Without these our bones could not move, our lungs could not breathe, and our heart would not beat- we would die! Your body is made up of approximately how many muscles? Let’s check out this amazing system!!!!

Mrs. DiOrio The Muscular System

Muscle Anatomy and Physiology

Skeletal Muscle Characteristics  Inserts by tendons into your bones  Voluntary – we can control it  Cells are surrounded and bundled by connective tissue- “What does bundling provide?”  Tires easily

Smooth Muscle Characteristics  Controls movements of internal organs  EX: Digestive system  Involuntary – no conscious control  Can stay contracted for long periods of time…stomach cramps… Figure 6.2a

Cardiac Muscle Characteristics  Contracts rhythmically “waves”  Regulates heart  Involuntary  Can sustain strong continuous contractions without getting tired Figure 6.2b

Function of Muscles  Movement of bones  Maintain posture  Stabilize joints  Generate heat

8 Connective Tissue Wrappings of Skeletal Muscle

 Endomysium – around single muscle fiber  Perimysium – around a fascicle (bundle) of fibers Figure 6.1

Connective Tissue Wrappings of Skeletal Muscle  Epimysium – covers the entire skeletal muscle  Fascicle – bundle of muscle fibers Figure 6.1

11 So what does “bundling” provide?

12 85% of body heat is generated by muscle contractions. How does a muscle produce force?

Microscopic Anatomy of Skeletal Muscle Figure 6.3a

Microscopic Anatomy of Skeletal Muscle  Sarcolemma – specialized plasma membrane surrounding each muscle fiber Figure 6.3a

Microscopic Anatomy of Skeletal Muscle  Sarcoplasmic reticulum- surrounds each and every myofibril. Figure 6.3a

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Microscopic Anatomy of Skeletal Muscle  Myofibril:  Bundles of myofilaments-thin & thick threads found in myofibrils  Myofibrils are aligned to give distinct bands  I band = light band  A band = dark band Figure 6.3b

 Sarcomere  Unit of muscle contraction- like little chains aligned end to end. Figure 6.3b

Microscopic Anatomy of Skeletal Muscle  Sarcomere:  Thick filaments = myosin filaments  Thin filaments = actin filaments Figure 6.3c

Microscopic Anatomy of Skeletal Muscle  Myosin and actin overlap somewhat  At rest, there is a bare zone that lacks actin filaments

The Sliding Filament Theory of Muscle Contraction  The sliding filament theory is the explanation for how muscles produce force (or, usually, shorten). It explains that the thick and thin filaments within the sarcomere slide past one another, shortening the entire length of the sarcomere. In order to slide past one another, the myosin heads will interact with the actin filaments and, using ATP, bend to pull past the actin. Figure 6.7

Vocabulary Summary Muscle Fascicle Fiber Myofibril Sarcomere Myofilament Thick Thin

Get Ready for QUIZ #1!!!!  Rowboat moving through water, with the oars pulling the boat along with each stroke, to help clarify the concept  Note that Huxley’s Sliding Filament Theory is very unique in that other scientists have not improved his explanation of muscle contraction even after seven decades of research.

Contraction of a Skeletal Muscle  Muscle fiber contraction is “all or none”  Not all fibers may be stimulated during the same interval  Different combinations of muscle fiber contractions may give graded responses – different degrees of skeletal muscle shortening

Muscle Fatigue and Oxygen Debt  When a muscle is fatigued, it is unable to contract  The common reason for muscle fatigue is oxygen debt, lactic acid build up & depletion of glycogen  Oxygen must be “repaid” to tissue to remove oxygen debt  Oxygen is required to get rid of accumulated lactic acid  EX: Marathon runners collapse by muscle fatigue…remember?

Muscle Atrophy- Example?  During atrophy, cellular & molecular mechanisms are not able to balance; leads to muscle loss.   cross sectional area=  muscle mass but not muscle fibers  protein synthesis  protein degradation Sarcopenia- muscle loss to to aging; connective tissue  so muscles are stringier.

