Synaptic Transmission

Question 1

What is a Chemical Synapse?

Answer 1

• Defined by the presence of synaptic vesicles filled with neurotransmitters
  -> Neurotransmitters act as chemical messengers between cells

Question 2

What happens during an chemical synapse?

Answer 2

(From picture)

Presynaptic membrane
1. Neurotransmitters are produced and stored in vesicles
2. Action potential happens
3. Depolarization causes voltage gated Calcium channels to open
4. Calcium causes vesicles to fuse to presynaptic membrane

Postsynaptic membrane
5. Neurotransmitters are released from vesicles via exocytosis (cell exiting)
6. Transmitter binds to receptors in POSTsynaptic membrane
7. Postsynaptic channels open OR close
8. Excitatory OR Inhibitory postsynaptic potential occurs depending on the change in ion concentration
9. Glial cells (astrocytes) remove excess neurotransmitters

Question 3

What are the two types of Receptors ?

Answer 3

Ionotropic (Ligand-Gated Ion Channels)
- DIRECT activation of ion channels
-> Membrane protein serves as both the receptor AND ion channel
- Inactivated once neurotransmitter has been removed from synaptic cleft
- FAST synaptic transmission

Metabotropic (G-Proteins: Guanine nucleotide binding proteins)
- INDIRECT activation of ion channels (not directly on gate structure)
-> Receptor and ion channel are SEPARATE molecules
- Require one or more metabolic steps
- SLOWER response with longer lasting effects