Neural and Hormonal Regulation of GFR

Neural Regulation of GFR:

When the blood pressure increase the sympathetic nerve fibers release nor epinephrine which causes constriction of blood vessel thus decreasing GFR.

Hormonal Regulation of GFR:

Two hormones, Angiotensin II reduce GFR and atrial natriuretic peptide (ANP) increase GFR

Substance Filtered Reabsorbed Urine

Water 180 liter 178 liter 1-2 liter

Protein 2 g 1.9 g .1 g

Sodium ion 579 g 575 g 4 g

Chloride ion 640 g 633.7 g 6.3 g

Bicarbonate ion 275 g 274.9 g 0.03 g

glucose 162 g 162 g 0 g

urea 54 g 24 g 30 g

Potassium ion 29.6 g 29.6 g 2 g

Uric acid 8.5 g 7.7 g .8 g

Creatinine 1.6 g 0 g 1.6 g

Substances filtered reabsorbed and excreted in urine

Tubular Reabsorption and SecretionReabsorption: Normally 99% of filtered water is reabsorbed Solutes that are reabsorbed include glucose, amino acid,

urea and ion such as sodium, potassium, calcium, chloride, bicarbonate and phosphate.

Secretion: Substance that are secreted include: hydrogen ion,

potassium, ammonium ion, creatinine and certain drugs. Two important outcomes of Tubular secretion:

Secretion of H- ion help to control body PH Secretion of other substance eliminate them from the body

Reabsorbtion and secretion in the PCT 65% of Na+ is reabsorbed 65% of H2O is reabsorbed

65% K+

100% Glucose 100% amino acid 50% Cl-

90% of filtered bicarbonate (HCO3-)

Secretion: Variable amount of H+ NH4- and urea and a small

amount of Creatinine is secreted in the PCT.

Reabsorbtion and Secretion in the LOH

Reabsorbtion: 25% Na+

15% H2O

20-30 % K+

35 % Cl-

10-20% HCO3-

Secretion:

Variable amount of urea is secreted in the LOH

Hormonal Regulation of Tubular Reabsorbtion and Tubular Secretion

Angiotension II Aldosterone Antidiuretic hormone Natriuretic peptide Parathyroid

Antidiuretic hormone

ADH (antidiuretic hormone) makes collecting ducts more permeable to water, it helps produce concentrated urine

-efferent arterioles

Effect of aldosterone on DCT and Collecting Duct

BP causes angiotensin II formation angiotensin II stimulates adrenal cortex adrenal cortex secretes aldosterone aldosterone promotes Na+ reabsorption Na+ reabsorption promotes water reabsorption water reabsorption urine volume BP drops less rapidly

Effect of atrial natriuretic factor (ANF)

BP stimulates right atrium Atrial walls stretches atrium secretes ANF ANF promotes Na+ and water excretion BP drops

Ureters• Tubes that convey urine from kidney to the urinary bladder• 25-30 cm long and 3mm in diameter• Start from pelvis, enter into pelvic cavity and passes obliquely

through the posterior wall of the bladder

Structure consists of three layers of tissue Outer fibrous tissue Middle smooth muscle layer Inner mucosa lined with transitional epithelium

Functions:• Propel urine from kidney into the bladder by peristaltic contraction of

smooth muscle layer• The wave of contraction occur in minor calyces• Peristaltic wave occur several time per minutes and send little spurts

of urine into bladder.

Urinary bladder:

It is a reservoir for urine whose size and position vary, depending on the amount of urine it contain

Lie in the pelvic cavityStructure:• Roughly pear shaped structure but more oval when

filled with urine.• The posterior surface is called base and the point

where the bladder open into urethra is called neck• The superior surface of the bladder is covered by

peritoneum• Posteriorly bladder is surrounded by uterus in female

and rectum in male

Outer loose connective tissue layer

Mucosa Middle smooth muscle and elastic tissue

rugae

Trigone NeckUrethral sphincter

The bladder wall composed of three layers

1. Outer layer of loose connective tissue containing blood, lymph vessels and nerve

2. The middle layer consists of inter-lacing mass of smooth muscle fibers and elastic tissue. These are called Detrusor muscle. It contracts to empty urine

3. The mucosa lined with transitional epithelium When the bladder is empty the inner layer is arranged in

folds or rugae which disappear when bladder is full The total capacity of bladder is more then 600 ml and

awareness of desire to urinate is initiated at 300-400ml The three orifices of the bladder wall form a triangle or

trigone.

• The upper two pore is the opening of ureter and the lower one is the urethra

• At the site where the urethra emerge is a thick smooth muscle layer called urethral sphincter.

Reflex control of micturition when conscious effort cannot override the reflex action..

• http://highered.mheducation.com/sites/0072507470/student_view0/chapter26/animation__micturition_reflex.html

Control of micturition after bladder control is established