Lecture 4

Question 1

Post Synaptic Receptors

Answer 1

a transmitter agent diffuses across a synapse and bind to a specific site on a receptor protein embedded in postsynaptic membrane

Question 2

Ionotropic

Answer 2

directly opens channels

Question 3

Metabotropic

Answer 3

initiates a metabolic cascade to activate enzymes

Question 4

2 types of receptors

Answer 4

1) ionotropic
2) metabotropic

Question 5

Ionotropic Effects

Answer 5

ligand binding opens an ion channel

Question 6

Metabotropic Effects

Answer 6

Binding of the ligand to the post-synaptic metabotropic receptor activates an enzyme that is usually G-protein coupled

Question 7

4 Ligands for ionotropic receptors

Answer 7

1. Acetylcholine
   
   2. Glutamate
   3. GABA
      
      4. Glycine

Question 8

Beta- Adrenoreceptor

Answer 8

A metabolic receptor for noradrenalin (NA)

Question 9

6 Ligands for Metabotropic Receptors

Answer 9

1. ACh: muscarinic receptor
2. Peptides: substance P, Beta-endorphin, ADH
3. Catecholamines: noradrenaline, dopamine
4. Serotonin
5. Purines: adenosine, ATP
6. Gases: NO, CO

Question 10

PSPs (Postsynaptic potential)

Answer 10

are generated in in excitable membrane (are neuronal dendrites and cell bodies- does not have high density of voltage-gated Na+ channels thus, can NOT initiate an AP)

Question 11

Nearest excitable membrane is at the ___________ of the axon (trigger zone )

Answer 11

beginning

Question 12

Spread of PSPs

Answer 12

the binding of a transmitter generates PSP
- PSP must spread through passive conduction across the membrane to get to the initial segment of the axon

Question 13

EPSPs

Answer 13

excitatory postsynaptic potential

Question 14

PSP Summations

Answer 14

loss of current (AP) occurs along the membrane due to the poor cable property of biological tissues before the AP reaches its trigger zone

Question 15

2 Types of Summations

Answer 15

1. spatial summation
2. temporal summation

Question 16

Spatial summation

Answer 16

minimum of 10-30 synchronous EPSPs in dendritic tree, each generated at a different synapse

Question 17

Temporal summation

Answer 17

only a few active synapses, but each generating EPSPs at high frequency; summated potentials reach threshold over a period of time

Question 18

Spatial Summation

Answer 18

Large number of EPSPs in synchrony

Question 19

Temporal Summation EPSPs

Answer 19

last for about 30-40 ms in duration before dying out, thus, successive inputs on any given synapse generates subsequent EPSPs that add on to pre-existing EPSPs (e.g. 10 ms apart)

Question 20

Inhibitory Post-Synaptic Potential

Answer 20

IPSPs tend to be preferentially located on the cell soma, interposed ½ way between the site where EPSP is generated and the trigger zone

Question 21

IPSP (Cl- Channel)

Answer 21

• IPSP involves the opening of the Cl- channel
  
  • The equilibrium potential for Cl- is very close to the resting MP (-70 mV)
  • Therefore at rest, opening of the Cl- channel would result in little change

Question 22

After Hyperpolarization

Answer 22

Voltage-gated K+ channels at trigger zone cause after hyperpolarizations

Question 23

A Spike Train

Answer 23

the sequence of neuronal firing timings, where a spike refers to the firing of an action potential.