Applied Exercise Physiology Section 5: Body Systems Topic 1: Muscular System Prepared by Mr. Cerny Niagara Wheatfield Senior High School

Types of Muscle Cardiac Cardiac  Heart Smooth Smooth  Organ lining Skeletal Skeletal  Movement  40% of total body mass

Types of Muscle (con’t) Cardiac Smooth Skeletal

Skeletal Muscle How many different muscles can there be? How many different muscles can there be? ~660 ~660

Skeletal Muscle Structure Cylindrical fibers bunched together Cylindrical fibers bunched together Cable wire c.s.

Macrostructure It is the number of muscle fibers packed into a given muscle cross-sectional area that determine overall force- generating capacity It is the number of muscle fibers packed into a given muscle cross-sectional area that determine overall force- generating capacity Skeletal muscle c.s. 40x

Microstructure Sarcomere: basic functional unit of muscle basic functional unit of muscle Striated (light & dark bands) Striated (light & dark bands) Contains ACTIN & MYOSIN filaments that are responsible for contraction Contains ACTIN & MYOSIN filaments that are responsible for contraction

Actin & Myosin

Where did the Ca ++ come from? Ca ++ is stored and released from the sarcoplasmic reticulum (SR) Ca ++ is stored and released from the sarcoplasmic reticulum (SR) SR is a network of tubules within the muscle fiber SR is a network of tubules within the muscle fiber

Sarcoplasmic Reticulum

Excitation-Contraction Coupling 1. Action potential travels along neuron by the temporary changing of charges 2. Nerve impulse causes the release of acetylcholine (ACh). 3. ACh travels across neuromuscular junction, binding to muscle cell membrane. 4. ACh binding initiates an electrical impulse which travels across membrane and into T tubules. 5. Impulse stimulates release of Ca +2 from SR. 6. Ca +2 binds with t-t complex of the actin filaments, shifting it's position, exposing myosin binding sites. 7. Myosin binds to actin; Ca +2 presence also causes enzymatic actions of myosin to breakdown ATP into ADP + P + energy. 8. Energy of ATP degradation causes shape change of myosin head, pulling actin molecule toward center of sacromere. 9. After sliding, a new ATP binds to myosin, breaking the myosin-actin bond, releasing the myosin head. 10. If Ca +2 is still present, the process repeats itself until sacromere has shortened completely. 11. If a nerve impulse ceases, the Ca +2 is reabsorbed by the SR and the muscle relaxes.

Muscle Fatigue 1 1 What causes it? 1) Reduction in ATP 1) Reduction in ATP  Under high stress, ATP utilization reduced faster than ATP production 2) Peripheral metabolic bi-products 2) Peripheral metabolic bi-products  Lactic acid  H (and other free radicals)

Muscle Fatigue 3) Dehydration 3) Dehydration  Increases temp = decreases contractile properties 4) Decrease nerve signals/action potentials 4) Decrease nerve signals/action potentials 5) Reduction of Ca 5) Reduction of CaCa  “leakage” 1 leakage1leakage1  From decrease nerve connection

Muscle Types ForceSpeed # mit. Resistance to fatigue Activity # capillaries Oxidative / nonoxidative Slow twitch (I)Same (slightly less) SlowManyYesEnduranceManyOxidative Fast twitch (II)Same (slightly more) FastFewNo Sprinting /bursts Fewnonoxidative

Muscle Strength “Bigger” muscles:  Usually NOT increase in muscle cells (hyperplasia)  Usually an increase in existing tissue size (hypertrophy) Factors contributing: Genetics Genetics Exercise Exercise Nutrition Nutrition Endocrine Endocrine Environmental Environmental Nervous Nervous

The Muscular System 11.0 Describe Animal Health Needs 11.3 Describe the musculoskeletal system

Function of the muscular system Provides movement in conjunction with the skeletal system Provides movement in conjunction with the skeletal system Important in life support Important in life support Used by humans and other animals for food Used by humans and other animals for food

Classifications of Muscles Voluntary: Movement of the muscle is under the control of the animal Voluntary: Movement of the muscle is under the control of the animal Involuntary: Movement of the muscle is not controlled by the animal Involuntary: Movement of the muscle is not controlled by the animal

Types of Muscles Smooth Muscles: Involuntary muscles, found in the walls of internal organs and the blood vessels. Smooth Muscles: Involuntary muscles, found in the walls of internal organs and the blood vessels.

Smooth Muscles Are not under voluntary control Are not under voluntary control Are spindle shaped and are not striated. Are spindle shaped and are not striated. Interlace to form Sheets of smooth muscle tissue. Interlace to form Sheets of smooth muscle tissue. Are found in many internal organs: Stomach, Intestines, Blood Vessel walls Are found in many internal organs: Stomach, Intestines, Blood Vessel walls

Types of Muscles Cardiac Muscles: Muscles that form a network to make up the heart. Not under active brain controll Cardiac Muscles: Muscles that form a network to make up the heart. Not under active brain controll

Cardiac Muscles Only found in the Heart Only found in the Heart Are Striated Are Striated Are NOT under Voluntary Control Are NOT under Voluntary Control Contract Without Direct stimulation by the Nervous System Contract Without Direct stimulation by the Nervous System

Types of Muscles Skeletal Muscles: Have a striped appearance, include voluntary and involuntary, attached to and moves your bones. This is a majority of the muscle tissue in your body. Skeletal Muscles: Have a striped appearance, include voluntary and involuntary, attached to and moves your bones. This is a majority of the muscle tissue in your body.

Skeletal Muscles Are made of Elongated Cells called MUSCLE FIBERS Are made of Elongated Cells called MUSCLE FIBERS Are grouped into dense bundles called FASCICLES Are grouped into dense bundles called FASCICLES Are LARGE and have MORE than ONE NUCLEUS Are LARGE and have MORE than ONE NUCLEUS Most are Voluntary Most are Voluntary