Unit 1 Exam

Muscle Structure & Function

What is a muscle fiber?
→ A single muscle cell that contains myofibrils

What is a motor unit?
→ One motor neuron and all muscle fibers it innervates

What are myofibrils?
→ Contractile structures inside muscle fibers made of sarcomeres

What is myosin?
→ Thick filament with heads that bind actin and use ATP

What is actin?
→ Thin filament attached to Z-lines

What is a sarcomere?
→ Functional unit of muscle contraction between two Z-lines

What is the Z-line?
→ Boundary of a sarcomere where actin attaches

What is an action potential?
→ Electrical signal that triggers muscle contraction

Sliding Filament Theory

What initiates muscle contraction?
→ Action potential and calcium release

Role of calcium in contraction?
→ Exposes actin binding sites by moving tropomyosin

Role of ATP in contraction?
→ Powers cross-bridge cycling and detachment

What happens during the power stroke?
→ Myosin pulls actin toward the sarcomere center

What causes muscle relaxation?
→ Calcium pumped back into the sarcoplasmic reticulum

Neuromuscular Concepts

What is the all-or-none principle?
→ A muscle fiber contracts fully or not at all

What is recruitment?
→ Activation of additional motor units to increase force

Characteristics of Type I fibers?
→ Slow, aerobic, fatigue-resistant, endurance

Characteristics of Type IIa fibers?
→ Fast, moderate endurance and power

Characteristics of Type IIb (IIx) fibers?
→ Fastest, most powerful, fatigue quickly

Proprioceptors

Function of proprioceptors?
→ Sense body position and movement

Muscle spindle function?
→ Detects stretch and causes contraction

Golgi tendon organ function?
→ Detects tension and inhibits contraction

Biomechanics

What is biomechanics?
→ Study of forces and motion in the human body

Difference between proximal and distal?
→ Proximal = closer to trunk; distal = farther away

Axial skeleton includes?
→ Skull, spine, rib cage

Appendicular skeleton includes?
→ Arms, legs, girdles

Agonist muscle?
→ Prime mover

Antagonist muscle?
→ Opposes prime mover

Levers

First-class lever example?
→ Neck extension

Second-class lever example?
→ Calf raise

Third-class lever example?
→ Biceps curl

Muscle Actions

Concentric action?
→ Muscle shortens

Eccentric action?
→ Muscle lengthens under tension

Isometric action?
→ Muscle tension without movement

Negative work?
→ Force applied opposite the direction of movement

Strength & Safety

Strength definition?
→ Maximum force a muscle can produce

Strength-to-mass ratio?
→ Strength relative to body weight

Valsalva maneuver?
→ Breath holding to stabilize spine

When use a weightlifting belt?
→ Near-maximal or maximal lifts

Purpose of knee wraps?
→ Joint support and elastic assistance

Bioenergetics

Catabolism?
→ Breakdown of molecules to release energy

Anabolism?
→ Building molecules using energy

ATP?
→ Primary energy currency of the cell

Energy Systems

Phosphagen system duration?
→ 0–10 seconds

Primary fuel of phosphagen system?
→ ATP and phosphocreatine

End product of glycolysis?
→ Pyruvate

ATP from glucose vs glycogen?
→ Glucose = 2 ATP, Glycogen = 3 ATP

Two fates of pyruvate?
→ Oxidative system or lactate

What is the Cori Cycle?
→ Lactate → liver → glucose → muscle

Lactate & Oxygen

Lactate threshold?
→ Point where lactate accumulates rapidly

OBLA?
→ Fixed blood lactate (~4 mmol/L)

Oxygen deficit?
→ Oxygen shortfall at exercise start

EPOC?
→ Elevated oxygen use after exercise

Training Specificity

Interval training?
→ Alternating work and rest

HIIT?
→ Very high-intensity intervals

Combination training?
→ Trains multiple energy systems

📊 HIGH-YIELD TABLES (EXAM FAVORITES)

Muscle Fiber Types & Sports

Energy Systems by Intensity & Duration