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Muscle Systems

Muscle Systems. Animal Science I Anatomy, Physiology, and Absorption of Nutrients. Objective. Name, locate and describe the functions of the parts of the muscle systems of animals. Types of Muscles. Skeletal Smooth Cardiac

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Muscle Systems

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  1. Muscle Systems Animal Science I Anatomy, Physiology, and Absorption of Nutrients

  2. Objective • Name, locate and describe the functions of the parts of the muscle systems of animals.

  3. Types of Muscles • Skeletal • Smooth • Cardiac • Differentiated based on their structure, location and method of control • Fig 5-4

  4. Skeletal (striated voluntary) • Most of the flesh referred to as meat • Called striated because of the dark bands that cross each muscle fiber • Subdivided into two typesbased on color • Red: muscle that is involved in sustained work • Pale/White: muscle that is activated on a more intermittent basis

  5. Skeletal Muscle

  6. Skeletal Muscle Structure • Exist in bundles enclosed in connective tissue that contain many muscle fibers of varying length • Cylindrical in shape • Muscle fibers are enclosed in a sheath of connective tissue • Myofibrils are the component parts of muscle fiber • Two types of myofilaments (myosin- thick, actin-thin) are found in the myofibril • Muscle contraction occurs when the thin myofilaments slide past the thick • Fig 5-5 • http://www.youtube.com/watch?v=0kFmbrRJq4w

  7. Skeletal Muscle Attachment • Usually tendons • One end to an unmovable part known as the origin and the other to a more moveable part known as the insertion

  8. Control • Controlled by the voluntary nervous system • Nerve endings are located on every muscle fibril • Muscles contract when stimulated by an impulse and relax in the absence of stimulation • Degree of contraction is related to the frequency of stimuli • Stimulus over a long period of time leads to fatigue, due to a build up of lactic acid in the muscle and a reduction in stored energy

  9. Adenosine Triphosphate (ATP) • Supplies the energy for muscle contraction

  10. Skeletal Muscles At Work • Work in pairs or groups • Muscles that begin movement are called agonists • Muscles that work in opposition of the agonists are called antagonists • Even when no work is being done, muscles are in a state to tension • This is called muscle tone and allows rapid muscular response as needed

  11. Smooth (unstriated involuntary) • Muscles that surround the hollow internal organs of the body • Two types: visceral and multiunit • Most in the vertebrate body are visceral • Multiunit smooth muscle is found where better muscular control is needed

  12. Smooth Muscle Characteristics • Activated by the autonomic nervous system • Generally act more slowly than the skeletal muscles • Do not have myofibrils or dark striations • Color is generally white • No origin or insertion points ; no attachment to the skeleton • Stretchable • Cells are smaller than skeletal and cardiac muscle cells • Appear spindle shaped • Contraction can be stimulated by: myosin-actin mechanism, chemicals, hormones

  13. Cardiac (striated involuntary) • Only found in the muscular wall of the heart • Striated like a skeletal muscle • Rectangular in shape with a central nucleus

  14. Cardiac (striated involuntary) • Contain two components not found in other types of muscle: intercalated discs and Purkinje fibers • Intercalated discs are dark thickenings that cross the muscle fibers and separate the cardiac cells • Purkinje fibers are specialized muscle fibers that are found in the lateral ventricles of the heart • They are part of the contractile system, carrying the contraction impulses to the ventricle muscles • Autonomic nervous system can speed up or slow down the rate of heart muscle contraction but it does not start the contractions

  15. Cardiac Muscle Contractions • Begins in the sinoatrial node that is located in the upper right atrium • Nerve stimulation is not required for this contraction to occur • When contraction begins it rapidly spreads to the entire muscle • Contraction is followed by a period of relaxation—during which it can’t be stimulated to contract again • These properties result in the rhythmic beating of the heart that is essential to the circulation of blood through the body

  16. Summary* • 3 types of muscles-skeletal, smooth, cardiac • Skeletal muscles make up most of the flesh referred to as meat • Skeletal muscle cells are cylindrical in shape and occur in bundles • Adenosine Triphosphate (ATP) supplies the energy for muscle contraction • Smooth muscles surround the hollow internal organs of the body • Smooth muscles are spindle shaped • Smooth muscles are able to expand • Cardiac muscles are only found in the muscular wall of the heart • Cardiac muscle cells are rectangular in shape with a central nucleus

  17. Assignment • Discussion Questions 6-9 p. 128due—

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