The Cardiovascular System Objectives The Structure and Function

The Cardiovascular System

Objectives Ø The Structure and Function of the Cardiovascular System Ø How blood flows through the heart Ø The electrical activity within the heart Ø The role of Vascular system and it’s various components Ø Cardiovascular disease Ø Exercise response of the CV system

Functions

Functions of the CV system Ø Delivery and transport - Oxygen , nutrients and hormones from endocrine glands to tissues Ø Removal – Carbon dioxide and waste products from tissues Ø Maintenance – Temperature, and fluid levels Ø Prevention – fights infections and foreign antigens

Parts of the Cardiovascular system

The Cardiovascular system Components Ø Pump – The heart, a double pump. Pumps oxygenated blood to tissues and deoxygenated blood to the lungs. Ø Channels – the blood vessels where the blood travels through. Arteries, arterioles, capillaries, venules, veins Ø Fluid Medium – blood carries nutrients to and from the tissues.

Blood Ø Plasma – 55% l l l Ø 90% water 7% plasma proteins 3% acids and salts Formed elements 45% l l 99% RBC’s (Erythrocytes) 1% WBC’s (Leukocytes)

Anatomy of the Heart

The Heart Specialized muscle tissue called myocardium Ø Suspended in the chest by the aorta, vena cava, and pulmonary arteries and veins Ø Made of four chambers Ø

Heart Ø The heart is contained in a sac like structure (pericardium)

Heart Layers Pericardium - Shell Ø Epicardium – Outer layer Ø Myocardium – Heart muscle Ø Endocardium – Inner layer Ø

Inside of the heart Ø See Homework assignment l Draw the Heart and all it’s components

Cont…

Valves Cont… These valves are important for allowing the blood to travel consistently in the correct path. Thus they make sure that blood does not travel backwards Ø They open and close according to the pressure differences that occur within the heart during the cardiac cycle. Ø The opening and closing of these valves result in the Lub-Dub sound of the heart beat! Ø

Lub Dub Initial sound (Lub) is caused by the closing of the Tricuspid and mitral (bicuspid) valves Ø As the ventricles contract pushing blood into the aorta and pulmonary arteries, the pressure in the ventricles is higher then the pressure in the atria, this causes the valves to close Ø The second sound (dub) is caused by the increased pressure in the aorta and pulmonary arteries (which are filled with blood) and cause the aortic and pulmonary semilunar valves to close. The ventricles are almost empty at this point and so have a reduced pressure when compared to the aorta and pulmonary arteries which are filled with blood at this point. Ø

Cardiac Cycle Ø One cardiac cycle is one complete heart beat. (0. 8 sec. ) Ø On average the heart beats about 70 -72 times/min. Ø There is two parts to the cardiac cycle: -Systole: the active phase of the cycle when blood is ejected from the heart - Diastole – Passive phase in which heart relaxes and fills with blood

Steps to the Cardiac Cycle Ø Atrial Systole l Ø Ventricular Systole l l l Ø Ventricles contract Pressure increases and closes the tricuspid valve and mitral vlave Semi lunar valves open and blood spurts into aorta and pulmonary artery Ventricular Diastole l Ø Atria contract and blood is pushed into the ventricles Semi lunar valves close and ventricles relax and fill Atrial Diastole l Blood flows into the atria due to differences in pressure

Cardiac Cycle and Blood Pressure Ø Blood pressure is described using two numbers (systolic over diastolic) Ø Systolic- pressure in the arteries during systole Ø Diastolic – pressure in the arteries during Diastole Ø Blood pressure is measured in mm. Hg Ø Normal blood pressure is approximately 120/80 mm. Hg

Factors affecting Blood pressure Amount of blood (e. g. loss of blood volume due to injury could decrease pressure) Ø A decrease in blood pressure may not allow blood to flow properly since blood flow occurs because of differences in pressure. Ø Heart Rate the faster the heart rate the higher the pressure Ø Size of arteries (dilated vs. constricted) Ø Viscosity of blood (blood thinners, dehydration) Ø

How the Chambers know when to contract Ø Cardiac muscle cells allow electrical signals to pass through from cell to cell Ø This allows the heart to contract as a single unit. The contracting of the heart leads to the pumping of the blood Ø When all of the cardiac muscle cells contract at the same time = syncytium Ø All or None!

Excitation of the Heart Cardiac muscle cells are excitable like other muscle cells. However, the constant signal to contract comes from within. The heart can be stimulated by the autonomic nervous system (increase and decrease heart rate during exercise, stress etc) Ø The SA node sets the pace of the heart to keep it contracting regularly Ø The electrical signal from the SA node then spreads through the atria and then ventricles to contract. Ø

Excitation of the Heart

Excitation of the heart

When Things go wrong with the heart Ø Heart Attack l l Cholesterol Hypertension Ø Arrhythmia Ø Valve disorders

WHAT IS A HEART ATTACK? Ø A myocardial infarction or heart attack is caused when the heart muscle tissue does not get enough oxygen in order to maintain muscle contraction (i. e. beating). Ø This is most often caused by a blood clot which forms when blood flow through one or more of the coronary arteries is restricted. Ø Build up of Cholesterol is often the cause

HEART ATTACK

HEART ATTACK VS. CARDIAC ARREST Heart Attack is simply Ø Cardiac Arrest is when lack of blood f low to the heart stops its the myocardial tissue regular beating pattern and begins to fibrilate. Ø The Heart is still beating but not for long. Ø Shake like a bowl full of jelly. Each contraction is Ø Symptoms of a heart no longer strong attack begin enough to pump blood through the system Ø Heart requires defibrillation! Ø

Treatment 1 - Medication Ø Angiotensin converting enzyme (ACE) inhibitors are heart medications that widen or dilate your blood vessels to improve the amount of blood your heart pumps and lower blood pressure. ACE inhibitors also increase blood flow, which helps to decrease the amount of work your heart has to do

Treatment 2 - Angioplasty

Treatment 3 - Bypass

Arrhythmia Ø Arrhythmia – Irregular heart beat Ø Arrhythmia may cause your heart to beat too slowly (bradycardia, less than 60 beats per minute) or too quickly (tachycardia, more than 100 beats per minute), or cause uncoordinated contractions (fibrillation).

Arrhythmia Stress, smoking, heavy alcohol use, heavy exercise, use of certain drugs (such as cocaine or amphetamines), and too much caffeine or nicotine can lead to arrhythmia in some people. Ø A heart attack or an underlying condition that damages the heart's electrical system also can cause an arrhythmia. These conditions include high blood pressure (hypertension), coronary artery disease, heart failure. Ø Some cases are simply genetic conditions in which the electrical components of the heart are faulty. Ø

Valve problems Ø Leaking valves can produce other sounds when the heart is examined. “Murmurs” can result from leaky valves or from other defects of the heart. Ø If the Murmur is severe then medications and or surgery is required

Hypertension Normally the kidney control the level of salt in our blood by excreting it in urine Ø If intake levels get too high the kidneys can not keep pace and reduce the sodium levels quickly enough. Thus sodium levels remain high in the blood. Ø The extra sodium ends up attracting more water into the bloodstream. This increases blood volume and thus pressure in the blood vessels. Ø

Homework Question sheet