Nervous System Chapter 12

The voltage-gated potassium channels are ________ during repolarization

open

The type of neuronal circuit in which several neurons process the same information at one time is a _______ circuit.

parallel-after-discharge

voltage represents _____ energy.

potential

A __________ transmits an impulse through its axon toward the synapse.

presynaptic neuron.

Propagations of depolarization only flows away from the cell body towards the synaptic knob because _________

previous regions in the axon have soidum channels in the inactive state.

An axon is either incapable of generating an action potential or requires a larger than normal stimulus during the ___________ period.

refractory

The opposition to the movement of electrical charge is known as __________

resistance.

The relative difference in charge across the plasma membrane of a resting neuron is known as the _____________

resting membrane potential

Na+ and K+ leak channels and Na+/K+ pumps on the neuron are responsible for establishing and maintaining the _______.

resting membrane potential (RMP)

The function of a neuron is dependent on ___________________.

resting membrane potentials changing

The flow of _______ ion is the most common cause of depolarization.

sodium

An action potential cannot be initiated during the absolute refractory period because ________.

sodium channels are inactivated, and thus cannot open.

A change in membrane potential insufficient to cause an action potential is known as __________.

subthreshold value or resting potential.

Neurons integrate multiple synaptic inputs by the process of _________

summation

There would be no net movement of K+ ions through an open K+ leak channel when ________

the electrical chemical gradient and chemical gradient balance one another

Which describes the propagations of depolarizaion down an axon?

the flow of Na+ to downstream regions causes depolarization of adjacent regions.

The all-or-none law refers to the fact that action potentials will only occur if the initial segment reaches __________.

threshold

In the initial segment, an action potential is generated if the membrane potential reaches the _____________.

threshold potential

In the ______ of a neuron, you would be likely to find voltage-gated calcium channels.

transmissive segment

T/F There are more potassium leak channels in a neuron's membrane than sodium leak channels.

true

A graded potential is one that

varies in size depending on the magnitude of the stimulus (larger voltage change for stronger stimulus).

___________ are not commonly found in the receptive segment of a neuron.

voltage-gated ion channels.

Action potentials are generated by teh opening of ____________ gated channels and they occur on the _______.

voltage; axon

According to Ohm's law, the currrent is directly related to ____________ and inversley related to _______

voltage; resistance

Place the events of synaptic transmission from earliest to latest

1. action potential reaches syanptic knob 2. voltage-gated calcium channels open 3. calcium enters the synaptic knob 4. calcium triggers exocytosis of vesicles 5. the neurotransmitter diffuses across the synaptic cleft 6. the neurotransmitter binds to postsynaptic receptors.

The order of events of EPSP are as follows:

1. the excitatory neurotransmitter binds to the chemically gated cation channel 2. more Na+ enters the postsynaptic cell than K+ leaves 3. the inside of the cell becomes more positively charged. 4. the local current of Na+ becomes weaker as it moves towards the axon hillock.

The chain of events of chloride-based IPSP in order from earliest to latest:

1. the inhibitory neurotransmitter binds to postsynaptic chemically gated chloride channels. 2. Chloride moves from outside of the cell to inside of the cell. 3. The inside of the postsynaptic cell becomes more negative. 4. the local chloride current becomes weaker as it moves away from the neurotransmitter binding site.

the voltage-gated sodium channels undergo changes in activity during the depolariztion phase of an action potential. Place these in order from first to last.

1. the membrane potential is -70mv 2. sodium ions flow within the neuron. 3. the membrane potential becomes more positive 4. voltage-gated sodium ion channels open.

______ is a type of membrane transport protein that increases the potential energy across a membrane.

A pump.

the leak of potassium ions tends to drive the membrane potential to -90mV, and yet the normal resting membrane potetnial of a neuron is around -70 mV. What is the reason for this difference?

A small leak of sodium ions make the RMP more positive This is because when K+ leaves the cell, it becomes more negative due to the larger negative organic molecules and ions remaining in the cell

_________ are the most common.

Chemical synapses

Numerous ______ must be generated and arrive at the initial segment at nearly the same moment if a threshold is to be reached.

EPSPs

_________ allow ions to pass from one neuron to the other.

Electrical Synapses

Gap junctions are found in _________.

Electrical synapses.

T/F Voltage-gated potassium and soidum channels are present throughout the membrane of a neuron.

False

Repolarization is due to the opening of the voltage-gated ____________ and the subsequent movement of _________ out of the cell.

K+; K+

______ is kept inside of the cell, and ________ is kept outside of the cell.

K+; Na+

threshold is reached when enough _______ ions flow into the cell.

Na+

The nerve impulse ahs the voltage-gated ___________ channels opened first followed by the opening of the voltage-gated ___________ channels.

Na+; K+

__________ is the return of polarity from positive back to negative (the RMP)

Repolarization

The type of neuronal circuit that uses feedback to produce a repeated, cyclical stimulation of the circuit is a ____________ circuit.

Reverberating

T/F In an electrical synapse, there is essentially no synaptic delay.

True

T/F Most voltage-gated ion channels are closed until the electrical potential across a membrane changes.

True

T/F Voltage-gated sodium ion channels are closed initially and the membrane potential is -70mV.

True

T/F pre and postsynaptic neurons are bound together by gap junctions in electrical synapses.

