7.3 - regulation functions of the kidney

HORMONES

  • chemical messengers (carry messages from one part of the body to another)

  • travel via the blood to target organs

  • speed up or slow down certain body functions (ex. heart rate, growth, digestion etc)

  • make long term adjustments (puberty) as opposed to the nervous system which makes short term adjustments (quick responses)

POSTERIOR PITUITARY: below the hypothalamus

  • connected to the hypothalamus by nerve tracts (bundles of neurons)

  • stores and secretes (releases) hormones produced by the hypothalamus

ANTERIOR PITUITARY

  • not connected to the posterior pituitary

  • produces its own hormones but is controlled by the hypothalamus

  • hypothalamus produces releasing hormones which cause the anterior pituitary to secrete specific hormones

  • these hormones may affect body tissues or other endocrine glands

  • thus, the hypothalamus and the anterior pituitary are considered the neuro-endocrine control centre

  • anterior pituitary is considered the master gland

ADRENAL GLANDS

MEDULLA

  • secretes adrenalin and noradrenalin (epinephrine and norepinephrine)

  • initiates the fight or flight response

CORTEX

  • secretes cortisol (promotes healing)

  • secretes aldosterone for Na+ reabsorption

REGULATION OF KIDNEYS - BLOOD VOLUME (WATER BALANCE)

  • blood volume is directly controlled by kidneys (control how much water is reabsorbed and how much is removed as urine)

  • increase in reabsorption of water leads to an increase of blood volume

  • decrease in reabsorption of water leads to a decrease of blood volume

  • adjusted by combination of hormones and nervous system (kidney changes water reabsorption based on hormones and nerve signals)

ADH: anti-diuretic hormone

  • released by the posterior pituitary gland

  • causes the distal convoluted tubule and collecting duct to be more permeable to water. more water is reabsorbed which can increase/maintain blood volume

NO ADH PRESENT: collecting duct is NOT permeable to water, large volume of urine is produced

ADH PRESENT: collecting duct is permeable to water, small volume of urine is produced

produced by the body when its dehydrated to reabsorb/conserve more water

ALDOSTERONE

  • released by adrenal glands

  • causes reabsorption of Na+ from the distal convoluted tubule

  • this causes blood to be hypertonic (more solutes in blood), causing more water to be reabsorbed into the blood from the nephron

JUXTAGLOMERULAR APPARATUS AND BP

  • region of afferent arteriole that monitors BP

  • increase in fluid loss (filtrate) will lead to decrease in BP

  • decreased BP automatically leads to less fluid being filtered (less force pushing fluid out of the glomerulus)

  • if BP is low, juxtaglomerular cells release renin (enzyme)

  • renin stimulates the conversion of angiotensinogen (from the liver) into angiotensin

ANGIOTENSIN

angiotensin causes:

  1. release of vasoconstriction

  2. stimulates release of aldosterone from the adrenal cortex

VASOCONSTRICTION

  • reduces the diameter of blood vessel which helps increase blood pressure (the force)

ALDOSTERONE

  • causes Na+ reaction

  • Na+ reaction leads to increase blood volume and increased BP

MAINTENANCE OF pH

  • chemoreceptors in the carotid and aortic bodies stimulate the respiratory centre when blood pH decrease

  • but the respiratory can only maintain minor fluctuations in pH

  • the kidneys maintain the blood’s constant pH

BLOOD PH IS TOO LOW (ACIDIC)

  • some H+ ions are excreted in the DCT with ammonia (NH3)

  • NH3 produced in the tubule cells from the deamination (removal of amino group) of amino acids

NH3 + H+ → NH4

  • and some bicarbonate ions are reabsorbed into the blood

H+ + HCO3 → H2CO3 → Co2 + H2O (removes hydrogen ions)

BLOOD PH IS TOO HIGH (BASIC)

  • less NH4 will be excreted and less HCO3 will be reabsorbed (from urine/nephron)

  • phosphate will also buffer blood