Lab 7 Flashcards
Generated by excitable cells, rapid reversal of polarity
Action potential
Rising phase of action potential
Depolarization
Falling phase of action potential
repolarization
Undershoot of AP
Hyperpolarization
Muscle cells of the heart, a phase of intermediate voltage precede the falling phase , extending duration of AP
Plateau phase
Action potential is an —–
All or none process
Specific information transmitted by the neurons encoded in the
Frequency of action potential and their velocity of conduction
When there is no electrical activity
Cell difference across the cell membrane
Resting potential
In resting potential is it negative inside or outside?
Negative inside
Potential difference or the transmembrane potential in neurons at rest
-70mv
These contributes to electrical activity of various cell bodies
Electrochemical pump, voltage gated channels Na, K leak channels , differential distribution of permeable and non permeable ions
AP, of a nerve can be visualized on a computer screen through
Chart or scope software
Which leg is dissected in frogs
Sciatic nerve
Where does the nerve placed?
Nerve chamber
Is a sciatic nerve compound or not
Compound nerve
Thick myelinated fibers have ____ thresholds and conduct impulse ____
Lower , faster
Unmyelinated or smaller diameter fibers which need strong stimulus
High threshold and slow conduction
2 peaks
Compound action potential
How does resolution increase?
Increasing the distance between the stimulating and recording electrodes and using sub maximal stimuli
What does the increasing of distance significant for
Nerves has more time to pull away and separate from the action potential of slower conducting nerves
Strength increase =
Current begins to excite larger areas of the axon
Result of using sub maximal stimuli
AP occurs more quickly and the latency of stimulation decreases
Voltage at which neuron is sufficiently stimulated (depolarizer) to fire action potential
Threshold
At some stimulus voltage, all neurons reach threshold and fire all action potentials
Further increase will NOT recruit more axons to fire
Maximum response
Strength of stimulus is____ as the duration of stimulus
Reverse proportional
The minimal voltage over the longest duration of current flow milliseconds
Rheobase
Significance of rheobase
Progressive increase in pulse duration is no longer associated with a progressive decrease in voltage
The duration needed to produce a response at twice the rheobase strength
Chronoaxie
Indicative of excitability of differ t nerves dependent of Na channels
Chronoaxie
Significance of chronoaxie
If 2 nerves with the be same rheobase, chronoaxie the stimulus duration corresponding to twice the rheobase can give an indication of their relative excitabilities
Equation of conduction velocity
cv = d/t (cm/s)
Deflection caused by application of the voltage to the nerve
Stimulus artifact
Often studied by measuring difference between the sites of 2 electrodes
Biolectrical phenomena
Dropped on the nerve and increases the speed of conduction of AP
Warm ringers solution
Decrease conduction velocity
Cold fingers solution
Increasing the K+ ion concentration outside the axon will
Increase the rate at eh in potential will be generated or propagated
Reason of KCl increase AP
Higher k+ concentration outside will prevent k efflux making inside more positive and closer to depolarization in shorter time
Blocks voltage gated Na+ channels will inhibit propagation of AP
Lidocaine