Types of Muscle Contractions  Isotonic contractions  Myofilaments slide past each other during contractions  The muscle shortens- tension remains the same; muscles go through a range of motion.  EX: knee bending, rotating arms, smiling, picking a book up off the table and placing it back!

Types of Muscle Contractions Isometric contractions Tension in the muscles increases The muscle is unable to shorten; No range of motion. EX: pushing against a wall, holding a book steady using an outstretched arm, holding a pose.

Muscles and Body Movements  Movement is attained due to a muscle moving an attached bone Figure 6.12

Muscles and Body Movements  Muscles are attached to at least two points!  Origin – attachment to a immoveable bone  Insertion – attachment to the movable bone  When a muscle contracts it moves toward the origin!!! Figure 6.12

Muscles and Body Movements  5 GOLDEN rules of Skeletal Muscle Activity:  Cross at least 1 joint  Lies proximal to joint crossed  At least 2 attachments  Muscles pull not push!  During contraction, the muscle insertion moves toward the origin Figure 6.12

Effects of Exercise on Muscle  Results of increased muscle use:  Increase in muscle size  Increase in muscle strength  Increase in muscle efficiency  Muscle becomes more fatigue resistant

Types of Ordinary Body Movements  Inversion- turning sole of foot medially  Dorsiflexion-standing on your heels ***tibialis anterior makes this happen!  Abduction-moving limb away from midline; raise arm up toward shoulder  Adduction-opposite of abduction!  EX: Jumping Jacks!!!

Body Movements Figure 6.13

Get ready for QUIZ #2!!! Muscle Contractions & Body Movements =5_VL5QVszq0 =5_VL5QVszq0 Please get a partner and choose an exercise to demo! Please get a partner and choose an exercise to demo!

Naming Skeletal Muscles ● Location— bone or body region associated with the muscle ● Shape— e.g., deltoid muscle (deltoid = triangle) ● Relative size— e.g., maximus (largest), minimus (smallest), longus (long) ● Direction of fibers or fascicles—e.g., rectus (fibers run straight), transversus, and oblique (fibers run at angles to an imaginary defined axis)

Naming Skeletal Muscles ● Number of origins— e.g., biceps (2 origins) and triceps (3 origins) ● Location of attachments— named according to point of origin or insertion ● Action— e.g., flexor or extensor, muscles that flex or extend, respectively

Head and Neck Muscles Figure 6.14

Arm Muscles Only!!!

Quick Check: Quick Check:  Shaving  Smiling  Raising your eyebrows  Chewing  Back of your head  Fastest or busiest over a 100,000x’s a day  Side of neck  Shoulder rub

Trunk Muscles

Deep Trunk and Arm Muscles Slide 6.40 Figure 6.16

Muscles of the Pelvis, Hip, and Thigh Figure 6.18c

Muscles of the Lower Leg Figure 6.19

Superficial Muscles: Anterior Figure 6.20

Superficial Muscles: Posterior Figure 6.21

Ankle Sprains

Examples of Strains

Sprains and Strains are categorized according to severity. Grade I (mild) sprain or strain involves some stretching or minor tearing of a ligament or muscle. Grade II (moderate) sprain or strain is a ligament or muscle that is partially torn but still intact. Grade III (severe) sprain or strain means that the ligament or muscle is completely torn, resulting in joint instability.

First Aid R – rest I - immobilize (ice) C - compression E - elevation

ACL Surgery Most surgery for ACL injuries involves replacing the ACL with tissue called a graft Usually an autograft (tendon taken from another part of the body) is used The most common grafts used are the tendon of the kneecap or one of the hamstring tendons Another choice is allograft tissue, which is taken from a deceased donor

Tommy John Surgery Repairs an injured elbow ligament (UCL construction) A surgeon replaces the injured UCL with a tendon taken from somewhere else in the patient’s body