FUNCTION OF THE KIDNEY This section is a highly simplified analysis of renal function, including analysis of blood flow through the kidney and of the formation of glomerular filtrate. Then the changes that occur in the filtrate as it passes through the tubules are calculated. However, only four substances are considered as they pass through the tubules: sodium, potassium, urea, and water. The control effects of angiotensin, aldosterone, antidiuretic hormone, and nervous signals are also presented. Encapsulation grouping component containing all the components in the Kidney Model. The inputs and outputs of the Kidney Model must be passed by this component. KD1: The perfusion pressure of the kidneys (PAR) is calculated by subtracting any pressure gradient caused by renal arterial constriction (GBL) from the systemic arterial pressure (PA). This block allows one to simulate Goldblatt hypertension. KD2: This block allows one to simulate other experiments. The factor (RAPRSP), when set to any value besides zero, will fix the renal perfusion pressure (PAR) to an exact value that will not change regardless of changes in systemic arterial pressure. The factor (RFCDFT) allows one to test the hypothetical condition that function of the kidney over a long period of time asymptotically approaches normal output function regardless of changes in arterial pressure. That is, PAR drifts continually back toward the normal mean value of 100 rather than being determined by the systemic arterial pressure, simulating shift of the renal function curve. This is used to test theories that in the long run kidney output function can be independent of arterial pressure. KD2: This block allows one to simulate other experiments. The factor (RAPRSP), when set to any value besides zero, will fix the renal perfusion pressure (PAR) to an exact value that will not change regardless of changes in systemic arterial pressure. The factor (RFCDFT) allows one to test the hypothetical condition that function of the kidney over a long period of time asymptotically approaches normal output function regardless of changes in arterial pressure. That is, PAR drifts continually back toward the normal mean value of 100 rather than being determined by the systemic arterial pressure, simulating shift of the renal function curve. This is used to test theories that in the long run kidney output function can be independent of arterial pressure. KD1: The perfusion pressure of the kidneys (PAR) is calculated by subtracting any pressure gradient caused by renal arterial constriction (GBL) from the systemic arterial pressure (PA). This block allows one to simulate Goldblatt hypertension. KD2: This block allows one to simulate other experiments. The factor (RAPRSP), when set to any value besides zero, will fix the renal perfusion pressure (PAR) to an exact value that will not change regardless of changes in systemic arterial pressure. The factor (RFCDFT) allows one to test the hypothetical condition that function of the kidney over a long period of time asymptotically approaches normal output function regardless of changes in arterial pressure. That is, PAR drifts continually back toward the normal mean value of 100 rather than being determined by the systemic arterial pressure, simulating shift of the renal function curve. This is used to test theories that in the long run kidney output function can be independent of arterial pressure. KD57, KD58, KD59, KD60, KD61, KD62, KD63, KD64, KD65, KD66, and KD67: Calculation of an autoregulatory feedback factor that affects the degree of constriction of both afferent and efferent arterioles (RNAUG2) which is the output of Block 64. This feedback effect, and the resistance of the afferent and efferent arterioles, increases in proportion to the calculation from these blocks and in response to the flow rate of fluid in the tubules at the macula densa (MDFLW) which is the input to Block 57. Blocks 57, 58, and 59 calculate the sensitivity of this feedback mechanism, and the sensitivity control factor is RNAUGN in Block 58. Blocks 60 and 61 calculate the time constant of development of this feedback in the arterioles after any change in rate of flow (MDFLW) at the macula densa. The time constant of this feedback response is RNAGTC in Block 60. The value RNAULL is the lower limit to the autoregulatory response (RNAUG1) as set by Block 62. RNAUUL is the upper limit, as set by Block 63. Block 65, 66, and 67 calculate obliterative adaptation of this feedback response in case such as this does occur. The sensitivity of this, RNAUAD, in Block 66 is set at zero because many persons believe there is no such decay of this feedback response. Yet others have postulated such a feedback response, in which case RNAUAD would then become the factor that sets the time constant of the loss of the feedback response with time. The output of this total system from Block 14 is RNAUG2. NB - REMOVED DAMPING FROM KD57-KD61!!!!!!!!! KD57, KD58, KD59, KD60 and KD61: Calculation of an autoregulatory feedback factor that affects the degree of constriction of both afferent and efferent arterioles (RNAUG2) which is the output of Block 64. This feedback effect, and the resistance of the afferent and efferent arterioles, increases in proportion to the calculation from these blocks and in response to the flow rate of fluid in the tubules at the macula densa (MDFLW) which is the input to Block 57. Blocks 57, 58, and 59 calculate the sensitivity of this feedback mechanism, and the sensitivity control factor is RNAUGN in Block 58. Blocks 60 and 61 calculate the time constant of development of this feedback in the arterioles after any change in rate of flow (MDFLW) at the macula densa. The time constant