Bio 161 Exam 3 (Khan Academy-Neuronal Synapses)

how does a signal go from one neuron’s axon to the next neuron’s dendrite?

action potential makes the voltage just positive enough to trigger a sodium channel, which allows Na+ to flow into the cell. By the time positively charged Na+ enters the cell, a Ca++ channel is triggered. Ca++ flows into cell because of the Ca++ pumps, once another action potential occurs another Ca++ gate is triggered, allowing these Ca++ ions to bond to other proteins that are docked to vescicles and change their confirmation just enough that the proteins bring vescicles closer to membrane and pull apart the 2 membranes so that they merge, allowing neurotransmitters to be dumped into the synaptic cleft. Neurotransmitters then bind to postsynaptic neuron (dendrites), which triggers ion channels.

when an action potential makes the voltage of a cell just positive enough, what happens?

sodium channels are triggered

sodium channels

allows flow of Na+ to enter a cell

Ca++ channel

allows flow of Ca++ to enter a cell

what kind of channel is a Ca++ channel?

voltage gated channel

are Ca++ channels mostly opened or closed?

closed

what happens when a Ca++ channel opens?

Ca++ floods into cell

Ca++ pumps

subsets of ATPase

what happens if Ca++ pumps are given 1 ATP?

Ca++ bonds someplace else and pulls phosphate apart from ATP

what is able to happen when phosphate is pulled apart from ATP?

causes enough energy to change protein confirmation and will push Ca++ out

how does Ca++ exit the cell?

Ca++ bonds and pump opens so that Ca++ can only exit

does Ca++ and Na++ have a higher concentration inside or outside of the cell?

outside of cell

synapse

place where axon terminal meets with dendrites

synaptic cleft

space between axon terminal and dendrites

how long is a chemical synapse?

20nm

vescicles

membrane-bound things inside the cell (containers)

are vescicles on presynaptic or postsynaptic neurons?

presynaptic, near terminal end

what do vescicles contain?

phospholipid bilayers and molecules (neurotransmitters)

exocytosis

when voltage-gated Ca++ channels open, Ca++ floods in and bonds to proteins that are docked to share proteins and change their confirmation just enough that proteins bring vescicles closer to the membrane and also pulls apart the 2 membranes so that the membranes merge, allowing neurotransmitters to be dumped into the synaptic cleft

neurotransmitter-gated ion channels

ion channels that are triggered when neurotransmitters bond to the membrane of the postsynaptic neuron (dendrites)

snare proteins

proteins that are docked to vescicles