Second lecture and Third lecture

Question 1

What is the blood-brain barrier?

Answer 1

Selectively permeable barrier between blood and the brain through tight junctions in the walls of cells of the brain’s capillaries.

Question 2

What is the primary function of the blood-brain barrier?

Answer 2

Regulate and maintain the composition of the extracellular fluid in the brain.

Question 3

How do astrocytes contribute to the function of the blood-brain barrier?

Answer 3

They actively transport wanted nutrients across the walls for most chemicals.

Question 4

What problem can arise from the function of the blood-brain barrier?

Answer 4

It can be a problem for drugs that we want to get into brain tissue.

Question 5

What does the blood-brain barrier restrict?

Answer 5

Entry of chemicals or toxins that would interfere with the transmission of information between neurons.

Question 6

What does the blood-brain barrier actively transport back to the bloodstream?

Answer 6

Waste.

Question 7

What is the area postrema?

Answer 7

A region of weakness in the blood-brain barrier located in the medulla.

Question 8

What can be detected in the area postrema?

Answer 8

Poisons.

Question 9

What is the wall of the axon made of?

Answer 9

A special cell membrane

Question 10

What can we measure across the axon cell membrane?

Answer 10

Relative voltage difference (electrical potential)

Question 11

What is the electrical charge inside the axon at rest?

Answer 11

Negative

Question 12

What is the Resting State Potential when the axon is at rest?

Answer 12

Negative

Question 13

What is transmitted along the axon from soma to axon terminals?

Answer 13

Axonal Transmission (conduction) of signals

Question 14

What are the electrochemical signals sent by neurons called?

Answer 14

Action Potentials (APs)

Question 15

Where are Action Potentials usually triggered in a neuron?

Answer 15

Near the soma

Question 16

What do Action Potentials trigger at the axon’s terminals?

Answer 16

Release of neurochemicals

Question 17

What influences the behavior and neurobiology of recipient neurons?

Answer 17

Neurochemicals released from Action Potentials

Question 18

What is the electrochemical basis of the Action Potential easily measured as?

Answer 18

An extremely brief reversal of the voltage difference

Question 19

What ensures that the Action Potential travels in one direction along the axon?

Answer 19

Nature of the axon membrane and its local environment

Question 20

What is the ‘code’ used by the neuron to convey information?

Answer 20

Temporal pattern and sequence of many Action Potentials

Question 21

What does the All-or-none Law state about Action Potentials?

Answer 21

Firing of AP depends on a threshold

Question 22

How is the size of the Action Potential described?

Answer 22

Fixed in size for a given neuron

Question 23

What does the Rate Law explain about variations in axon transmission?

Answer 23

Variations in the rate of AP propagation represent variations in stimulus intensity

Question 24

Fill in the blank: The Action Potential is propagated at this exact, full voltage potential without _______.

Answer 24

decrement

Question 25

True or False: All Action Potentials are of different sizes.

Answer 25

False

Question 26

What is the resting potential of an axon?

Answer 26

-70mV ## Footnote The resting potential is the membrane potential of a neuron when it is not being altered by other neuronal activity.

Question 27

What happens during depolarization?

Answer 27

Membrane potential moves towards being more positive ## Footnote This is part of the process of action potential where the charge inside the axon becomes more positive.

Question 28

What is hyperpolarization?

Answer 28

Membrane potential becomes more negative than in resting state ## Footnote This occurs when the membrane potential dips below the resting potential.

Question 29

Define Action Potential (AP).

Answer 29

Brief electrical impulse that provides the basis for conduction along an axon ## Footnote The AP is characterized by a rapid reversal of polarity and a return to a negative state.

Question 30

What is the threshold of excitation?

Answer 30

Value of the membrane potential that must be reached to produce an action potential (e.g. -60mV) ## Footnote Without reaching this threshold, no action potential occurs.

Question 31

True or False: The action potential can be stopped once the threshold of excitation is reached.

Answer 31

False ## Footnote Once the threshold is reached, the action potential is generated and self-regenerates down the axon's length.

Question 32

How long does the action potential process take?

Answer 32

3-5ms ## Footnote This is the rapid duration of the action potential process.

Question 33

What is diffusion force?

Answer 33

Molecules distribute themselves evenly when dissolved, moving from high concentrations to low concentrations ## Footnote This principle explains how substances spread out in solution.

Question 34

What is electrostatic pressure?

Answer 34

Electrical force when substances are dissolved in water and split into charged particles (ions) ## Footnote This pressure affects the movement of ions in biological systems.

Question 35

What are cations?

Answer 35

Carry positive charge ## Footnote Cations are one type of ion that plays a critical role in action potentials.

Question 36

What are anions?

Answer 36

Carry negative charge ## Footnote Anions are the other type of ion that contributes to electrical activity in cells.

Question 37

What happens to ions with the same charge?

Answer 37

They repel each other ## Footnote This principle is fundamental to understanding ionic interactions.

Question 38

What happens to ions with opposite charges?

Answer 38

They attract each other ## Footnote This attraction is crucial for the formation of ionic bonds and electrical activity.

Question 39

What keeps Na+ levels high outside the axon?

Answer 39

Sodium-potassium pumps continuously pump out Na+ and pump in K+ ## Footnote This process helps maintain the concentration gradient necessary for action potentials.

Question 40

What primarily influences the movement of Na+ into the cell?

Answer 40

Both diffusion and electrostatic pressure ## Footnote These forces would normally push Na+ into the cell, but the resting membrane is not very permeable to Na+.

Question 41

What happens when the membrane becomes permeable to Na+?

Answer 41

The sodium channels open, allowing Na+ to rush inside the axon ## Footnote This influx leads to a rapid change in membrane potential, creating an action potential.

Question 42

What is the threshold in the context of action potentials?

Answer 42

The level of depolarization where the closed sodium gates open ## Footnote At this point, the process becomes all or nothing, allowing ions to transfer rapidly across the membrane.

Question 43

What occurs first once the threshold of excitation is reached?

Answer 43

Na+ channels open, allowing Na+ to rush inside the axon ## Footnote This initiates the action potential.

Question 44

What happens after the Na+ channels open during an action potential?

Answer 44

Voltage-dependent K+ channels open later, allowing K+ to leave the cell ## Footnote This is due to diffusion out of the cell.

Question 45

What occurs when the Na+ channels become refractory?

Answer 45

They block and won't open again until the membrane repolarizes to a negative inside ## Footnote This is critical for resetting the action potential cycle.

Question 46

What causes the membrane to return to resting potential?

Answer 46

Diffusion of K+ out of the cell ## Footnote This happens as the K+ channels remain open.

Question 47

What is the role of the Na+/K+ transporter after an action potential?

Answer 47

It removes new Na+ that leaked in and retrieves K+ that leaked out ## Footnote This helps restore the resting state of the neuron.

Question 48

How does action potential propagation differ in myelinated versus non-myelinated axons?

Answer 48

In non-myelinated axons, the AP regenerates along the axon; in myelinated axons, it jumps from node to node ## Footnote This is known as saltatory conduction.

Question 49

What are the advantages of myelination?

Answer 49

Faster conduction and more economic use of energy ## Footnote Myelin allows for action potentials to jump between nodes, reducing energy expenditure.

Question 50

Where do action potentials start in a neuron?

Answer 50

At the axon hillock ## Footnote This is the part of the axon next to the cell's soma.

Question 51

What happens at the terminal branches of the axon?

Answer 51

Action potentials influence synapses and neurotransmitter release ## Footnote This affects the neurobiology of recipient neurons.

Question 52

Fill in the blank: The electrical disturbance along the myelinated segment of the axon is ______.

Answer 52

decremental ## Footnote The voltage change gets smaller as it passes under the myelin.

Question 53

True or False: Action potentials can travel backwards along the axon.

Answer 53

False ## Footnote They only propagate forwards due to the refractory state of Na+ channels.