of this feedback response is RNAGTC in Block 60. KD62 and KD63: The value RNAULL is the lower limit to the autoregulatory response (RNAUG1) as set by Block 62. RNAUUL is the upper limit, as set by Block 63. KD64: Calculation of an autoregulatory feedback factor that affects the degree of constriction of both afferent and efferent arterioles (RNAUG2) which is the output of Block 64. This feedback effect, and the resistance of the afferent and efferent arterioles, increases in proportion to the calculation from these blocks and in response to the flow rate of fluid in the tubules at the macula densa (MDFLW) which is the input to Block 57. KD65, KD66, and KD67: Block 65, 66, and 67 calculate obliterative adaptation of this feedback response in case such as this does occur. The sensitivity of this, RNAUAD, in Block 66 is set at zero because many persons believe there is no such decay of this feedback response. Yet others have postulated such a feedback response, in which case RNAUAD would then become the factor that sets the time constant of the loss of the feedback response with time. The output of this total system from Block 14 is RNAUG2. NB - REMOVED DAMPING FROM KD57-KD61!!!!!!!!! Containment grouping component for "autonomic_effect_on_AAR", "angiotensin_effect_on_AAR", "AAR_calculation" and "atrial_natriuretic_peptide_effect_on_AAR". KD10, KD11, KD12, and KD13: Calculation of the effect of autonomic stimulation (AUM) on afferent arteriolar resistance (AUMK). A sensitivity controller for this is in Block 11 (ARF). A limit is in Block 13 equal to 0.8. KD10, KD11, KD12, and KD13: Calculation of the effect of autonomic stimulation (AUM) on afferent arteriolar resistance (AUMK). A sensitivity controller for this is in Block 11 (ARF). A limit is in Block 13 equal to 0.8. KD10, KD11, KD12, and KD13: Calculation of the effect of autonomic stimulation (AUM) on afferent arteriolar resistance (AUMK). A sensitivity controller for this is in Block 11 (ARF). A limit is in Block 13 equal to 0.8. KD3, KD7 and KD8: Calculation of a temporary value for the effect of angiotensin on the afferent arteriolar resistance (ANMAR). The angiotensin-related factors that affect the afferent arteriolar resistance are an angiotensin multiplier factor (ANM), and an angiotensin multiplier sensitivity controller (ANMAM). KD3, KD7 and KD8: Calculation of a temporary value for the effect of angiotensin on the afferent arteriolar resistance (ANMAR). The angiotensin-related factors that affect the afferent arteriolar resistance are an angiotensin multiplier factor (ANM), and an angiotensin multiplier sensitivity controller (ANMAM). KD3, KD7 and KD8: Calculation of a temporary value for the effect of angiotensin on the afferent arteriolar resistance (ANMAR). The angiotensin-related factors that affect the afferent arteriolar resistance are an angiotensin multiplier factor (ANM), and an angiotensin multiplier sensitivity controller (ANMAM). KD9: Calculation of a temporary value for the afferent arteriolar resistance (AAR1), except for the effect of atrial natriuretic peptide on this resistance which is calculated later. The factors that affect the afferent arteriolar resistance are the angiotensin multiplier on afferent arterioles (ANMAR), an autonomic multiplier factor for nervous control of afferent resistance (AUMK), an autoregulatory feedback multiplier effect on afferent arteriolar resistance (RNAUG2), a myogenic autoregulation factor (myogrs), and a basic afferent arteriolar resistance factor (AAR1) which allows for intrarenal alterations. KD9: Calculation of a temporary value for the afferent arteriolar resistance (AAR1), except for the effect of atrial natriuretic peptide on this resistance which is calculated later. The factors that affect the afferent arteriolar resistance are the angiotensin multiplier on afferent arterioles (ANMAR), an autonomic multiplier factor for nervous control of afferent resistance (AUMK), an autoregulatory feedback multiplier effect on afferent arteriolar resistance (RNAUG2), a myogenic autoregulation factor (myogrs), and a basic afferent arteriolar resistance factor (AAR1) which allows for intrarenal alterations. KD21, KD22, and KD23: Calculation of the effect of circulating atrial natriuretic peptide on afferent arteriolar resistance (AAR). The input to this sequence is ANPX which is derived from the atrial natriuretic peptide section diagram. Sensitivity is determined by ANPXAF, and the lower limit of AAR is set by Block 23 to equal AARLL. KD21 and KD22: Calculation of the effect of circulating atrial natriuretic peptide on afferent arteriolar resistance (AAR). The input to this sequence is ANPX which is derived from the atrial natriuretic peptide section diagram. Sensitivity is determined by ANPXAF. KD23: The lower limit of AAR is set by Block 23 to equal AARLL. $\mathrm{AART}=\mathrm{AAR1}-\mathrm{ANPX}\mathrm{ANPXAF}+\mathrm{ANPXAF}\mathrm{AAR}=\begin{cases}\mathrm{AARLL} & \text{if \mathrm{AART}< \mathrm{AARLL}}\\ \mathrm{AART} & \text{otherwise}\end{cases}$ Containment grouping component for "autonomic_effect_on_EAR", "angiotensin_effect_on_EAR", "effect_of_renal_autoregulatory_feedback_on_EAR" and "EAR_calculation". KD14, KD15, and KD16: Calculation from AUMK (the output of Block 13), the effect of autonomic stimulation on efferent arteriolar resistance. The output of Block 16 multiplies efferent arteriolar resistance in Block 6. KD14, KD15, and KD16: Calculation from AUMK (the output of Block 13), the effect of autonomic stimulation on efferent arteriolar resistance. The output of Block 16 multiplies efferent arteriolar resistance in Block 6. KD3, KD4 and KD5: Calculation of a temporary value for the effect of angiotensin on the