The longitudinal septum divides the heart into right and left parts.
In newborns h. S. with. – 140 per minute, in older people it is 95 per minute.
70 ml is thrown out for one reduction. blood (1 minute is a minute volume of blood equal to 5 liters). The work done by the heart can be determined by multiplying the volume of blood that pushes the heart to the pressure at which the blood is released into the arteries.
The work of the heart is accompanied by various manifestations, such as heart tones. They are formed: the first – at reduction of ventricles, the second – at closing of valves of an aorta and a pulmonary trunk during relaxation; the third and fourth tones are very weak are not always observed. When the heart muscle works, electric currents are generated. They can be recorded in the form of a curve or so-called electrocardiogram. This method of research is important for determining the proper functioning of the heart and diagnosis.
The heart muscle has the following physiological properties: excitability, conductivity, contractility, automatism. This muscle is made up of striated fibers, but unlike skeletal muscle, its fibers are connected by contacts – nexuses – and therefore the excitation from any part of the heart can spread to all muscle fibers of the myocardium. The heart muscle has the ability to perceive changes in the environment and respond to excitation.
Normally, a muscle is excited under the influence of impulses of specialized heart cells, ie without the intervention of the nervous or endocrine systems (spontaneously). This ability of the heart muscle is automatic. Russian physiologist Kulyabko revived the heart of a child who died of pneumonia, 20 hours after his death, passing saline solution through the vessels of the heart (1902), proved the possibility of maintaining the viability of an isolated heart.
The accumulation of special cells occurs periodic excitation is called cardiac centers of automation: one – in the wall of the right atrium, the second on the border between the atria and ventricles. Automation centers produce electrical impulses from the first month of human embryonic life that travel through the heart muscle to other areas, which is conduction. Due to the normal functioning of the conduction system, both atria or ventricles of the heart are simultaneously covered by excitation and therefore simultaneously shrink, expelling blood.
The automation of the heart makes it possible to maintain the vital functions of the body even when the nervous system is disturbed.
Normally, the automaticity of the heart under the influence of neuro-humoral regulation is consistent with the needs of the body.
Neuro-humoral regulation of the heart
The work of the heart changes reflexively – with the participation of the autonomic nervous system (autonomic). Two pairs of centrifugal nerves – parasympathetic and sympathetic – approach the heart. Parasympathetic (vagus nerve) steam from long inhibits the heart.
Nuclear-free plates, the smallest of all cells, colorless, oval in shape, in 1 mm3 – 250 thousand, are formed in the red bone marrow, live 5-8 days.
Function: Blood clotting. Blood clotting is an important protective reaction of the body that prevents blood loss. Platelets are easily destroyed by damage to blood vessels or contact of blood with air, with the release of a substance – thromboplastin. There is an inactive protein in the blood plasma – prothrombin, which is formed in the liver (vitamin K is involved in its synthesis), when it is exposed to Ca, which is constantly present in the blood plasma and thromboplastin, the active protein thrombin is formed. There is no thrombin in the blood of a healthy person, otherwise the blood is clotted in the vessels.
There is inactive dissolved protein fibrinogen in the blood, which is also produced by the liver. By itself, like prothrombin, it does not affect blood clotting. Thrombin catalyzes the conversion of fibrinogen to fibrin, an insoluble protein that precipitates in the form of filaments, forming a network. Blood cells are trapped between these threads and tightly close the wounds, forming a clot. Acceleration of blood clotting – thrombosis (in osteosclerosis, infectious disease, stress). At the same time appoint anticoagulants (anti-coagulanin).
Hirudin – leeches with saliva, hemparin (liver, spleen, lungs). Delayed blood clotting in radiation sickness, jaundice, hemophilia leads to the danger of blood loss. Enhance blood clotting Ca chloride, vitamin K, thrombin.
The structure and function of the human heart. Automation of the heart.
Neuro-humoral regulation of the cardiac cycle.
The heart is the central organ of the cardiovascular system, the main function of which is pumping. It is a hollow, cone-shaped muscular organ. Located in the thoracic cavity between the lungs, 2/3 in the left half of the chest. The diaphragm adjoins it from below. In persons of normal body structure, the heart occupies an oblique position (in the lean – vertically, in the smooth – horizontally).
Heart weight 250-350 g, length 14-16 cm, thickness 12-15 cm. The top of the heart is directed downwards.
Externally, the heart is surrounded by an elastic pericardial sac – the pericardium, which protects it from over-stretching when filled with blood. The pericardium secretes fluid that moisturizes the heart and reduces its friction during contraction. Heart shirt – heart.
