NERVE Flashcards
Gilia - Astrocytes, Myelinating (CNS vs PNS)
- Glia – insulate, support, nourish neurons
o Astrocytes – brain, regulate chemical content of extracellular space
o Myelinating glia – CNS (oligodendrocytes), PNS (Schwann cells), insulate axons (myelin)
Neuron
sense enviro and cause output, soma dendrites and axons
Soma
nucleus and organelles, produce proteins
Dendrite
antennae, receive signal
Dendritic Spine
site of synaptic input into neuron, dynamic not static will change based off what it needs to do
Axon
axon hillock is where axon joins soma, initial segment is start of axon where APs are formed, middle is axon proper, size is important for speed of conduction, axon terminal or terminal bouton ends it
Axoplasmic Transplant
axons have no ribosomes, moving material down this for it to get proteins, anterograde away from soma and retrograde toward soma using microtubules, fast anterograde transport for organelles and slow anterograde transport for cytoskeleton proteins, some pathogens go retrograde transport
Nociceptor Reflex
breaking the skin translated to neural signals and these travel rapidly to spinal cord, nociceptors are located on general somatic afferent neurons which has cell body in dorsal root ganglion, in spinal cord signal is transferred to interneurons which distribute signal, signals can go to neighboring motor neurons called general somatic efferent
Resting Membrane Potiential
affects function, most have negative and give AP with positive change, Cl/Ca/Na more outside and K more inside, caused by ion pumps and permeability of ions, Na/K pump uses a lot of your energy to maintain membrane potential keeps 2K in and pushes 3Na out, K leak channels for electrochemical equilibrium to help sit at -90mV, steady leak of Na channels as well which is +58 mV, why is it -65 because it is more permeable to K then Na
Channels Open/Channels Close
- More K channels open, more K out/hyperpolarize/quick
- Some K channels close, less K out/depolarize/quick
- Some Na channels open, Na in/depolarize/fast
- Some Ca channels open, Ca in/depolarize/fast
- K goes out, Ca/Cl/Na in
Phases
- Threshold, rising phase, peak +58, falling phase, undershoot, restabilize
- Neuron has fastest AP, skeletal muscle shortens then cardiac muscle cell in timing
- Voltage gated Na channel forms pore in membrane for Na to go across, has little delay and open for short time but not opened again until depolarization reached again
- Threshold its open, briefly after threshold the inactivated gate is closed, then during overshoot (-50) the voltage gated channel closes again
- Delayed voltage gated K channel, highly selective, one gate voltage dependent, depolarization causes it to open with delay, open briefly after polarization
Membrane Conductance
opening channels increases membrane permeability, closing channels decreases membrane permeability, an individual neuron has fast Na channels and delayed K channels
Refractory Period
- AP in one direction, orthodromic is soma to terminal, antidromic is terminal to soma, does not turn back on itself because of inactivation of Na channels
- Absolute refractory period – Na channels inactivated due to depolarization and can’t be activated again until it restabilizes
- Relative refractory period – hyperpolarized until the voltage gated K channels close
Conduction
- Conduction – 10m/sec, depends on where it spreads,
- Largest diameter in somatic efferent/afferent neurons for motor/touch, smallest diameter is somatic afferent causing slow pain, large diameter takes up space and is more susceptible to be blocked
- Myelin – insulation around axon, with node of Ranvier breaks to generate AP with voltage gated Na and K there, current spreads faster
- Saltatory conduction – AP jumps from node to node
Path of Myelin
- Proprioception bigger and myelinated and fastest, touch medium and myelinated, pain and temp smaller and myelinated, pain/temp/itch is unmyelinated and small
- Path of myelin
o Inherited – leukodystrophies, dysmelination, hypomyelination, demyelination, consequences slow conduction
o Ex: Gullain-Barre – autoimmune weakness of neurons, MS – autoimmune affects oligodendrocytes in CNS
