Questions? Homework due in lab 6. PreLab #6 HW 15 & 16 (follow directions, 6 points!)

Transcription

1 Questions? Homework due in lab 6 PreLab #6 HW 15 & 16 (follow directions, 6 points!)

2 Part 3

3 Variations in Urine Formation Composition varies Fluid volume Solute concentration

4 Variations in Urine Formation Water intake must equal water loss Kidney regulates water loss by producing: Hypotonic urine (dilute) Hypertonic urine (concentrated)

5 Countercurrent Mechanism Role of countercurrent mechanisms Establish and maintain an osmotic gradient Creates hypertonic interstitial fluid within kidney medulla Hypertonic interstitial fluid allows the kidneys to vary urine concentration

6 Osmolality of interstitial fluid (mosm) Active transport NaCI Cortex Passive transport Water impermeable NaCI NaCI Countercurrent multiplier The long loops of Henle of the juxtamedullary nephrons create the medullary osmotic gradient. Loop of Henle NaCI NaCI Outer medulla Inner medulla Figure 25.16a

7 Formation of Concentrated Urine Depends on the medullary osmotic gradient and the ability to alter permeability of the collecting tubules ADH triggers reabsorption of in the collecting tubules Osmotic gradient drives water from filtrate into blood

8 Active transport Passive transport Descending limb of loop of Henle Collecting duct DCT Cortex NaCI Outer medulla NaCI NaCI Urea Inner medulla Urea (b) Maximal ADH Small volume of concentrated urine Figure 25.17b

9 Formation of Dilute Urine Filtrate is diluted in the ascending Loop of Henle In the absence of ADH, dilute filtrate continues into the renal pelvis as dilute urine

10 Active transport Passive transport Collecting duct Descending limb of loop of Henle DCT Cortex NaCI Outer medulla NaCI NaCI Inner medulla Urea (a) Absence of ADH Large volume of dilute urine Figure 25.17a

11 Regulation of Water Output Influence of ADH Water reabsorption in collecting tubules is dependent upon ADH release ADH dilute urine and volume of body fluids ADH concentrated urine

12 Osmolality Na + concentration in plasma Stimulates Plasma volume BP (10 15%) Osmoreceptors in hypothalamus Negative feedback inhibits Stimulates Baroreceptors in atrium and large vessels Inhibits Stimulates Posterior pituitary Releases ADH Antidiuretic hormone (ADH) Collecting ducts of kidneys Targets Effects Water reabsorption Results in Osmolality Plasma volume Scant urine Figure 26.6

13 Acid-Base Balance ph affects all functional proteins and biochemical reactions in the body Regulation prevents changes in body s internal environment Alkalosis or alkalemia: arterial blood ph >7.45 Acidosis or acidemia: arterial ph < 7.35

14 Acid-Base Balance Concentration of hydrogen ions is regulated by 1. Chemical buffer systems Rapid, first line of defense 2. Brainstem respiratory centers Acts within 1 3 minutes 3. Renal mechanisms Most potent Requires hours to days to affect ph changes

15 Acid-Base Balance Lungs Regulate carbonic acid levels by CO 2 manipulation Kidneys Selectively secrete and reabsorb to maintain ph

16 Acid-Base Balance Most important renal mechanisms: Conserving (reabsorbing) HCO 3 Excreting HCO 3 Secretion of H + H + secretion occurs in the PCT and in collecting tubules

17 Acid-Base Balance Examples Respiratory Acidosis Kidneys Respiratory Alkalosis Kidneys

18 More on Compensation Uncompensated ph abnormal and either CO 2 or HCO 3 - is off The other system has not started to compensate at all Partially compensated ph is abnormal and both CO 2 and HCO 3 - are off The other system is trying to compensate Fully compensated ph is normal and both CO 2 and HCO 3 - are off The other system has corrected the ph but there is still and acid base imbalance since CO 2 and HCO 3 - are abnormal Lets practice Urinary 31 #21-24

19 Variations in Blood Pressure Activity of kidney related to variations in blood pressure Blood pressure and blood volume are related Blood volume is controlled by Solute concentration Water regulation

20 Variations in Blood Pressure Renal mechanisms influencing blood pressure ADH Water Renin-angiotensin mechanism Sodium Potassium

21 Antidiuretic Hormone (ADH) Plasma osmolarity Increase osmoreceptors stimulated thirst & ADH secretion water reabsorption (decreased urine output) increased blood volume increased blood pressure Causes?

