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26 Cards in this Set
- Front
- Back
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Which myosin heads can bind to actin?
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- only those within the zone of overlap
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Explain muscle fiber innervation
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-each muscle fiber is innervated by only one motor neuron
-a single motor neuron can innervate many muscle fibers - MOTOR UNIT= motor neuron + innervated muscle fibers |
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Describe motor unite recruitment
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- recruitment= progressive activation of additional motor units; increased recruitment caused increased force production
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What is the all or none principle?
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- all fibers in a motor unit will contract when the motor neuron innervating these fibers is stimulated
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What is graded-force production?
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- whole muscle is under graded activation since under voluntary conditions not all more units are activated at one time
- the graded muscle force is due to recruitment of motor units and summation |
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What determines contractile velocity?
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-the rate of ATP hydrolysis determines the rate of cross-bridge cycling which determines the contractile velocity
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What are the different fiber types found in humans?
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- Type I= slow twitch
- Type IIa= fast twitch - Type IIx= really fast fiber (rare) Hybrids of these fiber types |
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Describe Type I fibers?
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- high aerobic (oxidative) capacity (lots of mitochondria)
- small - slow contractile speed - low power -high endurance |
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Describe Type IIa fibers
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- high anaerobic (glycolytic) capacity (few mitochondria)
- large - fast contractile speed - high power -low endurance and fatigue quickly |
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What are the different ways muscle can adapt to exercise?
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- neural adaptations
- muscle growth (hypertrophy) - fiber type adaptations |
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What are the neural adaptations?
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- occur early in training
- increased motor unit recruitment leads to increased strength - increased motorneuron output leads to increased rate of torque development |
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What is muscle hypertrophy?
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- happens later in training
- addition of muscle mass via an increase in the size of muscle fibers= primary way to increase strength |
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What is the process of muscle hypertrophy?
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- mechanical stimulus (weightlift)
-activation of various protein signaling cascades (within minutes) - increase in gene activation (hours after exercise) - increase in protein synthesis and muscle growth (hours and days after exercise) |
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What can happen to muscle fiber type as a result of training?
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- they fiber types can begin to adapt and become more like the other type that is required for the activity
- even though Type I have an increase in power and contractile velocity with strength training their parameters don't come close to obtaining power or velocity of Type II fibers |
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What is sarcopenia?
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- the degenerative loss of skeletal muscle mass and strength with aging
- changes in fiber force and power due to reduced fiber size |
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What fiber type to the elderly tend to rely on heavily?
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- Type I
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How fast can you lose muscle mass due to inactivity?
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- 20% in one month
-the majority is lost within the first month |
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What happens to an inactive elderly patient who already has reduced muscle mass?
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- 16% strength loss in just 10 days
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What type of fiber shift happens as a result of bedrest? As a result of a spinal cord injury?
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- increase in mixed fibers; shift to faster fibers
- huge increase in Type IIx fibers (30-40%) |
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What is the connective tissue layers?
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- fascia= fibrous connective tissue that binds muscle into a functional unit
- all CT sheaths are continuous with each other and with tendon - force transferred through CT to tendon then to bone -consists predominantly of collagen and elastin |
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What are the functions of the CT layers?
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1. conduit for BV and nerves
2. maintain muscle shape 3. force distribution and transfer |
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What kind of metabolism do tendons have?
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- an active metabolism
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How are tendons organized?
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- into progressively smaller units held together by CT sheaths
- PARATENON= elastic sleeve, permits free movement of tendon against surrounding tissues - EPITENON= CT sheath around entire tendon -PERITENON= PARATENON + EPITENON - ENDOTENON= sheath surrounding fiber bundles (fascicles) -Collagen fiber -Collagen fibril |
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What are some functional properties of tendons?
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- tendons are elastic structures that deform in response to loading
-under voluntary conditions the load on the patellar tendon can be over 8000N or 1800lbs |
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How does chronic training affect tendons?
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- increased tendon cross-sectional area and stiffness
-increased stiffness allows the tendon to be loaded with more strain |
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What effect do drugs have on tendons?
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- Corticosteriods/Anabolic steroids= chronic use, high doses or direct injection into tendon can result in tendon degeneration and delayed healing; may decrease tendon strength and increase rupture risk
- Acetaminophen= alters tendon elasticity |
