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Exercise Physiology
The Study of how our bodies structures and functions are altered when we are exposed to acute bouts of exercise, a challenge to homeostasis
Exercise Physiologist
Someone who has a general understanding of the scientific basis underlying exercise induced physiological responses
Thre types of Muscle tissue
Skeletal
Cardiac
Smooth
Smooth muscle
Involuntary
Controlled my ANS
Located in the walls of blood vessels and throughout internal organs
Cardiac
Controlled by the ANS and endocrine systems
Skeletal
VOluntary muscle
COntrolled consciously by the somatic NS
Over 600 different skeletal muscles in the human body
Structure of a single muscle fiber
Transverse tubules
Sarcoplasmic reticulum
T-Tubules
Mitochondira
Myofibril
Sarcoplasm
Plasmalemma
Terminal cisternae
Plamalemma
(Cell membrane)
Fuses with tendon
Conducts AP
Maintains pH, transports nutrient
Satellite cells
Muscle growth, development
Response to injury, immobilization, training
Sarcoplasm
Cytoplasm of muscle cell
(Glycogen storage, myoglobin)
Transverse tubules
Extensions of plamalemma
Carry AP deep into muscle fiber
Sarcoplasmic reticulum
Calcium storage
Myofibrils
Muscle > Fasciculi > muscle fiber > myofibril
Hundreds to thousands per muscle fiber
Sarcomeres
Basic contractile element of skeletal muscle
Sarcomeres
A bands: Dark stripes
I Bands: Light striped
H-zone: Middle of A band
M- Line: Middle of H zone
Protein filaments
Actin (Thin filaments:
Myosin: Thick filaments
Myosin
Two intertwined filaments with globular heads
Titan
Stabilizer for myosin
Actin
Three proteins
Actin : Contians myosin binding site
Tropomyosin: Covers active site at rest
Troponin: Anchored to actin, moves tropomyosin
Motor units
Single motor neuron and all fibers it innervates
More operating motor units + more contractile force
Neuromuscular junction
Site of communication b/w neuron and muscle
Consists of synapse b/w motor neuron and muscle fiber
ACH
Acetycholine
Skeletal muscle contraction (Excitation contaction coupling)
AP starts
Ap arrives at axon terminal, releases ACH
ACH crosses synapse, binds to ACH receptors on plasmalemma
AP travels down plamalemma, T tubulues
Triggers CA release from SR
Ca enables actin myosin contraction
Role of CA in Muscle contraction
Ap arrives at SR from T tubule
Causes mass release of CA into sarcoplasm
Ca binds to troponin on thin filament
Troponin- Ca complex moves tropomyosin
Myosin binds to actin, contraction occurs
Sliding filament theory:
Process of actin myosin contraction
Contracted state
Myosin head pulls actin toward sarcomere center(Power stroke)
Filaments slide past each other
Sarcomeres, myofibril, muscle fiber all shortens
After power stroke ends: Myosin detaches friom active site
Myosin head rotates back to original position
Myosin attached to another active site farther down
Process continues until
Z disk reaches myosin filaments or AP stops
Energy for muscle contration
ATP
Binds to myosin head ( ATP > ADP + P+ energy)
Muscle relaxation
Ap ends, electrical stimulus of SR stops
Ca pumped back into SR
Muscle fiber types
Type I - 50% of all fibers in an average muscle
Peak tension in 110ms (Slow twitch)
Type II - Peak tension in 50 ms (fast twitch)
Type IIa
Type IIx
Type IIc
Slow twitch (Type I)
High aerobic (Oxidative) capacity and fatigue resistance
Low anaerbic (glycolytic) capactiy and motor unit strength
Slow contractile speed and myosin ATPase
Low SR development
Fast twitch (TypeII)
Moderate (Oxidative) capactiy and fatigue resistance
High anaerobic( GLycolytic) capacity and motor unit strength
Fast contractile speed and myosin ATPase
High SR development
FAst twitch ( Type IIx)
Low aerobic (oxidative) capactiy and fatigue resistance
High anaerobic (glycolytic) capactiy and motor unit strength
FAst contractile speed and myosin ATPase
High SR development
SIngle muscle fiber physiology
Peak power is different b.w muscle fiber types
All fiber types tend to reach their peak power at 20% peak force
Type I fibers during exercise
High aerobic endurance
Can maintain exercise for prolonged periods