1. CH 9 Smooth Muscle Tissue J.F. Thompson, Ph.D.

2. Smooth Muscle Cells nonstriated = smooth uninucleate

3. Smooth Muscle Tissue Lacks the dense fibrous connective tissue sheaths of skeletal muscles, but have delicate endomysium Found in the walls of hollow internal organs (except the heart) Often organized into two antagonistic layers (longitudinal and circular) oriented perpendicular to each other

4. Characteristics of Smooth Muscle Found in the walls of hollow internal structures (digestive, respiratory, reproductive tracts, blood vessels) Arrector pili, pupil of the eye, etc. Involuntary (unconscious) Long, slow contractions, non-fatigable

5. Smooth Muscle Tissue

6. May be autorhythmic May have gap junctions Dense bodies are cytoskeletal anchors Myosin and Actin myofilaments are responsible for contraction

7. Smooth Muscle Tissue When the longitudinal layer contracts, the organ dilates and shortens When the circular layer contracts, the organ constricts and elongates

8. Contractions of Smooth Muscle Peristalsis – alternating contractions and relaxations of smooth muscles that squeeze substances through the lumen of hollow organs Segmentation – contractions and relaxations of smooth muscles that mix substances in the lumen of hollow organs

9. Contractions of Smooth Muscle Some smooth muscle cells: –Act as pacemakers and set the contractile pace for whole sheets of muscle –Are self-excitatory and contract without external stimuli Whole sheets of smooth muscle exhibit slow, synchronized contractions –They contract in unison, reflecting their electrical coupling with gap junctions

10. Regulation of Smooth Muscle Contracts under the influence of: –Autonomic Nervous System –Hormones –Local regulatory factors

11. End CH 9 Smooth Muscle Tissue