Muscle Tissue Flashcards
What are the general features of muscle tissue?
Uses ATP for movement, posture, and heat production. Made of myocytes (muscle fibres).
How much of the body’s tissue mass is muscle?
50% of total tissue mass.
What are the three types of muscle?
Skeletal, cardiac, and smooth muscle.
What is the structure of skeletal muscle cells?
Long, cylindrical, multinucleated, peripheral nuclei, striated appearance.
Is skeletal muscle voluntary or involuntary?
Voluntary control.
What are the functions of skeletal muscle?
Movement, heat production, posture, and protection.
What creates the striations in skeletal muscle?
The arrangement of myofibrils within the muscle fibre.
What are myofibrils?
Long, cylindrical structures inside muscle fibres, made of myofilaments (actin & myosin).
What are myofilaments?
Thin filaments = actin and thick filaments = myosin.
What is a sarcomere?
The functional unit of a myofibril, separated by Z discs.
What are the key components of a sarcomere?
A band (thick filaments), I band (thin filaments), H zone (only thick), M line (middle), Z disc (boundary).
What is titin?
A molecular spring linking the Z disc to the M line, giving tension to the I band.
What are the connective tissue layers of skeletal muscle?
Epimysium (surrounds muscle), Perimysium (surrounds fascicles), Endomysium (surrounds fibres).
What is the sarcolemma?
The cell membrane of a muscle fibre.
What is the sarcoplasm?
The cytoplasm of a muscle fibre, filled with myofibrils.
What is a fascicle?
A group of 10-100 muscle fibres.
What is the structure of cardiac muscle?
Single central nucleus, striated, branched fibres, involuntary.
What connects cardiac myocytes?
Intercalated discs.
What is the function of intercalated discs?
Allow communication & adhesion between cardiac cells using desmosomes & gap junctions.
What is the role of desmosomes in intercalated discs?
Prevent cell separation by binding intermediate filaments for adhesion.
What is the role of gap junctions in intercalated discs?
Allow electrical signals to pass for coordinated heart contractions.
What is the structure of smooth muscle?
No striations, spindle-shaped, small, involuntary.
Where is smooth muscle found?
Blood vessel walls (vasoconstriction), digestive tract, iris, erector pili (skin).
What filaments does smooth muscle contain?
Myosin (thick) and actin (thin).
How does smooth muscle contract?
Actin filaments attach to dense bodies (like Z discs), tension is transmitted via intermediate filaments, causing twisting contraction.
What are dense bodies made of?
Actinin.
Do all smooth muscle cells have gap junctions?
No - some (e.g., gut) have many, some (e.g., iris) have none.
