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10 Cards in this Set

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  • Back
What type of muscle fibers are used for sustained contractions?
Type 1 - slow twitch - red fibers
These have increased mitochondria and myoglobin for increased oxidative phospholrylation

Think "one slow, red ox"
Describe the physiological structure of a skeletal muscle.
Skeletal muscle is made up of bundles of muscle fibers. Each muscle fiber is a multi-nucleated cell that is made up of myofibrils. Myofibrils are made up of sarcomeres that contain actin and myosin.
What makes up a motor unit in skeletal muscle?
A single motor neuron and all the muscle fibers it controls.
How does troponin play a role in skeletal muscle contraction?
Troponin complex is a regulatory protein located on tropomyosin. Tropomyosin keeps the myosin-binding sites on actin covered until Ca2+ binds to troponin.
What is the most common dislocation of the humerus?
Anterior-inferior
What is the I band, H zone, A band and Z disk in a sarcomere?
The light band, (known as the I-band) is made up of thin filaments, whereas the dark band (known as the A-band) is made up of thick and thin filaments. The Z-line (also known as the Z-disk or Z-band) defines the lateral boundary of each sarcomeric unit. The H zone surrounds the M (middle) line and is only thick filaments. It's the A band that always stays the same length; the I band and H zone get smaller as the thick and thin filaments slide past each other in a contraction.

Remember: I for thIn (actIn); A for dArk and for Always staying the same length; H is for Heavy (myosin) and Z is at the END of the alphabet, so it's at the ENDs of the sarcomere.
What is the sarcolemma?
It is the membrane of a single muscle cell (muscle fiber). It is continuous within the fiber as T-tubules.
In skeletal muscle, how does an action potential release the Ca2+ from the sarcoplasmic reticulum?
A DHP receptor in the sarcolemma is mechanically attached to a ryanodine receptor in the sarcoplasmic reticulum. When an action potential comes, the DHP receptor changes conformation and allows the ryanodine receptor to move aside like a door, letting the Ca2+ come out.
What is the chain of events that occurs in a smooth muscle cell contraction?
Ca2+ enters cell from ECF and sarcoplasmic reticulum and binds to calmodulin.

Calmodulin activates MLCK (myosin light chain kinase).

MLCK phosphorylates the light chains in myosin heads allowing crossbridging to form with actin; thus creating muscle tension.
What's the difference between endochondral ossification and membranous ossification?
Endochondral: Longitudinal bones. Cartilaginous model of bone is first made by chondrocytes. Osteoclasts and osteoblasts later replace with woven bone and remodel to lamellar bone.

Membranous: Flat bones (skull, facial). Woven bone formed directly without cartilage. Later remodelled to lamellar bone.