leaves the cell. 4. Cell repolarizes. 5. Activation gates on K+ channels begin to close. 6. Cell experiences hyperpolarization.

Events that occur at the synapse.

1. An action potential arrives at the synaptic terminal 2. Calcium channels open, and calcium ions enter the synaptic terminal 3. Vesicles containing neurotransmitter fuse with the plasma membrane of the sending neuron 4. Neurotransmitter molecules diffuse across the synaptic cleft 5. The neurotransmitter molecule bind to receptors in the plasma membrane of the receiving neuron, causing ion channels there to open.

What is the magnitude of an action potential?

100mV

This neuron spends approximately _____ msce in a hyperpolarized state.

2.5

The Nissl bodies seen in the neuron cell body represents which cellular organelle?

All the voltage-gated Na+ and K+ channels are closed.

What correctly describes a graded potential?

Amplitude of various sizes

Cold sores on the skin of the mouth occur when herpes simplex viruses that are dormant in neural ganglia become active and travel to the skin of the mouth. Which of the following is the mechanism by which these viruses travel from the ganglia (located within the head) to the skin of the mouth?

Anterograde axonal transport

Neuroglia that control the chemical environment around neurons by buffering ions such as K+ and recapturing neurotransmitters are _____________.

Astrocytes

The part of a neuron that conducts impulses away from the cell body is called a(n):

Axon

Which part of the neuron is responsible for generation a nerve impulse?

Axon

Which of the following is true of axons? A. Axons use chemically gated ion channels to generate graded potentials. B. A neuron can have only one axon, but the axon may have occasional branches along its length. C. Smaller (thinner) axons are more likely to bear myelin sheaths than larger (thicker) axons. D. Neurons can have multiple axons but only one dendrite.

B. A neuron can have only one axon, but the axon may have occasional branches along it's length.

The term central nervous system (CNS) refers to the what?

Brain and spinal cord

Which of the following is not a function of the autonomic nervous system? A. innervation of cardiac muscle B innervation of smooth muscle of the digestive tract C. innervation of glands D. innervation of skeletal muscle

D. Innervation of skeletal muscle

Which of the following is NOT one of the basic functions of the nervous system? A, monitor changes occurring both inside and outside the body B. integration of sensory input C. control the activity of muscles and glands D. regulation of neurogenesis

D. Regulation of neurogensis.

Which of the following is not a characteristic of neurons? A. They conduct impulses. B. They have an exceptionally high metabolic rate. C. They have extreme longevity. D. They are mitotic

D. They are mitotic.

Which of the following is not a function of astrocytes? A. support and brace neurons B. control the chemical environment around neurons C. anchor neurons to blood vessels D. guide the migration of young neurons, synapse formation, and helping to determine capillary permeability E. provide the defense for the CNS

E. Provide defense for the central nervous system

What is the clearest example of a neuronal membrane's selective permeability?

K+ ions can diffuse across the membrane more easily than Na+ ions.

The ion ___ is crossing the cells plasma membrane at ___ msec.

K+;1.5

What is the major role of the Na+-K+ pump in maintaining the resting membrane potential?

Maintaining the concentration gradients for Na+ and K+ across the cell membrane.

Which type of glial cells monitors the health of neurons, and can transform into a special type of macrophage to protect endangered neurons?

Microglia

Which of the following would increase the membrane permeability of K+?

More K+ leakage channels

Schwann Cells are functionally similiar to what?

Oligodendrocytes

Which type of glial cells produces the myelin sheaths that insulate axons, or nerve fibers, in the CNS?

Oligodendrocytes

Which peripheral nervous system (PNS) neuroglia forms the myelin sheath around larger nerve fibers in the PNS?

Schwann cells

What is the conducting region of the neuron?

The axon

A patient is admitted to the hospital with exacerbation of MS. She ask the nurse "why did this have to happen to me again? I was doing so well." Why are some forms of MS characterized by periods of remission and exacerbation's?

The axons are not damaged; growing number of Na+ channels appear spontaneously in the demyelinated fibers, allowing conduction to resume.

