Chapter 11

The intracellular fluid is considered to be electrically neutral because

there are the same number of positively and negatively charged ions.

True or false: Three factors that generate the resting membrane potential include diffusion of ions across a membrane, a selectively permeable membrane, and the electrical attraction of oppositely charged ions.

true

Sodium is more concentrated in the _____ fluid than in the _____ fluid.

extracellular, intracellular

The ion ______ is more concentrated in the extracellular fluid.

sodium

The intracellular fluid has essentially the same number of positive and negative charges and is therefore electrically_____

neutral

The role of the Na+-K+ pump in membrane potential regulation is that it ______.

reestablishes correct ion distribution, compensating for ion leakage

The cell body of a neuron is also known as the

soma

Which type of neuroglia helps promote and regulate synapse formation?

Astrocyte

Explain why Na+ has little effect on establishing the resting membrane potential?

At rest, the membrane is relatively impermeable to Na+ because there are few Na+leak channels.

The brain and spinal cord are the two components of the

Central Nervous System

Predict the effects on membrane potential if the membrane's permeability to Cl- increases.

Cl- would diffuse into the cell, causing a hyperpolarization.

Which factors contribute to the generation of the resting membrane potential? Select all that apply.

Diffusion of ions down their concentration gradients through the membrane Selective permeability of the membrane, allowing some ions to pass more easily than others The electrical attraction of cations and anions to each other

Predict the effect of increasing a membrane's permeability to K+ on membrane potential.

K+ will diffuse out of the cell, causing a hyperpolarization

The sodium-potassium pump is responsible for what portion of the resting membrane potential?

Less than 15 mV

Which statement below best describes why Na+ is highly concentrated outside of neurons and K+ is concentrated within neurons?

Na+ and K+ are actively pumped across the membrane in opposite directions by Na+/K+ pumps utilizing ATP.

When Na+ channels open, what happens to the Na+ ions?

Na+ diffuses into the cell

Explain why Na+ ions diffuse into the neuron when the Na+ channels open.

Na+ is more concentrated outside the cell than inside; hence, the concentration gradient causes diffusion into the cell.

Predict the effect of increasing a membrane's permeability to Na+ on membrane

Na+ will diffuse into the cell, causing a depolarization.

What is responsible for concentrating K+ inside and Na+ outside of neurons?

Na+-K+ pumps

The category of cells of the nervous system that support and protect neurons are called_________ cells.

Neuroglia

What is the name of the gaps found between segments of myelin along an axon?

Nodes of Ranvier

After a nerve cell responds to a stimulus, the period of time when the cell can not respond again, regardless of the strength of stimulus, is called the ____ refractry period

absolute

Identify the statements that are true regarding the nature of the large proteins found within neurons. Select all that apply

They are synthesized inside the cell. They do not readily diffuse through the membrane. They are negatively charged.

In order for an action potential to occur, a minimum membrane potential called the must be reached.

They leave the cell

True or false: Three factors that generate the resting membrane potential include diffusion of ions across a membrane, a selectively permeable membrane, and the electrical attraction of oppositely charged ions.

True

Identify why the membrane becomes hyperpolarized following the repolarization phase of an action potential.

Voltage-gated K+ channels remain open for a short period of time after reaching RMP; allowing K+ to diffuse out of the cell

What type of potential is irreversible?

action

What type of potential is non-decremental?

action potential

The nervous system transfers information from one part of the body to another by using

action potentials

raveling waves of excitation moving down an axon are referred to as _

action potentials

Large, negatively charged proteins inside the cell _____ readily diffuse across the neuron membrane

cannot

Large, negatively charged proteins inside the cell _____ readily diffuse across the neuron membrane.

cannot

The spinal cord and brain comprise the ___________ nervous system.

central

True or false: During the absolute refractory period a neuron will be re-stimulated if it reaches threshold.

false

True or false: Once achieved, a single action potential can travel the distance of the entire axon of the neuron

false

The speed of an action potential along myelinated axons is ______ the speed of an action potential along an unmyelinated axon

faster than

Some protein channels in a cellular membrane are able to open or close in response to stimuli; because of this characteristic, these channels are called ______ channels

gated

The general class of cells in the nervous system that protect nerve cells and help in their functioning are called _______ cells

gilia

Cells of the nervous system that support and protect the neurons are called

glial cells

An increase in a membrane's permeability to K+ will result in ______ of the membrane.

