2 Introduction Muscular tissue enables the body and its parts to move Movement caused by ability of muscle cells (called fibers) to shorten or contractMuscle cells shorten by converting chemical energy (obtained from food) into mechanical energy, which causes movementThree types of muscle tissue exist in body
4 Parts of a Skeletal muscle Origin—attachment to the bone that remains relatively stationary or fixed when movement at the joint occursInsertion—point of attachment to the bone that moves when a muscle contractsBody—main part of the muscle
5 Microscopic Structures Here’s the breakdown:Muscle >bundles of fibers>individual muscle fibers>sarcomeres>myofilamentsA sarcomere is a contractile unit of a muscle fiber. Fibers contain thick myofilaments (myosin) and thin myofilaments (actin).
7 Sliding Filament Theory Actin and myosin myofilaments slide past each other in a “ratchet” motionWhat two things are required for this contraction to occur?
8 Motor Unit – how we get muscles to move! Stimulation of a muscle happens by a nerve impulse .Each muscle has specific nerves that function to make it move!!!A motor neuron is the specialized nerve that transmits an impulse to a muscle, causing contractionNeuromuscular Junction is the exact spot where the nerve enters the muscle
10 Functions of the muscular system: MovementPostureHeat production
11 Movement Prime Mover Synergist Antagonist The main muscle responsible for a particular movementSynergistThe muscle(s) that assist the prime mover with a particular motionAntagonistThe muscle that works in opposition to the above
12 PostureTonic muscle contraction allows us to maintain good posture
13 Heat Production Requires ATP Contraction of muscle fibers produces heat
14 Muscle Fatigue – what causes it? Reduced strength of muscle contractionCaused by repeated muscle stimulation without adequate periods of restRepeated muscular contraction depletes cellular ATP storesContraction in the absence of adequate oxygen produces lactic acidWhat is meant by Oxygen Debt?
15 Motor UnitEach muscle of the body has a particular nerve or several nerves that “innervate” that muscle.The muscle and the nerve that supplies it’s innervation are known as a motor unit.
16 Types of skeletal muscle contractions TwitchTetanicIsotonicIsometric
18 Effects of Exercise on Skeletal Muscles Improves muscle toneImproves postureResults in more efficient heart and lung functioningReduces fatigue
19 Effects of Exercise on Skeletal Muscles Prolonged inactivity causes disuse, called atrophyRegular exercise increases muscle size, called hypertrophy
20 The Step Test – The question Why do breathing and heart rate remain elevated after exercise stops?
21 The Step Test – The answer Stored ATP is quickly depleted, and if oxygen supplies are not sufficient, muscle cells switch to energy conversion that does not require oxygen. However, this energy conversion produces lactic acid.The “oxygen debt” is paid when labored breathing and an increased heart rate are required to remove lactic acid and replace depleted energy reserves, even after exercise has ended.
22 Step Test – 2nd questionWhy would a “physically fit” person return to normal breathing and heart rate levels more quickly than an unfit person?
23 Step Test – 2nd answerincreased efficiency of the respiratory and circulatory systemsan increase in the number of blood vessels in musclesmore efficient delivery of oxygen and glucose to muscle fibersmore oxygen is available = the less “oxygen debt” there will be in the muscles.
24 Step Test – 3rd questionAerobic training also increases the number of mitochondria in muscle fibers.Why would this benefit the muscle contraction process?
25 Step Test – 3rd answerMitochondria are cellular organelles that convert glucose to ATPContraction of muscle cells requires ATPan increase in the number of mitochondria in a muscle cell increases the speed with which ATP is produced in the cell.Mitochondria = ATP
26 Body movements Figure 8-11 RotationAdduction and abductionPronation and supinationDorsiflexion and plantarflexion
27 Exercise – Learning activity Let’s say we want to strengthen the various muscles listed here….Biceps brachiiPectoralis majorGluteus maximusGastrocnemiusRectus abdominusWhat exercises should we do?
28 Exercise – Learning activity Let’s say we want to strengthen the various muscles listed here….Biceps brachii = arm curlsPectoralis major = push upsGluteus maximus = squatsGastrocnemius = foot flexion and extensionRectus abdominus = sit-ups
29 Muscle disorders Strain—injury from overexertion or trauma Cramps are painful muscle spasms (involuntary twitches)InfectionsMuscular dystrophyMyasthenia gravis
30 Review Function of the muscular system Structure of a muscle Types of muscle tissueHow a contraction occursTypes of contractionsHow exercise affects muscle