exam 5 Flashcards
Describe the factors that lead to muscle fatigue.
Although the precise mechanisms that cause muscle fatigue are still not clear, several factors are thought to contribute. One is inadequate release of calcium ions from the SR, resulting in a decline of Ca2+ concentration in the sarcoplasm. Depletion of creatine phosphate also is associated with fatigue, but surprisingly, the ATP levels in fatigued muscle often are not much lower than those in resting muscle. Other factors that contribute to muscle fatigue include insufficient oxygen, depletion of glycogen and other nutrients, buildup of lactic acid and ADP, and failure of action potentials in the motor neuron to release enough acetylcholine.
Why would cardiac muscles have longer refractory periods than skeletal muscles. Choose the best answer?
a) to preserve the normal rhythm of the heart and prevent fatigue
b) the muscle types contain different contractile proteins
c) skeletal muscle is autorhythmic
d) skeletal muscles have prolonged calcium influx
e) cardiac muscle is not dependent on aerobic respiration to produce ATP
to preserve the normal rhythm of the heart and prevent fatigue
Motor unit recruitment occurs when there is a(n) [———-] in the number of active motor units within a skeletal muscle.
a) increase
b) decrease
c) no change
a) increase
Which microscopic structure is found only in the cardiac muscle tissue?
a) myosin
b) tropomyosin
c) sarcomeres
d) intercalated discs
e) striations
intercalated discs
Which type of muscle tissue contracts when excited by their own autorhythmic muscle fibers?
a) cardiac muscle
b) slow twitch oxidative skeletal muscle
c) multi-unit smooth muscle
d) fast twitch glycolytic skeletal muscle
cardiac muscle
How does a nerve impulse elicit a muscle action potential?
A nerve impulse reaches the synaptic end bulb and causes the release of acetylcholine, which diffuses across the synaptic cleft and binds to and activates acetylcholine receptors on the motor end plate. Binding of acetylcholine opens an ion channel in the acetylcholine receptors allowing Na+ to flow into the cell, which generates an action potential in the muscle cell.
What are the three ways that ATP can be produced in muscle fibers?
ATP can be produced from creatine phosphate, by anaerobic cellular respiration, and by aerobic cellular respiration.
Most muscles cross at least one
a) tendon
b) joint
c) bone
d) ligament
e) body plane
joint
The attachment of a muscle’s tendon to the stationary bone is called the _____; the attachment of the muscle’s other tendon to the movable bone is called the _____.
a) origin, action
b) insertion, action
c) origin, insertion
d) insertion, origin
origin, insertion
Briefly describe the three categories of levers based on the position of their fulcrum. Give an example of each type of lever and state whether the lever works at a mechanical advantage, disadvantage or both.
If the fulcrum is between the effort and the load it is a first class lever. Scissors are an example of a first class lever. A first class lever can produce either a mechanical advantage or disadvantage depending on whether the effort or load is closer to the fulcrum. If the load is between the fulcrum and the effort, it is a second class lever. A wheel barrow is an example of a second class lever. They operate at a mechanical advantage because the load is always closer to the fulcrum than the effort. If the effort is between the fulcrum and the load, it is a third class lever. Forceps are an example of a third class lever. They operate at a mechanical disadvantage because the effort is always closer to the fulcrum than the load.
The muscle that serves as the “prime mover” during a movement is called the
a) antagonist.
b) agonist.
c) synergist.
d) asynergist.
e) fixator.
agonist
This type of muscle works by stabilizing the origin of the agonist so that it can act more efficiently.
a) synergist
b) agonist
c) antagonist
d) fixator
e) secondary mover
fixator
Discuss the roles of agonists, antagonists, synergists, and fixators in movement.
The agonist (prime mover) contracts to cause a particular movement. The antagonist causes the opposite action, and so, must relax while the agonist contracts. Synergists prevent unwanted movements during an action or aid the agonist during the movement, while fixators stabilize the origin of the agonist. Both allow the agonist to work more efficiently.
Briefly describe four main benefits of stretching before exercising.
Stretching can improve physical performance by increasing joint flexibility allowing the joint to move through a greater range of motion. Stretching decreases risk of injury by decreasing resistance in various soft tissues so there is less of a chance of exceeding maximum tissue extensibility during activity. Stretching can reduce some of the muscle soreness that results after exercise. Stretching can help realign soft tissues to improve and maintain good posture.
Protrusion of an organ through a structure that normally contains it is referred to as a
hernia.
During inhalation, _____muscles contract to elevate the ribs. During forced exhalation, ______muscles contract to depress the ribs.
external intercostals; internal intercostals
