Lecture 5- Membrane Potential Flashcards
Central nervous system (integration)
brain and spinal cord
Peripheral nervous systems
sensory input and motor output
sensory receptor send the _____ to the brain for integration
Sensory input
motor output send the signal to the ____ from the brain and spinal cord after integration
effector
_____ receive, process and transmit information to other cells
-Functional Units of Nervous System
neurons
- the cell body
-contains genetic information, maintains the neuron’s structure, and provides energy to drive activities
soma
-receive input from many other neurons and carry those signals to the cell body.
-
dendrites
_____ (nerve fibers) – conduct signals away from the cell
• carry information for long distances with high fidelity and without loss
Axon
classification of neurons
- sensory or afferent neurons
- motor or efferent neurons
- interneuron
Action potential
Nerve impulses
AP is carried from the ______ (near axon hillock) to the axon terminal – skeletal muscle cell or gland
spike-initiating zone
Electrical potential difference across the cell membrane caused by different concentrations of ___, ____, and ___on each side of the membrane.
K+, Nat, and Cl ions
- fundamental property of cells resulting from an
excess of negative charges on side of the plasma membrane and an excess of positive charges on the
other side
Membrane Potential (Vm )
- source of potential energy to move molecules across membranes
-excitable cells use changes in _____ as
communication signals
-critical for allowing the coordinated movements of
cells and organisms
membrane potential
a ______ is a localized electrical gradient across membrane
membrane potential
________ are more concentrated within a cell
anions (negative)
_____ are more concentrated in the extracellular
fluid
cations (positive)
an unstimulated cell usually has a resting potential of _________
-70mV
As the K+ ions diffuse out of the cell, the impermeable anions are left behind, creating a ________
membrane potential
*Excess negative charge inside – draw _______ into the cell
positive charges
Potassium ions continue to
move, inward and outward fluxes exactly balance each other
equilibrium potential (Eion )
__________ Is the principal intracellular cation
K+
____ is the principal extracellular cation
Na+
____, ____, ____, ___ are the principal intracellular anions
proteins, amino acids, sulfate, and phosphate
____ - the concentration of K+ is greater inside the cell, while the concentration of Na+ is greater outside the
cell
at resting potential
at resting potential the concentration of K+ is greater inside
the cell, while the concentration of Na+ is greater outside the
cell - ________
chemical potential energy
____ use the energy of ATP to maintain
these K+ and Na+ gradients across the plasma membrane
Sodium-potassium pumps
Sodium-potassium pumps use the energy of ATP to maintain
these __ and ___ across the plasma membrane
K+ and Na+ gradients
Opening of ______ in the plasma membrane converts chemical potential to electrical potential
ion channels
Opening of ion channels in the plasma membrane converts
chemical potential to _____
electrical potential
A neuron at resting potential contains many open ___ and ___; K+ diffuses out of the
cell
K+ channels and fewer open Na+ channels
_____ trapped inside the cell contribute to the negative
charge within the neuron
Anions
- allow ions to
diffuse across the plasma membrane
– these channels are always open
Non-gated ion channels
____ can generate large changes in their
membrane potential
excitable cells
- open or close in response to stimuli
gated ion channels
- opening or closing of ion channels alters the membrane‘s
permeability to particular ions, which in turn alters the _____
membrane potential
types of gated-ions
- chemically-gated ion channels (ligand-gated ion channels)
- voltage-gated ion channels
_____ open or close in response to a
chemical stimulus
chemically-gated ion channels (ligand-gated ion channels)
__________ open or close in
response to a change in membrane potential
voltage-gated ion channels
changes in membrane potential of neuron give rise to ____
nerve impulses
What are the two graded potential:
- Hyperpolarization
- Depolarization
Gated K+ channels open,
K+ diffuses out of the
cell , the membrane
potential becomes
more negative
more negative
Gated Na+ channels
open ® Na+ diffuses
into the cell ® the
membrane potential
becomes less
negative
Depolarization
An _____ is a rapid sequence of changes in the voltage across a membrane
action potential
In the resting state, closed voltage-gated K+ channels open slowly in response to depolarization
Voltage-gated Na+ channels have two gates:
- closed activation gates open rapidly in response to
depolarization - open inactivation gates close slowly in response to depolarization
Most voltage-gated Na+ and K+
channels are closed, but some K+
channels (not voltage-gated) are
open
Resting phase
Voltage-gated Na+ channels open first
and Na+ flows into the cell
Depolarization
During the _____, the threshold is
crossed, and the membrane potential
increases
Rising phase
During ____ , voltage-gated
Na+ channels become inactivated;
voltage-gated K+ channels open, and K+ flows out of the cell
falling phase
during falling phase, voltage-gated
Na+ channels become _____;
voltage-gated K+ channels open, and K+ flows out of the cell
inactivated
During the ______, membrane permeability to K+ is at first higher than at rest, then voltage-gated K+ channels close; resting potential is restored
undershoot
The _______ is a result of a temporary inactivation of the Na+ channels.
refractory period
nerve impulses
propagate themselves
along an ____
axon
the _____ is
repeatedly regenerated
along the length of the
axon
action potential
An action potential is generated as
sodium ions flow ____ across the
membrane at one location
inward
An _____ is generated as
sodium ions flow inward across the
membrane at one location
action potential
the membrane is
____ as K+ flows outward
repolarizing
- in myelinated neurons only unmyelinated regions of the axon
depolarize
Saltatory conduction
Depolarized region
Node of Ranvier
– in myelinated neurons only unmyelinated regions of the axon
depolarize
_ thus, the impulse moves faster than in unmyelinated neurons
Saltatory conduction
in myelinated neurons only unmyelinated regions of the axon
____
depolarize
– action potential travels directly from the presynaptic to the postsynaptic cells via gap junctions
electrical synapses
In electrical synapses, action potential travels directly from the presynaptic
to the postsynaptic cells via _____
gap junctions
A _____ transmits the signal toward a synapse
presynaptic neuron
A _____ , transmits the signal away from the synapse
postsynaptic neuron
_______ is a region where
neurons nearly touch and
where nerve impulse is
transferred
synapse
Synapse is a region where
neurons nearly touch and
where nerve impulse is
______
transferred
a small gap between neurons is called?
synaptic cleft
Transmission across a
synapse is carried out by
______
neurotransmitter
Transmission oy synapse result in a ____
Sudden rise in calcium at end
of one neuron
Stimulates synaptic vesicles to
merge with the presynaptic
membrane
Neurotransmitter
_____ r molecules
are released into the synaptic
cleft
neurotransmitter
Primary Factors Influencing Impulse Transmission
- Axon diameter (typically around 1 micrometer)
- Myelination - formation of the myelin sheath around a nerve
- Temperature - the lower the temperature, the slower the impulses move.
– increase the transmembrane resistance and
decrease the effective neuronal membrane capacitance
Myelination
As the number of membrane layers wrapped around the axon
Resistance increase
If the myelin layer is thick
Capacitance decrease
Action potentials traveling down the axon “jump” from node to node.
Saltatory conduction
