Muscle Tissue Flashcards
(52 cards)
Sphincters are operated by what type of muscle?
Skeletal muscle
What is being described: Non-dividing cells surrounded by satellite cells and contained in a sarcolemma.
Muscle fibre
What are muscular satellite cells?
These arise from the myoblast cells that do not fuse to form myotubes. They remain as undifferentiated muscle stem cells/mesenchymal cells that can replace muscle fibres lost due to injury.
When a satellite cell is activated by injury, what happens?
The satellite cell undergoes asymmetric division - forming one satellite cell and one myoblast. The myoblast matures and fuses to the muscle fibre.
True or false: Skeletal muscle is striated
True,
True or false: Skeletal muscle is controlled by the autonomic nervous system
False, it requires somatic or voluntary input.
Fused myocytes/tubular cells formed from myoblasts form __1__ and are surrounded by __2___ (connective tissue around muscle cells). Bundles of 1 form muscle fascicle, surrounded by __3__. The __4__ covers all the fascicles.
1) Muscle fibres (cell)
2) Endomysium
3) Perimysium
4) Epimysium
What are the myofilaments inside a muscle fibre?
Thin: actin, tropomyosin, troponin Thick: myosin
Remember the muscle fibre is composed of many myofibrils and each myofibril which is also called a muscle cell is made up of myofilaments
What is a myofibril?
Any one of the contractile threads found in a muscle fibre.
What are transverse tubules (T-tubules) and what do they do?
‘Tunnels’ throughout muscle fibres that conduct action potentials from the sarcolemma to initiate contraction.
What is a sarcomere?
The smallest functional unit of muscle (not the smallest structural unit). Contraction happens here. Basically the area between 2 Z lines.
What forms the I band of the sarcomere?
Only thin bands of actin and it looks lighter because actin is isotropic/thin.
Think there’s only one Ishika
What forms the A bands of the sarcomere?
Thick bands of myosin (Anisotropic), overlapping with actin, therefore, appears dark.
Think A as in Alpa has 2 children
What is the Z line in the sarcomere?
Protein chain that supports the actin filaments (I bands). Z = zig zag
Remember Z at the end of the alphabet thus, at the end of the sarcomere
What is the M line in a sarcomere?
The middle line. (M for middle). Consists of proteins supporting the thick myosin filaments.
Where is the H zone on a sarcomere?
The central region that contains only myosin thick filaments.
Think, H for a house and only Maisuryas (Myosin) in the house
How is contraction achieved in the sarcomere?
Sliding of thick and thin filaments in the zone of overlap.
True or false: Striations can be found in cardiac muscle
True
Is cardiac muscle mononucleated or multinucleated?
Mononucleated. Cells are not fused.
Is skeletal muscle mononucleated or multinucleated?
Multinucleated. Myoblasts fuse together to form multinucleated fibres
Cardiac muscle contains intercalated discs at the ends of the cardiocytes. What structures are found here and why?
Gap junctions and desmosomes allow exchange of ions and molecules - allows spread of action potentials.
True or false: A sarcomere Z line appears zig zag shaped, and the M line appears straight
True z line = zig zag
True or false: cardiac muscle contraction is not reliant on the nervous system for stimulation.
True Pacemaker cells stimulate contractions; the nervous system can only alter the rate of activity.
True or false: Smooth muscle is incapable of regeneration
False. Smooth muscle cells can divide, therefore the tissue is capable of regeneration.
