neuron
nerve cells
long-lived - a lifetime or more
amitotic - most cannot divide
extremely high metabolism (glucose and O2)
neuroglial cells
do not carry an impuls
scaffolding, insulation and support of neurons
half the total brain mass
internodes
regions between the nodes of Ranvier
underneath the cells
underneath the myelin
nodes of Ranvier
unmyelinated regions
regularly spaced
increase the speed of impulse conduction as impulse will jump from node to node
channels
myelin
lipid produced by Schwann cells
protects and electrically insulates some axons
increases speed of neural impulse conduction
synaptic end bulb
in the axonal terminals
bulbs at the end of the axon that links to dendrites of another nerve or cell
axonal terminals
specialized area to send signal to next neuron
axon
conducting component
carries signals away from cell body, one per neuron, can be extremely long or short, branch into axonal terminals
axon hillock
region just outside cell body where signals from dendrites are summed - if enough stimulus is received, an impulse is conducted down the axon
dendrites
receptive regions (receptors)
sends signals to cell body
hundreds per cell body
graded stimuli and threshold
nissl bodies
rough ER
makes proteins
cell body (soma)
biosynthetic center
contains the usual organells and highly functional ER
structure of a neuron
cell body or soma
nissl bodies
dendrites
axon hillock
axon
axonal terminals
synaptic end bulb
ganglia
clusters of neuron cell bodies within the PNS
nuclei
clusters of neuron cell bodies within the CNS
tracts
bundles of neurons in the CNS
nerves
parallel bundles of neurons in the PNS
gyrus/gyri
elevated ridges
sulci
shallow grooves
fissure
deep groves
IPSP
inhibitory post-synapse potential
if there is reduced permeability to Na+ ions or increased permeability of K+ ions, the membrane potential becomes more negative and further from threshold making it less likely that a new action potential will occur
EPSP
excitatory post-synapse potential
if positive ions flow into nerve cell, it moves the membrane towards threshold making it easier to set off a new action potential
absolute refractory period
the period from the opening of the Na+ gate to the closing of the Na+ gate
no new action potentials can be started
nothing can change it
relative refractory period
when K+ gates open & repolarization is occurring
a second action potential can be initiated but only by a stronger than normal stimulus
saltatory conduction
occurs in myelinated axons
impulses jump from one node of Ranvier to the next
allows for faster, more energy efficient transmission
speed of transmission in a large myelinated neuron may reach 100 m/s
synaptic potentiation
repeated use of a synaptic pathway, causes buildup of Ca+ supplies in the region - results in release of more neurotransmitters and easier action potential generation
plays a role in learning and efficiency
coma
not just deep sleep
oxygen usage drops
signal doesn't get through RAS (reticular activating system)
doesn't activate
contusion
bruising of the brain leading to permanent damage
concussion
alteration in brain function due to a blow to the head, can lead to a buildup of tau proteins
structure of neurons
mutlipolar - 3 or more processes, 1 axon, lots of dendrites
bipolar - 2 processes, 1 dendrite, 1 axon
unipolar - single process, cell body placed in center of axon instead of near dendrites
neurons and their functions
sensory neurons - afferent, carry signal TO the CNS
interneuron - within the CNS, creates an association between stimulus and response
motor neurons - efferent, carries OUT response of CNS
motor neurons
efferent, carries OUT response of CNS
interneuron
within the CNS, creates an association between stimulus and response
sensory neurons
afferent, carry signal TO the CNS
bipolar neuron
2 processes
1 dendrite
1 axon
multipolar neuron
3 or more processes
1 axon
lots of dendrites
unipolar neuron
single process
cell body placed in center of axon instead of near dendrites
CNS neuroglial cells
oligodendrites
astrocytes
ependymal cells
microglia
oligodendrites
produce myelin, insulate thick CNS neuron fibers
astrocytes
most abundant and versatile
supports neurons and anchors them to capillaries
control capillary permeability, helping to deliver nutrient to neurons
guide development of young neurons
recycle neurotransmitters, mop up K+
can also influence brain functionin
ependymal cells
line central cavities of brain and spinal cord
form barrier between CNS and central cavities
produces, filters, and circulates CSF
microglia
protect against invasion
immune system is blocked out of CNS - the immune cells of the CNS
membrane ion channels
chemically-gated
voltage-gated
mechanically-gated
chemically-gated channels
opened by binding of a molecule with a receptor
voltage-gated channels
opened when nearby membrane depolarizes
mechanically-gated channels
physical deformation, used by many receptors (hair receptors), manipulation
surface of cerebral hemispheres
gyrus/gyri - elevated ridges
sulci - shallow grooves
fissure - deep groves
frontal lobe
personality
emotions
intelligence
attention
concentration
judgment
body movement
problem solving
speech (speak and write)
parietal lobe
sense of touch (pain, temp, etc.)
