1. Smooth muscle surrounds the major hollow organs - including: blood vessels, bronchi, gut, uterus, bladder. Responsive to a variety of stimuli: neural input (autonomic and enteric nervous systems) broad array of hormones and drugs metabolites Diverse Functions Smooth Muscle

2. Smooth Muscle – Non-Striated Arteries – blood vessels Lines Hollow Organs - Uterus - Alimentary Canal Lines Ducts of Secretory Glands – e.g. Salivary - Maintain Tension for long periods - Rhythmically Contract to Propel Contents - Speed of Contraction 10X less than striated muscle * Coupled into a syncitium by gap junctions

3. Rhythmic Changes in Smooth Muscle Membrane Potential Inhibitory Input from Myenteric Inter- neurons Limits the Level of Depolarization Interstitial Cells of Cajal (ICC): Pacemaker Cells with Ion Channel Characteristics Similar to SA node cells Slow Waves

4. membrane potential mV Force (gms) tetrodotoxin slow waves spikes Slow Waves Exhibited in Duodenal Visceral Smooth Muscle Cells

5. Digestive Inter-digestive Patterns of Contractility Patterns of Motor Activity

6. Digestive Inter-digestive Patterns of Contractility Tonic Phasic Force (gms) Patterns of Motor Activity

7. Peristalsis: Propulsive Movements- Central Coordination Rhythmic Segmentation: Mixing and Slow Propulsion- Local Control Paced by Slow Wave Frequency Patterns of Motor Activity

8. Reservoir: Colon, Proximal Stomach Mixing: Distal Stomach, Small and Large Intestine Propulsion: Distal Stomach through Colon, Esophagus 3 Functions of Motility

9. Proximal Stomach -Reservoir: Receptive Relaxation Distal Stomach -Mixing and Grinding -Regulation of Emptying

10. Distal Esophagus LES Proximal Stomach mm Hg Intraluminal pressure mm Hg Swallow Basal Tone Relaxation Basal Tone Seconds 0 0 0 mm Hg

11. Minutes Fraction in Stomach Solid Liquid 1.0 0.8 0.6 0.4 0 0.2 0 3060 90 120 150180 Distal Stomach

12. Volume Remaining in Stomach % Minutes pH 2.0 pH 4.0 pH 7.0 100 50 0 0 1020 Gastric Emptying

13. Peristalsis: Propulsive Movements- Central Coordination Rhythmic Segmentation: Mixing and Slow Propulsion- Local Control Paced by Slow Wave Frequency Patterns of Motor Activity

14. cycles /min Duodenum Pylorus Ileocecal Junction Jejunum Ileum 12 11 10 9 8 : Mixing and Movement SLOW WAVE FREQUENCY

15. Haustrations: Proximal Colon- Mixing Mass Movements: Propulsive Contractions :: Rectosphincteric Reflex Motility within the Large Intestine

16. Lower Esophageal: Retard Gastric (LES) Retropulsion Pyloric: Retard Gastric Emptying Ileocecal: Retard Colonic Retropulsion Internal Anal: Regulate Emptying Into the Rectum External Anal: Regulate Defecation Primary Role of Individual Sphincters

17. Esophagus: Seconds Stomach: 1-3 Hours Small Intestine: 3-5 Hours Colon: 1-3 Days Transit Times During Digestion/Absorption of a Meal

18. I 45 - 60 0 II 30 - 45 50 III 5 - 10 100 MMC Phase Duration (min) % Slow Waves with Spikes Myoelectric Activity Contraction Amplitude mm Hg mV Time Inter-Digestive Period: Temporal Patterns of Motility

19. Phase III MINUTES Phase III Inter-Digestive Period: Migrating Motor Complex.

20. Endogenous Motilin MMCs Duodenum Prox. Jejunum Mid Jejunum Intravenous Motilin Phase IPhase IIPhase III hours Exogenous motilin stimulates both MMCs and endogenous motilin release Inter-Digestive Period: Migrating Motor Complex