Lecture 2

Question 1

What is the dip below resting potential after repolarization?

Answer 1

Hyper-polarization or after hyperpotential. So much K+ flows out of the cell that the potential dips below resting potential (-70 mV)

Question 2

Which direction does the depolarization wave move?

Answer 2

Towards the axon terminal (anterograde)

Question 3

At what rate does the depolarization wave occur?

Answer 3

1 meter/sec

*This is too slow

Question 4

What is the solution to a slow depolarization rate?

Answer 4

Myelinated axons

Question 5

What is the depolarization wave?

Answer 5

One section of a neuron is initial depolarized from a stimulus which then causes the depolarization of the next portion of the neuron and so on…

Question 6

What is myelin made from?

Answer 6

Glial Cells (part of the CNS - oligodendrocytes)

Question 7

How does myelin increase the transmission of action potentials?

Answer 7

Myelin insulates axons which allows for saltatory conduction. This allows the action potential to “jump” from section to section on an axon instead of having to go across the whole thing - therefore increasing the transmission of the action potential to 100 m/sec

Question 8

What is a node of ranvier?

Answer 8

Space in between the myelin on an axon. Where the action potential “jumps” and where ion channels are located

Question 9

If an axon has a thick myelin sheath, it will have a ____ action potential

Answer 9

Fast

Question 10

What disease does demyelination in the CNS cause?

Answer 10

Multiple Sclerosis

Question 11

What disease does demyelination in the PNS cause?

Answer 11

Guillian-Barre Syndrome

Question 12

What drugs block Na+ channels?

Answer 12

Local anesthetics:
LidoCAINE
NovoCAINE
CoCAINE
(puffer fish toxin - tetrodotoxin makes lips go numb if you eat it by blocking Na+ channels)

Question 13

List the steps of Excitatory/Inhibitory Post Synaptic Potentials (EPSP/IPSP)

Answer 13

1. Action potential in pre-synaptic neuron
2. Ca2+ channels OPEN
3. Influx of Ca2+
4. SNARE protein complex dissolves
5. Exocytosis of neurotransmitters
6. Neurotransmitter diffusion
7. Neurotransmitter binds to its receptor on the post synaptic neuron - this causes either:
   - Influx of Na+ or Ca2+ = EPSP
   - Influx of Cl- or Efflux of K+ = IPSP

Question 14

What is the role of the SNARE protein complex?

Answer 14

Holds the synaptic vesicles in place which is where the neurotransmitters are

Question 15

What end of a neuron is the presynaptic membrane?

Answer 15

Axon Terminal

Question 16

What could a postsynaptic membrane be on?

Answer 16

• Neuron (dendrite, axon or soma)
• Muscle cell
• Gland

Question 17

What causes an Excitatory Post-Synaptic Potential (EPSP)?

Answer 17

Influx of Na+ or Ca2+

Question 18

What causes an Inhibitory Post-Synaptic Potential (IPSP)?

Answer 18

Influx of Cl- or Efflux of K+

Question 19

How many EPSP do you need to generate an action potential?

Answer 19

50-100

Question 20

Approx. how many mV is one EPSP?

Answer 20

0.2-0.4 mV