distinguishing size, shape, and color
spatial perception/discrimination
visual perception (recognition)
temporal lobe
understanding language
memory
hearing
sequencing
organization
occipital lobe
vision
lobes of the brain
frontal lobe
parietal lobe
temporal lobe
occipital lobe
insula (pyschology)
major wave patterns seen on an EEG
alpha
beta
theta
delta
alpha
8-13 Hz
indicates calm, awake state
beta
14-30 Hz
awake, concentrating or "working" on something
theta
4-7 Hz
common in children, abnormal in adults, can appear when concentrating
delta
4 or less Hz
high amplitude, seen when asleep, sign of brain damage in awake adults (signifies dampening of the RAS or under anesthesia)
types of neurotransmitters
acetylcholine
biogenic amines
amino acids
neuropeptides
purines
acetylcholine
excitatory to skeletal muscles
inhibitory to others
biogenic amines
indolamines - serotonin, histamine
catecholamines - epinephrine, norepinephrine, dopamine
amino acids
excitatory - glutamate
inhibitory - glycine, GABA
neuropeptides
inkephalins, endorphins
purines
excitatory - ATP
inhibitory - adenosine
types of neural integration
serial processing
parallel processing
divergence
convergence
reverberating series
parallel after discharge
serial processing
one neuron stimulates the next, etc. (predictable reflex)
parallel processing
circuits branch
divergence
convergence
reverberating series
parallel after discharge
divergence
one incoming fiber triggers increasing number of neurons down the circuit
convergence
lots of neurons converge to create a strong stimulation or inhibition
reverberating series
fires down a line of neurons but 1 will loop back and refire an earlier neuron
controls rhythmic activity (breathing)
parallel after discharge
cognitive, higher order processes
major fissures in the brain
longtitudinal fissure
transverse fissure
central sulcus
precentral sulcus
postcentral sulcus
lateral sulcus
parieto-occipital sulcus
conduction velocities of neurons (speed)
Group A fibers - large diameter, thickly myelinated, very fast, 150 m/s (300 mph)
Group B fibers - smaller diameter, lightly myelinated, intermediate speed, 100 m/s (30 mph)
Group C fibers - smaller diameter, unmyelinated, very slow, 1 m/s (2 mph or less)
Group A fibers
large diameter, thickly myelinated, very fast, 150 m/s (300 mph)
Group B fibers
smaller diameter, lightly myelinated, intermediate speed, 100 m/s (30 mph)
Group C fibers
smaller diameter, unmyelinated, very slow, 1 m/s (2 mph or less)
Collections of nerve cell bodies outside the central nervous system are called ______________.
ganglia
Meningitis can be caused by infection of the central nervous system by bacteria. Which cells would be most responsible for removing the infection?
microglia
A stimulus traveling toward a synapse appears to open calcium ion channels at the presynaptic end, which in turn promotes fusion of synaptic vesicles to the axonal membrane.
True
An inhibitory postsynaptic potential (IPSP) is associated with _________________.
hyperpolarization
Nerve impulses leading to the brain carry information about cool temperatures on the skin. The nerve fibers sending these signals will most likely belong to which division of the nervous system?
sensory (afferent) division
Which of the following is not a chemical class of neurotransmitters?
nucleic acid
Schwann cells are functionally similar to _____________.
oligodendrocytes
These cells in the CNS have cilia that move in order to circulate cerebrospinal fluid.
ependymal cells
Which of the following describes the nervous system integrative function?
analyzes sensory information, stores information, makes decisions
Which of the following is not a function of astrocytes?
provide the defense for the CNS
During depolarization, the inside of the neuron's membrane becomes less negative.
True
Which of the choices below describes the ANS?
motor fibers that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle and glands
A neuron that has as its primary function the job of connecting other neurons is called a(an) __________________.
interneuron
What does the central nervous system use to determine the strength of a stimulus?
frequency of action potentials
The period after an initial stimulus when a neuron is not sensitive to another stimulus is the ______________.
absolute refractory period
The term central nervous system refers to the ______________.
brain and spinal cord
Axon diameter and degree of myelination determine nerve impulse conduction velocity.
