6-8 Muscle Flashcards
Each myofibril consists of many ________ surrounded by the SR and t-tubule system. These are highly organized contractile and structural proteins!
Contractile proteins consist of _____ and _____ filaments. Myosin is a _____ filament with intertwined heavy chains with globular heads. Bind to actin and have ATPase activity!
Actin is a _____ filament and needs two strands for a helix. F actin is made of many G actin molecules and has myosin binding sites.
You have tropomysin with is a double stranded helix around _____. Covers myosin binding sites.
Sarcomeres! Thick and thin. Thick. Thin. Actin
(LO) Beginning with release of Ach from the motor neuron and ending with muscle relaxation, describe the process of excitation-contraction coupling in skeletal muscle with respect to receptors, channel activation, ionic flow, actin-myosin cross bridge cycling, the role of ATP and how force is generated.
- AP begun in the NMJ depolarizes down sarcolemmal membrane and T-tubue system.
- AP causes a conformation change in DPHR, which causes a change in RyR conformation and opens it. RyR allows Ca(2+) into cytosol.
- Ca(2+) binds TnC, which has 4 binding sites, and then causes contraction. Cross-bridge cycling and force generation occurs.
- SERCA sequesters Ca(2+) in the SR.
- Without Ca(2+) present, tropomyosin moves back over binding site and relaxation occurs.
(LO) Predict the pathologic mechanism of Muscular Dystrophy.
- Dystrophin, which connects sarcomere to sarcolemma and ECM, experiences a mutation.
- Dystrophin is a structural protein, thus, if it is damaged, the sarcomere doesn’t attach properly and does not enforce the stability of the muscle fiber. (?)
(LO) Define preload and afterload.
Distinguish between an isometric and isotonic contraction.
still not done-jk
Pre-load=before contraction/force STRETCHED.
After load=during the time that the muscle contraction/force is applied.
Isometric contraction: same length
- Force generated is insufficient to move weight placed on muscle (afterload).
- Can determine the length-tension relationship.
Isotonic contraction: same strength
- Force generated is sufficient to move load.
- Can determine the force-velocity relationship. As load increases, speed of lift decreases
(LO) Explain the length:force and force:velocity relationships and what they show in skeletal muscle.
Length-Tension: shown with Isometric contraction. Active force is measured.
-Shows that stretching a muscle to a certain point can increase force generated. Stretching a muscle allows cross bridging to form more easily. (preload changed, afterload is above max force)
Force-Velocity: shown with Isotonic contraction. Velocity of shortening is measured at a variety of afterloads.
-As load increases, the speed at which you lift decreases. Slower contraction gives more cross bridges time to form. (preload set, afterload changed)
(LO) Contrast a muscle twitch and tetanus.
Describe how more force can be generated in skeletal muscle.
-A muscle twitch is present each time a motor neuron fires. This generates a single muscle AP and a single generation of force. These are usually insufficient for movement.
-Tetanus can be achieved by recruiting more units (spatial summ.) or stimulating the same unit numerous times (temporal summ.)
(More force can be generated via isometric contraction, where stretching a muscle, to a point, can increase force generated).
________ muscle is smaller than ________ muscle and spindle shaped. NO sarcomeres! Actin and myosin held in place with ____________ filaments. No ________, has calponin and caldesmon instead. Has _________ connections, can have gap junctions, and no _-tubules.
Has SR and SERCA, but no _____ configuration.
________ muscle has short, _-shaped cells. Gap junctions at __________ disk. Can contract on their own. AP’s are longer. Has fewer _-tubules but they’re larger. Much more __________, fatigue resistant. Must have extracellular _______ to contract because DHPR and RyR aren’t close. Has more of these pumps (NCX and SERCA). Has a slightly ______ RMP of (-90mV)
Smooth. Skeletal. Intermediate. Troponin. Mechanical, T-tubules. Triad.
Cardiac, Y-shaped. Intercalated disk. T-tubules. Mitochondria! Calcium. Lower RMP
Identify the 3
ways to increase intracellular calcium in a smooth muscle cell.
All of the calcium for skeletal muscle comes from the __.
Whereas in smooth muscle only _____ comes from the SR.
It gets in by GQ mediated system, depolarization, and ligand gated channels.
SR
Some comes from SR, not all.
Contrast unitary and multi-unit smooth muscle.
\_\_\_\_\_\_\_ unit smooth muscle- GI, Bladder, Uterus. Cells linked by gap junctions. Little innervation. Some can generate own ATP. ALL contract together.
_____-unit smooth muscle -Iris, vas deferens
Each cell has its’ own innervation
Function as distinct muscle cells (like skeletal)
Single-unit (unitary)
Multi-unit
Once the actin-______ complex goes through the powerstroke, they remain latched together for quite some time. This complex has dephosphorylated light chains and has a very ___ affinity for ATP. Until the ATP comes along, the two remain latched. This is the ______ state of the smooth muscle myosin and saves the smooth muscle cell a great deal of ATP.
What tissues would this be necessary??
Myosin. LOW. Latch.
You would see this in vascular smooth muscle. Long isometric smooth muscle contraction.
Opposed to skeletal muscle, _______ muscle has short, y-shaped cells. Gap junctions at intercalated disk. __’s are longer. _______ t-tubules but fewer of them.
DHPR and RyR don’t close so there has to be extracellular _______ to contract. RMP is slightly _______ (-90mV) thus having more sarcolemma __2+ pumps
Cardiac . AP’s. Larger
Calcium. Lower. Ca2+
The absolute refractory period in ______ muscle is much larger than the others and prevents tetany. __2+ channels are open a long time. This is found in phase _ of 4.
…cardiac
Ca2+
2
(LO)
Skeletal muscles don’t need ECF __2+, so there’s NO effect on contraction.
______ muscle ALWAYS needs ECF __2+.
For hypercalcemia, the threshold becomes more ________. Making it less excitable so the strength of the contraction is _______.
For Hypocalcemia, threshold is more ________, making it _____ excitable and resulting in a _______ strength of contraction.
Ca2+.
Cardiac. Ca2+
Negative.
Stronger
Postive. More. Weaker
(LO) for ______ muscle, it’s almost impossible to over stretch! (Think of stomach)
For the same muscle, heavier the load, more phosphorylation of ______. Which makes contractions stronger and faster
For smooth muscle, almost impossible to overstretch! Think of the stomach.
Myosin
Compare fast cardiac cells and slow cardiac cells based on their action potentials. Use
the ionic currents present to explain the different phases.
….
