Kine 1020 Exam - notes PDF

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Chapter 17 – Muscular Structure and Function  There are 3 main types of muscle: o Cardiac  The muscle within the heart  Striated  Involuntary o Smooth  Blood vessels  Non-striated  Involuntary o Skeletal Muscle  About 600, making up 40-60% of body weight,  Striated and not electrically coup...

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Chapter 17 – Muscular Structure and Function  There are 3 main types of muscle: o Cardiac  The muscle within the heart  Striated  Involuntary o Smooth  Blood vessels  Non-striated  Involuntary o Skeletal Muscle  About 600, making up 40-60% of body weight,  Striated and not electrically coupled  Voluntary  Skeletal Muscle Structure o Muscle is composed of a number of fasciculi that are bundled together. Within each fasciculi there are bundles of individual muscle fibres (cells) that number in the 10s. Muscle fibres in turn are mainly composed of myofibrils (contraction units) o Myofibrils contain the contractile proteins that generate force and are very numerous. o The # of fibres or cells varies between muscle and is related to the size of the muscle o Muscle –> Fascicle –> Muscle Fibre –> Myofibril o Myofibrils can be broken down to sarcomeres (basic contractile unit)  Muscle Protein  The proteins actin, tropomyosin, and troponin make the thin filament and myosin is the thick filament that is responsible for the light and dark areas o Actin  Globular protein (g-actin) that binds together in a chain to form microfilaments (F-actin)  In the muscle, 2 F-actins, will wind together into double helix form, together with the troponin and tropomyosin to form the thin filament  Actin is a structural protein that acts like scaffolding o Tropomyosin  long, double-stranded protein that weaves around the F-actin molecules in a double helical arrangement  During rest, the tropomyosin blocks that active sites on actin so that myosin cannot bind o Troponin  Globular protein that is made up of 3 sub units: Troponin C, I, & T)  Troponin-T binds the troponin to the tropomyosin

During muscle contraction, the calcium will bind to troponin-C and cause it to change shape and removes the tropomyosin exposing the active binding sites on actin  Troponin-I will inhibit this process during the rest stage o Myosin  has 2 Globular head regions and a rod-like tail region, and is the major protein in thick filament  the myosin forms the filament with the tail regions coming together in a thick rod like structure with the heads extending outwards  Each head has 2 reactive sites, one for binding to actin and other to bind to ATP o Intermediate Proteins  Titan  One of the largest proteins located from the Z-line and M-line  A single titan protein extends half the length of the sarcomere providing a scaffolding structure for the sarcomere  Allows for the force to transmit at the Z-line and contribute to the passive stiffness of the muscle  Desmin  Acts like scaffolding anchoring the Z-line to the Z-line of the next lateral sarcomere  Titan provides support lengthwise and Desmin would be more like the cord that binds all the sarcomere chains (myofibrils) together via the Z-lines  C-Protein  Located in the middle of each half A-band  Act like elastic bands binding the myosin tail region in bundles to form thick filaments Muscle Contraction o In order for there to be muscle contraction, there needs to be signal resulting in an actin-myosin interaction o Voluntary skeletal muscles are controlled by the Central Nervous System o The electrical signal travels down the motor neuron and causes the release of acetylcholine into the neuromuscular junction o This transmit an action potential that travels down the sarcolemma o The action potentials then travel inside the muscles via the T-tubules causing the voltage gated calcium channels on the sarcoplasmic reticulum to open and the release calcium ions from the sarcoplasmic reticulum into the sarcoplasm o The calcium binds to troponin C, causing troponin T to change conformation (shape) allowing tropomyosin to move and unblock the binding sites on actin and the actin-myosin binding and power stroke to occur o This actin-myosin binding requires: 1) Energy in the form of ATP 

