BIO 104 5/9/96

Purpose of the heart:
     -transport blood to the lungs then the rest of the body
     -we have a closed circulatory system
Circulatory Illnesses:
     -Heart Attack:  the heart muscle is not getting enough
          oxygen and the heart begins to die.
          -Coronary Artery:  it feeds blood to the heart 
          straight from the aorta.
               Embolism occurs when the coronary artery get 
               blocked.
          Risk Factors:  
               1. diet
               2. exercise
               3. smoking
     Coronary Bypass
          -The surgeon takes a piece of a vein, most likely from
          the leg, and connects it to the coronary artery;  by-
          passing the blocked section of the artery.
     Angina:  heart pain when there is not enough oxygen getting
          to the heart.

     The heart contracts about 2.5 billion times in an average
     persons life-span.
          -That is enough blood to fill 13 super-tankers (13
               million barrels of liquid)
     Cardiac Output
          Heart rate x stroke volume
          -If you had a heart rate of 72, you would multiple that
               by 80 to get stroke rate.  The heart pumps 80 ml
               of blood per contraction.
          5-6 liters of blood is pumped by the heart per minute.
               -The heart almost pumps the body's whole supply of
               blood in one minute.
     What causes the heart to contract?
          The pacemaker is stimulated by autonomic nerve fibers-
          then an impulse is sent to the A-V node and that signal
          is sent to the purkinje fibers and the muscles
          contract.
     The heart rate is effected by environmental conditions, such as stress
     and confrontation, because it is controlled by the autonomic nervous
     system.  This action takes place in the brain stem.
               In the brain stem there is a cardiac center:
               It does 2 things:
               1. activates the sympathetic nerves (increase the
                    heart rate)
                    or
               2. inhibit the parasympathetic nerves (slows the
                    heart rate)
          1.  When the heart is stimulated the transmitter is 
               norepinephrine (adrenaline) 
               -This stimulates the heart rate and will cause the
               blood vessels to constrict and blood pressure to
               increase.
          2.  When the heart is inhibited the transmitter of this
               action is acetylcholine.
               -This inhibits the heart rate and the blood
               vessels dilate and the blood pressure decreases.
          3.  Both of these actions operate through the sinoatrial node.

     The left ventricle is very large.
          -It must pump blood through the entire body; so our
               blood is under a lot of pressure (but the arteries
               use their muscles to push the blood through the 
               body)
          There are two types of pressure:
          1. systolic
          2. diastolic
     High blood pressure:
          -Body fluids are regulated through the kidneys and high
          blood pressure will damage the kidneys.
          -High blood pressure can lead to the bursting of a
          blood vessel, and when this occurs in the brain it is a
          stroke.

     Pressure doesn't move blood through the body.  It is muscle 
          contractions that do.  The blood is prevented from
          going backwards in the heart by a series of valves.
     
Lymphatic system:
     -has lymph nodes which contain ducts
     -contains phagocytes, which also have ducts
     -used to transport lipids
     -connected with the spleen which filters the lymph
     -The lymph system carries excess fluids and fats, but also 
          filters the blood.
          -When you are sick your lymph nodes swell.
Clotting 
     -depends on the amount of fibrin.
     -You have a damaged vessels, then binds to a "factor 10" and
          it converts it to factor 10a.  Factor 10a activates a
          protein, prothrombin, found in the plasma, which is 
          converted to form thrombin.  Thrombin takes fibrinogen
          to make fibrin.  Fibrin forms a mesh like network, and
          traps blood cells to form a blood clot.