A & P Chapter 11

Assume you have a membrane with only potassium leakage channels. The RMP is -90mV. Predict the RMP if we add Na+ leakage channels. The most likely RMP value of Na+ is ___

-70 mV

What are the three functions of the nervous system?

1. sensory input 2. integration 3. motor output

How would an increased extracellular K+ concentration affect K+ diffusion at leakage (nongated) channels and the membrane potential?

A decrease in the electrochemical gradient would reduce K+ leak so cells would be less negative (more depolarized).

Cl- is a common, negatively charged extracellular ion. Predict the effect on the RMP if many Cl- gated channels are suddenly opened.

A more negative RMP would result. Cl- is negatively charged and has a higher concentration in the ECF. The opening of Cl- channels would allow more negative charge to attempt to enter the cytoplasm. If the cell's normal RMP were -70mV, it would now become more negative. The farther away the RMP is from zero, either in the positive or in the negative direction, the greater the separation of charges is. This is called hyperpolarization. When the RMP moves closer to 0 mV, depolarization occurs.

The graded potentials produced at the part of the neuron labeled ___, are generated by ion flow through ___ channels

A) chemically gated

If we consider neurons to be carrying on conversations, which portion(s) of the neuron "listen(s)?"

A. Dendrites and B. cell body

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

Adenosine

Endorphins ____

Are peptides with inhibitory, opiate-like actions

Which of the pictured cell types influences neuronal function by "mopping up" leaked potassium ions and by recapturing and recycling released neurotransmitters? These cells also participate in information processing in the brain.

Astrocyte, which is depicted by (a)

From where can collaterals emerge on a myelinated nerve?

At the myelin sheath gaps (nodes of Ranvier)

You are driving and see a red light ahead. Your nervous system indicates "stop", and your foot hits the brake. Which portion of the nervous system, as indicated in the figure, is responsible for the decision to stop?

B. Integration

Somatic motor fibers carry information from the _______.

CNS to skeletal muscles

Which type of ion channel opens when a neurotransmitter binds to it?

Chemically gated (ligand-gated) channels

Which of the following does not describe the function of the structure labeled (B)?- Nucleolus

Conductive region of the neuron

Match the system with its correct description: The somatic nervous system __________.

Conducts impulses from CNS to skeletal muscles

If we consider neurons to be carrying on conversations, which portion of the neuron "speaks" by releasing neurotransmitters?

D. Axon terminal

Which structure is the secretory region of the neuron?

D. axon terminal

The prefix ___ means "do the opposite of or reverse."

De-

Na+ channels open during which of the following events?

Depolarization phase of an action potential

Which option correctly describes the event shown in the figure?

Depolarizing graded potential that could have resulted from an increase in extracellular K+

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

Ependymal cells

Which of the following describes acetylcholine?

Excites skeletal muscle

Which fiber type consists of small diameter, unmyelinated axons, that propagate nerve impulses slowly?

Group C fibers

The prefix ___ means "higher than normal."

Hyper-

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

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

Dopamine ____

Is a "feel good" transmitter; deficient in Parkinson's disease

The primary determinant of the resting membrane potential

K+ permeability

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

K+, Na+

Double the number of closed channels for k+

Largely unchanged

Double the size of the cell, without adding channels

Largely unchanged

Which statement best describes the role of leakage (nongated) channels?

Leakage channels help maintain the resting membrane potential.

The resting membrane potential of a cell

Membrane potential of −70 mV

The point at which there is no net movement of K+ into or out of the cell

Membrane potential of −90 mV

Based on your understanding of this cell's function, you might expect this cell to be active in neurodegenerative disorders like Alzheimer's where this cell removes damaged neurons. Additionally, this cell is active in preventing encephalitis and meningitis due to its ability to phagocytize microorganisms.

Microglial cell, which is depicted by B

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

Myelinated axons with the largest diameter

The concentration of ___ is higher outside than inside the cell

Na+

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

Na+ and Cl-

Which of the following is not a characteristic of neurons?

Neurons are relatively small, simple-structured cells.

Which of the following terms is correctly matched with its definition?

Nucleus: a collection of neuron cell bodies in the CNS

The movement of which ion leakage (nongated) channels plays the most important role in generating the resting membrane potential?

