PHYL 301 EXAM 3 UPDATED ACTUAL QUESTIONS AND
CORRECT ANSWERS
Question:
1. motor unit
Answer:
- a single alpha motor neuron and all the muscle fibers it controls
- all fibers in a motor unit contract at the same time
- smaller motor units are for finer control of movement (Ex. motor neurons in the eye innervate 2-3 fibers)
- larger motor units are for larger movements (Ex. - muscle fibers in the leg may innervate up to 2,000
fibers)
- more motor units recruited = stronger contraction
- if a motor neuron is damaged, adjacent neurons may move over and bind to muscle fibers that are no
longer innervated - but only occurs if muscle continues to move
Question:
2. muscle tone
Answer:
- resting tension in a skeletal muscle due to some motor units being active
- no movement occurs from muscle tone b/c not enough tension is produced
- stabilizes the position of bones and joints and prevents injury
- the only time there is no resting muscle tone is during REM sleep
Question:
3. muscle hypertrophy vs. muscle atrophy
Answer:
- *hypertrophy* - enlargement of stimulated muscle, increased mitochondria, concentration of glycolytic
enzymes, glycogen reserves, and myofibrils
- individual myofibrils enlarge and contain a larger number of thick and thin filaments
- *atrophy* - reduction in the size, tone, and power of slow twitch (Type II, SO) muscle fibers, leads to
stiffness and soreness after a few days of disuse
- Fast twitch (Type IIbx) muscles do not atrophy with disuse always have some storage of glycogen
,Question:
4. 3 muscle fiber types and characteristics (diameter, myosin-ATPase activity, speed of contraction,
resistance to fatigue, oxidative phosphorylation capacity, enzymes for glycolysis, mitochondria,
capillaries, myoglobin, color, glycogen content, substrates used to generate ATP during contraction)
Answer:
1. *Fast twitch (Type IIbx) fibers* - large diameter due to densely packed myofibrils, quick and powerful
contraction, fatigue easily b/c powerful contractions use lots of ATP and have few mitochondria to meet
demand, mainly rely on glycolysis for energy
2. *Slow twitch oxidative (SO, Type I) fibers* - half diameter of Type IIbx, contract 3x slower, lots of
mitochondria so take longer to fatigue, more capillaries allow for greater blood flow and O■ delivery,
contain *myoglobin* (binds O■ and stores it in muscle fibers)
3. *Intermediate fast oxidative glycolytic (FOG, Type IIa) fibers* similar to Type IIbx, except more
mitochondria, more capillaries, and more resistant to fatigue
Question:
5. concentric vs. eccentric muscle contraction
Answer:
- two types of isotonic contractions (when muscle contracts and length changes)
- *concentric* - muscle shortens against load, moves in same direction as contraction (Ex. - pulling a chair
up)
- *eccentric* - muscle lengths against load, moves in the opposite direction of muscle contraction (Ex. -
lowering chair slowly)
Question:
6. 3 types of levers (joints)
, Answer:
- *1st class lever* - fulcrum is in the center, with resistance and effort on opposite sides (similar to a
seesaw), very few in the body
- Ex. - alanto-occipital joint, muscle pulls head backwards using joint as pivot point, and weight of head in
front is the resistance; efficient, but can only move weight of head
- *2nd class lever* - resistance is in the center, with fulcrum and effort on opposite sides, very few in the
body
- increases amount of force generated, but less distance and speed
- Ex. - metatarsalphalangeal joint in foot is the fulcrum, effort is triceps sura pulling up
- *3rd class lever* - effort is in the center, with resistance and fulcrum on opposite sides, most common
type
- increases speed and distance traveled, but requires greater force
- Ex. - elbow joint b/t the trochlea of the humerus and trochlear notch of ulna, resistance is the weight of
the forearm
Question:
7. arthritis vs. osteoarthritis vs. rheumatoid arthritis
Answer:
- *arthritis* - broad term for pain and inflammation of joints ('arth' = joint, 'itis' = inflammation)
- *osteoarthritis* - chronic inflammation of joints that results from overuse of joints and weak muscles,
causes pain and stiffness in joints
- inflammatory cells and chemicals erode and soften the articular cartilage of joints
- causes *crepitus* (crackling sounds due to friction b/t bone and cartilage) as cartilage breaks down
- may also cause bone spurs (osteophytes) to grow - sharp exposed bone tissue that causes pain
- *rheumatoid arthritis* - autoimmune disease in which the body's immune system mistakenly attacks the
joints
- antibodies attack the synovial membrane and enzymes in the synovial fluid degrade cartilage - causes
inflammation, swelling, and pain around joints
- over time, joints ossify, become unstable, and lose mobility
- inflammation softens tendons and may cause them to rupture, which leads to subluxation and dislocation
- treatment with anti-inflammatories (steroids, aspirin) - but aspirin can cause other problems (easy
bruising b/c anticoagulant, gastric ulcers in people with H. pylori, ringing in ears b/c interferes w/ auditory
