Chapter 10 Heart and Vessels

Blood flow to a capillary bed.

(a) Arterioles have circular, smooth muscle cells that act as precapillary sphincters to control blood flow to capillaries. (b) Some arterioles connect directly to small veins (venules), forming an arteriovenous shunt (c) Capillary walls are a single endothelial cell thick, allowing for the exchange of materials between blood and tissue fluid.

The action of heart valves on the left side of the heart

(a) Ventricular systole: The bicuspid valve is closed because the papillary muscle contracts to keep the cusps of the valve from opening toward the atria, and blood flowing toward the left atrium causes the cusps of the valve to overlap. The aortic semilunar valve is open because the cusps of the valve are pushed open by the blood flowing toward the aorta. (b) Ventricular diastole: The bicuspid valve is opened by the blood flowing into the left ventricle. The semilunar valve is closed because the cusps of the valve overlap as they are pushed by the blood in the aorta toward the dilated left ventricle. Similar action is taking place on the right side of the heart at the same time. The heart rests after the four phases have been completed to ensure enough time for all of the chambers to fill. The contraction of the atria in the next cycle pushes more blood into the already full ventricles, which expands the ventricular walls, making the ventricles more likely to contract.

Coronary circulation

(a) anterior view, (b) posterior view, (c) polymer cast of coronary arteries.

Spiral arrangement of cardiac muscle in the heart

(a) anterior view; (b) view from the apex of the heart, showing the spiral pattern.

Position of the heart in the thorax

(a) relationship of the heart to the sternum and ribs, (b) relationship of the heart to the pleural cavities of the lungs and the diaphragm, (c) frontal view with the lungs retracted and the pericardial sac cut

The three types of blood vessels in the body differ by location and direction of flow, as explained in the following list:

1. Arteries carry blood away from the heart to capillaries. 2. Capillaries allow for the exchange of materials between the blood and tissues. 3. Veins deliver blood from the capillaries back to the heart.

he three types of anastomoses are

1. Arteriovenous anastomoses. This type of route is often called a shunt. It merges an artery with a vein, skipping a capillary bed. You may ask why this would ever be done. After all, the point of circulation is to deliver materials to the tissues and take other wastes away, and that happens in the capillaries. This type of route is used in the fingers, palms, toes, and ears in conditions of extreme cold. The capillary beds are then temporarily bypassed so that heat is not lost. This is a protective mechanism. 2. Arterial anastomoses. This type of circulatory route merges two arteries to provide collateral routes to the same area. These routes can be found in the heart, to make sure all parts of the heart are adequately fed, and at joints, where movement may block one of the routes. 3. Venous anastomoses. This type of route is the most common of the anastomoses. It merges veins to drain an organ.

The effects of lifestyle can also make a difference in how this system ages. Here are some of the effects:

1. Physical conditioning can improve aerobic capacity in elderly individuals by increasing their cardiac output and ability to use oxygen effectively. It is possible for well-conditioned older people to exceed the aerobic capacity of people who are much younger and not as well conditioned. 2. Physical conditioning slows or reduces the vascular stiffening that may occur with aging. 3. Exercise over a lifetime can significantly increase the collateral circulation in the heart. This provides multiple avenues for blood to feed areas of myocardium that may have otherwise died if a coronary artery becomes blocked. 4. A diet low in sodium helps keep blood pressure under control. 5. Nonsmokers avoid the associated polycythemia that develops in smokers, whose blood cells carry carbon monoxide instead of oxygen. Not smoking helps keep the blood from becoming too thick and adding to the workload of the heart.

Heart anatomy

A hollow organ about the size of an adult fist and weighs approximately 300 grams (g), or 10 ounces (oz). It has a broad, superior base attached to the great vessels and a pointed apex (end) immediately superior to the diaphragm. The heart is located between the chest's pleural cavities in the mediastinum, deep to the sternum. Normally tilted, approximately two-thirds of the heart rests left of the midsagittal plane. Depending on body size and type, the heart may be positioned more upright (tall bodies) or more tilted (barrel-chested bodies).

Holter monitor

A machine worn by the patient that continuously monitors the heart's rhythms during everyday activities.

