Neuro Exam 1 - Electrical Communication

Electrical Properties of Neurons

What are postsynaptic potentials?

Chemical input from other cells that cause local changes in electrical charge.

Where are postsynaptic potentials located in the neuron?

The dendrites and Soma

What is an action potential?

if these changes are big enough t raise the voltage at the initial segment of the axon (AKA the Axon Hillock) beyond a certain threshold, then an action potential is generated and conducted down thhe length of the axon

How is an action potential generated?

If the spatial and temporal summation of PSPs depolarizes the axon hillock to its threshold (around ~40mV), then an action potential is generated and conducted down the length of the axon

What is the all or nothing principle?

Characterized by either a complete response or by a total lack of response or effect, depending on the strength of the stimulus.

What is resting potential?

The inside of a neuron has a negative electrical charge relative other the outside

What are the electrical properties of a neuron due to?

Low gradient, movement of ions across the cellular membrane

What are Ion Channels?

Proteins that span the membrane and allow ions to pass through from one side to the other.

What are the three types of ion channels?

Selective or Semi-Selective, Gated, and Constantly Open channels.

What are the two forces that determine whether an ion channel will permit ions to enter or exit the neuron?

Diffusion (aka chemical pressure) and Electrostatic force.

Define Diffusion (Chemical Pressure)

Particles will tend to move from where they are more concentrated to where they are less concentrated until they are uniform in solution.

Define Electrostatic force?

One of the four fundamental forces of nature, causes ions to move away from similar charge and toward opposite charge. Voltage is a measure of the potential for this force to move a charged particle.

What is the sodium/potassium pump?

The pump that pulls 2 K+ ions into the cell for every 3 Na+ ions that it removes from the cell.

What powers Sodium/Potassium exchanges?

One molecule of ATP powers every one of these exchanges

Is the sodium/potassium pump always active?

The sodium/potassium pump is always active.

When is the potassium gradient at equilibrium?

At resting potential

What is hyper polarization?

When the charge inside the neuron becomes more negative

When does hyper polarization occur?

When positively charged ions enter or negatively charged ions exit.

What are iontropic receptors?

Ion channels that open when neurotransmitters bind to them.

How do ionotropic receptors impact signals?

Convert chemical signal into electrical signal

What is an example of an inotropic receptor and where it gets its name from.

Nicotinic Acetylcholine Receptor, gets its name from the face that the drug nicotine binds to the receptor and causes it to open, mimicking the action of acetylcholine.

Excitatory Postsynaptic Potentials (EPSPs)

Ionotropic receptors allow positively charged ions (i.e. Na+) into the neuron, causing a brief, local depolarization around the synapse.

Inhibitory postsynaptic potentials (IPSPs)

ionotropic receptors allow negatively charged ions (i.e. CI-) into the neuron causing a brief, local hyperpolarization around the synapse.

Are the postsynaptic potentials graded and do they last over time and distance?

Yes they’re graded and they diminish quickly over time and distance

Define Spatial Summation?

Combining the influence of PSPs across space.

Define Temporal Summation?

Combining the influence of PSPs across time.

How does the rising phase of action potential occur?

Voltage-gated sodium channels open to allow Na+ ions into the axon.

When are voltage-gated sodium channels open?

When the voltage on the interior of the axon is between threshold and around +40mV

When are voltage-gated sodium channels closed?

When the reach the high end of that range(which is close to equilibrium for sodium), they close and stop allowing Na+ into the axon.

What happens during the falling phase of the action potential?

The charge inside the axon returns to the normal resting potential (after briefly dipping below it).

How are voltage-gated potassium channels opened?

The positive change that occurs during the rising phase opens voltage-gated potassium channels

What is the refractory period?

A brief period in which voltage-gated sodium channels don’t open again

Can the action potential travel in multiple different direction?

The action potential can only travel in one direction.

Can the speed of action potentials vary between neurons? Within a neuron?

The speed can vary between neurons but not within neurons

What generates the action potential in a myelinated axon?

The nodes of ranvier is where the action potential is generated in a myelinated axon.

Define Saltatory Conduction

How the action potential jumps from node to node of a myelinated axon

What can happen when myelin is damaged?

Without the insulation provided by myelin, the diffusion of Na+ becomes less efficient, slowing the action potential or eliminating it completely.

If a drug has -caine in its name, what does it act as?

A local anesthetic

How do local anesthetics influence the action potential?

Temporarily prevents voltage-gated sodium channels from working

What is the role of voltage-gated calcium channels?

Open and allow Ca2+ ions into the terminal in response to depolarization caused by the action potential.

What happens to the synaptic vesicle of a voltage gated calcium channel when calcium is detected?

The vesicle ruptures snd ejects neurotransmitter into the synaptic cleft.