The Blood System

Annotations:

• ~lungs used by mammals for gas exchange are supplied with blood by a separate circulation ~blood capillaries in lungs pumped at low pressure  ~blood goes back to heart to be pumped back again  Pulmonary Circulation-to and from lungs  Systemic Circulation-to and from other organs (heart muscles too) ~pulmonary circulation receives deoxygenated blood that has returned from the systemic circulation  ~systemic circulation receives oxygenated blood from pulmonary circulation

1. The Cardiac Cycle

Annotations:

• ~heart can contract without motor neurons, contraction called myogenic. ~membrane of heart muscle cell depolarizes when the cell contracts and this activates adjacent cells so they contract  !region with the fastest rate of spontaneous beating is a small group of cells in the wall of the right atrium called "Sinoatrial Node" Sinoatrial Node-initiates each heartbeat, due to membrane of cell first to depolarize in each cardiac cycle 

1. Initiating the Heartbeat

   Annotations:

   • ~Sinoatrial node (also called 'Peace Maker") initiates each heartbeat, and sets pace for the beating ~the peacemaker can be replaced by an artifical peacemaker, that can be implanted in the wall of the heat, the electrodes initiates each heart beat
2. Atrial and Ventricular Contraion

   Annotations:

   • ~Sonoatrial node initiates heartbeat by contracting and sending electric singal that epreds through the wall of the artria, causes the whole atria to contract.
3. Changing the Heart Rate

   Annotations:

   • ~Senoatrial node responds to signals from outside the heart  ~signals from one of nerves causes the senoatrial node to increase frequency of heartbeats  ~the two nerves originating from the brain in a region called "Cardiovascular centre" ~The cardiovascular centre recieves inputs from receptors, these receptors monitor blood pressure,pH, and oxygen concentraion  ~Low blood pressure, oxygen concentration, pH means the heart needs to speed up, increasing the flow rate of the blood, providing more oxygen, and removing carbon dioxide ~High blood pressure, oxygen concentration, and ph means heat need to slow down 
   1. Epinephrine

1. Heart Structure

1. Arteries

   Annotations:

   • ~Arteries are vessels that carry blood from the heart to the tissue. ~Ventricles are the main pump chambers of the heart, they are thick stronge muscles, due to high pressure.  ~elastic tissue contains elastic fibers that stores energy when its stretches (stretches at the peak of a pumping cycle), and recoils back to help propel blood down the artery.~each organ supplied with blood from one/more arteries 
   1. Artery Walls

      Annotations:

      • ~Concentration of smooth muscle (in artery wall) determine diameter of the lumen and rigidity of the arteries, therefore controlling overall flow through them. ~Artery walls work with the heart to facilitate and control blood flow.  ~walls have to be strong to withstand constantly and intermittently high blood pressure without bulging outwards(aneurysm) or bursting Layers of Artery Walls -Tunica Externa: A tough outer layer of connective tissue -Tunica Media: Thick layer containing smooth muscle and elastic fibers  -Tunica Intima: Smooth endothelium form lining of artery 
   2. Arterial Blood Pressure

      Annotations:

      • Systolic Pressure-peak pressure reached in an artery, pushing the wall of artery outwards, and storing potential energy in elastic fibers  Diastolic Pressure-minimum pressure inside an artery ~at the end of a heartbeat, the pressure fall sufficiently, the stretched elastic fibres squeeze blood in lumen, this mechanism saves energy and pressure from getting too low  Vasoconstriction-a process when the circular muscles in the wall of the artery form a ring so when they contract the circumference is reduced and the lumen is narrowed, increases blood pressure in arteries ~vasoconstriction of arterioles restrict blood flow to the part of the body that they supply and the opposite process (vasodilation) increases it  
2. Capillaries

   Annotations:

   • ~Are the narrowest blood vessels, they branch off and rejoin repeatedly to form a Capillary Network. Capillaries transport blood to most of organs. ~Capillary walls contain on layer of thin endothelium cells, they haves pores and are very permeable, ~'Tissue Fluid(contain glucose, oxygen, and other substances, apart from large protein molecules) flows between cells to allow them to absorb useful substances and get rid of waste products ~permeability of capillaries depends on tissue(can change over time),capillaries repair and remodels themselves
3. Veins

   Annotations:

   • Veins-transport blood from capillary network back to the heart  ~blood is at low pressure, meaning they don't need thick walls and is wider to hold more blood (80% of blood in veins) ~blood flow assisted by gravity and pressure by other tissue, concentration of muscles works like a pump  each part of the body is served by one/more veins 
   1. Valves in Veins

      Annotations:

      • ~to maintain circulation veins contain valves, to stop backflow of blood. ensure blood circulates in the body 
4. Identifying Blood Vessels