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30 Cards in this Set
- Front
- Back
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What are the three types of muscle tissue?
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Skeletal, smooth and cardiac
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What is muscle composed of?
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Elongated cells called myofibres, or muscle fibres.
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How can muscle types be classified?
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Microscopic appearance: striated = skeletal & cardiac
Innervation: voluntary = skeletal, involuntary = cardiac & smooth |
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How do skeletal muscle cells appear under the LM?
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- Multiple nuclei
- Nuclei are located peripherally (REMEMBER) - Skeletal muscle cells can be 1mm-10cm long - Striations can be seen under high magnificatio - Striations not visible in cross section |
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What is a group or bundle of myofibres?
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A fascicle
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What are the three connective tissues surrounding muscle?
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- Epimysium (surrounds the entire muscle)
- Perimysium (surrounds the fascicles) - Endomysium (reticular fibres & basal lamina surrounding individual myofibres) |
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What connects muscle to bone?
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Connective tissue - at the end of muscle the muscle cells gradually disappear & the connective tissue increases. The connective tissue becomes a tendon.
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What is a tendon?
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Attaches muscle to bone. Fusion of the epimysium, perimysium & endomysium.
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What are the contractile proteins within muscle cells?
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Myofibrils - composed of myofilaments. Myofilaments are arranged in a very regular pattern that gives skeletal muscle its striated appearance.
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Do muscle cells multiply when you exercise?
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NO. Myofibrils multiply.
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What are the types of myofilaments?
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- Thick (primarily myosin)
- Thin (primarily actin) |
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How are the myofilaments arranged?
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Arranged in a regular overlapping pattern, gives skeletal & cardiac muscle the striated appearance.
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How long is a sarcomere at rest?
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Aout 2.5um
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What are actin and myosin?
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Proteins within the cell, form myofilaments.
Actin: arranged in double helix Myosin: arranged like two golf clubs with intertwined shafts and heads pointing in opposite directions. Has an actin-binding site and an ATP-ase. |
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How do muscles contract?
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All sarcomeres in a muscle shorten as the thick and thin filaments slide over each other. This process relies on calcium ions, regulated by the sarcoplasmic reticulum.
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What is the motor end plate?
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Where a nerve action potential arrives at the sarcolemma forming a neuromuscular junction.
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Where is cardiac muscle derived from?
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Mesoderm
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Where is cardiac muscle found?
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In the heart and large arteries close to the heart
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What is the molecular structure of cardiomyocyte?
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- 50% of cell is mitochondria
- Centrally placed nucleus - Striated - Cells are joined by intercalated disks |
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What surrounds each muscle cell?
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- Endomysium, contains an extensive capillary system
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What are intercalated discs?
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- Located between cardiac muscle cells
- Can be transverse (fascia adherens and desmosomes) or longitudinal (gap junctions) |
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Where is smooth muscle found?
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- gut
- bladder - ureters - uterus - blood vessels |
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What is the structure of smooth muscle cells?
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- elongated
- single elongated nucleus - Stains pinker than CT in H&E but looks similar |
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What can cause smooth muscle cells to contract?
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- Mechanical, electrical, chemical stimulation
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How do smooth muscle cells contract?
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Smooth muscle cells contract by hydrolysing ATP to produce ADP and energy which in the presence of calcium causes an interaction between actin and myosin filaments.
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What is a focal density?
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It is an area where the cell membrane acts as an attachment point for the actin.
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What is the speech of cardiac muscle contractions compared to smooth?
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Slower, uses ATP at 10% of the rate as skeletal muscle. Can maintain a contracted state for longer periods without as much energy expenditure.
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How does calcium enter the cell?
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Via caveolae - no T tubules and only rudimentary SR.
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Regeneration and growth in muscle cells?
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Cardiac: can get larger, limited regeneration, do not increase in number.
Skeletal: can repair after injury through satellite cells, can become larger. Smooth: can become larger, proliferate & easily regenerate |
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What are the other types of contractile cells in the body?
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1. Myoepithelial cells - glands
2. Myofibroblast cells - repairing tissue 3. Pericytes - control lumen size of capillaries |
