Neuronal membrane and action potential

Question 1

What are the properties of a neuron?

Answer 1

• Have a resting membrane potential (negative compared to the extracellular environment)
• Have a concentration gradient
  -Relatively high membrane permeability to K+
• 3 Na+/2K+ ATPase pump helps to maintain concentration gradients
• Electric gradient

Question 1

What is the principle for generating an Action Potential?

Answer 1

All or nothing response- AP only occurs when threshold voltage is reached.

Question 2

What are voltage-gated Na+ channels?

Answer 2

• Voltage sensitive channels that sit in the cell membrane
• Exist in four states (Resting(inactivated/ Open (activated), Inactivated, Closed and inactivated)
• Blocked by tetrodotoxin (TTX) - can result in weaking and paralysis of muscles

Question 3

What are the properties of a neuron (membrane potential)?

Answer 3

• Excitable and can alter their MP in response to a trigger which can generate an AP
• Information spreads along the axon as a wave of electrical charge

Question 4

How is electrical activity spread?

Answer 4

• As a wave of electrical charge in a directional manner.

Question 5

How do neurones communicate with each other?

Answer 5

By releasing small quantities of specialised chemicals called neurotransmitters at the synapse.

Question 6

What are examples of neurotransmitters?

Answer 6

• Noradrenaline
• Acetycholine

Question 7

What is summation?

Answer 7

When neurones receive information simultaneously from multiple sources. If the membrane potential is changed sufficiently then ap will occur.

Question 8

What regulates the speed of communication in the nervous system?

Answer 8

• Diameter of axon
  -Myelination
• Length of axon

Question 9

What is saltatory conduction?

Answer 9

When an ap jumps from node to node.

Question 10

What is Multiple sclerosis?

Answer 10

-Loss of myelin in the CNS
- Autoimmune disease
- attacks and hardens myelin sheath
- Slows nerve conduction
- Episodes of weakness,, lack of coordination, vision and speech disturbance
- Tested by examining conduction velocity of optic nerve

Question 11

What is Guillain-Barre?

Answer 11

• Loss of myelin in PNS
• Autoimmune
• Attacks peripheral nerves innervating muscle and skin
• Characterised by slowing/falling of AP’s that innervate the muscles
• Tested by stimulating peripheral nerve - measure time it takes to evoke a response (e.g. muscle twitch).