Final Flashcards
What are t-tubules?
Transverse tubules that are extensions of the sarcolemma
What can be found on the sarcolemma?
motor end plate (has ligand gated channels), voltage gated NA+ and K+ channels, nuclei,
WHat do t-tubules contain? How does this explain their function?
contain voltage gated channals and voltage sensitive receptors. the ap from sarcolemma propogates to the t-tubles, and triggers receptors that Ultimately leads to release of Ca2+ from internal storage
WHAT IS THE sarcolemma?
the cell wall of a muscle cell/fibre
What is the role of the sarcolemma?
To receive action potentials through motor end plate.
WHat does the motor end plate contain?
Neuromusclar juction. This junction has ligand-gated channels.
What is the terminal cisternae of the sarcoplasmic reticulum?
It is where Ca+ is stored. It releases the Ca+ for contraction when receptors on transverse tubules receive the action potential
What is the sarcoplasm?
the cytoplasm of the muscle fiber/cell
What does the sarcoplasm contain?
sarcoplasmic retoiculum (terminal cisternae), mitochondria, myoglobin, glycogen granuses, myofibrils
WHat type of proteins are found in sarcomeres?
contractile, regulatory, and stabilizing
Which proteins are stabilizing?
Titin (thick), Z-line and M-line
WHat type of proteins are regulatory? Which myofilament are they associated with?
troponin and tropomyosin. thin
What type of proteins are contractile?
Myosin (thick) and actin(thin)
How are myoglobin and glycogen granules used for energy? How do they influence appearance?
Myoglobin stores O2 which is needed for ATP production in the mitochondria. Glycogen granules stores energy in the form of many glucose molecules. Myoglobin provides red pigment. If a molecule is white, it means it doesn’t have much myoglobin and relays on glycogen for glycolysis
What is titin?
runs through the core of the thick filament and attaches it to the Z-line
Describe the structure of thick filaments and myosin
myosin = tail, hinge, head
thick filaments have many individual myosin molecules clustered together
What contains binding sites for myosin heads?
globin (G) actin molecules
Describe the structure of filamentous (F) actin
Individual g-actins are like beads that come together to form a string.
Filamentous actin is the string of actins coming together and intertwining
What covers actin active sites for myosin heads when muscle is at rest?
Tropomyosin covers the active sites on actin
What holds tropomyosin in place?
troponin
Describe the A-band
It is the entire length of the myosin(thick filament). Includes the actin that overlaps
Describe the I band
Length of thin filement that do not overlap with the myosin. a z-line (disc) will be in the middle
How are thick filaments anchored and stabilized?
They are anchored by proteins in the middle (M-line). Titin extends through the thick filaments to attach to the end of the sarcomere(Z-line)
Where do thin filaments attach?
They attach to the z-line proteins
What is the zone of overlap?
The area were thick and thin filaments overlap
WHat is the H-band?
Length of the thick filament that does not overlap with thin filaments
What is another name for titin?
Elastic Filaments
Describe the sliding filament mechanism of contraction.
As the muscle contracts, the A band doesn’t change in length. INstead, the actin/thin filaments slide across the thick filaments as moves toward the m-Line . Titin gets compressed. This means the Z-line is pulled toward the middle by the actin. Ultimately, the zone of overlap increase, I band decrease, and H zone decreases
