Contraction Cycle
These parts of the sarcomere are impacted by muscle contraction.
Z discs come closer together. H & I bands get smaller.
These are the three components of thin filaments.
Actin, troponin, & tropomyosin
______ carries nerve impulses towards the neuron.
Dendrites
This is what causes the hypertrophy of muscles.
There is an increased production of myofibrils, mitochondria, glycogen, myofilaments, SR, T tubules, etc. due to repetitive resistance training. This causes the diameter of fibers to increase, not the number of fibers to multiply.
Briefly explain sliding filament theory.
As myosin attaches to actin, they pull on the thin filament, making the muscle shorter & causing a muscle contraction. Myosin will then attach to another actin further down, pulling on the muscle more.
This is the role of the T tubules.
To carry action potentials
These cells help establish the blood-brain barrier.
Astrocytes
This is why skeletal muscle is multinucleated.
There are hundreds of myoblasts (precursor muscle cells) that fuse together to form a muscle fiber.
Disconnecting myosin from actin; reactivating myosin head; active transport of calcium back into SR
These fibers fatigue quickly, appear white, & have few mitochondria.
Fast fibers
This is the rarest type of neuron found in the retina & ear.
Bipolar neurons
What order do skeletal muscle fibers acquire energy for muscle contractions?
2. Creatine phosphate
3. Aerobic respiration (if oxygen is available)
4. Glycolysis (if oxygen is not available)
What is the entire contraction cycle in order?
1. Calcium released from SR
2. Calcium binds to troponin; tropomyosin shifts away
3. Cross-bridges form
4. Power stroke
5. Myosin head is released from actin by ATP
6. Myosin head is reenergized by ATP for the next cycle
This is contraction where the bones do not move.
Isometric contraction
What is grey matter?
Why is there a 2-millisecond delay during the latent phase?
Calcium ions are still being released from the SR & haven't yet bound to troponin.
What is the order of steps at the NMJ?
1. Action potential arrives
2. Acetylcholine is released into synaptic cleft
3. Acetylcholine diffuses across the synaptic cleft & binds onto motor end plate
4. Action potential generated in muscle fiber
5. Remaining ACh leaves cleft
6. Action potential covers the surface of the muscle fiber
7. Action potential arrives at the T tubules, starting the contraction cycle
This separates muscle into fascicles.
What forms myelin in the CNS versus PNS?
Oligodendrocytes=CNS
Schwann cells=PNS
Briefly describe motor unit recruitment.
There are tons of motor units per skeletal muscle. As the number of active motor units increases, the tension in the muscle increases. Peak tension occurs when all motor units are active in a muscle. Motor units can only contract in an all or none response. This helps to save energy & prevent jerky movements.