: thick middle layer; cardiac muscles : thin inner layer; endothelial lining

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1 Bio 1102 Lecture 5 (guided) Chapter 8: Heart & Blood Vessels Functions of Circulatory System: To carry from lungs to all cells, tissues, and organs of body To carry from digestive system to all cells, tissues and organs of body The heart is the organ that pumps blood through the body Heart is located between the Three layers of the heart: : thin outer layer; protects & anchors : thick middle layer; cardiac muscles : thin inner layer; endothelial lining 2 Circuits of Blood Flow: Circuit: blood pumped to and from the lungs Circuit: blood pumped to and from the rest of the body Blood that has been circulated through body in the Systemic Circuit has lost its oxygen and picked up carbon dioxide Heart pumps this blood to lungs (via the Pulmonary Circuit) where carbon dioxide is expelled and oxygen is replenished chambers of the heart 2 on the left: pumps oxygenated blood from the lungs through the systemic circuit 2 on the right: pumps deoxygenated blood from the body through the pulmonary circuit Note: left and right not as you read the diagram, but in relation to the organ Blood returning from systemic circuit enters heart via two large veins (superior and inferior ) Superior, from upper part of body (head, neck, and arms) Inferior, from lower part of body Blood enters the right (upper chamber), is pumped into right ventricle, and then through the pulmonary arteries to the 1

2 7 8 Blood is oxygenated in lungs Blood returns to left atrium of heart via Systemic System begins Blood enters left ventricle Thicker-walled than right ventricle Pumps blood to rest of body, via the Largest artery in body Heart valves 4 valves in heart control direction of blood flow Valves between artria and ventricles = valves Anchored to walls of ventricles by Right atrioventricular valve = valve Left atrioventricular valve = valve (aka mitral valve) Valves between ventricles and arteries are two more valves ( valves) Heart Sounds The sound of the valves closing Incomplete closing of valves can be heard as a Rheumatic fever Heart murmurs can also result from holes in the septum between the ventricles, or other heart defects When blood doesn t flow efficiently through chambers of heart, the heart has to work harder Video of normal heart sounds: =1 Video of heart murmur, due to mitral valve not closing fully 7 Video of heart murmur, due to aortic valve stenosis May result from congenital heart defect, from calcium build up on the valve, or from damage due to infection such as rheumatic fever Control of Heart Rate Heart beats at different speeds depending on your activity level 2

3 Has an internal pacemaker called the Inside wall of Cluster of cells that produce electrical impulses Impulses spread throughout heart (first to atria, then to ventricles) Synchronizes the contractions of atria Signal then travels to another cluster of special cells, the Signal then is distributed to the ventricles by the bundles (in the septum) and then the bundles (see figure 8.13) Without some regulation, SA node would cause heart to beat 100 times per minute at rest too fast Heart control center of brain slows down the SA node On average, impulses from brain slow heart rate to about beats per minute (at rest) When active, impulses from brain are reduced, so heart rate speeds up Other nerves and hormones (e.g. adrenaline) can also work to increase heart rate (up to about 180 beats per minute) Heart beat rate is regulated to meet the needs of the body s cells for Bonus Activity Part 1 This will be a literal activity! You will design an experiment to see the effects of exercise on your heartbeat rates. FIRST, get together in a group of 4-5, and design an experiment to test the effects of exercise on heartbeat rates. You are free to design your experiment as you see fit, with the following guidelines: Be careful, and if someone isn t feeling well, he/she should not participate in any strenuous activity Your data should include an average heartbeat rate for your group at rest and after some form of activity On a piece of paper, write a description of your experimental design, record your raw data, and calculate your averages. Did heart rate increase after the activity your group conducted? By how much? How does this compare with the data from other groups? Heart Attacks Most common type: Caused by blood clots in arteries supplying blood to the heart Often associated with arteries narrowed by Lack of flow to heart starves muscles of oxygen and nutrients, killing cells The damaged area is called an 3

4 What causes plaque formation? Poor diet Smoking Lack of exercise Heredity Stress Severity of the heart attack depends on Diet and plaque formation A high fat diet may be a risk factor for atherosclerosis: Heart Attack Grill restaurant: Warnings of Heart Attack May occur without warning Chest pain ( ) may precede heart attack for several weeks Caused by reduced blood flow to heart Pain in center of chest, spreading to throat, jaw, back, and arms Occurs when person is active, under stress, or exposed to carbon monoxide Taking an during a heart attack can reduce damage reduces Other causes of heart attack Loss of control of heart muscle by sinoatrial (SA) node Heart muscles thus beat independently, reducing flow of blood through heart (= ) Heart stops beating = Heart beat may be restored by applying strong electrical current to chest ( ), or by cardiopulmonary resuscitation (CPR) Applying pressure to breastbone, massaging the heart Treatments Balloon A catheter with a tiny balloon attached is inserted into the artery Chemicals are injected to dissolve the clot Balloon is then inflated 4