efferent arteriolar resistance (ANMER). The angiotensin-related factors that affect the efferent arteriolar resistance are an angiotensin multiplier (ANM), and a sensitivity control for the effect of angiotensin on the efferent arterioles (ANMEM). KD3, KD4 and KD5: Calculation of a temporary value for the effect of angiotensin on the efferent arteriolar resistance (ANMER). The angiotensin-related factors that affect the efferent arteriolar resistance are an angiotensin multiplier (ANM), and a sensitivity control for the effect of angiotensin on the efferent arterioles (ANMEM). KD17, KD18, and KD19: Sensitivity control of the renal autoregulatory feedback on efferent arteriolar resistance. The sensitivity is controlled by (EFAFR) in Block 18. KD17, KD18, and KD19: Sensitivity control of the renal autoregulatory feedback on efferent arteriolar resistance. The sensitivity is controlled by (EFAFR) in Block 18. KD6 and KD6A: Calculation of the efferent arteriolar resistance of the kidneys (EAR). The various factors that affect this are: the angiotensin multiplier on efferent arterioles (ANMER), the basic efferent arteriolar resistance when all other factors are normal (EARK), a multiplier factor from Block KD19 that determines feedback from the renal autoregulatory mechanism, a multiplier factor from Block 16 that determines autonomic nervous signal control of efferent arteriolar resistance, and a factor (MYOGRS) for any myogenic autoregulation that might occur in the efferent arterioles. Block KD6A sets the lower limit for the efferent arteriolar resistance (EAR) at a level equal to the factor (EARLL). KD6: Calculation of the efferent arteriolar resistance of the kidneys (EAR). The various factors that affect this are: the angiotensin multiplier on efferent arterioles (ANMER), the basic efferent arteriolar resistance when all other factors are normal (EARK), a multiplier factor from Block KD19 that determines feedback from the renal autoregulatory mechanism, a multiplier factor from Block 16 that determines autonomic nervous signal control of efferent arteriolar resistance, and a factor (MYOGRS) for any myogenic autoregulation that might occur in the efferent arterioles. KD6A: Block KD6A sets the lower limit for the efferent arteriolar resistance (EAR) at a level equal to the factor (EARLL). KD20: Calculation of the total renal resistance (RR) by adding efferent arteriolar resistance (EAR) to afferent resistance (AAR). KD20: Calculation of the total renal resistance (RR) by adding efferent arteriolar resistance (EAR) to afferent resistance (AAR). $\mathrm{RR}=\mathrm{AAR}+\mathrm{EAR}$ KD24A: Renal perfusion pressure (PAR) divided by renal resistance (RR) equals the renal blood flow for normal kidneys (RFN). KD24A: Renal perfusion pressure (PAR) divided by renal resistance (RR) equals the renal blood flow for normal kidneys (RFN). $\mathrm{RFN}=\frac{\mathrm{PAR}}{\mathrm{RR}}$ KD73: Calculation of the actual renal blood flow (RBF) by multiplying the normalized renal blood flow (RFN) for two normal kidneys times the fraction of normal kidney mass present in the body (REK). KD73: Calculation of the actual renal blood flow (RBF) by multiplying the normalized renal blood flow (RFN) for two normal kidneys times the fraction of normal kidney mass present in the body (REK). $\mathrm{RBF}=\mathrm{REK}\mathrm{RFN}$ Containment grouping component for "glomerular_colloid_osmotic_pressure", "glomerular_pressure", "glomerular_filtration_rate". KD68, KD69, KD70, KD71, KD71A, KD72, KD72A, and KD72B: Calculation of the colloid osmotic pressure of the proteins in the plasma of the fluid flowing through the glomerular capillaries (GLPC). This calculation is based on four input factors, fractional hematocrit (HM1) in Block 68, normalized rate of blood flow (RFN) in Block 69, normalized rate of flow through the two kidneys (GFN) in Block 70, and plasma protein concentration in the blood elsewhere in the body (PPC) in Block 72A. The output of Block 72A is damped in Block 72B by the damping factor GPPD; this is to prevent oscillation in the feedback circuit. NB - REMOVED DAMPING FROM KD72-KD72B!!!! KD68, KD69, KD70, KD71, KD71A, KD72, KD72A, and KD72B: Calculation of the colloid osmotic pressure of the proteins in the plasma of the fluid flowing through the glomerular capillaries (GLPC). This calculation is based on four input factors, fractional hematocrit (HM1) in Block 68, normalized rate of blood flow (RFN) in Block 69, normalized rate of flow through the two kidneys (GFN) in Block 70, and plasma protein concentration in the blood elsewhere in the body (PPC) in Block 72A. The output of Block 72A is damped in Block 72B by the damping factor GPPD; this is to prevent oscillation in the feedback circuit. NB - REMOVED DAMPING FROM KD72-KD72B!!!! KD68, KD69, KD70, KD71, KD71A, KD72, KD72A, and KD72B: Calculation of the colloid osmotic pressure of the proteins in the plasma of the fluid flowing through the glomerular capillaries (GLPC). This calculation is based on four input factors, fractional hematocrit (HM1) in Block 68, normalized rate of blood flow (RFN) in Block 69, normalized rate of flow through the two kidneys (GFN) in Block 70, and plasma protein concentration in the blood elsewhere in the body (PPC) in Block 72A. The output of Block 72A is damped in Block 72B by the damping factor GPPD; this is to prevent oscillation in the feedback circuit. NB - REMOVED DAMPING FROM KD72-KD72B!!!! KD68, KD69, KD70, KD71, KD71A, KD72, KD72A, and KD72B: Calculation of the colloid osmotic pressure of the proteins in the plasma of the fluid flowing through the glomerular capillaries (GLPC). This calculation is based on four input factors, fractional hematocrit (HM1) in Block 