Topic 6.2 and Option H5 – The Transport System

The Transport System In order to maintain homeostasis, various materials must be transported through the body Mammals have a closed circulatory system – meaning materials are transported within vessels The medium for transport through the body is blood

Blood Form of connective tissue made of cells suspended in a liquid (plasma) Average human body has 4-6 liters. Functions: Transporting materials through the body Transfer heat to body surface Defend body against disease 6.2.7

Blood and Transport Blood is responsible for transporting many materials through the body: Nutrients Hormones Antibodies Urea (nitrogen waste) Oxygen Carbon dioxide Oxygen and carbon dioxide are associated with red blood cells, all other materials dissolve in blood plasma 6.2.7

Blood Components Plasma – 55% Red blood cells – 45% White blood cells less than 1% Platelets 6.2.6

Blood Plasma Components of Blood Plasma: Water – 90% - solvent for carrying materials Plasma Proteins Fibrinogen – clotting Globulins – defense Albumins – maintain osmotic balance, viscosity Dissolved nutrients Hormones Waste materials 6.2.6

Blood Cells Erythrocytes (red blood cells) – 90% of blood cells Transport oxygen and carbon dioxide Leucocytes (white blood cells) – Phagocytes – non-specific defense Lymphocytes – produce antibodies – specific defense Thrombocytes - platelets 6.2.6

Blood Components 6.2.6

Structure of the Heart Cone-shaped organ about the size of a clenched fist Located just beneath the sternum (breastbone) Base Point where large vessels attach (pulmonary artery, aorta) Apex Cone-shaped end, points down

Heart Chambers Chambers – collect and pump blood to lungs and body Left and right atria – collection chambers for blood returning to heart from body and lungs Left and right ventricles – pumping chambers to send blood out to lungs and body Right ventricle pumps blood to lungs Left ventricle pumps blood to body 6.2.1 6.2.3

Structure of the Heart 6.2.1

Heart Chambers Heart Chambers

Heart Valves Valves – control direction of blood flow through the heart Atrio-ventricular (AV) valves – separate atria from ventricles Right = tricuspid, Left = bicuspid (mitral valve) Semilunar valves – located at two exits of heart (pulmonary artery and aorta) Right = pulmonary, Left = aortic 6.2.1 6.2.3

Heart Valve Function Heart valves are flaps of tissue controlled by the flow of blood As blood flows through the heart the flaps are pushed open – allowing blood to flow from chamber to chamber If blood tries to flow backward – the valves close shut – preventing backflow 6.2.3

Heart Valves Heart Chambers

Great Vessels Vena cava (superior and inferior) – carry blood into right atrium Pulmonary arteries – carry blood from right ventricle to lungs (for O2) Pulmonary veins – carry blood from lungs to left atrium Aorta – carries blood from left ventricle to body Coronary arteries – supply the heart muscle with O2 and nutrients 6.2.2

Structure of the Heart 6.2.1

Quick Review… Aorta Superior vena cava Right atrium Tricuspid valve Right ventricle Inferior vena cava Pulmonary artery Pulmonary veins Left atrium Mitral valve Aortic semilunar valve Left ventricle

Double Circulation Heart pumps blood through two circuits: Pulmonary circuit – Right Atrium/Ventricle to lungs (for O2) Systemic circuit – Left Atrium/Ventricle to body

Double Circulation Pulmonary Circuit: Systemic Circuit: Body  vena cava  R. A. R. A.  tricuspid AV valve  R. V. R. V  Pulmonary semilunar Valve  P. Artery  Lungs (for O2) Lungs  P. Vein  L. A. Systemic Circuit: L. A.  bicuspid (mitral) AV valve  L. V. L. V.  Aortic semilunar valve Aorta body

Blood Vessels Arteries – carry blood AWAY from heart Thick-walled vessels to withstand high pressure Outer layer of collagen and elastic fibers allow vessel to stretch and recoil Middle layer of smooth muscle to help pump Lumen – narrow interior maintains high pressure 6.2.5

Blood Vessels Veins – RETURN blood to the heart Smaller and thinner-walled than arteries Low pressure – little danger of bursting Wide lumen to accommodate slow moving blood Thin walls can be flattened to help move blood Contain valves to prevent backflow 6.2.5

Arteries and Veins Artery Vein 6.2.5

Blood Vessels Capillaries – exchange materials in blood with body tissue Small microscopic vessels Thin porous walls made of single layer of endothelium Very narrow lumen Moderate pressure 6.2.5

Blood Vessels Heart Chambers 6.2.5

Control of the Heart Myogenic – heart beats on its own – does not require nervous system control Cardiac muscle contractions are stimulated by electrical impulses generated by the sinoatrial node (SA node) and atrioventricular node (AV node) Located in wall of right atrium 6.2.4

