1. Muscle Tissue 2007

2. Specialized for contractions Specialized for contractions Elongated cells Elongated cells Unique terms to describe components of muscle cells Unique terms to describe components of muscle cells Sarcolemma – muscle cell membranes Sarcolemma – muscle cell membranes Sarcoplasm – cytoplasm Sarcoplasm – cytoplasm Sarcoplasmic reticulum – endoplasmic reticulum Sarcoplasmic reticulum – endoplasmic reticulum Muscle cell = muscle fiber (not like a CT fiber) Muscle cell = muscle fiber (not like a CT fiber) 3 types of muscle: skeletal, cardiac, smooth

3. Organization of Skeletal Muscle

4. Skeletal (striated, voluntary) Muscle Long, cylindrical shaped cells Long, cylindrical shaped cells Multinucleate cells Multinucleate cells Peripheral nuclei Peripheral nuclei Striated (striped) appearance seen in light microscope: A band, I band, Z line, H band. Striated (striped) appearance seen in light microscope: A band, I band, Z line, H band.

5. Skeletal Muscle (longitudinal section)

6. Myofibril – structural & functional subunit of muscle cells; consists of myofilaments. Myofilaments – the contractile elements of skeletal muscle; consist of filamentous polymers of myosin (thick filaments) and actin (thin filaments).

7. Sarcomere – the basic contractile unit of skeletal muscle; extends from Z-line to Z-line actinmyosin

8. Motor end plate – the area of contact made by the endings of a motor neuron onto a muscle fiber.

9. Motor end plate - releases the neurotransmitter acetylcholine.

10. Neuromuscular Junction

11. Skeletal Muscle (cross-section, low power)

12. Skeletal Muscle – High Power

13. Cardiac Muscle - Striated - Single, large, oval, centrally located nucleus - Branched cells - Intercalated disks = specialized end-to-end junctions

14. Cardiac Muscle

15. Intercalated Disks - anchor myofibrils and permit fast transmission of contractions; consist of 3 components:

16. Cardiac Muscle

17. Mitochondria in Cardiac Muscle

18. Purkinje Fibers - large, modified cardiac muscle cells that electrical transmit impulses to cardiac muscle.

19. Smooth Muscle

20. Most body tubes lined externally by smooth muscle. Most body tubes lined externally by smooth muscle. Important in sphincters, peristalsis, blood pressure regulation. Important in sphincters, peristalsis, blood pressure regulation. “involuntary muscle” – activated by autonomic nervous system and hormones. “involuntary muscle” – activated by autonomic nervous system and hormones.

21. Smooth Muscle Cells are fusiform in shape – round at center and tapered at ends. Cells are fusiform in shape – round at center and tapered at ends. A single nucleus, centrally located. A single nucleus, centrally located. When contracted, nuclei may have a corkscrew appearance. When contracted, nuclei may have a corkscrew appearance. No striations – actin & myosin present but not regularly arranged in a repeated pattern. No striations – actin & myosin present but not regularly arranged in a repeated pattern. Cells connected to each other by gap junctions that allow conduction of impulses and contraction from one cell to another. Cells connected to each other by gap junctions that allow conduction of impulses and contraction from one cell to another.

22. Smooth Muscle: top: cross-section; bottom: longitudinal section