You can mark you interesting snippets of text that will be available through a unique link in your browser.

Skeletal-muscle pump

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.

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. [Sheriff D. Point: The muscle pump raises muscle blood flow during locomotion. J Appl Physiol. 2005 Jul;99(1):371-2.] [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] 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. [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.] 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

External links

* Medical College of Georgia article on the [http://www.lib.mcg.edu/edu/eshuphysio/program/section3/3ch10/s3c10_6.htm Skeletal-muscle pump]


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • muscle pump — compression of veins by the contraction of skeletal muscles, forcing blood towards the heart against the flow of gravity; seen particularly in the deep veins of the lower limbs. Called also venous p …   Medical dictionary

  • Pump (disambiguation) — A pump is a mechanical device used to move fluids and slurries.Pump may also refer to: * Ion pumps (Ion transporters) in cell membranes * Pump (shoe) * Pump (album), by Aerosmith * Pump can refer to two different Caribbean drums, one each used in …   Wikipedia

  • Muscle weakness — ICD 10 M62.8 ICD 9 728.87 (728.9 before 10/01/03) DiseasesDB …   Wikipedia

  • muscle — muscleless, adj. muscly, adj. /mus euhl/, n., v., muscled, muscling, adj. n. 1. a tissue composed of cells or fibers, the contraction of which produces movement in the body. 2. an organ, composed of muscle tissue, that contracts to produce a… …   Universalium

  • Muscle relaxant — This article refers to skeletal muscle relaxants. For information on smooth muscle relaxants, see Antispasmodic. A muscle relaxant is a drug which affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate… …   Wikipedia

  • muscle — noun ADJECTIVE ▪ hard, powerful, strong ▪ taut, tense, tight ▪ relaxed ▪ smooth …   Collocations dictionary

  • Cardiac muscle — Dog Cardiac Muscl …   Wikipedia

  • Smooth muscle tissue — Smooth muscle …   Wikipedia

  • Vein — In the circulatory system, a vein is a blood vessel that carries blood back toward the heart (as opposed to artery, a blood vessel carrying blood away from the heart). The majority of veins in the body carry low oxygen blood from the tissues back …   Wikipedia

  • Ventricular hypertrophy — DiseaseDisorder infobox Name = Ventricular hypertrophy ICD10 = ICD10|I|51|7|i|30 ICD9 = ICD9|429.3 ICDO = Caption = OMIM = MedlinePlus = eMedicineSubj = eMedicineTopic = DiseasesDB = Ventricular hypertrophy is the enlargement of ventricles (lower …   Wikipedia