The Cardiovascular System A&P Spring 2016

Vocabulary Terms Mitral valve Cardiac conduction system Aorta Aortic valve Coronary arteries Cardiac Veins Coronary Sinus Systole Diastole Cardiac cycle Functional Syncytium Cardiac conduction system Sinoatrial node Atrioventricular node A-V bundle Purkinje fibers Pericardium Epicardium Myocardium Endocardium Atria Ventricles Septum Tricuspid Valve Papillary Muscles Pulmonary Valve

Video Introduction Get out a sheet of paper and label it Cardiovascular Facts (be sure to put your name too!) As you watch the video, write down 7 facts to turn in for a grade Cardiovascular System Intro

Structure of the Heart Size and location of the heart Coverings of the heart Wall of the heart Heart chambers and valves Skeleton of the heart Path of blood through the heart Blood supply to the heart

Size and location of the heart Average adult heart is 14cm long and 9cm wide Located within the mediastinum Base of the heart lies beneath the 2nd rib

Size and location of the heart Structures that border the heart: Lungs- laterally Vertebral column- posteriorly Sternum- anteriorly

Coverings of the heart Pericardium- membrane that encloses the heart Consists of 3 layers 1. Fibrous pericardium 2. Parietal pericardium 3. Visceral pericardium ( a.k.a. epicardium)

Coverings of the heart The pericardial cavity Space between the parietal and visceral pericardium Contains serous fluid Reduces friction between the membranes as the heart moves

Wall of the heart Composed of 3 layers 1. outer epicardium 2. middle myocardium 3. Inner endocardium

Wall of the heart Outer epicardium Consists of connective tissue beneath epithelium Also called the visceral pericardium Protects the heart by reducing friction

Wall of the heart Middle myocardium Consists mostly of cardiac tissue Muscle fibers are organized in planes Separated by connective tissue

Wall of the heart Inner endocardium Consists of epithelium and connective tissue Contains elastic and collagenous fibers Also contains blood vessels and Purkinje fibers Purkinje fibers are specialized cardiac muscle fibers

Heart Chambers and valves Heart is divided into 4 hollow chambers 2 upper chambers called atria 2 lower chambers called ventricles Atria Receive blood returning to the heart Ventricles Contract to force blood out of the heart

Test your knowledge! In your notes, answer the following questions: The base of the heart lies just beneath which rib? What is another name for the visceral pericardium? As the heart moves,the serous fluid helps to reduce what? What are the 4 hollow chambers in the heart?

Let's Review What is the pericardium? How many layers are in the wall of the heart? Name them How many chambers are in the heart?

Heart chambers and valves The septum Wall-like structure that separates the left and right atrium and ventricles Blood on one side of the heart never mixes with blood on the other side The atrioventricular (A-V) valve Ensures one way blood flow between the atria and ventricles Tricuspid on the right Mitral on the left

Heart chambers and valves Tricuspid valve Has 3 tapered projections called cusps Permits blood to move from right atrium to right ventricle No backflow Papillary muscles help keep the cusps from opening in the other direction Mitral valve Bicuspid valve Same function as tricuspid valve

Heart chambers and valves Pulmonary Valve Located at the base of the pulmonary trunk Allows blood to leave the right ventricle Tricuspid Aortic valve Located at the base of the aorta Allows blood to leave the left ventricle tricuspid

Skeleton of the heart Made of dense masses of connective tissue Provide attachments and support for: The septum Heart valves Muscle fibers

Path of blood through the heart Blood enters the right atrium (deoxygenated) Blood enters the right ventricle (via heart contraction) Blood is pushed out of the heart and to the lungs (contraction) Blood enters the left atrium (oxygenated) Blood enters the left ventricle (contraction) Blood is pushed out of the heart and to the body

Blood supply to the heart Coronary Arteries Branches of the Aorta Supply oxygenated blood to the tissues of the heart Cardiac Veins Branches of the Coronary Sinus Drain deoxygenated blood from the tissues of the heart

Think about it... What would happen if the structure of the heart was faulty? Ex, Atrial Septal Defect (ASD) Atrial Septal Defect Ex, Valvular Heart Disease Valvular Heart Disease

What's coming up... Next, we will discuss the actions of the heart

The heart actions Cardiac cycle Heart sounds Cardiac conduction system Electrocardiogram Regulation of the cardiac cycle

Cardiac Cycle This cycle constitutes one complete heart beat 3 basic steps Terms to know: Systole- contraction of heart chamber Diastole- relaxation of heart chamber

Cardiac Cycle Step 1 Atria contract (Atrial Systole) Ventricles relaxed (Ventricular Diastole) Blood is pushed from atria into the ventricles

Cardiac Cycle Step 2 Atria relax (?) Ventricles contract (?) Blood is pushed from the ventricles into the arteries (out to the body)

Cardiac Cycle Step 3 Atria and ventricles both relax for a brief moment (?) Atria fill up with blood again

Cardiac Cycle Atrial Systole; Ventricular Diastole Atrial Diastole; Ventricular Systole Atrial & Ventricular Diastole

Heart sounds Lubb- Dubb Each part of the sound is actually valves in the heart closing Lubb: A-V Valves between the atria and ventricles closing Dubb Pulmonary and Aortic valves between the ventricles and arteries closing

