The transport system Topic 6.2

Assessment Statements Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood through the heart State that the coronary arteries supply heart muscle with oxygen and nutrients Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline) Explain the relationship between the structure and function of arteries, capillaries and veins State that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat.

The human heart Pair of side-by-side pumps Two atria –Thin-walled collection chambers Two ventricles –Thick-walled muscular pump –Produces force known as blood pressure Blood moves through large arteries, smaller arteries, arteriole, capillary bed, venule, larger vein, largest veins

Two circuits Pulmonary circuit –Right side of heart sends blood to lungs Systemic circuit –Left side of heart sends blood to body cells

Pulmonary circulation 1.Deoxygenated blood comes from body 2.Enters heart through vena cava 3.Blood collects in right atrium (RA) 4.Moves through rt. atrioventricular (AV) valve to rt. ventricle 5.RA contracts forcing any remaining blood into the right ventricle (RV) 6.Once a volume of blood has accumulated in the RV, it begins to contract

7.Rt. AV valve closes to prevent backflow to the RA (closing of valve creates ‘lub dub’ sounds heard through a stethoscope) 8.Dramatic increase in blood pressure (BP) inside the RV opens the right semilunar valve 9.Blood enters pulmonary artery (PA) 10.Blood leaves PA and enters lungs through smaller arteries and capillaries 11.RBCs drop off carbon dioxide and pick up oxygen

Systemic circulation RBC enters left atrium (LA) Blood accumulates in LA Blood travels through left AV valve and enters the left ventricle (LV) LV contracts Left AV valve closes to prevent backflow into the LA Dramatic increase in bp inside the LV opens the left semilunar valve Blood enters the aorta and then to body

Coronary arteries First arteries to receive blood that has left the heart Coronary arteries branch into the heart muscle itself Supply the heart with oxygen and nutrients

Control of heart rate The majority of tissue making up the heart is cardiac muscle It contracts and relaxes without nervous system control (known as myogenic muscle contraction) Needs to be controlled in order to keep the timing of the contractions unified and useful Right atrium conatins a mass of tissue within its walls known as the sinoatrial node (SA node)

Sinoatrial Node Mass of tissue acts as the pacemaker for the heart Sends out an ‘electrical’ signal to initiate the contraction for both atria Resting heart rate of 72 bpm, signal from the SA node is sent out every 0.8 seconds

Atrioventricular node Also within the right atrium AV node receives the signal from the SA node, waits approximately 0.1 seconds and then sends out another ‘electrical’ signal Signal goes to the ventricles and results in their contraction

Medulla During times of increased body activity, the heart rate needs to increase to get rid of excess CO 2 and gain more O 2 As CO 2 levels rise, an area of the brainstem called the medulla chemically senses the increase Signal sent through the cardiac nerve to the SA node to increase heart rate to an appropriate level Timing is changed

After exercise Level of CO 2 in bloodstream begins to decrease and another signal is sent from the medulla by means of the vagus nerve the SA node once again takes over the timing of the heart rate

Other influences During periods of high stress or excitement, adrenal glands secrete adrenaline into the bloodstream Causes SA node to ‘fire’ more frequently than it does at the resting heart rate and thus heart rate increases

Arteries Arteries are blood vessels taking blood away from the heart that has not yet reached a capillary Have thick smooth muscle layer that is used by your autonomic nervous system to change the inside diameter of the blood vessels which helps to regulate bp Arteries→arterioles→capillary bed→venule

Capillaries Blood enters a capillary bed, much of the pressure is lost blood cells make their way through one at a time Chemical exchanges occur through the single-cell thickness of capillaries

Veins Veins receive blood at a relatively low pressure from the capillary beds Blood flow is slower Collect blood from capillaries and return it the heart Veins have thin walls and a larger internal diameter Have many internal passive valves that help keep the slow-moving blood consistently moving towards the heart

Quick comparison ArteryCapillaryVein Thick walledWall is 1 cell thickThin walled No exchangesAll exchanges occurNo exchanges No internal valves Have internal valves Internal pressure highInter pressure lowInternal pressure low

Components of blood ComponentsDescription PlasmaLiquid portion of blood ErythrocytesRed blood cells (carry oxygen and carbon dioxide) LeukocytesWhite blood cells (phagocytes and lymphocytes) PlateletsCell fragments (assist in blood clotting)

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