Difference Between Myogenic And Neurogenic Heart Pdf

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The mechanisms of initiation and maintenance of ventricular fibrillation VF we have been hotly debated since Hoffa and Ludwig first observed and documented the bizarre chaotic action of ventricles after exposure to electrical current.

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The neural control of heartbeat in invertebrates

The heart is a muscular organ in most animals, which pumps blood through the blood vessels of the circulatory system. In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria and lower left and right ventricles. The wall of the heart is made up of three layers: epicardium , myocardium , and endocardium.

The heart pumps blood with a rhythm determined by a group of pacemaking cells in the sinoatrial node. These generate a current that causes contraction of the heart, traveling through the atrioventricular node and along the conduction system of the heart.

The heart receives blood low in oxygen from the systemic circulation , which enters the right atrium from the superior and inferior venae cavae and passes to the right ventricle. From here it is pumped into the pulmonary circulation , through the lungs where it receives oxygen and gives off carbon dioxide. Diagnosis of heart disease is often done by the taking of a medical history , listening to the heart-sounds with a stethoscope , ECG , and ultrasound. The human heart is situated in the middle mediastinum , at the level of thoracic vertebrae T5-T8.

A double-membraned sac called the pericardium surrounds the heart and attaches to the mediastinum. The upper part of the heart is located at the level of the third costal cartilage.

The largest part of the heart is usually slightly offset to the left side of the chest though occasionally it may be offset to the right and is felt to be on the left because the left heart is stronger and larger, since it pumps to all body parts. Because the heart is between the lungs , the left lung is smaller than the right lung and has a cardiac notch in its border to accommodate the heart.

The heart has four chambers, two upper atria , the receiving chambers, and two lower ventricles , the discharging chambers. The atria open into the ventricles via the atrioventricular valves, present in the atrioventricular septum. This distinction is visible also on the surface of the heart as the coronary sulcus. Similarly, the left atrium and the left ventricle together are sometimes referred to as the left heart.

The cardiac skeleton is made of dense connective tissue and this gives structure to the heart. It forms the atrioventricular septum which separates the atria from the ventricles, and the fibrous rings which serve as bases for the four heart valves. The interatrial septum separates the atria and the interventricular septum separates the ventricles. The heart has four valves, which separate its chambers.

One valve lies between each atrium and ventricle, and one valve rests at the exit of each ventricle. The valves between the atria and ventricles are called the atrioventricular valves. Between the right atrium and the right ventricle is the tricuspid valve. The tricuspid valve has three cusps, [21] which connect to chordae tendinae and three papillary muscles named the anterior, posterior, and septal muscles, after their relative positions.

It is also known as the bicuspid valve due to its having two cusps, an anterior and a posterior cusp. These cusps are also attached via chordae tendinae to two papillary muscles projecting from the ventricular wall. The papillary muscles extend from the walls of the heart to valves by cartilaginous connections called chordae tendinae.

These muscles prevent the valves from falling too far back when they close. As the heart chambers contract, so do the papillary muscles. This creates tension on the chordae tendineae, helping to hold the cusps of the atrioventricular valves in place and preventing them from being blown back into the atria. Two additional semilunar valves sit at the exit of each of the ventricles.

The pulmonary valve is located at the base of the pulmonary artery. This has three cusps which are not attached to any papillary muscles. When the ventricle relaxes blood flows back into the ventricle from the artery and this flow of blood fills the pocket-like valve, pressing against the cusps which close to seal the valve. The semilunar aortic valve is at the base of the aorta and also is not attached to papillary muscles. This too has three cusps which close with the pressure of the blood flowing back from the aorta.

The right heart consists of two chambers, the right atrium and the right ventricle, separated by a valve, the tricuspid valve.

The right atrium receives blood almost continuously from the body's two major veins, the superior and inferior venae cavae. A small amount of blood from the coronary circulation also drains into the right atrium via the coronary sinus , which is immediately above and to the middle of the opening of the inferior vena cava.

The right atrium is connected to the right ventricle by the tricuspid valve. In addition to these muscular ridges, a band of cardiac muscle, also covered by endocardium, known as the moderator band reinforces the thin walls of the right ventricle and plays a crucial role in cardiac conduction. It arises from the lower part of the interventricular septum and crosses the interior space of the right ventricle to connect with the inferior papillary muscle.

The pulmonary trunk branches into the left and right pulmonary arteries that carry the blood to each lung. The pulmonary valve lies between the right heart and the pulmonary trunk.

