A&P Chapter 6
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Sarcomeres join together to form what?
Muscle Fibers join together for form what?
Muscle fasciculus joins together to form what?
What is the cell membrane of a muscle cell called?
What is the intracellular fluid of a muscle fiber?
What is titin?
springy filamentous protein that acts as the framework to hold actin and myosin together so the machinery of the sarcomere will work
What two structures does Titin attach to?
Z band, Myosin thick filament
What other substance is part of the sarcolemma?
The sarcoplasm contains large amounts of what 5 things?
- 1) potassium
- 2) magnesium
- 3) phosphate
- 4) protein enzymes
- 5) mitochondria for ATP
What is the job of a T tubule?
carry action potentials through the sarcolemma into the sarcoplasm
Aside from the sarcolemma, what else does the T-tubule come into contact with?
What part of the sarcoplasmic reticulum contacts the T tubule?
Which receptor is located on the sarcoplasmic reticulum? what is its role?
Ryanodine receptor - releases calcium from SR into sarcoplasm
What receptor is on the T tubule? what is its role?
DHP receptor - depolarization pulls DHP receptor back which opens the Ryanodine receptor on the terminal cisternae
Where is it believed the genetic defect for malignant hyperthermia lies?
What is the contractile element of the muscle?
what is the functional unit of the muscle?
What are the lateral borders of the sarcomere?
Where is the M line?
in the middle of the sarcomere
Where is the H zone?
contains myosin thick filament on either side of M line WITHOUT including any thin filament
Where is the A band?
Myosin thick filament on either side of the M line, all of the myosin (overlaps some thin filament)
Where is the I band?
Thin filament on either side of Z line - WITHOUT including any myosin thick filament
What is the function of the myosin head? (aside from binding with actin)
What are the 3 components of actin?
What is bound to F actin?
G-actin + ATP (binding site for myosin head)
What is the role of tropomyosin?
block the active site on actin
What are the three types of troponin? where/what do they bind?
- Troponin C - calcium
- Troponin I - actin
- Troponin T - tropomyosin
Actin and Myosin are said to be _________ (in relation to each other). What does this relationship result in?
interdigitated. Sliding action.
What initiates a muscle contraction?
List the steps of a muscle contraction beginning with the action potential and ending with how the muscle contraction terminates
- 1) action potential travels causes release of ACh
- 2) ACh opens ligand-gated ACh cation channels
- 3) opening of channels causes influx of sodium
- 4) influx of sodium causes depolarization of T tubule
- 5) depolarization of t tubule pulls DHP receptor which opens the Ryanodine receptor on terminal cistern
- 6) Open Ryanodine receptor allows influx of Ca++
- 7) Ca++ binds to troponin T
- 8) conformational change occurs with tropomyosin to reveal actin active site
- 9) ATP binds with myosin
- 10) myosin head cleaves ATP --> ADP + phos
- 11) myosin binds to active site on actin
- 12) ADP + phos is released as power stroke occurs
- 13) New ATP binds to myosin head allowing it to release from active site on actin
- 14) Repeats until the Calcium membrane pumps on the SR pump the calcium back and close the gates
In what position does the myosin head rest?
pivoted away from the M line
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