Cardiac Conduction System Coordinates the events of the cardiac cycle Composed of specialized cardiac muscle tissue Sends impulses through the heart

Cardiac Conduction System SA Node Atrial Syncytium AV Node AV Bundle Pukinje Fibers Path of impulses through heart

Cardiac Conduction System Sinoatrial (SA) Node Initiates impulses without stimulation from nerves Impulses spread to surrounding muscle and cause contraction Impulse activity is rhythmic A.K.A. pacemaker

Cardiac Conduction System Atrial Syncytium Specialized cells in the wall of the heart Cause atrial chambers to contract when impulse travels through

Cardiac Conduction System Atrioventricular (AV) Node Serves as a bridge between atria and ventricles Impulses slow as they pass through

Cardiac Conduction System Atrioventricular (AV) Bundle A.k.a. Bundle of His Branches out into ventricle walls

Cardiac Conduction System Purkinje Fibers Connected to AV bundle branches Help ventricle walls contract in twisting motion Push blood into arteries

Electrocardiogram “ECG” Records electrical changes in the myocardium during cardiac cycle There are several “waves” during one cardiac cycle P wave QRS Complex T wave

Electrocardiogram P wave Represents atria contracting QRS Complex Represents ventricles contracting Actually 3 waves close together T wave Represents chambers beginning to relax

Regulation of the Cardiac Cycle Heart rate changes to fit the body’s needs Ex. Speeds up when we exercise Changes in the SA node cause changes in heart rate b/c it’s the pacemaker

Regulation of the Cardiac Cycle Signals to change heart rate come from the Medulla Oblongata Contains the “Cardiac Center” Connected by sympathetic and parasympathetic nerve fibers

Regulation of the Cardiac Cycle Parasympathetic fibers Release acetylcholine Tells heart to slow down Sympathetic fibers Release Norepinephrine Tells heart to speed up

Regulation of the Cardiac Cycle Other factors influence heart rate: Body Temperature Certain ions Increased temp = increased rate Decreased temp = decreased rate

Regulation of the Cardiac Cycle Ions Calcium Potassium Hyperkalemia Too much potassium Decreases rate and force of contractions

Regulation of the Cardiac Cycle Hypercalcemia Too much calcium Contractions last too long Hypocalcemia Not enough calcium Contraction too short and weak

Blood Vessels Arteries and Arterioles Capillaries Venules and Veins

Arteries and Arterioles Vessels that carry blood away from the heart Subdivide into progressively thinner tubes Arterioles Thinner vessels Branch off from arteries

Arteries and Arterioles Artery Wall Consists of 3 layers Innervated by the sympathetic nervous system Vasoconstricion vasodilation

Arteries and Arterioles Vasomotor Fibers Sympathetic nerve fibers Innervate artery walls Vasoconstriction Impulses from fibers causes artery walls to contract Vasodilation LACK of impulses causes walls to relax

Capillaries Smallest blood vessels Walls composed of only 1 layer Semipermeable Openings are thin slits where cells overlap

Capillaries Capillaries can form 2 different ways Direct, single path from arterioles to venules Creation of highly branched networks Networks have precapillary sphincters

Capillaries Precapillary sphincters Contracts and relaxes based on needs of surrounding cells This way blood can flow through different pathways to meet all the needs

Capillaries Exchanges in capillaries Occurs between blood inside and tissue fluid outside Includes gases, nutrients and metabolic by-products Exchange methods Diffusion Filtration osmosis

Venules and Veins Venules Microscopic vessels Continue from capillaries Veins Larger vessels that return blood to heart Formed from merged venules

Venules and Veins Walls of veins Similar to artery walls Have flaplike valves Aid in returning blood to the heart

Paths of Circulation 2 paths Pulmonary Circuit Systemic Circuit

Paths of Circulation Pulmonary Circuit Takes blood through the lungs 4 steps 1. Blood enters right atrium 2. blood enters right ventricle 3. blood is sent to the lungs 4. blood is sent to the left atrium

Paths of Circulation Systemic Circuit Takes blood through the body 4 steps 1. blood enters left atrium 2. blood enters left ventricle 3. blood is sent to the body 4. blood is sent to the right atrium

Blood Pressure Arterial blood pressure Factors that influence arterial blood pressure Heart action Blood volume Peripheral resistance Blood viscosity

Blood Pressure Commonly refers to the force that blood exerts against the inner walls of the arteries

Arterial Blood Pressure Pressure rises and falls as the ventricles contract and relax Measured in two parts Systolic pressure Diastolic pressure

Arterial Blood Pressure Systolic Pressure Maximum pressure during ventricular contraction Diastolic Pressure Minimum pressure during ventricular relaxation

Factors that influence- Heart Action Stroke volume The volume of blood pushed out of the left ventricle with each contraction Cardiac Output Volume pushed out per minute Calculation = stroke volume X heart rate Changes in cardiac output can cause changes in blood pressure

Factors that influence- Blood Volume Equals the total amount of blood in the vascular system Usually about 5 liters for adults Changes in blood volume can cause changes in pressure

Factors that influence- Peripheral Resistance Force caused by friction between blood and vessel walls Hinders blood flow Vessel contraction or dilation can change peripheral resistance Therefore, changes blood pressure

Factors that influence- Blood Viscosity The ease with which blood flows Greater viscosity = greater resistance to flowing Blood pressure increases with greater viscosity Vice versa