The left heart has two chambers: the left atrium and the left ventricle, separated by the mitral valve. The left atrium receives oxygenated blood back from the lungs via one of the four pulmonary veins.

The left atrium has an outpouching called the left atrial appendage. Like the right atrium, the left atrium is lined by pectinate muscles. The left ventricle is much thicker as compared with the right, due to the greater force needed to pump blood to the entire body.

Like the right ventricle, the left also has trabeculae carneae , but there is no moderator band. The left ventricle pumps blood to the body through the aortic valve and into the aorta. Two small openings above the aortic valve carry blood to the heart itself, the left main coronary artery and the right coronary artery. The heart wall is made up of three layers: the inner endocardium , middle myocardium and outer epicardium.

These are surrounded by a double-membraned sac called the pericardium. The innermost layer of the heart is called the endocardium. It is made up of a lining of simple squamous epithelium and covers heart chambers and valves. It is continuous with the endothelium of the veins and arteries of the heart, and is joined to the myocardium with a thin layer of connective tissue. The middle layer of the heart wall is the myocardium, which is the cardiac muscle —a layer of involuntary striated muscle tissue surrounded by a framework of collagen.

The cardiac muscle pattern is elegant and complex, as the muscle cells swirl and spiral around the chambers of the heart, with the outer muscles forming a figure 8 pattern around the atria and around the bases of the great vessels and the inner muscles, forming a figure 8 around the two ventricles and proceeding toward the apex.

This complex swirling pattern allows the heart to pump blood more effectively. There are two types of cells in cardiac muscle: muscle cells which have the ability to contract easily, and pacemaker cells of the conducting system. These contractile cells are connected by intercalated discs which allow a rapid response to impulses of action potential from the pacemaker cells. The intercalated discs allow the cells to act as a syncytium and enable the contractions that pump blood through the heart and into the major arteries.

They are generally much smaller than the contractile cells and have few myofibrils which gives them limited contractibility. Their function is similar in many respects to neurons. There are specific proteins expressed in cardiac muscle cells. The pericardium is the sac that surrounds the heart.

The tough outer surface of the pericardium is called the fibrous membrane. This is lined by a double inner membrane called the serous membrane that produces pericardial fluid to lubricate the surface of the heart.

The pericardium is present in order to lubricate its movement against other structures within the chest, to keep the heart's position stabilised within the chest, and to protect the heart from infection. Heart tissue, like all cells in the body, needs to be supplied with oxygen , nutrients and a way of removing metabolic wastes. This is achieved by the coronary circulation , which includes arteries , veins , and lymphatic vessels. Blood flow through the coronary vessels occurs in peaks and troughs relating to the heart muscle's relaxation or contraction.

Heart tissue receives blood from two arteries which arise just above the aortic valve. These are the left main coronary artery and the right coronary artery.

The left main coronary artery splits shortly after leaving the aorta into two vessels, the left anterior descending and the left circumflex artery. The left anterior descending artery supplies heart tissue and the front, outer side, and the septum of the left ventricle. It does this by branching into smaller arteries—diagonal and septal branches.

The left circumflex supplies the back and underneath of the left ventricle. The right coronary artery supplies the right atrium, right ventricle, and lower posterior sections of the left ventricle.

The right coronary artery runs in a groove at the back of the heart and the left anterior descending artery runs in a groove at the front. There is significant variation between people in the anatomy of the arteries that supply the heart [30] The arteries divide at their furtherst reaches into smaller branches that join together at the edges of each arterial distribution.

The coronary sinus is a large vein that drains into the right atrium, and receives most of the venous drainage of the heart. It receives blood from the great cardiac vein receiving the left atrium and both ventricles , the posterior cardiac vein draining the back of the left ventricle , the middle cardiac vein draining the bottom of the left and right ventricles , and small cardiac veins.

Small lymphatic networks called plexuses exist beneath each of the three layers of the heart. These networks collect into a main left and a main right trunk, which travel up the groove between the ventricles that exists on the heart's surface, receiving smaller vessels as they travel up. These vessels then travel into the atrioventricular groove, and receive a third vessel which drains the section of the left ventricle sitting on the diaphragm.

The left vessel joins with this third vessel, and travels along the pulmonary artery and left atrium, ending in the inferior tracheobronchial node. The right vessel travels along the right atrium and the part of the right ventricle sitting on the diaphragm. It usually then travels in front of the ascending aorta and then ends in a brachiocephalic node. The heart receives nerve signals from the vagus nerve and from nerves arising from the sympathetic trunk.

