BMS11004 - WEEK 3 WEDNESDAY

Question 1

how can synapses enable flexible processing

Answer 1

increase complexity, and flexibility for integration (interneurons can allow multiple inputs)

Question 2

what is strcture of electrical synapse

Answer 2

gap junctions (direct pore) allowing current to directly pass between neuron without chemicals, making cytoplasms of 2 neuron continuous

Question 3

how large is gap junction diameter

Answer 3

1-2nm

Question 4

how can you tell if 2 neurons are connected by gap junctions (electrical synapse)

Answer 4

1. dye injection- small molecule so can diffuse across gap
2. if can transmit both hyperpolarisations and depolarisations then is a electrical synapse
   if delete a connexin gene then stops as gene is required when building gap junctions

Question 5

what are electrical synapses used for

Answer 5

reflex actions = fast communication and synchronising neurons, if necessary

Question 6

provide overview in chemical synaptic transmissions

Answer 6

1. package NT into vesicle, move to pre-synaptic terminal
2. AP arrive, open v/gated Ca2+ channels
3. Ca2+ influx cause vesicles fuse to membrane and release NT
4. NT diffuse across synaptic cleft, activates receptor on PSC, further signalling
5. NT removed from cleft

Question 7

name the 2 major vesicle catagory types

Answer 7

defined by what is inside
- synaptic vesicles, dense-core secretory granules

Question 8

compare structures of synaptic vesicles and dense-core secretory granules

Answer 8

SV = clear and small (40-50nm)
DCSG = dense and large (100nm)

Question 9

compare what synaptic vesicles and dense-core secretory granules carry

Answer 9

SV = small molecule transmitters (eg: glutamate)
DCSG = peptide NT eg: amino acids, opioidsm endorphins

Question 10

explain how synapic vesicle and dense-core secretory-granules are filled

Answer 10

SV = filled by presynaptic terminal transporter protein
DCSG = created and filled by ER/Golgi apparatus

Question 11

compare lifespans for synaptic vesicles and dense-core secretory granules

Answer 11

SV = recycled via endocytosis
DGSG = one+done

Question 12

how can you record how Ca2+ channels open

Answer 12

use calcium sensitive flurorescent proteins

Question 13

explain how vesicles bind to membrane, using SNARE proteins (including v-SNARE, t-SNARE, synaptotagmin and “zipper”)

Answer 13

v-SNARE = vesicle
t-SNARE = target
when Ca bind to synaptotagmin, conformational change make SNAREs ‘zipper’ together and force vesicle to fuse to membrane

Question 14

what are SNARE-proteins used for

Answer 14

targets for toxins like botulinum and tetnus
used to transport proteins around cells using their ‘zippers’

Question 15

state 2 different ways how NT can bind to postsynaptic receptor to initiate a process

Answer 15

1. ligand-gated ion channel
2. G-protein coupled receptor

Question 16

explain how NT binding to postsynaptic receptors using ligand-gated ion channels (ionotropic receptor), impacts cell

Answer 16

directly depolarises/hyperpolarises postsynaptic cell

Question 17

explain how NT binding to postsynaptic receptors using G-protein-coupled receptor (metabotropic receptors), impacts cell

Answer 17

causes biochem cascades, often involving enzymes

Question 18

what is a GPCR

Answer 18

G-protein-coupled-receptors
G proteins which are coupled to other G protein that could be responsible for multiple different effects

Question 19

name 3 methods of NT removal

Answer 19

1.diffuse away- takes time, not best way, and not temporally precise
2.actively taken up by transporters for recycling into presynaptic neuron/glia
3. destroyed in synaptic cleft by enzyme

Question 20

give properties of electrical synapses (directions, speed)

Answer 20

signal pass in both direction
passed directly and can only be attenuated (make bigger or smaller but not inverted or changed direction)
fast (<0.3ms)

Question 21

give properties of chemical synapses (directions, speed, signal transormations, modifablities)

Answer 21

signals pass in 1 direction but can be transformed to change direction, inverted, amplify
more ‘plastic’ = modifiable
slower (0.3-5ms)

Question 22

what NT do neuromuscular junctions use?

Answer 22

acetylcholine

Question 23

what are useful components of neuromuscular junctions (why may you want to use them)

Answer 23

fast and reliable, largest synapse in body, many active zones in pre-synap, junctional folds on post-syn precisely aligned to active zones = allow Ach to land exactly and definitely trigger contractions

Question 24

explain how signals in neuromuscular junctions are released in discrete amount (not in continuous amounts)

Answer 24

statistical distribution of post-synaptic potential amplitudes shows NT in “quantum packets” with 1 quantum = 1 vesicle, filled with NT
cannot release half-vesicle, but release different number of whole vesicle

Question 25

name different joinings for synapse

Answer 25

1. axosomatic = soma
2. axodendritic = dendrites
3. axoaxonic = one terminal button onto another
4. axospinous = presynaptic neurons onto post-dendritic spine
5. dendrodentric = dendrites form synapse with others
6. dendrosomatic = dendrite onto somas

Question 26

explain how botulinum toxin causes paralysis

Answer 26

targets SNARE proteins, ‘zippers’ for movement of NT
so cannot move chemicals into vesicle for synaptic transmissions