nervous system ch 12: nervous tissue

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Where are interneurons located?

(CNS) brain and spinal cord.

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

remember classification of neurons picture slide 18 nervous tissue

...

interneurons make up ___ % of our neurons

99%

If acetylcholinesterase became mutated and nonfunctional, what would be the immediate result?

Acetylcholine would build up in the synaptic cleft.

If a drug was developed that interfered with the proper functioning of the microtubules found within the axons of neurons, how would you expect this to impact axonal transport processes?

Both anterograde and retrograde transport processes would cease.

The enzyme choline acetyltransferase catalyzes the reaction between acetyl-CoA and choline resulting in the formation of the neurotransmitter acetylcholine. This enzyme is produced within the cell body of neurons, but the synthesis of acetylcholine occurs within the axon terminals. Which statement best describes the axonal transport mechanism associated with this process?

Choline acetyltransferase is transported in the anterograde direction.

Line cavities in brain and spinal cord Part of choroid plexus, which produces cerebrospinal fluid

Ependymal cells

does electrical synapse work fast or slow?

Fast: no synaptic delay in passing electrical signal

Nonexcitable, support cells found in CNS and PNS Smaller, but far outnumber neurons; account for about half the volume of nervous system

Glial cells (neuroglia)

The event that occurs when the inside of a cell becomes more negative than the resting membrane potential is called _____

Hyperpolarization

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

K+/K+

brain tumors arise from:

Meninges (protective membranes of CNS) Metastasis from nonneuronal tumors in other organs Glial cells that are mitotically active throughout life

Small cells that wander CNS and replicate in infection Phagocytic cells ofthe immune system Engulf infectious agents and remove debris

Microglia

where is signal received by the postsynaptic neuron

Most commonly with one of its dendrites

The threshold is reached when the ______ ions flow into the cell.

Na+

Which of the following membrane transporters are present throughout the membrane of a neuron?

Na+/K+ pumps potassium leak channels sodium leak channels

The nerve impulse has the voltage-gated ______ channels opened first followed by the opening of the voltage-gated ______ channels.

Na+; K+

Elongated, flat cells that ensheath PNS axons with myelin Allows for faster action potential propagation

Neurolemmocytes (Schwann cells)

Large cells with slender extensions Extensions wrap around axons of neurons forming myelin sheath

Oligodendrocytes

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

Suppose that a new virus is discovered that specifically infects motor neurons. Assume that this virus enters neurons in conjunction with choline molecules. Once inside the cell, the virus enters the nucleus and replicates. Which direction describes the axonal transport route taken by this virus?

Retrograde transport

Which describes the propagation of depolarization down an axon?

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

If demyelination occurs, why don't action potentials occur at regions of the axon that were previously myelinated?

These regions lack the appropriate concentration of voltage-gated sodium channels.

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

Two EPSPs in proximity to each other

Membrane pumps require ______ energy.

a lot of

Action potentials are always propagated along an axon at the same ______ but ______ can vary depending on the strength of the stimulus.

amplitude; frequency

The nerve impulse causes ______ in the number of calcium ions that enter the synaptic knob.

an increase

have dendrites but no axons

anaxonic neurons

The voltage-gated potassium channels ______ during repolarization.

are open

Which glial cell occupies the space of dying neurons?

astrocyte

type of glial cells: (star-shaped cells) Have processes that end in perivascular feet Most abundant glial cell in CNS

astrocyte

Help form blood-brain barrier by wrapping feet around brain capillaries Regulate tissue fluid composition (chemical environment around neurons) Form structural support for nearby neurons• Assist neuronal development Occupy the space of dying neurons

astrocytes

______ are star shaped.

astrocytes

The myelin sheath covers ______.

axon

A nerve is a bundle of parallel

axons

Cytoplasm within an axon is called ______.

axoplasm

A synapse is a junction ______.

between a neuron and another cell

Unipolar neurons start out as ______ neurons during development.

bipolar

one dendrite and one axon• Limited number; e.g., in retina of the eye

bipolar neurons

Controls which substances have access to brain

blood-brain barrier of astrocytes

Many excitatory neurotransmitters cause the opening of channels that allow for the flow of ______.

