What causes staircase phenomenon?

What causes staircase phenomenon?

The effect exhibited by skeletal and heart muscle when subjected to rapidly repeated maximal stimuli following a period of rest. In the resulting series of contractions, each is greater than the preceding one until a state of maximum contraction is reached.

Why do you observe staircase phenomenon in cardiac muscle?

The Bowditch effect or staircase phenomenon is the intrinsic property of the heart to either increase or decrease the force of contraction in response to an increment in pacing rate.

What causes the treppe effect?

The “treppe” exhibited in intact human skeletal muscle, as shown in the initial increase in the extent of the knee-jerk, is probably caused by the accumulation of small amounts of the commonly recognized fatigue products: carbon dioxide, lactic acid and manopotassium phosphate.

What causes contraction of cardiac muscle?

Contraction in cardiac muscle occurs due to the the binding of the myosin head to adenosine triphosphate ( ATP ), which then pulls the actin filaments to the center of the sarcomere, the mechanical force of contraction.

What is the refractory period in cardiac muscle?

After an action potential initiates, the cardiac cell is unable to initiate another action potential for some duration of time (which is slightly shorter than the “true” action potential duration). This period of time is referred to as the refractory period, which is 250ms in duration and helps to protect the heart.

Why cardiac muscles Cannot be Tetanized?

Cardiac muscle tissue contracts without neural stimulation, a property called automaticity. As a result, cardiac muscle tissue cannot undergo tetanus (sustained contraction). This property is important because a heart in tetany could not pump blood.

What is Fenn effect?

Fenn effect – the increased liberation of heat in a stimulated muscle when it is allowed to do mechanical work.

What is staircase phenomenon?

staircase phenomenon –> treppe. A phenomenon in cardiac muscle first observed by H.P. Bowditch; if a number of stimuli of the same intensity are sent into the muscle after a quiescent period, the first few contractions of the series show a successive increase in amplitude (strength).

What stimulates contraction in cardiac muscle?

Contraction in each cardiac muscle fiber is triggered by Ca++ ions in a similar manner as skeletal muscle, but here the Ca++ ions come from SR and through voltage-gated calcium channels in the sarcolemma. Pacemaker cells stimulate the spontaneous contraction of cardiac muscle as a functional unit, called a syncytium.

What causes absolute and relative refractory period?

Absolute refractory period occurs because of the inactivation of sodium channels. Since the sodium channels are inactivated, the neuron can’t depolarize and initiate another action potential. Relative refractory period occurs due to the slow inactivation of potassium channels.

What is meant by the term refractory period?

Definition of refractory period : the brief period immediately following the response especially of a muscle or nerve before it recovers the capacity to make a second response.

Are the staircase phenomenon and all or none law contradictory to each other in case of cardiac muscle?

It appears that the staircase phenomenon violates the principle of all or none law, but in fact it is not so, because each stimulus alters the condition for the next stimulus.

What is the staircase phenomenon?

staircase phenomenon The effect exhibited by skeletal and heart muscle when subjected to rapidly repeated maximal stimuli following a period of rest. In the resulting series of contractions, each is greater than the preceding one until a state of maximum contraction is reached.

What is the inverse staircase effect in heart failure?

This phenomenon is usually absent or even reversed (negative Bowditch effect) in heart failure and other diseases of heart, such as cardiomyopathy and coronary artery disease. This is termed as the null or inverse staircase phenomenon. The probable cause for this effect is attributed to mutations in SERCA2a.

What is a phenomenon in cardiac muscle?

A phenomenon in cardiac muscle. If a number of stimuli of the same intensity are sent into the muscle after a quiescent period, the first few contractions of the series show a successive increase in amplitude (strength). Synonym (s): staircase phenomenon.

Does the staircase effect occur in the adductor pollicis?

The staircase effect was significantly positive for the first dorsal interosseus muscle and the adductor pollicis muscle. The signal potentiation was not significantly different between the first dorsal interosseus muscle with a maximum increase at 148 (19)% using PMG, and the adductor pollicis muscle at 154 (22)% using MMG.