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2) Calcium 3) The proper alignment of proteins to facilitate the necessary protein-protein interactions to occur o The head of the myosin or myosin ATPase (enzyme) needs to hydrolyze the ATP and the other myosin head needs to bind with actin o Steps for muscle contraction 1) Energization of myosin which results when ATP is hydrolyzed to ADP and Pi, this energizes the head of the myosin. i. *If this occurs in the absence of calcium nothing happens and is in continuous resting stage. ii. *If it occurs in the presence of calcium, then there is a binding of energized myosin to actin iii. When action potential travels down the sarcolemma, into the t tubule, it triggers the release of calcium which then binds to troponin 2) After the actin myosin binding there is a power stroke, wherein the myosin head bends and causes a shortening of sarcomere length 3) The myosin stays in a bent state until ATP binds to the myosin ATPase Muscle Fibre Contractile Activity In order for muscle to contract there has to be a stimulus that is followed by a response Also known as a twitch response 1) When a nerve stimulates a muscle, there is an action potential. This is called the Latent period. No muscle contraction or force production 2) Following the latent period, the contraction begins and a gradual increase in the force/tension produced in the muscle until the force production reaches the climax. This is called Contraction time 3) After the climax, the muscle tension will return to rest. This is called relaxation time The muscle twitch time is dependent upon the intrinsic properties of the muscle such as fibre type The contraction time is based by the type of myosin that is present and the relaxation time is dependent on the speed of calcium dissociation from troponin and reuptake back into the sarcoplasmic reticulum The speed of relaxation tends to mirror the twitch speed o Motor Unit Recruitment  Muscle fibre twitches do not occur singly, but in concert with other fibres  Consist of a single nerve with several muscle fibres is referred to as motor units  The more fibres that the nerve is connected to, the more tension it will produce  The muscle fibres that are connected to each nerve are similar in type  Slow twitch motor units  Slower contracting, and fatigue resistance

Produce less force, but can sustain the force production for a very long time  Fast twitch motor units  Type IIa o Fast contracting that have a moderate resistance to fatigue o Can produce more force than slow twitch, but cannot sustain the force production for as long before fatiguing  Type IIx o Also fast twitch, can produce more force that type IIa with the same number of muscle fibres o More easily fatigue than type IIa o Other Factors in Muscle Force Production Muscle force production is also dependent upon the frequency of stimulation, the length of the fibre at the onset of contraction, the muscle tension and bone structure  Frequency summation  When there is a single action potential there is single contraction that is followed by a relaxation  If there is 2 action potentials that occur prior to complete relaxation, the force generated by the 2 are summed up  The action potential can only occur during relaxation phase and will lead to staircase effect in force generated  Maximal force production is called tetanus  Fibre length  When the sarcomere is at their resting length, the potential for force production is the most optimal  If the sarcomere is longer or shorter, the tension that is produced with the contraction is less  Stretching the sarcomere there is less physical connection between the actin and myosin fibres, resulting in ales cross bridge  o Force Transmission (Series-Elastic Component) Ultimate strength of the muscle contraction is related to not only the force production created by the actin-myosin cross bridges, but also the transmission of the force through the length of the tissues o Parallel Elastic Component  Determined by the intermediate filaments  Force transmission along the length of the fibre o Series Elastic Component  Force transmission at the tendon and ligaments at the origins/insertions of the muscle o During the active contraction phase, the total tension produced and the active tension caused by the contraction (actin-myosin cross bridges) are the same o During relaxation phase the active tension will decrease 

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o Passive tension can increase to the point where it is actually the major contributor to the total tension achieved during certain actions Characterizing Muscle Contractions Muscle contractions can be characterized by the force or tension that is produced, or by other terms such as work or power Work(kgm)= force (kg) x distance (m) Power (kgm)= Work(kgm) / time (sec) can also be characterized by the type of contractions o Static or Isometric  Contractions wherein force is generated, but there is no movement or shortening of the muscle o Dynamic  Contractions that result in movements that are subdivided into 2 categories: Concentric (Shortening) and Eccentric (lengthening) o Force (Load) – Velocity Relationships  Velocity of the contraction is also related to the force generated  Concentric, the greater the external load, the slower the force would be  Eccentric, the greater the external load stretching the muscle, the greater the velocity of contraction will be  You can eccentrically move a weight faster than you can concentrically move it o Motor unit recruitment  Slow motor units are recruited at low levels of force production and the fast twitch, fast fatiguing fibres well be recruited as you approach maximal production  Slow twitch –> Fast twitch; Fatigue resistant –> Fast twitch, fast fatiguing o Characteristics of Muscle Function  Muscle power and endurance are intermediate combinations of force and velocity  There is no way to measure this

Chapter 18 – Energy Metabolism and Bioenergetics - The flow of energy in a biological system resulting in the ability to do work, produce heat, etc. - Energy can neither be created nor destroyed, but merely change forms - In the body chemical energy is converted to thermal (heat) and mechanical energy (work) through chemical reactions o Exergonic reactions  Energy releasing reactions o Endogenic reactions  Energy-consuming reactions; producing ATP  Enzyme Catalyzed Chemical Reactions