Potassium

How can the central nervous system determine whether a particular stimulus is intense or weak?

Stronger stimuli generate action potentials more frequently than weaker stimuli.

The prefix ___ means "being together" or "similar"

Syn-

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

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

What is the nervous system?

The master controlling and communicating system of the body

What is the function of the myelin sheath?

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

Which of the following represents a hyperpolarizing change in membrane potential called an inhibitory postsynaptic potential (IPSP)?

The postsynaptic membrane becomes more permeable to potassium and chloride.

Which of the following events begins with opening of potassium gates and the rushing out of K+?

The repolarization phase in an action potential

All voltage-gated Na+ and K+ channels are closed during which of the following stages?

The resting state of a neuron

What is the primary difference between the somatic nervous system and the autonomic nervous system?

The somatic nervous system allows us to consciously control our skeletal muscles, and the autonomic nervous system controls activity that humans cannot consciously control, such as the pumping of the heart and the movement of food through the digestive tract.

Which of the following is not true of chemical synapses?

They transmit nerve impulses directly from one neuron to another.

Which statement is true of the glial cell pictured above?

This glial cell has processes that touch nearby neurons, monitoring their health, and when this glial cell senses that certain neurons are injured or in other trouble, this microglial cell migrates toward them.

In axonal transport, retrograde movement is transport toward the cell body. Which of the following move in this direction?

Worn out organelles

Saltatory conduction refers to

a conduction process in myelinated axons where the electrical signal appears to jump from gap to gap along the axon

In considering the types of neurons and their predominant functions, efferent is to multipolar as

afferent is to unipolar

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 transport

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

astrocytes

Which of the following types of glial cells are the most abundant and versatile and aid in making exchanges between capillaries and neurons?

astrocytes

Which of the following divisions of the nervous system is also known as the involuntary nervous system?

autonomic nervous system

What does the CNS consist of?

brain and spinal cord

An appropriate label for B in the figure shown here could also be the ____

central nervous system

What parts is the nervous system divided into?

central nervous system and peripheral nervous system

Match the system with its correct description: The peripheral nervous system __________.

consists of cranial and spinal nerves carrying impulses to and from the brain and spinal cord

Match the system with its correct description: The central nervous system __________.

consists of the brain and spinal cord

What does the PNS consist of?

cranial and spinal nerves

When a neuron is stimulated and sodium channels open, the process of ___ has begun

depolarization

An action potential is self-regenerating because __________.

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

The point marked 2, on the figure, can be described as

depolarizing graded potential as ions move through nonvoltage-gated channels

Which of the following circuit types is exemplified by impulses that travel from a single neuron of the brain, activate one hundred or more motor neurons in the spinal cord, and excite thousands of skeletal muscle fibers?

diverging circuit

Which of the following neurotransmitters acts as a natural opiate as it inhibits pain?

endorphins

________ are a group of natural chemicals that reduce the perception of pain.

endorphins

Which of the following types of glial cells line the central cavities of the brain and spinal cord, where they help to circulate the cerebrospinal fluid?

ependymal cells

When potassium channels have been open long enough to go below resting membrane potential, ___ has occurred

hyperpolarization

Which of the following describes a change of membrane potential from -70mV to -75mV?

hyperpolarization

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.

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

retrograde movement

Which of the following characteristics is not associated with a myelinated nerve fiber in the peripheral nervous system?

slow conduction of nerve impulses

Calcium provides structure to bones, stimulates muscle contraction, alters heart rate, and stimulates hormone release. In a neuron, calcium's main role is ________.

stimulating the release of neurotransmitters

A stimulus that fails to generate an action potential is called a ________.

subthreshold stimulus

When calcium ions enter the synaptic terminal,

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

Indicate, by letter, where one would find short-distance signals called graded potentials that travel toward the cell body.

A. dendrites

Which letter matches the process(es) of the neuron that provide(s) an enormous surface area for receiving signals from other neurons?

A. dendrites

The point marked 1, on the figure, can be described as

All gated Na+ and K+ channels are closed

Identify the correctly classified neurons

Almost all interneurons are multipolar and most are confined within the CNS.