Cardiac vessel disorders

Aneurysm-A weakness in arterial vessel walls that can balloon out and possibly rupture. Arteriosclerosis- Calcification of the atheroma, or fatty deposit, within the blood vessel. Atherosclerosis- A condition that results in the buildup of fatty deposits within arterial walls, which causes the walls to roughen and project to the lumen (open space) within the vessel. Coronary artery disease- -(CAD) Obstruction of the coronary arteries that supply blood to the heart, usually caused by arteriosclerosis or atherosclerosis. Thrombophiebitis- Inflammation of a vein, caused by thrombosis. Varicose veins- Veins in which dysfunctional valves cause the backflow and pooling of blood, resulting in enlarged veins.

Myocardial disorders

Angina Pectoris-A heaviness or pain in the chest caused by a temporary or reversible myocardial ischemia. CHF- A condition in which one of the ventricles is not working as efficiently as the other. Myocardial infarction- The death of myocardial tissue due to ischemia

concepts of volume, pressure and flow

(a) As the volume increases, the pressure decreases within the syringe, so air rushes in to equalize the pressure inside and outside the syringe. (b) As the volume decreases, the pressure increases within the syringe, so air rushes out to equalize the pressure inside and outside the syringe.

Internal anatomy of the heart

(a) anterior view, (b) dissection of a cadaver heart.

Surface anatomy of the heart

(a) anterior view, (b) posterior view, (c) anterior view of a cadaver heart.

pharyngitis

(referred to as streptococcal pharyngitis or strep throat). Rheumatic fever can affect the joints, skin, central nervous system, and heart.

What is the cardiac conduction system?

A system of modified cardiac muscle cells that initiate and carry impulses which coordinate the cardiac cycle/

What occurs during ventricular diastole

AV valves open All four chambers fill with blood Ventricular pressure decreases

Heart Regulation

Adjusting either the heart rate or the stroke volume can change the cardiac output. Anything that changes the heart rate is called a chronotropic factor. Positive factors increase the heart rate, while negative factors decrease the rate.

What structure conducts impulses from the atria to the ventricles?

Atrioventricular node

Specialized cells within the heart that initiate and carry impulses and coordinate the cardiac cycle are part of the _____

Cardiac conduction system

Fossa ovalis

Closure of the hole in the fetal heart

What blood vessels empty blood to the right atrium?

Inferior vena cava and superior vena cava

Stimulation by the sinoatrial (SA) node leads to the

Simultaneous contraction of the atria

The fibrous strings that attach the atrioventricular valves to the papillary muscles are the

Tendinous cords

interatrial septum

The complete wall which separates the two atria from each other. The wall is complete because a hole has closed that existed in the fetal heart.

Heart Physiology

The function of the heart is to pump blood to meet the needs of the body. It is a sophisticated pump that can be regulated to meet the level of need, whether it is to pump faster or slower

Semilunar valves

The pulmonary valve and the aortic valve—are located between each ventricle and the vessel that carries the pumped blood away from the heart. The pulmonary valve lies between the right ventricle and the pulmonary trunk. The aortic valve lies between the left ventricle and the aorta. the purpose of all the heart's valves is to ensure the flow of blood in one direction by preventing backflow.

The relationship of an ECG and contraction of the myocardium

The purple areas in each drawing (a-g) indicate where tissues are depolarizing, and the green areas indicate where tissues are repolarizing. The graphs next to each drawing show the corresponding portion of the ECG pattern.

The Ventricles are______

The thicker-walled lower chambers of the heart

Input from the parasympathetic and the sympathetic nervous systems to the SA node influence heart rate. True or false

True

The systemic circuit carries oxygenated blood from the left ventricle to the body and back to the right atrium. True or false

True

What best describes the aortic valve?

Valve located at the base of the aorta

Defribrillator

a device used to deliver an electric shock to the heart when the heart has an arrhythmia. The electric shock interrupts the abnormal rhythm of the heart, allowing the normal heart rhythm to resume.

