PNB 2275 1st EditionExam # 4 Study Guide Lectures: 1 - 5Lecture 11. Renal Function- Excretes: metabolic end products, drugs, and exogenous compounds also known as xenobiotic.- Regulates: osmolarity, pH, arterial blood pressure, and essential substances such as Na, K, H, Ca, Mg, Cl, HCO3, HPO4, and water - Secretes: Renin, Erythropoietin, and active Vitamin D 2. Anatomy- 2 Kidneys (sometimes 1)- Cortex (outer area), Medulla (inner area), Calyces (minor & major), Nephron (functional unit of kidney)- Ureter (smooth muscle, peristalsis waves moves urine)- Urinary Bladder- Urethra (tube leading to out of the body)- 2 types of Nephrons:- Cortical (around 85% are these) – they handle re-absorption and have peritubular capillaries -Juxtamedullary – concentrate urine, very important job in generating concentration gradient between cortex and medulla, this is the reason we can concentrate urine, contain vasa recta and peritubular capillaries. - Renal Corpuscle: - Glomerulus: capillary network - Bowman’s capsule: parietal (exposed to air) and visceral epithelium - Afferent arteriole- brings blood into glomerulus- Efferent arteriole- drains blood out- Juxtaglomerular Apparatus- Macula Densa cells: osmoreceptors in distal tubule – responsible for sensing changes in osmolarity, particularly NaCl. - Granular Cells: responsible for secreting the enzyme Renin, of afferent arteriole- Mesangial Cells: can regulate how much filtration occurs, has contractile properties. 3. Filtration Barrier- Fenestrated capillary Epithelium- Basement Membrane- Pores formed by Podocytes- Resulting filtrate= protein- free dialysate of plasma- Once it enters bowman’s space there are no red blood cells unless there is a diseaseThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.*Flow of liquid is 1. Filtration: blood to lumen 2. Reabsorption: lumen to blood 3. Secretion: blood to lumen (movement of peritubular capillaries to the kidney) * Excretion Rate= Filtration Rate – Reabsorption + Secretion4. Filtration- Glomerular Filtration Rate (GFR): Amount of plasma filtered from the glomeruli into Bowman’s space per unit time- The average adult GFR is 125 ml/min, or 180 L. day- Filtration Fraction = GFR/ Renal plasma flow- Plasma volume enters afferent arteriole =100%- 20%volume filters , >19% of fluid is reabsorbed in the remainder of nephron- >99% of plasma enters kidney and returns to systemic circulation while <1% of volume is excreted to external environment.5. Factors that Change GFR- Forces favor filtration, Ph – glomerular capillary hydrostatic pressure- Forces opposing filtration Pfluid – bowman’s hydrostatic pressure- Π- Colloid osmotic force. - Net Filtration= Ph - Pbs - Π - GFR= Kf *(Ph - Pbs - Π) [Kf is the filtration coefficient such as ml/min/mmHg]- When conductance is high and resistance is low we get a high GFR and a higher surface area increases GFR.- Kf= GFR/Net filtration Pressure - Variable influencing Ph:- Arterial pressure, buffered by autoregulation (increase in GFR) - Afferent arteriolar resistance- Efferent arteriolar resistance - Autoregulation of GFR is maintained when blood pressure is between 80- 180 mmHg.6. GFR Regulation- Myogenic Response:- Increase in renal BP leads to constriction of afferent arteriole and vice versa- Tubuloglomerular feedback- Paracrine control- Increase in GFR (increased NaCl sensed by macula densa) leads to constriction of afferent arteriole- Hormones and Autonomic neurons- By changing resistance in arterioles - By altering the filtration coefficient 7. Tubuloglomerular Feedback- GFR increases-> flow through tubule increases-> flow past macula densa increases -> paracrine from macula densa to afferent arteriole -> afferent arteriole constricts -> resistance in afferent arteriole increases -> hydrostatic pressure in glomerulus decreases -> GFR decreases. 8. Autonomic Regulation • Sympathetic neurons innervate both afferent and efferent arterioles – Through α receptor• Triggered by a drop in systemic BP or heart attack, severe stress, circulatory shock – lead to ↓GHP (Glomerular Hydrostatic Pressure) and ↓ GFR9. Hormonal Regulation- Renin-angiotensin mechanisms- Renin is released when blood flow declines, osmolarity of the tubular fluid is too low, and sympathetic innervation - Angiotensin II restores GFR- Nephron - Vasoconstrictor- Increase filtration coefficient (potocytes and Mesangial cells) - Aldosterone secretion- CNS (thirst and ADH release) - ANP (atrial natriuretic peptide)- dilate afferent arteriole, constrict efferent arteriole, and leads to increase in GFR- inhibits sodium reabsorption which increases urine production and decreases blood volume and pressure-also inhibits renin secretion-suppresses ADH secretion-reduces sensation of thirst- promotes sodium loss at the kidneys- produced in the heart Lecture 2 1. Renal Clearance- Defined as clearance for substance “s” - Calculated value representing volume of plasma from which “S” is completely cleared per unit time- Clearance of S= (mass of S excreted per unit time)/ Plasma concentration of S- Cs= (Us*V)/Ps where Cs= Clearance of S, Us= [S] in urine V= urine volume/ unit time and Ps= [S] inplasma- To calculate renal clearance the substance has to meet the following criteria:-freely filtered out of the glomerulus, nothing is added or subtracted in or by the tubules. - Creatinine clearance can be used to estimate GFR for proximal tubules- The rate of excretion of creatinine exceeds its rate of filtration by 5 – 10%2. Principles governing the tubular reabsorption- Na is reabsorbed by active transport- Electrochemical gradient drives anion reabsorption (both transcellular and paracellular)- Water moves by osmosis, following solute reabsorption (partially through AQP1)- Concentrations of other solutes increase as fluid volume in lumen decreases. Permeable solutes are reabsorbed by diffusion.3. Proximal Tubule (PT) Reabsorption - Basolateral Side: Active Transport- Apical Side: a variety of symport, antiport, or leak - 1st half primarily reabsorbs NaHCOs and Na- organic solutes- 2nd half NaCl is mainly reabsorbed in this area, both transcellular and paracellular - No active transporters in the PT- Passive reabsorption due urea concentration gradient. - Small proteins and peptides can pass through the filtration barrier- Most filtered proteins are removed from