Muscle and Nerve Anatomy Flashcards
Transmembrane potential of skeletal muscle:
-90mV
Nernst equation:
chemical work = electrical work
Equilirium potentials
K+:
NA+:
CL+:
K+ -97mV
Na +66mV
Cl -90mV
Thus; chloride is the only ion in equillibrium if only the transmembrane concentration and the potential differences are taken into consideration.
The Na/K pump is a ____:_____ pump.
3:2
two forces pulling K from outside to inside the cell
- transmembrane potential (-90mV)
- active K+ transport(-7mV)
Na remains in equilibrium because of its impermeability due to mechanical barrier imposed by cell membrane. Small amount of Na that does not enter the cell is actively pumped out.
Membrane potential reaches critical level at _____ in human muscle cells
-65 to -75
close to resting state of Na (+66mV)
Resting Membrane:
K channels are ____
Na channels are ____
open
closed
depolarization causes ____ fold increase in Na permeability. Increases permeability to K also after about a 1msec delay
500
Membrane recovery occurs after inactivation of ______ and increased _____ permeability responsible for the rapid recovery towards resting membrane potential
Na+ channels
K+
hyperpolarization occurs secondary to _____ conductance
K+
______ is the connective tissue around individual axons within each fascicle
endoneurium
____ is the collagenous tissue binding each fascicle (of axons)
perineurium
_____ binds individual fascicles together. Outermost layer of support for the peripheral nerve, continuous with the duramater of the spinal roots. VASA NERVORUM is located here
epineurium
vasa nervorum is located here which supplies blood to that particular nerve
Vitally important when you start discussing blood supply to particular nerve such as with Wegeners.
Unmyelinated fibers share a single ______
schwann cell
also known as c-fibers (pain fibers)
Junctions between schwann cells are called _____
nodes of ranvier
Resting transmembrane potential in peripheral nerves are _____ at the somma and _____ at the axon
-70mV, -90mV
After about _____ of depolarization, the membrane reaches the critical level and an action potential develops with the same maximal response regardless of the kind or magnitude of the stimulus
10-30mV
____ is minimal current intensity below which no response can be elicited even if the current is applied for an indefinite period (at least 300ms)
rheobase
____ is the minimal duration of a current required to excite the cell at twice the rheobase strength
chronaxie
what are the two forces pulling K from outside to inside the cell?
- transmembrane potential (-90mV)
- Active K transport (-7mV)
Nerve conduction studies evaluate which nerves?
Large 1-A myelinated alpha fibers
Large 1-A alpha fibers:
diameter:
velocity:
diameter: 10-20nanometers
velocity: 50-120m/s
NCS cannot localize _____
pain. pain is carried by unmyelinated C fibers which can’t be picked up on NCS.
Loss of sensation to touch/pin-prick yes. Pain, no.
What is saltatory conduction?
action potential depolarizes from node of ranvier to node of ranvier in myelinated fibers as Na travels along the axon
The rate of propagation is proportional to ____
diameter of the nerve. So the larger the diameter, the faster the conduction velocity.
This is clinically important bc when you do things distally, the nerve is smaller in diameter, therefore studies done distally will have a different velocity than proximal studies.
In an unmyelinated fiver, the conduction velocity varies proportional to ____
the square root of the diameter.
