Muscular system

• What are the three main types of muscle tissue and their key characteristics?

  • Cardiac muscle: Heart only, involuntary, no fatigue
  • Smooth muscle: Digestive system, vessels, involuntary, Vasodilation
  • Skeletal muscle: Voluntary, moves limbs by pulling bones via contraction, fatigue, strong
• What initiates the nerve impulse in muscle contraction?

  Action potential sent from the brain
• Where does the nerve impulse reach to trigger muscle contraction?

  Neuromuscular junction
• What neurotransmitter is involved in muscle contraction at the neuromuscular junction?

  Acetylcholine
• What are the four main layers of connective tissue in a muscle and what do they hold?

  • Epimysium: Layer holding the whole muscle
  • Perimysium: Layer holding fascicles
  • Endomysium: Layer holding each fiber
  • Myofibril: Thinner section that fills a fiber
• What type of neuron sends signals from sensory receptors to the brain?

  Sensory neuron
• When do sensory neurons send signals to the brain?

  When something has been sensed
• What type of neuron sends signals from the brain to the muscles?

  Motor neuron
• What phrase describes the relationship between sensory input and motor output?

  Sensory Senses = Motors Move
• What is the function of motor neurons in muscle contraction?

  To send signals to tell the muscles to move
• What are the three types of skeletal muscle fibers and their key characteristics?

  • Type 1 (slow twitch):
  • $↓force$
  • $↑O2$
  • Long duration
  • Suitable for marathon running and slow long events
  • Type 2a (fast twitch):
  • Medium force
  • Uses both $O2$ and glucose
  • <3 minutes duration
  • Powerful speed
  • Suitable for 400-800m runs
  • Type 2x (fast twitch):
  • $↑force$
  • Uses glucose
  • <10 seconds duration
  • Explosive power
  • Suitable for boxing, golf swings, and tennis shots
• What ion is released from the sarcoplasmic reticulum during muscle contraction?

  Calcium $(Ca^+)$
• What protein does calcium bind to in the sliding filament theory?

  Troponin
• What happens to tropomyosin when calcium binds to troponin?

  Tropomyosin changes shape, exposing myosin binding sites on actin
• What occurs once myosin binding sites are exposed on actin?

  Myosin heads attach to actin, forming a cross bridge
• What enzymatic activity breaks down ATP during muscle contraction?

  ATPase activity
• What is the outcome of ATP being broken down by ATPase in muscle contraction?

  Contraction occurs
• What happens to calcium ions after muscle contraction?

  Calcium ions leave troponin
• What are the three main types of muscle contraction and their characteristics?

  • Isometric:
  • Fixed length
  • Under tension
  • Muscle does not change length
  • Example: Plank pose
  • Concentric:
  • Shortening contraction
  • Pulls limbs closer together
  • Example: Bicep curl
  • Eccentric:
  • Lengthening contraction
  • Lowering against gravity
  • Muscle is under tension while lengthening
  • Example: Quads during the downward phase of a squat
• What is the role of the antagonist in muscle contraction?

  Controlling the speed of the agonist
• Which muscle is considered the agonist?

  The muscle under the most tension
• What is the function of a synergist muscle?

  To support the agonist
• What is the role of a fixator muscle?

  To hold isometrically to anchor the position
• List the main muscles of the upper body.

  • Pectorals
  • Trapezius
  • Abdominals
  • Obliques
  • Rhomboids
  • Latissimus Dorsi
  • Erector Spinae
  • Transverse Abdominus
  • Deltoid
  • Biceps & Triceps
  • Wrist flexors/extensors
• List the main muscles of the lower body.

  • Iliopsoas
  • Glutes
  • Quads (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius)
  • Hamstrings (bicep femoris, semimembranosus, semitendinosus)
  • Anterior Tibialis
  • Soleus
  • Gastrocnemius
• What triggers muscle contraction according to the Sliding Filament Theory?

  • A nervous impulse arriving at the neuromuscular junction
• Where are calcium ions released from to initiate muscle contraction?

  From the sarcoplasmic reticulum.
• How do calcium ions allow myosin to attach to actin?

  • Calcium ions bind to troponin
  • Change the shape of tropomyosin
  • Allow myosin to form a cross bridge with actin
• What role does ATP breakdown play in muscle contraction?

  ATP breakdown releases energy that allows myosin to pull actin inwards, shortening the muscle (Power Stroke).
• What is the mechanism described for the myosin repeating its contraction?

  • Myosin detaches from actin
  • ATP provides energy
  • Myosin re-attaches to the next binding site
  • Repeats contraction
  • Similar to a ratchet mechanism
• What regulates muscle lengthening and relaxation after contraction?

  • The actin regulates muscle lengthening and relaxation
• What factors limit the duration of muscle contraction?

  Availability of ATP and calcium ions.