Muscular System

Muscular System Functions: 1. produce movement 2. Maintain posture 3. Stabilize joints 4. Generate heat 5. Move substances (fluid, food etc)

Properties of Muscles: Excitability: capacity of muscle to respond to a stimulus Contractility: ability of a muscle to shorten and generate pulling force Elasticity: ability of muscle to recoil to original resting length after stretched

 Muscles are responsible for all types of body movement – they contract or shorten and are the machine of the body  Three basic muscle types are found in the body  Skeletal muscle  Cardiac muscle  Smooth muscle

Muscle Coverings:  Epimysium –tissue that covers the entire skeletal muscle. Separates the muscle from all other organs  Fascicle–A group of muscle fibers Perimysium- surrounding a group a fascicle. Contains blood vessels and nerves. Endomysium- surrounds individual muscle fiber. Also has blood vessels and nerves.

Muscle Coverings:

Head and Neck Muscles

Muscles of the cephalic area:

Trunk Muscles

Muscles of the Anterior Trunk area:

latissimus dorsi Muscles of the Posterior Trunk area:

Posterior of leg Anterior of leg Muscles of the Posterior and Anterior Leg:

Types of Ordinary Body Movements  Flexion – decreases angle of joint and brings two bones closer together  Extension- Increase the angle or extending something  Rotation- movement of a bone in longitudinal axis (back and forth), shaking head “no”

 Abduction: Moving away from the body or anatomical position  Adduction: Moving towards the body or anatomical position.  Circumduction: moving in a circular motion Types of Ordinary Body Movements

 Flexion – decreases angle of joint and brings two bones closer together  Extension- Increase the angle or extending something  Rotation- movement of a bone in longitudinal axis (back and forth), shaking head “no”

 Abduction: Moving away from the body or anatomical position  Adduction: Moving towards the body or anatomical position.  Circumduction: moving in a circular motion Types of Ordinary Body Movements

Anatomy of Skeletal Muscles:  Cells are multinucleate

 Myofibril- The smallest unit  Bundles of myofilaments  Myofibrils are aligned to give distinct bands  I band = light band  A band = dark band Anatomy of Skeletal Muscles:

 Sarcomere- one segment on a myofibril (from Z disc to Z disc)  (these are what allow the muscle to contract and move)

Components of a Sarcomere:  Thick filaments = myosin filaments  Has ATP  (for energy to be broken down and used in order to move) Anatomy of Skeletal Muscles:

Components of a Sarcomere:  Thin filaments = actin filaments

How skeletal muscles move or “slide” Thin Actin slide past the thick Myosin so that the actin and myosin filaments overlap In the relaxed state, thin and thick filaments overlap only slightly In order for this process to start sodium must ender the cell (active transport) and the nervous tissue sends a signal to begin contraction

How skeletal muscles move or “slide”  Step 1: Activation by nerve causes Calcium to be released.  Step 2: This allows the myosin heads to attach to the actin.  Step 3: ATP is used and broken down in order to “pull” the myosin over the actin (contracting the muscle)  Step 3: Myosin heads then bind to the next site of the actin filament and get ready for a second contraction. This shortens the Z line and they over lap.  Step 4; They continue until the muscle contracts and the two over lap more and more until the H zone disappears.  Step 5: To release the contraction the Calcium is taken back into the muscle fibers which covers the location so myosin can’t bind. Now the muscle is relaxed  IF calcium doesn’t go back in the contraction is prolonged and called a charlie horse or Cramp!

How skeletal muscles move or “slide”

Within a skeletal muscle, not all fibers may be stimulated during the same interval  Muscle force depends upon the number of fibers stimulated  More fibers contracting results in greater muscle tension  Muscles can continue to contract unless they run out of energy How skeletal muscles move or “slide”

Energy for Muscle contraction and fatigue  Muscles use stored ATP for energy  Only 4-6 seconds worth of ATP is stored by muscles

 1. After this initial time, other pathways must be utilized to produce ATP  Muscle cells contain creatine phosphate (CP)  CP regenerates new ATP  CP supplies only last 20 seconds Energy for Muscle contraction and fatigue

 2.Glycolysis  Reaction that breaks down glucose with or without oxygen to make ATP  Without Oxygen glucose breaks into lactic acid which is what builds up and produces muscle fatigue.

Muscle Fatigue and Oxygen Debt  When a muscle is fatigued, it is unable to contract  The common reason for muscle fatigue is oxygen debt or lactic acid build up.  Oxygen is required to get rid of accumulated lactic acid

Disorders relating to the Muscular System Muscular Dystrophy: inherited, muscle enlarge due to increased fat and connective tissue, but fibers degenerate and atrophy Myasthemia Gravis: progressive weakness due to a shortage of acetylcholine receptors

For the test.. Muscular and Skeletal For Skeletal – skeletal diagram Bone formation Joints – types, range of motion For Muscular- the study guide except the following: 6, 7, 12, 13, 14, 17, 18, 25