Neuron homework

It is necessary that the neurotransmitter molecule is eliminated after each stimulation event. Its removal can occur by (1) ____________ , in which the neurotransmitter is chemically ____________ in the ____________ , and (2) ____________ , in which the neurotransmitter is reabsorbed by a neurotransmitter ____________ in the membrane of the ____________ neuron. These neurotransmitters are "recycled" once packaged into another ____________ for reuse.

- Degradation - Inactivated - Synaptic cleft - Reuptake - Transport protein - Presynaptic - Synaptic vesicle

The _____ segment includes both dendrites and the cell body, which are the regions of the neuron that receive stimuli to excite the neuron. Channels in this region are _____ ; no significant numbers of _____ channels are present.• The _____ segment is composed of the axon hillock. This segment contains voltage-gated channels.• The _____ segment is equivalent to the length of the axon. It contains voltage-gated channels.• The _____ segment includes the synaptic knob and contains voltage-gatedchannels and _____.

- Receptive - Chemically gated - Voltage-gated - Initial - Conductive - Transmissive - Pumps

Between each presynaptic and postsynaptic neuron is a ____________ that is the fluid-filled space between them. Each presynaptic neuron releases ____________ that binds with receptors in the ____________ segment of a postsynaptic neuron. The ____________ channels of the receptive segment open when these molecules bind. Specific ions then cross the membrane, initiating a ____________ potential in the postsynaptic neuron. This local potential is a small voltage change in the ____________ potential.Graded potentials that occur in postsynaptic neurons are specifically called ____________ potentials.

- synaptic cleft - neurotransmitter - receptive - gated - graded - resting membrane - postsynaptic

Microglia

-Cells of the lymphatic system -Marcrophages of the CNS

Select all of the following that would increase the magnitude of a postsynaptic potential.

-More neurotransmitter released from the presynaptic neuron -More chemically gated channels open in the postsynaptic neuron

Astrocytes

-Most abundant CNS glial cell -Involved in neurogenesis, scar formation, and BBB maintenance

satellite cells

-PNS cells that surround and insulate the somas

Select all that are true of oligodendrocytes.

-They are glial cells found in the CNS. -They can form myelin around several axons simultaneously. -They help form a myelin sheath around CNS axons.

Inhibitory Neurotransmitter Actions

-binds to a chemically gated potassium ion -binds to a chemically gated chloride ion -potassium moves down its concentration gradient out of the neuron -chloride moved down its concentration gradient into the neuron

Excitatory Neurotransmitter Actions

-binds to a chemically gated sodium channel - sodium moves down concentration gradient into the neuron -the inside of the neuron becomes more positive

Select all that apply. The cell membrane provides resistance, which can be altered by

-voltage-gated ion channels opening or closing.voltage-gated ion channels opening or closing. -additional leakage ion channels being inserted into the cell membrane.

Place the items in the correct order for an IPSP from beginning to end. Not all items will be used.

1. An inhibitory neurotransmitter binds to chemically gated K+ channels 2. K+ channels open 3. K+ flows out of the neuron 4. The inside of the neuron becomes more negative 5. The IPSP propagates toward the axon hillock

Place the following structures in the order that an electrical impulse would travel beginning with the postsynaptic membrane.

1. Dendrite 2. Axon hillock 3. internode 4. neurofibril node 5. synaptic knobs

Place the items for an EPSP in the correct order from beginning to end. Not all items will be used.

1. Excitatory neurotransmitter released from presynaptic neuron 2. Neurotransmitter binds to chemically gated sodium channels 3. Sodium channels open 4. Sodium flows into neuron 5. Inside of neuron becomes more positive 6. This EPSP propagates toward axon hillock

EPSP and IPSP ____________ potentials are local currents of ions that move along the plasma membrane toward the initial segment area of the ____________ . Graded ____________ potentials are added together in the initial segment; this process is called ____________ . The initial segment, by adding postsynaptic potentials, determines if a(n) ____________ potential is reached.This potential is ____________ mV. This is a change of ____________ mV from the RMP. When this threshold is reached, it initiates the opening of ____________ channels and the generation of a(n) ____________ potential that will travel along the axon.

1. Graded 2. axon hillock 3. postsynaptic 4. summation 5. threshold membrane 6. -55 7. +15 8. voltage-gated 9. action

The relative difference in charge across a plasma membrane is the ____________ in an inactive excitable cell. A ____________ is used to measure the voltage difference across the plasma membrane. This is done by placing one microelectrode into the ____________ and the other microelectrode outside the neuron into the ____________ . The RMP has a value that is typically ____________ millivolts. More positive ions reside ____________ a neuron than ____________ a neuron when it is at rest.

