Bio 1-L9-Calcium dependent exocytosis for signal release

resting membrane potential- where is sodium and potassium- why the differences in charge?

• sodium outside- 120 milimolar

• inside- chloride- 63.8

• potassium- more inside the outside

allows it to do work when gates open- changes polarity

3 sodium in and 2 potassium

what influences if an ion will move

1. chemical- ions will tend to flow down

2. electrical gradient- if negative inside ions will flow down

3. permeability of membrane

4. na/k atpase

what is an action potential briefly

• excitation stimulus- will allow sodium ions to flow into cell

how do ligand gates work? does this cause A.P?

• signal binds to ligand- changes confirmation and it opens

• channel opens and flow through difussion- inside becomes very POSITIVE

• inside becomes DEPOLARISED

voltage moves towards neutral- more is needed for action potential though- -55mV

what are the triggers for depolarisation and neurotransmitter release?

• Na is the ELECRICAL- as it changes the voltage- allows Ca2+ voltage channels to open

• Ca2+ is the CHEMICAL for NT. release- changes biochemistry in vesicle

what is the synaptic vesicle cycle steps?

1. active filling of vesicles

2. clustering in active zone

3. docking of these at active zone

4. priming for the calcium dependent exocytosis

5. calcium triggering fusion

6. recycling

key proteins for neurotransmitter release?

1. SNAP-25

2. syntaxin 1

3. synaptobrevin on the membrane

4. synaptotagmin- Calcium CENSOR

ALL HAVE ALPHA HELICES- pull vesicle down to cell membrane

neurotransmitter release steps

1. sodium gates open- Na

2. cause depolarisation within cell- opens voltage depend Calcium channels

3. calcium flows in

4. synaptotgamin in the active zone bind to calcium

5. causes exocytosis

models of recycles

1. kiss and run

2. Cathrin mediated endocytosis

3. ultrafast endocytosis budding