Muscular tissue

Skeletal Muscle

Skeletal muscles are a key component of the human muscular system, responsible for various functions.

Thick filaments consist of 200-300 myosin molecules, 1.6 mm long and 15 nm in diameter

Each molecule consists of two pairs of light chains and two heavy chains

S1 binds ATP and cross bridge with actin

Each thin filaments is a polymer of G-actin, 1 mm long and 8 nm in diameter

Troponin has 3 globular subunits TnC has a great affinity for calcium, TnT binds to tropomyosin, and TnI binds to actin, preventing the interaction of it with myosin.


Smooth Muscle

Smooth muscle is a type of muscle tissue found in various systems of the body, playing a crucial role in involuntary movements.

Involuntary, in the wall of hollow viscera usually form sheets

Fusiform, 30-200 mm long

1 central nucleus

No striations, no T-tubule system

Surrounded by an external lamina

Thin filaments are composed of actin with tropomyosin but no troponin

Thick filaments are composed of myosin

Cardiac Muscle

Cardiac muscle, also known as myocardium, is a specialized type of muscle tissue found only in the heart.

Ca ions of extra cellular matrix enter the cells through T-tubule and calcium-sodium channels

Atrial cell secretes atrial natriuretic peptide, cause Na and H2O loss via kidney

Intercalated disks are specialized cell junctions

Cell membrane in these disks approximate each other

Have a transverse portion where there are desmosomes and fascia adherents and a lateral portion which has many gap junctions

Cells joined end-to-end by intercalated disks

Cells branched and arranged in layers (Lamina) separated by slender CT sheets that convey vessels and nerves and conducting system

15 mm diameter, 80 -100 mm long

1-2 central achromatic oval nuclei

Extracellular matrix is the primary calcium source for contrition

Sarcoplasmic reticulum does not form terminal cisternae and extensive networks

Dyad forms by SR and T-tubules in vicinity to Z line

T- tubules are 2.5 times the diameter of skeletal muscle and have external lamina

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