Nervous System - Nerve Transmission

Question 1

What is potential + different types

Answer 1

Potential - the charge value

Resting potential
Active potential
Threshold potential
Refractory period

Question 2

Resting potential

Answer 2

-70 millivolt
Na+ voltage channel close not permeable
K+ ion channel open permeable

Na ions high out cell low in cell
K ion high in cell low out of cell

Due to:
1)Negative charge protein + ions

2)Na+/K+ pump on axon - actively pump 3 Na+ out of cell, 2 K+ into cell per ATP = charge decrease

3)K+ diffuse out until equilibrium of diffusion + electrochemical attraction force = charge decrease

Question 3

Action potential (depolarisation)

Answer 3

+40 mv at peak
Threshold = -55mv
Na+ channel open
K+ channel close

Happens when:

1)Charges gradient changed by NT enough to go above threshold potential

2)open Na channel to trigger saltatory conduction (so even if stimulus too high doesn’t matter) close K channel

3)positive charge by Na carry along axon = more Na channel opens

Membrane depolarised (positive charge inside negative outside)

Question 4

Refractory period (re-polarisation)

Answer 4

Happens after action at a node of Ranvier
Lower than -70mv

Due to:
1)K channel open - out flux (too quickly) = decrease charge (known as hyperpolarisation)
2)Na channel close - actively pumped out
3)Na/K pump will revert change back to resting potential

Important since:
Prevent overstimulation
Prevent impulse from going other way

Question 5

Saltatory conduction

Answer 5

Jumping of electrical impulse from excess positive charge from sodium from one node of Ranvier to other via myelin sheath insulation

-pumps insulated by myelin sheath doesn’t need to work

Question 6

All or nothing principle

Answer 6

Either an action potential will trigger

Or not: ions released will be recycled by Na/K pump

Question 7

What happens if stimulus receive is higher than normal

Answer 7

Action potential still peaks at 40mv

But more neurones will be active

Question 8

Myelination on speed of conduction + energy required

Answer 8

Myelinated
-faster (saltatory conduction), need less energy (less pumps to power)

Unmyelinated
-slower (no skips), need more energy

Question 9

Axon diameter on speed of conduction + energy needed

Answer 9

Greater:
-faster (less resistance to ions = more pumps + channel for ions), need more energy (more pumps)

Less:
-slower (resistance + less pumps and channel), less energy needed