Physiology of Micturition- Cystometrogram.pptx

Physiology of bladder filling and emptying

1. Physiology of Micturition Dr.Gomathi Sivakumar MD., Senior Assistant Professor of Physiology, Government Kilpauk Medical College.

2. Micturition is the process by which the urinary bladder empties when it becomes filled. Micturition

3. Functional Anatomy of Urinary Bladder Filling of Bladder Emptying of Bladder Micturition reflex Higher centres for control Abnormalities of micturition Physiology of Micturition

4. Functional Anatomy of Bladder

5. Functions of the bladder

6. Latin word Detrudo Thrust down/Push down Detrusor muscle

7. Smooth muscle cells – low resistance electrical pathways Contracts in all directions like a toy balloon deflating from its neck Plasticity Detrusor muscle

8. Elasticity vs Plasticity

9. In humans, bladder smooth muscle appears to lack gap junctions, which would indicate the absence of electrotonic coupling between cells. Thus, bladder smooth muscle is probably “multiunit” with a 1 : 1 ratio between nerve endings and smooth-muscle cells

10. Sphincters

11. Internal sphincter(Sphincter vesicae) Circular smooth muscle fibers At bladder neck Involuntary External sphincter(Sphincter urethrae) Ring of skeletal muscles At the level of urogenital diaphragm Voluntary control Sphincters

12. N erves controlling bladder function

13. Parasympathetics Pelvic Nerves (Nervi Erigentes ) Detrusor contraction Internal sphincter relaxation Nerves of Emptying

14. Sympathetics Hypogastric Nerves Detrusor relaxation Internal sphincter contraction Nerves of Filling

15. Somatic fibres Onuf nucleus Pudendal Nerve External sphincter Voluntary control

16. Innervation of Bladder Afferent fibres Parasympathetic nerves more important in bladder function

17. Afferent Fibres Stretch ParasympatheticsPosterior column Pain and fullnessSympatheticsAnterolateral column Sensations from urethraPudendal nerve Innervation of Bladder

18. Filling of bladder

19. Filling of bladder

20. Ureteral openings

21. Vesico uretral reflux

22. Capacity of urinary bladder At birth 30 - 50 ml In adults, Sensation of bladder filling – first urge to void-150 ml Sense of fullness at 400 to 500 mL. >400 ml uncomfortable > 700 ml Uncontrollable

23. Technique used to demonstrate the intravesical pressure changes as the bladder gets filled with urine Cystometrogram A plot of intravesical pressure against the volume of fluid in the bladder Cystometry

24. Cystometry

25. Cystometrogram

26. Phenomenon of adaptation Plasticity of detrusor Law of Laplace Phase Ib  Minimal or no pressure rise

27. Law of Laplace . P=____ R 2T

28. Due to Plasticity of detrusor Law of Laplace Large volume of urine can be accommodated with minimal change in the intravesical pressure until the organ is relatively full. Independent of nervous mechanism  present in the denervated bladder also Adaptation

29. Emptying of bladder

30. Micturition reflex Higher centres for Control Emptying of bladder

31. Micturition reflex Self-regenerative”

32. Adequate stimulus 300 to 400 ml Receptors Bladder stretch receptors Afferent nerves pelvic nerves Centre Sacral segments of the cord Efferents parasympathetic fibers in pelvic nerves Response contraction of detrusor, Internal sphincter relaxation “Self-regenerative” Micturition reflex

33. If socially acceptable opportunity is not available to void Efferent impulses from the brain inhibit parasympathetic neurons in the sacral spinal cord. Voluntary contraction of the external sphincter Micturition reflex in inhibited state for a while…bladder filling continues… micturition reflexes occur more often and more powerfully. Control by Higher centres

34. Micturition waves

35. In socially acceptable condition , Voiding phase begins with a voluntary relaxation of the external urinary sphincter and also the pelvic floor Micturition reflex now continues as higher centers no longer inhibit it Emptying of Bladder Voluntary contraction of abdominal muscles  raises bladder pressure  contributes to voiding After urination, the female urethra empties by gravity. Male urethra– by contractions of bulbospongiosus

36. Higher centers controlling micturition Facilitatory centers Pons PMC Barrington centre Posterior hypothalamus Limbic system Inhibitory centers Cerebral cortex(Paracentral lobule-medial frontal lobe) Midbrain Basal ganglia

37. 1.Keep the micturition reflex partially inhibited , except when micturition is desired. 2 . Prevent urination, even if the micturition reflex occurs by tonic contraction of the external bladder sphincter until a convenient time occurs. 3 . Help to initiate a micturition reflex by facilitating sacral micturition centers and at the same time inhibit the external urinary sphincter so that urination can occur. Higher control of micturition

38. Abnormalities of micturition

39. Atonic bladder Autonomous bladder Automatic bladder Abnormal bladder

40. Deafferentation - Atonic bladder

41. sensory nerve fibers are destroyed Eg : Posterior nerve root lesion Tabes dorsalis No t ransmission of stretch signals from the bladder No detrusor reflex contraction Distended thin walled and hypotonic bladder overflow incontinence . Deafferentation - Atonic bladder

42. Denervated bladder-Autonomous bladder- Decentralised bladder

43. Both afferents and efferents are damaged. Decentralised bladder Eg : cauda equina lesion, section of pelvic nerves First it become flaccid. Then becomes small, hypertrophic bladder Denervation hypersensitization Denervated bladder-Autonomous bladder

44. Automatic bladder

45. Spinal cord is damaged above the sacral region but the sacral cord segments are still intact Automatic bladder

46. Stage of spinal shock - First few days to several weeks Micturition reflexes are suppressed Internal sphincter activity returns first before detrusor bladder tends to become overdistended Catheterization to prevent overstretching of the bladder, Automatic bladder

47. Stage of reflex recovery M icturition reflexes return but involuntary emptying occurs. Some patients can train themselves to initiate voiding by pinching or stroking their thighs, provoking micturition reflex Automatic bladder

48. Low pressure bladder filling Smooth muscle adaptation Sphincter continence Inhibited Micturition reflex Bladder emptying Spinal micturition reflex facilitated or inhibited by Higher centres To sum up…