Biology 210 Chapter 12 Cardiovascular system

Functions of the cardiovascular system

1. Contractions of the heart generates blood pressure in the arteries 2. The heart and blood vessels keep oxygen rich blood separate from oxygen poor blood 3. One way valves in the heart and veins keep the blood flowing in one direction 4. The heart and blood vessels regulate blood flow according to the needs of the body 5. Exchange across capillary wall refreshes blood and tissue fluid

Cardiovascular Pathways

A. Pulmonary circuit •Powered by the right ventricle •Pulmonary arteries - carry O2-poor blood to the lungs •Pulmonary veins - carry O2-rich blood from lungs to the left atrium B. Systemic circuit •Powered by the left ventricle •Aorta - carries O2-rich blood to all body tissues •Vena cava - returns O2-poor blood to the right atrium. C. Coronary circuit Supplies blood to the heart muscle itself •First branches off the aorta •Arteries can become clogged and by-pass surgery may be necessary D. Renal circuit •Supplies blood to the kidneys E. Hepatic portal circuit •Supplies blood to the digestive organs especially the liver

Arteries

ALWAYS carry away from the heart and usually carry oxygen rich blood

Veins

ALWAYS return blood to the heart and usually carry oxygen poor blood

Blood Pressure

Blood flow in arteries •Due to the pumping action of the heart moves blood through the arteries Average blood pressure = 120/80 mm Hg Sphygmomanometer •aka blood pressure cuff Systolic pressure - Highest pressure in the artery during each heartbeat •Ventricles are contracting •About 110 to 120 mm Hg in a healthy adult Diastolic pressure - Lowest pressure in the artery during each heartbeat •Ventricles are relaxing •About 70 to 80 mm Hg in a healthy adult

blood flow

Blood flow in veins •Blood pressure is almost non-existent in veins Venus return is dependent upon several mechanisms: 1. Skeletal muscle contraction 2. One-way valves 3. Respiratory movements Blood flow in capillaries is slow •This is important because the slow progress allows time for the exchange of substances between the blood and surrounding tissues

two semilunar valves

Called SL Base of major arteries making a "dub" sound when closing

Myocardium

Consists of cardiac muscle tissue, which contracts to pump blood

septum

Divides the right and left chambers of the heart

Venus end

Entrance of CO2, water, and wastes

cardiac cycle

One complete heart beat where both atria contracts simultaneously followed by both ventricles contracting simultaneously •Cardiac cells have an intrinsic ability to contract independently, inside and outside the body •If individual cells are twitching independently, once they touch they will begin beating in unison •Once cells touch, the cell membranes connect at specialized junctions called intercalated disks •Although cells contract on their own, they still need outside control of rate

Two membranes surrounds the heart

Pericardium and myocardium

Pericardium

Thick membranous sac surrounding the heart ( secretes serous fluid)

Two artia:

Thin walled upper chambers that serve as reservoirs for blood

heart valves

Two atrioventricular and two semilunar valves

Systole

When ventricles contracts and pumps blood out of heart

Diastole

When ventricles relax and receive blood from atria

The heartbeat

cardiac cycle, systole, diastole

arteriole end

exit of O2, water, and nutrients

Aorta

largest artery

vena cava

largest vein in the body

Two atrioventricular valves

mitral and tricuspid Called AV valves Between atria and ventricles, making a "lub" sound when closing

P wave

occurs just prior to atrial contraction Signals from SA node spread across the atria and cause them to contract

T wave

occurs when the ventricles are recovering Return of the ventricles to the electrical state before contraction

heart

pumps blood throughout the body

heart chambers

right atrium, right ventricle, left atrium, left ventricle

Arterioles

smallest arteries

Venules

smallest veins

Two ventricles

thick-walled lower chambers powering the pulmonary and systemic circuits

blood vessels

tubelike structures that carry blood throughout the body

Electrocardiogram (ECG)

•Also known as the ECG or EKG •A recording of the electrical changes that occur in the myocardium during a cardiac cycle •Abnormal patterns can indicate heart problems •The P wave occurs just prior to atrial contraction •The QRS complex occurs just prior to ventricular contraction •The T wave occurs when the ventricles are recovering

pulse

•Alternating expansion and recoil of an arterial wall •ALWAYS taken in systemic artery

capillary exchange

•Arterial end - blood pressure is higher than osmotic pressure •Exit of water, O2, glucose, amino acids, and fatty acids •Venous end - osmotic pressure is higher than blood pressure •Entrance of CO2, waste molecules, and water

Capillaries

Smallest blood vessels connecting arterioles to venules

Passage of blood through the heart

Superior and inferior Vena Cava - Right Atrium - Tricuspid Valve - Right Ventricle - Pulmonary Semilunar Valve- Pulmonary Trunk and Arteries to lungs- Pulmonary Veins leaving the lungs - Left Atrium - Bicuspid Valve - Left Ventricle - Aortic Semilunar Valve - Aorta - To the body

Blood Vessels and Circulation

•Blood passes through the following loop of vessels moving away from the heart: •Arteries •Arterioles •Capillaries •Venules •Veins •Blood returns to the heart from venules and veins •Common features •Lumen: the hollow interior through which blood flows •Endothelium: the inner lining consisting of simple squamous epithelium •Unique features •Each type of blood vessel has traits that reflect its particular function •Arteries are thick, muscular vessels that carry blood away from the heart to body tissues •Layers •Inner—endothelium •Middle •Elastic fibers—allow the artery to stretch •Smooth muscle—allows the artery to contract •Outer—connective tissue •Anchors artery •Vasoconstriction •Smooth muscle of the middle layer contracts and the diameter of the lumen narrows, reducing blood flow •Vasodilation •Smooth muscle of the middle layer relaxes and the diameter of the lumen increases, increasing blood flow •Aneurysm •Occurs when the wall of an artery is weakened and swells outward •The primary risk is that it will burst, causing blood loss •If it does not burst, then it can form life-threatening clots •Can be repaired surgically in some cases •Arterioles •Smallest arteries •The prime controllers of blood pressure—pressure of blood against vessel walls •Serve as gatekeepers to the capillary networks, keeping them open or closed •Respond to hormones, the nervous system and local conditions •Capillaries are microscopic blood vessels connecting arterioles and venules •Sites of exchange of materials between the blood and the body cells •Have walls that are one cell thick •Provide enormous surface area for exchange •Exchange occurs through endothelial cells (across the plasma membranes) or through slits between these cells •Blood flows very slowly, allowing more time for exchange of materials

Ventricular Fibrillation or VFib

•Chaotic quivering of the ventricles that drastically reduces cardiac output •Must be corrected quickly with a defibrillator

internal conduction system

•Sinoatrial (SA) node •Natural pacemaker •Located in the right atrium •Causes atria to contract •Generates an electrical signal that sets the tempo of the heartbeat •Atrioventricular (AV) node •Located between the two atria •Receives the signal from the SA node •Transmits the signal by way of the atrioventricular bundle, located along the wall between the two ventricles, to Purkinje fibers that penetrate the walls of the ventricles, causing the ventricles to contract •Problems with the internal conduction system can result in ventricular fibrillation, irregular contraction of the ventricles •Electric shock may induce the SA node to function normally •Implantable defibrillators can be used in the long term

QRS complex

•The QRS complex occurs just prior to ventricular contraction Spread of signals through ventricles and ventricular contraction