Lecture 6 Flashcards
Muscles (15 cards)
3 types of Muscle Tissue
Skeletal Muscle (voluntary)
Smooth Muscle (Involuntary)
Cardiac Muscle (involuntary)
Skeletal Muscles
Entire, Fasicle and Muscle Fibre
Entire muscle
– Surrounded by epimysium connective tissue
– Consists of many bundles (fasciculi)
Fascicle
– Surrounded by perimysium
– Consists of individual muscle cells (muscle fibres)
Muscle fibre (cell)
– Surrounded by endomysium
– Consists of myofibrils divided into the
contractile units of the muscles sarcomeres
Connective Tissue Layers
Epimysium
- Means on or over
Perimysium
- Means around or inclosing
Endomysium
- Means inside or within
Structure of Muscle Fibres
Sarcoplasm
– Cytoplasm of muscle cell
– Unique features: glycogen storage, oxygen binding myoglobin
Transverse tubules (T-tubules)
– Extensions of plasmalemma
– Carry action potential deep into muscle fibre
Sarcoplasmic reticulum (SR):
- Essential for muscular contraction
- Network of interconnecting tubular channels running parallel to the myofibril
Sarcomere
- Basic contractile element of skeletal muscle
- End to end for full myofibril length.
- Run z line to z line (Z line because it’s zaggy)
What are myofibrils?
Myofibrils are tiny fibers inside muscle cells
They contain myofilaments:
- Actin = thin filament
- Myosin = thick filament
Actin (Thin Filaments)
Composed of 3 proteins
Actin: Has the site where myosin binds
Tropomyosin: Covers the binding sites when muscle is at rest (the gate)
Troponin: Attached to actin, moves tropomyosin away to expose binding sites (Big brother)
Myosin (Thick Filaments)
Two intertwined filaments with globular heads
Heads stick out all around (360°)
Heads bind to actin to cause muscle contraction
Stabilized by a protein called titin
Sliding Filament Theory
Muscles shorten because myosin and actin filaments slide past each other — not because the filaments change length.
Myosin crossbridges attach to actin, pull (rotate), then detach — repeating this cycle to create movement.
Types of Muscle Contractions
Concentric Contraction
- Length of muscle shortens
- Muscle Force is greater than the resistance
Static or Isometric Contraction
- No change in muscle length
- Muscle Force is equal to the resistance
**Eccentric Contraction **
- Muscle Lengthens
- Muscle Force is less than the resistance
Muscle Fibre Types - Type 1
- Slow to contract
- Use oxygen → lots of mitochondria
- Don’t get tired easily (great for endurance)
- Thin with lots of blood supply
- Low power
- Red in colour (from myoglobin)
Muscle Fibre Types - Type IIa
- Red/white in colour
- Use both oxygen (aerobic) and no-oxygen (anaerobic) systems
- Faster and stronger than Type I
- Don’t tire as fast as Type IIb
- Good for middle-distance and team sports (e.g., 800m run, swimming)
Muscle Fibre Types - Type IIb
- Very fast and powerful
- Use stored carbs (no oxygen)
- Tire quickly
- Big in size
- White (low myoglobin)
- Great for short bursts (e.g., sprinting, lifting)
DOMS
Peaks 1 or 2 days after exercise
Eccentric contractions appear to be the initiator
Causes:
– Structural damage to the connective tissue of muscle cells
– Inflammatory reactions & swelling
Approxiametly how many skeletal muscles in the body?
650
