Week 2: Nerve Excitability and Propagation Flashcards
The transmembrane potential of a resting cell.
Resting Potential
A stimulus that produces temporary, localized changed in resting state.
Graded Potential
An impulse that is propagated along the surface of the axon.
Action Potential
Produces graded potentials in postsynaptic cells.
Synaptic Activity
The integration of stimulus by the postsynaptic cell.
Information Processing
This fluid has higher concentrations of Na+ and Cl-.
Extracellular Fluid
This fluid has higher concentrations of K+ and negatively charged proteins.
Intracellular Fluid
This means that ions have to move through membrane channels in order to pass from intracellular and extracellular fluid spaces.
Selective Permeability
True or False?
Membrane permeability varies by ions.
True.
True or False?
Both passive and active transport mechanisms at the level of the cell membrane ensure an equal charge exists across the cell membrane.
False.
Ensures an UNEQUAL charge exists across the cell membrane.
Represent the imbalance in the number of particular ions across the cell membrane.
Chemical Gradients (Passive Force)
Represent the imbalance of electrical charges across the cell membrane which is more negative inside the cell.
Electrical Gradients (Passive Force)
Result from the combined chemical and electrical forces acting on a specific ion.
Electrochemical Gradients (Passive Force)
There are ______ K+ inside the cell so the K+ wants to move _________.
More, out.
There are ______ Na+ outside the cell so Na+ want to move ______.
More, in.
A chemical gradient results in _____ movement driven by chemical ____________ differences between ECF and ICF.
Ion, concentration.
Electrical differences are measured in __________.
Millivolts (mV)
A typical neuron rests at ______.
-70 mV
The membrane potential at which there is no net movement of a particular ion across the plasma membrane is called __________ ____________.
Equilibrium Potential
K+ has an equilibrium potential of _______.
-90 mV
Na+ has an equilibrium of _________.
+66 mV
At normal resting potential, the cell must bail out ________ that leak in and recapture __________ that leaked out.
Sodium, potassium.
The bailing of sodium and recapturing of potassium is done by what pump?
Sodium-Potassium Exchange Pump
The Sodium-Potassium Exchange Pump is powered by ______, making it an active transport mechanism.
ATP
The Sodium-Potassium Exchange Pump exchanges __ intracellular Na+ for __ intracellular K+.
3 Na+, 2 K+
The Sodium-Potassium Exchange Pump involves a carrier protein called ____________.
Sodium-Potassium ATPase
Also called leak channels; are always open but permeability can vary from moment to moment.
Passive Channels
Also called gated channels; open or close in response to specific stimuli
Active Channels
Gated channels that open or close when specific chemical bind to receptor sites on the channel.
Chemically Gated Channels
Gated channels that open and close in response to changes in the transmembrane potential when the cell reaches threshold.
Electrically Gated Channels
Gated channels that open and close in response to physical distortion (pressure) of the membrane surface.
Mechanically Gated Channels
Graded potentials are also called ___________.
Local Potentials
True or False?
Graded potentials are changes in the membrane potential that can spread far from the site of stimulation.
False.
Graded potentials CANNOT spread far.
True or False?
Any stimulus that opens gated channels produces a graded potential.
True.
Na+ are attracted to the \_\_\_\_\_\_\_\_\_\_ charges along the \_\_\_\_\_\_\_\_\_\_\_ surface of the nerve cell membrane. A) positive, outer B) negative, inner C) positive, inner D) negative, outer
B) negative, inner
Na+ influx shifts the membrane potential toward 0 mV also called \_\_\_\_\_\_\_\_\_\_\_\_\_\_. A) hyperpolarization B) equilibrium C) depolarization D) polarization
C) depolarization
True or False?
During graded potentials, the degree of depolarization decreases with distance away from the site of stimulation.
True.
True or False?
Graded potentials always lead to an action potential.
False.
Graded potentials MAY OR MAY NOT lead to an action potential.
When a stimulus is removed, normal membrane permeability is restored to resting levels, which is called ____________.
Repolarization.
Graded potentials are usually brought about by \_\_\_\_\_\_\_\_\_ or \_\_\_\_\_\_\_\_\_\_\_ gated channels. A) chemically, mechanically B) chemically, electrically C) electrically, mechanically D) active, passive
A) chemically, mechanically
True or False?
Electrically gated ion channels are associated with action potentials.
True.
-70mV toward -60 mV a graded _____________.
Depolarization
-70 mV toward -90 mV a graded ______________.
Hyperpolarization
Also called excitation; is any shift from resting membrane potential toward 0 mV.
Depolarization
The process of restoring the normal resting potential after depolarization.
Repolarization
The first step in generation of an action potential is the opening of voltage gated ________ _________.
Sodium channels
Threshold is at _____ mV.
-60 mV
True or False?
Once one voltage gated Na+ channels is opened, adjacent voltage gated Na+ channels open.
True.
Arrange the steps of an action potential.
_____ Around 30+ mV; Na + inactivation gate close; K+ activation gates open: K+ moves out; repolarization begins
_____ The cell body is depolarized enough that it reaches threshold and voltage gated Na+ channels open
_____ Na+ inactivation gate remains closed until threshold reached; K+ channels begin to close at -70 mV; a brief period of hyperpolarization occurs after
_____ Na+ activation gates open; Na+ is driven down the electrochemical gradient; rapid depolarization results in a positive intracellular charge
Step 3
Step 1
Step 4
Step 2
The period in which the plasma membrane does not respond normally to additional stimuli from the time an action potential begins until the normal resting membrane has stabilized.
Refractory Period
This type of refractory period occurs when Na+ activation gates are open or Na+ inactivation gates are closed.
Absolute Refractory Period
This type of refractory period occurs when Na+ channels regain their rest position up until resting membrane potential is achieved.
Relative Refractory Period
True or False?
Another action potential can occur in the relative refractory period only if the cell membrane is sufficiently hyperpolarized.
False.
Only if the cell membrane is sufficiently DEPOLARIZED.
This type of propagation occurs along an unmyelinated axon resembling dominos; this is a slower type of propagation.
Continuous Propagation
This type of propagation occurs along a myelinated axon resembling the game “Leap Frog”; this is a much faster type of propagation.
Saltatory Propagtaion
Myelin greatly \_\_\_\_\_\_\_ propagation speed of action potentials. A) decreases B) inhibits C) deducts D) increases
D) increases
The diameter of the axon affects the propagation speed, and the \_\_\_\_\_\_\_\_ the diameter, the lower the \_\_\_\_\_\_\_\_ to propagation. A) smaller, acceptance B) larger, resistance C) larger, acceptance D) smaller, resistance
B) larger, resistance
These type of fibres are the largest diameter, myelinated fibres; action potential speeds up to 120 m/s (268 mph)
Type A Fibres
These type of fibres are smaller in diameter, myelinated fibres; 18 m/s (40 mph).
Type B Fibres
These type of fibres are smaller in diameter, unmyelinated fibres; 1 m/s (2mph)
Type C Fibres
