Physiological kidney Function Flashcards
Relationship between Na+ and Osmatic pressure
1 mmol Na+ + 1 mmol Cl- = 2 mOsm/L
Osmatic pressure def
Pressure applied to solution to prevent extra solvent moving across semi-permeable membrane and entering solution. Units: Osm/L
Where in relation to the cell is there a higher Na conc
Outside cell. Need ATPase pumps and energy to move across conc gradient
Extracellular Fluid Osmarility at Isotonic with cell
300 mOsm/L
Function of Blood Volume Regulation
Maintains blood pressure. Controlled by salt balance (aldosterone)
Function of Blood Osmorality Regulation
Maintains cell structure. Controlled by water retention (anti-diuretic hormone)
Salt and Water Intake and Excretion
Intake: diet and respiration (water = waste), excretion: faeces, sweat, exhalation (water only) and urine (only 1 regulated)
What is Na+ and water balance
When intake of substances = excretion
Type of transport Na+ experiences from interstitial fluid across capillary membrane
Diffusion. Down conc gradient
Type of transport Na+ experiences across tubule epithelial membrane on basolateral side
Active transport. Na+ and K+ ATPase pumps. UP conc gradient
Type of transport Na+ experiences across luminal side tubule (nephron) epithelial membrane
Diffusion (some facilitated, passive and with co-transporters eg glucose and amino acids). Down conc gradient
Region of regulated filtered Na+ uptake
Distal tubule and collecting ducts. High blood pressure = little/no uptake = most excreted in urine
Relationship between Na+ levels and blood pressure
High Na+ levels = high blood pressure
Renin-Angiotensin-Aldosterone System
3 Hormone system. Activated in cases of low blood pressure/volume. Increases filtered Na+ uptake (greater retention). Contain juxtaglomerular complex
Juxtaglomerular Complex Outline
Region where distal convoluted tubule connects to afferent and efferent arterioles. Contains mesangial cells that sense Na+ levels in blood
Granular Cells Outline
1st part of juxtaglomerular complex. Stimulated by drop in arterial blood pressure (interatrial baroreceptors), drop in plasma Na+ or drop extra cellular fluid volume (sympathetic NS). Excrete renin into blood
Macula Densa Outline
Cells in tubule part of juxtaglomerular region. Senses NaCl levels in tubule lumen
Effect of Renin in Blood
Converts Angiotensinogen to angiotensin 1
Effect of angiotensin converting enzyme (ACE) in blood
Converts angiotensin 1 to angiotensin 2
Angiotensin 2 Function
Stimulates adrenal gland to produce aldosterone
Aldosterone Function
Increases Na channels on luminal membrane and increases no. of ATPase pumps on basolateral side of distal and collecting tubes cell membranes. This increases the amount of Na out of lumen per unit time and the amount of Na reabsorbed and K+ secreted
Association between Na+ and water retention
High Na+ levels = high water retention = high blood volume = low urine volume. More Na+ excreted is more water excreted (by osmosis)
Natriuretic Peptides/Hormones
Lowers Blood Pressure by decreasing Na+ reabsorption. Inhibit renin , aldosterone, ADH and vasopressin secretion and sympathetic signalling. Produced in heart and released when muscle cells are stretched more with increased blood volume/pressure
2 Types of Natriuretic Hormones
Atrial natriuretic peptide (produced by atrial cardiac muscle cells) and brain natriuretic peptide (produced ventricular cardiac muscle cells)
Vasopressin (Anti-diuretic hormone function)
Retention of water
Anti-diuretic Hormone Action
enables distill convoluted tubule to be permeable to water by inserting aquaporin 2 on luminal side (aquaporins 3 and 4 are always on basolateral side)
Osmatic Gradient Outline
Difference in osmolality surrounding distill convoluted tubule (hypertonic interstitum)(dependent on hydration state, low diff if well hydrated, thus water isn’t reabsorbed this way if well hydrated). Osmality increases moving from outer cortex to medulla. Water moves into medulla as it moves by osmosis into hypertonic (>300 mOsm/L) space
Vasopressin Production
Produced in hypothalamus stored in posterior pituitary gland. Released when extracellular fluid is hypertonic (body is dehydrated)
Area of most K+ reabsorption
Proximal tubule and ascending loop of Henlee. Most K+ in body is in interstitial fluid due to ATPase Pumps. K+ moves through pumps (active across basolateral , out of cells, against conc gradient) and paracellular uptake (passive into cells, down conc gradient)
Aldosterone relation to K+ secretion
Aldosterone increases K+ secretion by adding more ATPase pumps on basolateral membrane increasing Na+ absorption and K+ secretion. When K+ levels are low in plasma aldosterone production reduces
Increased plasma membrane K+ levels results in
Depolarization (charge becomes positive). Lower membrane potential
Decreased plasma membrane K+ levels result in
Hyperpolarisation (charge becomes negative). Increased membrane potential
Blood pH
7.4. Ranges from 7.35 in veins - 7.45 in arteries. (veins have carbonic acid from CO2). Acidosis = below 7.35, akalosis = above 7.45 (enzymes denature)
3 ways to maintain ECF pH
Chemical buffers (bind free H+, raise pH), respiration fluxes (CO2 levels), renal (H+ in urine, HCO3- reabsorbed (used as buffer, forming carbonic acid))
relationship between HCO3- and Cl-
as one is reabsorbed the other is secreted to maintain cell charge
How H+ is secreted into urine
H+ ATPase pump