True
Immediately after an action potential has peaked, which of the following channels will open?
voltage-gated potassium channels
A second nerve impulse cannot be generated until _________________.
the membrane potential has been reestablished
Which of the following correctly describes a graded potential?
it can have amplitudes of various sizes
Nerve impulses are sent to slow the heart's rate of contraction. The nerve fibers sending these signal will most likely belong to which division of the nervous system?
sensory (afferent) division
somatic nervous system
sympathetic division
parasympathetic
parasympathetic division
Which of the following is an excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle?
cholinesterase
acetylcholine
norepinephrine
gamma animobutyric acid
acetylcholine
In myelinated axons the voltage-regulated sodium channels are concentrated at the nodes of Ranvier.
True
An action potential is regarded as an example of a positive feedback. Which of the following examples below best illustrates the positive feedback aspect of an action potential?
A threshold stimulus will cause the opening of voltage gated sodium ion chann
A threshold stimulus will cause the opening of voltage gated sodium ion channels that will cause further depolarizing stimulus. This stimulus will open still more voltage gated sodium ion channels.
Which of the following is FALSE or INCORRECT?
An excitatory postsynaptic potential occurs if the excitatory effect is greater than the inhibitory effect but less than threshold.
A nerve impulse occurs if the excitatory and inhibitory effects are equal.
An
A nerve impulse occurs if the excitatory and inhibitory effects are equal.
Strong stimuli cause the amplitude of action potentials generated to increase.
False
Which of the following is NOT a function of the autonomic nervous system?
innervation of skeletal muscle
innervation of smooth muscle of the digestive tract
innervation of glands
innervation of cardiac muscle
innervation of skeletal muscle
Cell bodies of sensory neurons may be located in ganglia lying outside the central nervous system.
True
The all-or-none phenomenon as applied to nerve conduction states that the whole nerve cell must be stimulated for conduction to take place.
False
Saltatory conduction is made possible by _______________.
the myelin sheath
Nerve impulses leading to the skeletal muscle carry information to direct movement. The nerve fibers sending these signals will most likely belong to which division of the nervous system?
sensory (afferent) division
somatic nervous system
sympathetic divi
somatic nervous system
The action potential is caused by permeability changes in the plasma membrane.
True
Which ion channel opens in response to a change in membrane potential and participates in the generation and conduction of action potentials?
voltage-gated channels
Loss of function in the enzyme acetylcholine esterase would result in which of the following?
Inability to destroy and remove acetylcholina from the synaptic cleft
Which of the following is NOT characteristics of neurons?
They are mitotic
The interior surface of a neuron's plasma membrane at resting membrane potential will have a ________________.
negative charge and contain less sodium than outside of the cell
If a post synaptic neuron is stimulated to threshold by spatial summation this implies that ________________.
The postsynatpic cell has many synapses with many presynaptic neurons
The action potential changes the membrane from ________ mV (resting) to __________ mV and back again to the resting membrane potential.
-70, 30
This results from a change in membrane permeability first to ________ then to ________ due to the opening of what type of ion channels?
Na+, K+, voltage-gated channels
Where is the density of voltage-gated Na+ channels the greatest?
axon hillock
What areas of the neuron generate signals that open these voltage-gated channels?
the cell body and dendrites
If the membrane reaches the trigger point, known as _____________, what electrical potential will be generated?
threshold, action potential
During the depolarization phase, voltage-gated _______ channels open and ______ enters the cell.
Na+, Na+
What are the two processes that stop the potential from rising above +30 mV?
Inactivation of voltage-gated Na+ channels
Opening of voltage-gated K+ channls
The opening of voltage-gated K+ channels cause the membrane to ______________.
repolarize
Does K+ move into or out of the cell?
out of the cell
If the membrane potential becomes more negative than -70mV, this is called __________________.
hyperpolarization
This potential is caused by what characteristic of K+ permeability?
slow decline
After an action potential, the neuron cannot generate another action potential because _______ channels are inactive. This period is called the ___________________.
Na+, absolute refractory period
Conduction velocity along the axon is increased by what two characteristics?
the diameter of the axon (increased diameter)
how well the axon is insulated with myelin
Conduction along a myelinated axon is called __________________.
saltatory conduction
Name the disease whose symptoms include loss of vision and increasing muscle weakness.
Multiple Sclerosis (MS)
What does this disease destroy?
myelin sheath
How does this stop an action potential?
The myelin sheaths become hardened lesions (sclerosis). The loss of myelin shunts and short-circuits the current so that successive gaps are excited more and more slowly and eventually impulse conduction ceases.
