Term
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Definition
| there is an increase in cardiac output and a redistribution of blood flow so that a larger proportion of the cardiac output is diverted to the active muscle. |
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Term
| Circulatory changes during exercise |
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Definition
Heart: increase cardiac output
Blood flow:
-increase in active muscles
-decrease in the viscera
-initial decrease in the skin, followed by an increase as body warms up |
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Term
| Control of cardiovascular: Neural |
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Definition
| Effects are mainly sympathetic and therefore adrenergic. Cerebrocortical input activates the sympathetic nervous system (“sympathetic drive”) and inhibits the parasympathetic nervous system. These effects may be coupled with sympathetic activation arising from stimulation of stretch and tension mechanoreceptors in active muscles. Even the anticipation of physical activity causes cerebrocortical activation of the sympathetic nervous system, and inhibits parasympathetic vagus nerve discharge to the heart. The result is that the heart rate and force of contraction increase (Beta_1-adrenergic receptors) and there is increased vasoconstriction (alpha-adrenergic receptors). THis increased vasocontristriction affects mainly the skin and abdominal viscera: the effect is quite mild in the muscles, and there may even be vasodilation via Beta_2-adrenergic receptors activated by low levels of epinephrine released by the adrenal medulla. The result is that a higher proportion of the cardiac output is available to flow through the muscles. |
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Term
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Definition
| Caused by the release of vasodilator substances such as carbon dioxide and lactic acid. Serves to increase the blood flow through active muscles. Local factors are also responsible for the increase in flow through the coronary circulation. |
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Term
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Definition
| It takes several minutes before the muscle receive sufficient oxygen, glucose and fatty acids. metabolism is covered at first by building up an oxygen deficit (oxygen from myoglobin, depleteion of creatine phosphate, anaerobic glycolysis forming lactate) Once exercise has begun, the increased sympathetic drive and reduced parasympathetic inhibition of the S-A node continue, and may even augmented. |
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Term
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Definition
-rate, force of contraction, stroke colume and cardiac output However, at elevated heart rates, the stroke volume may actually decrease, the heart is beating so fast that efficient filling of the ventricles does not have a chance to occur.
Overall, however, there is a steady increase in cardiac output is achieved mainly by an increase in heart rate. The situation may be different in well-trained long distance runners, where the stroke volume during exercise can double |
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Term
| Sympathetic action on Aterioles |
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Definition
| are constricted mainly in the skin and abdominal viscera, reducing blood flow through these organs. As soon as the body starts to heat up, the blood vessels in the dilate. The reduction in blood flow through the circulation supplying the gastrointestinal tract can be as much as 70%. Vasoconstriction results from the binding of norepinephrine to alpha-adrenergic receptors in the arterioles of these organs |
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Term
| Sympathetic action: Veins |
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Definition
| are constricted, reducing the venous capacity and boosting venous return to the heart. Stroke volume is therefore increased, and cardiac output is therefore boosted by the operation of the Starling law |
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Term
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Definition
| The venous pump (constriction and relaxation of skeletal muscles around the long veins of the legs and arms, which have valves in them) also boosts the amount of blood returning to the heart. |
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Term
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Definition
| Blood flow through the brain does not change significantly |
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Term
| In exercise: coronary circulation |
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Definition
| increases markedly, in response to local vasodilation from factors associated with the increased demand for oxygen by myocardium. |
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Term
| Release of vasodilator substances (e.g. carbon dioxide, lactic acid) in active muscles.This leads to the following |
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Definition
a) Muscle arterioles and precapillary sphincters open, allowing blood to flow into all thecapillary beds. The effect is known as capillary recruitment.
b) As a rusult of a., blood flow through active muscle is increased - sometimes by as much as 15-20 times, effectively having been diverted from the skin and, more importantly, from the abdominal viscera.
