Bio 2420 2/21-2/27 Notes
Bio 2420 2/21-2/27 Notes BIOl 2420
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This 7 page Class Notes was uploaded by Aurora Moberly on Sunday February 28, 2016. The Class Notes belongs to BIOl 2420 at Southern Utah University taught by Dr. Paul Pillitteri in Winter 2016. Since its upload, it has received 49 views. For similar materials see Human Physiology in Biology at Southern Utah University.
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Date Created: 02/28/16
Test 3 3/4/16 Goal: 95 Skeletal Muscle System - Three layers of connective tissue in the muscle belly: - Epimycium: Wrapped around the entire muscle belly, outermost layer - Perimycium: Connective tissue that divides the muscle cells into bundles called fascicles - Endomycium (Basal Lamina): Layer of connective tissue wrapped around each individual muscle cell - All three layers of the connective tissue together are called the Parallel Elastic Component - Two functions of the Parallel Elastic Component: Protection, elasticity to produce force - Tendons: Attach muscle to bones, know as the Series Elastic Component, help to generate force when the muscle is stretched - Muscle Cell: - Sarcolemma: Muscle cell membrane - Skeletal muscle cells are multinucleate (one cell contains multiple nuclei) - Skeletal muscle cells are striated due to the arrangement of proteins in the cell - Muscle cells will run the entire length of the muscle - Looking down the barrel of the muscle cell there are many cylinders called myofibrils - Myofibrils: Bundles of proteins - Two main proteins: Myosin and Actin - Myosin is the thick protein/filament, appears as a dark patch on the myofibril - Actin is the thin protein/filament, appears as a light patch on the myofibril, overlaps with myosin - Creates a Z line/disk that attaches with other proteins - Sarcomere: Functional unit of skeletal muscle that extends from one Z line to the next Z line, contracts the muscle - All myofibrils sacromeres are lined up creating striation on the muscle cell, provides a unified and evenly distributed contraction - Myosin Filament: - Made up of many individual myosin molecules - Myosin molecule has a tail and two heads - Each head has two binding sites: Actin Binding Site (Attaches to the actin filament) and Myosin ATPase Site (Bind ATP and breaks it for energy use) - Once the head breaks ATP it holds onto ADP + P the head is now said to be energized - All the tails of the myosin filament point to the middle and the heads point to the ends - Actin Filament: - Actin molecules strung together in a helix formation - Each actin molecule has a binding site for myosin - Regulatory proteins on the helix: Tropomyosin and Troponin - Tropomyosin: Wraps itself around the actin filament so it covers over the binding sites so it can’t bind with the myosin - Troponin: Has three parts to it T IBinds to actin) T (Tinds to tropomyosin) T C (Binds calcium ions) - Troponin holds onto both the actin and tropomyosin but when calcium binds to TCit causes the troponin shape to change and pulls the tropomyosin off the myosin binding sites to allow myosin to bind to the actin - T-Tubules: Tube extensions of the cell membrane that dive deep into the cell, function is to spread the action potential deep down into the cell - Sarcoplasmic Reticulum (SR): Highly branched membranous sac, its function is to store and release calcium ions - The action potential from the T-Tubules sparks the SR to release the calcium ions - Contraction (Twitch) of a Muscle (Sliding Filament Mechanism): - Excitation-Coupling-Contraction-Relaxation - 1. Stimulus from motor neuron - 2. Action potential initiated and spreads down the sarcolemma - 3. Action potential travels down the T-tubules to hit the SR ++ - 4. SR releases Ca - 5. Ca++ binds to troponin - Troponin shifts tropomyosin to uncover the binding sites on actin - 6. Energized myosin head binds to actin (cross bridge formation) - 7. Myosin head pulls actin across myosin filament - Shortens sarcomere - Spends energy and releases ADP and P - 8. New ATP binds, cross bridge detaches and re-cocks - As long as calcium is present the steps 6-8 will be repeated to create the contraction - Relaxation: - 1. Ca++ is actively pumped back into SR ++ - 2. Ca is removed from troponin - 3. Tropomyosin moves to cover actin-binding sites - 4. Cross bridge cannot form, muscle relaxes to resting length - Muscle Properties: - All or None: In terms of a muscle twitch when the calcium is released from the SR there will be enough to bind with all the troponin and all the binding sites will be uncovered - Treppe: If we allow the muscle to relax and stimulate immediately after we can get a greater force because all of the calcium hasn’t been taken back up to the SR by the time the second stimulation has started - Twitch: -Latent Period: Time between action potential generated on the membrane and when the cell begins to generate force - Contraction Phase: Beginning of force generation to the peak of force generation - Relaxation Phase: Peak of the force generation till the muscle cell is completely relaxed - Motor Unit: How the nervous system is wired to your muscle cells - One muscle cell will only have one neuron innervating it - One neuron will innervate many muscle cells through branching - Motor unit is one motor neuron and all the cells that it innervates - Summation: - Motor Unit Summation: Recruits (stimulates) multiple motor units to create a contraction - Eventually the force stops increasing and you even out because you have all the motor units in that muscle stimulated - Twitch/Wave Summation: We stimulate the muscle and before it relaxes we stimulate it again, summing the twitches - Tetanus: No relaxation between twitches because the stimulus is coming so fast - Length-Tension Relationship: - The length of the muscle effects how much force it can produce - Force depends on how many cross bridges can be formed - As the muscle lengthens there is little overlap with the myosin and actin so there is less force produced; as the muscle length shortens there are more overlap, more crossbridges and more force produced - The force decreases when the muscle length is at it’s shortest because everything is too compact - Stretching the muscle causes the connective tissue (series elastic component) to stretch and produce force, called passive force - Active force is the actual contraction of the muscle - Muscle Actions: - Concentric: Shortens the muscle length, joint angle decreases, force production is greater than the resistance on the muscle - Eccentric: Lengthens the muscle while producing force, joint angle increases, force production is less than the resistance - There are less motor units recruited so it requires less energy - Since less motor units are required there is more weight distributed over less cells so they get more damaged than in concentric exercises - Isometric: Muscle produces force but the length of the muscle does not change, no change in joint angle, force production equals resistance - Asynchronous Recruitment: Nervous system switches out which motor units it is using so that those motor units don’t get tired out - Isotonic: Action where the force potential generated is the same throughout a muscles movement (Doesn’t happen in real life) - Is kinetic: The speed of the muscle movement over the range of the motion is constant (Doesn’t happen in real life) - Muscle Metabolism: - 1. Creatine Phosphate System (ATP-PC System) - Creatine’s function is to bind phosphates and goes through a chemical reaction with ADP to form ATP - Very fast process, doesn’t require oxygen - Limited in the amount of ATP it can produce - If you are exercising at maximal intensity you get about 5-10 sec of ATP from this system - 2. Anaerobic Glycolysis (Lactic-Acid System) - Glucose broken down to pyruvate that is broken down into lactic acid - Fast, no oxygen - Limited in the amount of ATP it can produce because it produces too much lactic acid that lowers the pH and prevents the enzymes from continuing the reaction - Maximal intensity exercise this system will provide 30-90sec - 3. Oxidative Metabolism - Glycolysis then Krebs then electron transport chain - Slow, oxygen required - Unlimited amounts of ATP produced - Fiber Types: - 1. Type I - Slow contraction speed, relies on oxidative metabolism - Smaller muscle cells, less force - Fatigue resistant - 2. Type II A - Fast, oxidative/glycolytic - Bigger, produces more force - Fatigues faster - 3. Type II B - Fast, glycolytic - Biggest, produces most force - Fatigue fast - A motor unit will always be made up of only one fiber type - Muscle will be composed of multiple fiber types - Fiber types can be changed to a degree to adapt to whatever type of stress you are placing on the muscles - Muscle Adaptation: - Hypertrophy: Increase in cell size due to using more force on that cell, cell size increases by increasing the amount of protein in the cell -Atrophy: Decrease in cell size due to not using it, cell size decreases by decreasing the amount of protein in the cell - Hyperplasia (Doesn’t occur in skeletal muscle): Increase in cell number - You are born with a certain number of muscle cells and that