68, normalized rate of blood flow (RFN) in Block 69, normalized rate of flow through the two kidneys (GFN) in Block 70, and plasma protein concentration in the blood elsewhere in the body (PPC) in Block 72A. The output of Block 72A is damped in Block 72B by the damping factor GPPD; this is to prevent oscillation in the feedback circuit. NB - REMOVED DAMPING FROM KD72-KD72B!!!! KD24: Arterial pressure drop (APD) in the renal arteries and afferent arterioles before the blood gets to the glomerulus equals RFN times efferent arterial resistance (AAR). KD25: Calculation of glomerular pressure (GLP) by subtracting afferent pressure drop (APD) from the input pressure to the kidney (PAR). KD24: Arterial pressure drop (APD) in the renal arteries and afferent arterioles before the blood gets to the glomerulus equals RFN times efferent arterial resistance (AAR). KD25: Calculation of glomerular pressure (GLP) by subtracting afferent pressure drop (APD) from the input pressure to the kidney (PAR). $\mathrm{APD}=\mathrm{AAR}\mathrm{RFN}\mathrm{GLP}=\mathrm{PAR}-\mathrm{APD}$ KD26: Calculation of average filtration pressure through the glomerular capillary walls (PFL) by subtracting intrarenal pressure (PXTP) and colloid osmotic pressure of the glomerular plasma (GLPC) from the average glomerular pressure (GLP). KD27 and KD28: Calculation of the normalized glomerular filtration rate (GFN) if both kidneys are fully functional. This is calculated by multiplying the pressure drop across the glomerular capillary membrane (PFL) times the glomerular filtration coefficient (GFLC). The lower limit for glomerular filtration is set in Block 28 by the value GFNLL. NB - DAMPING REMOVED FROM KD27!!! KD51: Calculation of the actual glomerular filtration rate (GFR) by multiplying the rate that would be true if both kidneys were totally intact (GFN) times the fraction of normal kidney mass actually functioning (REK). KD26: Calculation of average filtration pressure through the glomerular capillary walls (PFL) by subtracting intrarenal pressure (PXTP) and colloid osmotic pressure of the glomerular plasma (GLPC) from the average glomerular pressure (GLP). KD27: Calculation of the normalized glomerular filtration rate (GFN) if both kidneys are fully functional. This is calculated by multiplying the pressure drop across the glomerular capillary membrane (PFL) times the glomerular filtration coefficient (GFLC). NB - DAMPING REMOVED FROM KD27!!! KD28: The lower limit for glomerular filtration is set in Block 28 by the value GFNLL. KD51: Calculation of the actual glomerular filtration rate (GFR) by multiplying the rate that would be true if both kidneys were totally intact (GFN) times the fraction of normal kidney mass actually functioning (REK). $\mathrm{PFL}=\mathrm{GLP}-\mathrm{GLPC}-\mathrm{PXTP}\mathrm{GFN1}=\mathrm{PFL}\mathrm{GFLC}\mathrm{GFN}=\begin{cases}\mathrm{GFNLL} & \text{if \mathrm{GFN1}< \mathrm{GFNLL}}\\ \mathrm{GFN1} & \text{otherwise}\end{cases}\mathrm{GFR}=\mathrm{GFN}\mathrm{REK}$ KD29: Calculation of normalized rate of flow of fluid out of the proximal tubules (PTFL) making the assumption that this is directly proportional to the normalized glomerular filtration rate (GFN). The value (1.0) is considered to be the normal flow of fluid out of the proximal tubules when all functions of the kidneys are normal. KD30, KD31, and KD32: This is a sensitivity controller to determine the normalized rate of flow of tubular fluid at the macula densa level in the kidneys (MDFLW) when the normalized rate of flow out of the proximal tubules (PTFL) changes from the normalized mean value of 1. The multiplier value MDFL1 in Block 31 determines how many times as much the normalized value for macula densa flow (MDFLW) changes with respect to change in proximal tubular outflow (PTFL). KD33: This block sets a lower limit of macula densa flow (MDFLW) equal to zero. KD29: Calculation of normalized rate of flow of fluid out of the proximal tubules (PTFL) making the assumption that this is directly proportional to the normalized glomerular filtration rate (GFN). The value (1.0) is considered to be the normal flow of fluid out of the proximal tubules when all functions of the kidneys are normal. KD30, KD31, and KD32: This is a sensitivity controller to determine the normalized rate of flow of tubular fluid at the macula densa level in the kidneys (MDFLW) when the normalized rate of flow out of the proximal tubules (PTFL) changes from the normalized mean value of 1. The multiplier value MDFL1 in Block 31 determines how many times as much the normalized value for macula densa flow (MDFLW) changes with respect to change in proximal tubular outflow (PTFL). KD33: This block sets a lower limit of macula densa flow (MDFLW) equal to zero. KD79, KD80, and KD81: Calculation of the renal tissue fluid colloid osmotic pressure (RTSPPC) based on the average colloid osmotic pressure of the plasma in the glomerulus (GLPC) times a factor caused by reabsorption of fluid into the plasma flowing through the capillaries surrounding the tubules (RTPPR), and minus a factor resulting from a protein differential between the capillaries and the tissue spaces (RTPPRS). The lower limit of RTSPPC is set to 1.0 by Block 81. KD79 and KD80: Calculation of the renal tissue fluid colloid osmotic pressure (RTSPPC) based on the average colloid osmotic pressure of the plasma in the glomerulus (GLPC) times a factor caused by reabsorption of fluid into the plasma flowing through the capillaries surrounding the tubules (RTPPR), and minus a factor resulting from a protein differential between the capillaries and the tissue spaces (RTPPRS). KD81: The lower limit of RTSPPC is set to 1.0 by Block 81. Containment grouping component