AP 1 (9-2)
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What is the function of actin in thin myofilaments?
- Contractile proteins.
- Each G actin has a binding site for myosin.
What is the function of Tropomyosin in thin myofilaments?
- Regulatory protein
- Blocks binding sites on actin to myosin.
What is the function of troponin in thin myofilaments?
- Regulatory protein
- Complex of three proteins
- Attaches to actin
- Attaches to tropmyosin
- Binds calcium reversibly
- Calcium binding to troponin regulates skeletal muscle contraction
- Two interwined subunits
- Each with a long tail and fat, protruding head
- Each head has an actin-binding site and an ATPase site
- Myosin molecules bind to each other.
- Anchored by protein filaments by M line.
What is Titin?
- Elastic protein, runs through the thick filaments.
- Anchors thick filaments between M-Line and Z-line
- Provides structural supports and elasticity
What is the Sarcoplasmic reticulum and what is its function?
- Endoplasmic reticulum which lies below the sarcolemma.
- Stores calcium ions.
What are Transverse tubules?
Invaginations of the sarcolemma that lie below two cisternae of the sarcoplasmic reticulum and is open to the outside of the muscle fiber.
Each skeletal muscle cell is connected to a neuron called a _____.
Somatic motor neuron
What must happed for contraction of a muscle cell to occur?
a nerve impulse must pass along the motor neuron to each skeletal muscle cell and stimulate it.
What is a neuromuscular junction?
Connection point between the neuron and the muscle cell.
What is a motor end plate?
Depressed area of a folded, specialized portion of the muscle cell membrane. (beneath the neuron ending)
What does a nerve impulse cause in a neuromuscular junction?
Acetylcholine to cross the neuromuscular junction and stimulate the muscle cell to contract.
What is a motor unit?
One neuron and all of the muscle cells it innervates.
Small motor units cause what?
small weak precise movements (eye muscles)
Large motor units cause what?
Large powerful movements (leg muscles)
Whenever a _____ fires, all muscle cells in its motor unit contract.
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