2 -Skeletal Muscle Flashcards
Synonym for muscle fiber.
Muscle cell
Plasma membrane of a skeletal muscle fiber, surrounds the cytoplasm (i.e. sarcoplasm).
Sarcolemma (i.e. sarc = flesh)
Sarcolemma is associated with a coat of polysaccharides containing embedded collagen fibrils. These fibrils fuse with the […] of the muscle.
Tendon
Subunit of muscle.
Fasiculi
A fasciculus consists of a bundle of […].
Muscle fibers
Each muscle fiber consists of a bundle of […].
Myofibrils
Portion of a myofibril between two adjacent Z discs.
Sarcomere
Filaments that make up the sarcomere.
Actin/Thin and Myosin/Thick
Three proteins that make up an actin filament.
Actin, troponin, and tropomyosin
Component of actin filament, helical backbone, contains “active sites” where myosin can bind.
F-actin
Protein of actin filament, lies on top of F-actin, covers active/binding sites when contraction is undesired.
Tropomyosin
Protein of actin filament, attached intermittently along tropomyosin, contains three different proteins.
Troponin complex
Actin filaments attach to both Z discs of a sarcomere and […] with myosin filaments.
Interdigitate
Bands that make up a sarcomere.
1 Complete A band, two halves of I bands
A protien that maintains alignment between actin and myosin filaments, acts as a spring between a Z disce and the end of a myosin filament.
Titin
Synapse between a motor neuron and a skeletal muscle fiber.
Neuromuscular junction
Tiny, fluid-filled space between cells at a synapse.
Synaptic cleft
Stores molecules of transmitter in the presynaptic axon terminals, walls are made out of membrane.
Synaptic vesicle
Neurotransmitter associated with the synapes of the NMJ.
Acetylcholine (i.e. this will ALWAYS be the case)
Location of acetylcholine receptors in NMJ.
Embedded in the plasma membrane of the postsynaptic cell
The process by which a signal is passed between neurons or other excitable cells.
Synaptic transmission
Function of an action potential sent to a NMJ.
Release ACh into the synaptic cleft via synaptic vesicles.
As the AP arrives at the axon terminal it opens […] causing a depolarization.
voltage-gate calcium channels
Force permitting synaptic vesicles of the NMJ to undergo exocytosis, releasing ACh into the synaptic cleft.
Flow of calcium ions into the axon terminal
Amount of ACh molecules per each synaptic vesicle.
~5000
Amount of synaptic vesicles released per AP.
300
Upon ACh entering the synaptic cleft in can bind to ACh receptors embedded in the […]
Muscle fiber sarcolemma
Enzyme found in the synaptic cleft, breaks down ACh.
Acetylcholinesterase (i.e. some ACh is removed via reuptake or is dissolved)
Triggers the movement of cations (i.e. typically sodium) into muscle fibers via the opening of an ion channel.
Binding of two ACh molecules to a single ACh receptor
Graded potential produced due to the influx of sodium into a muscle fiber.
Excitatory postsynaptic potential (i.e. an end plate potential)
Can be recorded in muscle fibers due to the result of random discharge of a single synaptic vesicle.
Miniature end plate potential (mEPP)
Invaginations of the sarcolemma into the interior of the muscle fiber, lie at right angles to the myofibrils, are made of membrane and filled with ECF.
Transverse (T) tubules
Structure that carries the electrical signal into the interior of a muscle fiber.
T-tubule
Membranous structure that is adjacent and mostly parallel to the myofibrils, in contact with the T tubules, and a storage depot for calcium ions
Sarcoplasmic reticulum
A t-tubule protein, “senses” changes in voltage due to action potential.
Dihydropyridine receptor
Interacts with dihydropyridine receptor, acts as a calcium release channel.
Ryanodine receptor
Ion the is released from the sarcoplasmic reticulum to the sarcoplasm surrouding the myofibrils upon ryanodine receptor activation.
Calcium
Causes actin and myosin to dissociate.
ATP binding to myosin
Causes a conformational change in myosin that “cocks” the head.
Hydrolyziation of ATP to ADP plus phosphate (i.e. both of which remain attached)
Result of calcium binding to troponin C.
Troponin pulls on tropomyosin revealing the active site of actin (i.e. thus mysoin head can now bind to form a cross bridge)
Term for the head of myosin being attached to actin.
Cross bridge
Cause of myosin head “sprining”/”uncocking”.
Release of phosphate group (i.e. ADP remains attached)
Myosin and actin remain attached to each other until […] is released from myosin.
ADP
