The document discusses several types of action potentials recorded from nerve and muscle cells, including: - Monophasic and biphasic action potentials recorded extracellularly from nerve fibers. Biphasic potentials have two peaks that are mirror images of each other. - Compound action potentials recorded from stimulating multiple nerve fibers simultaneously. This results in a larger potential that is the algebraic sum of individual fiber potentials. - Cardiac muscle action potentials have a prolonged plateau phase mediated by calcium channels, prolonging depolarization. - Skeletal muscle contraction can be tetanized if stimulated at a high frequency, fusing individual twitches into a sustained contraction through calcium summation.

1. Refractory period

5. Adaptation.
 Slowly rising currents fail to fire the nerve because the
nerve adapts to the applied stimulus, a process called
adaptation.

8. Monophasic action potential

9. Biphasic action potential

10. Biphasic action potential
 It can be recorded by placing both the recording electrodes either
in the ECF or ICF.
 In the Y axis when there is no stimulation of the nerve fiber, there
is no potential difference between the two recording electrodes
and hence the horizontal line recorded is known as isopotential
line.
 The recording will have two peaks and one will be the mirror
image of the other.
 The isopotential duration between the mirror images will depend
on the distance between the two recording electrodes and is
directly related.
 The ionic basis of the potential recorded will be same as far
monophasic action potential.

11. spike potential
 spike potential the initial, very large change in potential of
the membrane of an excitable CELL during excitation.

12.  Action potentials recorded extracellularly differ from those
recorded intracellularly in several important
respects. The size of any one action potential will be
obviously reduced. The shape of the waveform for any
one action potential will depend on the exact geometry
of its contact with the electrode.

13. compound action potential
 Delivering a sufficiently large stimulus to the nerve will result in
an action potential that is quite a bit larger than a single
intracellular action potential but looks remarkably similar.
 This compound action potential (CAP) is the algebraic
summation of all the action potentials produced by all the fibres
that were fired by that stimulus.
 The nerve is made of thousands of axons whose size,
myelination and position with respect to the stimulating and
recording electrodes all affect the size of their contribution to the
compound action potential.

14.  Both the classic intracellular action potential and the
compound action potential are biphasic. In other
words, they have both positive and negative
deflections, but for different reasons. The negative
phase of the intracellular action potential is attributed
to the mechanism of after-hyperpolarization.

16. Compound Action potential

18. Cardiac muscles

19.  Plateau greatly prolongs the period of
depolarization.
 This type of action potential with plateau is seen
in heart muscle fibers.

20.  Opening of fast channels causes the spike portion
of the action potential.
 The slow, prolonged opening of the slow calcium-
sodium channels mainly allows calcium ions to
enter the fiber.
 This is largely responsible for the plateau portion
of the action potential.

22. Smooth muscles

24.  Sensitive to stretch
 Slow wave potential
 Spike potential

25.  Summation of Twitches and Tetanization
 Summation: If a skeletal muscle is stimulated and a
second stimulus is applied before relaxation is
complete, a second contraction, which develops a
greater tension, is fused to the first contraction. A
possible explanation may be that Ca++ remains from
the previous contraction and together with additional
Ca++ from the second stimulus constitutes more
activator Ca++ than would be available if relaxation
had been incomplete.
 Tetanus: If the stimulus is repeated at a sufficiently
high rate, the muscle will not relax between each
stimulus but rather will remain in a contracted state.

26.  A tetanic contraction (also called tetanized
state, tetanus, or physiologic tetanus, the latter to
differentiate from the disease called tetanus) is a
sustained muscle contraction evoked when the motor
nerve that innervates a skeletal muscle emits action
potentials at a very high rate.During this state, a motor
unit has been maximally stimulated by its motor
neuron and remains that way for some time. This occurs
when a muscle's motor unit is stimulated by multiple
impulses at a sufficiently high frequency. Each stimulus
causes a twitch. If stimuli are delivered slowly enough, the
tension in the muscle will relax between successive
twitches. If stimuli are delivered at high frequency, the
twitches will overlap, resulting in tetanic contraction.
Tetanic contraction can exist in a variety of states,
including isotonic and isometric forms.

27.  Tetany or tetany seizure is a medical sign consisting of
the involuntary contraction of muscles, which may be
caused by disease or other conditions that increase
the action potential frequency of muscle cells or the
nerves that innervate them. Muscle cramps which are
caused by the disease tetanus are not classified as
tetany; rather, they are due to a lack of inhibition to
the neurons that supply muscles.