Micturition Reflex and Common Disorders of Urinary System PDF

Micturition Reflex and Common Disorders of Urinary System Dr Pallav Sengupta Assistant Professor of Physiology www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES Learning objectives...

Micturition Reflex and Common Disorders of Urinary System Dr Pallav Sengupta Assistant Professor of Physiology www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES Learning objectives Define and describe process of micturition Briefly describe common disorders of micturition Explain common disorders of urinary system Micturition Reflex Micturition is the process by which the urinary bladder empties when it becomes filled. Kidneys form the urine continuously but voiding of urine (micturition) is a periodic process.  Muscles of bladder Detrusor muscle: Smooth muscle of the bladder Rugae: Mucosa of the bladder formes folds known as rugae Internal sphincter: At the neck of the bladder the internal sphincter is present. Its natural tone keeps the bladder neck and the posterior urethra empty of urine. External sphincter The urethra passes a layer of skeletal muscle called the external sphincter. This muscle is under the voluntary control Urinary bladder  Neural Innervation of Urinary bladder Supplied with sensory and motor nerves. Both sympathetic and parasympathetic. The parasympathetic fibers (pelvic nerve / nerve of emptying) stimulatory effect on the bladder contraction. The sympathetic fibers (hypogastric nerve / nerve of filling) is uncertain. stimulate the blood vessels. The somatic nerve supply (pudic or pudental nerve) Urinary bladder and its innervation  Process of micturition 1. Transport of urine through the ureter The detrusor muscle tone in the bladder wall tends to compress the ureter (follows rhythmic contraction of ureter) Prevents backflow of urine Pressure builds up in the bladder.  Process of micturition … contd. 2. Filling of the bladder During the filling phase, the bladder pressure is low, and the sphincteric pressure is high. When there is no urine in the bladder, the intravesicle pressure (IVP) is about 0. But by the time 30 to 50ml of urine has collected, the pressure rises 5 to 10cm of water. Additional urine, 200 to 300ml, can collect with only a small additional rise in pressure. Under the influence of sympathetic nerve.  This constant level of pressure is caused by intrinsic tone of the bladder wall itself. Beyond 300 to 400ml collection of more urine in bladder causes the pressure to rise rapidly (desire to urination). Above 800 ml = pain Above 1000 ml = involuntary cystometrogram  Process of micturition … contd. 3. Emptying of the bladder: Micturition 1. Rise in bladder pressure above a threshold mark 2. Fall in sphincter pressure 3. Contraction of diaphragm and abdominal muscles. Relaxation of diaphragm and abdominal muscles and contraction of the external sphincter are important also for the termination of micturition. 4. Under the influence of parasympathetic nerve.  Control by higher centres Strong facilitatory and inhibitory centers in the brain stem located mainly in the pons. Several centers located in the cerebral cortex that are inhibitory but can become excitatory  Disorders of micturition Atonic bladder The sensory nerve fibers from the bladder to the spinal cord are destroyed Person loses bladder control. The bladder fills to capacity and overflows a few drops at the time through the urethra. This is called overflow incontinence. Automatic bladder The bladder fills to a threshold, and then empties to a considerable extent as a result of vesicle contraction. This happens without any voluntary control. Called automatic bladder. Neurogenic bladder This is a term used for an irritable bladder, which empties small quantities of urine at a time repeatedly. This condition results from partial damage in the spinal cord or the brain stem that interrupts most of the inhibitory signals.  Common disorders of urinary system Analgesic neuropathy: Long term use of pain relievers particularly non steroidal anti inflammatory drugs (NASAIDs) Ibuprofen, naproxyn particularly when combined with caffeine Chronic renal failure: Progressive kidney diseases Progression can be controlled by treating underlying causes like hypertension, high cholesterol End stage renal failure can only treated with dialysis/renal transplantation Common disorders of urinary system Diabetes insipidus Too little ADH, insensitive kidney to ADH Large urinary output. Patients often become dehydrated Chances of brain damage due to low sodium level Glomerulonephritis Inflammation of the glomerulus Damage of filter Blood, Blood cells appear in the urine Decreased removal of waste products, loss of electrolyte balance Hemolytic uremic syndrome Caused by bacteria E. coli (undercooked meat) Bacterial toxin led to damage of RBCs. Lodging of RBCs in the blood vessels of kidney. Preventing blood flow to the nephrons  Learning Resources Text Book: Colbert BJ, Ankney J, Lee KT. Anatomy and Physiology for health professions. 2nd edition, Pearson education; 2011. ISBN-13: 978-0-13-506077-3. Chapter 17, pp. 446-449. Power-point presentation in the moodle www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES