Physiological Basis of Regional Flashcards
Myelination of axon in the PNS is by
Schwann Cells
Wrapping concentric rings of its plasma membrane Called _____Around the axon
Myelin Sheath
Cytoplasm and the nucleus squeezed outside of the myeline sheath is called
Neurilemma
What is the space between adjacent myelin sheath called?
Node of Ranvier
Myelination of axon in the CNS is by
Oligodendrocytes
Axons in the CNS are myelinated by extension from the oligodendrocytes therefore
Neurelimma is absent
How does myelination help impulse
Impulse move faster by jumping from node to node
Interruptions in the axon are called
Nodes of Ranvier
Allows axolemma to be exposed to the extracellular matrix
Nodes of Ranvier
How does the nerve impulse travel along unmyelinated axons
As a uniform wave of depolarization due to conformational changes in ion channels
In myelinated axons, these ion channels like booster stations for
Propagation of passively conducted electrical current
Describe peripheral nerve
mixed nerve type with both efferent and afferent , myelinated and unmyelinated fibers.
Which layer surrounds each individual axon
Endoneurium
Contain the nerve fibers in fascicle
Perineum
Which membrane is the semipermeable membrane that acts as a major barrier to diffusion of local anesthetics
Perineum
The sheath covering the entire nerve that contains nutrient blood vessels
Epineurium
Classification of A fibers (DGBA)
Delta
Gamma
Beta
Alpha
What are the A fibers responsible for
Motor, tactile, proprioception , muscle tone touch
Responsible for pain and temperature
Small A Delta fibers
Which fibers are the autonomic preganglionic fibers
B fibers
Which fibers are the post ganglionic autonomic pain and temp
C fibers
The only unmyelinated fibers
C fibers
A fibers Alpha and Beta responsible for
Motor and proprioception
Describe the cell membrane
Phospholipid bilayer
Semipermeable
Integral proteins and transmembrane
Electrical capacitance
Sodium Channels
Protein channel
Change configuration in response to membrane potenitial
Sodium channels potential
Depolarizing potential-> decrease electrical tension OPEN
Hyperpolarizing potentials –> Increase tension and CLOSE THE CHANNEL, Rapid activation
Potassium channels
slowly activate when membrane depolarizes
RELAEASE K out of the cell
Accounts for the resting membrane potential
Potassium channels
K passively exits the cell and set the potential
NERST potential
What changes the EP across the cell membrane
Depolarization which inducing conformational changes in adjacent ion channels opening voltage gated channels
What allow the establishment of the RMP
Leaking K channels.
Phases of the AP
Resting Depolarization Repolarization Hyperpolarization Refractory interval
Resting phase
Subthreshold depolarization
Only few Na open
Hyperpolarization
K channels are wide open
Action Potential propagation
Passive spread
Active spread-in axon
Myelinated : node to node
Non-myelinated: continuous wave
Once an action potential is initiated in one region
the depolarization wave will spread out sequentially to the rest of the neuron
