Synapse/ Action Potential

Question 1

3 Types of Synapses

Answer 1

Axosomatic: axon with cell body

Axodendritic: Axon with dendritic spine

Axo-axonic: Axon-Axon (often inhibitory)

Question 2

10 Steps in Neurotransmission

Answer 2

1. Neurotransmitter is placed in vesicle
2. Action Potential electrical pulse occurs
3. Depolarization
4. Voltage gated Calcium channels open
5. Calcium ions cause synaptic vesicles to fuse with PRESYNAPTIC
6. Neurotransmitter released via exocytosis into synaptic cleft
7. Transmitter binds to receptor on post synaptic cleft
8. Postsynaptic channels open or close
9. Postsynaptic current causes excitatory or inhibitory post synaptic potential–>exciting post synaptic cell
10. Clathrin retrieves vesicular membrane from plasmamembrane via endocytosis

Question 3

SNARE Proteins

Answer 3

Synaptobrevin, Snap-25, and syntaxin form SYNAPTOGAMIN which sense Calcium levels.

Often Target of Toxins of Bacteria

Question 4

Connexin, Connexon, and Gap Junction Relationship?

Answer 4

6 connexIN = 1 connexON. 2 connexON = 1 Gap Junction. This allows instant Electrical synapse

Question 5

Why aren’t Electrical synapses always used if they’re faster?

Answer 5

Electricity will diffuse/weaken.

Chemical synapses are re-upped between cells.

Question 6

Myasthenia Gravis

Answer 6

Autoantibodies against postsynaptic acetylcholine receptor

Question 7

Lambert-Eaton Syndrome

Answer 7

Autoantibodies against calcium gated channels. Blocks neurotransmission.

Question 8

Ways to make psychoactive drugs:

Answer 8

1. increase/Inhibit synthesis
2. Interfere with storage
3. Stimulate Release
4. Inhibit receptor
5. Inhibit reuptake
6. Inhibit breakdown

Question 9

Sodium Potassium Pump

Answer 9

Pumps out 4 Na+ and brings in 3 K+ / hydrolysis of ATP

–>creates negative potential cuz of separation of charges on membranes

Question 10

Sodium Channel in Neurons

Answer 10

• Always open
• Chem and electrical force push Na INSIDE because of high Na concentration OUTSIDE
• ->different direction of Na than pump, but there aren’t as many channels.
• Fluctuates until Resting Membrane Potential

Question 11

VOLTAGE-GATED Na and K Channels

Answer 11

When cell reaches threshold membrane potential Na channels open.

Na+ can now rush into the cell. This influx creates a positive intracellular charge. Thus, causing cell to reach it’s peak action potential.

K+ channels also sense threshold potential and open. However, these efflux out of the cell. Decreasing the cell’s positive charge and lowering the action potential.

Question 12

Why the hyper polarization during Action Potential?

Answer 12

Na channels close during refractory period. However, K channels are still open (K is leaving cell) which causes an excessive negative charge.

Question 13

How does the action potential only move in one direction?

Answer 13

The AP begins at the Axon Hillock. The voltage then moves to the next adjacent axon in the same direction because cells that already encountered the AP are hyperpolarized because K Channels remain open.

Question 14

EPSP and IPSP

Answer 14

Excitatory Post Synaptic Potential: Promotes Cell to reach Threshold

Inhibitory Post Synaptic Potential: Opens K or Cl channels to create stronger hyperpolarization, preventing cell from reaching Threshold

Question 15

Nodes of Ranvier

Answer 15

junction between two adjacent myelin segments. Na and K channels are concentrated here

Question 16

Saltatory Conductance

Answer 16

Action potential “jumps” from Node of Ranvier to Node of Ranvier

Question 17

Why is demyelination pathogenic?

Answer 17

Myelin acts as an insulator for voltage. If lost, AP may not be regained/voltage may dispurse