Muscular System

1
Muscular System
2
Skeletal Muscle Tissue
3
Functions of the Muscular System

• constrict organs and vessels
• pump blood
• cause respiration
• produce body movement
• maintain posture
• produce movements involved in communication
• produce body heat

4
Basic Structure of Skeletal Muscle

• Each skeletal muscle fiber single cell
• containing numerous myofibrils
• Myofibrils are composed of actin and myosin
• Sarcomeres are joined end to end to form
  myofibrils
• Muscle fibers are organized into fasciculi
• Fasciculi groups Sarcolemma
• Fasciculi are organized into muscles by
  associated connective tissue

5
Anatomy of Skeletal Muscle

• Muscle
• Sarcolemma
• Fasciculi
• Muscle Fibers
• Z Line (Sarcomere distance between two Z lines)
• H Band (Lengthens during contraction)
• I Band (Shortens during Contraction)
• Thick and thin filaments

Listed from largest to smallest
6
(No Transcript)
7
Muscles and Energy

• Muscles need lots of ATP
• energy from ATP is used to
• reset the myosin crossbridge head
• release the actin filament
• muscles making ATP
• Breaks down creatine phosphate
• adding the phosphate to ADP to create ATP
• Carries out aerobic respiration
• Glucose is broken down in the presence of oxygen
  to produce ATP
• How much ATP????
• Carries out anaerobic respiration (Oxygen Debt)
• glucose is broken down to lactic acid
• ATP is formed
• Oxygen debt occurs after 30 seconds
• How much ATP????

8
Muscle Fibers

• Muscles have a mixture of two basic types of
  fibers
• fast twitch and slow twitch
• Fast-twitch fibers
• develop greater forces
• contract faster
• greater anaerobic capacity
• Slow-twitch fibers
• develop force slowly
• maintain contractions longer
• higher aerobic capacity

9
Thick and Thin Filaments

• thick and thin filaments do the actual work of a
  muscle
• Thick filaments are made of a protein called
  myosin
• shaft of myosin molecules arranged in a cylinder
• Thin filaments are made of actin
• thin filaments look like two strands of pearls
  twisted around each other

10
Contraction

• During contraction
• myosin thick filaments grab on to the actin thin
  filaments
• forming crossbridges
• thick filaments pull the thin filaments past
  them
• making the sarcomere shorter
• the signal for contraction is synchronized over
  the entire fiber
• all of the myofibrils that make up the sarcomere
  shorten simultaneously
• two structures in each thin filament
• long, rod-like protein called tropomyosin
• shorter, bead-like protein complex called
  troponin
• Troponin and tropomyosin are the molecular
  switches
• control the interaction of actin and myosin
  during contraction

11
(No Transcript)
12
Role of T-Tubules

• Action Potential
• Brought to entire sarcolemma almost
  instantaneously
• Via T-Tubules
• T-Tubules transmit message to Sarcoplasmic
  Reticulum
• Sarcoplasmic Reticulum transfers Ca ions to
  bind with troponin enzyme complex