Neurons communicate with other cells at junctions called __________________.
synapses
Neurons form synapses with _____________, _______________, and _______________.
muscles, glands and other neurons
Skeletal muscle is activated by neurons of the _____________________.
somatic nervous system
Cardiac muscle, smooth muscle and glands receive signals from neurons of the _____________________.
autonomic nervous system
A synapse between a somatic neuron and a skeletal muscle fiber is called a ___________________.
neuromuscular junction
When an action potential arrives at a neurotransmitter junction, it initiates a series of events which excite the underlying muscle fiber, causing it to _______________.
contract
At a chemical synapse, neuronal membranes are separated by a gap called the ___________________.
synaptic cleft
Electrical current cannot flow directly from one neuron to the other. A chemical, called a _______________, is released from the sending axon and carries the signal to the next neuron.
neurotransmitter
The neuron conducting an action potential toward the synapse is called the _______________.
presynaptic neuron
The axon terminal of the presynaptic neuron contains membranous sacs called ___________________ which are filled with ____________________.
synaptic vesicles, neurotransmitter
The gap separating the cells is called the ______________.
synaptic cleft
An action potential that reaches the axon terminal causes synaptic vesicles, to fuse with it, releasing ________________ into the ______________.
neurotransmitter, synaptic cleft
The neuron receiving the signal is called the postsynaptic neuron. When activated, receptors on the postsynaptic neuron open _________________.
ion channels
What channels in the presynaptic neuron open up in response to an action potential?
voltage-gated Ca2+ channels
The presence of what ion inside the cell causes the synaptic vesicles to fuse with the membrane?
Ca2+
What is the name for the channels stored in the synaptic vesicles?
neurotransmitters
What do these chemicals diffuse across?
the synaptic cleft
Where do these chemicals bind to receptors?
postsynaptic membrane
What type of gated channels do these chemicals open?
chemically-gated channels
Name two ways these chemicals can be removed from the synaptic cleft.
pumped into presynaptic terminal
broken down by enzymes
The response on the postsynaptic cell depends on two factors:
which neurotransmitter is involved
the specific receptor found on that cell
Autonomic nerves innervate what three things?
smooth muscle, cardiac muscle and glands
The most common excitatory neurotransmitter in the CNS is _______________.
glutamate
In which area of the neuron is an action potential initially generated?
axon hillcok
What change in a neuron is being measured in the graph?
the voltage measured across the axon membrane at a specific point as an action potential travels past.
At which point of the illustrated potential are the most gated Na+ channels open?
B
Which of the following circuit types is involved in the control of rhythmic activities such as the sleep-wake cycle, breathing, and certain motor activities (such as arm swinging when walking)?
converging circuits
reverberating circuits
diverging circuits
reverberating circuits
The period after an initial stimulus when a neuron is not sensitive to another stimulus is the _________________.
absolute refractory period
Saltatory conduction is made possible by ____________.
the myelin sheath
Which ion channel opens in response to a change in the membrane potential and participates in the generation and conduction of action potential?
voltage-gated channels
Immediately after an action potential has peaked, which cellular gates open?
potassium
The part of the neuron that conducts impulses away from its cell body is called a(n) ______________.
axon
Which structural classification describes this neuron?
multipolar
What is the structure of the extended fibers extending from the cell body?
dendrites
What areas of this neuron would be classified as receptive regions?
dendrites and cell body (soma)
Which of the following best characterizes depolarization?
small consecutive steps of Na+ exiting the cytoplasm into the extracellular fluid
mass movement of Na+ into the axon cytoplasm from the cell body to the terminal
small, consecutive steps of K+ ente
small consecutive steps of Na+ penetration into the axon along its length
Neurons __________________________.
flow through ion channels, depolarize membrane resting potential, and release vesicles.
bind at vesicle receptors and diffuse in vesicles across synapse, the vesicles bind at postsynatpic receptors.
are stored in vesicl
are stored in vesicles, diffuse across synapse, and bind at postsynaptic receptors.
When an action potential arrives at the end of the axon terminal, a series of events take place that result in the release of neurotransmitter from the presynaptic axon. Select the answer that correctly describes the primary stimulus for vesicles to move
voltage-gated membrane channels open and Ca2+ enters the cytoplasm, increasing intracellular calcium
Which statement best describes astrocytes?
Sodium from the action potential fuses with the membrane vesicle and releases the neurotransmitter in the cytoplasm, which can then diffuse out to the extracellular fluid.
Membrane organelles fuse with the membra
Membrane organelles fuse with the membrane and release contents out of the cell.
