3MyoglobinMyoglobin is a common protein, which has the ability to store oxygen in muscle cells. The myoglobin has a high level of red pigment, so the more myoglobin the meat has, the redder it will be. The terms “red meat” and “white meat” are actually an indicator for the level of myoglobin.
5MyoglobinThis protein is also the main reason that the red meat turns darker while you’re cooking it. During the heating process, iron atoms of the myoglobin lose electrons and they move up to a higher oxidation level. Thus, the meat turns from pinkish-red to brown.
22How muscle knows WHEN to contract Mechanism of contraction on a cellular level
23Motor UnitOne motor neuron and ALL the muscle cells that it stimulatesSpread throughout muscle
24Explanation - then see next slide! Stimulation of one motor unit results in weak contraction of ENTIRE muscleSince a motor unit is spread throughout the muscle & not clustered together, it stimulation will activate cells scattered throughout the entire muscleThis causes a weak contraction of the entire muscleMuscles requiring fine control have small motor units that only activate a few cells at a time.
29Transmission – know the steps Sarcolemma becomes temporarily permeable to sodium (Na+)Na+ ions rush into muscle cell which reverses electrical conditionsAction potential is caused which moves along sarcolemma and down T tubules deep into muscle fiberOnce initiated – action potential is unstoppable (all or none principle) resulting in full contraction of that particular muscle fiber (cell)Excitation-Contraction Coupling
30Safeguard When nerve stimulation stops: Ach is destroyed by acetylcholinesterase (AChE) to prevent continued contractionSubstances such as certain organophosphates found in pesticides and fertilizers destroy AChE causing convulsions
31End of stimulationK+ ions leaves cell rapidly to restore electrical balanceThen Na-K pump restores ions to original positions for relaxation of muscle fiber
36What causes the filaments to slide? Cross bridge attachment: in presence of Ca ions, high energy myosin cross bridge binds to actin binding sitePower Stroke: energy from ATP is used to bend cross bridge and pull actin toward center of sarcomere1% shortening for each power stroke
37Neuromuscular junction animation Focus Questions:What is the name of the stimulus that travels down the axon to the muscle fiber?An action potentialDoes the terminal (end) of the axon enter the muscle fiber?No. There is a gap between the two.Does acetylcholine enter the muscle fiber?No.What chemical does enter the muscle fiber, resulting in an action potential through the muscle fiber?Sodium
38Sliding Filament theory Boat = Myosin (thick filament)Oar = Myosin side armWater = Actin (thin filament)Life ring = Calcium
39Resting ATP is bound to myosin side arm. ATP cleaves into ADP + P (high energy)
40Step 1 Action potentialA nerve action potential releases acetylcholine into the synaptic cleft opening the Na+ channels.Action potential spreads across sarcolemma releasing Ca into sarcoplasma
41Step 2 Myosin-actin binding Ca binds to troponin.A shape change in troponin moves tropomyocin out of the way of actin binding site.Actin and myosin bind using energy from cleaved ATP.
42Step 3 Power StrokeSide arm pivots so myosin and actin slide by each other shortening the sarcomere.ADP and P released (low energy)
43Step 4 ATP Binding Actin-myosin release A different ATP molecule binds to active site.Actin released
44Step 5 ATP cleavage Return to high energy state Cycle will repeat if Ca still available.
45Think it overThe boat (myosin) does not move far in one cycle, can a muscle contraction occur with one cycle?NoIf a muscle is contracted what happens if a new molecule of ATP is not available?Muscle stays contracted- crampsWhy does rigor mortis occur? (Hint: What chemical is no longer available to the body?)ATP is not available to control Ca release so contractions are continuous 6-8 hours after death. Body relaxes hours as enzymes break down contractile structures.Myofilament Contraction
49Sliding Filament Animation Focus Questions:What chemical exposes the binding site for actin and myosin?CaWhat is the source of energy for a contraction?ATPWhat is the name of the step in which the actin filament is actively contracted?PowerstrokeWhat chemical must be present in order for the actin and myosin filaments to separate?
50Muscle contraction at the macroscopic level Place your fingers along the angle of your jaw just in front of your ear. Grit your teeth and fell what happens to the hardness of the masseter muscle.During muscle contraction the muscle becomes ________________________.
51With your thumb and little finger of one hand, span the opposite arm’s bicep’s from the elbow to as close to the shoulder as possible. Bend the arm and observe the change in the length of the muscle.During muscle contraction the muscle ___________________ in length.
52Wrap a string around your extended upper arm and determine the circumference. Clench your fist tightly and flex your arm to contract the muscle.During muscle contraction the diameter of the muscle _____________________.
55Developmental Aspects Progresses superior to inferior directionBaby can lift head before walkingProgresses proximal to distalBaby can move arm before grasping objectThis is due to the way that neural pathways are built in your brain.