These nerves act to influence, but not control, the heart rate. Sympathetic nerves also influence the force of heart contraction. The vagus nerve of the parasympathetic nervous system acts to decrease the heart rate, and nerves from the sympathetic trunk act to increase the heart rate. The vagus nerve is a long, wandering nerve that emerges from the brainstem and provides parasympathetic stimulation to a large number of organs in the thorax and abdomen, including the heart.

The ventricles are more richly innervated by sympathetic fibers than parasympathetic fibers. Sympathetic stimulation causes the release of the neurotransmitter norepinephrine also known as noradrenaline at the neuromuscular junction of the cardiac nerves. This shortens the repolarization period, thus speeding the rate of depolarization and contraction, which results in an increased heart rate.

what is difference between myogenic and neurogenic heart

The neurogenic heartbeat of certain invertebrates has long been studied both as a way of understanding how automatic functions are regulated and for how neuronal networks generate the inherent rhythmic activity that controls and coordinates this vital function. This review focuses on the heartbeat of decapod crustaceans and hirudinid leeches, which remain important experimental systems for the exploration of central pattern generator networks, their properties, network and cellular mechanisms, modulation, and how animal-to-animal variation in neuronal and network properties are managed to produce functional output. Invertebrates, owing to their small numbers of central neurons all of which are uniquely identifiable, have served as important experimental systems for the exploration of neuronal networks, their properties, network and cellular mechanisms, modulation, and how animal to animal variation in neuronal and network properties are managed to produce functional output. Automatic functions like neurogenic heartbeat have been particularly attractive for study because of their ongoing nature and the robustness of fictive neuronal activity in isolated nervous system preparations. Here we focus on two examples that are being actively pursued by experimental and computational approaches. In decapod crustaceans, the heart is neurogenic and receives innervation from a cardiac ganglion containing 9 neurons, five of which Large Cells are motor neurons. Heartbeat is driven by rhythmic bursts of impulses burst period 1—5 s in these motor neuron, which produce depolarizing EPSPs on heart muscle cells.

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. A DIRECT demonstration of the myogenic or neurogenic origin of the heartbeat in a given animal requires morphological identification of the structures involved and proof of their pacemaker function by surgical or electrophysiological means.


Such hearts are known as. Neurogenic hearts. Myogenic heart and their pacemakers –. •. In some i.e. the distinction between pacemakers and other cells is.


what is difference between myogenic and neurogenic heart

Vedantu academic counsellor will be calling you shortly for your Online Counselling session. Related Questions. Differentiate between Neurogenic heart and Myogenic heart. Answer Verified. Hint: The main organ for the circulation of blood in the organism which is responsible for the transportation of oxygen to the body required for the survival.

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Occurrence of Myogenic Hearts in Arthropods

The heart is a muscular organ in most animals, which pumps blood through the blood vessels of the circulatory system. In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria and lower left and right ventricles. The wall of the heart is made up of three layers: epicardium , myocardium , and endocardium.

Either your web browser doesn't support Javascript or it is currently turned off. In the latter case, please turn on Javascript support in your web browser and reload this page. Free to read. Interaction of neurogenic and myogenic factors that control heart rate was studied. Sympathetic nerve actions and stretch of the sinoatrial node both have an accelerator effect which appears to be competitive, and additive rather than facilitatory.

The electrical activity of the heart in Hirudo medicinalis is correlated with the rhythmic discharge of segmental heart motor neurons HE cells. Excitatory junctional potentials from the HE motor neurons summate in the heart muscle cells and give rise to large plateau-like potentials with associated spikes called bursts. Individual heart muscle cells isolated by enzymatic dissociation of the heart are capable of producing a myogenic polarization rhythm. The peripheral branches of the HE motor neurons are capable of producing antidromic burst activity peripheral neurogenic rhythm independently of the heart's myogenic rhythm when central activity in the HE cells is experimentally suppressed. HE motor neurons synaptically interact with one another in the periphery: their peripheral bursts can be coordinated and orthodromic activity in an HE cell can elicit antidromic activity in other ipsilateral HE cells whose central activity is suppressed experimentally. Antidromic bursting in HE cells is not normally observed when they are expressing their normal central activity rhythm. These observations indicate that there is a peripheral nerve plexus comprising the HE cells' peripheral branches that is capable of spreading the HE cells' activity along the heart tube.


having myogenic or neurogenic pacemakers, primarily on the genic and neurogenic hearts might not be so sharp. the mammalian heart, and compare it with.


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