for "plasma_urea_concentration", "glomerular_urea_concentration". KD53 and KD54: Calculation of the concentration of urea in the glomerular filtrate and also in the plasma (PLURC). Subtraction in Block 53 of the urinary output of urea (UROD) from rate of formation of urea in the body (URFORM) and the result integrated in Block 54 calculates the total urea in the plasma and other body fluids (PLUR). KD53 and KD54: Calculation of the concentration of urea in the glomerular filtrate and also in the plasma (PLURC). Subtraction in Block 53 of the urinary output of urea (UROD) from rate of formation of urea in the body (URFORM) and the result integrated in Block 54 calculates the total urea in the plasma and other body fluids (PLUR). $\frac{d \mathrm{PLUR}}{d \mathrm{time}}}=\mathrm{URFORM}-\mathrm{UROD}$ KD55: Calculation of the concentration of urea in the glomerular filtrate and also in the plasma (PLURC). KD55: Calculation of the concentration of urea in the glomerular filtrate and also in the plasma (PLURC). $\mathrm{PLURC}=\frac{\mathrm{PLUR}}{\mathrm{VTW}}$ Containment grouping component for "peritubular_capillary_pressure" and "peritubular_capillary_reabsorption_factor". KD74, KD75, KD76, and KD77: Calculation of renal peritubular capillary pressure. Blocks KD74, KD75 and KD76 are a sensitivity control to determine the effect of changes in RFN on the calculation. In Block KD77, the output of Block KD76 is multiplied by a resistance from the glomerulus back to the large veins (RVRS). KD74, KD75, KD76, and KD77: Calculation of renal peritubular capillary pressure. Blocks KD74, KD75 and KD76 are a sensitivity control to determine the effect of changes in RFN on the calculation. In Block KD77, the output of Block KD76 is multiplied by a resistance from the glomerulus back to the large veins (RVRS). KD78: The pressure difference for absorption of fluid into the peritubular capillaries (RABSPR) is equal to the average colloid osmotic pressure in the peritubular capillaries (RABSPR), which is equal to the average colloid osmotic pressure in the glomerulus (GLPC), minus renal tissue fluid colloid osmotic pressure (RTSPPC), minus the renal peritubular capillary pressure (RCPRS), and plus the renal tissue fluid pressure (RTSPRS). KD82: A temporary distal tubular reabsorption factor (RFAB1) is calculated from the peritubular capillary absorptive pressure difference (RABSPR) times the renal peritubular capillary reabsorption coefficient (RABSC). KD83: This is a damping circuit to calculate the reabsorption factor (RFAB). The damping coefficient is RFABDP. The purpose of this is to prevent oscillation in the system. NB - REMOVED DAMPING FROM KD83!! KD84, KD85, KD86, and KD87: Blocks 84, 85, and 86 are a sensitivity control for determining the effect of the reabsorption factor RFAB on distal tubule reabsorption (RFABD). The sensitivity is controlled by the factor in Block 85, RFABDM. Block 87 prevents the value of RFABD from falling below a value of .0001. KD78: The pressure difference for absorption of fluid into the peritubular capillaries (RABSPR) is equal to the average colloid osmotic pressure in the peritubular capillaries (RABSPR), which is equal to the average colloid osmotic pressure in the glomerulus (GLPC), minus renal tissue fluid colloid osmotic pressure (RTSPPC), minus the renal peritubular capillary pressure (RCPRS), and plus the renal tissue fluid pressure (RTSPRS). KD82: A temporary distal tubular reabsorption factor (RFAB1) is calculated from the peritubular capillary absorptive pressure difference (RABSPR) times the renal peritubular capillary reabsorption coefficient (RABSC). KD83: This is a damping circuit to calculate the reabsorption factor (RFAB). The damping coefficient is RFABDP. The purpose of this is to prevent oscillation in the system. NB - REMOVED DAMPING FROM KD83!! KD84, KD85, and KD86: Blocks 84, 85, and 86 are a sensitivity control for determining the effect of the reabsorption factor RFAB on distal tubule reabsorption (RFABD). The sensitivity is controlled by the factor in Block 85, RFABDM. KD87: Block 87 prevents the value of RFABD from falling below a value of .0001. Containment grouping component for "distal_tubular_Na_delivery", "Na_reabsorption_into_distal_tubules", "angiotensin_induced_Na_reabsorption_into_distal_tubules", "distal_tubular_K_delivery", "effect_of_physical_forces_on_distal_K_reabsorption", "effect_of_fluid_flow_on_K_reabsorption", "K_reabsorption_into_distal_tubules", "K_secretion_from_distal_tubules". KD34: Calculation of rate of delivery of sodium into the distal tubular system of two normal kidneys in milliequivalents per minute (DTNAI), which is equal to the normalized delivery of fluid into the distal tubules (MDFLW) times the concentration of sodium in the tubules (CNA), times the factor 0.0061619. KD34: Calculation of rate of delivery of sodium into the distal tubular system of two normal kidneys in milliequivalents per minute (DTNAI), which is equal to the normalized delivery of fluid into the distal tubules (MDFLW) times the concentration of sodium in the tubules (CNA), times the factor 0.0061619. KD113, KD114, and KD115: Calculation of the effect of an antidiuretic hormone multiplier constant (ADHMK) on the absorption of sodium by the distal tubular-collecting duct system (output of Block 115). The sensitivity of this ADH effect is adjusted by the sensitivity factor AHMNAR in Block 114. KD36 and KD37: Calculation of the sodium reabsorbed in the distal tubules and collecting duct (DTNARA). The different factors that affect this are the basic value for the normal state (DTNAR), the basic blood capillary hemodynamics of the system (RFABD), the effect of antidiuretic hormone (from Block 