Lecture 11 Flashcards
What are the 4 functions of skeletal muscle?
Movement, heat production, posture, communication.
Which tow Latin and Greek prefixes mean muscle?
“myo” and “sarco”
What is a myofibre (myocyte)?
A single muscle cell/strand.
What is a myofibril?
A group of contractile strands within a muscle cell (ie. myosin and actin arrangement)
Muscle cells/fibres can be up to __cm, and are ________, cylindrical, _____ nuclear.
Muscle cells/fibres can be up to 40cm, and are parallel, cylindrical, multinuclear.
What is striated muscle?
Striated muscle tissue is a muscle tissue that features repeating functional units called sarcomeres, in contrast with smooth muscle tissue which does not.
Is skeletal muscle striated or smooth?
Striated.
Myofilaments are arranged in a _________.
Myofilaments are arranged in a SARCOMERE.
What is a sarcomere?
The repeating protein arrangement of myofilaments.
What are myofilaments?
Thick or thin proteins in a sarcomere.
What is the sarcolemma?
The cell membrane of a striated muscle fibre cell
What is the function of the sarcoplasmic reticulum?
It is a type of ER which regulates Ca++ concentration in the cytoplasm of striated muscle cells.
How long is a sarcomere before and during contraction?
2 µm, 1 µm
What is the thick protein/filament in a sarcomere called?
Myosin
What is the thin protein/filament in a sarcomere called?
Actin
During muscle contraction, which sarcomere filament moves?
Actin, myosin does not move.
Actin and myosin int_________.
Actin and myosin interdigitate
Do both myosin and actin retain their length?
Yes!
Which two things are essential for muscle contraction?
Ca++ ions and Energy (ATP)
Muscle function depends on which 3 things?
- length of muscle fibres
- number of muscle fibres
- arrangement of muscle fibres
If a large ROM is required, muscle fibres are _______.
If a large ROM is required, muscle fibres are longer. Longer resting muscle = can shorten more, greater ROM.
Muscle fibres usually run ________ to line of pull (sheet, bundle).
Parallel to line of pull (sheet, bundle)
Tension (= force) is directly proportional to ________________.
Tension (= force) is directly proportional to cross-sectional area (CSA).
With a greater number of muscle fibres, does CSA and tension increase or decrease?
Increase.
What does it mean if muscle fibres are pennate?
Fibres run oblique to muscle tendon.
What are the advantages/disadvantages of pennate muscle fibres?
Reduced shortening but increased CSA
Even relaxed muscles are _______ ________.
Even relaxed muscles are SLIGHTLY ACTIVE. Nerve impulses activating muscle fibres.
What is a motor unit?
A motor unit consists of one somatic neuron and the muscle fibres supplied by its branches (a dozen - 1000s).
Does muscle tone produce movement?
No.
What is the purpose of muscle tone?
To help stabilise joins, maintain posture, and keep muscles firm and healthy.
