What Is Contraction of Heart Muscle Called

Myosin and Actin Animation: This animation shows myosin filaments (red) sliding along actin filaments (pink) to contract a muscle cell. Like cardiac activity, the brain`s electrical processes can be recorded from the outside. In this case, however, one does not record from a “single unit”. On the contrary, the electroencephalogram (EEG) is the ultimate in the recording of raw activity. Electrodes on the scalp, usually a network of a dozen or more, record the average activity of millions of neurons from large parts of the brain. Nevertheless, a functional separation of brain functions can be achieved by careful selection of electrode positions. The waveforms now recorded do not reflect the peak frequencies of some brain cells, but the degree (and time scale) of synchronization of large populations of brain cells. If all brain cells were to shoot without correlation, the result would again be a form of previously processed shot noise and thus show an almost “white” spectrum (the bandwidth is mainly limited by the spectral content of the peaks). This is not the case with EEG, where a single frequency (or narrow frequency band) is often the most important.

Already in the first EEG recordings that Berger made in the 1920s, some distinctive frequencies can be seen (see Fig. 4-31). These rhythms were called Greek letters, some of which are still used today: the alpha rhythm, about 10 Hz, during rest when one is awake; beta rhythm (broadband, irregular) in the performance of mental tasks; Delta waves (about 4 Hz) in deep sleep. Overall, EEG signals extend over a frequency band of about 1 to 50 Hz. Myoglobin: The heme component of myoglobin, represented in orange, binds oxygen. Myoglobin provides backup oxygen storage for muscle cells. The actual mechanical contraction reaction in the heart muscle takes place via the sliding filament contraction model. In the sliding filament model, myosin filaments slide along the actin filaments to shorten or lengthen muscle fibers for contraction and relaxation.

The path of contraction can be described in five steps: Heart muscle cells are the contracting cells that allow the heart to pump. Each cardiomyocyte must contract in coordination with its neighboring cells – known as functional syncytium – to effectively pump blood from the heart, and if that coordination breaks down, then – despite the contraction of individual cells – the heart cannot pump at all, as can be the case with abnormal heart rhythms like ventricular fibrillation. [7] Cardiac contraction impedes coronary flow during the systolic phase, so that under basal rest conditions, arterial influx occurs primarily during the diastolic phase of the cardiac cycle. Measurements of coronary artery epicardial inflow under resting conditions in pigs (Sanders et al., 1978; Bender et al., 2010) and dogs (Khouri et al., 1965) show that only 15% to 20% of left ventricular discharge occurs during systole (Fig. 22.3). However, the high heart rates generated by the movement lead to a gradual penetration of the systole in the diastolic interval, while the absolute blood flows increase during systole. As a result, up to 40% to 50% of total coronary inflow to systole can occur during strenuous physical activity (Khouri et al., 1965; Sanders et al., 1978). The increase in the CBF fraction during the systolic phase has an impact on the transmural distribution of myocardial blood flow, since the compressive effects of myocardial contraction on intramural coronary microvessels are not uniformly exerted on the wall of the left ventricle (Fig.

22.5). Thus, the myocardial compressive force increases from intrathoracic pressure to the epicardial surface at the same pressure or intraventricular to the endocardial surface (Brandi and McGregor, 1969; Archie, 1978). The interaction of this tissue pressure gradient with intravascular stretch pressure produces a series of vascular cascades through the wall of the left ventricle, which particularly impede subendocidary blood flow during systole (Downey and Kirk, 1975; Hess and Bache, 1976; Duncker et al., 1998a; Kajiya et al., 2000). Because the contracting myocardium compresses the intramural vessels during each systole, blood from the coronary microvessels in the innermost myocardial layers is pumped retrograde into more superficial subecardial and epicardial coronary arteries. Therefore, subendocardial vessels must be filled with diastoles, which is equivalent to emptying and charging a capacitor (Hoffman and Spaan, 1990; Kajiya et al., 2000; Westerhof et al., 2006). Therefore, the influx of epicardral arteries during systole is directed to the subecardium, while the antegrade subendopcardial blood flow is limited exclusively to diastoles. .