Muscles
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Motor units
A single neuron and the muscle it innervates
Reciprocal inhibition
When one muscle is contracting (agonist) it inhibits the other muscle (antagonist)
The diameter of the neuron determines what?
How fast or slow it is - larger = faster
How does a nerve talk to a muscle?
Acetylcholine - the neuro transmitter that stimulates skeletal muscles to contract
All or none
Motor units either give maximum response or no response at all
Skeletal
Creates movement in body parts, only muscles that can be under voluntary control
Cardiac
Make up the heart. Their contraction creates the force that propels the blood through the body
Smooth
Lines the walls of many internal organs and are responsible for pushing food through the digestive system and regulating blood pressure
What affects magnitude of force?
Size of motor unit - how many muscle fibers are innervates by the neuron (more force) Number of motor units involved - need more for heavier weight
Isotonic concentric
Muscle contraction - muscle is shortening, same force
Isotonic eccentric
Muscle contraction - muscle is lengthening
Isometric
Muscle contraction - muscle length remains the same
What is required to happen for the muscle to contract?
Cross bridges between actin and myosin contract muscle ATP is required to break the cross bridge
Hypertrophy
Growth of muscle fibers (Add actin and myosin)
Atrophy
Decay of muscle fibers (subtract actin and myosin)
What affects the force of a muscle contraction?
Size of the motor unit - larger unit has more muscle fibers = larger force Number of motor units involved
Myoglobin
Stores oxygen inside cells
Mitochondrial density
Uses oxygen (and glucose) to make energy (ATP)
Capillary density
Blood vessels that deliver oxygen and glucose
Aerobic
Slow but makes a lot of ATP
Anaerobic
Fast and makes little ATP
Type 1 muscle fibers
Color & Size: Red, small Force & Speed: Low force, slow speed Fatigue Resistance: Very high (endurance) Energy Usage: Aerobic (oxygen), efficient but slower Exercise Examples: Marathon running, cycling, long-distance swimming
Type 2a muscle fibers
Color & Size: Pink/red, medium Force & Speed: Moderate-high force, moderate-fast speed Fatigue Resistance: Moderate (lasts longer than IIx but not as long as Type I) Energy Usage: Mix of aerobic + anaerobic (flexible) Exercise Examples: Middle-distance running, soccer, basketball, repeated sprints
Type 2x muscle fibers
Color & Size: White, large Force & Speed: Very high force, very fast speed Fatigue Resistance: Very low (tires quickly) Energy Usage: Anaerobic (stored glucose, little oxygen use) Exercise Examples: Short sprints, powerlifting, jumping, explosive bursts