Heart heartbeat

The cardiotonics affect the transmission of electrical impulses along the pathway of the conduction system of tiie heart. The conduction system of die heart is a group of specialized nerve fibers consisting of die SA node, die AV node, the bundle of His, and die branches of Purkinje (Fig. 39-2). Each heartbeat (or contraction of tiie ventricles) is tiie result of an electrical impulse tiiat normally starts in tiie SA node, is tiien received by die AV node, and travels down die bundle of His and through tiie Purkinje fibers (see Fig. 39-2). The heartbeat can be felt as a pulse at the wrist and otiier areas of die body where an artery is close to the surface or lies near a bone When the electrical impulse reaches the... 

Symptoms of intoxication in humans caused by accidental ingestion of Kou-Wen plants have been described as follows. The effect on the digestive system starts with loss of appetite and turn of the stomach, and continues to severe abdominal pain and intestinal bleeding. The effect on the respiratory system presents as breathing difficulties which finally lead to death by respiratory failure. The effect on muscle innervation usually results in generalized muscular weakness and paralysis of the limbs. The effect on the circulatory system starts with heartbeat disorders and a drop in blood pressure, but heart failure is not a common cause of death. In addition to dilation of pupils, a drop in body temperature and proliferation of white blood cells have also been obseryed (70). 

The mechanism of these effects involves enhanced depolarization of these cells due to decreased potassium permeability and increased sodium and calcium permeability. With fewer K+ ions leaving the cell and with more Na+ and Ca++ ions entering the cell, the inside of the cell becomes less negative and approaches threshold more rapidly. In this way, action potentials are generated faster and travel through the conduction pathway more quickly so that the heart can generate more heartbeats per minute (see Figure 14.1). 

Two important concepts to keep in mind throughout this discussion are that (1) the heart can only pump what it gets and (2) a healthy heart pumps all of the blood returned to it. The SA node may generate a heartbeat and cause the ventricles to contract however, these chambers must be properly filled with blood in order for this activity to be effective. On the other hand, the volume of blood that returns to the heart per minute may vary considerably. The heart has an intrinsic ability to alter its strength of contraction in order to accommodate these changes in volume. 

In individuals who took thyroid hormones, 80% of the weight lost was lean body mass (muscle and bone) rather than excess fat. People taking these extracts experienced muscle weakness and bone breakdown, which led to a condition called osteoporosis, in which bones are weakened and the risk of bone fractures or breaks is increased. Thyroid hormone extracts also made the heart work harder by increasing metabolism, which led to problems such as increased heart rate, palpitations, and irregular heartbeat. These problems were potentially life threatening When the heart beats abnormally (or not at all), it is unable to pump blood and oxygen to the brain and body. Individuals die suddenly from this condition because the brain can only function for a few minutes without oxygen and nutrients. 

The side effects of amphetamine are related to its stimulant effects, especially at high doses and with long-term use. Side effects include irritability, insomnia, confusion, anxiety, paranoia, hallucinations, seizures, and aggressiveness. Amphetamines cause irreversible destruction of blood vessels in the brain, which can cause stroke—even in young people. These drugs also cause the potentially lethal side effects of increased heart rate, irregular heartbeat, and increased blood pressure. 

Abuse of diuretics can lead to problems similar to those resulting from laxative abuse. These include imbalances of certain minerals in the body. Of particular concern is potassium, which is needed at certain concentrations for the heart to pump correctly. Not having enough potassium in the body can lead to an irregular heartbeat, which can result in death. Kidney damage and dehydration are other health risks associated with diuretic abuse. 

Hyperkalemia is frequently asymptomatic. Patients might complain of heart palpitations or skipped heartbeats. 

Heartbeat, 5 79-80 Heart block, 5 86, 108 Heart disease, 2 811 Hearths... 

The pacemaker device is surgically placed in a pocket of tissue near the patient s collarbone. One or more wires, called leads, are connected to the pacemaker and threaded down through a major vein to the patient s heart. By sending electrical impulses along the leads to the heart, the pacemaker can induce a heartbeat. 

