1. Quick Comparison ArteryCapillaryVein Thick walledWall is 1 cell thickThin walled No exchangesAll exchanges occurNo exchanges No internal valves Have internal valves Internal pressure highInternal pressure low

2. Components of blood ComponentDescription PlasmaLiquid portion of the blood ErythrocytesRed blood cells (carry oxygen and carbon dioxide) LeucocytesWhile blood cells (phagocytes and lymphocytes) PlateletsCell fragments (assist in blood clotting)

3. Transported by blood What is transportedWhat it is or does NutrientsGlucose, amino acids, etc OxygenReactant needed for aerobic cell respiration Carbon dioxideWaste product of aerobic cell respiration HormonesTransported from gland to target cells AntibodiesProtein molecules involved in immunity UreaNitrogenous waste (filtered out of the body by the kidneys) HeatSkin arterioles (can change diameter in order to gain or lose heat)

4. Controlling heart rate Majority of tissue in heart is muscle Cardiac muscle spontaneously contracts and relaxes without nervous system control; known as myogenic muscle contraction The myogenic activity has to be controlled in order to keep the timing of the contractions unified and useful

5. SA Node Right atrium contains a mass of tissue within its walls known as the sinoatrial node (SA node) Acts as a pacemaker for the heart Sends out electrical signal to initiate the contraction of both atria For a person who has a resting heart rate of 72 bpm, the signal from the SA node is sent out every 0.8 seconds

6. AV Node Also in right atrium Receives signal from SA node Waits ~0.1 second then sends out another electrical signal This signal goes to the much more muscular ventricles and results in their contraction This is why both atria and then both ventricles contract together

7. Exercise Heart rate has to be increased Increased demand for oxygen for cell respiration Need to get rid of higher levels of carbon dioxide

8. Physiology of exercise As exercise begins, carbon dioxide levels increase The medulla in your brainstem sends a signal through a cranial nerve (called the cardiac nerve) to increase heart rate to appropriate level This signal is sent to the SA node; to alter timing

9. After excercise Carbon dioxide levels in blood stream decrease Another signal sent to medulla Another signal then sent by a different cranial nerve called the vangus nerve The vangus nerve will send a signal again to the SA node once again to change the timing of the heart

10. Heart rate and chemicals Most common chemicals for your heart is adrenaline (hormone) During periods of high stress or excitement, the adrenal glands secrete adrenaline into bloodstream This causes the SA node to “fire” more frequently than it does at the resting heart rate and therefore heart rate increases