Week 8 & 9 - Lecture (Muscles) PDF

Anatomy & Physiology I MUSCULAR SYSTEM Muscular System System Level Video  Functions of Skeletal Muscle Muscular Move the Maintain System Body posture System Level Regulate...

Anatomy & Physiology I MUSCULAR SYSTEM Muscular System System Level Video  Functions of Skeletal Muscle Muscular Move the Maintain System Body posture System Level Regulate Protect eliminatio and n of support materials Produce heat  Muscle Characteristics Contractile proteins slide past each other Enables body Contractili movement and other ty muscle functions Skeletal System System Level Conductivit y An electrical signal passes along plasma membranes Involves voltage- Characteristics gated channels open Excitability sequentially React to stimuli Fibrocartilage (stretch or chemicals Triggers ion movement across the cell membrane Acetylcholine (ACT) is a chemical stimulus released by motor neurons  Muscle Characteristics (cont) Muscle returns to its original length Requires release Skeletal of tension in the connectin protein System Spring-like System Level Elasticity Extensibility Characteristics Muscle lengthening Stretching Muscular Connective System System Level Tissue Components Epimysium Perimysium Endomysium Dense irreg Dense irreg Areolar Connective Tissue conn tissue conn tissue connect Layers Covers the Covers each Cover each whole fascicle fiber muscle Muscular System System Level Muscle Anatomy  Skeletal Muscle… Muscular System 1. Highly vascular – vessels extend System Level through each of the layers of the muscle organ. 2. Innervated – neurons also extend through each layer NEARLY connecting to the muscle fiber. The gap is the Nerves and Blood NEUROMUSCULAR JUNCTION Vessels 3. Somatic Nerves (Peripheral Nervous System) 4. Voluntary Movement Muscular System System Level Multi-nucleated Cells Satellite cells serve as the stem cells for muscle tissue regeneration  Skeletal Muscle Contraction Three Components 1. Neuromuscular Junction 2. Excitation-Contraction Coupling 3. Sarcomere Crossbridge Cycling Muscular System System Level Video Muscular System System Level Neuromuscular Junction Phase 1 Phase 2 1. ACh released at the neuromuscular junction binds with receptors at the motor end plate stimulating the gated ion channels to open (remember the sodium/potassium pump). Sodium rushes in and potassium rushes out of the muscle fiber (cell) >> in  Phase 2 2. EPP initiates an Action Potential (depolarization/repolarization) Depolarization: When Na+ rushes in (ends with closure of the voltage gated sodium channel) Repolarization: K+ channel opens allowing K+ to leave the cell re-establighing the  Phase 2 3. Action Potential Triad is reached when calcium channels (voltage regulated) open allowing release of Ca++ into the cytosol of the muscle fiber (cell). Phase 3 Crossbridge Cycling: 1. Calcium binds with troponin causing it to change shape 2. Myosin heads attach at a binding site on actin (this forms the crossbridge) 3. When the myosin head moves it pulls the thin filament (power stroke) 4. ATP binds to the myosin head causing it to release 5. ATP splits off into ADP Muscular System System Level Video for Better Understa nding  What is the primary fuel of the cell? Muscular System System Level ATP – Adenosine Muscle Triphosphate Metabolism (Supplying Energy to Muscle Fibers)  Sources of ATP: Muscular Small amount already System exist in the cell. System Level ADP donates its P to Cel create ATP and AMP Creatine can also provide a phosphate to Muscle Metabolism l make ATP Provides 5-6 seconds of fuel (Supplying Energy to Oxygen not required Muscle Fibers)  Sources of ATP: Muscular System Fuel: Glucose (blood or System Level muscle stores) Breaks glucose down into two Glycolysi pyruvate molecules Yields 2 ATP s Provides 5-6 seconds of fuel (Metabolic Oxygen not required Muscle Pathway) Rapid Production but lesser Metabolism amount (short, intense (Supplying Energy to muscle use) Muscle Fibers)  What happens to the pyruvate is important…. Muscular If Oxygen If Oxygen Not System Present Present System Level Enters Converted to Enters mitochondria to lactate mitochondrion be broken down molecules Muscle Metabolism Returns to the Liver and Converted back (Supplying Energy to converted to to pyruvate Muscle Fibers) glucose  Sources of ATP: Muscular System Aerobic Process System Level Multiple Fuels: pyruvate, fatty acids, amino acids Cellular Slower but provides Respirati large quantities of ATP Muscle on Pyruvate: 17 ATP molecules; fatty acids: Metabolism 129 ATP molecules (Supplying Energy to Muscle Fibers)  Produce slower contractions Less powerful contractions SLO Can sustain contractions for longer periods W of time Trunk and lower muscles OXI Muscular DAT Highest resistance to fatigue System IVE System Level Faster contractions FAS More powerful T Lower limb muscles OXI High resistance to fatigue DAT IVE Muscle Fibers Powerful FAS Short duration T Low fatigue resistence GLY Upper limbs with more of these fibers COL YTIC  Three Phases of a Muscle Twitch LATENT PHASE CONTRACTION PHASE RELAXATION PHASE Occurs after the stimulus and Begins with the repetitive Begins with release of the before contraction Power Strokes crossbridges Provides time for all the events Muscle tension increases Ca++ returns to its storage in occurring within the Sarcomere shortens the sarcoplasmic reticulum sarcoplasmic reticulum Low fatigue resistence Begin of tension generation Upper limbs with more of No change in length of the these fibers muscle  Motor Unit Recruitment Muscular  Motor units vary in their sensitivity to stimulus System System Level  Increase in intensity (voltage) cause a greater number of motor units to contract  Maximum contraction occurs when all Muscle Fibers motor groups have been stimulated.  Muscle force is determined by the number motor units activated “All-or-None” Law?  Isometric Muscular Contraction System System Level Isotonic Contraction Muscle Fatigue Important Terms Muscle Atrophy Oxygen Debt Muscular System System Level Video