Muscle Types & Properties
These proteins link myofibrils together at the Z-line to maintain alignment during contraction.
What are desmin and vimentin?
Depolarization of the sarcolemma travels deep into the cell through these invaginations.
What are T-tubules?
According to Huxley’s sliding filament theory, thin filaments slide past thick filaments to shorten this unit.
What is the sarcomere?
Acetylcholine is synthesized by combining these two molecules.
What are acetyl-CoA and choline?
Intercalated discs contain these two adhesion junctions at the transverse regions.
What are fasciae adherens and desmosomes?
Smooth muscle can act as a secretory cell. Name two extracellular matrix proteins it can produce.
What are collagen and elastin (also glycosaminoglycans or proteoglycans)?
Each sarcomere has two of these structures, which interface with the sarcoplasmic reticulum to form a triad.
What are T-tubules?
Calcium binds this regulatory protein, shifting tropomyosin off the actin binding site.
What is troponin?
This enzyme degrades acetylcholine in the synaptic cleft.
What is acetylcholinesterase?
The lateral regions of intercalated discs contain these junctions, allowing ion flow.
What are gap junctions?
This type of smooth muscle allows fine, independent control because each fiber is individually innervated.
What is multiunit smooth muscle?
The wave of depolarization opens these channels on the terminal cisternae to release calcium.
What are voltage-gated Ca²⁺ channels?
The power stroke is triggered when this molecule is released from the myosin head.
What is inorganic phosphate (Pi)?
Calcium influx into the presynaptic terminal occurs through this type of channel.
What are voltage-gated calcium channels?
Cardiac T-tubules differ from skeletal T-tubules in this key way.
They open to extracellular space and rely on extracellular Ca²⁺, since SR stores are sparse
This type of junction allows unitary smooth muscle cells to contract in synchrony.
What are gap junctions?
The sarcoplasmic reticulum associates with T-tubules at these enlarged regions.
What are terminal cisternae?
After the power stroke, this molecule must bind to detach myosin from actin.
What is ATP?
These folds increase the postsynaptic surface area for acetylcholine receptors.
What are junctional folds (primary and secondary clefts)?
Smooth muscle contraction is regulated by phosphorylation of this protein.
What is myosin light chain?
Cardiac muscle’s inherent rhythmicity originates from this specialized structure.
What is the sinoatrial (SA) node?
This intermediate step links acetylcholine binding at the neuromuscular junction to calcium release from the sarcoplasmic reticulum.
What is sodium influx → sarcolemma depolarization → T-tubule propagation of the signal?
In rigor mortis, this molecule is absent, locking actin and myosin together.
What is ATP?
Choline is transported back into the presynaptic terminal by this symporter.
What is the choline/Na⁺ symporter?
This kinase is activated by the Ca²⁺–calmodulin complex to phosphorylate myosin light chains.
What is myosin light chain kinase (MLCK)?