nervous system ch 12: nervous tissue
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