What does the 0 mV on the y-axis of an action potential tracing represent?

The cell's membrane is at equilibrium.

What part of the nervous system performs information processing and integration?

The central nervous system.

Imagine you changed the concentration of K+ outside a neuron such that the resting membrane potential changed to -80mV. What have you changed?

The electrical gradient for K+ and the concentration gradient for K+.

A second nerve impulse cannot be generated until what?

The membrane potential has been reestablished.

Hypothetically, what would be the most immediate effect of doubling the number of Na+ leakage channels in the plasma membrane?

The resting membrane potential would become less negative (more positive).

Suppose a drug is developed that blocks K+ leakage channels. The drug prevents ions from passing through those channels. If this drug was applied to a neuron, what would be the most immediate effect on that neuron?

The resting membrane potential would become less negative (more positive).

What allows us to consciously control our skeletal muscles?

The somatic nervous system

What is the electrochemical gradient of an ion?

The sum of the electrical and concentration gradients for that ion.

What is not true of graded potentials?

They increase in amplitude as they move away from the stimulus point.

Axon diameter and degree of myelination determine nerve impulse conduction velocity. (True/False)

True

Following repolarization, the neuron may become slightly hyperpolarized before it re-establishes its resting membrane potential. Hyperpolarization is due to a difference between now the voltage gated Na+ and K+ channels work. What is the difference?

VG Na+ channels stop the flow of Na+ relatively quickly, while VG K+ channels are slow to close, resulting in overshoot.

When an action arrives at the end of the axon terminal, a series of events take place that result in the release of neurotransmitter from the presynaptic axon. Select the answer that correctly describes the primary stimulus for vesicles to move towards the cell membrane and eventually release their contents.

VG membrane channels open, and Ca2+ enters the cytoplasm, increasing intracellular calcium.

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

Voltage-gated Na+ channels

The period after an initial stimulus when a neuron is not sensitive to another stimulus is the ________.

absolute refractory period

Which of the following will occur when an excitatory postsynpatic potential is being generated on the dendritic membrane?

a single type of channel will open, permitting simultaneous flow of Na+ and K+

What type of stimulus is required for an action potential to be generated?

a threshold level depolarization

Caffeine's stimulatory effects result from blocking receptors for which neurotransmitter?

adenosine

Action potential

also called nerve impulse transmitted by axons

Relative refractory period

an exceptionally strong stimulus can trigger a response

What conditions will increase the diffusion of molecules such as neurotransmitters?

an increase in the amount of neurotransmitter exocytized by the presynaptic axon

Subthreshold stimulus

an insufficient stimulus

What describes the nervous system integrative function?

analyzes sensory information, stores information, makes decision

Threshold stimulus

any stimulus below this intensity will result in no response in a neuron

Which of the following neuroglia is most responsible for helping determine capillary permeability in nervous tissue?

astryocytes

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

at the nodes of Ranvier

Which of the following is a rare type of sensory neuron that is found in special sensory structures like the retina of the eye?

bipolar

Binding of a neurotransmitter to its receptor opens _____ channels on the ____ membrane.

chemically gated; postynaptic

Direct depolarization path within one neuron.

dendrite -> cell body -> axon hillock -> axon -> presynaptic terminal

Converging circuit

different types of sensory input can have the same ultimate effect

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

either depolarize or hyperpolarize

Which of the following neurotransmitters inhibits pain and is mimicked by morphine, heroin, and methadone?

endorphin

Which neurotransmitter(s) is/are the body's natural pain killer?

endorphins

Which of the following neurotransmitters acts as a natural opiate?

endorphins

Which of the following line the central cavities of the brain and spinal cord and provide a fairly permeable barrier between the CSF and nervous tissue?

ependymal cells

Which membrane potential occurs because of the influx of Na+ through chemically gated channels in receptive region of a neuron?

excitatory postsynaptic potential

A potential of -90 mV is considered __________.

hyperpolarized *anything over -70mV is considered hyperpolarized*

What component of the reflex arc determines the response to a stimulus?

integration center

Diverging circuit

involved in activating fibers of a skeletal muscle

Reverberation circuit

involved in control of rhythmic activities (breathing)

Which of the following factors is associated with increased conduction velocity in an axon?

large diameter

Predict the possible effect of a drug that totally blocks the neurotransmitter receptor on the postsynaptic membrane.

local graded potentials and action potential transmission is blocked and there is not response by the postsynpatic cell, the muscle.