22 Aldosterone Aldosterone stimulates K + secretion and Na + reabsorption Changes in plasma sodium levels affect Plasma volume, blood pressure

23 Aldosterone Regulation of sodium balance Na + reabsorption 65% is reabsorbed in the proximal tubules 25% is reclaimed in the Loops of Henle Aldosterone active reabsorption of remaining Na + in DCT and collecting ducts Water follows Na +

24 Aldosterone Renin-angiotensin mechanism is the main trigger for aldosterone release Specialized cells of JGA secrete renin in response to Sympathetic nervous system stimulation Filtrate osmolality (decreased sodium) Stretch (due to blood pressure)

25 Efferent arteriole Glomerular capsule Glomerulus Afferent arteriole Efferent arteriole Parietal layer of glomerular capsule Capsular space Foot processes of podocytes Podocyte cell body (visceral layer) Red blood cell Proximal tubule cell Juxtaglomerular apparatus Macula densa cells of the ascending limb of loop of Henle Extraglomerular mesangial cells Granular cells Afferent arteriole Juxtaglomerular apparatus Renal corpuscle Lumens of glomerular capillaries Endothelial cell of glomerular capillary Mesangial cells between capillaries Figure 25.8

26 Aldosterone Renin catalyzes the production of angiotensin II Prompts aldosterone release from the adrenal cortex Targets cells of DCT and collecting ducts Initiates sodium reabsorption Causes systemic vasoconstriction

27 K + (or Na + ) concentration in blood plasma* Renin-angiotensin mechanism Adrenal cortex Stimulates Negative feedback inhibits Aldosterone Releases Targets Kidney tubules Effects Na + reabsorption K + secretion Restores Homeostatic plasma levels of Na + and K + Figure 26.8

28 Systemic blood pressure/volume Stretch in afferent arterioles (+) Filtrate NaCl concentration in ascending limb of loop of Henle (+) Inhibits baroreceptors in blood vessels (+) Granular cells of kidneys Renin Release (+) Sympathetic nervous system (+) Systemic arterioles Catalyzes conversion Causes Angiotensinogen (from liver) Converting enzyme (in lungs) Angiotensin I Vasoconstriction Results in Peripheral resistance (+) (+) Angiotensin II (+) (+) Posterior pituitary Releases Systemic arterioles Causes Vasoconstriction Results in Peripheral resistance Adrenal cortex Aldosterone Distal kidney tubules Causes Na + (and ) reabsorption Blood volume Secretes Targets Results in Blood pressure ADH (antidiuretic hormone) (+) Collecting ducts of kidneys (+) stimulates Causes reabsorption Renin-angiotensin system Neural regulation (sympathetic nervous system effects) ADH release and effects Figure 26.10

29 Renin-Angiotensin System Increases blood volume Vasoconstriction Increase BP Aldosterone produced in response to: Decreased blood volume Decreased BP Low plasma sodium High plasma potassium

30 Factors Affecting Urine Volume Increased temperature Increases vasodilation and perspiration Decreases blood flow to kidneys Decreased temperature Increases blood flow to kidneys

31 Diuretics Chemicals that increase urine output Osmotic diuretics Substances not reabsorbed Glucose in a diabetic patient ADH inhibitors Alcohol and water Substances that inhibit Na + reabsorption Caffeine, thiazides, loop inhibitors Potassium levels are affected by some diuretics

32 Factors Affecting Urine Output blood pressure blood solute concentration plasma proteins Psychological factors Anxious increased frequency and urge Fright decreases urine output volume

33 Activities Regulation of Sodium Balance Worksheet Urinary 26 Complete 1, 2, 4, & 5 Urinary 27 Complete 2, 3, & 5 Show me completed worksheets