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o To control the rate of chemical reactions, the body uses enzymes. Enzymes can speed up or slow down the rate of chemical reactions  Catabolic  Breakdown of larger molecules into smaller molecules  Anabolic  Synthesis of larger molecules from smaller molecules Energy Systems Biological energy systems are broken down into 3 main types: phosphagen system, glycolysis and oxidative-phosphorylation. All 3 of these produce ATP at different capacities o Adenosine TriPhosphate (ATP)  Metabolic currency in biological tissues. Tissues need energy to be converted to ATP in order for it to be used by biological tissues to produce work.  Each molecule of ATP releases 7.3 kcal/mol energy  During muscle contractions, myosin ATPase hydrolyzes ATP so that energy is released as mechanical movement and heat  ATP levels stay consistent in biological tissues (muscle) even during fatigue intense exercises o ATP-PhosphoCreatine (PCr)  Activities that are extremely vigorous, the muscle uses the ATP that is immediately present in the muscle  Only enough ATP for 2-3 seconds worth of activity  The ATP-PCr can reform ATP and PCr and ADP very rapidly. It doesn’t use oxygen or produce lactic acid, but can only supply energy for another 6-8 seconds  Occurs in the sarcoplasm, allowing for the rapid replenishment of ATP  During muscle contractions, there is an increase in the concentration of ADP and hydrogen ions and decrease in ATP thus PCr is available Glycolysis o Anaerobic energy source that can provide energy for a longer period of time than ATP-PCr, but at a slower rate o Glycolysis converts glucose-6-phospahte into 2 molecules of pyruvate and a net of 2 ATP o Glycolysis occurs in the sarcoplasm, and the rate of glycolysis is limited by the activity of phosphofructokinase (PFK) converting fructose-6-phospahte to fructose-1,6-biphospahte o This means higher PFK activity allows for increased rate of glycolysis and lower PFK slows the rate of glycolysis o AMP and ADP are important controllers of PFK activity, in that high AMP or ADP increases PFK activity to increase ATP production o Pyruvate can be used in the lactic (anaerobic) or oxidative (aerobic) systems to produce additional energy

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o Difference between aerobic and anaerobic glycolysis is where the G6P comes from and the end fate of G6P Anaerobic Glycolysis o The conversion of muscle glycogen to G6P is catalyzed by glycogen phosphorylase, and the conversion of pyruvate to muscle lactate is catalyzed by lactate dehydrogenase o Anaerobic glycolysis to produce energy is related to amount of muscle glycogen available o Anaerobic glycolysis can only continue if there is sufficient NAD to from NADH Aerobic Glycolysis o Blood glucose is used to create G6P, catalyzed by hexokinase. Blood glucose is source substrate for aerobic glycolysis, but blood glucose is not limited in the same way as muscle glycogen is o Calcium and insulin are 2 factors that allow blood glucose to enter the muscle and enter aerobic glycolysis Lactic Acid System o When energy demands are high, glycolysis can create pyruvate faster than aerobic metabolism can use it o An accumulation of pyruvate will inhibit glycolysis and slow the rate of ATP production o The lactic acid system can temporarily reduce the pyruvate accumulation by converting some of the pyruvate to lactate which then can become lactic acid o Lactate can be transported to the liver and eventually be converted back to glucose Oxidative (Aerobic) Phosphorylation System o Can provide nearly all the energy used during longer term exercises as it can produce more ATP than ATP-PCr system o The oxidative system uses oxygen to fully break down the glucose molecule into CO2, H20 and energy o 38 of those ATP are achieved through oxidative metabolism Contribution of the Energy Systems o Contributions of different energy systems to the total energy expenditure is related to the intensity of the activity and the duration o Anaerobic systems to the total energy intake is greatest in high intensity-short duration activities and decreases with increased duration and lower intensity exercise