Parallel after discharge circuit

may be involved in complex, exacting types of mental processing

Which statement describes exocytosis?

membrane organelles fuse with the membrane and release contents out of the cell

Spatial summation occurs when __________.

multiple local potentials occur at different places on the same cell at the same time *spatial summation refers to the same time at different locations*

The substance released at axon terminals to propagate a nervous impulse called a(n) ________.

neurotransmitters

Is nucleic acid a chemical class of neurotransmitters?

no

From where can collaterals emerge on a myelinated nerve?

nodes of Ranvier

What are gaps found along a myelin sheath?

nodes of Ranvier

Temporal summation

numerous nerve impulses arriving at a synapse at closely timed intervals exert a cumulative effect

In MS, the cells that are the target of an autoimmune attack are the ______.

oligodendrocytes

Diverging cirucuit

one incoming fiber triggers responses in every increasing numbers farther and farther along the circiut

Which of the following conditions would cause synaptic potentiation?

opening of NMDA (N-methyl-D-aspartate) receptors and influx of Ca++

Which of the following substances plays the major role in generating the membrane potential of a neuron through its passive movement?

potassium

The interior of a nerve cell has a slight excess of negative charge because __________.

potassium diffuses out of the cell

Which best represents synaptic transmission?

presynaptic axon to synapse to dendrite or postsynaptic cell body

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

presynaptic neuron

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

propagation is faster in myelinated axons

The sodium-potassium ion pump will __________.

pump three sodium ions out of the cell for every two ions of potassium it brings into the cell

During which phase of an action potential are voltage-gated K+ channels open, while voltage-gated Na+ channels are closed?

repolarizing phase

The ______ is due to differences in K+ and Na+ concentrations on either side of the plasma membrane, and the differences in permeability of the membrane to these ions.

resting membrane potential

Organelles for degradation or recycling are moved through the axon by __________.

retrograde movement

Which neuron circuit pattern is involved in the control of rhythmic activities such as breathing?

reverberation circuit

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

saltatory conduction

Which pattern of neural processing works in predictable, all-or-nothing manner, where reflexes are rapid and automatic responses to stimuli, in which particular stimulus always causes the same response?

serial processing

The sensory, or afferent, division of the peripheral nervous system transmits information from the __________ to the CNS.

skin

Hyperpolarization results from?

slow closing voltage-gated K+ channels

What best characterizes depolarization?

small consecutive steps of Na+ penetration into the axon along its length

Spatial summation

stimulation of a postsynpatic neuron by many terminals at the same time

An action potential is one segment of axon causes adjacent sections of axon membrane to reach threshold through what mechanism?

the generation of local currents

Depolarization

the interior of the cell becomes less negative due to an influx of sodium ions

Saltatory conduction is made possible by

the myelin sheath.

Absolute refractory period

the neuron cannot respond to a second stimulus, no matter how strong

If the membrane of a postsynaptic dendrite is setting up a graded potential, what must have happened after neurotransmitter was released by the presynaptic terminal?

the neurotransmitter bound at postsynaptic receptors to open postsynaptic ion channels

In a myelinated axon, how do the nodes of Ranvier differ from other segments of the same axon?

the nodes are more permeable to ions

The repolarization phase of an action potential results from?

the opening of voltage-gated K+ channels

During action potential propagation in an unmyelinated axon, why does the action potential suddenly "double back" and start propagation in the opposite direction?

the previous axonal segment is in the refractory period

Repolarization

the specific period during which K+ ions diffuse out of the neuron due to a change in membrane permeability

The myelin on a myelinated neuron can be degraded or destroyed in diseases such as MS - a process called demelination. If a myelinated neuron was affected by demyelination how would this affect action potentials in that neuron?

the speed of action potential propagation would be slower