Muscle Flashcards
What can be found in the deep fascia?
Large blood vessels, nerves and small amounts of fat
What is the deep fascia?
Dense connective tissue which surrounds adjacent muscles, in between muscles and bends them into functional groups.
Describe and explain the appearance of skeletal muscle
Pink due to pigmentation, myoglobin and vascularisation
In skeletal muscle what does the power output depend on?
Number of muscle fibres which can be increased by increased exercising
Where is the T tubule located in skeletal muscle?
AI junction
Describe the layers of skeletal muscle
Fascicles, myofibres, myofibrils, microfilaments. Epimysium surrounds muscles/organs, perimysium surrounds fascicles and endomysium surrounds individual muscle cells/fibres
What types of fascicles can there be?
Architectural patterns - parallel, circular, pennate etc. the pattern determines the range and power.
Describe red muscle in skeletal muscles.
Slow - lots of myoglobin, rich vascularisation, numerous mitochondria, fatigue slowly, rich in oxidative enzymes, poor in ATPase, fewer NMJ
Describe white muscle in skeletal muscles
Fast - poor vascularisation, few myoglobin, few mitochondria, faster and stronger contractions, poor oxidative enzymes, more NMJs
What are cross bridges?
HMM - contraction via breakdown of ATP by myosin ATPase
Describe the banding in skeletal muscle
Myosin filament, H zone, A band, Z line and I band
Describe the effects of contraction on the bands in skeletal muscle
I and H become smaller in length whereas A remains the same
Describe the structure of actin
Double helical, tropomyosin lies in a groove
Describe the structure of troponin
Attached through tropomyosin, one is a Ca2+ receptive protein
Out of myosin and actin which is thick and which is thin?
Myosin = thick Actin = thin
What is a tendon?
Fibrous cord that extends from the muscle to connect it to bone
What is aponeurosis?
Broad, flat structure that attaches bone or other adjoining structures
What are the functions of smooth muscle?
Slow contraction, hormonal stimulation, gap junction, less ordered interaction of myosin and actin
Describe the structure of smooth muscle
Fusiform, long cells. Only a few exhibit nuclei when transversely sectioned
Where would you find smooth muscle?
Contractile part of wall of GI tract, respiratory tract, ducts/glands, urinary and genital ducts, veins/arteries, muscles of iris in eye
Can skeletal muscle regenerate?
Yes, to a degree. In gross damage scar tissue will be formed
What do purkinje fibres do?
Spread impulse to the heart
Describe the structure and location of purkinje fibres
Fewer myofilaments, fibrils and Fewer intercalated discs. Beneath endocardium on internal surface of the heart. Commonly found along the inter-ventricular septum.
Describe intercalated discs
They are specialised junctions. Facing membranes have grooves and reciprocal pits. They have strong horizontal components (Z bands). Weaker vertical components contain gap junctions
What is brown atrophy of heart?
Atrophy of heart caused by lipofuscin pigment
Where are the T tubules in cardiac muscle?
Lie at the Z band
What are the main characteristics of cardiac muscle?
Elongated nuclei, fibres may bifurcate, cells joined by intercalated discs, fibres contain large numbers of sarcosomes with many cristae
Does cardiac muscle regenerate?
Does not regenerate when injured. Cardiac muscle is more resistant to injury than the other types of muscle. Damage is contained by formation of fibro-connective scar tissue
What is the role of calcium in muscle contraction?
Triggers contraction via troponin. Sarcoplasmic reticulum forms vesicles which in the presence of ATP reversibly take up Ca2+. Release of Ca2+ under control of T tubule membrane depolarisation triggers contraction via troponin.
How does smooth muscle recuperate after injury?
Proliferation and differentiation of primitive smooth muscle into new muscle fibres
How does skeletal muscle recuperate after injury?
Connective tissue of endomysium and perimysium divides and differentiates into myoblasts which fuse to form new muscle fibres
What is myopathy?
Muscle weakness that is not a result of NS or emotional disorders. Causes impaired muscles, cramps etc.
What is atrophy?
Wasting of muscle tissue as a result of lack of use, immobilisation, loss of nerve supply
What is dystrophy?
Defective muscular nutrition
What is hypertrophy?
Increased number of myofibrils, increased exercise, in pregnancy the uterus increases in size.
