Lab Final Practical

• Epimysium: a sheath of fibrous elastic tissue surrounding a muscle.
• Perimysium: A layer of connective tissue surrounding the fascicle
• Fascicles: A group of skeletal muscle fibers
• Tendon: attaches muscle to bone
• Endomysium: A layer of connective tissue that surrounds the muscle fibers.
• Sarcolemma: cell membrane surrounding the muscle fiber that can conduct an action potential
• Sarcoplasmic Reticulum: A membrane-bound organelle that stores and releases calcium ions
• T Tubules: tube-like invaginations that transmit action potential to terminal cisternae
• Terminal Cisternae: bulges/widened areas of SR that acts as a calcium storage site
• Thick Filament: A protein filament that is made up of actin and myosin. Head of thick filament binds to thin filament
• Thin Filament: two intertwined actin filaments that are pulled apart by the action of the myosin
• Tropomyosin: A protein that binds to actin and regulates the length of the actin filament
• Troponin: on the ends of each tropomyosin
• Crossbridge: A protein complex that links the actin filaments of the myosin heads
• Motor neuron: stimulates muscle fiber to contract
• Motor unit: A motor neuron and the muscle fibers it innervates.
• Neuromuscular Junction: synapse between a motor neuron and a muscle fiber
• Synaptic Vesicles: within the synaptic end bulbs filled with ACh
• Synaptic Cleft: space between the synaptic end bulb and the sarcolemma
• Acetylcholine: released when nerve impulse reaches synaptic end bulb, binds to receptors in motor end plate, can generate action potential when enough is released
• Action potential is initiated by:

  -Skeletal muscle fiber needs to be stimulated by motor neuron or voltage stimulation

  -Leads to depolarization of the sarcolemma

  -If depolarization reaches a threshold --> action potential inineuronstiated
• Order of events for Excitation Contraction Coupling:

  -Action potential moves down sarcolemma to T tubules

  -Causes Ca++ ions to be released from terminal cisternae of SR

  -Ca++ ions bind to troponin

  -Troponin changes shape and pulls tropomyosin away from myosin binding sites on actin
• 4 Steps to the muscle contraction cycle:

  -ATP hydrolysis

  -Attachment of myosin head to actin to form crossbridge

  -Power Stroke

  -Detachment of myosin from actin
• Type I (Slow Oxidative): long distance, low fatigue rate
• Type IIa (Fast Oxidative-Glycolytic): moderate distance, moderate fatigue rate
• Type IIb (Fast Glycolytic): Short sprint, high intensity, quick fatigue rate
• Which fibers break down ATPase faster than others?

  Fast-twitch fibers
• Which muscle fibers use glycolysis?

  Fast-twitch muscle fibers (Type IIa & IIb)
• Which muscle fibers use aerobic respiration?

  Slow-twitch fibers (Type I)
• Concentric muscle contraction: muscle shortens and pulls bone towards itself
• Eccentric muscle contraction: muscle lengthens, muscle shortens
• Isometric muscle contraction: Muscle length does not change, but tension does.
• Frontalis: Raising eyebrows
• Masseter: Chewing
• Pectoralis major: adducts & internally rotates arm
• Rectus Abdominis: flexion of the abdomen
• transversus abdominis: stabilizes trunk
• Trapezius: elevates and retracts the scapula, and extends the arm
• Levator Scapulae: elevates the scapula and rotates it medially
• Deltoid: flex, abduct, extend arm