Exam 4

• Oxygen-hemoglobin saturation curve


  Graphical representation of the relationship between oxygen partial pressure and hemoglobin saturation

  
• Left shift


  • Occurs when there is an increase in oxygen binding affinity, and less oxygen is released
• Left shift


  • Seen in fetal hemoglobin
• Right shift


  • Occurs when there is a decrease in oxygen binding affinity, and more oxygen is released
• Factors that can shift oxygen to the right

  • Increased temperature
  • Decreased pH
  • Increased PCO2
• Tubuloglomerular feedback


  The main form of GFR control (local control)
• Tubuloglomerular feedback


  Includes the JG apparatus which is a negative feedback loop to maintain GFR by macula densa cells releasing paracrine signals to affect afferent arterioles diameter

  
• Tubuloglomerular feedback


  • This feedback is not 100%
• Myogenic response


  Occurs in the afferent arteriole
• Systemic/reflex control


  Its main function is to keep water and maintain blood pressure
• Systemic/reflex control mechanisms


  • Neural: sympathetic, norepinephrine, alpha receptors (constrict afferent arterioles)
  • Hormonal: ANG II (vasoconstrictor) and ANP (dilates afferent, relax mesangial cells)

  
• Reabsorption


  The process of moving substances from filtrate in lumen in tubule back to blood flowing in peritubular capillaries around the nephron
• Secretion


  The selective removal of molecules from the blood and adding it to filtrate in the tubule lumen
• Excretion


  The movement of substance out of the body through urination
• Filtration


  The process by which fluid and solute are forced from glomerular capillaries into bowman's capsule due to pressure gradient across filtration membrane
• Tmax


  The maximum rate where substances can be reabsorbed by tubules. Is a point where all carriers at the time are saturated
• Clearance


  The amount of volume of plasma cleared at a certain point in time
• GFR


  The amount of fluid filtered from glomerular capillaries to the bowman's capsule per unit time. Measures kidneys ability to filter out waste from blood

  
• Aldosterone


  The hormone responsible for sodium reabsorption and is produced by the adrenal cortex
• Renal calculation


  1. Clearance = Ex / plasma [x]

  2. GFR = Clearance

  3. Excretion (Ex) = urine flow x urine[x]

  4. Excretion (Ex) = Filtration (Fx) - Reabsorption (Rx) + Secretion

  5. Tmax = GFR x RT (renal threshold)

  6. R = Filtration (Fx) - Excretion (Ex)

  7. Filtration = Ex x plasma (glucose)

  
• Hormones responding to blood pressure change

  • Vasopressin (ADH)
  • ANG II
  • ANP
  • Aldosterone
  • Renin

  
• RAS pathway


  1. Renin, ANG II, Aldosterone System

  2. Responds to low BP to increase it

  
• ADH


  Causes vasoconstriction to promote water retention in kidneys, this increases blood pressure and increases blood volume

  
• ADH


  Released by pituitary gland
• ANG II


  Causes vasoconstriction which ends up increasing blood volume and blood pressure

  
• ANG II


  Is made of renin and angiotensin I
• Aldosterone


  The hormone released by the adrenal cortex and it targets P cells
• Aldosterone


  Reabsorbs Na+ and secretes K+ (gets Na+/K+ pump to work), causing an increased blood volume and increased blood pressure

  
• Aldosterone


  Regulates blood pressure by regulating Na+ reabsorption

  
• ANP


  Inhibits renin and aldosterone that are found in the RAS Pathway
• ANP


  Promotes secretion of Na+ and water (increasing urine flow)
• ANP


  Decreases blood volume and blood pressure (vasodilation)
• ANP


  Comes from myocardium in the heart
• Severe dehydration leads to increased osmolarity and increased blood pressure
• Increased osmolarity triggers vasopressin release leading to increased water reabsorption and a decrease in osmolarity (in the hypothalamic mechanism)
• Because of the low blood pressure signal the RAS pathway is activated to increase BP but aldosterone is inhibited by high osmolarity. This leads to less aldosterone and less sodium reabsorption, causing a lowered osmolarity

  
• Renal mechanisms are used to lower GFR and conserve volume
• Cardiac mechanisms come into play when carotid and baroreceptors respond to the low BP signal increasing cardiac output and thus blood pressure

  
• Respiratory acidosis


  HCO3- is absorbed and H+ is secreted, causes a right shift
• Causes of respiratory acidosis

  • Lung diseases
  • Barbiturates and alcohol (drugs)
  • Lung diseases causing airway resistance (asthma, COPD)