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Cardiovascular System: Blood Vessels and Blood Pressure Regulation

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  • 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 is measured as systemic arterial BP in large arteries near the heart.

  • What is peripheral resistance?

    Peripheral resistance is the opposition to blood flow caused by friction between blood and vessel walls, mainly in systemic circulation.

  • Name the three main sources of peripheral resistance.
    • Blood viscosity
    • Total blood vessel length
    • Blood vessel diameter
  • How does blood viscosity affect resistance?

    Increased blood viscosity (thickness) increases resistance because thicker blood flows less easily.

  • How does blood vessel length affect resistance?

    The longer the blood vessel, the greater the resistance encountered by blood flow.

  • Which factor has the greatest influence on peripheral resistance?

    Blood vessel diameter has the greatest influence on resistance, with resistance varying inversely with the fourth power of the vessel radius.

  • What happens to resistance if the vessel radius doubles?

    If the radius doubles, resistance drops to 1/16 of its original value.

  • What is laminar flow and turbulent flow?

    Laminar flow is smooth, layered blood flow; turbulent flow is irregular flow that increases resistance and occurs with abrupt vessel diameter changes or plaques.

  • How is blood flow related to blood pressure gradient and resistance?

    Blood flow is directly proportional to the blood pressure gradient and inversely proportional to peripheral resistance.

  • 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?
    • Elasticity of arteries near the heart
    • Volume of blood forced into them at any time
  • Define systolic and diastolic pressure.
    • Systolic pressure: pressure during ventricular contraction, averages 120 mm Hg
    • Diastolic pressure: lowest aortic pressure during heart relaxation
  • What is pulse pressure?

    Pulse pressure is the difference between systolic and diastolic pressure and causes the throbbing sensation of the pulse.

  • How is mean arterial pressure (MAP) calculated?

    MAP = diastolic pressure + 1/3 pulse pressure

  • What are the main factors regulating blood pressure?
    • Cardiac output (CO)
    • Peripheral resistance (PR)
    • Blood volume
  • How does cardiac output affect mean arterial pressure?

    MAP is directly proportional to cardiac output; increases in stroke volume or heart rate raise MAP.

  • What neural mechanisms regulate blood pressure short-term?
    • Baroreceptor reflexes
    • Chemoreceptor reflexes
    • Higher brain center input
  • What is the role of baroreceptors in blood pressure regulation?

    Baroreceptors detect changes in blood pressure and send signals to the cardiovascular center to adjust heart rate, contractility, and vessel diameter to maintain homeostasis.

  • Name three factors aiding venous return to the heart.
    • Muscular pump (skeletal muscle contractions)
    • Respiratory pump (pressure changes during breathing)
    • Sympathetic venoconstriction
  • How do adrenal medulla hormones affect blood pressure?

    Epinephrine and norepinephrine increase cardiac output and cause vasoconstriction, raising blood pressure.

  • What is the renin-angiotensin-aldosterone mechanism?

    It is an indirect renal mechanism where renin release leads to angiotensin II formation, causing vasoconstriction, aldosterone secretion, ADH release, thirst, and increased blood volume and pressure.

  • What is 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 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.

  • What is circulatory shock?

    A condition where blood vessels are inadequately filled, causing insufficient blood flow to meet tissue needs; types include hypovolemic, vascular, and cardiogenic shock.