Week 3

Question 1

Method by which neurons communicate

Answer 1

Action potentials

Question 2

Membrane potential becomes less negative

Answer 2

Depolarization

Question 3

Membrane potential becomes more negative

Answer 3

Hyperpolarization

Question 4

First, the resting membrane potential is negative. Then, when the membrane potential reaches above threshold, an action potential is triggered. The membrane depolarizes in the rising phase, then re-polarizes in the falling phase. Then the membrane hyper polarizes during the undershoot. It can be impossible or difficult to initiate another AP. The membrane returns to resting potential.

Answer 4

Action potential steps

Question 5

Voltage gated, sodium and potassium channels, open and close as a function of the neuronal membrane potential. They are located along axon, hillock, axon membrane, and terminals.

Answer 5

Driving force of the action potential

Question 6

Sodium and potassium channels closed

Answer 6

Resting potential (channels)

Question 7

Voltage gated sodium channels open, sodium goes into the cell, which creates more depolarization.

Answer 7

Rising phase (channels)

Question 8

Voltage gated potassium channels, open slower than sodium channels, by the time they’re open, the cell is quite positive, causing potassium to flood out of the cell, makes the cell more negative, an activation gate closes, sodium can’t move.

Answer 8

Falling phase (channels)

Question 9

Potassium continues to leave the cell, causes, hyperpolarization, in resting potential, helps reset voltage gated sodium channels.

Answer 9

Undershoot (channels)

Question 10

In this period Neurons cannot fire again. This period Limits how frequently a neuron can fire. Accounts for unidirectional nature of action potential. Sodium channels can only open again once membrane potential hyperpolarizes.

Answer 10

Absolute refractory period (phases 2-3)

Question 11

In this period membrane potential becomes more negative than resting membrane potential. Neurons can fire again, but only with a strong stimulus. Ends when the neuron gets back to resting potential.

Answer 11

Relative refractory period (phases 3-6)

Question 12

When sodium channels open the local membrane potential depolarizes. Depolarization makes neighboring sodium channels open. Propagation moves forward only because recently open sodium channels are in active. In myelinated axons the AP is a faster process than in unmyelinated axons.

Answer 12

Action potential propagation

Question 13

Since action potentials are binary, the frequency and pattern conveys different info to the downstream neurons in circuit. The pattern is the temporal code. The frequency is the rate code.

Answer 13

Neural information code

Question 14

The point of contact between axon terminal and another neuron

Answer 14

Synapse

Question 15

The steps, through which action potential is converted to chemical signal and transmitted to postsynaptic neuron in circuit

Answer 15

Synaptic transmission

Question 16

1) presynaptic, neuron stores transmitters in vesicles, waiting to be released when an action potential reaches the presynaptic terminal (calcium channel)
2) when action potential triggers opening of calcium channels, they rush into the cell
3) the transmitter, binds to post synaptic, receptors, producing an EPSP. Some transmitters are already being broken down.
4) action potential ends, Neuro transmitters are broken down, EPSP didn’t reach threshold, so the postsynaptic neuron has returns to rest.

Answer 16

Steps in synaptic transmission

Question 17

Entering calcium releases vesicles from protein, anchors, and stimulates fusion with membrane

Answer 17

Exocytosis

Question 18

1) proteins on the vesicle and presynaptic cell bind to each other, docking, the vesicle
2) when calcium enters it binds to the docking proteins and activates vesicle fusion
3) Nero transmitters from vesicles diffuse out rapidly into the synaptic cleft

Answer 18

Steps of vesicular release

Question 19

Neurotransmitters bind to the channel. Channels open, ions flow in and out.

Answer 19

Ligand-gated ion channels

Question 20

Neuro transmitters find GPCR. G proteins subunits or intracellular messengers, modulate channels. Ion channels, open, ions flow in or out.

Answer 20

G-protein-coupled-receptors

Question 21

Open channel directories, relatively fast and short, effects are localized

Answer 21

Ionotropic

Question 22

Open channels, indirectly, uses chemicals, called second messengers, relatively slow acting, and long, lasting affects, effects are more widespread and varied

Answer 22

Metabotropic

Question 23

Produced when transmitter binds to a transmitter-gated channel selective for sodium or calcium. Allows for diffusion to temporarily push positive ions into the neuron, making it slightly more positive.

Answer 23

EPSP (excitatory postsynaptic potential)

Question 24

Produces when transmitter binds to a transmitter-gated channel selected for chloride. Allows for diffusion to temporarily push chloride into the neuron, making it slightly more negative.

Answer 24

IPSP (inhibitory postsynaptic potential)

Question 25

EPSP from two presynaptic event sum over time

Answer 25

Temporal summation

Question 26

EPSP from two separate presynaptic inputs sum over space

Answer 26

Spatial summation

Question 27

Junction of cell body in axon. Rich in voltage-sensitive channels. Where EPSPs and IPSPs are integrated. Where action potentials are initiated.

Answer 27

The axon hillock

Question 28

Very different way of cells connecting to each other. Pre-and post synaptic sells touch through connexons. Ions flow is bi directional. Doesn’t typically occur at axon terminals.

Answer 28

Gap junctions