NPB101: Membrane Potentials Part 4

Getting that AP to Move; Signaling Between Neurons and Targets

An AP drives a current to the ____.

neuron

T/F: An AP creates a local current

True an AP does create a local current (depolarization)

Distance matters when eliciting an AP because?

current can die out over time (length)

AP

It creates a current, and then that current depolarizes the adjacent region, and we regenerate the action potential.

T/F: Does the AP travel?

False, it regenerates not travels

What is this region called

Axon Hillock

What is occurring at the Axon Hillock?

at the Axon Hillock is where the AP starts off (elicits & sum)

In vivo, why don’t APs travel backwards/upstream (antidromic direction)?

a) The upstream region’s V-gated Na + channels are inactivated and cannot open to induce an AP

b) The upstream region’s V-gated K + channels are inactivated and cannot open to induce an AP

c) The upstream region runs out of extracellular Na+, so no Na+ can flow to induce an AP

d) The upstream region needs to regrow new channels before it can conduct an AP

a) The upstream region’s V-gated Na + channels are inactivated and cannot open to induce an AP, because imagine eliciting an AP on your finger and it travels backwards and forwards OUCH

T/F: AP travel backwards

False, AP do NOT travel backwards, only forwards because Na+ channel would be inactivated

AP in a neuron called unmyelinated (naked axon)

An axon with a bunch of stuff wrapped around it is what?

The stuff wrapped around an axon is called myelin that supports the cell

Myelin can be formed on?

oligodendrocytes (central neurons) and Schwann cells (peripheral neurons)

Myelin creates very specific region on the axon called _____

Nodes of Ranvier

In the Nodes is the only place you have ____ and ____ channels

V-Gated Na+ and K+ channels

Saltatory

“jumping”

What is Saltatory Conduction in Neurons?

Saltatory Conduction in neurons is when an AP is being elicited through the neuron at the axon region where it takes “big steps” and does the AP at the Nodes of Ranvier

What happens to motors that get demyelinated?

When motors get demyelinated, they cannot conduct fast AP

T/F: AP occur at Nodes of Ranvier

True they occur at Node of Ranvier as it goes through the neuron at the axon

The neuron is the communication cell of the _____

body

Electrical current is traveling through the ____

Neuron

T/F: Is the electrical current that travels through the neuron which is the signal?

True, the electrical current that travels through the neuron is the signal, the info traveling through the neuron

How does the current get to the target?

The current gets to the target by the synaptic cleft (the space between the axon terminus and the target. This is because it cannot jump to the target

Vesicles contain _____.

neurotransmitters

Neurotransmitters are stored in ______

vesicles

The AP travels down the ____.

axon

The AP and ____ current cause _____ at the ____ terminus.

electrical, depolarization, axon

T/F: V-Gated Ca2+ channel responds to hyperpolarization

False V-Gated Ca2+ channel responds to depolarization bc it opens in response to it

When a V-Gated Ca2+ channel responds to depolarization what happens?

V-Gated Ca2+ channel will be activated

Depolarization at the ____ activates V-Gated Ca2+ channel and (opens/closes) ____ with an influx of ____

terminus, opens, Ca2+

When Ca2+ comes into the terminus it causes the ____ to fuse

vesicles

What do the vesicles fuse to?

Presynaptic membrane (end of axon terminus)

Neurotransmitters get released into the _____ cleft

synaptic

Neurotransmitter has a ___ distance to travel

short

The neurotransmitter will manage to ___ to the ____ on the target

bind, receptor

What is this? What does it look like?

This is the receptor for the neurotransmitter and it looks like a channel and can act like one

What does this arrow of the receptor do?

allows an influx of Na+ to flow through causing depolarization and passes threshold creating an AP

What does this arrow of the receptor do?

It allows an efflux of K+ to flow out the cell creating hyperpolarizing not firing an AP

Neurotransmitters that depolarize the cell are called?

excitatory neurotransmitters

Neurotransmitters that cause ion, particularly K+(leave the cell) or even Cl-(into the cell) is called?

Inhibitory neurotransmitters

When K+ leaves the cell or Cl- going into the cell this is?

hyperpolarization

During hyperpolarization K+ ___ the cell and Cl- ____ the cell

leaves, enters

T/F: Excitatory causes hyperpolarization

False, Excitatory causes depolarization

What ions flow with an influx due to Excitatory/Depolarization? Choose 1 or more

• Na+

• K+

• Cl-

• Ca2+

Na+ and Ca2+ flow in with an influx

T/F: Inhibitory causes hyperpolarization

True

What ions flow with an influx due to Inhibitory/Hyperpolarization? Choose 1 or more

• Na+

• K+

• Cl-

• Ca2+

Cl- flows with an influx

What ions flow with an efflux due to Inhibitory/Hyperpolarization? Choose 1 or more

• Na+

• K+

• Cl-

• Ca2+

K+ flows with an efflux

If you have a lot of excitatory neurotransmitter, the neurotransmitter’s would cause a ____ depolarization

big

If you have a tiny amount of excitatory neurotransmitters the depolarization would be ___

small

If you have a lot of excitatory neurotransmitter, the neurotransmitter’s would cause a big depolarization & If you have a tiny amount of excitatory neurotransmitters the depolarization would be small. What is this called?

Graded Potential

For those that cause depolarization/excitatory (Na+ & Ca2+) this is called?

Excitatory(Depolarize) Post-Synaptic (occurring on the target tissue post-synaptic cell) Potential: EPSP

For those that cause hyperpolarization/inhibitory (K+ & Cl-) this is called?

Inhibitory Post-Synaptic Potential: IPSP

This is basically a ____ of information thats going to ___ this neuron

convergence, control

This is a ____ of information to talk to ____ targets

divergence, multiple

T/F: a Divergence output communicates with a synapse at one target

no a divergence output communicates with multiple targets at a synapse

T/F: a Convergence output communicates with a synapse at one target

False this doesn’t exist

T/F: a COnvergence

Target neurons receive ___ input from __#__ to __#__ of other neurons

synaptic, hundreds to thousands

T/F: this is Convergence: One cell influences many others

False this would be Divergence as it influences many others

T/F: this is Convergence: One cell influences many others. If not, explain what convergence is.

False, Convergence is one cell that is influenced by many others because it receives synaptic input from hundreds to thousands of neurons

T/F: this is Divergence: One cell influences many others

True, Divergency influences many others because its a single neuron that can communicate with a synapse upon many targets

What is summation?

PSP coming together (summing) to form an AP as it passes threshold and depolarizes

To get an AP you want ____ to summate

PSP

What is Temporal Summation?

The increase of frequency of input (coming from a given neuron)

What is Spatial Summation?

Input from 2 or more presynaptic neurons (to induce the response)

Is this summation bad? (Excitatory & Inhibitory)

No this is not bad, there are times we want to inhibit postsynaptic targets

DON’T REALLY NEED TO KNOW: Why do we want to inhibit postsynaptic targets?

To quiet down the target like in Parkisons

Neurotransmitters

chemical thats released by neurons this chemical can be norepinephrine, glycine, dopamine, etc.

T/F: The Electrical Synapse requires neurotransmitters

No the Electrical Synapse does not require neurotransmitters

Gap Junction

Allows the signal to travel from one cell to the other cell

What can pass through gap junctions?

AP pass through gap junctions, as an AP can occur in one cell and travel to the adjacent cell and cause that cell to fire off an AP