Chapter 6 pt2. Flashcards
(13 cards)
What are the steps in the development of skeletal muscle?
during development, myoblasts line upend-end and fuse to form myotubes, which produce myofibrils (made of myofilaments)
What are the differences between red and white skeletal muscle?
Some characteristics of red muscle (slow) are: high content in myoglobin, abundant mitochondria, high in oxidative enzymes, oxidative phosphorylation. Some characteristics of white muscle are low myoglobin, sparse mitochondria, low oxidative enzymes, anaerobic glycolysis.
What are the investments?
The investments of the skeletal muscle are the epimysium, endomysium, and perimysium.
What is a sarcomere? What are the bands and their locations—be sure you can identify them? What happens to the bands upon contraction?
Refer to slide 8 for the picture of a sarcomere. When contraction of the muscle occurs, the M line is extinguished, The A line will be constant, The Z discs will come closer, and the I band is narrower.
What are t-tubules and their function?
T-tubules are invaginations of the plasma membrane, which are present exclusively in striated muscle. Their role is to maintain the SR calcium store under the tight control of membrane depolarization via the voltage sensor channel DHPR
How are the thick filaments organized?
thick myofilaments are myosin II (200-300 myosins per filament). myofibril structure maintained by: titin (anchors thick filaments)
What events lead to the release of Ach?
Physiology. The neurotransmitter acetylcholine is released when an action potential travels down the axon of the motor neuron, resulting in altered permeability of the synaptic terminal and an influx of calcium into the neuron.
How is a neuromuscular junction organized?
every skeletal muscle has a motor and a sensory nerve fiber
motor fibers are myelinated but lose the myelin sheath when they penetrate the muscle CT
primary vs. secondary synaptic cleft
What does calcium have to do with contraction?
Calcium from the SR will bind to troponin on actin which in turn will activate tropomyosin. tropomyosin will display binding sites on actin for myosin which allows contraction.
What causes rigor mortis? Know the significance of ATP binding and hydrolysis to the myosin force cycle.
Rigor mortis–Deteriorating SR releases Ca+2 to enter cytosol–Ca+2 activates myosin-actin cross-bridging–Muscle contracts, but cannot relax. Muscle relaxation requires ATP, and ATP production is no longer produced after death–Fibers remain contracted until myofilaments begin to decay.
Know how the intercalated disk is organized.
intercalated disks have a transverse portion of desmosomes, fasciae adherents, and a lateral portion of gap junctions.
What are the granules in a cardiac fiber? What purpose do they serve?
Glycogen and atrial natriuretic peptide (ANP) from rat atrial muscle—the clear areas around the nucleus
What are dense bodies and what stain is used to visualize them?
iron hemotoxylin reveals dense bodies