True

t/f in most cases, a single EPSP is not sufficient to cause a neuron to reach the threshold potential.

True.

___________ channels are unique in that they have three states; resting, activation, and inactivation.

Voltage-gated channels

____________ and are the cause of hyperpolarization in an action potential.

Voltage-gated potassium channels remain open

Membrane pumps require ________ energy.

a lot of

Which occurs first, the absolute refectory period or the relative refractory period?

absolute refractory period

the relative refractory period occurs _________ the absolute refractory period.

after

refractory period occurs immediately ___________ an action potential.

after.

current is measured in ______

amps

The nerve impulse causes ________ in the number of calcium ions that enter the symaptic knobs.

an increase

Local ________ like lidocaine work by inhibiting impulse propagation.

anesthetics

Voltage-gated sodium channels __________ during the relative refractory period.

are returning to the resting state

A synapse is a junction ___________.

between a neuron and another cell.

The presence of ____________ ions causes the synaptic vesicles to bind to the membrane, allowing neurotransmitters to be released.

calcium

____________ use neurotransmitters.

chemical synapses.

A _________ is a channel that is usually closed but which opens in response to binding a neurotransmitter.

chemically gated channel.

The total lenght of the axon is called the _______ segment

conductive

If a prolonged stress in smooth muscle occurs, it responds by ___________, which is called the ___________ response.

contracting then relaxing; stress-relaxation response

the event that occurs when the inside of the cell becomes more positive than the resting membrane potential is called ____________.

depolarization

A positive charge in the membrane potential is called ________

depolarization it is the gain of positive charge as Na+ enters through voltage-gated Na+ channels

Membrane channels provide the means to move a substance _________ its concentration gradient

down.

Synapses are classified as ______

electrical and chemical synapses

the movement of charged particles (or current) is _________ that can be harnessed to do ______.

electrical energy; work

A difference in the number of cahrged particles between two sides of the membrane forms a(n)__________

electrical gradient

creating and transmitting _________ currents is central to the function of the neuron physiology.

electrical.

The location of a larger concentration of sodium ions are ___________

extracellular

t/f The relative charge across a neuron's plasma membrane is negative outside the cell relative to the inside of the cell.

false

The flow of sodium ions through sodium channels is best described as __________.

from outside the cell to inside the cell.

the __________ the resistance, the ________ the current.

higher; lower

Immediately following the repolarization of an action potential, the membrane undergoes _______ before returning to the resting membrane potential.

hyperpolarization

The event that occurs when the inside of a cell bbecomes more negative than the resting membrane potential is called ___________.

hyperpolarization

negatively charged proteins and other large organic molecules are found __________

in greater amounts inside of the neuron

The voltage-gated sodium channels are __________ during repolarization.

inactivated

__________ is what underlies the absolute refractory period.

inactivation of potassium channels.

Many local anesthetics prevent the transmission of pain by ___________.

inhibiting voltage-gated sodium channels.

the changes in membrane potential associated with both EPSP and IPSP inputs are "added" in the _____________ to determine if an actino potential is initiated and the threshold is reached.

initial segment

If summated PSPs reach threshold, an acition potential begins first in the _______

initial segment.

the electrical gradient ina resting neuron is such that the ____________ of the cell is negative relative to the _______.

inside; outside/interstitial

the location of a larger concentration of organic ions are found _________

intracellular

During an action potential, voltage-gated potassium channels open after voltage-gated sodium channels. The effect this has on the membrane potential is ___________.

it becomes less positive and more negative.

Channels that allow an ungagted flow of specific ions from regions of high concentration to regions of low concentration are called ________ channels.

leak

RMP is measured in ___________

millivolts

When K+ moves out of the cell down its concentration gradient, the cell becomes more _________

negative this is because more positive ions are diffusing out of the cell and larger negative particles (phosphate ions and organic proteins) remain inside of the cell.

A _________ is the propagation of an action potential aong an axon.

nerve impulse

Which of the following pumps can you find in the plasma membrane?

- Ca2+ - Na+/K+

which membrane transporters are present throughout the membrane of a neuron?

- K+ leak channels - Na+/K+ pumps - Na+ leak channels

Which ions have leak channels on the plasma membrane?

- Na+ - K+

Before a vesicle of neurotransmitter can be released which of the following must occur

- action potential reaches synaptic knob - voltage-gated calcium channel open

An inhibitory neurotransmitter may cause the opening of a ______ channel.

- chloride - potassium

The three main functions of the nervous system are ____________

- collect information - process and evaluate information - initiate response to information

Which of the following would be likey to cause hyperpolarization of a neuron?

- opening of a chemically gated chloride channel - opening of a voltage-gated potassium channel.

Which of the following would likely cause depolarization of a neuron?

- opening of a chemically gated sodium channel - opening of a voltage-gated sodium channel

_______________ to help return the membrane potential to the resting state following hyperpolarization.

- voltage-gated potassium channels close - na+/K+ pumps restore gradients

__________ is a typical resting membrane potential for a neuron.

-70 mV

Initially, the voltage-gated Na+ channels are closed and the membrane potential is _________ mV. As Na+ flows in the membrane potential changes to __________ mV and the threshold is reached.

-70; -55

If only K+ leak channels were present in neurons, the loss of K would result in an RMP with a value of ____________

-90mV