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Physiology - Basic Muscle
Skeletal Muscle, Smooth Muscle, and Cardiac Muscle Overview
21
Physiology
Graduate
09/10/2009

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Term
Myofibril
Definition
A slender striated strand within skeletal and cardiac muscle fibers and composed of bundles of myofilaments. Myofibrils occur in groups of branching threads running parallel to the cellular long axis of the fiber
Term
Sacromere
Definition
The smallest functional unit of a myofibril. Sarcomeres occur as repeating units along the length of a myofibril, occupying the region between Z lines of the myofibril
Term
Myofilament
Definition
The protein filaments that construct a myofibrils (Actin and Myosin)
Term
Actin
Definition
The thin filament of sacromeres.  Is coated in Tropomyosin and contains the binding site for the ATPase Head of Myosin
Term
Myosin
Definition
The thick filaments of Sarcomeres.  Contains the ATPase head which allows for the muscle contraction.
Term

Sarcoplasmic Reticulum

(SR)

Definition
An intracellular membrane network that plays a critical role in the regulation on intracellular Ca2+ concentration
Term
T-tubules
Definition
Invaginations of the sarcolemma (plasma membrane) that allow for quick depolarization of the cell 
Term
α-motor neuron
Definition
The innervation neurons of skeletal muscle with soma's present within the ventral horn
Term
Motor Unit
Definition
A motor nerve and all of the muscle fibers innervated by that nerve
Term
Ryanodine Receptor
Definition

(Calcium Release Channel)

 

The receptors found in the terminal cisternae, are responsible for the elevation in intracellular Ca2+, and bind Ryanodine.

Term
Dihydropyridine Receptor
Definition

(L-type voltage-gated Ca2+ Channel)

 

Stimulated thru contact with the Ryanodine Receptor of the SR

Term

Sarcoplasmic Endoplasmic Reticulum Calcium ATPase

(SERCA)

Definition

The pump in thru which Ca2+ is resequestered into the SR.

 

Most abundant protein in the SR

Term
g-Actin
Definition
The single actin molecules
Term
f-actin
Definition
The two stranded helical filament formed from g-actin
Term
Tropomyosin
Definition

Protein molecules that cover the binding sites of the actin molecule in the form of a dimers.

 

The Dimers have a T, I and C subunit.  T binds more tropomyosin, I facilitates the inhibition of the binding of myosin, and C binds Ca2+ promoting movement of the troponin dimer to allow binding of Myosin

Term
Fast-Twitch Fibers
Definition
Fast glycolitic, fatigue prone, pale fibers
Term
Slow-Twitch Fibers
Definition
Slow Oxidative, Fatigue resistant, red fibers
Term
Isometric Contraction
Definition
Stimulation of a muscle during which the origin and insertion of the muscle do not move
Term
Isotonic contraction
Definition
Stimulation of a muscle during which the origin and insertion do move
Term
Single-Unit Smooth Muscle
Definition
Smooth muscle cells are electrically coupled so that stimulation of one cell is followed by stimulation of adjacent cells.
Term
Multi-Unit Smooth Muscle
Definition
Smooth muscle cells are not electrically coupled, so stimulation of one does not stilumate another adjacent cell
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