Micturition (The Guyton and Hall physiology)

The process by which the urinary bladder empties when it becomes filled.

It is a reflex process
ANATOMY OF URINARY BLADDER BODY = in which urine is collected
NECK = funnel shaped extension and connecting with the urethra.
URETHRAL SPHINCTER.
1. INTERNAL URETHRAL SPHINCTER.
made up of detrusor muscle

2. EXTERNAL URETHRAL SPHINCTER.
made up of skeletal muscle fiber.
EXTERNAL URETHRAL SPHINCTER is responsible for voluntary control of micturition
The walls of the ureter contain smooth musle and are innervated by both sympathetic and parasympathetic nerves.



Parasympathetic stimulation increases peristaltic contraction .

Sympathetic stimulation inhibited MICTURITION REFLEX Filling of urinary bladder 300 – 400 ml
|
stimulation of sensory stretch receptors
present on the wall of bladder
|
Afferent impulses pass via pelvic nerve
|
reaches the sacral segments of spinal cord
|
synapses with postganglionic neuron
|
Efferent impulses via pelvic nerve
causes contraction of detrusor muscle
and relaxation of internal sphincter
|
flow of urine in to urethra and
stimulation of stretch receptors present
in urethra
|
it send afferent impulses via pelvic nerve
|
Inhibition of pudendal nerve
|
Relaxation of external sphincter
|
voiding of urine
Once a micturition begins ,, it is a “self regenerative “.
THAT IS,
the initial contraction of bladder
further activates the receptors to
causes still further increase in sensory
impulses from the bladder and urethra.


These impulses in turn further increases in reflex contraction of bladder.

1. MICTURITION Source: The Guyton and Hall physiology Maryam Fida (o-1827)

2. The process by which the urinary bladder empties when it becomes filled. It is a reflex process MICTURITION

3. BODY = in which urine is collected NECK = funnel shaped extension and connecting with the urethra. URETHRAL SPHINCTER. 1. INTERNAL URETHRAL SPHINCTER. made up of detrusor muscle 2. EXTERNAL URETHRAL SPHINCTER. made up of skeletal muscle fiber . EXTERNAL URETHRAL SPHINCTER is responsible for voluntary control of micturition ANATOMY OF URINARY BLADDER

4. The walls of the ureter contain smooth musle and are innervated by both sympathetic and parasympathetic nerves. Parasympathetic stimulation increases peristaltic contraction . Sympathetic stimulation inhibited contraction .

5. NERVE SUPPLY TO BLADDER AND SPHINCTERS. NERVE ON DETRUSOR MUSCLE ON INTERNAL SPHINCTER ON EXTERNAL SPHINCTER FUNCTION SYMPATHETIC NERVE Relaxation constriction Not supplied Filling of bladder PARASYMPATHETIC NERVE contraction relaxation Not supplied Emptying of bladder SOMATIC NERVE Not supplied Not supplied constriction Voluntary control of micturition

6. Filling of urinary bladder 300 – 400 ml | stimulation of sensory stretch receptors present on the wall of bladder | Afferent impulses pass via pelvic nerve | reaches the sacral segments of spinal cord | synapses with postganglionic neuron | Efferent impulses via pelvic nerve MICTURITION REFLEX

7. causes contraction of detrusor muscle and relaxation of internal sphincter | flow of urine in to urethra and stimulation of stretch receptors present in urethra | it send afferent impulses via pelvic nerve | Inhibition of pudendal nerve | Relaxation of external sphincter | voiding of urine

8. Once a micturition begins ,, it is a “self regenerative “. THAT IS, the initial contraction of bladder further activates the receptors to causes still further increase in sensory impulses from the bladder and urethra. These impulses in turn further increases in reflex contraction of bladder.

9. This cycle is continues repeatedly untill the force of contraction of bladder reaches the maximum and the urine is voided out completely.

10. The micturition reflex is an automatic spinal cord reflex….. but it can be inhibited and facilitated by centres in the brain…. 1…. Strong facilitive and inhibitory centres in the brain stem, located mainly in pons . 2…. Several centers located in the cerebral cortex that are inhibited. HIGHER CENTRES FOR MICTURITION

11. It is a graphical recording shows changes in intra vesicular pressure as the bladder fills with urine…. CYSTOMETROGRAM

12. When there is no urine in the bladder, the intravesicular pressure is about 0 When about 30 to 50 milliliters of urine is collected, the pressure rises to 5 to 10 centimters of water. Additional urine 200 to 300 milliliters collect, causes rise in pressure very little. This constant level of pressure is caused by intrinsic tone of the bladder wall itself. Beyond 300 to 400 milliliters, collection of more urine in the bladder causes the pressure to rise rapidly.

13. These pressure peaks are called MICTURITION WAVES in the cystometrogram and are caused by the micturition reflex.

14. ATONIC BLADDER 2) AUTOMATIC BLADDER 3) UNINHIBITED NEUROGENIC BLADDER ABNORMALITIES OF MICTURITION

15. It is the urinary bladder with loss of tone in detrusor muscle. due to destruction of sensory nerve fibers from the bladder to the spinal cord are destroyed, so transmission of stretch signals from the bladder is prevented . However there is efferent fibers from the cord to the bladder is intact. ATONIC BLADDER

16. The bladder fills to capacity and overflows a few drops at a time through the urethra.. This is called ‘ OVERFLOW INCONTINENCE ‘. CAUSES 1. Crush injury to the sacral region of the spinal cord. 2 . Damage to the dorsal root nerve fibers. Example. Syphilis can causes constrictive fibrosis around the dorsal root nerve fibers and destroy them. This condition is called TABES DORSALIS and bladder condition is called TABETIC BLADDER.

17. It refers to the urinary bladder that is characterized by hyperactive micturition reflex. In this condition, the voluntary control of micturition is lost, so even with the small amount of urine collected in the urinary bladder, micturition reflex occurs resulting in emptying of urine. CAUSE Spinal cord damage above the sacral region. AUTOMATIC BLADDER

18. It is the urinary bladder with frequent and uncontrollable micturition . It is caused due to partial damage in the spinal cord or the brain stem that interrupts most of the inhibitory signals. The facilitative impulses passing continually down the cord keep the sacral centres so excitable. So, there is frequent micturition … UNINHIBITED NEUROGENIC BLADDER