neuron potentials Flashcards
1
Q
what happens when a membrane potential becomes more negative
A
- the membrane is hyperpolarized
Deviates from norm state
2
Q
if the membrane potential becomes less negative what happens to the membrane?
A
- the membrane becomes depolarized
Gets closer to norm state
3
Q
How are local potential changes graded?
A
- the greater the stimulus intensity, the greater the potential change
4
Q
What happens when depolarization reaches the threshold point?
A
- has to reach -55mV
- action potential results
5
Q
What are millivolts?
A
- is the measure of potential energy generated by separated charges
6
Q
How are membranes used in the neuron potential process?
A
- serves as a barrier between ions that helps to build up potential
7
Q
What is the charge on the inside of the cell during resting membrane potential?
A
- negative
8
Q
What is the sodium-potassium pump?
A
- for every 2 K+ ions that it pumps out of the cell, it releases 3 sodium ions into the cell
- creates a difference in charges and makes the outside of the neuron more positive
- creates an electrochemical gradients
9
Q
What are voltage-gated channels?
A
- ## open and close in response to changes in membrane potential
10
Q
What mV do sodium channels like to open at?
A
- 55mV
11
Q
What do ligand-gland channels open to?
A
- specific neurotransmitter latches to its receptor
12
Q
What happens when ions escape thru channels?
A
- they diffuse down their electrochemical gradient and even out the concentration
13
Q
What is a graded potential?
A
- a small amount of change within the membrane in a localized part of the cell
14
Q
What is an action potential?
A
- a larger reaction that sends signals across axons
- triggers voltage gated channels
- for true action potential to kick in, the stimulus must reach about -55mV
15
Q
What causes a change in resting potential?
A
- stimulus
- the stimulus and resulting change has to be strong enough to cross a threshold
- for action potential to kick in, the threshold must reach about -55mV
16
Q
What is an all-or-nothing phenomenon?
A
- if the change doesn’t hit the level of -55mV, it’s like a false alarm and the neuron returns to it’s resting potential state
17
Q
What happens at -55mV that causes action potential change?
A
- the voltage-gated sodium channels open
- positive sodium ions rush in and make the cell massively depolarized
- goes positive up to about 40mV
18
Q
What is action potential?
A
- a brief depolarization caused by changes in current that is sparked by stimuli
- kicks off biological chain reaction that sends action down an axon
19
Q
What is the process of repolarization
A
- voltage gated potassium ion channels open up and let potassium ions flow out
- goes thru brief hyper polarization and the voltage drops to -75 mV before all the gates close and the sodium-potassium take over and bring everything back to resting level
20
Q
- what changes in the action potential in response to a stimuli?
A
- the frequency of the buzz that communicates between neurons
- smaller stimuli = slower buzzes
- large stimuli = faster buzzes
21
Q
What factor affects a neuron transmission speed the most?
A
- whether or not there is a myelin sheath around the axon
- axons coated in myelin conduct impulses faster than non-myelinated ones
22
Q
What is saltatory conduction?
A
- the transmission speed of a neuron leaping between nodes of ranvier that allows them to travel faster
23
Q
What part of the neuron senses stimuli?
A
- the dendrites
24
Q
What does the sodium potassium pump maintain?
A
- it maintains a resting membrane potential
25
where is the sodium potassium pump initially open to?
- the intracellular side of the cell
- has binding room for 3 sodium ions
- when the 3 sodium ions bind, they are phosphorylated
- ATP transfers its phosphate to the protein channel and causes it to change shape which causes the pump to open to the outside and the sodium ions are pushed to the outside
- has 2 potassium ions for the K+ to bind
- phosphate detaches and the protein channel returns to normal configuration and allows K+ into the inside of the cell
26
How does the sodium-potassium pump move ions across a concentration gradient?
- moves the ions AGAINST their concentration gradient using ATP
- keeps putting more Na+ ions outside where there is already an abundance
- also keeps putting potassium inside where there is already an abundance
- moves from low concentration to high concentration
27
What is the result of the sodium-potassium pumps work?
- considerably more K+ on the inside of the cell and more sodium ions outside
- causes an electrochemical gradient
- difference in charge AND ion types
28
how does K+ escape the cell since it is generally not permeable to the membrane?
- K+ escapes thru channels that are permeable to the ion
- the inequality of movement for K+ to be allowed to travel towards the outside of the cell contributes to a more negative charge inside of the cell
29
What happens when an axon membrane reaches it's threshold??
- voltage-sensitive sodium channels open and some Na+ diffuses inward and the membrane is depolarized
- whilst this happens, potassium channels open and K+ diffuses out and the membrane is repolarized
30
What is depolarization?
- the membrane of a neuron becoming less negative than the resting potential (more positive)
31
What is re-polarization?
- the membrane potential of a neuron returning to its resting negative state
32
What triggers a neuron out of its resting potential?
- a stimulus
33
What is a stimulus?
- anything that can "excite' a cell out of its resting potential of 70mV in either direction
- an excitatory stimulus will open chemically-gated Na+ channels, and based on the concentration gradient, Na+ ions flow in and make the neuron less negative
34
What is a threshold stimulus?
- usually a specific neurotransmitter will cause Na+ to flow in long enough to change the potential to -55mv
- this is called the threshold potential
35
what happens when a cell reaches threshold potential?
- voltage-gated sodium channels open at the trigger zone and the charge of the cell rapidly rises to about +30mV
- this reaction is known as action potential
- the change from neg to pos charge is known as depolarization because the inside and outside of the neuron now each possess a positive charge
36
what happens after the action potential is reached?
- there is a quick return to the resting membrane potential
- this is accomplished thru the opening of channels that allow potassium to rush out
- this is known as re-polarization because the polarity between the inside and the outside of the neuron is re-established
37
what is hyper-polarization?
- it's where the potential temporarily dips a bit below -70mV
- the actual number of sodium and potassium ions crossing the cell membrane is extremely small compared to how many are present but the bioelectric effect is quite significant