56Men vs. women Women’s skeletal muscles make up 36 % of body weight Men’s is 42 % due to effects of testosteroneMuscle strength per unit mass is equal
57Building Muscle Mass Type of joint involved in motions Direction of muscle fibers (contained in fascicle)Anatomy of the muscleAngles of body partsIn order to work a muscle effectively & to minimize risk of injury, the above factors must be considered. Number of reps and amount of weight depends on purpose of exercise (building vs. toning).
58Aerobic vs. Anaerobic 3 main factors affect your respiration type: Your nutritionYour respiratory efficiencyYour cardiovascular fitnessIMPORTANT NOTE TO UNDERSTAND:The type of respiration that is happening depends on what is going on in a particular muscle at a particular time. You will have some muscles doing aerobic and others doing anaerobic AT THE SAME TIME!
60Aerobic RespirationIs the most efficient type of respiration – producing the most ATP per glucose moleculeGlucose + oxygen produce ATP + carbon dioxide + waterIt is slower and requires continuous delivery of oxygen & nutrients to the muscle
61Aerobic Respiration Duration of energy produced can be hours This type of energy production is used for activities that require endurance rather than powerJogging, marathon running, walking, etc
62Anaerobic Respiration Muscle uses up oxygen faster than circulatory and respiratory systems can deliver itGlucose gets converted to lactic acid in that muscleLactic acid will get converted to pyruvic acid and enter aerobic mechanism when oxygen becomes available
63Anaerobic Respiration Circulatory and respiratory system cannot deliver oxygen as fast as muscles are using it up.This leads to lactic acid buildup - when oxygen is again available – lactic acid is converted to pyruvic acid and oxidized
64Anaerobic Respiration For muscle to be restored to resting state:Oxygen stores must be replenishedLactic acid converted to pyruvic acidGlycogen stores replacedATP & creatine phosphate reserves replenishedLiver must reconvert the pyruvic acid produced to glucose or glycogenALL of these processes require oxygen
65Oxygen DebtThe amount of oxygen that must be taken into the body to provide for these restorative processesThe difference between amount of oxygen needed for totally aerobic respiration during muscle activity AND the amount that is actually used.All nonaerobic sources of ATP used during muscle activity contribute to this debt
66Oxygen DebtRepaid by rapid, deep breathing (hyperventilation) triggered by change in pH from lactic acid) after exertion is endedBreathing pure oxygen does not help recovery time – oxygen has to have time to get to the muscles that require it. There are limitations due to your circulatory and respiratory systems.
68Efficiency of Oxygen Use Athlete: ~10 % greater rate and efficiency of oxygen use than normal personMarathon runner: ~45 % greaterWorking your muscles, heart, lungs, etc out on a regular basis increases your efficiencyThings like smoking, poor nutrition, too much sugar, etc. decreases your efficiency
70Muscle Strain Commonly called a “pulled muscle” Is excessive stretching & possible tearing of muscle due to overuse/abuseInjured muscle becomes painful & inflamed (myositis)Treatment: adjacent joints are usually immobilized
71Muscle Strain Factors contributing Degree of stretch (more flexible at a joint the less likely you are to strain a muscle than someone who’s “tight”Speed of stretch
72Contusions A bruise or bleeding within a muscle Caused by impact to muscleWhen already injured muscle is repeatedly struck, a more serious condition, myositis ossificans, can develop
73Myositis OssificansInvolves formation of a calcium mass with the muscle over a period of 3-4 weeksAfter 6-7 weeks the mass usually begins to dissolve and is reabsorbed by the body.In rare cases, a bony lesion can remain in the m
75Muscle Cramps Moderate to severe muscle spasms that cause pain Possible causesElectrolyte imbalanceCa, Mg or K deficiencydehydration
76DOMS (Delayed Onset Muscle Soreness) Follows participation in a long or strenuous activitySoreness begins hours after activityInvolves multiple microscopic tears in muscle tissue & causes inflammation, pain, swelling & stiffness
77Muscle DisordersTorticollis – a twisting of the neck which causes rotation and tilting of the head to one side – caused by injury to one of the sternocleidomastoid musclesPulled groin muscles – Strain or stretching of adductor muscles (magnus, longus, brevis)Foot drop – paralysis of anterior muscles in lower leg – caused by injury to the peroneal nerve
79Muscle disordersShin splints – inflammation of the anterior muscle group of the lower leg (& the periosteum they pull on)– caused by trauma or strain – usually felt on the medial &/or anterior borders of the tibia
81Muscle DisordersCharley horse – officially a trauma induced tearing of muscles followed by bleeding into the tissues (NOT just a cramp)
82Halux valgus – permanent displacement of the great toe – caused by wearing pointy toed shoes
83Duchenne Muscular Dystrophy Page 194Genetic – affects primarily males – X linked traitDystrophin protein not produced correctly – leads to muscle fiber degeneration & atrophyProgresses from extremities upwardGenerally do not live beyond young adulthood
85Myasthenia gravis Probably autoimmune Shortage of neurotransmitter receptors in muscleMuscles not stimulated properly & grow progressively weakerDeath occurs when respiratory muscles fail to function
86Drooping of eyebrow & eyelid called Ptosis Myasthenia Gravis