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Cardiovascular System: Blood Vessels and Blood Pressure Regulation

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Terms in this set (29)

  • What is blood flow?
    Blood flow is the volume of blood flowing through a vessel, organ, or entire circulation in a given period, measured in milliliters per minute. It equals cardiac output for the entire vascular system.
  • Define blood pressure (BP).
    Blood pressure is the force per unit area exerted on the wall of a blood vessel by blood, expressed in mm Hg. It drives blood from higher- to lower-pressure areas.
  • What is peripheral resistance?
    Peripheral resistance is the opposition to blood flow caused by friction between blood and vessel walls, mainly influenced by blood viscosity, vessel length, and vessel diameter.
  • How does blood viscosity affect resistance?
    Increased blood viscosity (thickness) increases resistance because thicker blood flows less easily, raising friction within vessels.
  • Which factor has the greatest influence on peripheral resistance?
    Blood vessel diameter has the greatest influence on resistance; resistance varies inversely with the fourth power of the vessel radius.
  • Explain laminar flow in blood vessels.
    In laminar flow, fluid near vessel walls moves slower than in the center, reducing resistance; disruption causes turbulent flow, increasing resistance.
  • Relationship between blood flow (F), pressure gradient (ΔP), and resistance (R).
    Blood flow is directly proportional to pressure gradient (ΔP) and inversely proportional to resistance (R): if ΔP increases, flow increases; if R increases, flow decreases.
  • Where is systemic blood pressure highest and where does it drop steeply?
    Systemic blood pressure is highest in the aorta and drops steeply in the arterioles.
  • What determines arterial blood pressure?
    Arterial blood pressure is determined by the elasticity of arteries near the heart and the volume of blood forced into them during each heartbeat.
  • Define systolic and diastolic pressure.
    Systolic pressure is the pressure during ventricular contraction (~120 mm Hg); diastolic pressure is the lowest pressure during heart relaxation (~80 mm Hg).
  • What is pulse pressure and pulse?
    Pulse pressure is the difference between systolic and diastolic pressure; pulse is the throbbing sensation felt due to this pressure difference.
  • How is mean arterial pressure (MAP) calculated?
    MAP = diastolic pressure + 1/3 pulse pressure; it represents the average pressure propelling blood to tissues.
  • How is blood pressure measured clinically?
    Using a sphygmomanometer, cuff pressure is increased above systolic pressure then slowly released; Korotkoff sounds indicate systolic and diastolic pressures.
  • Why is capillary blood pressure low?
    Low capillary pressure (35 to ~17 mm Hg) prevents rupture of fragile capillaries and allows filtrate to move into interstitial spaces.
  • What adaptations aid venous return despite low venous pressure?
    Muscular pump, respiratory pump, and sympathetic venoconstriction help return blood to the heart by squeezing veins and preventing backflow.
  • What are the three main factors regulating blood pressure?
    Blood pressure is regulated by cardiac output (CO), peripheral resistance (PR), and blood volume.
  • How does vessel diameter affect blood pressure regulation?
    Vessel diameter changes alter peripheral resistance, which significantly influences blood pressure by increasing or decreasing resistance.
  • Describe the baroreceptor reflex in blood pressure regulation.
    Baroreceptors in carotid sinuses and aortic arch detect pressure changes and adjust heart rate and vessel diameter via medullary centers to maintain MAP.
  • What happens when blood pressure is high according to baroreceptor reflex?
    Baroreceptors increase input to vasomotor center, inhibiting vasoconstriction and cardioacceleratory centers, stimulating cardioinhibitory center, causing vasodilation and decreased heart rate.
  • How do chemoreceptors influence blood pressure?
    Chemoreceptors detect low pH, low O2, or high CO2 and increase blood pressure by stimulating cardioacceleratory and vasomotor centers to raise CO and vasoconstriction.
  • Name hormones involved in short-term blood pressure regulation.
    Epinephrine and norepinephrine increase CO and vasoconstriction; angiotensin II causes vasoconstriction; ADH causes vasoconstriction; atrial natriuretic peptide lowers blood pressure.
  • How do kidneys regulate blood pressure long-term?
    Kidneys regulate blood pressure by controlling blood volume through direct elimination or retention of water and via the renin-angiotensin-aldosterone system.
  • What triggers the renin-angiotensin-aldosterone mechanism?
    Decreased arterial blood pressure causes kidneys to release renin, leading to angiotensin II production, which raises blood pressure by vasoconstriction and stimulating aldosterone and ADH release.
  • What are the effects of angiotensin II on blood pressure?
    Angiotensin II causes vasoconstriction, stimulates aldosterone secretion, triggers ADH release, and activates thirst to increase blood volume and pressure.
  • Define hypertension and its risks.
    Hypertension is sustained arterial pressure ≥140/90 mm Hg, increasing risk of heart failure, vascular disease, renal failure, and stroke.
  • What is primary hypertension?
    Primary hypertension has no identifiable cause and is influenced by heredity, diet, obesity, age, diabetes, stress, and smoking; it can be controlled but not cured.
  • What causes secondary hypertension?
    Secondary hypertension results from identifiable disorders like kidney disease, obstructed renal arteries, or endocrine disorders such as hyperthyroidism.
  • What is hypotension and when is it a concern?
    Hypotension is low blood pressure below 90/60 mm Hg; usually not a concern unless it causes inadequate tissue perfusion.
  • Describe circulatory shock and its types.
    Circulatory shock is inadequate blood flow to tissues; types include hypovolemic (blood loss), vascular (vasodilation), and cardiogenic (heart failure).