5 Opens artery Loosens plaque may be inserted after balloon angioplasty Holds artery open after balloon is removed Coronary bypass surgery Used when coronary arteries are completely blocked by plaque Transplant small pieces of from other locations (usually the leg) into the heart These veins are connected so as to bypass the clog Atherosclerosis Thickening of artery walls due to build up of Too much in blood forms deposits in lining of arteries Can narrow blood vessels, increasing risk of a blockage Can result in heart attack If occurs in vessels leading to or in brain, can cause Can cause increase in blood pressure This, in turn, can damage organs such as the kidneys Aneurysm of artery walls Caused by some diseases, atherosclerosis, and high blood pressure Ballooning of the artery in weakened areas If rupture occurs, blood lost rapidly Often results in death Prevention involves the usual steps: stop smoking, reduce stress, lower blood pressure, exercise and lose weight, etc. may also be helpful Increase good cholesterol (HDL), which removes cholesterol from artery walls Found in oily fish (like salmon, trout, and sardines), the eggs of some chickens (freeranging), milk and cheese from grass-fed cows, and vegetable sources such as flax seed and walnuts Break Blood Vessels 3 Types of Blood Vessels 5

6 Arteries: carry blood Veins: carry blood ; have valves Capillaries: fine, branching network of vessels in tissues Structure of Blood Vessels Inside of vessel = Innermost layer of vessel = A continuation of the lining of heart Flattened cells very smooth; minimize friction Middle layer = muscle with fibers Outer layer = tissue (mostly collagen) Anchors vessels in place Protects vessels Arteries carry blood away from heart, toward in tissues Branch into networks of the smaller and smaller arteries Smallest arteries, which lead directly to capillaries, are called Pressure in vessels as it reaches the arterioles Therefore, they lack the outer layer of connective tissue Also, have thinner layer of smooth muscle Arterioles can regulate amount of blood flow to each capillary by either dilating (allowing more blood to flow) or constricting (reducing blood flow) Sphincter A band of smooth muscle at junction of an arteriole and a capillary Can open or close to adjust blood flow to capillaries : when the arteriole and/or precapillary sphincter constricts to reduce blood flow to a capillary bed : when the arteriole and/or precapillary sphincter relaxes to increase blood flow to a capillary bed Vasodilation and vasoconstriction regulated by hormones, nerve signals, and the local conditions surrounding the vessels Blood pressure Force of blood against walls of blood vessels generated by pumping of heart Highest in ; lowest in and Blood pressure can increase with: Stress/anger Age Plaque in arteries 6

7 High blood pressure can be a symptom of cardiovascular disease 36 Top number (higher number) i pressure The highest pressure of blood against artery walls Occurs when heart ventricles contract and blood is pumped into the arteries Bottom number (lower number) is pressure The lowest pressure of blood against artery walls Occurs when the heart relaxes and re-fills with blood Normal blood pressure is defined as or less Pre- is defined as over a prolonged elevation in blood pressure or greater Can lead to heart attack Capillaries Where nutrients, gases, water, and hormones are delivered to cells, and wastes are carried away from cells Walls consist of layer of cells Microscopic pores in these cells; slits between the cells Materials move across the thin walls of capillaries by At beginning of capillary bed, fluid filtered out of blood includes nutrients and At end of capillary blood, fluid returned to blood includes and waste materials such as urea Veins Once needed nutrients and gases are removed from blood in capillary beds of systemic circuit, blood enters veins This blood contains waste materials (in systemic circuit) Blood pressure in veins, and veins have walls Obstructions can cause bulges ( veins) Eventually, veins of systemic circuit empty this blood into the superior or inferior, and the blood enters the right 41 7

8 Veins have three layers, like arteries, but Outer two layers are much Don t need thick outer layer when blood pressure is low also, a larger Helps them hold a large amount of blood Veins serve as a blood volume reservoir of blood is located in your veins Veins contain one-way valves Prevents How is blood returned to heart through veins? Contraction of Veins pass between skeletal muscles When they contract/relax, they push on the veins Pushes blood toward heart One-way valves Blood cannot flow backwards due to these valves Movements associated with breathing Inhaling puts pressure on veins in At same time, pressure in chest (thoracic) cavity, dilating the veins there This results in blood being pushed from veins in abdomen toward veins in chest Lymphatic System A system of vessels and glands Tissue fluid bathes cells of the body Fluid Materials diffuse through this fluid between capillaries and cells Fluid comes from capillaries; more water leaves capillaries than enters Excess water is picked up by capillaries and ultimately returns to fluid to the circulatory system Drain into veins at base of neck Lymph moves through vessels using gravity or muscle contractions Lymphoid organs (such as the spleen, thymus, and lymph nodes) involved in immune response (to be discussed later) Activity Part 2: On the same sheet with your blood pressure activity, answer the following questions: Define the pulmonary and systemic circuits. Compare and contrast arteries, veins, and capillaries. How does atherosclerosis of the coronary arteries affect the heart? 8

9 45 All for today 9