both Na+ and K+

The central nervous system is made of the____ and _____spinal .

brain and spinal

Which are components of the central nervous system?

brain and spinal cord

At the synaptic knob, voltage-gated ______________ channels open, thereby stimulating the synaptic vesicles to release their neurotransmitters by exocytosis.

calcium

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

calcium

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

Soma is another name for the ______.

cell body

______ ______ leads to synaptic knobs in CNS

central process

The 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

______ synapses are far more common than electrical synapses

chemical

Presynaptic neuron's axon terminal produces signal Postsynaptic neuron receives signal

chemical synapse

Synapses are classified as ______.

chemical synapses and electrical synapses

produces cerebrospinal fluid

choroid plexus

The total length of the axon is called the ______ segment.

conductive

The main activity of the ______ is the propagation of an action potential along the axolemma.

conductive segment

______ is the type of neuronal circuit that is made when multiple impulses come together at a single postsynaptic neuron.

converging circuit

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

decrease

A positive change in the membrane potential is called ______.

depolarization

Neurotransmitter ______ across cleft and binds to postsynaptic receptors

diffuses

Another way for the neurotransmitter to be removed from the synaptic cleft is by ______ where there is uptake by surrounding glial cells.

diffusion

Parallel-after- _______ circuits have several neurons processing the same information at one time.

discharge

A message traveling from one presynaptic neuron to multiple postsynaptic neurons is an example of a ______ circuit.

diverging

Glial cells ______ transmit electrical impulses.

do not

Creating and transmitting _____ currents is central to the function of neuron physiology.

electrical

what are the two kinds of synapse

electrical and chemical

A difference in the number of charged particles between two sides of the membrane forms a(n) ______.

electrical gradient

Presynaptic and postsynaptic neurons bound together by gap junctions

electrical synapse

The lining ventricles of the brain is a location of ______.

ependymal cells

which cells have cilia to propel and circulate

ependymal cells

Neurotransmitter molecules released from vesicles of synaptic knob into cleft Neurotransmitter diffuses across cleft and binds to postsynaptic receptors Binding of neurotransmitter to receptor initiates postsynaptic potential (a graded potential)

events of synaptic communication

______ is responsiveness to a stimuli.

excitability

Which of the following are characteristics of neurons?

extreme longevity excitability amitotic secretion conductivity

An increase in the response of a postsynaptic neuron to a neurotransmitter is known as ______.

facilitation

True or false: A neuromodulator is another name for a neurotransmitter.

false

______ classification according to the direction they propagate action potentials

functional

Presynaptic and postsynaptic neurons bound together by ____ ______

gap junctions

Protect and nourish neurons Provide physical scaffolding for nervous tissue Guide migrating neurons during development Critical for normal function at neural synapses

glial cells

____ cells are Capable of mitosis

glial cells

____ cells protect and nourish neurons

glial cells

Blood-brain barrier decreases effectiveness of chemotherapy

gliomas

Treatment consists of radiation or surgery

gliomas

_____ grow rapidly and are highly malignant

gliomas

A potential that is a temporary change in membrane potential which lasts only as long as the stimulus that causes it and can vary in size is called a potential.

graded potential

Binding of neurotransmitter to receptor initiates postsynaptic potential: what kind of potential?

graded potential

glial cells account for about ___ the volume of the nervous system

half

Glial cells are found ______.

in both the central and peripheral nervous systems

Action potentials occur ____________________________.

in the unmyelinated regions of an axon

The voltage-gated sodium channels ______ during repolarization.

inactivated

The electrical gradient in a resting neuron is such that the _____ of the cell is negative relative to the ______

inside, outside

(association neurons) Receive, process, and integrate information from many other neurons Communicate between sensory and motor neurons• Located within CNS Generally are multipolar

interneurons

Neuronal pools are made of ______.

interneurons

neurons make up a network with ____ in between the different neurons

interneurons

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

into; positive

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

A larger axon transmits an impulse ______ than a smaller axon.

larger

Graded potentials result from the opening of ________________.

ligand-gated channels

The myelin sheath is made of a high percentage of ______.

