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By @mat_graphik

Spiercontractie en actiepotentiaal

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20 Questions

Wat is de eerste stap die leidt tot spiercontractie?

ACh vrijgeven door motor neuron

Hoeveel spiervezels kan een motorische eenheid gemiddeld bezenuwen?

150 spiervezels

Welk type spieren kan een motorische eenheid uit slechts 2 tot 3 spiervezels bestaan?

Oogspieren

Wat gebeurt er bij stimulatie door een motor neuron in alle spiervezels die deel uitmaken van zijn motorische eenheid?

Contractie

Wat is de naam van het proces waarbij meer motorunits worden geactiveerd en dit resulteert in een geleidelijke toename van spierspanning?

Recruitment

Wat is een motorunit?

Een motorneuron en de spiervezels die het innerveert

Wat gebeurt er wanneer Ca2+ zich bindt aan troponine tijdens spieractivatie?

Het veroorzaakt een conformationele verandering in de troponinemolecule, waardoor tropomyosinemoleculen zich verplaatsen van de actieve myosine-bindingsplaatsen op de actinemoleculen

Hoe verkorten sarcomeren?

Filamenten glijden over elkaar en Z-lijnen worden dichter bij elkaar gebracht

Hoe wordt de energie voor spiercontractie vrijgegeven?

Door de binding van ATP aan de myosinekoppen

Wat is excitation-contraction coupling?

Het proces waarbij een spiervezel wordt geactiveerd en een spiercontractie optreedt

Wat is het laatste onderdeel van de cross-bridge cyclus tijdens spiercontractie?

Ontspanning

Wat gebeurt er wanneer tropomyosinemoleculen bewegen van de actieve myosine-bindingsplaatsen op actinemoleculen?

Myosinekoppen kunnen binden aan actinefilamenten

Hoe worden myosinekoppen aan actinefilamenten bevestigd tijdens spiercontractie?

Door te roteren wanneer ze binden aan een actieve site op een actinefilament

Wat gebeurt er tijdens de power stroke in de spiercontractie?

Het aangehechte myosinehoofdje klapt zich om naar het centrum van de sarcomeer

Wat is noodzakelijk om de kruisbrug tussen actine en myosine te doorbreken na de power stroke?

Een nieuwe ATPmolecule bindt aan het myosinehoofdje

Hoe wordt de losgemaakte myosinekop gereactiveerd in de spiercontractie?

Terwijl deze het ATP splitst en de vrijgemaakte energie opslaat

Wat is noodzakelijk voor een langdurige spiercontractie?

Dat actiepotentialen elkaar snel opvolgen en de calciumafgifte vanuit de terminale cisternen doorgaat

Wat gebeurt er bij een kortdurende spiercontractie?

Als één enkel actiepotentiaal over het sarcolemma wordt geleid, worden de calciumionen zeer snel verwijderd en zal de contractie zeer kort van duur zijn

Wat gebeurt er aan het einde van een spiercontractie?

Ca2+ wordt teruggepompt naar het sarcoplasmatish reticulum waar het opgeslagen wordt tot er een nieuw actiepotentiaal aankomt in het sarcolemma

Wat is nodig voor zowel de contractiefase als relaxatiefase in een spiercontractie?

