Crash Course :Urinary System part 2

Glomerular Filtration Rate (GFR)

Volume of filtrate formed by all glomeruli per minute (~125 mL/min); must be kept constant.

Intrinsic Autoregulation

Kidney's local ability to maintain stable GFR despite blood pressure changes via arteriole adjustments.

Extrinsic Regulation

Nervous/hormonal control overriding autoregulation during stress; reduces GFR to maintain systemic blood pressure.

Afferent Arteriole

Vessel supplying blood to the glomerulus; constriction/dilation regulates GFR.

Efferent Arteriole

Vessel draining blood from the glomerulus; constriction increases filtration pressure.

Antidiuretic Hormone (ADH/Vasopressin)

Hormone from posterior pituitary that increases water reabsorption in collecting ducts, conserving water.

Osmoreceptors

Cells in hypothalamus that detect blood concentration (osmolarity) and trigger ADH release.

Aquaporins

Water channel proteins inserted into collecting duct cells under ADH influence, allowing water reabsorption

Detrusor Muscle

Smooth muscle in bladder wall; contracts to expel urine during micturition.

Internal Urethral Sphincter

Involuntary smooth muscle sphincter at bladder-urethra junction; relaxes via parasympathetic signaling.

External Urethral Sphincter

Voluntary skeletal muscle sphincter; consciously relaxed to allow urination.

Micturition Reflex

Spinal reflex for urination, coordinated by pontine micturition center; integrates autonomic and voluntary control.

Pontine Micturition Center (PMC)

Brainstem region that coordinates timing of bladder contraction and sphincter relaxation.

Incontinence

Inability to voluntarily control urination.

Diabetes Insipidus

Condition of ADH deficiency or insensitivity, causing production of large volumes of dilute urine.