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
