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Flashcards in Nerves 4 Deck (26):
1

What channels open when the threshold potential is reached?

- Voltage gated Na channels open
- Sodium moves into the cell and depolarises

2

How does repolarisation occur?

- Voltage gated potassium channels open and potassium leaves the cell

3

How do local anaesthetics work?

- Block voltage gated Na channels
- AP's can't be generated

4

3 properties of action potentials?

- Self propagating
- All or none
- Stimulus intensity shown by frequency of AP's

5

How do AP's move down the axon?

- Voltage gated channels open in one area
- Causes significant depolarisation in the next part
- Voltage gated Na channels open in this bit and so on

6

Why does local current not cause the AP to travel back up the cell?

- Voltage gated Na channels have a refractory period where they can't open

7

What 2 ways are there that allow neurones to transmit AP's ASAP?

- Large axons
- Myelination

8

How do large axons increase conduction velocity?

- Reduce resistance from the cell membrane (axial resistance)

9

What is it that limits rate of conduction?

Refractory period

10

With reference to the refractory period, how do large axons speed up signals?

- Less Na channels required

11

What is myelin?

Membrane of schwann cells or oligodendrocytes

12

What nerves do Schwann cells myelinate?

Peripheral nervous system

13

Where do oligodendrocytes myelinate?

In the CNS

14

What are the nodes of ranvier?

- Unmyelinated axon in between myelinated axon
- Where voltage gated Na channels are found in the myelinated cell

15

What does myelination stop?

Leakage of the signal

16

What is an example of a de myelinating disease?

- MS
- Gulliane Barre

17

What does demyelination cause?

- Local currents decay faster
- Next node won't be depolarised
- Signal won't be sent

18

How are different nerve fibres classed?

A alpha to A delta
B etc
C etc
- They are from large to small

19

What classification is given to the largest nerve fibres?

A alpha

20

What are 2 rules of A alpha fibres

- Sensitive to anoxia
- Least susceptible to anaesthetic

21

What is anoxia?

Lack of oxygen

22

What are 2 rules of C fibres?

- Least susceptible to anoxia
- Most susceptible to anaesthetic

23

What fibres are the fastest conductors?

- C fibres

24

What fibres are the slowest conductors

- A alpha

25

What 2 functions do A alpha fibres have?

- Proprioreception
- Motorneurones

26

Function of C fibres?

- Heat
- 'Slow' pain