Question

1. Which of the following statements correctly characterizes synapses?

1. Synaptic vesicles constitute important features for transmission in both chemical and electrical synapses
2. A postsynaptic neuron typically receives input from different presynaptic axons that are either excitatory or inhibitory, but it cannot receive inputs from both types
3. Synaptic delay is approximately the same for both chemical and electrical synapses 

4. Receptors can provide a gating function with respect to a given ion channel 

5. The mechanism of indirect gating of ions normally does not involve the activation of G proteins 


   (Please note: you should give the reason of why you made the choice.)

2. Which of the following correctly describes the N-methyl-D-aspartate (NMDA) receptor?

1. It controls a high-conductance anion channel
2. The NMDA channel is easily blocked by the presence of magnesium
3. NMDA is selective for ionotropic receptors
4. Insufficient amounts of glutamate, acting through NMDA receptors, may cause neuronal cell death
5. Current flow is blocked in the presence of glutamate, leading to hyperpolarization of the cell

(Please describe the classification of glutamate receptors. What are their characteristics?)

Answer 1

Answer :

1) Synapse is a structure that allows a neuron to pass its information to next neuron either through chemically or electrically .

a) Synaptic vesicles are involved in chemical transmission

b) A neuron can receive both excitatory and inhibitory signals

c) Electrical transmission occurs without any significant delay as compared to chemical transmission

d) Ligand gated ion channels allow ions such as Na+, K+, Ca2+ to pass through membrane in response to binding of a ligand

e) Indirect gating of ion channels involve sG protein .

HENCE OPTION d is correct.

2) NMDA receptor is an ionotropic glutamate receptor . Glutamate receptors are classified as ionotropic receptors (non selective cation channels allowing passage of ions such as Na+, K+, Ca2+) and metabotropic receptors (a second messanger is involved and are G protein coupled).

a) NMDA receptor have cation channels

b) NMDA receptor is blocked by magnesium ion

c) Ionotropic receptors include Kainate receptors, NMDA receptor, AMPA receptor

d) Excessive amount of glutamate may lead to neuronal cell death

e) Glutamate is excitatory and current flow is not blocked in presence of glutamate

HENCE OPTION b is correct

Glutamate Receptors Inotropic receptors Metabotoopis receptors Kainate Recepta NMDA receptor AMPA receptor Groupil Group 3 Group ! molul m Glu 5 m Glu2 mGlu3 Lines de cuisine mGluu mGlub m Glu7 m Glu8 fast and excitatory Slow and excitatory Slow and inhibitory