115), and the effect of an aldosterone multiplier effect to cause reabsorption of sodium (AMNA) as determined from the output of Block 23 in the aldosterone section of these diagrams. Block 37 sets the lower limit of DTNARA at zero. DIURET allows one to simulate the effect of a diuretic. KD113, KD114, and KD115: Calculation of the effect of an antidiuretic hormone multiplier constant (ADHMK) on the absorption of sodium by the distal tubular-collecting duct system (output of Block 115). The sensitivity of this ADH effect is adjusted by the sensitivity factor AHMNAR in Block 114. KD36 and KD37: Calculation of the sodium reabsorbed in the distal tubules and collecting duct (DTNARA). The different factors that affect this are the basic value for the normal state (DTNAR), the basic blood capillary hemodynamics of the system (RFABD), the effect of antidiuretic hormone (from Block 115), and the effect of an aldosterone multiplier effect to cause reabsorption of sodium (AMNA) as determined from the output of Block 23 in the aldosterone section of these diagrams. Block 37 sets the lower limit of DTNARA at zero. DIURET allows one to simulate the effect of a diuretic. KD36 and KD37: Calculation of the sodium reabsorbed in the distal tubules and collecting duct (DTNARA). The different factors that affect this are the basic value for the normal state (DTNAR), the basic blood capillary hemodynamics of the system (RFABD), the effect of antidiuretic hormone (from Block 115), and the effect of an aldosterone multiplier effect to cause reabsorption of sodium (AMNA) as determined from the output of Block 23 in the aldosterone section of these diagrams. Block 37 sets the lower limit of DTNARA at zero. DIURET allows one to simulate the effect of a diuretic. KD108, KD109, KD110, KD111, and KD112: Calculation of the fraction of the distal tubular reabsorption of sodium that is absorbed each minute that is dependent on the availability of angiotensin (DTNANG). The input factor to this system of blocks, ANM, is the angiotensin multiplier. Blocks 108, 109, and 110 adjust the sensitivity of the effect in accordance with the sensitivity factor ANMNAM. Block 111 converts the output of Block 110 into actual milliequivalents of sodium per minute, and Block 112 places a lower limit on absorption of sodium in response to angiotensin to a level of zero. KD108, KD109, KD110 and KD111: Calculation of the fraction of the distal tubular reabsorption of sodium that is absorbed each minute that is dependent on the availability of angiotensin (DTNANG). The input factor to this system of blocks, ANM, is the angiotensin multiplier. Blocks 108, 109, and 110 adjust the sensitivity of the effect in accordance with the sensitivity factor ANMNAM. Block 111 converts the output of Block 110 into actual milliequivalents of sodium per minute. KD112: Block 112 places a lower limit on absorption of sodium in response to angiotensin to a level of zero. KD101 and KD102: Calculation of the rate of entry of potassium into the distal tubular system (DTKI) based on the rate of sodium entry into the system (DTNAI), divided by the concentration of sodium in the extracellular fluid (CNA), and multiplied by the concentration of potassium in the extracellular fluid (CKE). KD101 and KD102: Calculation of the rate of entry of potassium into the distal tubular system (DTKI) based on the rate of sodium entry into the system (DTNAI), divided by the concentration of sodium in the extracellular fluid (CNA), and multiplied by the concentration of potassium in the extracellular fluid (CKE). $\mathrm{DTKI}=\frac{\mathrm{DTNAI}\mathrm{CKE}}{\mathrm{CNA}}$ KD99 and KD100: Calculation of the effect of renal hemodynamics (RFABD) in affecting the rate of reabsorption of potassium by the distal tubule-collecting duct system (RFABK). The intensity of this effect is controlled by factor RFABKM in Block 100. KD99 and KD100: Calculation of the effect of renal hemodynamics (RFABD) in affecting the rate of reabsorption of potassium by the distal tubule-collecting duct system (RFABK). The intensity of this effect is controlled by factor RFABKM in Block 100. KD88, KD89, KD90, and KD90A: Calculation of a multiplier factor for the effect of rate of flow of fluid into the distal tubular system (MDFLW) on the rate of reabsorption of potassium from the distal tubules and collecting ducts (MDFLK). The sensitivity of this control is MDFLKM in Block 89. The lower limit of the output MDFLK is set to .1 by Block 90A. KD88, KD89 and KD90: Calculation of a multiplier factor for the effect of rate of flow of fluid into the distal tubular system (MDFLW) on the rate of reabsorption of potassium from the distal tubules and collecting ducts (MDFLK). The sensitivity of this control is MDFLKM in Block 89. KD90A: The lower limit of the output MDFLK is set to .1 by Block 90A. KD104, KD105, KD106, and KD107: The rate of reabsorption of potassium in the distal tubule-collecting duct system DTKA is proportional to the urinary excretion rate of potassium (KODN) times a proportionality factor, .0004519, and divided by the rate of output of urine from the kidneys (VUDN). Blocks 105, 106, and 107 are a time delay circuit to allow for the time required for this effect to develop. The time delay constant is determined by factor I6 in Block 106. KD104, KD105, KD106, and KD107: The rate of reabsorption of potassium in the distal tubule-collecting duct system DTKA is proportional to the urinary excretion rate of potassium (KODN) times a proportionality factor, .0004519, and divided by the rate of output of urine from the kidneys (VUDN). Blocks 105, 106, and 107 are a time delay circuit to allow for the time required for this effect to develop. The time delay