Skeletal-muscle pump
Encyclopedia
The skeletal-muscle pump is a collection of skeletal muscle
s 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. 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. 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.
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...
s that aid the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
in the circulation of blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
. It is especially important in increasing venous return
Venous return
Venous return is the rate of blood flow back to the heart. It normally limits cardiac output.Superimposition of the cardiac function curve and venous return curve is used in one hemodynamic model.-Physiology:...
to the heart, but may also play a role in arterial blood flow.
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. 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. 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.
External links
- Medical College of GeorgiaMedical College of GeorgiaGeorgia Health Sciences University formerly known as, and now home of the, Medical College of Georgia , is a public academic health center, with its main campus located in the Medical District of Augusta, Georgia. It is the smallest of four research universities in the University System of Georgia...
article on the Skeletal-muscle pump