muscles Flashcards
Types of Muscle
- Skeletal muscle
- Cardiac muscle
- Smooth muscle
Skeletal muscle tissue
- attached to bones and skin
- striated
- voluntary
- powerful
- multinucleate
Cardiac muscle tissue
- only in heart
- striated
- involuntary
- uni or binucleate
Smooth muscle tissue
in walls of hollow organs(stomach, urinary bladder, airways
- not striated
- not uninucleate
- involuntary
Common Features
- Elongated cells
- myofilaments
- —actin
- –myosin
- Terminology
- –myo and sacro
Special characteristics of muscle
- Excitability
- –ability to receive and respond to stimuli
- Contractility: ability to shorten when stimulated
- extensibility: ability to be stretched
- Extensibility: ability to be stretched
- Elasticity: ability to recoil to resting length
Muscle Functions
- Movement of bones or fluids (e.g. blood)
- Maintaining posture and body position
- Stabilizing joints
- Heat generation (especially skeletal muscle)
How many arteries and nerves are in each muscle?
Each muscle is served by one artery, one nerve, and one or more veins
What is connective tissue sheaths called?
PICTURE BECCA
- Epimysium:
- —dense regular connective tissue surrounding entire muscle (groups of perimysium)
- Perimysium
- —fibrous connective tissue surrounding fascicles (groups of muscle fibers)groups of endomysium
- Endomysium: fine areolar connective tissue surrounding each muscle fiber
Muscles attach 2 ways. What are they?
PICTURE 9.1
- Directly
- —epimysium of muscle is fused to periosteum of bone or perichondrium of cartilage
- Indirectly
- —connective tissue wrappings extend beyond the muscle as a replica tendon or sheetlike aponeurosis
What is Sarcolemma?
plasma membrane surface
What is sarcoplasm?
cytoplasm of muscle cells
What is myofibrils?
contractile elements of skeletal muscle
What is in s skeletal muscle fiber (cell)
- cylindrical cell 10 to 100 in diameter up to 30 cm long
- multiple peripheral nuclei
- many mitochondria
- numerous glycosomes for glycogen storage and myoglobin for 02 storage
- also contain highly specialized organelles: myofibrils, sarcoplasmic reticulum, and T tubules
Myofibrils
PICTURE OF Myofibril
- Densely packed, rodlike elements
- –80%of cell volume
- Exhibit striations: perfectly aligned repeating series of dark A bands and light I bands
- Composed of contractile proteins
- —Thick filaments - myosin
- —Thin filaments - actin
Sarcomere
- Smallest contractile unit (functional unit) of muscle fiber
- Region of myofibril between two successive Z discs
- Composed of thick and thin myofilaments made of contractile proteins
Features of a Sarcomere
PICTURE OF A SARCOMERE
- Thick filaments: run the entire length of A band
- Thin filaments: run the length of I band and partway into the A band
- Z disc: coin-shaped sheet of proteins that anchors the thin filaments and connects myofibrils to one another
- H zone: lighter mid region where filaments do NOT overlap
- M line: line of protein myosin that holds adjacent thick filaments together
Ultrastructure of thick filament
Composed of the protein myosin
- –1. myosin tail forms central part of dark band
- –2. myosin heads contain:
- —–binding sites for actin of thin filaments
- —–during contraction forms a cross bridge with actin
- —-binding sites for ATP
- —-ATPase enzymes
Regulatory Proteins of Actin
- Tropomyosin
2. Troponin - polypeptide complex
What does tropomyosin do?
- Spirals around actin
- Block myosin head binding sites during relaxed state
What is troponin?
- binds Ca2
- binds tropomyosin (TnT)
- Inhibitory protein that binds actin (Tnl)
Elastic filament
PICTURE 9.3
- composed of protein Titin
- Extends from Z disk to the run within the thick filament to the M line
- Helps to resist excessive stretching
Intracellular tubules in muscles
- sarcoplasmic reticulum
- T-tubules
Sarcoplasmic Reticulum (SR)
- Network of smooth endoplasmic reticulum surrounding each myofibril
- Pairs of terminal cistern form perpendicular cross channels
- Stores Ca2+
- Functions in the regulation of intracellular Ca2+levels