c) Total peripheral resistance is reduced - the vasodilation in the active muscles is so strong that it actually reduces the peripheral resistance, even though the vessels in the skin and abdominal viscera remain constricted. In exercise that involves a large percentage of body’s musculature (running or swimming) the reduction of peripheral resistance may be quite large. The reduction of total peripheral resistance enables the heart to pump more blood more efficiently. This is because the reduction in total resistance minimizes the the rise in mean arterial pressure that could be a consequence of increased cardiac output. |
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Term
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Definition
| When the body temperature rises during active strenuous exercise, the heart-regulation center in the hypothalamus is activated, and the skin vessels dilate to increase heat loss from the skin. If this occurs, there is a further drop in the perpheral resistance |
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Term
| Oxygen extraction during exercise |
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Definition
| More oxygen is extracted from the blood perfusing active muscles. This is caused by an increase in muscle temperature and a reduction of pH, both which force hemoglobin to give up its oxygen more easily. |
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Term
| The Four Variables of the cardiovascular system |
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Definition
1) the pump (the heart)
2) Total perpheral resistance (arterioles)
3) Capacity (veins and venules)
4) Volume of circulating fluid (blood volume) |
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Term
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Definition
| is a complex syndrome characterized by inadequate blood flow to such critical organs as the heart, brain, liver, kidneys and the abdominal viscera |
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Term
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Definition
can be caused by any factor that reduces blood volume.
Hypovolemic shock includes the following cases where loss of body fluid has occurred:
-Hemorrhage (loss of blood)
-Severe burns (loss of plasma)
-Vomiting (loss of fluid and elctrolytes)
-Diarrhoea (loss of fluid and electrocytes) |
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Term
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Definition
1) Reduced firing rate of the baroreceptors in the carotid sinus and aorta rapidly activates the sympathetic nervous system - effects on the heart on the heart and blood vessels are aimed at maintaning cardiac output and arterial blood pressure.
2) Slower responses:
-conservation of body fluid by reducing urine volume (kidneys)
-moving fluid from the interstitial space into the circulation
-restoring lost body fluid by stimulating thirst |
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Term
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Definition
1) Arteriolar vasoconstriction total peripheral resistance (especially in skin and viscera) -no vasoconstriction in coronary vessels (supplies blood to brain and heart
2) Constriction of the veins and muscular venules (mainly in the skin and gastrointestinal tract) reduces the capcity of the circulation system
3) Heart rate and force of contraction increase, promoting and increase in cardiac output. Other symptoms of sympathetic system: -Blanching of the skin in pale skinned people due to vasoconstriction of the blood vessels in the skin -Cold sweat, cold and clammy skin - the sympathetic nervous system causes sweating, and the skin is cold because of the vasoconstriction of its blood vessels. Sweating causes it to cool even more. |
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Term
| Typical symptoms after activation of sympathetic nervous system: |
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Definition
-Blanching
-Cold sweat, cold and clammy skin |
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Term
| The slower responses to return Blood volume to normal |
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Definition
1) Retention of salt and water by the kidneys. The volume of urine is reduced. This is a conservation measure, and minimizes the volume of fluid that would normally lost via urine. This is a hormonal mechanism, of which the renin-angiotensine-aldosterone system is one of the most important.
2) Movement of fluid from the interstitial space into the capillaries. This is really the opposite of edema, and is caused by reduction of pressure within the capillaries.
3) Increased thirst (appetite for salt may also be increased). this restores lost fluid and electrolytes. These effects are believed to be caused by angiotensin and aldosterone. |
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Term
| Mean arterial pressure (MAP) |
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Definition
| = diastolic arterial pressure + (1/3)arterial pulse pressure =diastolic arterial pressure + (1/3)(systolic - diastolic arterial pressure) |
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Term
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Definition
| the work load of the heart (i.e. afterload is increased), particularly the myocardium of the left ventricle, which initially hypertrophies (increases in size), and increases its oxygen demand. Therefore, any pathological decrease in coronary flow will have more severe consequences in hypertensive people than in normals. If the left ventricle starts to fail, there may be pulmonary congestion and edema. |
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Term
| hypertension in atherosclerosis |
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Definition
| Hypertension also leads to vascular pressure damage and associated atherosclerosis. effects on the renal circulation include atherosclerotic lesions which can eventually lead to renal failure. |
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Term
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Definition
| also known as essential or idiopathic hypertension, arises from unknown causes and accounts from more than 90% of all cases of hypertension. |
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Term
| Reason for treating hypertension |
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Definition
| Treatment of hypertension is important in order to minimize damage to cerebral, ocular, renal and cardiac tissues |
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Term
| Treatment of essential hypertension |
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Definition
| -Lifestyle modification - reduce sodium intake in the diet and carry out a program of weight reduction. Other factors may need to be addressed on an individual basis might include alcohol intake and smoke -Pharmacological - drugs can be divided into those that affect total peripheral resistance and those include alcohol intake and smoking. |
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Term
| Pharmalogical treatment for hypertension |
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Definition
drugs can be divided into those that affect total peripheral resistance and and those have an effect on cardiac output:
-cardiac output (diuretics, beta-blockers)
-total peripheral resistance (calcium channel blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and alpha-blockers. |
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Term
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Definition
| cardiac output X total peripheral resistance |
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Term
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Definition
| in older hypertensives, the cardiac output is notmal but the peripheral resistance is up by 40% - 60%. That is, the increased blood pressure is due to a rise in the peripheral resistance, there being no change in the cardiac output part of the equation. |
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Term
| Augmented intracellular calcium |
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Definition
| One of the underlying factors in this effect may be vasoconstriction due to augmented intracellular calcium (hence the use of calcium channel blockers such as verapamil in many hypertensive therapies. |
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Term
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Definition
The two coronary arteries branch off from the aorta just beyond the aortic semilunar valves.