Which of the following best describes the all-or-none phenomenon?

An action potential occurs completely when threshold is met and does not happen at all if threshold is not met.

multiple sclerosis is

An autoimmune disease that leads to destruction of the myelin sheaths in the CNS

In the figure above, which letter(s) correspond(s) to the peripheral nervous system?

Both A and C represent portions of the peripheral nervous system (PNS).

What is the difference between nerves and tracts?

Bundles of axons are called tracts in the CNS and nerves in the PNS.

In a chemical synapse, which of the following best describes the role of calcium ions?

Calcium ions trigger exocytosis of neurotransmitter.

Which of the following statements is false?

Electrical synapses provide a complex means to allow areas of the brain to work independently

The prefix ___ means "within."

Endo-

GABA ___

In generally inhibitory; found throughout the CNS

Which of the following events is not involved in the transfer of information across a chemical synapse?

Ions flow directly from one neuron to the next.

Serotonin ___

Is a mood transmitter and drugs that block its uptake relieve anxiety and depression

Norepinephrine ___

Is a neurotransmitter of postganglionic neurons in the sympathetic nervous system

The concentration of ___ is higher inside than outside the cell

K+

The membrane is more permeable to ___

K+

In axonal transport, anterograde movement is transport away from the cell body. Which of the following move in this direction?

Mitochondria and enzymes needed to synthesize certain neurotransmitters

Which of the following is not true of motor (efferent) neurons?

Motor (efferent) neurons are bipolar.

Which of the following could cause a graded depolarization?

Na+ entering the cell through chemically gated channels

Although it plays a role, it is not a primary determinant of the resting membrane potential

Na+ permeability

Based on your understanding of this cell's function, diseases such as multiple sclerosis, that damage the myelin sheath of neurons, likely affect which of the cells in the figure?

Oligodendrocyte, which is depicted by D

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

A resting neuron is an unstimulated neuron that is not presently generating an action potential. The resting membrane potential is the separation of the relative positive and negative charges across the membrane if a cell at rest. Drag the charges to the correct side of the membrane to represent the resting membrane potential of a typical neuron.

Outside is positive, inside is negative

Which of the following best defines neural integration?

Processing and interpretation of sensory input and determining what should be done at each moment in the body

Reflexes are ___

Rapid automatic responses to a stimulus in which the particular stimulus always produces the same motor response

Which of the following is an example of serial processing?

Reflexively withdrawing your hand after touching a hot object

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

Repolarizing phase

Pictured is a cross section of a myelinated axon in the peripheral nervous system (PNS). Which glial cell type produces the myelin sheath, indicated by the arrow, in the PNS?

Schwann cell

In the figure shown, A represents a neuron carrying information from the eye to the brain. Which of the following correctly describes A?

Sensory nerve fiber within a cranial nerve

Drag and drop the correct concentrations and the direction of the concentration gradient in a cell at RMP. Answers may be used more than once or not at all. The appropriate arrow should be placed on the plasma membrane—the targets appear on either side of the pumps.

The Na+ concentration is higher outside of the cell, while the concentration of K+ is higher inside the cell.

Imagine that the cell membrane from the previous problem becomes more permeable to Na+. Predict how this will affect the RMP.

The RMP will be more positive.

Which of the following begins with the opening of the Na+ channels and ends when the Na* channels begin to reset to their original resting state?

The absolute refractory period

You are going to record RMP from a cell using an electrode. You place your electrode and record a resting membrane potential every millisecond. You record an initial value of -70mV; however, over time you notice that your recordings become more and more positive until the RMP reaches 0mV. Assuming that Na+ and K+ are the major determinants of RMP in this cell, which of the following could best explain your results?

The cell's Na+-K+ ATPase pumps have stopped functioning. -Yes! Since the RMP eventually becomes zero, the concentration of ions on either side of the membrane would be roughly equal. Without active processes to maintain concentration gradients, we would expect the concentration of ions on either side of the membrane to equilibrate.

Excessive potassium efflux as a result of relatively slower closure of the potassium gates corresponds to what part of an action potential curve?

The hyperpolarization phase of an action potential

Which of the following results if the neuron is stimulated at the time point indicated by the arrow?