Most textbooks in the 1960s suggested that deaths from belladonnoid dmgs were likewise due to central respiratory failure, even though there were insufficient empirical data to confirm this conclusion. To the contrary, a review of lethal studies of BZ in rats indicated that cardiac, rather than respiratory, failure caused death. Unlike morphine, BZ disturbs the heartbeat not the ability to breathe. The ability of the rat (or human) beating heart to mechanically ventilate the lungs, therefore, does not apply to BZ. 

Things turn out to be a bit more complex than I have suggested thus far. Acetylcholine is also known to cause contraction of skeletal muscle and to slow the rate of heartbeat. However, muscarine does neither of these things nor are these actions of acetylcholine blocked by atropine. Another plant-derived molecule, nicotine from tobacco, proved to be an acetylchohne agonist at skeletal muscle and heart. 

Many of bariums compounds are toxic, especially barium chloride, which affects the functioning of the heart, causing ventricular fibrillation, an erratic heartbeat that can lead to death. 

Dopamine is found in every sympathetic neuron and ganglion in the CNS. As a drug, and in addition to stimulation of dopaminergic receptors, dopamine indirectly stimulates both a- and )3-adrenoreceptors. Dopamine also causes a release of endogenous norepinephrine. The mechanism of action is based on the excitatory effect on )3-adrenoreceptors (in low and moderate doses), as well as on a-adrenoreceptors (in large doses). It has a positive inotropic effect on the heart, increases blood supply, selectively widens renal and mesenteric blood vessels, does not elevate blood pressure, and slightly increases the frequency of heartbeats. 

Because they increase the force of the heartbeat, all three catecholamines may produce an excessively rapid heart rate. Palpitations produced by epinephrine and isoproterenol are accompanied by tachycardia, whereas those produced by norepinephrine usually are accompanied by bradycardia owing to reflex slowing of the heart. Headache and tremor are also common. Epinephrine is especially likely to produce anxiety, fear, and nervousness. 

Following transfer of the embryos from the culture bottle into warm media, the normal heartbeat is 60 beats per minute (bpm) on average. Variations of 5 bpm from the average are noted as reduced or increased. Irregularities in the heart beat rhythm are also noted. 

Signs of overdosage include hypotension, excessive drowsiness, decreased heart rate, or abnormal heartbeat... 

Irregular heartbeat, difficulty breathing, heart problems, feeling faint, swelling, gynecomastia, decreased libido... 

FinkM, Callol-Massot C, Chu A, etal. (2009) A new method for Detection and Quantification of Heartbeat Parameters in Drosophila, Zebrafish, and Embryonic Mouse Hearts. BioTechniques 4l6, 101-113. 

Historically and romantically, the heartbeat is recognized as the quintessential hallmark of life. Normally, the heart beats at 60-100 beats per minute (bpm), with each beat yielding a ventricular contraction that ejects blood out to the body. Each heartbeat is an electrical event that originates from a collection of electrically excitable cells within the heart called the sinoatrial node (SA), anatomically located at the upper pole of the heart. The sinoatrial node is the primary pacemaker of the heart. The electrical impulse generated in the sinoatrial node spreads rapidly downward from the atria chambers of the heart and reaches the atrioventricular node (AV), a collection of electrically excitable cells that constitutes the electrical interface between the atria and ventricles of the heart. Erom the AV node, the impulse propagates throughout the ventricles via an electrical conduction system referred to as the His-Purkinje system. The electrical transmission... 

Buxus harlandii Hance Xi Ye Huang Yang (Box tree) (leaf) Cyclovirobuxine D, buxanmine E, cycloprotobuxine C, buxpiine K.58 Improve blood circulation, enhance heart muscle, regulate heartbeat, treat hepatitis, arthritis. 

Rheumatic heart disease, pulmonary heart disease, pulmonary emphysema, anemia, nephritis, drugs that inhibit heartbeat and reduce blood pressure, poor nutrition or having a low calorie diet. 

---