1. Muscular Systems Overview April 22, 2015 Sutherlin AST W. Crawford Adapted from “The Anatomy of Domesticated Animals” and the Colorado Agriscience Curriculum

2. The Muscular System Function: locomotion or movement life support – gathering food – reproduction – simple body functions

3. The Muscular System Structure of muscles: – consist of mostly protein – found in bundles or sheets – connected to bones by tendons

4. The Muscular System Classification of muscles: – Voluntary – Involuntary The lean portion of animals carcass is what is used for food (muscles)

5. The Muscular System Voluntary – Under control of the animals will – All are straited (striped) – Flexor- decreases the angle between two bones (biceps) – Extensor- opposite side and increases the angle of two bones (triceps)

6. The Muscular System Involuntary – Not under the control of the animals free will – Heart – Secretory organs- force out secretions – Digestive system- movement of food – Respiratory system – Smoothed or straited

7. Let’s go further…

8. Muscular System Functions Body movement Maintenance of posture Respiration Production of body heat Communication Constriction of organs and vessels Heart beat

9. Properties of Muscle Contractility – Ability of a muscle to shorten with force Excitability – Capacity of muscle to respond to a stimulus Extensibility – Muscle can be stretched to its normal resting length and beyond to a limited degree Elasticity – Ability of muscle to recoil to original resting length after stretched

10. Muscle Tissue Types Skeletal – Attached to bones – Nuclei multiple and peripherally located – Striated, Voluntary and involuntary (reflexes)

11. Muscle Tissue Types Smooth – Walls of hollow organs, blood vessels, eye, glands, skin – Single nucleus centrally located – Not striated, involuntary, gap junctions in visceral smooth

12. Muscle Tissue Types Cardiac – Heart – Single nucleus centrally located – Striations, involuntary

13. Skeletal Muscle Structure Muscle fibers or cells – Develop from myoblasts – Numbers remain constant Connective tissue Nerve and blood vessels

14. Embryologic origin Muscle cells are the result of the conjoining of embryo cells called myoblasts Explains multiple nuclei

15. Muscle Fibers Muscles are attached to bones by tendons – Tendon is the connective tissue – This tissue also encapsules the muscle and forms the epimysium

16. Muscle Fibers Skeletal muscle is made up of bundles of subunits called fasicles (or fascicles) Fascicles are covered by connective tissue call perimysium Fascicles are made up of muscle cells – Muscle cells = muscle fibers

17. Muscle Fibers Muscle cells – Ensheathed in endomysium – Made up of long protein molecules call myofibrils – Myofibrils have two types of myofilaments Thick myofilament Thin myofilament

19. Muscle Fiber

20. Sarcomeres The myofibril is divided into chains of sarcomeres Sarcomeres are the sections of myofilaments that slide over one another as muscles contract and relax This is where the work happens

21. Organization of myofilaments I:

22. Sliding Filament Model Actin myofilaments sliding over myosin to shorten sarcomeres – Actin and myosin do not change length – Shortening sarcomeres responsible for skeletal muscle contraction During relaxation, sarcomeres lengthen

23. Sliding filament model II:

24. Sarcomere Shortening

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