Electrocardiogram (ECG) (EKG)

a means of looking at cardiac rhythms. It is a graph showing the electrical activity in the heart, not the amount of contraction of the cardiac muscle. Figure 10.14 shows a normal ECG. The five waves on an ECG per cardiac cycle represent only three electrical events, outlined in the following list: The P wave shows the depolarization of the atria. The Q, R, and S waves together represent the ventricles depolarizing. The T wave represents the ventricles repolarizing.

arter/o, arteri/o

artery

atri/o

atrium

tendinous cords

attach the cusps of the AV valves to mounds of papillary muscle in the ventricles. These cords resemble parachute cords anchoring the valve (parachute) to the muscle.

steth/o

chest

ather/o

fatty substance

cardi/o

heart

Stethoscope

instrument for hearing heart sounds

pericardi/o

pericarium

sphygm/o

pulse

tachy

rapid

brady/

slow

tricuspid valve lies between?

the right atrium and the right ventricle

vascul/o

vessel

Myocardial Infarction

Atherosclerosis may cause CAD, which results in blocked blood flow in a coronary artery. This lack of blood flow—ischemia can lead to a myocardial infarction (MI)—the death of myocardial tissue fed by the affected artery commonly called a heart attack. Symptoms can vary for men and women, but most people experience the following: A crushing pain in the chest that may radiate to the neck and jaw and down the left arm Shortness of breath or difficult breathing Sweating Nausea A feeling of impending doom In addition to the symptoms mentioned here, women may experience lightheadedness, sleep disturbances, indigestion, anxiety, and unusual fatigue lasting for several days.

The upper, thin-walled chambers of the heart are called?

Atria

The atria fill with blood during______

Atrial relaxation and ventricular relaxation Atrial relaxation and ventricular contraction

In the systemic circulatory route, freshly oxygenated blood from the left ventricle is pumped into the ________, which branches off to different parts of the body

Aorta

The right and left coronary arteries arise from the

Aorta

List the types of vessels in the order a drop of blood would flow through the systemic circulatory route beginning with the aorta.

Artery, Arteriole, Capillary, Venule, Vein

Congenital heart defects

Atrial septal defect A hole in the septum that separates the right and left atria Congenital valve disorders Valve defects including stenosis, or narrow valves; atresia, in which a valve lacks a hole for blood to travel through; and regurgitation, in which the valve does not close tightly enough and allows blood to flow back through the valve. Patent ductus arteriosus The failure of the ductus arteriosus to close after birth. Tetralogy of fallot A combination of four congenital heart defects: pulmonary valve stenosis, VSD, overriding aorta, and right ventricular hypertrophy. Ventricular septal defect A hole in the septum that separates the right and left ventricles.

The valves that ensure one-way blood flow between the atria and the ventricles are the?

Atrioventricular valves

Baroreflex.

Baroreceptors in the aortic arch and carotid arteries constantly send signals. If the pressure is too high, messages from these receptors cause the medulla oblongata's cardiac inhibitory center to increase vagal stimulation of the heart, thereby decreasing the heart rate and blood pressure.

When the arterioles of a patient dilate, resistance and blood pressure______

Decrease

If the cardiac output decreases, then blood pressure________

Decreases

Resistance _____ the flow of blood

Decreases

Prehypertension

Diagnosed when the resting systolic pressure is 120 to 139 mmHg and/or diastolic pressure is 80 to 89 mmHg.

Neural Control

The brain also regulates blood pressure and flow. The vasomotor center in the medulla oblongata uses sympathetic fibers to constrict most vessels except those going to cardiac and skeletal muscles.

Coronary Route

The heart makes up only 0.5% of the body's weight, yet receives 5% of the circulating blood. This rich blood supply is another reason the heart can stay aerobic. The heart's myocardium is not fed by the blood passing through the chambers. It has its own circulation route composed of coronary arteries and veins

Chambers and Valves

The human heart is divided into four chambers. The two superior chambers—the right and left atria receive blood for the heart, while the Two inferior chambers—the right and left ventricles—pump blood out of the heart. Atria's small, hollow, earlike flaps called auricles, which slightly increase the atria's volume. Sulci are depressions on the surface of the heart and mark the division of the chambers externally. The coronary sulcus marks the separation of the atria from the ventricles. The anterior interventricular sulcus and posterior interventricular sulcus mark the separation of the right and left ventricles.

