Neurotransmission

Question 1

Inhibitory Post-Synaptic Potential

Answer 1

Graded potential

Hyperpolarizing postsynaptic potential=influx of negative ions or effluent of positive ions

Usually from opening of Cl- or K+ channels

Question 2

Excitatory post-synaptic potential

Answer 2

Graded potential caused by depolarizing post synaptic potential due to an influx of positive ions

Usually an opening of Na+ or Ca2+ channels.

Question 3

Speed of propagation of action potential highest in axons that have….

Answer 3

Large diameter and increased myelination

Increases conduction velocity

Question 4

Electrical synapse

Answer 4

Better fidelity of event transfer between neurons

Coordinated connection of large groups of neurons

Important for signaling in retina, glial cells, astrocytes, enteric NS

Direct physical connection allows for flow of ions between cells through gap junctions, which are made of many individual channels between cells

Transmit depolarizing and hyperpolarzing currents

Low resistance/high conductance pathway with near instantaneous transmission

Question 5

Chemical Synapse

Answer 5

Rapid signal amplified in target

Excitatory or inhibitory

Neurons integrate their response from multiple inputs

Manipulated pharmacologically

Used in CNS and PNS

Synthesis and release of NTs causes ion channel to open on post-synaptic neuron resulting in post-synaptic potential

Question 6

Molecular mechanisms of exocytosis-steps

Answer 6

1. Vesicle docks
2. SNARE complexes form to pull membranes together
3. Ca2+ enters and binds to synaptotagmin, a protein on the vesicle
4. Ca2+ bound synaptotagmin catalyzes membrane fusion by binding to SNAREs and the plasma membrane

Question 7

Molecular mechanisms of endocytosis-steps

Answer 7

1. From inside the cell, clathrin is attached to to-be vesicular membrane using adaptor proteins
2. Clathrin triskelia assemble into a coat around vesicle to curve the membrane.
3. Dynamin forms a ring to pinch vesicle from membrane
4. Coated vesicle is translocated by actin filaments
5. HSBC-70 and auxiliary uncoat clathrin and dynamin from the vesicle.

Question 8

Two families of post-synaptic receptors

Answer 8

1. Ligand gated/Ionotropic

2. G-protein-coupled/Metabotropic

Question 9

Ligand-gated ion channels

Answer 9

Ionotropic

Used by ACh, glutamate, GABA, and glycine

NT receptor is major part

Very fast

1. NT binds
2. Channel opens
3. Ions flow across membrane

Question 10

G-protein coupled receptors

Answer 10

Metabotropic

For biogenic amines (serotonin, dopamine, norepinephrine), ACh, glutamate, GABA, neuropeptides

Receptor is separate from ion channel

Functional, but not physical linkage: G-protein activation stimulates dissociation, which interacts with the ion channel

Question 11

Mechanisms to deal with excess NT

Answer 11

1. Reuptake by specific transporters in presynaptic terminal or glial cells
2. Degradation by specific enzymes (ie acetylcholinesterase)

Question 12

Definition neuropharmacology

Answer 12

Mechanism by which drugs affect the nervous system

Can affect synthesis, storage, release, reception (agonist/antagonist), or inactivation (reuptake inhibitor, degradation inhibitor)