Week 03 Lect. 3 - Nerve Cells, Synaptic Transmission

Question 1

What are 3 major types of synapses based on location?

Answer 1

1. Axodendritic
2. Axosomatic
3. Axoaxonic

Question 2

Describe electric synapses based on their…

Mechanism?

Direction of transmission?

Delay?

Location?

Structure?

Answer 2

Mechanism: Electrical Conduction

Direction: Bidirectional

Delay: None

Location: CNS, PNS, Smooth + Cardiac Muscle

Structure: Gap Junctions

Question 3

Describe chemical synapses based on their…

Mechanism?

Direction of transmission?

Delay?

Location?

Structure?

Answer 3

Mechanism: Chemical/Neurotransmitter

Direction: Unidirectional (pre to post synaptic)

Delay: 1-5 ms

Location: CNS and PNS

Structure: Pre/post-synaptic membrane + vesicles

Question 4

What inhibitors can affect the voltage-gated Na+ channels at the axon hillock which respond to suprathreshold graded potentials?

Answer 4

Lidocaine and TTX (tetrodotoxin)

Question 5

What is the space constant in relation to neural potential transmission?

Answer 5

space constant (λ) is the distance over which charge drops ~37% (1/e)

Question 6

What is the time constant in relation to neural potential transmission?

Answer 6

Time constant (τ) is the time after which the charge drops by ~37% (1/e)

Question 7

What is the most frequent excitatory post-synaptic potential neurotransmitter?

Answer 7

Glutamate

Question 8

What are some common glutamate receptor types?

Answer 8

1. Ionotropic (ligand-gated ion channels)
   
   1. AMPA - univalent cations (Na+ influx)
   2. NMDA - univalent cations + Ca²⁺
      
      • require dolarization, have Mg²⁺ plug
      • inhibited by PCP
2. Metabotropic Receptors
   
   • ​G protein-coupled

Question 9

What is the effect of EPSPs on membrane potential?

Answer 9

slight 0.1-5 mV depolarization for milliseconds

Question 10

What is the effect of inhibitor post-synaptic potentials on membrane potential?

Answer 10

• slight hyperpolarization of the membrane by 01.-5 mV for milliseconds

AND/OR

• stabilization of the Em

Question 11

In general, what causes IPSPs?

And what is the most frequent neurotransmitter for this?

Answer 11

• opening of ligand-gated Cl^- channels or opening of K⁺ channels
• most frequently triggered by GABA

Question 12

What are some GABA receptor types?

Answer 12

1. GABA_A receptor - ligand gated Cl^- channel (benzos activate)
2. GABA_B receptor - G_i protein-coupled; open K⁺ channels

Question 13

What are spatial and temporal summation?

Answer 13

Spatial - multiple APs from multiple presynaptic neurons adding up in the postsynaptic neuron

Temporal - multiple APs from a single presynaptic neuron adding up in the postsynaptic neuron

Question 14

What are the 4 main characteristics of a neurotransmitter?

Answer 14

1. Present/synthesized in presynaptic neuron
2. Released in response to presynaptic depolarization
3. Have specific receptors on postsynaptic cell
4. Evokes response in target cell

Question 15

How are neurotransmitters taken up into synaptic vesicles?

What two transporters?

Answer 15

1. V-type Proton Pump - takes in H⁺ ions via ATP energy
2. NT-proton Exchanger - Pulls in NTs using H⁺ gradient

Question 16

What are 3 mechanisms for termination of neurotransmitter effect?

Answer 16

1. Diffusion
2. Reuptake
3. Enzymatic Breakdown

Question 17

What is the intracellular effect of activation of muscarinic receptors 1, 3 and 5?

Answer 17

Gq >>> InsP3, increased [Ca2+]

Question 18

What is the intracellular effect of activation of muscarinic receptors 2 and 4?

Answer 18

Gi/o >>> Ad. Cyclase inhibition, cAMP decrease

Question 19

What is the intracellular effect of α1 adrenergic receptors?

Answer 19

Gq >>> InsP3, [Ca2++] increase

Question 20

What is the intracellular effect of α2 adrenergic receptor activation?

Answer 20

Gi/o >>> Ad. cyclase inhibition, cAMP decrease

Question 21

What is the intracellular effect of activation of β1-3 adrenergic receptors?

Answer 21

G_s >>> Ad. Cyclase activation, cAMP increase