Circulation

Functions

  • distribute needs

    • water

    • heat

    • oxygen

    • glucose

  • remove unwanted things

    • carbon dioxide

    • nitrogenous wastes

    • heat

  • maintain homeostasis

    • temperature

    • pH

Types of Circulation

Diffusion

  • small inverts

    • protists, sponges, cnidarians, planarians

  • what characteristics is required for this to work?

    • High SA: Vol ratio

  • body movement helps circulate fluid

Cardiovascular System

  • muscular, pumping heart moves fluid in a specific direction determined by unidirectional vessels

    • open

      • heart pumps hemolymph into body cavity where it bathes cells, tissues, and organs

      • molluscs (except cephalopods) and arthropods

    • closed

      • blood circulates in tubular vessels

        • arteries, arterioles, capillaries, venules, veins

        • annelids, cephalopods, and vertebrates

Vertebrate Circulatory Systems

  • bony fishes

    • single circuit

    • low pressure

  • amphibians

    • double circuit

    • higher pressure/flow

    • single ventricle

  • most reptiles

    • double circuit 

    • partially divided ventricle

  • crocodilians, birds, and mammals

    • double circuit (pulmonary/systematic)

    • completely divided ventricle

    • high blood pressure

Cardiac Definitions

  • preload

    • blood volume, blood available for pumping

  • afterload

    • resistance, against which the heart must pump

  • contractility:

    • performance of the heart muscle

  • heart rate

  • hemodynamics

    • factors affecting blood flow

  • blood flow (mL/min)

    • volume of blood flowing through any tissue in a given period of time

  • total blood flow

    • cardiac output (CO)

      • volume of blood circulating through the systematic (or pulmonary) vessels each minute

      • cardiac output = heart rate (HR) * stroke volume (SV)

  • distribution of CO depends on:

    • pressure differences

      • blood flows from high to low pressure 

      • greater pressure difference = greater blood flow

    • a vessels resistance to blood flow

      • the higher the resistance, the smaller the blood flow