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Muscle Physiology - Skeletal
Moluecular Basis of Contraction
19
Physiology
Undergraduate 2
10/21/2008

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Term
Skeletal Muscle
Definition
  • Striated
  • Voluntary (Somatic)
  • Connected to at least two bones
Term

Muscle Fibers

Definition

Muscle cells

  • Runs the length of the muscle
  • Mulitnucleated
  • Innervated by only one muscle neuron
Term
Sacrolemma
Definition
Muscle fiber's plasma membrane
Term
Myofibrils
Definition

The muscle fiber's contractile machinery.

  • Bundle of overlapping thick/think filaments
Term
Sarcoplasmic Reticulum
Definition

Saclike membranous network that surrounds the myofibrils

  • Role in activation of muscle contractions
  • Function to store calcium ions and release when a muscle is stimulated to contract
Term

Transverse Tublules

 

(T Tubules)

Definition

Structures that transmit action potentials from the sarcolemma to cell's interior, releasing calcium from sarcoplasmic reticulum.

Term
Thick Filament
Definition

Filaments composed of myosin that form part of the contractile machinery of a muscle cell.

  • Each thick filament surrounded by 6 thin filaments
Term
Thin Filament
Definition

Filaments composed of actin that form part of the contractile machinery of a muscle cell.

  • Also contain troponin and tropomyosin in striated muscle cells
Term
Sarcomere
Definition

Functional unit of skeletal muscle.

  • Area between two Z lines
Term
Z Line
Definition

Cytoskeleton protein that connects thin filaments of adjoining sarcomeres.

Term
M Line
Definition

Supporting proteins that hold thick filaments together.

Term
A Band
Definition

Stacked set of thick filaments plus portions of thin filaments that overlap both ends of thick filaments.

Term
H Zone
Definition
Light area in A band where the thin filaments do not reach, only the thick filaments.
Term

I Band

Definition
Occupies space between the A bands of adjoining sarcomeres.
Term
Tropomyosin
Definition
Regulatory protein that extends over numerous actin molecules that blocks the myosin-binding sites in muscle at rest.
Term
Troponin
Definition

Regulatory protein that fastens down each end of the tropomyosin molecules so they do not move from myosin-binding sites.

  • Contains calcium-binding site that allows contraction
Term
Crossbridges
Definition

Heads of the intertwinning thck filaments that are wrapped around each other and actively generates a muscles mechanical force. 

  • Bridge gap between thick and thin filament
  • Contains an actin-binding site
  • Contains ATPase site
Term
Sliding Filament Model
Definition
Process of muscle contraction whereby thick and thin filaments slide past each other.
Term

Crossbridge Cycle

Definition

Mechanism that drives muscle contraction.

  • This is characterized by the stroke forward when the myosin binds to actin of thin filament.
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