What are skeletal muscles composed of?
Skeletal muscle tissue plus connective tissues, nerves and blood vessels.
What are the functions of the skeletal muscle tissues?
Produce skeletal movement, maintain posture and body position, support soft tissues, guard entrances and exits, maintain body temperature, and provide nutrient reserves.
What are three types of muscle tissues?
Skeletal muscle tissue, cardiac muscle tissue, and smooth muscle tissue.
What is a neuromuscular junction? Where is it located?
Specialized intercellular connection where the nervous system controls each skeletal muscle fiber. Located midway along length of muscle fiber.
What does the strength of a skeletal muscle contraction depend on?
It depends on how many muscle fibers are active at any given moment.
What is the active mechanism for lengthening a muscle fiber? How does it return to its original length?
There is none. It returns to its original length through combination of gravity, contraction of opposing muscles, and elasticity in muscles stretched by contraction.
What does a muscle fiber do as it shortens?
Its exerts a pull, (tension) on connective tissue fibers attached to it.
What is and isometric contraction?
Muscle doesn't change in length, tension produced never exceeds the load. Doesn't bulge as much as an isotonic. It tightens.
The demand for ATP is enormous and mitochondrial ATP production rises to a maximum rate determined by availability of oxygen at...
peak levels of activity.
At peak exertion, mitochondrial activity can only provide 1/3 of ATP needed. How is the remainder produced?
Anaerobically by breaking down glucose and pyruvate.
The more ATP required, the more oxygen required. The amount of oxygen required to restore normal, pre-exertion conditions is called what?
What is polio and what does it cause?
A virus that attacks motor neurons in the spinal cord and brain. It causes muscular atrophy and paralysis.
When active in body tissues, what does tetanus do?
Release powerful toxin that suppresses the mechanism that inhibits motor neuron activity.
What is the result of tetanus? What is the mortality rate?
Result is powerful contraction of skeletal muscles throughout the body. 40-60% mortality rate.
What is botulism? What causes it?
It produces paralysis of skeletal muscles by preventing ACh release at neuromuscular junctions. Caused by consumption of contaminated food.
What is myasthenia gravis?
Loss of ACh receptors at neuromuscular junctions. Results in progressive muscular weakness.
What happens when skeletal muscles are deprived of nutrients and oxygen for an extended period?
They begin to deteriorate and within a few hours, the muscle fibers run out of ATP.
Shortly after death, what happens? Where does it begin?
Rigor mortis. Begins in smaller muscles of face, neck, and arms.
When a muscle becomes flaccid and muscle fibers become smaller and weaker, what is this called?
Is muscular atrophy reversible?
Initially, yes. But dying muscle fibers are not and cannot be replaced.
What is the origin of a muscle?
Where the fixed end attaches. Typically proximal to the insertion when in anatomical position.
What is an agonist?
Prime mover. Muscle whose contraction is chiefly responsible for producing movement.
What is a synergist?
Helps larger agonist work efficiently. Additional pull near insertion or stabilize point of origin.
What is flexion?
Movement in anterior-posterior plane that reduces the angle between articulating elements.