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Chapter 6-Muscles
Four Major Functional Characteristics | contractility, excitability, extensibility, elasticity |
Contractility | the ability of skeletal muscle to shorten with force. |
Excitability | the capacity of skeletal muscle to respond to a stimulus. |
Extensibility | the ability to be stretched. |
Elasticity | ability to recoil to their original resting length after they have been stretched. |
Epimysium | A connective tissue sheath that surrounds skeletal muscle. |
Fascia | Is another connective tissue located outside the epimysium. Surrounds and separates muscles. |
Perimysium | Loose connective tissue that surrounds fasciculi (fascicle) |
Fasciculi (fascicle) | Numerous visible bundles that compose a muscle. |
The fasciculi are composed of single muscles cells called what? | fibers |
Each muscle fiber is a single cylindrical cell containing what? | several nuclei |
Endomysium | A connective tissue sheath that surrounds each fiber. |
Myofibrils | A threadlike structure that extends from one end of the fiber to the other. |
What is the cytoplasm of each fiber filled with? | Myofibrils |
Myofibrils consist of what 2 major kinds of protein fibers? | actin myofilaments, myosin myofilaments |
Actin Myofilaments | thin myofilaments. They resemble 2 minutes strands of pearls twisted together. |
Myosin Myofilaments | thick myofilaments. They resemble bundles of minute golf clubs. |
Sarcomeres | Are highly ordered units formed from actin and myosin myofilaments. Is the basic and structural and functional unity of the muscle. |
The arrangement of actin and myosin give what appearance? | a banded appearance |
I band | a light area on each side of the Z line. |
The A band | extends the length of the myosin. It is the darker central region in each sarcomere. |
H zone | a light area in the center of each sarcomere, which consists of only myosin. |
The myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called what? | M line |
Resting membrane potential | the charge difference across a membrane. |
Action potential | the brief reversal back of the charge. |
Motor neurons | are nerve cells that carry action potentials to skeletal muscle fibers. |
Each branch of axons that connects to the muscle forms what near the center of the cell? | neuromuscular junction or synapse |
Motor unit | A single motor neuron and all the skeletal muscle fibers it innervates. |
Neuromuscular junction | Is formed by an enlarged nerve terminal resting in an indentation of the muscle cell membrane |
Presynaptic terminal | The enlarged nerve terminal |
Synaptic cleft | The space between the presynaptic terminal and the muscle cell |
Postsynaptic terminal | The muscle fiber |
Each presynaptic terminal contains what? | Synaptic vesicles |
Acetylcholine | Secrete a neurotransmitter |
When an action potential reaches the nerve terminal it cause the synaptic vesicles to what? | Release acetylcholine into the synaptic cleft by exocytosis |