lipids

Engulf infectious agents and remove debris

microglia

Cells that wander through the CNS and replicate in response to infection are called _____

microglial

______ act as phagocytes.

microglial cells

The brain interprets the increased frequency of nerve signals as a ______ stimulus.

more intense

(efferent neurons) Conduct output from CNS to somatic and visceral effectors All are multipolar

motor neurons

If a neuron has many dendrites and a single axon, it is called a(n) ______ neuron.

multipolar

Most motor neurons are ______.

multipolar

many dendrites and one axon most common type

multipolar

Oligodendrocytes create the ____ sheath in the central nervous system.

myelin

The presence of a ______ sheath increases the rate of impulse conduction.

myelin

several layers of membrane of glial cells

myelin

Oligodendrocytes Extensions wrap around axons of neurons forming ______ _____

myelin sheath

process of wrapping an axon with myelin

myelination

A cablelike bundle of axons in the peripheral nervous system is called a ______.

nerve

A ______ is the propagation of an action potential along an axon.

nerve impulse

What is the primary tissue of the nervous system?

nervous tissue

Neuronal pools are also called ______.

neuronal pathways neuronal circuits

Nervous tissue is composed of glial cells and ______

neurons

Neuromodulation alters the response of ______ to neurotransmitters.

neurons

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 neuron cell body houses both the ______ and the cytoplasm.

nucleus

_____ are large cells that ensheath many different axons.

oligodendrocytes

______ ______ splits into several receptive dendrites

peripheral process

microglia are ______ cells of immune system

phagocytic

receives signal

postsynaptic neuron

The sequential opening of voltage-gated sodium channels is followed by the sequential opening of voltage-gated _____ channels.

potassium

An inhibitory postsynaptic potential results from the opening of____________________.

potassium and/or chloride channels

Voltage is a measure of relative _____ energy.

potential

axon terminal produces signal

presynaptic neuron

Propagation of depolarization only flows away from the cell body towards the synaptic knob because ______.

previous regions in the axon have sodium channels in the inactive state

Membrane molecules that use the energy of ATP to move ions against a concentration gradient are called ______

pumps

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

receptive

can regulate potassium concentration

regulate tissue fluid composition of astrocytes

The following information best describes the _____________ phase of an action potential.

repolarization

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

repolarization

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

resting membrane potential

The function of a neuron is dependent on ______.

resting membrane potentials changing

Some antidepressant drugs work by blocking the_____ of serotonin.

reuptake

The removal of neurotransmitters from the synaptic cleft by transport into the synaptic knob is known as ______.

reuptake

The repetitious nature of a ______ circuit ensures that we continue breathing while we are asleep.

reverberating

Arranged around neuronal cell bodies in a ganglion Electrically insulate and regulate the exchange of nutrients

satallite cells

Glial cells of the PNS:

satellite cells and neurolemmocytes

afferent neurons Conduct input from somatic and visceral receptors to CNS Most are unipolar (a few bipolar)

sensory neurons

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

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

by number of processes coming off soma

structural classification

place where a neuron connects to another neuron or an effector

synapse

small fluid-filled gap between the two neurons

synaptic cleft

time it takes for all of these events

synaptic delay

"An action potential either happens or it doesn't." This statement could also be called ______.

the all or none law

In retrograde transport, substances are moved ______ the cell body.

toward

Vesicles involved in retrograde transport are moving ______ the cell body.

toward

True or false: Facilitation and inhibition may be caused by changes in either the presynaptic neuron or the postsynaptic neuron.

true

True or false: Graded potentials vary in size depending on the stimulus.

true

True or false: Voltage-gated sodium ion channels are closed initially and the membrane potential is -70 mv.

true

______ neurons have a single, short neuron process that emerges from the cell body and branches like a T.

unipolar

one process extends from cell body Splits into two processes

unipolar neurons (pesudounipolar)

during synaptic communication: where are neurotransmitter molecules released from?

vesicles of synaptic knob into cleft

The measure of the difference in electrical charge between two areas is called a _____

voltage

If a subthreshold value is reached on an axon membrane, an action potential ______.

will not occur


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