Phases of the Cardiac Cycle

The right and left atria go through systole and diastole together at the same time and that the right and left ventricles also work together with each other. Similarly, the AV valves function together, as do the semilunar valves. The four phases of a cardiac cycle happen in the following order: 1. Atrial systole. After the SA node fires, the atria depolarize and contract together, creating decreased volume and higher pressure in the atria than in the ventricles. The increased pressure pushes blood through the AV valves (tricuspid and bicuspid) into the ventricles. The pressure of the blood due to the atria's contracting is what forces the AV valves to open. 2. Atrial diastole. The atria then repolarize and relax. The elastic fibers in the walls of the atria return the atria to shape, increasing the volume and decreasing the pressure in the atria. The blood pressure in the superior and inferior venae cavae (on the right side of the heart) and the pulmonary veins (on the left side of the heart) is then greater than the pressure inside the atria, so blood rushes in from these vessels to fill the right and left atria. 3. Ventricular systole. Once the conduction system has carried the electrical impulses from the AV node to the Purkinje fibers, the ventricles depolarize and contract together. Papillary muscles also contract, pulling on the tendinous cords (chordae tendineae) to ensure that the AV valves stay closed and do not swing open toward the atria. This prevents the backflow of blood to the atria. Contraction of the ventricles decreases the volume and increases the pressure inside the ventricles. As a result, blood is pushed through the pulmonary and aortic valves into the pulmonary trunk and aorta, respectively. 4. Ventricular diastole. The ventricles then repolarize and relax. The elastic fibers in the ventricle walls return the ventricles to shape, increasing the volume and decreasing the pressure in the ventricles. The pressure inside the now full atria is greater than that inside the relaxed ventricles, so blood moves through the AV valves from the atria to the ventricles. The atria are not contracting in this phase. Blood is passively moving from the atria to the ventricles due to a difference in pressure. The pressure is also greater in the pulmonary trunk and aorta than inside the ventricles, but blood is caught in the cup-shaped semilunar pulmonary and aortic valves as it tries to return from these vessels to the ventricles. Once filled with blood, these valves are tightly closed to prevent backflow to the ventricles from the pulmonary trunk and aorta. Blood traveling passively from the atria to the ventricles in this phase reduces the pressure in the atria, so blood also moves passively from the venae cavae and pulmonary veins to the atria. All four chambers fill with blood during ventricular diastole.

Veins

The volume of the vessels continually decreases as blood moves from larger to smaller arteries to the capillaries. The opposite is true as blood continues on its path to the heart through the veins. Small veins called venules lead to medium and then large veins before returning blood to the heart. As the diameter of the veins increases, so does their volume. The total volume of all the veins is greater than that of the arteries. Increased volume means blood pressure is less in veins than it is in arteries. The decreased pressure means the walls of the veins do not need to be as thick and sturdy as those of the arteries. Arterial walls will hold an artery open even if empty. The thinner walls of veins collapse when a vein is empty.

Conducting Arteries

These are the largest of the arteries. Examples of conducting arteries include the pulmonary arteries, the aorta, and the common carotid arteries. They carry blood away from the heart. Because of their proximity to the heart, they need to withstand the high pressure generated by ventricular systole. They have the most muscle and elastic fibers in their walls so that they can expand with each heartbeat and then return to shape.

Resistance Arteries

These are the smallest of the arteries. Examples are the small arterioles that deliver blood to the capillaries. Arterioles have little, if any, elastic fibers. Each arteriole can feed a bed of approximately 100 capillaries. Precapillary sphincters (circular muscles) in the arterioles open or close to regulate blood flow to the capillaries.

Venules

These are the smallest of the veins, and they receive blood from the capillaries. Unlike the case with larger veins, there is no smooth muscle in the tunica media of venules.

Distributing Arteries

These arteries are medium-size. They distribute blood from the conducting arteries to organs. Examples include the hepatic artery, which carries blood to the liver, and the renal arteries, which carry blood to the kidneys. They have some elastic fibers in their walls to hold their shape, but they do not need to expand as much as conducting arteries with every heartbeat.

Systemic Routes

These routes carry blood from the heart to tissues in the body (other than the heart) and back again. The simplest route goes like this: Heart → arteries → capillaries → veins → heart Example: Blood leaves the heart's right ventricle to travel through the pulmonary trunk to pulmonary arteries, to arterioles, to capillaries covering air sacs (alveoli) in the lungs. Oxygen is loaded to the blood within the capillaries, and carbon dioxide is unloaded. From these capillaries, blood travels through venules to pulmonary veins to the left atrium of the heart.

