The document discusses several topics related to action potentials in nerve and muscle cells: - Compound action potentials recorded from nerves are the summed action potentials of many fibers in the nerve bundle. - Cardiac muscle action potentials have a prolonged plateau phase due to slow calcium channels, which causes sustained depolarization. - Tetanic contraction occurs when muscle is stimulated at a high frequency, causing individual twitches to fuse into a sustained contraction. - Tetany is involuntary muscle contraction that can be caused by conditions increasing the firing frequency of motor neurons.

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.  Summationof 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.