Energie

Study Notes

  • Activating more motor units is called "recruitment." This results in a gradual increase in muscle tension.
  • A motor unit consists of a motor neuron and the muscle fibers it innervates. Each motor unit contains many more muscle fibers than shown in the simplified diagram (Fig. 4.54a, b).
  • Motor units are not located next to each other, but are spread throughout the muscle and intermingled with motor units of other muscles.
  • Muscles are well supplied with blood vessels to provide necessary nutrients and oxygen for muscle contractions and to remove waste products.
  • In resting muscles, tropomyosin molecules cover the myosin binding sites on actin molecules, preventing myosin heads from binding.
  • When Ca2+ binds to troponin, it causes a conformational change in the troponin molecule, which in turn causes the tropomyosin molecules to move away from the active myosin binding sites on the actin molecules, allowing myosin heads to bind (Fig. 4.56).
  • Sarcomeres shorten when filaments slide over each other and Z-lines are brought closer together.
  • Myosin heads bind to active sites on actin filaments, forming cross-bridges.
  • Each myosin head is attached to ADP and a phosphate group in resting muscles.
  • The muscle contraction process consists of five interrelated steps: (1) exposure of active binding sites, (2) excitation-contraction coupling, (3) development of force, (4) relaxation, and (5) return to rest.
  • Ca2+ is stored in the sarcoplasmic reticulum and is released during muscle activation, allowing the active site on actin to be exposed.
  • Myosin cross-bridges form and bind to the active site on actin, initiating the contraction process.
  • During contraction, myosin heads produce force by pulling on the actin filament.
  • After the contraction, myosin heads release ADP and a phosphate group, allowing them to detach from the actin filament and return to their resting position.
  • The sliding filament theory explains how sarcomeres contract by the movement of thin actin filaments along the stationary thick myosin filaments.
  • The myosin heads are attached to ADP and a phosphate group in resting muscles, and are located in the direction of the actin filament.
  • In resting muscles, myosin heads are not bound to actin and Ca2+ is stored in the sarcoplasmic reticulum.
  • The figurative representation of a muscle in rest is shown in Figure 4.58.
  • Muscle contractions require large amounts of nutrients and oxygen and produce waste products, so muscles are well supplied with blood vessels.
  • The capillary network, arteries, and veins transport oxygen and nutrients to the muscles and remove waste products.
  • The myosin heads are attached to ADP and a phosphate group in resting muscles, which are located in the myosin head and store the energy released during ATP breakdown.
  • The excitation-contraction coupling is the process by which a muscle fiber is activated and a muscle contraction occurs.
  • The myosin heads form cross-bridges with the active site on actin, allowing the fibers to contract.
  • The cross-bridges generate force by pulling on the actin filament.
  • During relaxation, the myosin heads release ADP and a phosphate group and detach from the actin filament.
  • The myosin heads return to their resting position and are ready to begin the next contraction cycle.
  • The sliding filament theory explains how sarcomeres contract by the movement of thin actin filaments along the stationary thick myosin filaments.
  • This process is facilitated by the binding of myosin heads to active sites on actin filaments, forming cross-bridges.
  • The myosin heads rotate when they bind to an active site on an actin filament, causing the actin filament to be pulled in that direction.
  • The cross-bridge cycle consists of five steps: (1) attachment, (2) power stroke, (3) detachment, (4) relaxation, and (5) reattachment.
  • The energy for muscle contraction comes from the binding of ATP to the myosin heads.
  • The myosin heads bind to the active site on actin, forming a cross-bridge.
  • The myosin head undergoes a conformational change, causing the actin filament to be pulled in the direction of the myosin head, resulting in muscle contraction.
  • After the contraction, the myosin head releases ADP and a phosphate group and detaches from the actin filament, returning to its resting position and being ready for the next contraction.
  • The sliding filament theory explains how sarcomeres contract by the movement of thin actin filaments along the stationary thick myosin filaments.
  • The myosin heads bind to active sites on actin filaments, forming cross-bridges.
  • The myosin heads rotate when they bind to an active site on an actin filament, causing the actin filament to be pulled in the direction of the myosin head, resulting in muscle contraction.
  • The energy for muscle contraction comes from the binding of ATP to the myosin heads.
  • The myosin heads are attached to actin filaments through the formation of cross-bridges.
  • The myosin heads undergo a conformational change, causing the actin filament to be pulled in the direction of the myosin head and resulting in muscle contraction.
  • The myosin heads release ADP and a phosphate group and detach from the actin filament, returning to their resting position and being ready for the next contraction.
  • The myosin heads are attached to active sites on actin filaments, forming cross-bridges.
  • The myosin heads rotate when they bind to an active site on an actin filament, causing the actin filament to be pulled in the direction of the myosin head, resulting in muscle contraction.
  • The energy for muscle contraction comes from the binding of ATP to the myosin heads.
  • The myosin heads are attached to active sites on actin filaments, forming cross-bridges.
  • The myosin heads rotate when they bind to an active site on an actin filament, causing the actin filament to be pulled in the direction of the myosin head, resulting in muscle contraction.
  • The energy for muscle contraction comes from the binding of ATP to the myosin heads.
  • The myosin heads detach from the actin filament after the contraction, returning to their resting position and being ready for the next contraction.
  • The myosin heads are attached to active sites on actin filaments, forming cross-bridges.
  • The myosin heads rotate when they bind to an active site on an actin filament, causing the actin filament to be pulled in the direction of the myosin head, resulting in muscle contraction.
  • The energy for muscle contraction comes from the binding of ATP to the myosin heads.
  • The myosin heads are attached to active sites on actin filaments, forming cross-bridges.
  • The myosin heads rotate when they bind to an active site on an actin filament, causing the actin filament to be pulled in the direction of the myosin head, resulting in muscle contraction.
  • The energy for muscle contraction comes from the binding of ATP to the myosin heads.
  • The myosin heads detach from the actin filament after the contraction, returning to their resting position and being ready for the next contraction.
  • The myosin heads are attached to active sites on actin filaments, forming cross-bridges.
  • The myosin heads rotate when they bind to an active site on an actin filament, causing the actin filament to be pulled in the direction of the myosin head, resulting in muscle contraction.
  • The energy for muscle contraction comes from the binding of ATP to the myosin heads.
  • The myosin heads are attached to active sites on actin filaments, forming cross-bridges.
  • The myosin heads rotate when they bind to an active site on an actin filament, causing the actin filament to be pulled in the direction of the myosin head, resulting in muscle contraction.
  • The energy for muscle contraction comes from the binding of ATP to the myosin heads.
  • The myosin heads detach from the actin filament after the contraction, returning to their resting position and being ready for the next contraction.
  • The muscle fiber is activated when a muscle action potential reaches the muscle

Leer meer over de opeenvolging van acties die leiden tot spiercontractie, waaronder de rol van motor neuronen, ACh receptoren, Na+ instroom, actiepotentiaal en de afgifte van Ca2+ uit het sarcoplasmatisch reticulum.

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