Lecture 5 (brain's signalling systems)

Question 1

The first step in chemical neurotransmission?

Answer 1

The action potential is propagated over the presynaptic membrane.

Question 2

The second step in chemical neurotransmission?

Answer 2

Depolarization of the presynaptic terminal leads to influx of calcium.

Question 3

The third step in chemical neurotransmission?

Answer 3

Calcium promotes exocytosis, the fusion of vesicles with the presynaptic membrane, which releases transmitter into the cleft.

Question 4

The fourth step in chemical neurotransmission?

Answer 4

The binding of transmitter to receptor molecules in the postsynaptic membrane opens channels, permitting ion flow and initiating an excitatory or inhibitory postsynaptic potential.

Question 5

The fifth step in chemical neurotransmission?

Answer 5

Excitatory or inhibitory postsynaptic potentials spread passively over dendrites and the cell body to the axon hillock.

Question 6

The sixth step in chemical neurotransmission?

Answer 6

Enzyme present in the extracellular space breaks down excess transmitter or reuptake of transmitter slows synaptic action and recycles transmitter for subsequent transmission.

Question 7

The seventh step in chemical neurotransmission?

Answer 7

Transmitter binds to autoreceptors in the presynaptic membrane.

Question 8

The generation of an action potential? (Dansk)

Answer 8

• For at kunne få et aktionspotentiale, er der nødt til at være påvirkninger af samme neuron på samme tid. Det skal ske for at nå fyringstærsklen.
• Specifik aktivitet på flere neuroner på samme tid eller den samme aktivitet gentagne gange på samme neuron for at skabe aktionspotentiale og nå fyringstærsklen. Det skal være så stort, at det adskiller sig fra baggrundsstøjen.

Question 9

How is an excitatory postsynaptic potential generated?

Answer 9

Stimulation of a presynaptic neuron causes it to produce an all-or-none AP that spreads to the end of the axon, releasing transmitter. After a brief delay, the postsynaptic cell displays a small local depolarization, as natrium channels open to let the cations in.

Question 10

How can an excitatory postsynaptic potential lead to an AP?

Answer 10

If EPSPs are elicited by many neurons that converge on the postsynaptic cell, these potentials can produce a depolarization large enough to reach threshold and trigger an AP.

Question 11

Myelinated neurons vs unmyelinated neurons?

Answer 11

• Myelinated neurons: increases the speed of the AP. Passive transportation where the myelin is. Restart of the AP in the nodes of Ranvier.
• Unmyelinated neurons: Natrium entry locally depolarizes the axon, sufficiently depolarizing the adjacent region to open more of the voltage-gated natrium channels, re-creating the AP there, and so on, down the axon. A patch of natrium channels behind the AP are temporarily refractory.

Question 12

How does an AP travel along the axon?

Answer 12

The action potential is regenerated along the length of the axon. One action potential strongly depolarizes the next adjacent axon segment. This creates a new action potential, which in turn depolarizes the next patch of membrane and so on.

Question 13

Who can activate a receptor?

Answer 13

A receptor can only be activated by one specific transmitter.

Question 14

Who can activate a neuron?

Answer 14

A neuron can be activated by multiple transmitters.

Question 15

Ionotropic receptors?

Answer 15

directly control an ion channel.

Question 16

Metabotropic receptors?

Answer 16

recognize the synaptic transmitter, but they do not directly control ion channels. But they activate G proteins.

Question 17

Neurons that wire together, fire together?

Answer 17

When a presynaptic neuron repeatedly activates a postsynaptic neuron, the synaptic connection between them will become stronger and more stable.

Question 18

Neurophysiology?

Answer 18

The study of electrical and chemical processes in neurons.

Question 19

Where are the cells more negative?

Answer 19

They’re more negative on the inside than on the outside of the cell.

Question 20

Anions?

Answer 20

Negatively charged ions.

Question 21

Cations?

Answer 21

Positively charged ions.

Question 22

What is the neuron’s resting membrane potential?

Answer 22

Between -50 and -80 mV.

Question 23

Ion channel?

Answer 23

An important type of membrane-spanning protein. It allows ions of a specific type to pass through the membrane.

Question 24

Sodium-potassium pump?

Answer 24

Neurons use a mechanism that pumps Na+ out of the cell for every two K+ ions pumped in. This consumes energy.

Question 25

Which kind of ion channels does the cell membrane of a neuron have?

Answer 25

Ion channels which allow K+ to cross the membrane at all times.

Question 26

Does acetylchlone work as exhibitoy or inhibitory?

Answer 26

BOTH!

Question 27

How does ACh work exhibitory?

Answer 27

When as exhibitory, it will open channels for Na+ and K+ - in this way, ACh released onto muscle fibers excites them to contract.

Question 28

How does ACh work inhibitory?

Answer 28

At inhibitory synapses, it opens Cl- channels, thereby hyperpolarizing the membrane and making an action potential less likely.

Question 29

Degradation?

Answer 29

when a transmitter is broken down and thus inactivated by a special enzyme.

Question 30

Reuptake?

Answer 30

when transmitter molecules are rapidly cleared from the synaptic cleft by being taken up unto the presynaptic terminal.

Question 31

What happens when a seizure takes place?

Answer 31

broad swaths of the brain start firing in simultaneous waves of excitation.