Myogenic

Myogenic

Myogenic contraction refers to a myocyte contraction that originates from a property of the myocyte itself. I.e. the contraction is initiated by the cell itself, not an outside occurrence or stimulus such as nerve innervation.

Mechanisms

Unstable Membrane Potentials

Many cells have resting membrane potentials that are unstable. This instability is usually due to ion channels in the cell membrane that spontaneously open and close (e.g. If channels in cardiac pacemaker cells). When the membrane potential reaches depolarization threshold an action potential (AP) is fired, excitation-contraction coupling initiates and the myocyte contracts.

Slow wave potentials

Slow wave potential are unstable resting membrane potentials that continuously cycle through depolarization- and repolarization phases. However, not every cycle reaches depolarization threshold and thus an action potential (AP) will not always fire. Owing to temporal summation (depolarization potentials spaced closely together in time so that they summate), however, cell membrane depolarization will periodically reach depolarization threshold and an action potential will fire, triggering contraction of the myocyte.

Pacemaker potentials

Pacemaker potentials are unstable cell membrane potentials that reach depolarization threshold with every depolarization/repolarization cycle. This results in AP's being fired according to a set rhythm. Cardiac pacemaker cells, a type of cardiac myocyte in the SA node of heart, are an example of cells with a pacemaker potential.

Stretch

This mechanism involves the opening of mechanically-gated Ca2+ channels when some myocytes are stretched. The resulting influx of Ca2+ ions lead to the initiation of excitation-contraction coupling and thus contraction of the myocyte.

See also

Membrane potential

Action potential

Excitation-contraction coupling

Myogenic mechanism (Myogenic reflex)


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • myogenic — [mī΄ō jen′ik] adj. [ MYO + GENIC] originating in or produced by a muscle …   English World dictionary

  • myogenic — myo·gen·ic .mī ə jen ik also my·og·e·nous mī äj ə nəs adj 1) originating in muscle <myogenic pain> 2) taking place or functioning in ordered rhythmic fashion because of inherent properties of cardiac muscle rather than by reason of specific …   Medical dictionary

  • myogenic — adjective Etymology: International Scientific Vocabulary Date: 1904 taking place or functioning in ordered rhythmic fashion because of the inherent properties of cardiac muscle rather than specific neural stimuli < a myogenic heartbeat > …   New Collegiate Dictionary

  • myogenic — /maɪoʊˈdʒɛnɪk/ (say muyoh jenik) adjective of or relating to muscle: myogenic pain …  

  • Myogenic regulatory factors — are basic helix loop helix (bHLH) transcription factors that regulate myogenesis: MyoD, Myf5, myogenin, and MRF4[1]. These proteins contain a conserved basic DNA binding domain that binds the E box DNA motif [2]. They dimerize with other HLH… …   Wikipedia

  • Myogenic contraction — refers to a contraction initiated by the myocyte cell itself instead of an outside occurrence or stimulus such as nerve innervation. Contents 1 Mechanisms 1.1 Unstable Membrane Potentials 1.1.1 Slow wave potentials …   Wikipedia

  • Myogenic mechanism — The myogenic mechanism is how arteries and arterioles react to an increase or decrease of blood pressure to keep the blood flow within the blood vessel constant. The smooth muscle of the blood vessels reacts to the stretching of the muscle by… …   Wikipedia

  • Myogenic determination factor 5 — Myf5 domain Identifiers Symbol Myf5 Pfam PF12232 InterPro IPR02203 …   Wikipedia

  • myogenic tonus — raumenų tonusas statusas T sritis Kūno kultūra ir sportas apibrėžtis Ilgai išsilaikantis raumenų tamprumas. atitikmenys: angl. myogenic tonus vok. Muskeltonus, m rus. мышечный тонус …   Sporto terminų žodynas

  • myogenic — adj. [Gr. mys, muscle; gennaein, to produce] Pertains to a muscle contraction initiated by nerve impulse; see neurogenic …   Dictionary of invertebrate zoology

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”