Micturition Reflex in Human Physiology

Study Notes

The micturition reflex is a complex neural process that enables the urinary bladder to store and release urine

Somatic nervous system: controls the external urethral sphincter
Autonomic nervous system: controls the detrusor muscle and internal urethral sphincter
Sensory receptors: detect bladder fullness and stretching

Storage phase
- Bladder muscles relax, and the internal urethral sphincter contracts
- Urine accumulation and storage in the bladder
Voiding phase
- Bladder muscles contract, and the internal urethral sphincter relaxes
- Urine release through the urethra

Acetylcholine (ACh): stimulates detrusor muscle contraction
Norepinephrine (NE): inhibits detrusor muscle contraction
Beta-adrenergic receptors: relax the bladder and inhibit contraction
Alpha-adrenergic receptors: stimulate the internal urethral sphincter contraction

Brain centers: pontine micturition center and sacral micturition center regulate the reflex
Spinal cord: integrates sensory information and transmits signals to the brain centers

Disruptions in the micturition reflex can lead to urinary incontinence, retention, or other elimination disorders

The micturition reflex is a complex neural process that enables the urinary bladder to store and release urine.

The somatic nervous system controls the external urethral sphincter.
The autonomic nervous system controls the detrusor muscle and internal urethral sphincter.
Sensory receptors detect bladder fullness and stretching.

Brain centers, including the pontine micturition center and sacral micturition center, regulate the reflex.
The spinal cord integrates sensory information and transmits signals to the brain centers.

Disruptions in the micturition reflex can lead to urinary incontinence, retention, or other elimination disorders.

The kidneys filter waste and excess fluids from the blood, regulating electrolyte balance and blood pressure.
The nephron is the functional unit of the kidney, consisting of glomerulus, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.

Filtration: Removing waste products from the blood, such as urea, creatinine, and ammonia.
Reabsorption: Returning essential nutrients, electrolytes, and water back into the bloodstream.
Secretion: Removing excess substances, such as potassium and hydrogen ions, from the blood.
Regulation of electrolyte balance: Maintaining homeostasis of sodium, potassium, calcium, and magnesium levels.
Regulation of acid-base balance: Maintaining pH balance by controlling hydrogen ion levels.
Regulation of blood pressure: Controlling blood pressure through the renin-angiotensin-aldosterone system.
Production of hormones: Producing erythropoietin, calcitriol, and renin.

Blood tests: Include blood urea nitrogen (BUN), creatinine, and electrolyte levels (sodium, potassium, calcium).
Urinalysis: Includes pH, specific gravity, proteinuria (protein in urine), and hematuria (blood in urine).
Imaging studies: Include ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI).

Acute kidney injury (AKI): Sudden loss of renal function, often reversible.
Chronic kidney disease (CKD): Progressive loss of renal function, often irreversible.
End-stage renal disease (ESRD): Complete loss of renal function, requiring dialysis or transplantation.