The walls of the heart have 3 layers:
The outer connective tissue layer is the epicardium. The middle muscle layer is the myocardium. The inner connective tissue layer is the endocardium.
The walls of the left ventricle are thicker due to greater myocardial development (more load).
The longitudinal septum of the heart is divided into right and left parts. The atria are located in the upper part, and the ventricles in the lower part. Between the atria and ventricles there are openings that are closed by valves that allow blood to flow in only one direction from the atria to the ventricle.
Between the atria and ventricles there are sash valves (on the right side – tricuspid, on the left – bicuspid – mitral). In a healthy heart, all valves open and allow blood to flow in only one direction. There are crescent valves (pocket) between the ventricles and arteries.
The work of the heart consists of rhythmic contractions and relaxations. Contraction is called systole, relaxation – diastole.
There are three phases of systole:
atrial systole, ventricular systole. general diastole.
With the contraction of the atria, the blood passes into the ventricles, after filling which close the flap valves, the contraction of the ventricles begins and the blood leaves the heart. Brain contraction).
Climates of the planet: the history of development. Abstract
Climates of the Earth at an early stage of its formation. The emergence of climate zonation in the Cambrian. Climates of the Phanerozoic
A detailed study of the climate shows that it, like everything in nature, is constantly changing, the climate can not but change because the factors of its formation can not remain unchanged over time. It is characterized by fluctuations both in historical time and in the distant geological past. What was the climate of the Earth in its distant past, it is possible to judge only by indirect data.
The study of the peculiarities of rocks, fossils of animals and plants, buried and modern soils, the nature of which depends on the climate of the past shows that where the earth’s surface is now covered with perennial ice, once rained tropical forests, and where now has a hot climate, the earth’s surface was covered by glaciers. Fossil leaves and fruits of the breadfruit, which grows only in tropical countries, are found under the ice deposits of the Arctic islands.
Based on fossilized remains of plants found at the South Pole, it has been established that ferns and laurels grew in Antarctica 40-50 million years ago and are now found only in the subtropics. In the middle of the last century, scientists discovered traces of past glaciations that occurred millions of years ago in North America, South Africa, Australia and India. 30 million years ago fan-shaped and pinnate palms, myrtles and magnolias grew in Ukraine. In Siberia, cypresses and walnuts grew along the rivers.
Thus, climate change is understood as its directionally progressive improvement or deterioration, during which there is a natural change in the meteorological regime.
Climates of the Earth at an early stage of its formation
Geological data show that climate change in the Earth’s past was very profound. This is easy to understand, as these changes spanned hundreds of millions of years. During this time, the situation on Earth changed radically: the location of land and sea, spelling, distribution of ocean cheap lab report writing help currents, volcanic activity, the composition of the atmosphere and more. On the other hand, cosmic influences on the Earth could change.
Considering organic and inorganic fossil remains as signs of the climates of the past, we proceed from the position that in the past there was the same dependence of flora and fauna, weathering and soil formation, and others. from the climate that still exists today.
There is no clear idea about climates in the early stages of Earth formation, especially in the Archean era, because they appeared in a denser atmosphere, which contained a lot of water vapor, CO2, H3CH4, deprived of oxygen, and almost complete lack of oxygen.
The Precambrian strata have been studied in some places. Remains of organisms 3.8 billion years old have been found. Limestone formations of blue-green algae, overlying layers on the seabed, formed in the shallow waters of the then seas and created reefs. There are also the first reddish strata of leaf ash, ribbon-like marls of annual and seasonal stratified organic residues due to strong metamorphism of rocks, as well as as a result of weak development of organic life, moraine-like deposits (tilites) were also found.
But this is evidence that long-term and significant changes in the dependent atmosphere have resulted in a sharp increase in the role of solar radiation in all terrestrial processes. There is a heterogeneity in the whole geographical distribution of climatic conditions – a combination of heat and relatively cool, humid and arid areas. For the discovery, for example, of large and powerful strata of marine sediments and coral reefs in mid-latitudes indicates the existence of a warmer climate that existed in these latitudes in the ancient era of Earth’s development, which covers 6/7 of geological history …
The emergence of climate zonation in the Cambrian
Of the fossil evidence of the climate of this period, the most widely represented marine sediments of the Lower Cambrian, corresponding to the period of large marine transgressions, when most of the modern materials were covered with warm seas with rich fauna.