Neuro Exam #1: Action potentials-conductance

sodium

before action potential is reached, which ion is moving into the neuron membrane?

potassium

after action potential is reached, which ion is moving out of the neuron membrane?

-80- -70 mV

what is the range for a neuron's resting potential?

Na+ channels open

what occurs once the threshold level is reached?

Na +channels close, K+ channels open

what occurs when action potential is reached?

sodium

what channels are open during depolarization?

potassium

what channels are open during repolarization?

into

Na+ channels allow ions to move _____ the cell

out of

K+ channels allow ions to move _____ the cell

K+ channels remain open after resting potential

what occurs during hyperpolatization?

E Na+

During depolarization, Em moves toward _______

E K+

During repolarization, Em moves toward _______

threshold

the opening voltage for both channels is ________

threshold

ID the purple box:

hyperpolarization

ID the blue box:

repolarization

ID the green box:

depolarization

ID the yellow box:

resting membrane potential

ID the orange box:

all-or-none principle

once threshold is reached, an action potential reaches full amplitude:

absolute refractory period

the time during which it is impossible to generate a second action potential:

relative refractory period

the time during which a second action potential can be generated but would require a stronger stimulus to reach threshold:

sodium channel inactivation

what is the molecular mechanism of the absolute refractory period?

false

t/f: with enough stimulus, the sodium channel that is in inactivation state can be opened again

larger stimulus

after Na+ channel reactivation, it is possible to generate another action potential but a ___________ is necessary to open enough Na+ channels to override the efflux of K+ whose permeability is still above the resting state

true

t/f: Action potentials are "all-or-none"

Na+ channels

local dental anesthesia lidocaine works on______

inactive

lidocaine acts at a defined site on Na+ channels and lock the channel in its _________ conformation

false

t/f: when a Na+ channel is in inactive form, it remains open and ions continue to diffuse in

regenerative current

Propagation of an action potential in an excitable cell:

nodes of Ranvier

the myelin sheaths are discontinuous and are separated by areas of bare axonal membrane called:

saltatory conduction

for myelinated neurons, ion flux passes only through the Nodes of Ranvier where there are functional channels, thus the action potential "jumps from node to node. This is called:

length constant (lambda)

quantifies the distance that a graded electrical potential can travel passively down an axon - before it decays to ~ 37% of its original amplitude:

membrane resistance

the force that impedes the flow of ions from the outside of the membrane to the inside, and vice versa:

axial resistance

the force that impedes current flow through the axoplasm (down the axon), parallel to the membrane:

# of channels

what determines the membrane resistance?

axon diameter

what determines the axial resistance?

greater

the fewer number of channels, the ______ the membrane resistance

lower

the more number of channels, the ______ the membrane resistance

lower

the greater the diameter of an axon, the ____ the axial resistance

greater

the smaller the diameter of an axon, the ____ the axial resistance

greater

a nerve with a large axon will have a ______ conduction velocity

greater

axons that are myelinated will have a ______ membrane resistance

lower

axons that are unmyelinated will have a ______ membrane resistance

large diameter, myelinated

Which type of axon will have the fastest conduction velocity?
- large diameter, unmyelinated
- large diameter, myelinated
- small diameter, unmlyelinated
- small diameter, myelinated

low axial resistance, high membrane resistance

Which type of axon will have the fastest conduction velocity?
- low axial resistance, low membrane resistance
- high axial resistance, high membrane resistance
- low axial resistance, high membrane resistance
- high axial resistance, low membrane resistance

high axial resistance, low membrane resistance

Which type of axon will have the slowest conduction velocity?
- low axial resistance, low membrane resistance
- high axial resistance, high membrane resistance
- low axial resistance, high membrane resistance
- high axial resistance, low membrane resistance

small diameter, unmlyelinated

Which type of axon will have the slowest conduction velocity?
- large diameter, unmyelinated
- large diameter, myelinated
- small diameter, unmlyelinated
- small diameter, myelinated

true

t/f: the ionic current injected into the axon will follow the path of least resistance

axon diameter and myelination

The length constant is a function of:

demyelinating

multiple sclerosis is a _______ disease

membrane resistance

when it comes to the length constant, patients with multiple sclerosis have a biological defect that will affect what variable?

decrease

patients with multiple sclerosis have a biological defect that will ________ the membrane resistance of their neurons