3- Synapses

Question 1

Define synapses ?

Answer 1

Area of contact between 2 neurons

Question 2

Synaptic knob site ?

Answer 2

Distal end of the axon

Question 3

Synapses classified according to site ? (3) ( most common)

Answer 3

1- axo-dendritic (80-95% ) least excitable & most common
2- axo-axonic most excitable
3- axo-somatic junction

Question 4

Types of synapses ?

Answer 4

Electrical & chemical

Question 5

Define electrical synapses ?

Answer 5

Presynaptic & postsynaptic neuron membrane come close together forming area of fusion= gap junction

Question 6

Gap junction form a —— resistance bridge that allows ———- conduction of electrical potentials ?

Answer 6

Low , rapid

Question 7

impulse in the pre-synaptic axon causes secretion of ——————- at the synapse ?

Answer 7

chemical transmitter

Question 8

chemical transmitter act on receptors in the ?

Answer 8

Postsynaptic neuron

Question 9

Process of synaptic transmission involves ? (3)

Answer 9

1- release of transmitters into synaptic cleft
2- action of transmitter on postsynaptic
3- termination

Question 10

Depolarization of synaptic knob membrane cause ————————?

Answer 10

Transient opening of voltage gated Ca++ = inflow

Question 11

Neurotransmitter released into synaptic cleft is proportional to ————- entered synaptic knob ?

Answer 11

Calcium

Question 12

Ligand channels 2 types ? Mention them

Answer 12

1- cation channels
2- anion channels

Question 13

Cation channels allow passage ——-,——,—— ?

Answer 13

Sodium , potassium, calcium

Question 14

Na+ influx is ———- than K+ efflux leading to ——————of postsynaptic membrane ?

Answer 14

Grater
Depolarization

Question 15

Na+ influx is grater than K+ efflux leading to depolarization of postsynaptic membrane
The Transmission that produces this effect is called ?

Answer 15

Excitatory transmission ( Adrenalin or acetylcholine)

Question 16

Excitatory postsynaptic potentials is ?

Answer 16

Opening of ion channels which leads to depolarization & the inside of postsynaptic become less negative

Question 17

Anion channels allow mainly ————- postsynaptic membrane?

Answer 17

Chloride

Question 18

Chloride ion reflux leads to —————of postsynaptic membrane thus ————- postsynaptic neuron ?

Answer 18

Hyper polarization, inhibit

Question 19

Neurotransmitter that open chloride ion channels is called ?

Answer 19

Inhibitory transmission

Question 20

Hype polarization is produced by ?

Answer 20

Inc rate of k+ outflow

Question 21

Second messages receptor system is ?

Answer 21

G-protein
(slide 18)

Question 22

The movement of a component freely within the postsynaptic cell leads to?

Answer 22

1- Opening of specific ion channels e.g. second messenger gated K+ channels K+ efflux & hyper-polarization of postsynaptic membrane

2- Activation of particular enzyme systems that control the metabolic pathways in the neuron as CAMP, and cGMP.

3- Regulation of gene transcription & formation of new protein.

Question 23

Summation 2 types ?

Answer 23

Spatial & temporal

Question 24

Spatial summation is ?

Answer 24

Many synaptic knobs discharged at same time = EPSP leading to action potential

Question 25

Temporal summation is ?

Answer 25

Single presynaptic knob discharge repetitively = EPSP produced by preceding stimulus

Question 26

Post-synaptic inhibition?

Answer 26

The pre-synaptic neuron secretes inhibitory chemical substance that causes hyper-polarization of post-synaptic neuron by increase chloride influx or increase potassium efflux resulting in IPSP.

Question 27

Pre-synaptic inhibition?

Answer 27

In pre-synaptic inhibition the inhibitory knobs lies directly on the termination of the excitatory pre-synaptic fiber.
- release inhibitory chemical transmitter which decreases the release of chemical transmitter by the pre-synaptic terminal.

Question 28

Presynaptic facilitation?

Answer 28

lie on terminal nerve fibrils
• neurotransmitter chemicals secreted at such terminals frequently cause facilitation
• Circuits of this type could lead to short- term memory.