-The left coronary artery branches into the circumflex artery and the left anterior descending artery (sometimes called the anterior interventricular artery).
-The right coronary artery passes along the atrioventricular sulcus between the right atrium and the right ventricle. it branches into the posterior interventricular artery and the marginal artery |
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Term
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Definition
| Blood is collected from the capillary beds in the heart and drains into the cardiac veins. The veins run parallel to the arteries. Finally, the veins drain into the coronary sinus, a very large vein that empties into the right atrium |
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Term
| Collateral Circulation in the Heart |
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Definition
| Some connections (collaterals) exist between the smaller arteries in the heart. When a sudden blockage occurs in one of the larger coronary arteries, blood flow through these collaterals may be enough minimize the damage. |
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Term
| Changes in the coronary blood flow during systole and diastole are as follows |
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Definition
-Flow decreases during ventricular systole. the reason for this is that there is strong squeezing of the intra-myoardial vessels when the heart muscle contracts during systole.
-Flow increases during ventricular diastole. During diastole. During diastole, the cardiac muscle relaxes completely and no longer prevents blood flowing through the capillary beds, so that blood flows rapidly during diastole Same when skeletal muscles contract |
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Term
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Definition
| Oxygen demand is the major factor governing coronary flow. If the heart is beating faster and more forcefully during emotional stress, it will require more oxygen, and the flow of blood through the coronary vessels will increase. this is purely a local response to vasodilator substances released during metabolism of the cardiac muscle, and is another example of active hyperemia |
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Term
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Definition
occurs when the heart demands more oxygen than the coronary circulation is able to supply.
-Supply: The ability of the coronary circulation to deliver oxygen (and nutrients) can be reduced by formaiton of a blood clot, thromboembolism, atherosclerosis, a spasm of the artery, or sudden reduction in blood pressure (from hemorrhage or during a heart).
-Demand: The demand for oxygen (and nutrients) by the cardiac muscle cells can be increased by exercise or emotional stress. |
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Term
| Consequences of myocardial ischemia: Myocardial infarction |
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Definition
| When the interruption or reduction of coronary blood supply to the myocardium is so severe and long-lasting that function can no longer be sustained, the ischemic cardiac muscle cells that make up the affected myocardium become injured and then die. the condition is then called a myocardial infarction or heart attack. |
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Term
| Consequences of myocardial ischemia: Ventricular arrhythmias (dysrhythmias) |
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Definition
| Acute myocardial ischemia, aside from leading to cell injury and cell and death, can be an important cause of ventricular arrhythmias. K(+) is lost from the injured cells, causing a reduction in the resting membrane potential of normal cells. Changes in refreactioriness and conduction also occur. The problem may be worsened if the ventricle has become enlarged as a result of the heart working against a chronically elevated blood pressure, as occurs in hypertensive patients |
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Term
| Consequences of myocardial ischemia: Angia pertoris |
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Definition
| When ischemia occurs, there is the formation of pain-producing substances such as lactic acid coupled with damage to the myocardium and loss of contractility. Lactic acid stimulates the pain endings in the cardiac muscle. The pain is called angina pectoris. Angina pectoris is a type of referred pain coming from the chest, arms and other region of the body. It typically lasts from 1-10 minutes, and may occur only during exertion (when the oxygen demand of the myocardium increases), or it may develop suddenly at rest. When that happens, the cause is usually a sudden blockage caused by development of a clot associated with ruptured, unstable atherosclerotic lesion. |
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