MUSCLE MUSCLE TISSUE TISSUE

Myology  Anatomical study of muscles is called myology  Mostly myology is concerned with skeletal muscles  Together with bones, joints, tendons and ligaments, they form the musclosketal system of levers that provide body movements  The musculosketal system work closely together with the nervous system to attain a coordinated and meaningful body movements.

Types of Muscles  Skeletal muscle -attached to bones -striated-voluntary-cylindrical -multinucleate & peripheral

Types of Muscles...  Smooth muscle -visceral organs of GIT, -visceral organs of GIT, -blood vessels etc -blood vessels etc -non-striated, -non-striated, -involuntary -involuntary -spindle-shaped, -spindle-shaped, -uninucleate -uninucleate

Types of Muscles...  Cardiac muscle -heart (myocardium) -striated-involuntary-branched -intercalated discs

Muscle Functions  Movement  Maintain posture  Stabilize joints  Heat production

Characteristics of Muscle Tissue  Excitable (+ neuron, adipocytes) -response to electrical impulses  Contractile -shorten and lengthen to generate mechanical energy  Elongated cells

Terminology  Has special terminology Muscle cell= myofibre or myocyte Muscle cell= myofibre or myocyte Myofibrils= contractile elements Myofibrils= contractile elements Myofilaments= actin and myosin Myofilaments= actin and myosin Sarcoplasm= muscle cytoplasm Sarcoplasm= muscle cytoplasm Sarcoplasmic reticulum= muscle ER Sarcoplasmic reticulum= muscle ER Sarcomere= contractile unit/segment Sarcomere= contractile unit/segment Sarcolemma= cell membrane/ plasmalemma Sarcolemma= cell membrane/ plasmalemma Sarcosome= mitochondria (rare use) Sarcosome= mitochondria (rare use)

Skeletal muscles cells -Connective tissue wrappings (well developed in skeletal muscles) Endomysium - Loose areolar and elastic fibres cover individual myofibres individual myofibres Perimysium -Collagen fibre fascicule (a bundle of muscle cells) -Collagen fibre fascicule (a bundle of muscle cells) Epimysium -Dense fibrous connective around entire muscle -Dense fibrous connective around entire muscle

Fig. Muscle organization

Fig. Myofibre

Fig. Sarcomere

Fig. Myofibril organization

Actin (thin filaments)

Fig. Myosin (thick filament)

Fig. Skeletal muscle fibre- H/E

Slow twitch (red) fibers -Slowly contraction -High O 2 usage -Rich blood supply and myoglobin -Hence red fibers -Less fatigue and high endurance -Rich mitochondria -Little glycogen -Less contractile force -E.g. postural muscles

Intermediate fibres Intermediate fibres Fast contraction Fast contraction Aerobic metabolism Aerobic metabolism Moderate blood, myoglobin and mitochondria, Moderate blood, myoglobin and mitochondria, Moderate glycogen Moderate glycogen Moderately fatigue resistance Moderately fatigue resistance Intermediate power Intermediate power E.g walking, sprinting E.g walking, sprinting

Fast twitch (white) fibres -contract fast -anaerobic metabolism -little myoglobin, blood, -mitochondria, increased -glycogen--white fibers fatigable -powerful, short-term--ball hitting

White and red muscle fibres

Nerve and blood supply Muscle tissue is richly innervated by nerves Each myofibre is innervated by one nerve fibre Or one nerves fibre innervates several myofibres Motor innervation: At the neuromuscular junction found at the sarcolemma. Acetylcholine is the neurotransmitter found at the sarcolemma. Acetylcholine is the neurotransmitter Sensory innervation At the specialized muscle spindles inside the muscle near myotendinous junctions They are proprioceptive fibres for strech Muscle is also richly supplied with blood. Small arteioes run within the muscle fascicles

Neuromuscular Junction Nerve ending Muscle cell

Muscle regeneration Muscle fibres have limited ability to regenerate after injury Fibrous tissue multiply to replece injured muscle cells Satellite cells can also differentiate to replace dead cell

Muscle mass Hypertrophy Hypertrophy -Increase in muscle fibre cell size with exercise -Increase in muscle fibre cell size with exercise Atrophy Atrophy -Decrease in muscle fibre size e.g. -Decrease in muscle fibre size e.g. Hyperplasia Hyperplasia - Increase in number of muscle cells - Increase in number of muscle cells

Smooth muscle cells

Cardiac muscle cells

Optics of light microscopy