hyperolization

At rest, the neuron plasma membrane is relatively ______ to Na+; therefore, Na+ does not influence the resting membrane potential very much.

impermeable

An axon hillock transitions into the ______ segment of an axon.

initial

The beginning of the axon is called the ________ segment

initial

A negative membrane potential indicates that the area with a more negative charge is on the ______ of the membrane.

inside

Potassium ions and negatively charged proteins are more concentrated ______ the cell.

inside

Potassium has a much higher concentration in the _____ fluid than in the _____ fluid.

intracellular, extracellular

A synapse is a

junction between two cells

When the membrane potential decreases, the inside of the membrane becomes _____ negative. This is called ______.

less, depolarization

A multipolar neuron has ______ dendrite(s)

many

The sodium-potassium pump plays a _____ role in maintaining resting membrane potentia

minor

A neuron with one axon and multiple dendrites is called a _______ neuron.

multipolar

Action potentials (nerve messages) are able to travel faster along ______ axons.

myelinated

Action potentials are conducted more rapidly along ______ axons.

myelinated

If the area just inside the membrane of a cell is more negative than the outside, the resting membrane potential will have a ______ value.

negative

The intracellular fluid has essentially the same number of positive and negative charges and is therefore electrically

neutral

Glial cells that form myelin sheaths within the CNS are the ______.

oligodendrocytes

The plasma membrane has opposite charges arranged across the membrane and is thus said to be _____

polar

When opposite charges are arranged on opposing sides of a membrane, the membrane is said to be ______.

polarized

During an action potential, repolarization is due to _____ ions leaving the cell

potassium

Inside excitable cells at rest, you'll find high concentrations of ______ ions and negatively charged proteins.

potassium

The ion that is in a higher concentration in the intracellular fluid compared to the extracellular fluid is_______.

potassium

The plasma membrane is more permeable to _____ and chloride and much less permeable to _____.

potassium, sodium

The purpose of the absolute refractory period is to

prevent action potentials from being generated in reverse direction

A period of time after a nerve cell has responded to a stimulus in which it cannot be re-excited by a threshold stimulus is called a(n) ______ period.

refactory

After a nerve cell responds to a stimulus, the period of time when the cell cannot respond again except to an unusually strong stimulus is called the Blank 1Blank 1 absolute, Incorrect Unavailable _____ refractory period.

relative

The difference in electrical charge across the plasma membrane in an unstimulated cell is called _____ ____ the potential.

resting membrane

A cell is not stimulated but it does contain an electrical charge difference across its membrane. This charge difference is its ______.

resting membrane potential

Which term best describes the concentration gradients for sodium and potassium on an excitable cell?

steep

A junction between a neuron and another cell is called a(n)

synapse

In order for local potentials to trigger an action potential, the membrane must reach a level called the ______.

threshold

Once stimulated, a single action potential

travels only a short distance before stimulating another action potential

True or false: There is a significant difference in concentration between the intracellular concentration of sodium and the extracellular concentration of sodium.

true

Neuroglial cells that aid in the production of cerebrospinal fluid are the _______ cell

ependymal

The sodium-potassium pump moves the ions in which direction?

Sodium out of the cell and potassium into the cell

Identify the functions of astrocytes.

Synthesis of neurotransmitters Promotion of the formation of synapses Regulation of synaptic activity

Explain the importance of the absolute refractory period in the propagation of action potentials.

The absolute refractory period ensures one-way propagation of action potentials.

Select the item that best defines the soma of a neuron

The cell body of a neuron

The highly branched cytoplasmic extensions of a neuron cell body that are specialized to receive input and conduct signals toward the cell body are called

dendrites

Branched cytoplasmic extensions of the neuron that receive input and transmit signals toward the cell body are________

dentrites

When the resting membrane potential shifts to a more positive value, this is referred to as

deplorization

An increase in a membrane's permeability to Na+ will result in ____ of the mebrane

depolarization

During an action potential, an increase in membrane permeability to Na+ leads to a(n) _______ followed by an increase in permeability to K+ that leads to a(n) ______ of the membrane and a slight afterhyperpolarization.

depolarization, repolarization

When the neuron membrane becomes more positive than the resting membrane potential, it is said to be ______.

depolarized