nerve)
CORRECT ANSWERS
Question:
1. motor unit
Answer:
- a single alpha motor neuron and all the muscle fibers it controls
- all fibers in a motor unit contract at the same time
- smaller motor units are for finer control of movement (Ex. motor neurons in the eye innervate 2-3 fibers)
- larger motor units are for larger movements (Ex. - muscle fibers in the leg may innervate up to 2,000
fibers)
- more motor units recruited = stronger contraction
- if a motor neuron is damaged, adjacent neurons may move over and bind to muscle fibers that are no
longer innervated - but only occurs if muscle continues to move
Question:
2. muscle tone
Answer:
- resting tension in a skeletal muscle due to some motor units being active
- no movement occurs from muscle tone b/c not enough tension is produced
- stabilizes the position of bones and joints and prevents injury
- the only time there is no resting muscle tone is during REM sleep
Question:
3. muscle hypertrophy vs. muscle atrophy
Answer:
- *hypertrophy* - enlargement of stimulated muscle, increased mitochondria, concentration of glycolytic
enzymes, glycogen reserves, and myofibrils
- individual myofibrils enlarge and contain a larger number of thick and thin filaments
- *atrophy* - reduction in the size, tone, and power of slow twitch (Type II, SO) muscle fibers, leads to
stiffness and soreness after a few days of disuse
- Fast twitch (Type IIbx) muscles do not atrophy with disuse always have some storage of glycogen
,Question:
4. 3 muscle fiber types and characteristics (diameter, myosin-ATPase activity, speed of contraction,
resistance to fatigue, oxidative phosphorylation capacity, enzymes for glycolysis, mitochondria,
capillaries, myoglobin, color, glycogen content, substrates used to generate ATP during contraction)
Answer:
1. *Fast twitch (Type IIbx) fibers* - large diameter due to densely packed myofibrils, quick and powerful
contraction, fatigue easily b/c powerful contractions use lots of ATP and have few mitochondria to meet
demand, mainly rely on glycolysis for energy
2. *Slow twitch oxidative (SO, Type I) fibers* - half diameter of Type IIbx, contract 3x slower, lots of
mitochondria so take longer to fatigue, more capillaries allow for greater blood flow and O■ delivery,
contain *myoglobin* (binds O■ and stores it in muscle fibers)
3. *Intermediate fast oxidative glycolytic (FOG, Type IIa) fibers* similar to Type IIbx, except more
mitochondria, more capillaries, and more resistant to fatigue
Question:
5. concentric vs. eccentric muscle contraction
Answer:
- two types of isotonic contractions (when muscle contracts and length changes)
- *concentric* - muscle shortens against load, moves in same direction as contraction (Ex. - pulling a chair
up)
- *eccentric* - muscle lengths against load, moves in the opposite direction of muscle contraction (Ex. -
lowering chair slowly)
Question:
6. 3 types of levers (joints)
, Answer:
- *1st class lever* - fulcrum is in the center, with resistance and effort on opposite sides (similar to a
seesaw), very few in the body
- Ex. - alanto-occipital joint, muscle pulls head backwards using joint as pivot point, and weight of head in
front is the resistance; efficient, but can only move weight of head
- *2nd class lever* - resistance is in the center, with fulcrum and effort on opposite sides, very few in the
body
- increases amount of force generated, but less distance and speed
- Ex. - metatarsalphalangeal joint in foot is the fulcrum, effort is triceps sura pulling up
- *3rd class lever* - effort is in the center, with resistance and fulcrum on opposite sides, most common
type
- increases speed and distance traveled, but requires greater force
- Ex. - elbow joint b/t the trochlea of the humerus and trochlear notch of ulna, resistance is the weight of
the forearm
Question:
7. arthritis vs. osteoarthritis vs. rheumatoid arthritis
Answer:
- *arthritis* - broad term for pain and inflammation of joints ('arth' = joint, 'itis' = inflammation)
- *osteoarthritis* - chronic inflammation of joints that results from overuse of joints and weak muscles,
causes pain and stiffness in joints
- inflammatory cells and chemicals erode and soften the articular cartilage of joints
- causes *crepitus* (crackling sounds due to friction b/t bone and cartilage) as cartilage breaks down
- may also cause bone spurs (osteophytes) to grow - sharp exposed bone tissue that causes pain
- *rheumatoid arthritis* - autoimmune disease in which the body's immune system mistakenly attacks the
joints
- antibodies attack the synovial membrane and enzymes in the synovial fluid degrade cartilage - causes
inflammation, swelling, and pain around joints
- over time, joints ossify, become unstable, and lose mobility
- inflammation softens tendons and may cause them to rupture, which leads to subluxation and dislocation
- treatment with anti-inflammatories (steroids, aspirin) - but aspirin can cause other problems (easy
bruising b/c anticoagulant, gastric ulcers in people with H. pylori, ringing in ears b/c interferes w/ auditory
nerve)
