Muscle Structure and Function Biology 2121 Chapters 9-10
Introduction 1. Functions 2. Naming (321) Movement, Posture; Heat and Joints 2. Naming (321) Location; Shape (temporalis; deltoid) Size (gluteus maximus) Fiber Direction (abdominus rectus) Origins (bicep) Location of Attachment (sternocleidomastoid)
Major Muscle Groups Chest and Shoulder Group Abdominals Quadriceps and Hamstring Group
Histology of Muscle Tissue- Skeletal Muscle Voluntary Found in major muscle groups Striated Multinucleated Pushed to sides
Smooth Muscle Involuntary Found in digestive system organs, bladder, etc. Non-Striated Uni-nucleated Spindle-Shaped nuclei
Cardiac Muscle Involuntary Heart only Branching Fibers Uni-nucleated
Gross Anatomy 1. Whole muscle 2. Fascicles 3. Muscle Fiber Cells Tendon Epimysium 2. Fascicles Muscle fiber cells Perimysium 3. Muscle Fiber Cells Long and multi-nucleated Sarcolemma and sarcoplasma Endomysium
Attachments Tendons Aponeurosis Direct or Indirect Attachments
Microscopic Anatomy – Myofibrils 1. Contractile proteins 2. Sarcomeres Actin and myosin 3. Myofilaments Actin (thin) Myosin (thick)
Sarcomere 1. A ‘sarcomere’ 2. Structural Proteins Z to Z I-Band (light zone) A-Band (dark zone) 2. Structural Proteins Elastic filaments – Titan 3. Sliding Filament Model of Contraction Link
Sarcomere Contraction
Chemical Stimulation and Muscle Contractions 1. Stimulation and Neurotransmitters Acetylcholine 2. Neuromuscular Junction Nerve and Muscle Interface Synapse Sarcolemma
Neuromuscular Junction
Events at the Neuromuscular Junction 1. Nerve Impulse 2. Calcium ions – Axon Terminal of Nerve 3. Vesicle and release of ACh 4. ACh receptors and Acetylcholinesterase 5. Sodium-Potassium exchange 6. Action Potential formed
Neuromuscular Junction
Action Potential 1. Resting Membrane 2. Reversal of Charges -70 mV Na+ and K+ 2. Reversal of Charges Depolarization 3. Moves in one Direction
What Happens after the Action Potential is Formed?
Excitation and Contraction 1. Action Potential moves along the sarcolemma 2. Down the T-Tubule 3. Sarcoplasmic Reticulum and Release of Ca++ 4. Ca++ moves to the sarcomere
Formation of a Cross-Bridge 1. Ca++ interacts with troponin 2. Removes tropomyosin 3. Allows for Myosin Head Attachment 4. Formation of a cross- bridge
Cross-Bridge Cycling 1. Myosin heads attach forming cross- bridge 2. Working Stroke 3. ATP breaks cross- bridge 4. ATP hydrolysis 5. High-energy configuration – New Cross-bridge
ATP and Muscle Metabolism
ATP Production 1. Creatinine Phosphate 2. Anaerobic Respiration No oxygen “Lactic Acid Fermentation” 1 glucose molecule = 2 ATP Net 3. Aerobic Respiration Oxygen available 1 glucose molecule = 36 ATP Net Mitochondria of the Cell
Creatine Phosphate
Fermentation Glycolysis (2) Pyruvic acid molecules (3-C) Blood flow restricted during vigorous exercise (low oxygen) Lactic acid formed Anaerobic glycolysis
Aerobic Respiration