Information about Skeletal Muscle Pump
The skeletal-muscle pump is a collection of skeletal muscles that aid the heart in the circulation of blood. It is especially important in increasing venous return to the heart, but may also play a role in arterial blood flow.
Between muscle contractions, intramuscular pressure transiently returns to a level below the venous blood pressure and blood from the capillary system refills the veins until the next contraction. It is postulated that this change in pressure may be great enough to actually create a vacuum that draws blood from the arterial side to the venous side. It is hypothesized that this vacuum during rhythmic contraction actually increases blood flow through the muscle and may be responsible for a portion of the increase in muscle blood flow immediately at the onset of activity.[1][2] While this explanation is attractive because it would explain the readily observable tight coupling between muscle contraction and a rapid increase in muscle blood flow, recent evidence has emerged that cast doubts on this theory. Experiments have shown that a strong muscle contraction can occur without a corresponding increase in skeletal muscle blood flow.[3] Given the proposed manner of action of the muscle pump to increase arterial blood flow, it would seem impossible for a muscle contraction and skeletal muscle hyperemia to be uncoupled.
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Venous return
During physical exercise, muscles contract and expand laterally. The intramuscular pressure exerted on the veins by the surrounding muscle pushes blood through the one-way valves of the veins, returning it to the heart. This pumping action keeps blood from pooling in the lower limbs, and individuals that stand still for extended periods of time can experience reduced venous return to the heart and low blood pressure (hypotension) leading to dizziness or fainting (syncope).Arterial blood pumping
While the muscle pump clearly is important in aiding the return of blood to the heart from the lower limbs, whether the muscle pump plays a role in the control of muscle arterial blood flow is a topic of debate.Between muscle contractions, intramuscular pressure transiently returns to a level below the venous blood pressure and blood from the capillary system refills the veins until the next contraction. It is postulated that this change in pressure may be great enough to actually create a vacuum that draws blood from the arterial side to the venous side. It is hypothesized that this vacuum during rhythmic contraction actually increases blood flow through the muscle and may be responsible for a portion of the increase in muscle blood flow immediately at the onset of activity.[1][2] While this explanation is attractive because it would explain the readily observable tight coupling between muscle contraction and a rapid increase in muscle blood flow, recent evidence has emerged that cast doubts on this theory. Experiments have shown that a strong muscle contraction can occur without a corresponding increase in skeletal muscle blood flow.[3] Given the proposed manner of action of the muscle pump to increase arterial blood flow, it would seem impossible for a muscle contraction and skeletal muscle hyperemia to be uncoupled.
References
1. ^ Sheriff D. Point: The muscle pump raises muscle blood flow during locomotion. J Appl Physiol. 2005 Jul;99(1):371-2.
2. ^ Clifford PS, Hamann JJ, Valic Z, Buckwalter JB. Counterpoint: The muscle pump is not an important determinant of muscle blood flow during exercise. J Appl Physiol. 2005 Jul;99(1):372-4
3. ^ Hamann, J. J., J. B. Buckwalter, and P. S. Clifford. Vasodilation is obligatory for contraction-induced hyperemia in canine skeletal muscle. Journal of Physiology (London). 557:1013-1020, 2004.
2. ^ Clifford PS, Hamann JJ, Valic Z, Buckwalter JB. Counterpoint: The muscle pump is not an important determinant of muscle blood flow during exercise. J Appl Physiol. 2005 Jul;99(1):372-4
3. ^ Hamann, J. J., J. B. Buckwalter, and P. S. Clifford. Vasodilation is obligatory for contraction-induced hyperemia in canine skeletal muscle. Journal of Physiology (London). 557:1013-1020, 2004.
External links
- Medical College of Georgia article on the the Skeletal-muscle pump
Skeletal muscle is a type of striated muscle, usually attached to the skeleton. Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction.
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heart is a muscular organ responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in the annelids, mollusks, and arthropods.
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Blood is a specialized biological fluid consisting of red blood cells (also called RBCs or erythrocytes), white blood cells (also called leukocytes) and platelets (also called thrombocytes) suspended in a complex fluid medium known as blood plasma.
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Vanous Return:
The rate of blood flow back to the heart is the venous return. It normally limits cardiac output.Factors That effect Venous return:
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Physical exercise is manual activity that develops or maintains physical fitness and overall health. It is often practiced to strengthen muscles and the cardiovascular system, and to hone athletic skills.
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A muscle contraction (also known as a muscle twitch or simply twitch) occurs when a muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten or remain the same.
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vein is a blood vessel that carries blood toward the heart. The majority of veins in the body carry low-oxygen blood from the tissues back to the heart; the exceptions being the pulmonary and umbilical veins which both carry oxygenated blood.
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Vanous Return:
The rate of blood flow back to the heart is the venous return. It normally limits cardiac output.Factors That effect Venous return:
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MeSH D007022
In physiology and medicine, hypotension refers to an abnormally low blood pressure. This is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it.
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In physiology and medicine, hypotension refers to an abnormally low blood pressure. This is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it.
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Fainting
Classifications and external resources
ICD-10 R 55.
ICD-9 780.2
DiseasesDB 27303
eMedicine med/3385 ped/2188 emerg/876
MeSH D013575 Fainting, also called syncope
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Classifications and external resources
ICD-10 R 55.
ICD-9 780.2
DiseasesDB 27303
eMedicine med/3385 ped/2188 emerg/876
MeSH D013575 Fainting, also called syncope
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Medical College of Georgia is the smallest of four research schools in the University System of Georgia (USG). MCG currently has 5 undergraduate and graduate schools on campus: The School of Medicine, School of Dentistry, School of Nursing, School of Allied Health, and Graduate
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