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Main Ideas from Ch. 34 (Types of Blood Vessels :check: (image (High blood…

- - - - Definition: circulatory system in which the heart contracts to pump hemolymph into sinuses and relaxes to draw it back in
        
        Hemolymph :sparkles: --> circulatory fluid (aka interstitial fluid)
        
        Sinus :sparkles: --> space surrounding organs
      - Present in arthropods and some mollusks
      - Pros: :+1: lower blood pressure means requires less energy, blood pressure may serve additional purpose for some organisms
      - :checkered_flag: Think: consists of 1. heart, 2. circulatory fluid (hemolymph), 3. sinuses
    - - Definition: circulatory system in which one or more hearts pumps blood into large blood vessels that branch off into smaller ones (infiltrating organs and tissues)
        
        Blood :sparkles: --> circulatory fluid
      - Present in annelids (earthworms), most cephalopod mollusks (squid, octopus), and all vertebrates
        
        Cardiovascular system :sparkles: --> characteristic of vertebrates; consists of muscular pump (heart), interconnecting vessels (arteries, capillaries, veins), and circulatory fluid (blood)
        
        Single circulation :sparkles: --> blood passes through heart once in each complete circuit
        
        Double circulation :sparkles: --> blood passes through heart twice in each complete circuit
      - Pros: :+1: high blood pressure means effective delivery of oxygen and nutrients to large, active organisms; good for regulation of blood distribution to organs
      - :checkered_flag: Think: consists of 1. heart, 2. circulatory fluid (blood), 3. vessels
- - - - Gas exchange occurs in capillaries of lungs (blood loads oxygen and unloads carbon dioxide)
        
        Oxygen-rich blood flows through the pulmonary veins to get to the left atrium and pass through the left atrioventricular valve leading into the left ventricle
        
        Left ventricle pumps oxygen-rich blood out through the systematic semilunar valve and into the aortic arteries (or aorta) which branches off to supply oxygen to body tissues
        
        Gas, nutrient, and waste exchange occurs in capillaries of body tissues (oxygen diffuses into tissues, and carbon dioxide diffuses into blood)
        
        Oxygen-poor blood flows through the inferior vena cava (coming from trunk and hind limbs) and the superior vena cava (coming from head, neck, and forelimbs) to get to the right atrium and pass through the right atrioventricular valve leading back into right ventricle
        
        REPEAT
- - - - Atria and ventricles relax
        
        For half the cycle, blood returning from large veins flow into atria and ventricles through atrioventricular (AV) veins
    - - Atria contract and ventricles relax
        
        Atria contract briefly to force any remaining blood into ventricles
    - - Atria relax and ventricles contract
        
        Ventricles contract during the remainder of the cycle to pump blood into large arteries through semilunar valves
- - - - Pacemaker cells in atrioventricular (AV) node
        
        Pacemaker cells in the sinoatrial (SA) node are autorhythmic
        
        Autorhythmic :sparkles: --> repeatedly contract and relax without signal from nervous system
        
        Pacemaker cells set the rate and tempo of cardiac cells so muscles can contract in unison
        
        Pacemaker cells produce rapid electrical signals
        
        Pacemaker cells are regulated by physiological cues (aka standing up vs. sitting down) and hormones and temperature (aka body is stressed so body temp. rises)
    - - Medulla oblongata in brain
        
        Medulla oblongata is one of the most basic structures of our brains that almost all animals have
        
        Medulla onlongata controls heart rate through the autonomic nervous system
        
        Sympathetic (fight or flight) --> increases heart rate
        
        Parasympathetic (rest and digest) --> decreases heart rate
  - - - During atrial contraction, electrical impulses reach the AV node, delaying the electrical impulse for ~0.1 s
        
        This delay allows for for the atria to completely empty before the ventricles contract
        
        After this delay, the electrical impulse spreads to the heart apex, then to ventricles and Purkinje fibers, causing contraction
- - - - Function: helps with molecule diffusion between blood and interstitial fluid (think: appears as a net in body tissues and organs because they come within close contact to cells)
      - Structure: endothelium + basal lamina; smallest diameter; very thin walls (ideal for diffusion)
    - - Function: carries blood away from heart
      - Structure: endothelium + thick layer of smooth muscle + thick layer of connective tissue (ideal for withstanding high blood pressure and maintaining blood flow); hormones and nervous system signals act to dilate or contract arteries to control blood flow
        
        Vasodilation increases blood flow and decreases blood pressure; vasoconstriction decreases blood flow and increases blood pressure
    - - Function: carries blood toward heart
      - Structure: endothelium + thin layer of smooth muscle + thin layer of connective tissue; valves (help maintain unidirectional blood flow)
- - - - Blood pressure (hydrostatic pressure) :sparkles: --> drives fluid out of capillaries into tissues
      - Blood proteins (osmotic pressure) :sparkles: --> presence of these proteins draw fluid out of tissues and back into capillaries
      - These forces are opposing so there is a net loss of fluid from capillaries
    - - Arterial end --> blood pressure is higher than osmotic pressure --> net pressure out
      - Venous end --> osmotic pressure is higher than blood pressure --> net pressure in