Physiological Effects of Electrical Currents

What are the three primary physiological responses to electrical current?

Electrochemical effects, electrothermal effects, electrophysical effects.

What happens to sodium ions (Na+) when subjected to electrical stimulation?

Sodium ions migrate to the cathode, forming sodium hydroxide.

What is produced when chloride ions (Cl-) move towards the anode?

Hydrochloric acid is produced.

What is the result of electrochemical effects at the cathode and anode?

Alkaline reaction at the cathode and acidic reaction at the anode.

What can excessive or prolonged electrical stimulation lead to?

Corrosive effects and skin damage/burns.

What is the mechanism behind electrothermal effects?

Charged particles moving through tissues produce heat due to friction and vibration.

What consequence can arise from excessive heat generation during electrical stimulation?

Skin burns can occur due to excess heat.

How do electrical currents cause electrophysical effects?

They depolarize nerve and muscle cell membranes.

What happens to membrane permeability in the presence of an electrical stimulus?

Membrane permeability to Na+ increases.

What is the function of the negative electrode (cathode) in electrical stimulation?

It is more efficient at depolarizing nerves.

What are the stimulus requirements for producing action potentials?

Sufficient amplitude and duration of electrical stimuli.

What does the strength-duration curve represent?

It shows combinations of current strength and duration required to stimulate nerves or muscles.

What is the Rheobase?

The minimal amplitude required to stimulate tissue when the pulse duration is infinite.

Define Chronaxie.

The minimal pulse duration required to stimulate tissue when the amplitude is double the Rheobase.

What is the typical Chronaxie for nerves?

Typically below 1 ms.

What does a prolonged Chronaxie indicate in denervated muscles?

It indicates denervation or other excitable tissue diseases.

What principle describes the generation of action potentials?

The All-or-Nothing Principle.

What is the significance of the All-or-Nothing Principle?

Stimuli greater than the minimal required will not produce a larger action potential.

What characteristic of denervated muscles differs from innervated muscles?

Denervated muscles have a significantly larger Chronaxie.

What is required for effective stimulation of denervated muscles?

A larger pulse duration is required.

What type of fibers are described as A-Beta fibers?

Touch and pressure fibers.

What pulse durations are required for A-Beta fibers?

Shorter pulse durations/widths.

What is the requirement for motor fibers in electrical stimulation?

They require larger pulse durations.

What type of pain relief does TENS aim for using A-Beta fibers?

Acute pain relief.

How are larger-diameter nerve fibers stimulated during electrical stimulation?

They are preferentially stimulated.

What fibers are stimulated first during electrical stimulation?

More superficial fibers closer to electrodes.

What is the effect of increasing intensity/amplitude in electrical stimulation?

It stimulates deeper and more fibers.

What types of current are commonly used in physical therapy?

Various current types, waveforms, and parameters.

What waveform does standard TENS typically use?

Symmetrical biphasic waveforms.

Are ramp-up and -down parameters typically used with TENS?

No, they are not typically used.

What is the primary mechanism for tissue heating during electrical current application?

Friction and vibration of charged particles in bodily tissues.

What are the consequences of low ion movement compared to high current intensity?

Low ion movement leads to minimal physiological effects, while high intensity can cause significant tissue response.

Which types of current can create a burning sensation at high intensities?

Direct current (DC) or monophasic currents.

What does the increase in Na+ permeability during electrical stimulation lead to?

It leads to depolarization and ion movement across the membrane.

Why is it important to consider pulse duration when applying electrical stimulation to denervated muscles?

Short pulse durations might not effectively stimulate them.

What does an increase in electrical current intensity generally produce?

It produces a stronger action potential response.

What is the risk of applying excessive electrical current beyond safe levels?

Increased risk of tissue damage and burns.

What role does skin resistance play in electrical stimulation?

Skin acts as an insulator and can limit the amount of current that penetrates the tissues.

What type of applications may utilize the principles of electrical stimulation?

Rehabilitation and pain management applications in physical therapy.