The Muscular System - Chapter 6
The Muscular System - Chapter 6
What does the muscle tissue consist of?
Muscle cells that are highly specialized for contraction.
What are skeletal muscles composed of?
Skeletal muscle tissue plus connective tissues, nerves and blood vessels.
How are skeletal muscles attached to bones?
Directly or indirectly.
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.
Each cell in skeletal muscle tissue is a single muscle fiber. True or False.
Each skeletal muscle fiber contains...
hundreds of nuclei.
What is a tendon made of?
Collagen and connective tissues.
Collagen fibers of connective tissue layers merge to form what?
Tendon or Aponeurosis.
What does a tendon attach to?
The muscle to a specific point on a bone.
What does and aponeurosis attach to?
Over a broad area that may involve more than one bone.
What is a motor neuron?
A nerve cell that excites muscles to contract.
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.
Muscle contraction is an active process that uses what as a power source?
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 the resting tension in a skeletal muscle?
The greater the muscle tone,
the greater the resting rate of metabolism.
What is an isotonic contraction?
Tension rises and the skeletal muscle's length changes. It lifts.
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 low in...
a resting skeletal muscle.
The demand for ATP increases at...
moderate levels of activity.
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.
What is the most likely way to contract tetanus?
Deep puncture wound, like from a nail.
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 does rigor mortis begin and end?
Begins 2-7 hours after death and ends after 1-6 days.
What is the enlargement of a stimulated muscle?
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 the insertion of a muscle?
The site where the movable end attaches to another structure.
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 antagonist?
Muscle whose action opposes that of a particular agonist.
What is flexion?
Movement in anterior-posterior plane that reduces the angle between articulating elements.
What is extension?
Increases in angle in articulating elements.
What is lateral flexion?
When vertebral column bends to the side.
What is dorsiflexion?
Flexion at the ankle joint and elevation of sole. (dig your heel)
What is plantar flexion?
Extends the ankle joint and elevates the heel (stand on tiptoe)
What is abduction?
Movement away from longitudinal axis of body.
What is adduction?
Movement toward longitudinal axis of body.
What is circumduction?
Moving your arm as if to draw a circle on the wall.
What is pronation?
Turns wrist and hand from palm facing front to palm facing back.
What is supination?
Palm is turned from palm facing back to palm facing front.
Moving a part of the body anteriorly in the horizontal plane is called?
Twisting motion of the foot that turns the sole inward...
Twisting motion of the foot turning the sole outward...
What occurs when a structure moves in an inferior or superior direction?
Depression and elevation.