Neurotransmission (1)

Question 1

What are the names of the researchers who decided “animal electricity” was present in the nerve? And in what year?

Answer 1

Lucia and Luigi Galvani
1781

Question 2

What is the name (and year) of the researcher who found electricity makes criminals’ corpses twitch

Answer 2

Giovanni Aldini (Galavani’s nephew)
1802

Question 3

Electrical currents are…

Answer 3

Flows of charged particles

Question 4

____ charges repel, ____ charges attract

Answer 4

Like, Opposite

Question 5

Currents only flow through…

Answer 5

Materials that conduct electricity

Question 6

Voltage is a measure of how much p____ there is for c____ to m____

Answer 6

How much potential there is for charge to move - how much stored electrical energy

Question 7

Conductance is a measure of what?

Answer 7

How well charge can flow

Question 8

The amount of current that flows depends on what two things?

Answer 8

1. How much potential there is
2. How easy it is for the current to flow through the circuit

Question 9

What is Ohm’s Law?

Answer 9

Current (charge per second or amps) = Potential (volts) x Conductance
OR
Current = Potential / Resistance

Question 10

What is meant by resistance?

Answer 10

How much a material resists current flow

Question 11

Around how many times slower is nerve conductance than electricity flows down a wire?

Answer 11

1 million

Question 12

Currents flow down nerves as a wave of charge movement. This wave of current down an axon is known as what?

Answer 12

The action potential

Question 13

How do cells signal electrically?

Answer 13

Movement of ions
Electrically charged particle (e.g. sodium chloride = Na+ and Cl-)
Different sizes

Question 14

Why do cells have a baseline voltage difference across the membrane?
1. W____ is slightly p____ - it has n____ bits and p____ bits, which means the c____ stuff can b____ to it and therefore things like i____ are s____ in water - also the heads of p____ molecules
2. T____ aren’t c____ so they don’t b____ to water and s____ together forming this layer inside the membrane, so water s____ things can’t get through.

Answer 14

1. Water is slightly polarised - it has negative bits (the oxygen) and positive bits (the hydrogens) which means the charged stuff can bind to it and therefore things like ions are soluble in water – also the heads of these phospholipid molecules
2. Tails aren’t charged so they don’t bind to water and stick together forming this layer inside the membrane, So water soluble things can’t get through

Question 15

What ions are on the inside and outside of cells?

Answer 15

Outside:
. Na+
. Cl-
. Bit of Ca2+
Inside:
. Proteins (-ve)
. K+

Question 16

What do ion channels do?

Answer 16

Let ions of the specific channel pass through the membrane

Question 17

Which way does the potassium concentration gradient go?
How does the create an electrical gradient?

Answer 17

High conc of K+ inside the cell, low conc of K+ outside the cell
Now the inside is negative relative to the outside. This stops more potassium leaving the cell.
An electrochemical gradient is created

Question 18

Briefly describe the concept of equilibrium potentials, and discuss how negative and positive potentials affect what ions move through the cell membrane
Which direction an ion f____ is dictated by c____ d____ across the m____ and the ion c____ - when both are b____ theres no n____ flow, the membrane potential at which this happens is called the e____ p____.

Answer 18

Which direction an ion flows is dictated by concentration difference across the membrane and the ion charge – when both are balanced there’s no net flow – the membrane potential (voltage) at which this happens is called the equilibrium potential

Lots of K inside cell so will tend to leave, and membrane potential has to get pretty negative to stop the K+ from leaving the cell – so negative equilibrium potential
Lots of sodium outside cell, so tends to go into cell, and will do that very readily when the inside is negative relative to outside – but if membrane becomes really positive, ions will stop entering
Lots of chloride outside so concentration gradient is driving chloride entry to the cell but negative potential inside the cell repels chloride entry

Question 19

Define equilibrium potential (E)
What are the two things that dictate E?

Answer 19

Potential across membrane at which there is no net flow of an ion
E dictated by concentration difference and ion charge

Question 20

What does the Nernst equation calculate?

Answer 20

Equilibrium potential for an ion
Says that the equilibrium potential for an ion depends on the temperature, the charge on an ion and the concentration gradient across the membrane of an ion

Question 21

What is the membrane potential set by?
E____ g____ and p____ of membrane to different i____

Answer 21

Electrochemical gradient and permeability of membrane to different ions

Question 22

Why is the resting membrane potential of neurons near to the equilibrium potential for potassium?

Answer 22

At rest the membrane is more permeable to potassium than any other ion

Question 23

What will happen to the membrane potential if the permeability of the membrane to an ion increases?

Answer 23

The membrane potential will move towards the equilibrium potential for that ion

Question 24

Ion gradients are maintained via s____-p____ p____

Answer 24

Via sodium-potassium pumps

Question 25

Intracellular transmission is ____
Intercellular transmission is ____

Answer 25

Intra = electrical
Inter = Chemical

Question 26

What can electrical signals be measured with?

Answer 26

A voltmeter

Question 27

Resting membrane potential is ____

Answer 27

Negative

Question 28

Define action potential
Wave of t____ d____ that travels d____ the a____

Answer 28

Wave of transient depolarisation that travels down the axon

Question 29

What is the resting membrane potential in millivolts?

Answer 29

~-70mV

Question 30

What happens to the membrane potential when only
1. K+ channels
2. Na+ channels
are open?

Answer 30

1. , K+ leaves the cell, until the membrane potential reaches about -80mV
2. Na+ enters the cell, making the membrane potential more positive, until the membrane potential is about +60mV

Question 31

At what voltage are voltage-gated sodium channels and voltage-gated potassium channels activated at?

Answer 31

Sodium = -55mV
Potassium = +30mV

Question 32

What are some properties of action potentials?

Answer 32

Wave of transient depolarisation of the cell’s membrane
Conveys a fast signal from one place to another in the body
Generated by changes in membrane permeability due to opening and closing of voltage ion channels
Self-regenerating electrical wave
Is a transient change (~1ms) in membrane potential
occurs only if a threshold membrane potential is achieved in the axon initial segment (axon hillock), which transiently opens voltage gated sodium channels

Question 33

What are the five action potential events?
1. T____ p____ reached
2. D____ due to opening of s____ channels
3. D____ due to i____ of s____ channels and opening of v____-gated p____ channels
4. H____ as v____-gated p____ channels are still o____
5. S____ channels released from i____

Answer 33

1. Threshold potential reached
2. Depolarisation due to opening of sodium channels
3. Depolarisation due to inactivation of sodium channels and opening of voltage-gated potassium channels
4. Hyperpolarisation as voltage-gated potassium channels are still open
5. Sodium channels released from inactivation (can fire AP again)

Question 34

What is the scientific word for when all sodium channels are inactivated?

Answer 34

Absolute refractory period

Question 35

What is the term for when some sodium channels are inactivated?
R____ r____ p____

Answer 35

Relative refractory period
Some sodium gates are inactivated, potassium open and the neuron is repolarising

Question 36

Action potentials are ____ or ______

Answer 36

All or nothing
(Must reach a threshold point)