Muscular System

• Which type of muscle is found only in the heart and is involuntary?

  Cardiac muscle
• Where is smooth muscle primarily located?

  Digestive organs and blood vessels
• What is the function of skeletal muscles?

  They move limbs by pulling bones via contraction
• What are two characteristics of skeletal muscles?

  Fatigue and strong contractions
• Describe the neuromuscular control process

  • Nerve impulse from the brain initiates an action potential
  • Impulse reaches the neuromuscular junction
  • Acetylcholine is released as a neurotransmitter
  • Acetylcholine moves over the synaptic cleft
  • Acetylcholine binds to muscle fiber receptors
  • Initiation of sliding filament theory (ST)
• What is the basic unit of skeletal muscle contraction called?

  Sarcomere
• What are agonist, antagonist, synergist, and fixator muscles?

  • Agonist: The muscle under the most tension, primarily responsible for movement
  • Antagonist: Controls the speed of the agonist
  • Synergist: Supports the agonist during movement
  • Fixator: Holds isometrically to anchor the position
• What are the three layers of connective tissue surrounding skeletal muscles?

  • Epimysium: Encircles the entire muscle
  • Perimysium: Surrounds fascicles within the muscle
  • Endomysium: Wraps around individual muscle fibers
• What is the role of myofibrils in muscle fibers?

  They are thinner sections that fill muscle fibers
• What does a motor neuron do?

  It sends signals to tell muscles to move
• What type of neuron sends signals to the brain when something is sensed?

  Sensory neuron
• What are the two types of muscle contraction mentioned?

  Concentric and eccentric contractions
• Compare the characteristics of Type 1, Type 2a, and Type 2x muscle fibers

  Type 1 (Slow Twitch):

  • Slow contraction speed
  • High oxygen utilization
  • Long duration
  • Suitable for endurance activities like marathons

  
  

  Type 2a (Fast Oxidative):

  • Medium contraction speed
  • Uses both oxygen and glucose
  • Moderate duration (<3 minutes)
  • Suitable for powerful speed activities like 400-800m runs

  
  

  Type 2x (Fast Glycolytic):

  • Fast contraction speed
  • Relies primarily on glucose
  • Short duration (<10 seconds)
  • Suitable for explosive activities like boxing and tennis shots
• Summarize the Sliding Filament Theory

  • A nerve impulse releases $Ca^{2+}$ ions from the sarcoplasmic reticulum
  • $Ca^{2+}$ binds to troponin, causing a conformational change
  • This change exposes myosin binding sites on actin
  • Myosin heads attach to actin, forming cross bridges
  • ATPase breaks down $ATP,$ providing energy for myosin to pull actin
  • Contraction occurs as actin slides over myosin
  • $Ca^{2+}$ ions are then removed from troponin
• What is an isometric contraction?

  A contraction where the muscle length remains fixed while tension is applied, such as in an abs plank
• What is an eccentric contraction?

  A contraction where the muscle lengthens while under tension, such as lowering quads during the downward phase of a squat
• What type of filament is actin?

  Thin filament
• What type of filament is myosin?

  Thick filament
• What occurs during a concentric contraction?

  The muscle shortens, pulling limbs closer together, as in a bicep curl