Cardiovascular And Respiratory Control

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Cardiovascular and Respiratory Control

Cardiovascular and Respiratory Control


The main purpose of this essay is to understand the increase in Baseline Characteristics under resting conditions and to describe the basic reasons for such changes.

1. Results from Baseline Characteristics

Change in Resting Cardiac Output

From the graph mentioned above we can see that there has been a huge change in the cardiac output from 1966 to 1996. The basic reason for such increase in the cardiac output is that in healthy individuals, cardiac output is adjusted by a rapid increase in the strength of contraction that occurs almost immediately upon an increase in activity (Wood, 2008). After this increased contractility, additional changes in cardiac output arise from adjustment of the heart rate. The major reason for this increase is the increase in the ratio of hypertension, myocardial infarction, congenital heart disease, valvular heart disease, cardiac arrhythmias, pulmonary disease, cardiomyopathy, fluid overload, drug effects, electrolyte imbalance and decreased fluid volume.

Change in Resting Heart Rate

From the data calculated from 1966 to 1996 we can see a rapid increase in the heart rate/min. The reason for such increase is exercise, heavy lifting or other activity that requires exertion, fear, pain, anxiety, stress, anger, or nervousness fever dehydration (Stenestrand, 2001). This may be caused by too little intake of fluids, loss of blood, diarrhea, vomiting, or medications such as diuretics, sometimes called "water pills.", low blood pressure, also called hypotension(Stenestrand, 2001). Hyperthyroidism, which is a level of thyroid hormone in the body that is too high. When you do exercise your muscles use up more oxygen and produce more carbon dioxide, this sends messages to the brain telling it to provide more oxygen and get rid of the carbon dioxide at a faster rate (Khong, 2008). Hence the brain relays signals to the heart to increase its capacity, which it does by beating faster and to the veins to dilate them so they can carry more deoxygenated blood away from the muscles. So everything works together rather than as separate entities (Stenestrand, 2001). Now a day these symptoms are increasing thus resulting in increase in the heart rate.

Change in resting Stroke volume

From the above graph we can see that there has been a decrease in the resting stroke volume from 1966 to 1996. Stroke volume is determined by several factors, including preload (amount of the ventricular stretch prior to the systolic beat), after load (the pressure gradient at the aortic valve) and contractility (or the intrinsic property of the hear muscle to contract) (Stenestrand, 2001).

Sympathetic tone does increase the cardiac output, but not necessarily by increasing the stroke volume; rather it does so by increasing the heart rate (remember cardiac output = stroke volume X heart rate) (Shepherd, 2005). That is why people with acute lowering of blood pressure (as in bleeding) are always tachycardia.

Low blood pressure states usually occur in the setting of low blood volume. That in turn lowers the preload (because of the lowered venous return), which is the main determinant of ...
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