Lecture 3

Question 1

Depolarization due to action potentials decay rapidly as a distance from stimulus…

Answer 1

Increases

Question 2

Are single action potentials usually sufficient to carry information along a neuron?

Answer 2

Nah

Question 3

Why is it important that action potentials are propagation?

Answer 3

• initial AP starts a new AP in adjacent membrane
• each new AP is full strength and follows the same step
• allows for full strength APs to travel the full length of the neuron

Question 4

What is conduction velocity?

Answer 4

Speed at which APs are conducted away from initiation site

Question 5

What does conduction velocity depend on?

Answer 5

The time and length constants

Question 6

What is the time constant?

Answer 6

How fast membrane can depolarize to 63% of max AP voltage.

Question 7

What is the length constant?

Answer 7

How far depolarization travels before falling below 63% of max

Question 8

What does the time constant depend on?

Answer 8

• Depends on the number of channels

- depends on how well the membrane holds a charge

Question 9

What happens to the membrane resistance when there are more open channels?

Answer 9

-lower resistance, more ion flow, faster depolarization

Question 10

What happens to the membrane capacitance when there is less charge in the membrane?

Answer 10

-more transferred ions inside, faster depolarization

Question 11

For a smaller time constant, what would you want?

Answer 11

• more open channels

- less charge in the membrane

Question 12

How a longer length constant, what do you want?

Answer 12

• high resistance, less open channels, fewer ions leaking out
• more cytoplasm than membrane

Question 13

What is the length constant dependent on

?

Answer 13

• open channels

- internal resistance

Question 14

Can thick or thin nerves conduct impulses quicker>

Answer 14

THICK

Question 15

Increasing the diameter lowers the internal resistance which results in what?

Answer 15

Faster conduction

-higher length constant means faster conduction

Question 16

What combination of time and length constants would result in most rapid conduction?

Answer 16

Low time constant and high length constant

Question 17

What is it called when action potentials jump between the nodes of ranvier?

Answer 17

Saltatory conduction

Question 18

Why is saltatory conduction a thing?

Answer 18

• myelin doesn’t allow any ion flux at that part which increases membrane resistance and increases the length constant
• the ions then focus on the nodes which decreases the nodes membrane resistance and decreases the time constant
• basically shortens the nerve

Question 19

What kind of nerve is likely to be the most heavily myelinated?

Answer 19

Motor

Question 20

MS is a demyelination disease that attacks which nervous system?

Answer 20

The central nervous system!!!!

Question 21

What does a loss of myelin do to the length constant?

Answer 21

It decreases the length constant, so APs might not be propagated

Question 22

Electrical synapses are what kind of junctions?

Answer 22

Gap junctionssss

Question 23

What is an electrical synapse?

Answer 23

Direct connections between cells which allows ions to flow between

Question 24

Where would you find electrical synapses?

Answer 24

Heart, smooth muscle, bladder, places where you need coordinated contraction

Question 25

What are the advantages and disadvantages of electrical synapses?

Answer 25

They are fast, but they do not allow for any integrations from other sources.
-it can travel in both directions

Question 26

What is a chemical synapse?

Answer 26

Information is transported via chemicals across the synaptic cleft

Question 27

What are the advantages and disadvantages of chemical synapses?

Answer 27

-slow, but allow for integration

Question 28

What are the four steps of synaptic transmission?

Answer 28

• propagation of AP
• release of neurotransmitter
• binding of neurotransmitter to receptors
• effect on post-synaptic cell

Question 29

What signals the release of neurotransmitters?

Answer 29

-when AP reaches the terminal, voltage gated calcium channels open. Calcium entering causes the release of NT

Question 30

If the neurotransmitters depolarize the post synaptic cell, what kind of response is it? What ions are responsible for this?

Answer 30

-excitatory! Sodium and calcium!

Question 31

If the neurotransmitters hyperpolarize the post synaptic cell, what kind of response is that? What things do this?

Answer 31

Inhibitory! Open potassium channel. Close chloride channel

Question 32

Describe the neuromuscular junction

Answer 32

• AP opens voltage gated calcium channel
• calcium causes release of acetylcholine
• acetylcholine binds to post-synaptic cell
• the nicotine can receptors are essentially sodium channels which depolarize the cell and cause muscle constriction

Question 33

What enzyme breaks down acetylcholine? And what does it break it down into?

Answer 33

Acetylcholine esterase

-breaks it down into choline and acetate

Question 34

What does botulinum toxin do?

Answer 34

Blocks the release of acetylcholine

Question 35

What does curare do?

Answer 35

• arrow poisons

- blocks acetylcholine receptors

Question 36

What does Neostigmine do?

Answer 36

Acetylcholine esterase inhibitor

-increases contractions

Question 37

What does hemicholinium so?

Answer 37

Blocks choline reabsorption

-so no acetylcholine

Question 38

What are the uses of hemicholinium?

Answer 38

• irreversible disruption of NMJ
• chemical warfare
• nerve gas
• pesticide