Muscular System

Functions of Muscles  Produce movement  Maintain posture  Stabilize joints  Generate heat

Vocabulary  ATP  Acetylcholine  Antagonist  Abduction  Adduction  Atrophy  Extension  Flexion  fixators  hypertrophy  Insertion  Isometric contraction  Isotonic contraction  Muscle tone  Muscle fatigue  Motor unit  Neuromuscular junction  Origin  Oxygen debt  Prime mover  synergist

Three classes of muscles CardiacSmoothSkeletal Body location Cell shape contraction

Functional Characteristics  Irritability  Ability to receive and respond to stimuli  Contractility  Can shorten  Extensibility  Can stretch  Elasticity  Regain shape

Levers  For movement to occur, bones and muscles interact as a simple machine called a lever.  Four basic components of levers  Rigid bar, a fulcrum on which the bar turns, the resistance, and the force needed to move the bar.  Bicep curl: forearm bones are the rigid bar, elbow joint is the fulcrum, the weight in the hand is the resistance, and the biceps brachii muscle in the front of the arm generates the energy to move the weight.

Gross Anatomy of skeletal muscle  Tendons attach muscle to bone  Connective tissue wrappings  Fascia covers the muscle  Epimysium covers each bundle of muscle fibers (fascicles)  Perimysium covers each individual fascicle

Nerve supply Each skeletal muscle fiber connects to a nerve cell called “motor neuron” at the neuromuscular junction. Attachments Origin: muscles attachment to fixed point Insertion: muscles attachment to the bone being moved

 Skeletal muscles attach to bone by either a tendon or an aponeurosis  Striated  Voluntary  Function in Groups

Skeletal Muscle activity  Must be stimulated by a nerve first  Neurotransmitters (acetylcholine) are hormones stimulated by the nerve impulse to initiate a muscular contraction.  Calcium – these ions are needed for the physiology of a muscle contraction; located in the sarcoplasmic reticulum  All-or-none response- muscle cell fiber (myofibril) contract completely

 ATP  Only source of energy for muscle activity  Limited amounts from cellular respiration  Produced by muscle in two ways  Creatine phosphate- ATP reserve for later when oxygen supplies are low during anaerobic activity.  Aerobic respiration At rest and low-intensity workouts

Muscle fatigue  Occurs when muscles are no longer able to contract  Occurs during oxygen debt (insufficient amount of oxygen to produce ATP)

5 Golden Rules of Skeletal Muscle Activity  All muscles cross at least one joint  The bulk of the muscle lies proximal to the joint it crosses  All muscles have at least two attachments: origin and insertion  During contraction insertion moves toward origin  Muscles can only pull; never push

Exercise and muscles  Muscle tone (Hypertrophy)  State of continuous muscle contraction   Atrophy  Wasting away of muscle not being used

 What is strength?  Amount of force that can be applied by a muscle during maximum contraction.  Three types of strengthening exercises  Isometric: contracts the muscle without changing its length.  Example: quad set  Isotonic: shortens and lengthens muscle through a complete range of motion.  Example: leg press or a squat  Isokinetic: Resistance is given at a fixed speed of movement with accommodating resistance.  Use of a device with a mechanical pressure system to produce a constant speed of motion; use for diagonostics or rehab.

Major Skeletal Muscles  Over 600 skeletal muscles in the body.  A muscles name often describes the muscle itself.  Muscles’ size (gluteus maximus)  Shape (trapezius)  Location (tibialis anterior)  Action (pronator teres)  Number of attachments (triceps)  Several muscles work in groups for common action:  Rotator cuff muscles:  Supraspinatus, infraspinatus, subscapularis, teres minor  Quadriceps: rectus femoris, vastus medialis, v. lateralis, v. intermedius  Hamstrings: biceps femoris, semitendinosis, semimbranosis

Identify the actions of the following muscles  Biceps brachii  Brachioradialis  Buccinator  Deltoid  Diaphragm  External obliques  Hamstring (muscle group)  Gastrocnemius  Gluteus maximus  Gluteus medius  Intercostals  masseter  Latissimus dorsi  Pectoralis major  Quadriceps muscle group  Rectus abdominis  Sartorius  Soleus  Sternocleidomastoid  Tibialis anterior  Trapezius  Triceps brachii

Orthopedic topics  Osteomyelitis  Chondromalacia  Lateral ankle sprain  Meniscus tear  Rotator cuff tear  SLAP lesion  Bankart tear  Epicondylitis  ACL tear  MCL tear  Osteoarthritis  Bucket handle meniscal tear  Ligament sprains  Muscle strain  Spondylolysis  Osgood Schlatter’s disease  Jumper’s knee  Iliotibial band friction syndrome

 Bursitis  March fracture  Colles’ fracture  Avulsion fractures  Turf toe  Plantar fasciitis  Herniated disk  osteoporosis  Duchenne’s muscular dystrophy  Muscular sclerosis