1. Resting membrane potential 2.Voltmeter 4. Neuron 5. Interstitial fluid 6. -70 8. Outside 9. Inside

When the propagated action potential reaches the ____________ at the end of the axon, ____________ channels are triggered to ____________ . Calcium ions move fromthe ____________ down their concentration gradient. The entry of calcium triggers a series of events, resulting in fusion of ____________ with the neuron plasma membrane. Neurotransmitter is subsequently released into the ____________ by exocytosis. Approximately 300 vesicles are released per action potential.

1. Synaptic knob 2. voltage-gated calcium 3. open 4. IF into the synaptic knob 5. synaptic vesicle 6. synaptic cleft

The transmissive segment is the ____________ . The main activity that occurs at the transmissive segment is the release of neurotransmitter from ____________ . Prior to the arrival of the action potential, ____________ embedded in the plasma membrane of a synaptic knob establish a ____________ concentration gradient by pumping it out to the extracellular fluid. Consequently, there is more calcium ____________ of the synaptic knob than ____________ it.

1. Synaptic knob 2.synaptic vesicle 3. calcium pumps 4. calcium 5. outside 6. inside

A synapse is the specific location where ____________ is functionally connected to either another neuron or ____________ . There are two types of synapses in the human body: chemical synapses and electrical synapses. Most synapses within the nervous system are ____________ synapses.

1. a neuron 2. an effector 3. chemical

Pumps move substances _______ a concentration gradient, a process that requires energy. Channels instead provide the means to move a substance ______ a concentration gradient. Neurons contain the following major types of channels:• Channels that are always open, allowing continuous diffusion of a specific ion from a region of ______ concentration to a region of _____ concentration are leak channels.• Channels that are normally closed that open in response to the binding of a __________ are chemically gated channels. When open, they allow a specific ion to _______ across the plasma membrane.• Channels that are normally closed, but open in response to changes in _________ across the plasma membrane are voltage-gated channels. When open, they allow a specific ion to diffuse across the membrane.

1. against 2. with 3. high 4. low 5. neurotransmitter 6. diffuse 7. electrical charge

What is the correct order for the events of neurotransmitter release from the synaptic terminal?1. Extracellular Ca2+ enters terminal and binds to sensor protein in the cytoplasm2. Exocytosis of neurotransmitter into synaptic cleft3. Action potential reaches axon terminal4. Ca2+-protein complex stimulates fusion of the docked synaptic vesicle with the plasma membrane5. Voltage-gated Ca2+ channels open

3, 5, 1, 4, 2

What is produced when depolarization of a cell membrane reaches threshold?

A new action potential is produced.

Oligodendrocytes

Form myelin sheath in CNS

What type of cells produce the myelin sheath in the central nervous system (CNS)?

Oligodendrocytes

Which of the following characteristics of action potentials can vary?

The frequency of action potentials

2. Indicate the summative effect that brings the initial segment closest to threshold.

Two EPSPs in proximity to each other

If extracellular calcium was absent, which would likely be true?

Vesicles containing neurotransmitter would not merge with the plasma membrane.

A recently depolarized area of a cell membrane cannot generate an action potential because of the

absolute refractory period.

In order to maintain the electrochemical gradients for sodium and potassium, ATPase pumps move these ions ____________ their respective gradients.

against

When threshold is reached, depolarization occurs with the same amplitude of potential change. This is known as

all or nothing principle

Which glial cell is starlike in shape and helps form the blood-brain barrier?

astrocytes

The motor division is separated further into a somatic motor division and a(n) ____________ motor division.

autonomic

Substances that cause facilitation of a neuron ____________________________.

cause the neuron to fire that may not under the same circumstances in the absence of the facilitator

Ependymal cells help produce

cerebrospinal fluid.

A resting membrane potential of -70 mV indicates that the ________________.

charges lining the inside of the plasma membrane are negative compared to the charges lining the outside

The voltage-gated Na⁺ channels ______ when the cell reaches +30 mV.

close

Demyelinating diseases cause a(n) ______________ in the conduction velocity of action potentials

decrease

The diffusional movement of sodium and potassium across the membrane is driven at all times by the ____________

electrochemical gradient.

On a graph of an action potential, the small depolarizations that lead to threshold are from

excitatory postsynaptic potentials (EPSPs).

In neurons, protein pumps allow substances to move passively down their concentration gradients. true or false

false

The inside of the cell membrane becomes negative at the time of an action potential. true or false

false

An axon with a large diameter transmits an impulse ____ than an axon with a smaller diameter.

faster

Neurolemmocytes

form myelin sheath in PNS

The afferent or sensory division transmits impulses ____________ .

from peripheral organs to the CNS.

The efferent or motor division transmits impulses ____________

from the CNS out to peripheral organs

ependymal cells

function in the production and circulation of cerebrospinal fluid

When chloride enters the neuron via chemically gated chloride channels, the membrane potential will become more negative than the resting membrane potential. This is called _____________.

hyperpolarization

Action potentials occur ____________________________.

in the unmyelinated regions of an axon

1. When voltage-gated sodium channels are open, sodium flows _____________ the neuron making the inside of the cell more _______________.

into, positive

Resting membrane potential is created as a result of a greater net flow of positive charges from the ____________ .

intracellular fluid to the extracellular fluid.

