1. Speed Of Conduction

Question 1

What 3 factors affect speed of conduction of action potentials ?

Answer 1

1. Myelination
2. Axon diameter
3. Temperature

Question 2

What does it mean by something being myelinated ?

Answer 2

They have myelin sheath an electrical insulator.

In the peripheral nervous sustem the sheath is made of Schwann cells and between these cells aw tiny patches of bare membrane called nodes of ranvier

Sodium ions concentrated at nodes of ranvier

Question 3

Define myelin sheath

Answer 3

Layer of Schwann cells around neurone acts as electrical insulator and speeds up conduction of nervous impulse

Question 4

Define node of ranvier

Answer 4

Tiny area of bare cell membrane on surface of myelinated neurone where depolarisation can take place

Question 5

Define Schwann cell

Answer 5

Type of cell that makes up the myelin sheath around neurones

Question 6

What are dendrites ?

Answer 6

Extensions of cell body that connect with other neurones

Question 7

Define saltatory conduction

Answer 7

Process in myelinated neurones by which nervous impulses ( depolarisation ) travels betweeeh nodes or ranvier as the sodium ions can get through the membrane.

The neurones cytoplasm conducts enough electrical charge to depolarise the next code so the impulse jumps from
Node to node - really fast

Question 8

What happens in non-myelinated neurone ?

Answer 8

Impulse travels as a wave along whole length of axon membrane - depolarisation along whole length of membrane

This is slower that’s saltatory conduction

Question 9

2. Axon diameter

Answer 9

Action potentials conduction wuicker along axon diameters which are bigger because there’s less resistance to the flow of ions than in the cytoplasm of smaller axon

Less resistance, depolarisation reaches other parts of neurone wuicker

Question 10

3. Temperature

Answer 10

Speed of conduction increases as temp does as ions diffuse faster

Only increases up to certain point though at 40 degrees - after than the proteins denature and speed decreased

Question 11

When are the sodium ion channels open and closed ?

Answer 11

Closed at rest ( it’s the sodium potassium pump and potassium ion channels which are open at rest )

Open when stimulus arrives

(Sodium ion channels close at repolarisation)
(Potassium ion channels close at hyperpolarisation)