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Anatomy & Physiology: Blood Flow, Blood Pressure, and Renal System

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  • What causes constriction and dilation in blood vessels?
    Constriction is caused by contraction of vascular smooth muscle, narrowing vessel diameter. Dilation is caused by relaxation, increasing vessel diameter.
  • Physical characteristics of arteries
    Thick, elastic walls to sustain high pressure; carry blood away from the heart.
  • Physical characteristics of arterioles
    Smaller branches of arteries with muscular walls; major site of resistance controlling blood flow.
  • Physical characteristics of capillaries
    Microscopic vessels with thin walls for exchange of gases, nutrients, and wastes between blood and tissues.
  • Physical characteristics of venules
    Small vessels that collect blood from capillaries and deliver it to veins.
  • Physical characteristics of veins
    Thin-walled, less muscular vessels with valves; return blood to the heart under low pressure.
  • How do metarterioles differ from arterioles and their function?
    Metarterioles are short vessels linking arterioles to capillaries; they regulate capillary blood flow via precapillary sphincters.
  • What property of artery walls helps sustain driving pressure from the heart?
    The elasticity of artery walls allows them to stretch and recoil, maintaining pressure during the cardiac cycle.
  • Define systolic and diastolic pressure
    Systolic pressure is the peak arterial pressure during heart contraction; diastolic pressure is the minimum pressure during relaxation.
  • What is pulse pressure and how is it calculated?
    Pulse pressure = systolic pressure − diastolic pressure; it reflects the force generated by each heartbeat.
  • Explain mean arterial pressure (MAP) and its formula
    MAP is the average arterial pressure during one cardiac cycle; calculated as MAP = diastolic pressure + 1/3 pulse pressure.
  • Relationship between MAP, cardiac output, and resistance
    MAP = cardiac output × total peripheral resistance; increases in either raise MAP.
  • Effect on MAP if blood flow into arteries increases but outflow is unchanged
    MAP will increase due to accumulation of blood volume in arteries.
  • Effect on MAP if peripheral resistance increases
    MAP will increase because resistance opposes blood flow, raising pressure.
  • Effect on blood pressure if circulating blood volume decreases
    Blood pressure decreases due to reduced blood volume.
  • Which two body systems regulate blood pressure homeostasis?
    The nervous system (via baroreceptor reflex) and the endocrine system (via hormones like RAAS).
  • Two cardiovascular compensations for decreased blood volume
    Increase heart rate and vasoconstriction to maintain blood pressure.
  • Baroreceptor reflex response to increased blood pressure
    Increased baroreceptor firing leads to decreased sympathetic and increased parasympathetic activity, lowering heart rate and dilating vessels.
  • Effect of decreased blood pressure on autonomic activity
    Sympathetic activity increases, parasympathetic activity decreases to raise blood pressure.
  • Effects of increased sympathetic activity on heart and vessels
    Increases heart rate, force of contraction, and causes arteriolar vasoconstriction.
  • Effects of increased parasympathetic activity on heart and vessels
    Decreases heart rate and force of contraction; minimal effect on arteriolar diameter.
  • What is orthostatic hypotension and why does blood pressure initially fall?
    A drop in blood pressure upon standing due to blood pooling in lower extremities and delayed autonomic response.
  • Relationship between total cross-sectional area and velocity of blood flow
    Velocity decreases as total cross-sectional area increases, e.g., slow flow in capillaries for exchange.
  • Types of exchange at capillaries between plasma and interstitial fluid
    Diffusion, filtration, absorption, and bulk flow.
  • Difference between filtration and absorption in capillaries
    Filtration moves fluid out of capillaries; absorption moves fluid into capillaries.
  • Direction of hydrostatic pressure effect on water in capillaries
    Hydrostatic pressure pushes water out of capillaries; it decreases along the capillary length due to energy loss.
  • What creates the osmotic pressure gradient between plasma and interstitial fluid?
    Plasma proteins create colloid osmotic pressure (π), pulling water into capillaries.
  • Direction of bulk flow into lymph capillaries
    Bulk flow moves fluid, proteins, and bacteria into lymph capillaries.
  • List six functions of the kidneys
    Regulate blood volume, blood pressure, osmolarity, ion balance, acid-base balance, and excrete wastes.
  • Difference between cortical and juxtamedullary nephrons
    Cortical nephrons have short loops of Henle; juxtamedullary nephrons have long loops extending deep into the medulla.
  • Path of filtered fluid through nephron
    Bowman’s capsule → proximal tubule → loop of Henle → distal tubule → collecting duct → renal pelvis.
  • What is the renal corpuscle and its function?
    The renal corpuscle consists of glomerulus and Bowman’s capsule; it filters blood plasma.
  • Describe the juxtaglomerular apparatus
    A structure near the glomerulus that regulates blood pressure and filtration rate via renin secretion.
  • When is fluid considered urine?
    When it enters the renal pelvis.
  • Three kidney processes
    Filtration, reabsorption, and secretion.
  • Osmolarity of fluid entering Bowman’s capsule
    Nearly equal to plasma osmolarity (~300 mOsm).
  • Equation relating excretion to kidney processes
    Excretion = Filtration − Reabsorption + Secretion.
  • Filtration barrier components in Bowman’s capsule
    Podocytes with foot processes form filtration slits allowing selective filtration.
  • Define glomerular filtration rate (GFR)
    The volume of filtrate formed per minute by both kidneys; average ~125 mL/min.
  • Effect of afferent arteriole resistance on GFR
    Increased resistance decreases GFR; decreased resistance increases GFR.
  • Effect of efferent arteriole resistance on GFR
    Increased resistance increases GFR; decreased resistance decreases GFR.
  • Difference between myogenic response and tubuloglomerular feedback
    Myogenic response adjusts arteriole diameter to pressure changes; tubuloglomerular feedback uses macula densa signals to regulate GFR.
  • Outline the renin-angiotensin-aldosterone system (RAAS)
    Renin release → angiotensin II formation → vasoconstriction and aldosterone release → increased blood pressure and sodium retention.
  • Three characteristics of mediated transport
    Specificity, saturation, and competition.
  • Define renal threshold
    Plasma concentration at which a substance first appears in urine.
  • Does filtration exhibit saturation?
    No, filtration does not saturate; it depends on plasma concentration.
  • Normal plasma glucose relative to renal threshold and its fate
    Normal plasma glucose is below renal threshold; all filtered glucose is reabsorbed.
  • Forces moving fluid from kidney tubule to peritubular capillaries
    Colloid osmotic pressure and low hydrostatic pressure in peritubular capillaries.
  • Direction of molecules in renal secretion
    From peritubular capillaries into the nephron tubule.
  • Define clearance
    Volume of plasma cleared of a substance per unit time.
  • How to determine GFR using inulin
    GFR = (urine inulin concentration × urine flow rate) / plasma inulin concentration.