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42 Cards in this Set

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The 3 types of Neuronal Membrane Potentials are?
Resting Membrane Potential
Graded Potential
Action Potential
RAG
Where are action potentials generated?
Dendrites bring info to the axon and action potentials are produced at the axon hillock, conducted down the axon to the axon terminal
How is the Resting potential measured?
The cell is placed in water bath with an intracellular microelectrode and an extracellular electrode separated by a voltmeter.
What are the 2 ways that the electric force across charges separated by a membrane increase?
1. increases with the quantity of the charge
2. increases with decreasing distance
Define Voltage (V)?
measure of potential energy generated by separated charge
Define Potential difference?
voltage measured between two points
Define Current (I)?
the flow of electrical charge between two points
Define Resistance (R)?
hindrance to charge flow
Define Insulator?
substance with high electrical resistance
Define Conductor?
substance with low electrical resistance
Define OHM's Law?
I = E/R or E = IR; states that for any given voltage (E), the lower the resistance (R) of the material, the higher the current (I) flows
What are gradients?
substances that diffuse from high conc. to low conc. passively
When do ions flow along their chemical gradient?
when they move from an area of high concentration to an area of low concentration
When do ions flow along their electrical gradient?
when they move toward an area of opposite charge
What are electrochemical gradients?
the electrical and chemical gradients taken together
Hydrophilic substances need what?
pores and channels
What are the 4 types of plasma membrane ion channels?
1. Passive, or leakage,
channels
2. Chemically gated
channels
3. Voltage-gated channels
4. Mechanically gated
channels
Cute MVP
CaMP Vehicle
Differentiate between the 4 types of plasma membrane ion channels?
1. Passive, or leakage,
channels = always open
2. Chemically gated
channels = open with
binding of a specific
neurotransmitter
3. Voltage-gated channels=
open and close in
response to membrane
potential

4. Mechanically gated
channels = open and close
in response to physical
deformation of receptors
What is electrochemical potential?
it measures the relative contributions of the ionic concentration and the electric potential
ElI Prayed
EPIc Elements
ExPect = RICE and Potatoes
What is the Nernst Equation used for?
it is used to calculate the equilibrium potential at a given concentration difference of a permeable ion across a cell membrane by showing at what potential the ion is at electrochemical equilibrium.
NEcQ
What is the Nernst Equation and its derivatives?
E = 61mV/z (log Co/Ci)

E = equilibrium potential (mV)
z = charge on the ion (+1 for Na; +2 for Ca; -1 for Cl)
Co = outside concentration
Ci = inside concentration
What is Resting Membrane Potential (Vr) and how is it generated?
The potential difference (–70 mV) across the membrane of a resting neuron and it is generated by different concentrations of Na+, K+, Cl, and protein anions (A)
What 2 factors lead to Ionic differences?
1. Differential permeability
of the plasma membrane to
Na+ and K+
2. Operation of the sodium-
potassium pump
I-OP
Differentiate btw:
1. subthreshold stimulus,
normokalemia
2. Above-threshold stimulus,
normokalemia
3. subthreshold stimulus,
hyperkalemia
4. Above-threshold stimulus,
hypokalemia
1. subthreshold stimulus,
normokalemia = the
stimulus will not fire an
action potential when the
potassium in the blood is
normal.

2. Above-threshold stimulus,
normokalemia = the stimulus can produce an action potential when the potassium in the blood is normal.

3. subthreshold stimulus,
hyperkalemia = the increased blood potassium raises the membrane potential so that a lower stimulus will still generate an action potential

4. Above-threshold stimulus,
hypokalemia = the decreased potassium in the blood causes hyperpolarization of the membrane and a high stimulus will not produce an action potential
What is the relationship between resistance and conductance?
Conductance or "g" is equivalent to permeability and resistance is R so :
R = 1/g
An inverse relationship
Define Polarization
This is any state, positive or negative, other than 0 mV.
Define Depolarization
This change makes the membrane potential less negative than the resting potential.
Define Repolarization
The membrane returns to resting potential after depolarization.
Define Hyperpolarization
This makes the membrane more polarized, more negative (inside) than the resting potential.
Differentiate between open and gated channels?
1. open channels have gates but spend most of their time in the open state

2. gated channels are usually closed but open in response to electrical, chemical, or mechanical signals
Differentiate between :
1. Inhibitory postsynaptic
potential (IPSP)
2. Excitatory postsynaptic
potential (EPSP)
1. IPSP = increased negativity of the membrane potential of a postsynaptic neuron caused by the binding of an inhibitory neurotransmitter from a presynaptic cell to a postsynaptic receptor making it more difficult for a postsynaptic neuron to generate an action potential.

2. EPSP = decreased negativity of the membrane potential of the postsynaptic neuron caused by the binding of an excitatory neurotransmitter from a presynaptic cell to a postsynaptic receptor making it more likely for a postsynaptic neuron to generate an action potential.
what happens when gated channels are open?
Ions move quickly along their electrochemical gradients across the membrane, generate an electrical current and lead to a voltage changes across
the membrane
What is a graded potential?
It is a local electrical change in the membrane.
What events occur when there is a graded potential?
The graded potential occurs
in various grades and this change is progressively greater as the triggering event becomes progressively
stronger.
Also, the flow of sodium ions into the ICF produces this kind of potential and the duration of a graded
potential is directly
proportional to the duration of the triggering event.
How do Graded potentials spread?
They spread by passive current flow.
Describe graded potentials in terms of :
1. Voltage
2. Current
3. Distance
1. Voltage changes are
decremental
2. Current is quickly
dissipated due to the
leaky plasma membrane
3. Can only travel over
short distances
When does an action potential occur?
An action potential occurs if a membrane reaches threshold potential.
3 events due to action potential?
1. Voltage-gated channels in the membrane for sodium and potassium ions undergo conformational changes.

2. The flow of sodium ions into the ICF reverses the membrane potential from -70 mV to +30 mV.

3. The flow of potassium ions into the ECF restores the membrane potential to the resting state.
Illustrate 3 characteristics of action potentials?
1. Sodium channels open during depolarization by positive feedback.

2. When the sodium channels become inactive, the channels for potassium open. This repolarizes the membrane.

3. As the action potential develops at one point in the plasma membrane, it regenerates an identical action potential at the next point in the membrane.
Therefore, it travels along the plasma membrane undiminished.
What is the role of the refractory period?
It ensures one-way travel of an action potential and it also limits the frequency of action potentials.
3 ways to describe the conduction of action potentials on axons?
1. The conduction is contiguous.

2. An action potential occurs by all or none.

3. Stimulus strength is coded by action potential frequency.
3 ways that nerve fibers are classified?
1. Diameter
2. Degree of myelination
3. Speed of conduction
Nurses Feel like MDS