Lecture 8 Flashcards
_____ bands of sarcomeres contain both thick and thin filaments, while ____ bands contain only thin filaments (hence the lighter appearance). The latter are bisected by ___ discs, which contain ____ and actin, anchoring the thin filaments. ____-lines bisect ______-bands and are regions where thick and thin filaments do not overlap.
A-bands
I-bands
Z-discs
Desmin
M-lines
A-bands
T-tubles account for about 80% of muscle cell surface area and form junctions with the ______ _______ (Ca++ storage organelle that encircles myofibrils.)
Sarcoplasmic Reticulum
Muscle fibers are innervated by ___-motorneurons, and each motor neuron may branch and innervate multiple fibers. A motorneuron and all the fibers it innervates are termed a ____ ____.
Alpha-motorneurons
Motor Unit
Synaptic “buttons” are covered by ______ cells.
Schwann
Myasthenia Gravis autoABs act in the same way ______ acts: by binding to Ach receptors and blocking the binding of Ach.
Curare
______ toxin and Conotoxin block presynaptic _____ channels, thus inhibiting release of Ach.
Molluscan toxin and Conotoxin
Ca++ channels
When Ca++ binds to troponin, ______ is displaced, uncovering _____ binding sites. This allows for the formation of the cross-bridges and sliding of thin filaments on thick filaments.
Tropomyosin
Myosin binding sites
_______ muscle is the only muscle that can be tetanized. This means multiple APs can be generated before the peak of tension in muscle contraction.
Skeletal
The ______ receptor from the T-tubules and the ________ receptor from the Sarcoplasmic reticulum articulate with one another in the sites of close apposition of T-tubular and SR membranes (Triads).
DHP receptors
Ryonadine receptors
The _____ 1S subunit of DHP receptors acts as a ____-gated Ca++ channel. The ______ subunit is necessary for the ______ subunit to be maintained in the neuronal cell membrane. The Ryanodine receptor acts as a _____-gated Ca++ channel (responds to calcium to release more), however, it is the allosteric interaction between this receptor and the DHP receptor that causes the Ryanodine receptor to open.
Alpha 1S subunit
Voltage-gated Ca++ channel
Ligand-gated
Beta subunit
Alpha subunit
_______ is the rod-shaped protein that binds to actin and covers Myosin binding sites.
Tropomyosin
______ is a protein comprised of three subunits. Tn-__ binds tropomyosin, Tn-__ inhibits myosin binding sites on actin, and Tn-__ has Ca++ binding sites (4 Ca++ per molecule). When Ca++ binds, the myosin binding site is uncovered.
Troponin
Tn-T
Tn-I
Tn-C
What is the sequence of Skeletal Muscle Cross-bridge cycling?
While phosphocreatine is the most immediate source of ATP in skeletal muscle, it has a very limited supply. So, for fast-twich fibers, ________ is the main source. For slow-twich fibers, ____ _____ is the main source. For intermediate fibers, both of those processes are sources of ATP.
Given the difference in sources of ATP for each fiber type, what would you expect of their respective Mitochondria composition? Conversely, how do the fibe diameters compare?
Glycolysis
Ox-Phos
Fast-twich have few, while slow-twich have many.
Slow-twich is thin, while fast-twich is thick.