The neuron cannot respond to another stimulus, no matter how strong, because this time point is within the absolute refractory period.

Place the events involved in generation of an action potential in the correct order of occurrence from left to right.

Threshold stimulus Na+ channels open. Na+ influx depolarization. Na+ channels close and K+ channels open. K+ flux depolarization. Hyper polarization K+ channels close

What type of conduction takes place in unmyelinated axons?

continuous conduction

Decrease the concentration of Na+ outside the cell by half

more negative

Double the number of K+ leak channels

more negative

Double the concentration of K+ outside the cell

more positive

Triple the number of Na+ leak channels

more positive

Complete the following sentence. The operation of the Na+-K+ ATPase pump ____

moves 3 Na+ to the ECF and 2 K+ to the cytoplasm -The pumps move more Na+ than K+, which counteracts the effect of the membrane's being more permeable to K+ (more K+ leak channels than Na+).

Spatial summation occurs when __________.

multiple local potentials occur at different places on the same cell at the same time

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

Interneurons and motor neurons are which of the following?

multipolar neurons

The prefix ___ means pertaining to the nervous system

neuro

Supporting cells of the nervous system are collectively called ___

neuroglia

A molecule that carries information across a synaptic cleft is a

neurotransmitter

In multiple sclerosis, the cells that are the target of an autoimmune attack are the

oligodendrocytes

Visceral sensory (afferent) fibers carry information from the ____

organs in the ventral body cavity to CNS

Which of the following circuit types is likely to be involved with making precise mathematical calculations?

parallel after-discharge circuit

The prefix ___ means around or surrounding

peri

Structures of the nervous system surrounding, but not part of the central nervous system are part of the ___

peripheral nervous system

Which of the following could produce the IPSP shown in the graph?

potassium ions leaving the cell

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

The point marked 3, on the figure, can be described as

representing the portion of the action potential, where Na+ entry depolarizes the neuron, opening up additional voltage-dependent Na+ channels that allow in even more Na+

Which type of axonal transport allows certain viruses to circumvent the barrier created by astrocytes to enter into the CNS?

retrograde transport

The chromatophilic substance, or Nissl bodies, seen in the neuron cell body represents which cellular organelle(s)?

rough endoplasmic reticulum

A neuron with a distal peripheral process and a central process that extends to the CNS is most likely _________________.

sensory neuron

The somatic sensory (afferent) fibers of the peripheral nervous system transmit information from the ____ to the CNS

skin

Somatic sensory (afferent) fibers carry information from the ____

skin, skeletal muscles, and joints to CNS

Which of the following could produce the EPSP shown in the graph?

sodium ions entering the cell

In the figure above, C most specifically represents which subdivision of the nervous system?

somatic nervous system

Two consecutive neurons communicate at a ____, where they physically come together

synapse

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

synaptic cleft

Which of the following best describes a rapidly firing presynaptic neuron that causes EPSPs that are close in time?

temporal summation

Bodily functions that follow "a law unto itself" are controlled by the involuntary nervous system. This system is also termed __________ and functions to __________.

the autonomic nervous system (ANS); conduct impulses from the CNS to cardiac muscle, smooth muscle, and glands

The resting membrane potential of neurons is determined by

the distribution, across the cell membrane, of large anionic cytoplasmic proteins, Na+, K+, and Cl-my

A neuron will not respond to a second stimulus of equal strength to the first stimulus to which it has already responded because __________.

the neuron is in the absolute refractory period

The point marked 5, on the figure, can be described as

the period of increased K+ permeability that typically lasts longer than needed to restore the resting state

The point marked 4, on the figure, can be described as

the point in time when Na+ entry declines and the slow voltage-gated K+ channels open

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.

The voluntary nervous system is to the involuntary nervous system as

the somatic nervous system is to the autonomic nervous system

Which of the following best describes the event that triggers an action potential in a neuron?

threshold stimulus

Which choice best characterizes K+ leakage channels?

transmembrane protein channels that are always open to allow K+ to cross the membrane without the additional input of energy

The generation of an action potential in a neuron requires the presence what type of membrane channels?

voltage-gated channels

Which of the following membrane ion channels open and close in response to changes in the membrane potential?

voltage-gated channels