CBIO 2200 1nd Edition Exam 4 Study Guide Lectures 15 17 Lecture 15 October 23 Organization of the muscle fiber o Muscle fascicles muscle fiber cells myofibrils thick and thin filaments myofilaments Types of Mysium o Epimysium around the muscle o Periomysium around fascicles o Endomysium around individual muscle fibers cells Myoblasts stem cells that fuse to make each muscle fiber Satellite cells stem cells or undifferentiated myoblasts help repopulate muscle Sarcolemma plasma membrane of muscle Sarcoplasm cytoplasm of muscle cells Myofibrils long protein cords that occupy the sarcoplasm Glycogen storage form of glucose Myoglobin muscle form of hemoglobin red pigment that stores oxygen in muscle Sarcoplasmic Reticulum SR ER of muscles goes around all myofibrils Terminal cisternae dilations of the sarcoplasmic reticulum Transverse T tubules tubular in folding which penetrate through the cell and emerge on the other side Triad composed of the two terminal cisternae and one transverse tubule What is each myofibril made up of o A bundle of parallel protein microfilaments called myofilaments Contractile proteins do the work Regulatory proteins regulate muscle contraction Tropomyosin covers myosin binding sites on actin Troponin lays on top of tropomyosin have calcium binding sites when calcium binds the troponin tropomyosin complex roles away and reveals myosin binding sites Titin anchors myosin to Z discs and keeps muscles from overstretching Sarcomere the distance between two z discs What is the most famous kind of linking protein o Dysrophin Denervation atrophy muscle atrophies when a nerve signal is blocked from the muscle What constitutes a motor unit o One nerve fiber and all the muscle fibers innervated by it Neuromuscular junction where nerve meets the muscle Schwann cell myelin producing cells Lecture 16 October 28 Myasthenia Gravis o Autoimmune disease o Women ages 20 40 o Body produces antibodies that bind to ACh receptors and block ACh from binding to them o Insufficient muscle contraction Treatments for Myasthenia Gravis o Cholinesterase inhibitors allow ACh to not be broken down ACh may eventually be able to beat antibodies o Immunosuppressive agents suppresses production of antibodies o Thymus removal thymectomy removes ability to make T cells o Plasmapheresis remove blood take out plasma where the antibodies are and put it back Electrophysiology study of electrical activity of cells What is the mV for resting membrane potential o 90 Depolarization stimulated cell sodium channels open Repolarization sodium channels close and potassium channels open Hyperpolarizatoin potassium channels remain open after the potential reaches unstimulated level Major phases of contraction and relaxation o Excitation arrival of nerve signal ACh release o Excitation contraction coupling release of calcium links with troponin o Contraction hydrolyze of ATP release of ADP and inorganic phosphate power stroke ATP binds to myosin o Relaxation myosin releases actin nerve stimulation stops ACh release stops AChE breaks down ACh tropomyosin re blocks active site Rigor Mortis hardening of muscles and stiffening of body lasts about 48 hrs Lecture 17 October 30 What does the supply of ATP depend on o Oxygen o Organic energy sources Two main pathways of ATP synthesis o Anaerobic fermentation makes 2 ATP o Aerobic respiration makes 36 ATP Two characteristics of Cardiac muscle o Striated like skeletal muscle but myocytes cardiocytes are shorter and thicker o Intercalated discs In smooth muscle z discs are absent and replaced by dense bodies Myocytes have a fusiform shape Sarcoplasmic reticulum is scanty There are no T tubules Capable of mitosis and hyperplasia Some lack nerve supply while others receive autonomic fibers Involuntary excitation Types of paralysis o Spastic paralysis contraction without relaxation Tetanus lockjaw o Flaccid paralysis muscles are limp and cannot contract Botulism type of food poisoning Botox What do tension of muscle fibers depend on o The fiber s resting length at the time of stimulation o The frequency of stimulation Myogram recording of muscle contraction recording of the mechanical event 3 stages of a twitch o Latent period o Contraction phase o Relaxation phase Threshold a certain amount of tension has to develop in order for muscle to contract Strength of twitch depends on o Starting length o Muscles fatigue after continual use o Warmer muscles contract more strongly o Hydration level influences cross bridge formation o Increasing the frequency of stimulus increases tension output Isometric muscle contraction muscle develops tension but does not shorten no movement Isotonic muscle contraction muscle is changing length tension remains constant but there is movement