Chapter 19 – Musculoskeletal Health and Fitness - Healthy muscles allow individuals to move freely and to keep the body responsive and strong - Muscles are responsible for co-ordination activities - Musculoskeletal = MSK o Low Back Pain

o Leading cause of work absenteeism, with risk increasing by age o Sources of low back can be: fracture, osteoporosis, bulging discs or herniation, pinched nerves, muscle sprains, arthritis, inflammation or spondylolisthesis o Related to muscle flexibility and strength, abdominal obesity or low back strain or injury o Core muscles are important for maintaining back stability o Low muscle endurance can be seen in poor posture and thus poor spine alignment, exacerbating the inflexibility and the hyper flexibility of certain muscles o Occupation – Related MSK Disorders o Lead to impaired work performance and disability o Mechanical overload, repetition frequency, exposure time, and posture o Vibration and cold can contribute to injury as well o Carpel tunnel syndrome, back sprain, hernia, tendonitis or any joint pain o Osteoarthritis o 2 main forms:  Rheumatoid  Osteoarthritis  Most common form  Results from wearing down of the protective cartilage on the ends of bones  Symptoms: stiffness and pain in the joints that is worse after exercise  Knee and hip are most prevalent o Osteoporosis o Lower bone mineral density o Osteopenia is borderline osteoporosis o Prevalent in older and obese o Symptoms: pain in the bones and lower bac, height loss, night cramps o More common in women o Men tend be heavier and have a higher bone mineral density o Associated with diets lacking in calcium and vitamin D, hormone in balance, physical activity  Musculoskeletal (MSK) Disorder o Age, sex and family history are known to be non-modifiable risk factors for MSK disorders; 3 main types of disorders 1. Fatigue a. Transient and reversible functional and structural changes. Changes are temporary and can recover quickly 2. Functional limitations a. Injury or damage that impairs movement or activity. Takes days to recover 3. Chronic disability

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a. Ongoing injuries, can contribute to further MSK disorders Skeletal Muscle Fatigue – MSK Disorder The inability to maintain the required power output which is related to a decline in both force and velocity Loss in the capacity for developing force and/or velocity of muscle resulting from muscle activity under a demand load Inability to maintain the required power output which is related to a decline in force, velocity and power Fatigue and the recovery to normal may be related to several different types of factors that are both central and peripheral o Sites of Central Fatigue  Voluntary contractions  Common marker of central fatigue is the ratio of integrated electromyography (iEMG) to compound muscle activation potential (CMAP)  iEMG/CMAP decrease from 4-1 over time with eccentric contractions o Sites of Peripheral Fatigue  Normal contraction, the electrical signal travels down the motor neuron and causes the release of acetylcholine into the neuromuscular junction Neuromuscular junction o Very lil evidence that, Electrophysiological studies that electrical transmission at the neuromuscular junction may be responsible for fatigue Calcium overload hypothesis o This suggests that there are disturbances in calcium transport, impaired excitation of the contraction coupling, reduced calcium sensitivity of the myofibril processes and activation of calcium degradative process o Impacted with fatigue Metabolic system limitations o Fatigue can be associated with low substrate availability or metabolite accumulatio, resulting in altered ATP homeostasis o Shift in fuel used and the products that result from metabolism that ultimately contribute to fatigue o Reduced levels or low phosphocreatine levels can limit exercise performance o Anaerobic glycolysis can be limited when there are reduced glycogen concentrations  Increasing glycogen levels or carbohydrate loading can delay fatigue o Increased hydrogen ions from the anaerobic systems (breaking down of ATP with muscle contraction and lactic acid production) can lower pH can contribute to fatigue o Factors begin to limit anaerobic metabolism, there is a greater reliance on aerobic metabolism o Accumulation of reactive oxygen species from the electron transport chain can impair ATP production

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Actin myosin interactions o In order for actin myosin to detach, there needs to be ATP o During exercise there is a decrease of ATP and a build up of inorganic phosphate o Metabolic process is by far the major contributor to decreased pH as opposed to lactic acid o ADP accumulation also decreases myosin ATPase activity, and again may contribute to muscle fatigue Skeletal muscle protein breakdown o Structural damage that is reflected by increased skeletal muscle protein breakdown and its release in the blood Skeletal muscle structural changes o Transient structural changes in muscle that can be physically seen through muscle biopsy o Exercise is associated with disruptions in the normal z-line and sarcomere appearance that can be seen with microscopy o The number of fibres with myofibrillar disruptions is related to the change in force generating capacity Functional Limitation – MSK Disorder Described as the sensation of discomfort or pain in skeletal muscle occurs following unaccustomed movement, activity, or exercise Functional limitations can be caused by non-traumatic causes and traumatic causes o Clinical manifestation  As a result from fatigue there can be myoglobinemia or creatine kinase in...