What condition will increase the diffusion of molecules, such as neurotransmitter?
an increase in number of postsynaptic receptors
an increased viscosity of the fluid between neurons
an increase in the amount of neurotransmitter exocytized by the presynap
an increase in the amount of neurotransmitter exocytized by the presynaptic axon
If the membrane of a postsynaptic dendrite is setting up a graded potential, what must have happened after neurotransmitter was released by the presynaptic terminal? The neurotransmitter ____________________.
bound at postsynaptic receptors to initiate an
bound at postsynaptic receptors to open postsynaptic ion channels
Which of the following choices best represents synaptic transmission?
presynaptic axon to synapse to dendrite or postsynaptic cell body
presynaptic axon to presynaptic cell body to dendrite
presynaptic axon to synapse to postsynaptic axon
presynaptic cell
presynaptic axon to synapse to dendrite or postsynaptic cell body
Predict the possible effect of a drug that totally blocks the neurotransmitter receptor on the postsynaptic membrane. For example, curare is a neurotoxin used by several South American cultures. The primary effect of curare is that acetylcholine, a major
local graded potential and action potential transmission is blocked and there is no response by the postsynaptic cell, the muscle
synapse
where two neurons communicate with each other
Which letter indicated the primary visual cortex?
D
The groove indicated by C is the ____________.
central sulcus
What structure is indicated by B?
corpus callosum
Which of the following is NOT one of the three types of functional areas within the cerebral cortex?
sensory areas
visual areas
motor areas
association areas
visual areas
Parkinson's disease results from degeneration of the dopamine-releasing neurons of the _____________.
substantia nigra
Which meninx is a delicate connective tissue membrane that clings tightly to the brain like cellophane wrap following its every convolution?
pia mater
Which part of the brain is considered the "gateway" to the cerebral cortex?
thalamus
Which part of the brain stem houses the reflex centers for respiration and cardiovascular functioning?
medulla oblongata
Which part of the brain processes inputs received from the cerebral motor cortex, brain stem nuclei, and various sensory receptors, and then uses this information to coordinate somatic motor output so that smooth, well-timed movements occur?
cerebellum
Which of the following allows us to consciously control our skeletal muscles?
the somatic nervous system
the parasympathetic division of the autonomic nervous system
the afferent division of the nervous system
the sympathetic division of the autonomic ner
the somatic nervous system
Which of the following is NOT a function of the autonomic nervous system?
innveration of glands
innervation of skeletal muscle
innervation of cardiac muscle
innveration of smooth muscle of the digestive tract
innveration of skeletal muscle
The central sulcus separates which lobes?
frontal from parietal
The blood-brain barrier is effective against __________.
metabolic waste such as urea
Region A includes which of the following?
prefrontal cortex
primary somatosensory cortex
primary motor cortex
Broca's area
prefrontal cortex
The groove indicated by C is the _____________.
central sulcus
Which of the following is the best description of the function of region B?
Region B coordinates the movement of several muscle groups into complex tasks.
Region B contains neurons receiving somatosensory input from the thalamus.
Region B includes neurons
Region B includes neurons who axons carry motor commands from the cerebrum.
What is the designation of the area at D?
primary visual cortex
The cortical regions indicated by E are involved in what functions?
They are the control centers for homeostatic and endocrine functions.
the production and interpretation of language
the storage of motor patterns for skilled movements of skeletal muscles
the production and interpretation of language
The conductive region of the neuron where the action potential occurs is called _____________.
the axon
The specific region on the axon where an action potential is generated is called _____________.
the axon hillock
What support cells forms the myelin sheaths in the peripheral nervous system?
Schwann cells
The gaps between Schwann cells that are essential for the conduction of the action potential are called ______________.
nodes of Ranvier
Neurons can communicate with, or stimulate, which of the following?
neurons, muscles, and glands
only glands and other neurons
only other neurons
only neurons and muscles
neurons, muscles and glands
Signals from other neurons are received on what parts of the neuron?
dendrites and the cell body (soma)
If axon branches, these branches of the neuron are called __________________.
axon collaterals
What is the correct order of the path of information in a neuron from input to output?
dendrite, cell body (soma), axon
In myelination, what part of the Schwann cell becomes the insulation?
the cell membrane
The action potential is a transient change in the resting membrane potential from -70 mV to +30 mV, then back to -70 mV. This change is caused by the opening of first ___________ then ____________ voltage-gated channels.