Large Veins

These veins have some smooth muscle in all three tunics. Examples of large veins are the venae cavae, pulmonary veins, internal jugular vein, and renal veins.

Heart Rate

This measurement is made by feeling a pulse in an artery. Each heartbeat creates a surge in pressure that can be felt in the arteries carrying blood away from the heart. Commonly, the radial artery is felt on the anterior surface of the wrist, but arteries in the neck and legs can also be used.

Stroke volume

This volume also plays a key role in determining cardiac output. Stroke volume is the amount of blood ejected by each ventricle with each heartbeat, but it is not the amount of blood each ventricle can hold. Ventricles cannot completely empty themselves with each contraction

Blood flow into capillary beds is regulated by

Precapillary sphincters

Skeletal muscle contraction helps to push blood through veins. Venous valves ensure that blood flows only in one direction. true or false

True

Heart rate and rhythm disorders

Disease: Arrhythmia-An abnormal heart rhythm. Atrial fibrillation- A condition in which faulty electrical signals cause the atria to beat very rapidly and in an irregular pattern. Bradycardia-A persistent resting adult heart rate that is less than 60 beats/min. Tachycardia-A persistent resting adult heart rate that is greater than 100 beats/min.

Valve disorders

Disease: Murmur-An abnormal heart sound prolapse: A valve in which the leaflet "billows" or bends in a way that prevents it from closing properly. stenosis: A narrowing of the valve, causing incomplete closure.

Interatrial septum and interventricular septum Myocardial walls

Divide the heart into right and left sides. Each side of the heart serves as a separate pump for blood. The right side of the heart pumps blood to the lungs (short distance), while the left side of the heart pumps blood to the rest of the body (long distance). Because the left side's workload is greater than the right side's, the left ventricle has a thicker myocardium. Always look at the outer walls of the ventricles on a dissected heart or illustration to determine right from left.

The difference between systolic and diastolic blood pressure is known as______

Pulse pressure

The structure that distributes electrical signals throughout the myocardium of the ventricular walls are?

Purkinje fibers

TESTS USED TO ASSESS THE PHYSIOLOGY OF THE HEART AND VISUALIZE ITS ANATOMY

Echocaridograpy, Electrocardiography ECG EKG, Heart CT scan, Nuclear heart scan,

Blood pressure disorders

Hypertension- The condition that results when resting pressures are greater than 140/90 mmHg. Hypotension- Chronic low pressure, below 90/60 mmHg. Prehypertension- The condition diagnosed when the resting systolic pressure is 120 to 139 mmHg and/or diastolic pressure is 80 to 89 mmHg. Shock-A life-threatening condition characterized by the body's organ systems, especially the brain, not getting enough blood flow to sustain normal function. There are different categories of shock: cardiogenic shock, hypovolemic shock, septic shock, and neurogenic shock.

Medullary ischemic reflex

If blood flow to the brain decreases, the cardiac accelerator center and the vasomotor center send sympathetic signals to increase heart rate and increase vasoconstriction. This increases pressure and blood flow to the brain. The medullary ischemic reflex is effective for even simple actions, like standing suddenly after being in a supine position, such as lying on your back. In this case, change of position reduces blood flow to the brain temporarily.

The major systemic arteries.

Many vessels are shown on only one side for clarity but occur on both sides (a. = artery).

The major systemic veins

Many vessels are shown on only one side for clarity but occur on both sides (v. = vein, vv. = veins).

The layer of the heart that consists of cardiac muscle tissue is called the

Myocardium

Superior view of the aortic valve with a section of the aorta removed.

See two openings within the aortic valve. The pressure of blood filling the cusps of the valve as it tries to return to the heart during ventricular diastole forces oxygen-rich blood into the right and left coronary arteries. These two arteries then branch to form the coronary arteries that lead to capillary beds in the heart's tissues. Twenty percent of the blood from the capillaries is directly returned to the right atrium of the heart from small veins. The rest of the blood in coronary circulation is collected by the great cardiac vein and the middle cardiac vein and then emptied into the coronary sinus before entering the right atrium.

