1. Muscle Tissue Specialized for contraction Elongated cells
3 types of muscle: skeletal, cardiac, smooth

2. Organization of Skeletal Muscle
Sarcolemma = muscle cell membranes
Sarcoplasm = cytoplasm
Sarcoplasmic reticulum = endoplasmic reticulum
Muscle cell = muscle fiber (not like a CT fiber)

3. Skeletal Muscle (voluntary, striated)
longitudinal section
Long, cylindrical shaped cells
Nuclei are multiple and peripherally located
Striated (striped) appearance due to banding pattern:
A band, I band, Z line, H band.

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

5. Myofilaments = the contractile elements of skeletal muscle; = myosin (thick filaments) and actin (thin filaments)
actin
myosin

6. Motor end plate – the region of sarcolemma contacted by the axon terminals of a motor neuron.
higher power

7. Neuromuscular Junction – the site of neurotransmitter (acetylcholine) release

8. Skeletal Muscle (cross-section)
low power
higher power

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

10. Cardiac Muscle (longitudinal sections)
intercalated disk
striated,
branching
cells

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

12. Lots of Mitochondria (tiny black dots) in Cardiac Muscle

13. Purkinje Fibers - large, modified cardiac muscle cells; transmit electrical impulses to cardiac muscle.

14. Smooth Muscle (involuntary)
- Forms the walls of hollow organs and bodily tubes
- Important in sphincters, peristalsis, blood pressure regulation.
– Activated by autonomic nervous system and hormones.
longitudinal section

15. Smooth Muscle
Cells are fusiform in shape – round at center and tapered at ends.
A single nucleus, centrally located.
When contracted, nuclei may have a corkscrew appearance.
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.

16. Smooth Muscle (top: cross-section; bottom: longitudinal section)

17. Summary of the 3 Muscle Types