The diffusion of ____________ into the cell or out of the cell causes a change in membrane potential.

ions

An unmyelinated fiber has voltage-gated ion gates along its entire _____

length

When K⁺ diffuses out of the cell, the cell becomes ______depolarized.

less

Neurotransmitters combine with their receptor sites and cause ____________ -gated ion channels to open.

ligand

Graded potentials result from the opening of ________________.

ligand-gated channels

The cell membrane immediately adjacent to an action potential depolarizes because of

local currents

Which glial cell acts as a phagocyte?

microglial cell

When Na⁺ diffuses into the cell, the cell becomes ____________ depolarized.

more

The peripheral nervous system is further subdivided into an afferent (sensory) division and an efferent ( ____________ ) division.

motor

K⁺ diffusing out of the cell has a _______ feedback effect on the initial depolarization.

negative

Calcium ions diffuse into the cell and cause synaptic vesicles to release ____________ .

neurotransmitter

assume in a laboratory you were able to isolate a neuron and remove the Acetylcholine receptors from the postsynaptic membrane. The substance _________________ would no longer cause facilitation of this neuron.

nicotine

The absolute refractory period assures that action potential propagation is

only in one direction.

The voltage-gated Na⁺ channels ______ when the cell membrane reaches threshold level as a result of a stimulus.

open

Neurolemmocytes produce myelin in the _____ nervous system.

peripheral

Na+ diffusing into the cell causes more Na+ gates to open, which is a _______ feedback loop.

positive

When sodium enters the neuron via chemically gated sodium channels, the membrane will depolarize. Therefore, the membrane potential will become more

positive

Graded potentials that occur in postsynaptic neurons are called ___________ potentials.

postsynaptic

Though potassium and sodium both leak through the membrane at rest, there is a greater diffusional flow of ____________ at rest.

potassium

An inhibitory postsynaptic potential results from the opening of____________________.

potassium and/or chloride channels

Neurotransmitters diffuse from the ____________ terminal across the synaptic cleft.

presynaptic

Graded potentials are produced within the _______________________ segment of a neuron.

receptive

1. _______________ the time between signals sent from the same presynaptic terminal increases the strength of the graded potential. This is an example of ________________ summation.

reducing, temporal

The depolarization causes a _______ that excites the entire membrane.

repetition

The following information best describes the _____________ phase of an action potential. • A membrane potential reading of +10 mV• Inactivated voltage-gated sodium channels• Open voltage-gated potassium channels

repolarization

Another term for the __________ nervous system is the afferent nervous system

sensory

This continues until the traveling ____________ reaches the end of the axon.

signal

Autonomic refers to the controls we are not aware of, like ____________ muscle, cardiac muscles, and glands.

smooth

The electrical and chemical gradients for ____________ are both high during resting membrane potential, which results in a very high electrochemical gradient toward the inside of the cell.

sodium

Normally, sodium and potassium leakage channels differ because ___________________.

sodium ions diffuse through leakage channels into the cell, but potassium ions diffuse through leakage channels out of the cell

Graded potentials are added together at the axon hillock in a process known as _________.

summation

Acetylcholinesterase

the enzyme that breaks down acetylcholine in the synaptic cleft

If all the sodium leakage channels were removed from the cell membrane of a neuron,

the membrane potential would be about -90 millivolts.

An EPSP will cause the postsynaptic membrane

to depolarize.

An action potential at the____ zone causes sodium to diffuse into the cell This results in membrane_____

trigger, depolarization

Depolarizing graded potentials may lead to an action potential. true or false

true

Graded potentials can result from mechanical stimulation or temperature changes. true or false

true

Graded potentials can result from voltage across the plasma membrane. true false

true

Increased permeability of the membrane to sodium results in depolarization. true or false

true

Neurotransmitters are removed from a synapse by degradation and reuptake. true or false

true

Postsynaptic neurons can generate both inhibitory and excitatory postsynaptic potentials simultaneously. true or false

true

Sodium has a higher concentration outside the cell than within. true or false

true

The effects produced by one graded potential can be added onto the effects of another graded potential. true or false

true

The entry of sodium ions into the postsynaptic neuron causes depolarization. true or false

true

The leakage of potassium plays a more significant role in the resting membrane potential than the leakage of sodium. true or false

true

The potential change can vary from small to large depending on the stimulus strength or summation. true or false

true

Action potentials arriving at the presynaptic terminal cause _____-gated calcium channels to open.

voltage

An inhibitory postsynaptic potential (IPSP)

will make it more difficult for the postsynpatic neuron to reach threshold.