constant is determined by factor I6 in Block 106. KD91, KD92, and KD93: Calculation of a temporary rate of potassium secretion into the distal tubular-collecting tubular system (DTKSC1) based on the concentration of potassium in the plasma (CKE), which is first normalized to the value 1.0 in Block 91, then raised to a power (CKEEX) in Block 92. The result is multiplied by the delivery of potassium into the tubular system at the macula densa level of the distal tubule (MDFLK), and by a multiplier effect depicting the effect of aldosterone on the secretion of potassium by the tubular epithelium into the tubule (AMK). KD94, KD95, KD96, KD97, and KD98: Calculation of the actual rate of secretion of potassium into the distal tubule-collecting duct system (DTKSC) by multiplying the temporary rate of secretion from Block 93 (DTKSC1) times a multiplier factor based on angiotensin concentration in the body fluids (ANMKE). ANMKE is calculated from a generalized body angiotensin multiplier factor (ANM) times a controller for the sensitivity of this effect (ANMKEM). ANMKE is limited to a lowest value by ANMKEL in Block 97. KD94, KD95 and KD96: Calculation of the actual rate of secretion of potassium into the distal tubule-collecting duct system (DTKSC) by multiplying the temporary rate of secretion from Block 93 (DTKSC1) times a multiplier factor based on angiotensin concentration in the body fluids (ANMKE). ANMKE is calculated from a generalized body angiotensin multiplier factor (ANM) times a controller for the sensitivity of this effect (ANMKEM). KD97: ANMKE is limited to a lowest value by ANMKEL in Block 97. KD91, KD92, and KD93: Calculation of a temporary rate of potassium secretion into the distal tubular-collecting tubular system (DTKSC1) based on the concentration of potassium in the plasma (CKE), which is first normalized to the value 1.0 in Block 91, then raised to a power (CKEEX) in Block 92. The result is multiplied by the delivery of potassium into the tubular system at the macula densa level of the distal tubule (MDFLK), and by a multiplier effect depicting the effect of aldosterone on the secretion of potassium by the tubular epithelium into the tubule (AMK). Containment grouping component for "normal_Na_excretion", "normal_K_excretion", "normal_urea_excretion", "normal_osmolar_and_water_excretion", "normal_urine_volume", "actual_Na_exretion_rate", "actual_K_excretion_rate", "actual_urea_excretion_rate", "actual_urine_volume". KD35: Calculation of the normalized rate of delivery of sodium into the urine (NODN) if both kidneys are intact and normal. This is calculated by subtracting from the rate of entry of sodium into the distal tubular system (DTNAI) the distal tubular and collecting duct reabsorption of sodium caused by the presence of angiotensin in the blood (DTNANG) and that caused by multiple other factors (DTNARA) from Blocks 36 and 37. KD38: This sets a lower limit for the normalized output of sodium (NODN) to zero. KD35: Calculation of the normalized rate of delivery of sodium into the urine (NODN) if both kidneys are intact and normal. This is calculated by subtracting from the rate of entry of sodium into the distal tubular system (DTNAI) the distal tubular and collecting duct reabsorption of sodium caused by the presence of angiotensin in the blood (DTNANG) and that caused by multiple other factors (DTNARA) from Blocks 36 and 37. KD38: This sets a lower limit for the normalized output of sodium (NODN) to zero. KD103 and KD103A: The normalized rate of excretion of potassium into the urine by two normal kidneys (KODN) is equal to the rate of entry of potassium into the distal tubular-collecting duct system (DTKI), minus any excess absorption caused by abnormal renal hemodynamics (RFABK), plus the rate of secretion of potassium by the tubular epithelium into the distal tubules and collecting tubules (DTKSC), and minus the rate of absorption of potassium by all portions of the distal tubule-collecting duct system DTKA. Block 103A sets the lower limit of the excretion of potassium in the urine (KODN) at zero. KD103: The normalized rate of excretion of potassium into the urine by two normal kidneys (KODN) is equal to the rate of entry of potassium into the distal tubular-collecting duct system (DTKI), minus any excess absorption caused by abnormal renal hemodynamics (RFABK), plus the rate of secretion of potassium by the tubular epithelium into the distal tubules and collecting tubules (DTKSC), and minus the rate of absorption of potassium by all portions of the distal tubule-collecting duct system DTKA. KD103A: Block 103A sets the lower limit of the excretion of potassium in the urine (KODN) at zero. KD52: Calculation of the rate of excretion of urea if both kidneys were functionally intact (DTURI) by multiplying the concentration of urea in the glomerular filtrate (PLURC) times the square of glomerular filtration for the two normal kidneys (GFN) times the numerical factor 3.84. KD52: Calculation of the rate of excretion of urea if both kidneys were functionally intact (DTURI) by multiplying the concentration of urea in the glomerular filtrate (PLURC) times the square of glomerular filtration for the two normal kidneys (GFN) times the numerical factor 3.84. KD40, KD41, and KD42: Calculation of the normalized output of osmotic substances by the kidneys if both kidneys are functioning totally and normally (OSMOPN) by adding together in Block 40 the milliequivalents of sodium output (NODN) and potassium output (KODN), then multiplying in Block 41 by a factor of 2 to include the anions that go with the sodium and potassium cations, and addition in Block 42 of osmotic excretion in the form of urea (DUTRI). KD40, KD41, and KD42: Calculation