The Heart’s Electrical System Sinoatrial node (SA node): The “pacemaker” – sets the rhythm of the heart Sends impulse directly into atria = atrial contraction Atrioventricular node (AV node): Receives message from SA node Sends impulse through conducting fibers into ventricle = ventricular contraction Can work as the pacemaker in the absence of SA node 6.2.4 H.5.3

The Heart’s Electrical System 6.2.4 H.5.3

Pathway of Cardiac Impulse Impulse originates in SA node Spread rapidly over right and left atria Atria contract – blood flows into ventricles Slight delay – ensures ample ventricular filling of blood Impulse enters AV node Moves along Bundle of His Branches to right and left bundle fibers Spreads rapidly along Purkinje fibers Ventricles contract (beginning at apex and traveling up) – blood flows into arteries 5.2.3 H.5.3

Pathway of Cardiac Impulse…Quick Review

Electrocardiogram (ECG) Measures electrical activity of the heart. P- wave Depolarization of the atria, just before contraction QRS wave Depolarization of ventricles. T-wave Repolarization of ventricles Use to detect damage to the heart

Control of Heart Rate SA node can be influenced by nervous system Vagus nerve connects nervous system to heart Parasympathetic action will slow heart rate down Sympathetic action will speed heart rate up SA node also influenced by hormones and temperature. Epinephrine from adrenal gland speeds heart rate up Increased body temperature increases heart rate 6.2.4

The Cardiac Cycle Each heart beat involves 4 phases of heart muscle contraction and relaxation – the cardiac cycle Useful terms: Diastole – relaxed state Systole – contracted state

The Cardiac Cycle Diastole Atrial Systole All four heart chambers relaxed Atria fill with blood Atrial pressure increases and opens AV valves Slow flow of blood into ventricles Passive ventricular filling Atrial Systole SA node fires and atria contract Atrial pressure rises rapidly and remaining blood pushed into ventricles Active ventricular filling H.5.1

The Cardiac Cycle H.5.1

Cardiac Cycle Ventricular systole Ventricles contract Ventricular pressure increases sharply AV valves forced closed Semilunar forced open, sending blood into arteries. At the same time the atria reenter diastole and begin filling with blood from veins H.5.1

The Cardiac Cycle Ventricular diastole – Ventricles relax Ventricular pressure decreases Semilunar valves close AV valves open, sending slow flow blood from atria to ventricles Passive ventricular filling H.5.1

The Cardiac Cycle H.5.1

Heart Sounds The heart is generally thought to have a “lub-dub” sound The “lub” comes from the closing of the AV valves – ventricular systole The “dub” comes from the closing of the SA valves – ventricular diastole H.5.1

Pressure, Volume, and the Cardiac Cycle Atria: Atria fill during ventricular systole and diastole Volume and pressure of atria increase When atrial pressure rises above ventricular pressure, AV valves open and blood flows into ventricles Pressure rise/fall in atria small compared to rise/fall in ventricle H.5.2

Pressure, Volume, and the Cardiac Cycle Heart Chambers H.5.2

Pressure, Volume, and the Cardiac Cycle Ventricles: Ventricles fill passively during atrial diastole and actively during atrial systole Volume and pressure of ventricles increase During ventricular systole volume decreases and pressure rises sharply and blood flows into arteries Pressure much greater in left ventricle than right ventricle – why? H.5.2

Pressure, Volume, and the Cardiac Cycle Heart Chambers H.5.2

Blood Pressure Hydrostatic pressure of blood against vessel walls Much greater in arteries than in veins – why? Read as systolic/diastolic – e.g. 120/80 Systolic Pressure during heart contractions Blood pressure at highest (120 mmHg) Diastolic Pressure during heart relaxation Blood pressure drops (80 mmHg)

Blood Pressure and Velocity Heart Chambers

Atherosclerosis Lipid deposits build up on inside of artery walls Limits blood flow and may cause formation of blood clots Walls of damaged arteries begin to thicken and harden H.5.4

Artherosclerosis H.5.4 H.5.4

Coronary Thrombosis Begins with artherosclerosis in coronary arteries Coronary arteries supply heart walls with blood If coronary arteries are totally blocked by clot, heart cells are unable to respire or contract Myocardial infarction = heart attack H.5.4

Coronary Heart Disease Wide spectrum disease of the heart involving artherosclerosis, coronary thrombosis, and heart muscle damage over time Risk factors include: Genetics, gender (sorry guys), smoking, obesity, diet (high fat, low fiber), exercise (or lack thereof) H.5.5