Week 2 - Neurophysiology

electrical

electrical

Information flows within a neuron via ___ signals.

chemical

Information flows between neurons via ___ signals.

anions

negatively-charged ions

cations

positively-charged ions

three; two

The sodium-potassium pump pumps ___ sodium ions (Na+) out of the cell for every ___ potassium ions (K+) brought in

-70mv

At rest, what is the difference in voltage inside the cell compared to the outside?

polarized

Is a resting neuron polarized or nonpolarized?

inside

At rest, is potassium (K+) concentrated inside or outside of the cell?

outside

At rest, is sodium (Na+) concentrated inside or outside of the cell?

outside

At rest, is chloride (Cl-) concentrated inside or outside of the cell?

diffusion and electrostatic pressure

The membrane potential is a balance of what two forces?

out of

At rest, does diffusion push potassium ions (K+) into or out of the cell?

into

At rest, does electrostatic pressure push potassium ions (K+) into or out of the cell?

into

At rest, does diffusion push sodium (Na+) into or out of the cell?

into

At rest, does electrostatic pressure push sodium (Na+) into or out of the cell?

into

At rest, does diffusion push chloride (Cl-) into or out of the cell?

out of

At rest, does electrostatic pressure push chloride (Cl-) into or out of the cell?

depolarizes; positive

When a neuron ___, voltage-gated channels allow sodium to rush in (being pushed by both diffusion and electrostatic pressure). The membrane potential becomes ___ and an action potential is fired.

potassium (K+)

After an action potential fires, sodium stops rushing into the cell, but ___ ions continue to leave the cell, returning the membrane to its resting potential.

hyperpolarization

The refractory phase is a brief period of ___ following an action potential during which the membrane is less likely to produce another action potential.

(“cooldown” period)

depolarization of the cell membrane

What triggers an action potential?

sodium channels; into the cell; diffusion and electrostatic pressure; becoming positive

Once an action potential is triggered, which ion channel opens first? Which way does that ion flow? Which forces push it? What is happening to membrane potential as this ion flows?

potassium channels; membrane potential becoming positive (K+ channels are voltage-gated); out of the cell; diffusion and electrostatic pressure; becoming negative

Which ion channels open next? What makes them open? Which ions flow through these channels and in which direction? What forces are pushing these ions? What is happening to the membrane potential as this ion flows?

propagated

An action signal must be ___ down the axon.

myelin; node of Ranvier

___ insulates the signal until it can be repropagated at the next ___

membrane potential

Neurotransmitters change the receiving neuron’s likelihood of firing by altering the receiving neuron’s ___

receptors

protein molecules that react to neurotransmitter

dendritic spines

increase surface area for more synapses and receptors

synaptic vesicles

small sacks in terminal buttons that contain molecules of neurotransmitter

terminal buttons

When an action potential reaches the ___, synaptic vesicles fuse with the membrane and then burst open, spilling neurotransmitter into the synapse.

ligand

any chemical that attaches to a receptor

charge

Postsynaptic potentials are changes in the ___ of a postsynaptic neuron.

smaller

Are postsynaptic potentials larger or smaller changes than action potentials?

excitatory (EPSP)

What kind of postsynaptic potential brings a neuron closer to depolarization, and therefore more likely to fire an action potential?

inhibitory (IPSP)

What kind of postsynaptic potential hyperpolarizes a neuron, making it less likely to fire an action potential?

-55mv

What is the threshold that must be reached at the axon hillock of the postsynaptic neuron in order for it to generate an action potential?

Synaptic vesicles fuse to the membrane and burst, releasing neurotransmitters into the synaptic cleft. These neurotransmitters bond to ligand-gated receptors on the postsynaptic membrane and change the charge of the postsynaptic cell.

After an action potential has traveled down the axon to the terminal buttons, what happens next? How does that presynaptic neuron send a signal to nearby neurons?

If the signal received triggers an EPSP, the postsynaptic neuron is pushed towards depolarization. If enough EPSPs stack up, the threshold will be reached and an action potential generated.

If the signal received triggers an IPSP, the postsynaptic neuron is hyperpolarized and becomes less likely to generate an action potential.

If a postsynaptic neuron receives a signal, what happens?

reuptake

Most common means by which neurotransmitters are cleared from the synaptic cleft

terminal buttons of the presynaptic neuron

What part of which neuron (presynaptic or postsynaptic) is responsible for neurotransmitter reuptake?

enzymes

Another means of clearing leftover neurotransmitter from the synaptic cleft is deactivation by ___

autoreceptors

___ stop the release of neurotransmitters, allowing existing neurotransmitter to either bind to a receptor or be cleared