Cardiovascular System PDF

Unit 7 Blood and the cardiovascular system 1 ORGAN SYSTEMS OF THE BODY: cardiovascular system Cardiovascular/Circulatory System Heart and system of vessels (arteries, veins, capillaries) Circulate blood in a closed system Transportation...

Unit 7 Blood and the cardiovascular system 1 ORGAN SYSTEMS OF THE BODY: cardiovascular system Cardiovascular/Circulatory System Heart and system of vessels (arteries, veins, capillaries) Circulate blood in a closed system Transportation (oxygen, carbon dioxide, nutrients, hormones, etc) Blood: major transportation system in the body; consists of plasma (gasses, proteins, ions, water) and formed elements (cells) Heart: muscular organ that consists of 4 chambers; coordinated contractions ensure circulation of blood throughout the body 2 HEART FUNCTION AND BLOOD CIRCULATION Protected in the thoracic cavity between the sternum and thoracic vertebrae Hollow organ – 4 chambers: 2 atria (upper chambers) 2 ventricles (lower chambers) 4 valves: 2 Atrioventricular valves (AV) 2 semilunar valves (SL) Cardiac output: 5L/min in normal resting adult, compare this with 4-6L of blood in circulation 3 HEART FUNCTION AND BLOOD CIRCULATION 2 Atria (1 atrium): Upper chambers of the heart Compared to ventricles: smaller, thinner walls, and less muscular “receiving chambers” – blood enters from the veins LV 2 ventricles: RV Lower chambers of the heart “discharging chambers” – blood pumped out of heart into arteries via the ventricles 4 HEART: VALVES Valves allow blood to flow in one direction (i.e. from atrium to ventricle) Atrioventricular valves (AV): 1. bicuspid/mitral (between left atrium and left ventricle) 2. tricuspid (between right atrium and right ventricle) Semilunar valves (SL): 1. aortic (allows blood to flow out of the left ventricle to the aorta) 2. pulmonary (allows flow out of the right ventricle to the lungs) 5 * Know these locations 6 HEART: VALVES The sound of the heartbeat results from the closing of the valves… Often heard as a “lub-dup” sound “Lub” is the atrioventricular valves (AV valves) closing “Dup” is the pulmonary and aortic valves closing (semilunar valves) 7 HEART: CONTRACTIONS Systole- contraction Diastole- relaxation Atrial systole contraction: contraction of the atria (pushing blood into the ventricles) Ventricular systole contraction: contraction of the ventricles pushing blood to 1) the lungs or 2) the body Contractions accomplished by the myocardium (middle cardiac layer of the heart) 8 9 HEART FUNCTION AND BLOOD CIRCULATION Systole – contraction of the heart Diastole – relaxation of the heart Left and right side of the heart act as separate pumps! Pulmonary circulation – blood flow from right ventricle to the lungs and back to the left atrium; blood receives oxygen from the lungs Systemic circulation – blood flow from the left ventricle to the rest of the body and back to the right atrium; deliver oxygen-rich blood to the body 10 BLOOD FLOW THROUGH THE HEART Blood flow occurs through blood vessels: Veins (brings blood to heart, mostly deoxygenated blood) 11 Arteries (brings blood away from heart, mostly oxygenated blood) SYSTEMIC AND PULMONARY CIRCULATION OF THE BLOOD 12 BLOOD VESSELS From the heart (LV) To the heart (RA) Arteries: Veins: (aorta > arteries > (venules < veins < arterioles) vena cavas) Capillaries: only one cell thick, allowing for oxygen, glucose and wastes to pass across rapidly to the tissues BLOOD VESSELS 14 BLOOD VESSELS: structure 15 BLOOD VESSELS: structure Veins (not arteries) have valves to prevent retrograde blood flow One Way Valves Arteries and veins have: endothelial layer (tunica intima): thin cells that line vasculature smooth muscle layer: (tunica media) important for blood pressure regulation; thicker in arterial walls to deal with the higher blood pressure connective tissue layer (tunica externa) for structural support; thicker in veins due to retrograde blood flow 16 CAPILLARIES Blood flow Blood flow Capillaries serve as exchange vessels Deliver nutrients and compounds from the blood to the tissues (glucose, oxygen) Carry cell byproducts form the tissues to the blood (CO2) Arterial end has high pressure – enables the movement of substances from the blood into the tissue (blue arrow ) Venous end has lower pressure – enables the movement of substances from the tissues into the blood (red arrow ) CORONARY BLOOD CIRCULATION The heart needs oxygen and nutrients as well… they use their own arteries/veins (coronary arteries/veins) Coronary Arteries – branch off of the Coronary Veins – veins that surround the aorta to deliver oxygenated blood to heart heart to remove deoxygenated blood (feeds into the vena cava) Major blockage of coronary arteries results in ischemia (lack of oxygen) to the heart muscle and the tissue dies… no heart muscle + no pumping = no life This is the basic explanation of a myocardial infarction (MI) or a heart attack CELLS OF THE HEART Recall: the muscle is a type of muscle (cardiac muscle) There are two main types of muscle cells (cardiomyocytes): Contractile cells – bulk of the cells; responsible for contracting in order to pump blood through the heart and throughout the body Conducting cells – function similar to neurons; initiate and propagate an action potential that travels through the heart triggering contraction (Cardiomyocytes have gap junctions that allow ions to travel from one cell to another) 19 NEURAL STIMULUS OF THE HEART Cardiac muscles contract rhythmically and represent involuntary muscle contraction (contractile cells) Coordinated by electrical signals (action potentials via conducting cells) The heart is regulated by the autonomic nervous system Sympathetic nerves initiate contraction (comes from spinal cord) Parasympathetic nerves decrease heart rate (comes from brain) Action potential begins at the sinoatrial node (SA node) Electrical current is passed along through specialized muscle cells: atrioventricular node (AV node), bundle of His, Purkinje fibers Electrical current can travel from one cell to another due to intercalated discs 20 NEURAL STIMULUS OF THE HEART Action potential: SA Node (aka: pacemaker) à AV node à bundle of His à Purkinje fibers Reaction: Atria contract à ventricles contract 21 NEURAL STIMULUS OF THE HEART Electrical current generated can be detected by an electrocardiograph to generate an electrocardiogram (ECG or EKG) RECALL: action potentials “Electrical” activity is propagation of a charge differential down the length of the axon…also known as an action potential. It takes advantage of the inherently negative charge inside the neuron and replaces it with a positive charge (caused by an influx of Na+ ions). The process of going from a negative to a positive charge is called depolarization. Currents move from one cell to the next through 23 gap junctions NEURAL STIMULUS OF THE HEART: ECG Depolarization – action potential that leads to contraction Repolarization – begins the relaxation phase of the cardiac muscle 3 distinctive waves: P wave – depolarization of the atria QRS complex – depolarization of the ventricles T wave – repolarization of the ventricles 24 NEURAL STIMULUS OF THE HEART: ECG 25 SUMMARY: HEART FUNCTION 26 CARDIAC DYSRYHTHMIAS (may lead to cardiac arrest) Normal Tachycardia: fast HR - >100 beats per minute Fibrillation: improper conduction of ventricles (or atria) Heart block – delays or stops transmission in the conduction system Bradycardia (not always a bad thing): slow HR -