1 The Muscular System Chapter 8

2 Three Kinds of Muscle Tissue 1. Smooth > Involuntary > Organ & Vessels 2. Cardiac > Involuntary > Heart 3. Skeletal > Voluntary > Stimulated to Contract by the Nervous System

3 Skeletal Muscle Attaches to bones & produces movement at joints Attaches to bones & produces movement at joints Make up the largest amount of muscle tissue in the body Make up the largest amount of muscle tissue in the body Makes up about 40% of total body weight Makes up about 40% of total body weight The body is composed of almost 700 individual skeletal muscles The body is composed of almost 700 individual skeletal muscles Usually act in groups to execute a body movement Usually act in groups to execute a body movement

4 Three Primary Functions of Skeletal Muscle 1. M ovement - of the skeleton 2. M aintenance of posture – a steady partial contraction of muscle called MUSCLE TONE keeps the body in position 3. G enerate heat – a natural by- product of muscle cell metabolism

5 Muscle Contraction Two proteins called ACTIN & MYOSIN are contained in muscle fiber Two proteins called ACTIN & MYOSIN are contained in muscle fiber They “latch on” to each other, and with the energy of ATP, slide together to cause the muscle fibers to contract They “latch on” to each other, and with the energy of ATP, slide together to cause the muscle fibers to contract

6 Types of Muscle Contraction Muscle Tone – partially contracted state Muscle Tone – partially contracted state Isotonic – muscle tone or tension remains the same, but the muscle shortens to produce movement – Ex: lifting weights, walking, running Isotonic – muscle tone or tension remains the same, but the muscle shortens to produce movement – Ex: lifting weights, walking, running Isometric – no change in muscle length, but there is a tremendous increase in muscle tension – Ex: pushing against an immovable object or force Isometric – no change in muscle length, but there is a tremendous increase in muscle tension – Ex: pushing against an immovable object or force ** Most movements involve a combination of isotonic & isometric contractions

7 Attachments of Skeletal Muscles Tendons – attach muscle to bone Tendons – attach muscle to bone Origin – is the relatively STABLE part of the skeleton where the muscle is attached Origin – is the relatively STABLE part of the skeleton where the muscle is attached Insertion –is the FREE MOVING part of the skeleton where the muscle attaches to cause movement Insertion –is the FREE MOVING part of the skeleton where the muscle attaches to cause movement Biceps origin is at the scapula Biceps origin is at the scapula Biceps insertion is on the radius and allows flexion of the arm at the elbow Biceps insertion is on the radius and allows flexion of the arm at the elbow

8 Prime Movers – are the muscles that perform the actual movement Antagonists – are the muscles that produce the opposite movement of the prime mover Biceps contract and flex and would be the prime mover Biceps contract and flex and would be the prime mover Triceps relax and extend and would be the antagonist Triceps relax and extend and would be the antagonist

9 Skeletal Muscle Groups Different characteristics can be used when naming muscles: Different characteristics can be used when naming muscles: 1. Location or Position – lateral, medial, internal, external, etc. 2. Size – maximus, major, minor, etc. 3. Shape – triangular (deltoid), trapezoid (trapezius), etc. 4. Action – flexor, adductor, abductor, etc.

10 Effects of Aging on Muscles Age 40 begins a gradual loss of muscle cells which results in a decrease in muscle size Age 40 begins a gradual loss of muscle cells which results in a decrease in muscle size Loss of power – especially in the vertebral column – causes the “bent over” appearance of KYPHOSIS (hunchback) Loss of power – especially in the vertebral column – causes the “bent over” appearance of KYPHOSIS (hunchback) Activity and life-long exercise can delay the onset of undesirable effects of aging Activity and life-long exercise can delay the onset of undesirable effects of aging

11 Muscle Diseases Muscular Dystrophy – is a group of disorders where there is a deterioration of muscle Muscular Dystrophy – is a group of disorders where there is a deterioration of muscle This disease: This disease: Progresses at different ratesProgresses at different rates Occurs more frequently in malesOccurs more frequently in males Causes weakness & paralysisCauses weakness & paralysis Causes death due to weakness in cardiac muscle or paralysis of respiratory musclesCauses death due to weakness in cardiac muscle or paralysis of respiratory muscles Life expectancy between 20 & 40 yearsLife expectancy between 20 & 40 years Has no known cureHas no known cure

12 Myasthenia Gravis – is a chronic disease that causes fatigue with the slightest exertion Affects adults Affects adults Begins with the muscles of the head and neck Begins with the muscles of the head and neck Myalgia - chronic muscle pain

13 Disorders Associated with Structures Bursitis – inflammation of the bursa sacs which include: Bursitis – inflammation of the bursa sacs which include: “Housemaid’s Knee” –patella bursa inflames due to pressure on the knee“Housemaid’s Knee” –patella bursa inflames due to pressure on the knee Ischial Bursitis – common among people who sit a lotIschial Bursitis – common among people who sit a lot “Student’s Elbow” – point of the elbow becomes inflamed“Student’s Elbow” – point of the elbow becomes inflamed

14 Bunions Enlargements commonly found at the base and side of the big toe Enlargements commonly found at the base and side of the big toe

15 Tendonitis Inflammation of the tendons from overexertion Inflammation of the tendons from overexertion

16 Carpal Tunnel “repetitive-use” syndrome that affects muscles and nerves supplying the hands and fingers “repetitive-use” syndrome that affects muscles and nerves supplying the hands and fingers

17 Muscular Disorders Due to Spasm or Injury Spasm – sudden, involuntary muscular contraction which is painful Spasm – sudden, involuntary muscular contraction which is painful Cramps – strong, painful contractions Cramps – strong, painful contractions Strains – common injury caused by overuse or overstretching Strains – common injury caused by overuse or overstretching “Charley Horse” – soreness and stiffness in a muscle caused by a strain “Charley Horse” – soreness and stiffness in a muscle caused by a strain

18 Sprains – are more severe than strains and can involve detachments of muscles from bones, tearing of muscles, damage to ligaments, blood vessels or nerves Sprains – are more severe than strains and can involve detachments of muscles from bones, tearing of muscles, damage to ligaments, blood vessels or nerves Atrophy – wasting away of or decrease in the size of a muscle from lack of use Atrophy – wasting away of or decrease in the size of a muscle from lack of use

19 Rigor Mortis A stage of rigidity of muscles after death occurs A stage of rigidity of muscles after death occurs Calcium escapes and causes actin and myosin to slide together and contract Calcium escapes and causes actin and myosin to slide together and contract With no ATP being produced, muscles remain contracted and become rigid With no ATP being produced, muscles remain contracted and become rigid

20 Effects of Exercise Vasodilation – is the increase in the diameter of blood vessels Vasodilation – is the increase in the diameter of blood vessels Allows blood to flow more easily Allows blood to flow more easily More blood is pumped to the heart More blood is pumped to the heart Increased load on the heart strengthens cardiac muscle and improves circulation Increased load on the heart strengthens cardiac muscle and improves circulation