1. The Muscular System By Sam and Jess

2. Functions Movement & Circulation Support Posture & Balance Joint Stabilization Heat Production

3. Structure: Skeletal Responsible for voluntary motion Striated – Attached to bone via tendons – Ex. Pectorals, deltoids, quadriceps Many mitochondria/ cell Striations

4. Structure: Cardiac Responsible for rhythmic contractions of heart Involuntary Blend of smooth and striated muscles – Bound together by intercalated disks Most mitochondria/ cell Intercalated Disks Nucleus

5. Structure: Visceral Involuntary: controlled by nervous impulses or hormones Lines walls of hollow organs Cells spindle shaped: slow + steady contractions – Ex. Vasoconstriction, Vasodilatation

6. Three Types of Muscles (cellular level)

8. Muscle Anatomy

10. Layers of Muscle Myofibrils Muscle Fiber Fascicles held together by perimysium nerves and blood vessels run through Fascia

11. Muscle Fiber Anatomy

13. Muscle Fiber Many mitochondria Glycogen stored near sarcolemma – Food for energy Sarcoplasmic reticulum – Storehouse for Calcium ions

14. The Sarcomere I Band A Band H Band

15. Muscle Contraction Δvoltage caused by nerve impulse Calcium ions Interactions between calcium, troponin, myosin, and actin – ATP required Fibers pulled shorter: Contraction Video: http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapt er10/animation__breakdown_of_atp_and_cross- bridge_movement_during_muscle_contraction.h tmlhttp://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapt er10/animation__breakdown_of_atp_and_cross- bridge_movement_during_muscle_contraction.h tml

18. All-or-None Principle Strength of muscle contraction does not depend on strength of nerve signal Cell will contract if voltage threshold is achieved

19. Disease 1: Muscular Dystrophy Inability to produce dystrophin protein – Inherited or mutation Muscle weakness and loss of muscle tissue; learning disabilities; inability to walk (age 12); skeletal deformities Gene therapy? Corticosteroids; mobility aid; physical therapy; surgery

20. Disease 2: Myositis Autoimmune Inflamed or damaged muscle cells Weakness, swelling, pain Immunosuppressant, immunoglobin, physical therapy, steroids

21. Disease 3: Myasthenia Gravis Autoimmune Muscle weakness after activity Slow eye, facial, swallowing movements Immunosuppressant drugs, Thymectomy

22. Tetany Hypocalcaemia: low calcium How does this affect muscle contraction?? – Normal: calcium binds to sodium to block Δvoltage – Abnormal: less calcium results in lower threshold for Δvoltage Result  constant muscle contractions

23. Fatigue When muscles run out of energy No “ingredients” for cell respiration Lots of waste products – Lactic Acid – ADP Must pay oxygen debt

24. Muscle Research in Switzerland “Dirty” muscles mean weak muscles – Healthy cells must clean out waste products and malfunctioning components Autophagy – Cells with overactive mTORC1 protein (promotes muscle growth) cannot self-clean Solution: Inject Rapamycin to inhibit mTORC1 and allow cells to clean

25. Alcoholic Skeletal Myopathy Linked to Vitamin D deficiency Myopathy: weakness and wasting of muscle tissue 40%-60% of alcoholics experience myopathy Vitamin D deficiency is prevalent in alcoholics Vitamin D deficiency impairs mitochondrial function Shorter phosphocreatine recovery times=better mitochondrial function. Supplements of vitamin D improve recovery rates

26. Duchenne Muscular Dystrophy (DMD) Research DMD: fatal, genetic disease where muscles, including heart, progressively deteriorate. Genetic mutation: absence of vital protein  dystrophin Antisense oligonucleotides (AOs) Drug  Dantrolene

27. “A mouse hanging on a wire during a test of muscle strength. Mice with a mutant dystrophin gene, which have a muscular dystrophy-like disease, can only hang for about 20 seconds before they lose their grip and fall to the ground. An antisense oligonucleotide being developed to treat the disease in people only helps a little bit. But if the mice also receive the drug dantrolene (shown as the wire), they are stronger and can hang for 30 seconds or so…It also works in human cells and may help patients with Duchenne's muscular dystrophy.” [CREDIT: G. KENDALL/UCLA; IMAGES: M.C. MICELI, S. NELSON, E. MOKHONOVA, M. SPENCER]