number doesn’t not increase Smooth Muscle - Characteristics: -Spindle shaped - Smaller than skeletal cells - One nuclei for each cell - Arranged in sheets that wrap around something (Ex. Blood vessels wrapped around blood cells) - Innervated by the autonomic nervous system - Structural Characteristics: - Actin/myosin but no myofibrils, not arranged in bundles - No z lines they have dense bodies that the actin attach to - No troponin - Tropmyosin but doesn’t block binding sites - Myosin head is inactive at rest - No T-tubules - Limited sarcoplasmic reticulum, releases calcium - Most of the calcium is coming from extracellular fluid - Autonomic Nervous System: - One neuron will innervate many cells - One cell can be innervated by more than one neuron (parasympathetic and sympathetic nervous system) - Varicosities: Bulges in branches of axon terminal that release the neurotransmitter - Contraction Process: - 1. Stimulus: Depends on the type of smooth muscle - 2. Action potential travels over the membrane - 3. Release of calcium from SR and opening of calcium channels on the cell membrane - Influx from outside of the cell, slow channels, slow contraction - 4. Calcium causes the activation of the myosin heads - Calcium and calmodulin bind to create calcium-calmodulin - Calcium-calmodulin activates myosin kinase - The active myosin kinase uses ATP to activate myosin head by phosophorlyating it - Relaxation of the cell comes from calcium being pumped out of the cell - Slow contraction and relaxation because of the slow release and uptake of calcium - Latch Phenomenon: Very slow crossbridge cycling - Uses few ATP and provides long sustained contractions - Types of Smooth Muscle (Stimulated in different ways): - Multi-Unit Smooth Muscle: Groups of cells innervated by certain neurons - Neurogenic: Tissue needs the nervous system to stimulate it - Found in large blood vessels and small airways in the lungs - Ciliary muscles and iris muscle - Base of hair follicles, gives you goosebumps - Single-Unit (Visceral) Smooth Muscle: - More common, walls of hollow organs, small blood vessels - Electrically linked by gap junctions - Contract as a single unit-functional syncytium - Myogenic-self excitable - Stimuli to influence calcium channels: Hormones, metabolic factors, stretch, ANS augments - Gradation of Contractions in Smooth Muscle: - Not all or none - Strength of contraction depends on how much calcium comes into the cell - Some channels always open-gives muscle tone - Different stimuli open/close membrane calcium channels - Action potential is not necessary for contraction for smooth muscle Endocrine System - Endocrine System: System of glands/organs that secrete chemical signals that influence other tissues - Controls activities that require duration - Hormones: Released into the blood to effect target tissues throughout the body - Three structural types: Peptides, amines, steroids - How hormones effect target tissues: - Receptors have to be specific to that hormone - Water soluble hormones are peptides and amines, have to bind to a receptor outside of the cell - Lipid soluble hormones are steroids, go right through the cell membrane into the cell and bind with a receptor inside of the cell - Steroids can affect the DNA - Hormone Regulation: - Secretion rate - Removal rate - Receptor numbers - Hormones can help regulate each other - Permissiveness: Allows another hormone to do it’s work - Synergism: Hormones work together to have a greater effect - Antagonism: Hormones have the opposite effect on each other or one hormone decreases the effect another hormone has - Important points about hormone function: - A single gland may produce multiple hormones - A single hormone may be secrete by more than one endocrine gland - A single hormone can have more than one type of target cell and therefore can have different effects - Same chemical messenger can be a hormone or neurotransmitter-source and mode of delivery - Some organs are completely endocrine while others have some endocrine functions - Endocrine Glands: - Pituitary Gland: Neuroendocrine organ, a way for the nervous system to control the endocrine system - Posterior Pituitary: Neurons attach from the hypothalamus and secrete oxytocin and vasopressin into the blood vessels - Anterior Pituitary: Blood supply connection between the hypothalamus and the anterior pituitary, hormones from the hypothalamus flow through the blood supply to the glandular organs of the pituitary gland (hypophysiotopic hormones) - 6 Hormones are released by the pituitary glands
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