The table illustrates the distribution of the systemic cardiac output to the var

Question

The table illustrates the distribution of the systemic cardiac output to the various organs at rest and during strenuous exercise.

What physiological mechanisms produce the changes in blood distribution depicted in the table? How do the physiological systems work together and how does a homeostatic imbalance in one system affects others?

Consider the competing homeostatic demands strenuous exercise places on the body. Why might exercising on an extremely hot summer day result in fainting?

Table 1. Distribution of systemic cardiac output at rest and during strenuous exercise. Flow at rest (ml/min) Brain Heart Skeletal muscle Skin Kidneys Abdominal organs Other Total 650 (13%) 215 (4%) 1030 (20%) 430 (996) 950 (20%) 1200 (24%) 525 (10%) 5000 Flow during strenuous exercise (ml/min) 750 (4%) 750 (4%) 12,500 (73%) 1900 (11%) 600 (3%) 600 (3%) 400 (296) 17,500

Explanation / Answer

Homeostasis maintain blood distribution in the verious organ. Blood flow through the tissue is depend on the metabolic needs of the tissues. During excercise blood flow through the skeletal muscles 15 times greater than the resting muscles. Excercise means increased muscular activity leads to low oxygen tension and release of vasodilator substance which cause dilation of precapillary sphincters. Blood shunted from viscera and skin through the vessel in skeletal muscle so increase in cardiac output of skeletal muscle, skin and heart. Movement of skeletal muscles during excercise compress vein in cyclic fashion and constriction of vein greatly increases the venous return to the heart. The resulting increase in the preload and increased sympathatic stimulation of heart result in elevated heart rate and stroke volume which increase the cardiac output. Due to excercise blood flow greatly increase in excercising muscles and other organ has a low blood flow which is jusy adequate to supply their metabolic needs.

Homeostasis is defined as constant steady environment despite external changes such as excercise. Excercise effect body temperature, blood oxygen level, sugar level and hydration all these system needed for survival. To maintain internal environment physiological system work together for example when body temperature increases than blood vessels of skin dilate to allow more blood flow to the surface of your body where it disperse heat result in sweating . This mechanism to cool down body temperature.

If homeostatic imbalance occur than automatic feedback system that maintain normal temperature , water level despite of external condition , disrupted. For example, absence of proper blood flow during excercise result in muscles do not get adequate blood and other nonrequired organ get more blood which leads to verious disorder and ultimately cell death.

Hot summer day means heigher temperature, insufficient intake of fluid and excessive sweating during excercise leads to the dehydration which result in low blood volume . Low blood volume means reduce supply of blood to brain which result in oxygen depletion in brain which cause fainting.

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