of the normalized output of osmotic substances by the kidneys if both kidneys are functioning totally and normally (OSMOPN) by adding together in Block 40 the milliequivalents of sodium output (NODN) and potassium output (KODN), then multiplying in Block 41 by a factor of 2 to include the anions that go with the sodium and potassium cations, and addition in Block 42 of osmotic excretion in the form of urea (DUTRI). KD43, KD44, KD45, KD46, KD47, and KD48: Calculation of the normalized output of urine volume if both kidneys are totally intact (VUDN) as the output of Block 48. Blocks 43, 45, and 47 calculate the portion of VUDN that is caused by excess of osmotic substances (OSMOP1) over and above the normal amount (OSMOPN). Blocks 44 and 46 calculate the portion of VUDN that is caused by that portion of OSMOPN that is below the normal value of .6. The sensitivity of this portion of urine output varies markedly with the antidiuretic hormone effect on the kidney (ADHMK). Block 48 summates the total VUDN caused by the osmotic substances above the normal level of .6 plus those caused by the osmotic substances below the normal level of .6. KD43, KD44, KD45, KD46, KD47, and KD48: Calculation of the normalized output of urine volume if both kidneys are totally intact (VUDN) as the output of Block 48. Blocks 43, 45, and 47 calculate the portion of VUDN that is caused by excess of osmotic substances (OSMOP1) over and above the normal amount (OSMOPN). Blocks 44 and 46 calculate the portion of VUDN that is caused by that portion of OSMOPN that is below the normal value of .6. The sensitivity of this portion of urine output varies markedly with the antidiuretic hormone effect on the kidney (ADHMK). Block 48 summates the total VUDN caused by the osmotic substances above the normal level of .6 plus those caused by the osmotic substances below the normal level of .6. KD43, KD44, KD45, KD46, KD47, and KD48: Calculation of the normalized output of urine volume if both kidneys are totally intact (VUDN) as the output of Block 48. Blocks 43, 45, and 47 calculate the portion of VUDN that is caused by excess of osmotic substances (OSMOP1) over and above the normal amount (OSMOPN). Blocks 44 and 46 calculate the portion of VUDN that is caused by that portion of OSMOPN that is below the normal value of .6. The sensitivity of this portion of urine output varies markedly with the antidiuretic hormone effect on the kidney (ADHMK). Block 48 summates the total VUDN caused by the osmotic substances above the normal level of .6 plus those caused by the osmotic substances below the normal level of .6. KD43, KD44, KD45, KD46, KD47, and KD48: Calculation of the normalized output of urine volume if both kidneys are totally intact (VUDN) as the output of Block 48. Blocks 43, 45, and 47 calculate the portion of VUDN that is caused by excess of osmotic substances (OSMOP1) over and above the normal amount (OSMOPN). Blocks 44 and 46 calculate the portion of VUDN that is caused by that portion of OSMOPN that is below the normal value of .6. The sensitivity of this portion of urine output varies markedly with the antidiuretic hormone effect on the kidney (ADHMK). Block 48 summates the total VUDN caused by the osmotic substances above the normal level of .6 plus those caused by the osmotic substances below the normal level of .6. KD39: Calculation of the actual rate of sodium output from the kidneys (NOD) by multiplying the normalized rate (NODN) times the percentage of normal kidney mass that is present in the body (REK). KD39: Calculation of the actual rate of sodium output from the kidneys (NOD) by multiplying the normalized rate (NODN) times the percentage of normal kidney mass that is present in the body (REK). $\mathrm{NOD}=\mathrm{NODN}\mathrm{REK}$ KD116: Calculation of the actual rate of potassium output from the kidneys (KOD) by multiplying the normalized rate (KODN) times the percentage of normal kidney mass that is present in the body (REK). KD116: Calculation of the actual rate of potassium output from the kidneys (KOD) by multiplying the normalized rate (KODN) times the percentage of normal kidney mass that is present in the body (REK). $\mathrm{KOD}=\mathrm{KODN}\mathrm{REK}$ KD56: Calculation of rate of excretion of urea per minute in terms of osmoles (UROD), which is equal to the rate of excretion if the kidneys were normal (DTURI) times the actual fraction of normal kidney mass in the body (REK). KD56: Calculation of rate of excretion of urea per minute in terms of osmoles (UROD), which is equal to the rate of excretion if the kidneys were normal (DTURI) times the actual fraction of normal kidney mass in the body (REK). $\mathrm{UROD}=\mathrm{DTURI}\mathrm{REK}$ KD49: Actual rate of urinary output (VUD) calculated from the rate of output if both kidneys were totally intact (VUDN) by multiplying VUDN by the fraction of normal kidney mass that is functional in the body (REK). KD50: A stability test to test whether or not VUD is varying up and down too much and if so making appropriate mathematical corrections. This is simply a mathematical maneuver for allowing more rapid solution of the equations. NB - This stability test has not been coded!!! KD49: Actual rate of urinary output (VUD) calculated from the rate of output if both kidneys were totally intact (VUDN) by multiplying VUDN by the fraction of normal kidney mass that is functional in the body (REK). KD50: A stability test to test whether or not VUD is varying up and down too much and if so making appropriate mathematical corrections. This is simply a mathematical maneuver for allowing more rapid solution of the equations. NB - This stability test has not been coded!!! $\mathrm{VUD}=\mathrm{VUDN}\mathrm{REK}$