3 things that make an axon move slowly
- axon is leaky: low membrane resistance (k+ leak channels)
- Axon is sticky: there is negative chloride on the outside of the membrane that the ions can become attracted to which slows down conduction
- axon is thin: less cross-sectional surface area making more resistance
What is myelin and how does it speed up the axon?
Myelin: lipid bilayer membrane made from glial cells
- plugs leak channels which increases resistance
- pushes Cl further from the membrane so the inside cannot be attracted to it
What are the nodes of ranvier?
unmyelinated areas of the axon with lots of voltage gated channels allowing them to open and close
What is saltatory Conduction?
when action potentials jump from node to node
What is the difference between multiple sclerosis and Guillain-Barre Syndrome?
Multiple sclerosis is when the myelin surrounding axons in the CNS becomes inflammed and attacked
Guillain-Barre Syndrome is when the myelin in the PNS is attacked by antibodies
What are voltage gated calcium channels and what happens when a neurotransmitter binds?
- ion channels that have to be activated by a neurotransmitter
- when the channels are open the neurotransmitter is released
- transmitter flows across the cleft due to diffusion
- binds to receptor and undergoes a conformational change which opens the channels allowing the IONS to flow through
What are the two ways calcium is kept low on the inside?
- calcium pump: uses energy to pump out calcium
2. Na/ Ca exchanger: lets sodium flow into the cell and that harnesses the energy to bump out calcium
What is the glutamate receptor channel and what does it do? What kind of action potential does it initiate?
- channel that when glutamate binds the channel opens to let sodium flow through
- positive sodium ions are coming into the cell causes the cell to depolarize
- K+ can leave through the cell but it has no reason to leave bc its already close to its equilibrium potential
- causes an EPSP
What is the GABA receptor channel? What kind of action potential does it initiate?
- GABA binds to the channel and it is permeable to chloride
- negative chloride ions are coming into the cell causing the cell to hyperpolarize
- causes an IPSP
Driving Force Equation
Ix = gx (Vm-Ex)
What does a positive answer from the driving force equation mean?
+ current = outward
cell is losing positive charge
cell is gaining negative charge
What does a negative answer from the driving force equation mean?
- current = inward
cell gains positive charge
cell is losing negative charge
What is the equation for spatial integrations?
Vx = Voe^-x/lambda
What is the equation for temporal integrations?
Vx = Vo e^-t/T