Bladder Anatomy and Function
- Detrusor muscle: Smooth muscle responsible for bladder contraction.
- Innervated by parasympathetic neurons in the sacral spinal cord.
- Involuntary control.
- External urethral sphincter: Skeletal muscle controlling urine outflow.
- Always contracted except during urination.
- Voluntary control.
Neural Control of Voiding
- Voiding center: Located in the dorsal pons.
- Process:
- Bladder fills to sufficient volume.
- Voluntary decision to void is made.
- Parasympathetic neurons stimulate detrusor muscle contraction.
- Voluntary relaxation of external urethral sphincter.
Bladder Pressure and Volume
- Bladder pressure is not directly proportional to volume.
- Sympathetic and parasympathetic innervation affects bladder elasticity.
- Normal bladder filling involves a gradual increase in volume with minimal pressure increase.
- Urge to void occurs at a certain pressure threshold.
- Nervousness can increase bladder sensitivity, leading to earlier urge.
- Sleep involves mechanisms to maintain low bladder pressure, preventing nighttime awakenings.
Conclusion
- Urinary voiding is a complex process involving multiple muscles and neural pathways.
- Voluntary control and bladder elasticity play crucial roles in maintaining continence and initiating urination.
- Factors like stress and sleep can influence bladder function.
Problem with the Urination System