4. Brain Mechanisms And Behaviours III

Question 1

A message moves through a neuron by

Answer 1

Action potentials

Question 2

What is the charge of the inside of a neuron

Answer 2

The intracellular fluid is NEGATIVELY charged

Question 3

What is the charge of the outside of a neuron

Answer 3

POSITIVELY Charged

Question 4

What ions are found inside the neuron

Answer 4

A- and K+ (organic ions/proteins and potassium ions)

Question 5

Molecules of high concentration tend to move to areas of low concentration

Answer 5

Diffusion

Question 6

What is electrostatic pressure

Answer 6

Same charges repel, opposite charges attract

Question 7

a high concentration of potassium on the inside and low concentration on the outside means

Answer 7

Potassium ions will move from the inside of the cell to the outside; however because the inside of the cell is negative and potassium is positive the potassium stays attracted to the inside, hence it stays in

Question 8

Why do the organic amines A- stay in even though there is low concentration of them outside the cell and they are being repelled by the negative inside

Answer 8

Because the amine molecules are too big

Question 9

What ions are on the outside of a neuron cell

Answer 9

Na+ sodium ions
Cl- Chloride ions

Question 10

Cl- is on the outside and due to the force of diffusion they are

Answer 10

Pushed into the cell because there is a low concentration of Cl- ions on the inside, however the electrostatic pressure pushes most of them back out because opposite charges repel (neg inside and neg chloride) and positive charges attract (positive outside and negative chloride.

Question 11

How come sodium’s get pushed in

Answer 11

Because they are + so due to electrostatic pressure the negative inside attracts them, and because due to the force of diffusion Na+ will go from an area of high concentration (outside) to low conc (inside).

Not all of them tho most go in then get pushed back out because of the sodium potassium pump/transporter situated in the cell membrane.

Question 12

For every 2 potassium’s sent into the cell from the outside through the pump, the pump will push out

Answer 12

3 sodium ions

Question 13

So basically the pump is there to maintain

Answer 13

Equilibrium/ negativity on the inside and positivity on the outside

Question 14

When there is no communication between neurons and they are working non their ion pumping/diffusion this is called the

Answer 14

Resting potential

Question 15

The electrical charge on the membrane is called the

Answer 15

Membrane potential

Question 16

The term potential refers to all the stored up source of energy and in the neuron cell this energy is

Answer 16

Electrical energy

Question 17

The difference between charges on the outside and inside yields

Answer 17

Potential which is again a stored up source of nrg, specifically electrical nrg for the neuron cell

Question 18

If we want to reduce membrane potential (depolarization)= reduce energy= reduce the exchange of charges then we

Answer 18

Reduce the difference between the outside and the inside charges by inserting positively charged ions inside the axon leading to depolarization

Question 19

The difference between the inside and outside is __ milli volts

Answer 19

-70

Question 20

Is we add positive charge on the inside (depolarization) the new difference is reduced and now less negative meaning the less

Answer 20

The difference between the outside and inside of the neuron cell, this way we reduce the membrane potential.

Question 21

If we add enough positive charge to the inside of the neuron (stimulus applied) it will eventually stop going back down to -70 and start moving up toward action potential. This value from reduction that we reached that would cause it to go high up is called the

Answer 21

Threshold of excitation/ excitation point

Question 22

The graph will go up to __ milli volts after excitation is reached

Answer 22

Almost +40

Question 23

The whole process of neg becoming positive in the inside/the other way around is called action potential, its the way back down on the graph and it takes _ msec to complete

Answer 23

2

Question 24

What stimulates the mechanism of action potential

Answer 24

When the pre synaptic neurotransmitter bind to the post synaptic cell and action potential goes through to the next cell

Question 25

Another type of protein molecules allows ions to enter and leave cells, these protein molecules provide

Answer 25

Ion channels which contain passages (pores) that can open and close. When the ion Chanel is open, a particular ion can flow through the pore and therefore enter or leave the cell (these ion channels are the same ones that wouldn’t allow molecules like sodium to enter the cell; however once the threshold of excitation is reached the channels open up allowing sodium to enter= more positive inside the cell making the inside positive if a lot manage to go in

Question 26

Know the stages after threshold excitation (adding enough positive ions to the axon/stimulus/changing the charge on the inside)

Answer 26

Na+ channels open, Na begins to enter the cell making the inside more positive

The potassium starts to leave because the inside is becoming too positive and equilibrium musty be reached, electrostatic pressure pushes K+ out cause k and na are both positive which mean they repel and diffusion pushes it out as well (prof never mentioned why diffusion pushes this out?)

At highest point no more sodium can go in (channels become refractory)

K+ will keep leave to the outside after the highest point until membrane potential returns back to normal/ to resting potential- when action potential finishes

K+ channels close
Na+ channels reset

Extra k+ outside diffuse away (hyperpolarization?)

Question 27

Remember these steps in image

Answer 27

Question 28

Answer 28

We consider this an axon and see how the action potentials move down it
The pins are stimulus to reach a threshold over and over again

Question 29

As action potentials move down the axon it remains

Answer 29

Constant in terms if size and intensity

Question 30

Why are action potentials constant

Answer 30

Due to saltatory conduction which means: because the axons are myelinated, action potentials can only be recreated within the unmyelinated parts then moves at a constant rate within the next Myelinated part till the next unmyelinated part where it must restart and be recreated like in the pins “axon” experiment

Question 31

The unmyelinated parts of the axon are called the

Answer 31

Nodes of ranvier (the only place action potential can be created)

Question 32

Know this

Answer 32

This basic law of axon allows conduction law states that an action potential either occurs or it does not occur.

And once triggered it is transmitted down the axon to its end.

An action potential always remain the same size, without growing diminishing.

When an action potential reaches the terminal buttons it branches out to the several terminal buttons, however the intensity stays the same, initiating the movement of the vesicular for synaptic transmit ion to take place

Question 33

Saltatory conduction is

Answer 33

When action potential starts and moved in the nodes of ranvier only and not the other parts

Question 34

The advantages of saltatory conduction are

Answer 34

Economic in terms of Energy (save the energy required to get rid of sodium entering the axon since it enters only at the Nodes of Ranvier) meaning it saves energy when its in specific areas because it reduces action potentials saving energy have which is imp because the sodium potassium pump as well as becoming electropositive then electronegative is costly to the cell (takes a lot of nrg)

Speed (conduction of an action potential is faster in myelinated axon because it is only transmitted between the nodes making it very fast. The faster the better because it allows us to react faster)