Lecture Notes Semester 2.docx

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York University
Kinesiology & Health Science
KINE 1020
Jennifer Kuk

Lecture Notes Semester 2Why is Strength Important Health relatedLowers risk of functional limitations o Prevents injury and infirmity o Is a predictor of advanced age disability o Reduced chronic low back painLowers risk of chronic diseases o Improved blood sugar control slowsprevents osteoporosis increases metabolic rateGood for psychological healthHelpful in emergencies Performance relatedIn sportMay help individuals to fill joboccupational requirements o Reduces risk of injuryincreases productivityDecreasing Muscle Strength with Aging Sarcopenia is the loss of muscle mass and strength due to the aging processIncreases functional limitationsInvolves apoptosisa decreased number of muscle fibresmassstrength Sarcopenia is a result of Programmed Cell Death which is characterized byDNA fragmentation DNA falls apart o Caused by a protein called DNA Fragmentation Factor DFF 40o Under normal circumstances DFF45 is present instead which inhibits DFF40 preventing the degradation it causesIf DFF45 is damagedaltered DFF40 can become active o Influenced by Caspase3protease that breaks down DFF45 more of thisactive DFF40more fragmentationNuclear condensation nucleus dissolvesoccurs in stages o Influenced by ApoptosisInducing Factor AIFStarts the condensation process disassembly of the nucleus at the ring stage o Leads to the disintegration of cells which are engulfed by macrophages but do not induce an inflammatory response therefore cannot be saved Potential causes of Sarcopenia still being identifiedMain idea apoptotic pathways involving caspases and AIF lead to cell deathsarcopenia o Caspasedependent process impacts initiation of apoptotic pathwaysInitiator caspases procaspases are inactive in muscle Caspase8 10 Caspase9 Caspase12which turn on Effector caspases active Caspase3 Caspase6 7which cause DNA fragmentation and protein breakdownProcaspases are activated by o IONIC IMBALANCE Increased calcium in muscle because of leaky sarcoplasmic reticulumTurns on caspase12 maybe 8 and 10 too o OXIDATIVE STRESS Increased levels of Reactive Oxygen Species ROS from mitochondria reduces mitochondrias functionalityCaused by the increased levels of calciumTurns on caspase8 10 o MITOCHONDRIAL DYSFUNCTION a decline in ATP levels and increase in oxygen free radicals causes mitochondrial membrane leakage leading to released cytochrome C which is regulated by Baxrelease and Bcl2release plugs the leak a good thing Cytochrome C has to bind with Apaf1 creating cytochrome cApaf1ATP or Apoptosomes which indicate cell deathTurns on caspase8 Bax Bcl2 CytC Apoptosomes o Caspaseindependent processMitochondrial dysfunctionAIF released from the leaky mitochondria results in nuclear condensation primarily and DNA fragmentation Loss of hormonal adaptations muscles cant grow if there are decreases in testosterone and growth hormone levelsLoss of neurological influences selective loss of type 2 motor units resulting in clusters of type 1 muscle fibres with age Impact of training strength and endurance on apoptotic pathways in the elderly Improves calcium handling reducing accumulationIncreases Bcl2Bax ratio to decrease the amount of cytochrome C leakageDecreases Apaf 1 decreasing the amount of apoptosomes that can be formedImproves mitochondrial functionReduces AIFMuscle Diseases Definitions and Types Muscle disease any disorder that affects the human muscle systemPrimary muscle disease the pathology originates with the muscle Secondary muscle diseases predominant the pathology originates in other systems o Nerveneuromuscular diseasedisorder ex Parkinsons disease o Bonejointo Inflammatoryo Immuneautoimmune muscle diseasedisorder ex Multiple Sclerosis Symptomsindications of muscle diseasesMuscle atrophy decreased size with muscle weaknessPain Tetany involuntary contractions spasms because of changing calcium levels o Generally in the larger muscle of the arms and legsTwitching single motor units firing due to loss of nerve cells typically close to the surface of the skinMuscular hypertension with increases in stiffness increased size in muscle due to increased amounts of fat there o A form of muscular dystrophy weaken the musculoskeletal system and hamper locomotionBiochemical parametersPrimary indicator of muscle diseaseMuscle weakness failure to develop an expected forceClassifications of muscle diseases associated with muscle weakness Upper motor neuron diseaseo Contrary to lower motor neuron disease you dont experience atrophy o Causes include tumors and spinal cord injury o Ex Stroke producing weakness on one side of the body the arm is typically flexed the leg is extended and the limbs have increased tone some movement may be preserved but the use of the hand is particularly limitedLower motor neuron diseaseflaccid limp muscle weakness o Can happen at the spinal cordmuscle wasting causes shrinkage and eventual death of neurons Paralysis is rapid and death comes within 3 years 1year in infantsEx amyotrophic lateral sclerosis ALS and Lou Gehrig diseaseNo known cause therefore no cure is available o Can happen at the peripheral nerves leaving the spinal cord going to the musclesdiseases called peripheral neuropathiespolyneuropathiesSymptoms usually begin in the hands and feet and progress towards the body also associated with sensory disturbancesThere is a degeneration of the axons Axons can regenerate but only at a rate of one or two mmday making injury recovery very slowAxonal types ofneuropathy are caused by damage to blood vesselsThere can also be a degeneration off the myelin sheathes covering of the axonsdemyelinating neuropathyMuscles rarely atrophy recovery can be rapidOther causes of peripheral neuropathy can include diabetes nerve trauma inherited factors chronic renal failureNeuromuscular NM disease o Associated with weakness and fatigability with exercise o Typically involve the generation of an endplate potential that is too low to propagate an action potential in the muscle fibreNot enough Ach or Ach receptors o May be acquired or inherited may be the result of autoimmune disorders congenital disorders or toxins
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