Topic.5.TheNeuron.powerpoint.5.2.Neuronal.Functioning Flashcards
What increases the conduction potential of AP, aka speed neurons transmit signals?
Having a larger diameter
Nerve fiber
axon and dendrite of a nerve cell
List the the four types of nerve fibers from lease to greatest conduction potential of
c-nerve fiber, A-delta nerve fiber, A-beta nerve fiber, A-alpha nerve fiber
A-alpha nerve fibers carry
information related to
muscle sense(proprioception)
A-beta nerve fibers carry
information related to
touch
A-delta nerve fibers carry
information related to
pain and
temperature
C-nerve fibers carry information
related to
pain, temperature and
itch
Another contribution besides diameter that contribute to C-nerve fiber’s extremely low speed in transmitting neurons is…
not myelinated
What two creatures have a large diameter axons? Why?
Squids and earthworms; fast conduction=fast response aka muscle contraction for escape response
using a large-diameter water hose. Fill in :
Larger diameter – lower___faster
____
lower internal resistance, faster
conduction
Cable theory is used to understand ___ by calculating the flow of ___
conduction velocity, electric currents along an axon
In the Cable theory, what two things are taken into account in order to calculate conduction velocity?
-capacitances
-resistance
Capacitance refers to___
stored electrical charge
What causes capacitance in the cable theory?
electrostatic forces that
act through the phospholipid
bilayer
What causes resistance(longitudinal or membrane resistance) in the cable theory?
resistance is due to the
cytosol’s significant resistance
to movement of electric charge
Ex: organelle
Explain what this teaches us:
2λ, it will be 37% of the size it was at 1 λ,
λ (length constant), a measure of
how far the voltage travels down the axon before it decays to 37% of its size(1/3)
if you apply a voltage of 90mV at a specific spot on the axon, at the distance of 1 λ, the voltage would be ____
At a distance of 2λ, the voltage would be about ____
~30mV;10mV.
if you have a length constant of 1 mm, that means at____ away from the cell body in an axon, ___% of
the voltage magnitude remains.
1 mm;37%
How does have a larger length constant relate conduction velocity? Why?
A larger length constant gives greater conduction velocity.
-Can reach threshold further down axon each time the AP is generated.
-AP doesn’t have to be regenerated as many times
What is the equation that shows lambda is dependent on resistance?
λ= sqrt(rm)/(rl)
rm = resistance of
membrane
rl = longitudinal
resistance/cytosol resitance
Using the lambda equation, how can I increase the amount of current that will remain inside the cytosol to travel longitudinally along the neuron
Asking about how to increase lambda, you will increase the membrane resistance(rm)
How does myelin relate to conduction velocity?
Myelin increases rm and speeds conduction velocity. Ions can’t leave the axon in areas covered by myelin, so those ions with travel to regenerate the action potential at the next nodes of Ranvier.
Chemical synapses:
Allow neurons to receive inputs from
numerous axon terminals at the same time.
neurotransmitters:
small signal molecules secreted by
the presynaptic nerve cell to relay the signal to the postsynaptic nerve cell.