ELM8: Transmission within neurons Flashcards
What is meant by attenuated current in the dendrites?
As we get closer to the cell body there is current loss
What reasons mean that attenuation in dendrites isn’t a big problem?
Short distances
Many inputs
Dendrites can generate action potentials
What causes non attenuated transmission with an action potential wave in axons?
Higher density of sodium channels
What is needed to achieve fast transmission in axons?
Big length constants
How can we increase the size of length constants?
Decrease the leakiness
Increase the diameter
Why is increasing the diameter of the axon not a viable solution?
The needed size of axons wouldn’t be able to fit inside the body
What is a way of increasing insulation of axons?
Myelination
What are some characteristics of the nodes of ranvier?
High density of sodium channels
Transmission along them uses saltatory conduction
What is saltatory conduction?
Wave of action potentials interspersed by segments of rapid cable conduction
Why does myelination increase transmission speed?
Density of sodium channels in the nodes of ranvier
Decreased capacitance of the membrane so cable transmission through internodes is faster
What causes multiple sclerosis?
Demyelination of CNS neurons due to attack on oligodendrocytes
What are the consequences of demyelinated neurons?
Sodium channels stay in the position at nodes of ranvier and aren’t spread out
Neuron can’t transmit signals
How can MS be diagnosed using the visual evoked potential test and other tests?
Effects visual system so can test vision
Electrodes put on scalp in check pattern
Stimulus causes electrical activity which is recorded
In MS the response is delayed due to slower conduction
How is an MRI used to diagnose MS?
Reveals presence of sclerotic plaques in brain and spinal cord
Can distinguish MS from other disorders
What is Guillain-Barre syndrome?
Autoimmune disorder where schwann cells are attacked and PNS neurons become demyelinated
