Ionic Basis of Resting Membrane Potential - Dr. Sylvester - Exam 1 - Patho 1

EPSPs cause __________ (depolarization, hyperpolarization)

depolarization

IPSPs cause ___________ (depolarization, hyperpolarization)

hyperpolarization

Action potentials are the primary electrical responses of neurons, & they result from changes in the conduction of _______ across the cell membrane.

ions

T/F: Action potentials occur slowly, & membrane potential changes are large.

False: Occur rapidly and change is small

Action potentials are transmitted along the neuron's ________ to its terminal

axon

T/F: Nerves act much faster than electrical wires

F

T/F: The amplitude & velocity of an action potential varies depending on the size of the stimulant.

F: all move with the same amplitude & velocity

T/F: Action potentials are "all or none".

T

Neuronal cell bodies can either be _________ or _________ by EPSPs or IPSPs.

depolarized, hyperpolarized

If threshold is reached, ___________ channels are opened causing an action potential to occur.

voltage-gated Na

inside of a neuronal cell is _______ charged while the outside of the cell is _________ charged

negatively, positively

Action potentials propagate down an axon due to changes in _______ along the axon.

charge

________ results from a difference in charge in the inside & outside of the cell membrane because of unequal distribution of ions across the membrane.

Membrane potential

__________ is known as the unequal distribution of charge across the cell membrane

concentration gradient

T/F: Channels within the cell membrane are ion specific.

T

resting membrane potential is an equilibrium state between the _________ & __________

ions concentration, electrical gradient

Ions move ________ (passively, actively) through pores & channels in the cell membrane.

passively

What ion have a much higher concentration inside the neuronal cell

K

What ion have a much higher concentration outside the neuronal cell

Na

The concentration difference between Na & K inside & outside the neuronal cell is established by _________.

Na/K ATPase

______ moves out of a neuronal cell when channels are open, & ______ moves into a cell when channels are open

K, Na

What is the resting membrane potential; close to equilibrium potential of K

-70 mV

Neuronal cell membranes are _______ (more, less) permeable to K than Na

more

K is almost always moving out of a neuron, explaining the _______ charge on the inside of the neuron

negative

intracellular & extracellular _______ concentration are the prime determinants of resting membrane potential

K

Since a steady leak of K cannot continue forever without eventual loss of gradient, ________ actively moves N & K AGAINST their electrochemical gradients.

Na/K ATPase

Na/K ATPase move ____ Na OUT for every _____ K that it moves IN.

3, 2

T/F: When Na moves passively through channels, it follows both concentration & electrochemical gradient while K only follows concentration gradient.

T

Cl can cause _______ potentials by causing hyperpolarization.

inhibitory

______ concentration is kept low inside of cells to prevent constant muscle contraction.

Ca

Membrane potential becomes more ________ as you increase the amount of K on the extracellular side of the cell, making it easier for an action potential to occur.

positive

What ion generally controls membrane potential of a neuron?

K

threshold = ________

-55 mV

_______ channels open when threshold is reached, & ions flood the cell causing an action potential.

Voltage-gated Na

_________ channels open after an action potential occurs to repolarize the cell to resting membrane potential.

Voltage-gated K

During depolarization, _________ channels open & ions enter the cell causing the membrane to reach threshold.

voltage-gated Na

Entry of Na causes ___________ channels to open & further depolarize the cell.

more voltage-gated Na

Voltage-gated K channels remain open shortly after resting membrane potential is reached following an action potential. This causes _________ to occur.

hyperpolarization

Voltage-gated Na channels are controlled by _______ feedback mechanism while voltage-gated K channels are controlled via ________ feedback.

positive, negative

Increasing extracellular K makes it ______ for an action potential to occur.

easier

T/F: Very few ions actually move across the cell membrane while an action potential is occurring.

T

_________ (increasing, decreasing) intracellular Ca causes a cell to become more excitable & easier for an action potential to occur.

increasing

A minimal _______ of stimulating current acting for a given duration is required to produce an action potential.

intensity

Threshold intensity varies with _______: with weak stimuli, long duration is required to cause an action potential, & with strong stimuli, duration can be short.

duration

Slowly rising currents fail to fire nerves because the nerves _______ to the applied stimulus.

adapt

Subthreshold stimuli do not cause action potentials, but they do have an effect on _________.

membrane potential

For subthreshold stimuli, the greater the _______, the greater the local response. A stronger stimulus will depolarize a cell more than a weaker stimulus.

stimulus

T/F: An action potential can be produced by a single EPSP of very strong magnitude.

F: multiple EPSPs required for AP to occur

T/F: APs occur only in the axon of a neuron, not in the cell body or dendrites.

T

When sufficient amounts of excitatory neurotransmitters are released into the synapse, it activates specific receptors on the postsynaptic membrane, causing ________.

depolarization

Depolarization can be caused by an influx of Na or _______.

Ca2+

A unit of depolarization is called a ______.

EPSP

when multiple EPSPs work together to cause an AP

summation

Inhibitory neurotransmitters activate specific receptors on the postsynaptic membrane & cause ________.

hyperpolarization

Hyperpolarization can be caused by an influx of _______ or an efflux of _______.

Cl, K

A _______ is a unit of hyperpolarization.

IPSP

T/F: A multitude of IPSPs can cause resting membrane potential to become lower than the normal resting membrane potential of -70 mV.

T

_________ is when EPSPs from the same nerve summate to cause an AP

temporal summation

_________ is when EPSPs from different nerves summate to cause an AP

spacial summation

___________ is when an EPSP & IPSP occur at the same time, causing no change in membrane potential

EPSP-IPSP cancellation

What is the specialized part of a neuron that connects the cell body to the axon?

axon hillock

axon hillocks are _________ (myelinated, unmyelinated)

unmyelinated

__________ is the location where APs are initiated

axon hillock

During an AP, resting membrane polarity is temporarily reversed with _______ charge on the inside & ______ charge on the outside. This allows an AP to propagate down an axon.

positive, negative

APs move down an axon because of _______

ion

In ________ axons, positive charges from the membrane ahead of & behind the AP flow into the area of negativity.

unmyelinated

In _________ axons, depolarization jumps from one node of Ranvier to the next.

myelinated

___________ is when depolarization jumps from one node of Ranvier to the next during an AP in a myelinated axon

saltatory conduction

APs travel about ______ times faster in myelinated axons than they do in unmyelinated axons because of saltatory conduction.

50