Action Potential II: Conduction Flashcards
What is a region of the nerve membrane without myelin called?
a node of Ranvier
With myelination, _____ the nerve diameter ______ the conduction velocity.
doubling; doubles
_____ are mediated by large, and therefore fast conducting, axons.
Reflexes
With myelination, doubling the ______ doubles the ______.
nerve diameter; conduction velocity
The _____ and ____ are carried principally by K+ ions.
axoplasmic; outward membrane currents
The axoplasmic and outward membrane currents are carried principally by ____.
K+ ions
What happens when anesthetic is applied to a long enough length of axon?
APs fire but cannot get past the anesthetic block bc the anesthetic blocks the Na+ channels
The action potential “jumps” from node to node; this is called ______.
salutatory conduction
______ is limited by the velocity of action potential propagation along sensory and motor axons.
Reaction time
The effective resistance between the _____ and the ______ is increased by myelin.
axoplasm; extracellular fluid
What is a node of Ranvier?
a region of the nerve membrane without myelin
_____ depends only on axon diameter.
Conduction velocity
When a node of Ranvier is depolarized to threshold, ____ in the nodal membrane ____ and the node becomes an active locus.
Na+ channels; open
An active locus in a _____ axon will depolarize a _____ length of membrane ahead of the active locus than a large diameter axon.
small diameter; shorter
The inward membrane current at the active locus is carried by _____.
Na+ ions
The _____ “jumps” from node to node; this is called salutatory conduction.
action potential
With ______, doubling the nerve diameter doubles the conduction velocity.
myelination
The effective resistance between the axoplasm and the extracellular fluid is increased by _____.
myelin
What is the safety factor of transmission?
axons have 5-10x excess # of Na+ channels
The action potential will propagate more slowly in a ____.
small axon
Conduction velocity depends only on _____.
axon diameter
______ greatly increases conduction velocity.
Myelination
Reflexes are mediated by _____, and therefore ____ conducting, axons.
large; fast
The action potential will propagate more _____ in a small axon.
slowly
Reaction time is limited by______ along sensory and motor axons.
the velocity of action potential propagation
The ______ at the active locus is carried by Na+ ions.
inward membrane current
When a ______ is depolarized to threshold, Na+ channels in the nodal membrane open and the node becomes ______.
node of Ranvier; an active locus
The ______ between the axoplasm and the extracellular fluid is increased by myelin.
effective resistance
Reaction time is limited by the velocity of action potential propagation along ______.
sensory and motor axons
The action potential “jumps” from ______; this is called salutatory conduction.
node to node
Myelination greatly increases _____.
conduction velocity
The effective resistance between the axoplasm and the extracellular fluid is _______ by myelin.
increased
Why is there a safety factor of transmission?
1) insures that action potentials will spread down all branches of the axon 2) it allows a shorter absolute refractory period 3) frequency and velocity of APs are increased
What is the purpose of myelin?
to insulate the nerve fiber
