Nerve/Synapse - Lecture 5

Question 1

3 main types of synapses

Answer 1

1. Axodendritic : Synapse on the dendrites
2. Axosomatic : Synapse on the soma (cell body)
3. Axoaxonic : Synapse on the presynaptic terminal

Question 2

What structure covers dendrites in a large number

Answer 2

Spines

Question 3

Within the 3 types of synapses, which one is the most common

Answer 3

Axodendritic synapse

Question 4

2 types of axodendritic synapse and their distinctions

Answer 4

1. Spine synapse - on spines + main EXCITATORY synapse in the brain
2. Shaft synpase - on dendrite body (shaft) + INHIBITORY and will equilibrate effect of spine synapse

Question 5

Something particular about axosomatic synapse

Answer 5

Often inhibitory

Question 6

How high number of spines on dendrites was visualized

Answer 6

Using antibodies specific to proteins associated to spines and using fluorescence

Question 7

Even though a neuron has one cell body, it can have ___________ of synpases on its ___________ as its axon seperates in different __________

Answer 7

synapses. presynaptic terminals. branches

Question 8

Characteristic of AP in neuron’s different branches

Answer 8

Has the same size and pattern/frequency everywhere in a neuron cause it comes from the same cell body

Question 9

Multiple presynaptic terminals can send a message to the ____________

Answer 9

same postsynaptic spine

Question 10

2 structures we can recognize in a presynaptic terminal

Answer 10

Presynaptic vesicles and the active zone

Question 11

What are presynaptic vesicles

Answer 11

spheres of phospholipids containing neurotransmitters

Question 12

1 structure we can recognize in postsynaptic spine and what is found there

Answer 12

Postsynaptic density. Full of specialized proteins involved in synapse

Question 13

What is special about active zone

Answer 13

Vesicles are docked there by a complex of proteins

Question 14

What seperates presynaptic terminal and postsynaptic spine and Structure/Function link

Answer 14

Extremely narrow extracellular space called the synaptic cleft. Extremely narrow to facilitate rapid diffusion of neurotransmitters and maximize synapse speed

Question 15

2 groups of presynaptic vesicles

Answer 15

Those that are in the active zone and those that are a back up

Question 16

Concentration of calcium ions inside vs outside neuron

Answer 16

Inside : Very very few

Outside : 0.5 mM (mmol/L)

Question 17

What starts synapse

Answer 17

Arrival of AP at the presynaptic terminal (+) activates voltage-gated calcium channels and calcium enters presynaptic terminal

Question 18

What happens after calcium enters presynaptic terminal

Answer 18

Cascade of biochemical processes triggers release of neurotransmitters by fusion of vesicles to the membrane

Question 19

What is found on the postsynaptic spine (on postsynaptic densities more precisely)

Answer 19

Ligand-gated ion channels. When bound by neurotransmitters, will make membrane permeable to their specific ions.

Question 20

What is particular about the calcium-dependent fusion of synaptic vesicles in active zone

Answer 20

Voltage-gated calcium channels are bound to the complex of proteins which binds the vesicles

Question 21

What happens to vesicle after it fuses to release the neurotransmitters

Answer 21

Joins back into a circle in the cytoplasm and will be refilled with neurotransmitters

Question 22

What is the advantage of the voltage-gated ion channels being part of the protein/vesicle complex

Answer 22

When Ca 2+ enters the cell, finds the proteins rapidly and process is fast

Question 23

What Botox, Tetanus toxins and Black widow spider venom do (how they act)

Answer 23

They chew up (decompose/cut) proteins in the complex in the active zone so synapse doesn’t work anymore

Question 24

Effect of botox

Answer 24

Less vesicles fusion. In face, muscles, will reduce synapses that control muscle movement and this will relax the face muscles.

Question 25

Effect of black widow spider venom

Answer 25

Uncontrollable fusion of vesicles (opposite of botox)

Question 26

2 types of postsynaptic responses to neurotransmitters

Answer 26

EPSP (excitatory postsynaptic potential) : depolarizes membrane or IPSP (inhibitory postsynaptic potential) : hyperpolarizes membrane

Question 27

Main excitatory neurotransmitter in the brain and what type of molecule it is

Answer 27

glutamate : amino acid

Question 28

What is an ionotropic receptor

Answer 28

Ion channels that open in response to binding of small molecules to receptor sites on their external surface

Question 29

2 types of ionotropic glutamate receptors and which type is responsible for EPSPs

Answer 29

AMPA receptors (responsible for EPSP) and NMDA receptors

Question 30

Characteristic of AMPA receptors’ EPSP

Answer 30

fast

Question 31

AMPA receptors are different than ______ and ______ channels

Answer 31

leak ion channels and voltage-gated ion channels

Question 32

EPSP magnitude in typical brain synapse and duration

Answer 32

depolarization of approx. 2 mV and lasts 20 msec

Question 33

How many EPSPs required to depolarize initial segment of the axon to the threshold and 2 ways they can be obtained

Answer 33

50-100 near-simultaneous EPSPs. Can come from multiple synapses acting in synchrony and/or from individual synapse activated at a high frequency.