Na+ then K+
What area(s) of the neuron generate signals that open the voltage-gated channels in the first part of the axon, thus causing an action potential?
dendrites and cell body
As the axon hillock depolarizes, voltage-gated Na+ channels open and Na+ moves (into or out of) ____________ the cell causing further (depolarization or repolarization) ________________.
into, depolarization
If depolarization reaches -55 mV, an action potential will be generated. What is this -55 mV trigger point called?
threshold
At the end of the depolarization phase, what voltage-gated channels open to help restore the resting membrane potential?
voltage-gated K+ channels
Repolarization is caused by the movement of what ion (sodium or potassium) in what direction (into or out of the cell)?
potassium, out of the cell
After an action potential, the membrane becomes more negative than -70 mV. This period is called ______________.
hyperpolarization
After a neuron has generated an action potential, it cannot generate another one for a while. This period is called __________________.
absolute refractory period
The fasting conduction of an action potential would occur in an axon with which of the following characteristics?
small diameter and unmyelinated
small diameter and myelinated
large diameter and unmyelinated
large diameter and myelinated
large diameter and myelinated
What is the name of the disease in which the myelin sheaths of central nervous system axons are destroyed?
Multiple Sclerosis (MS)
The somatic nervous system stimulates what type of muscles?
skeletal
Will signals from the sympathetic nervous system (SNS) cause heart rate to increase or decrease?
increase
Will signals from the parasympathetic nervous system (PNS) cause smooth muscles in the small intestine to increase or decrease contractions?
increase
If a neuron synapses with the dendrite of another neuron and excites it, this will lead to an ______________ on the second neuron.
action potential
Synapses between axon terminals of one neuron and the cell body of another neuron are called ______________.
axosomatic synapses
The type of synapse that regulates the amount of chemical transmitter that is released is called an ______________.
axoaxonic synapse
In an electrical synapse, when current flows from one neuron to another through gap junctions, this synapse is always _________________.
excitatory
Which of these choices is the fastest synapse?
chemical
electrical
electrical
In chemical synapses, one neuron excites another neuron by _____________________.
releasing a transmitter
What causes the neurotransmitter to be released at a chemical synapse?
an action potential in the presynaptic neuron
What structures in the cell membrane function as ion channels?
integral proteins
Passive sodium channels in the cell membrane will allow sodium to move ____________.
into the cell
Another name for passive channels is ____________.
leakage channels
What is the resting membrane potential of a typical neuron?
-70 mV
What ions pass into the cell when acetylcholine binds to its chemically gated channel?
sodium
Chemically gated channels are located mainly on what parts of the neuron?
dendrites and cell body (soma)
Which channels are responsible for the action potential?
voltage-gated channels
Which of the following statements about voltage-gated sodium channels is correct?
Only K+ can pass through these channels.
They are sensitive to changes in membrane potential.
They are essential for producing the resting membrane potential.
They are found
They are sensitive to changes in membrane potential.
What channel allows chloride to enter the cell?
chemically gated GABA channels
The Japanese puffer fish contains a deadly toxin (tetrodotoxin) that can lead to death due to which of the following reason?
This toxin causes changes in the resting membrane potential.
This toxin stop synaptic potentials.
This toxin stops action potentia
This toxin stops action potentials.
Excitable cells are most permeable to which of the following cations?
potassium
sodium
potassium
What is the major cation inside the cell?
potassium
Which of the following would increase membrane permeability to K+?
opening of voltage-gated K+ channels
closing of voltage-gated K+ channels
a decrease in the number of passive K+ channels
opening of voltage-gated K+ channels
In a cell selectively permeable only to K+, what force will push K+ out of the cell?
concentration gradient
As more and more K+ ions leave the cell, what force will tend to pull K+ ions back into the cell?
electrical gradient
When the electrical and chemical gradients for K+ are equal, what will happen to the net movement of K+?
There will be no net movement of K+ across the membrane.
The inside of an excitable cell is negative compared with the outside. What gradient(s) would tend to move Na+ into the cell?
the concentration gradient and electrical gradient
Because the neuron is permeable to Na+ as well as K+, the resting membrane potential is ___________ mV.
-70
At a resting membrane potential of -70 mV, K+ tends to leak out of the cell and Na+ tends to leak into the cell. The Na+/K+ pump stops this leakage. How many sodium and potassium ions are moved, and in what direction do they move (in or out)?
3 Na+ out, 2 K+ in
What would happen to the resting membrane potential of a neuron if the extracellular concentration of K+ decreased (from 5 to 2.5 mM/L)?
The membrane potential would become more negative.