Interventricular septum

Separates the two ventricles

The structure that separates and prevents mixing blood between the ventricles is the interventricular

Septum

The skeletal muscle pump

Skeletal muscle action massages blood through the veins in the direction of the heart.

Prolapsed Valve

Characterized by a valve leaflet that "billows" or bends in a way that prevents it from closing properly. This can be caused by degeneration of the valve or the chordae tendineae. While mitral valve prolapse is the most common type of prolapse, this condition can affect any valve found within the heart. Inability of the valve to close can cause regurgitation (backflow) of blood in the heart. If the regurgitation is severe enough, ventricular enlargement, arrhythmias, endocarditis, or stroke may occur. A prolapsed valve is diagnosed using echocardiography. Treatment usually involves monitoring the disorder. Some individuals may be medicated to treat the arrhythmias, and others may eventually need the faulty valve replaced.

portal route

contains two capillary beds before blood is returned to the heart. In this type of circulation, blood travels in the following route: Heart → arteries → capillaries → intervening vessels → capillaries → veins → heart Because there are two capillary beds, this type of route allows materials to be exchanged twice between the blood and tissues before returning to the heart. Examples of portal routes can be found between the hypothalamus and pituitary gland, in the kidney, and between the intestines and the liver.

Venules unite to form?

Veins

Varicose Veins

Veins in which the valves that prevent the backflow of blood are not working properly. The dysfunctional valves allow the blood to pool, causing the vein to enlarge. Varicose veins are usually secondary to some other condition, such as thrombophlebitis or pregnancy, and are commonly found in the legs. While visibly unattractive, most varicose veins do not cause significant health problems. If the varicose veins cause pain, treatment can include raising the legs while sitting or sleeping, avoiding standing for long periods, and wearing support hose. As with thrombophlebitis, if the varicose veins are severe, they can be surgically removed. (a) normal vein compared to a varicose vein, (b) varicose veins in the legs.

The smallest of all veins are

Venules

Tetralogy of Fallot

a combination of four heart defects: pulmonary valve stenosis, VSD, overriding aorta, and right ventricular hypertrophy. An overriding aorta is a defect involving the position of the aorta. In this case, the aorta is positioned between the right and left ventricles, allowing the deoxygenated blood from the right ventricle to flow to the aorta instead of the pulmonary artery. Right ventricular hypertrophy is the enlargement of the ventricle, which results from the ventricle working harder than normal. four abnormalities that result in insufficiently oxygenated blood pumped to the body.

Angina Pectoris

a heaviness or pain in the chest caused by a temporary or reversible myocardial ischemia. The hypoxemia from the reduced blood flow causes the heart to use anaerobic respiration to produce the energy it needs. The buildup of lactic acid produces the associated pain.

Atrial septal defect (ASD

a hole in the septum that separates the right and left atria. This allows oxygenated blood from the left atrium to mix with deoxygenated blood from the right atrium

Ventricular septal defect (VSD)

a hole in the septum that separates the right and left ventricles. The oxygenated blood in the left ventricle that should normally flow to the aorta and the rest of the body mixes with the deoxygenated blood in the right ventricle.

Tachycardia

a persistent resting adult heart rate greater than 100 beats/min. Stress, anxiety, drugs, heart disease, and fever can all cause tachycardia.

Bradycardia

a persistent resting adult heart rate that is less than 60 beats/min. Causes for this condition can be sleep, endurance training for athletes, and hypothermia.

Cardiac muscle is

autorhythmic, meaning it does not need to be stimulated by the brain to contract. Modified cardiac muscle cells initiate and carry the electrical impulses as part of a conduction system that stimulates heart contractions. The nervous system may further modify the amount and frequency of the contractions, but nerve impulses are not needed to initiate a heart contraction.

Cardiac Muscle Tissue

cardiac muscle is striated (striped) and branching and has one nucleus per cell. The specialized junctions between cells—intercalated disks enable the fast transmission of electrical impulses from one cell to another. With this feature, contractions of both atria are stimulated simultaneously, so they contract together as one. The same holds true for the ventricles. Unlike skeletal muscle cells that can perform tetany if nerve impulses are frequent enough, all cardiac muscle cells have an absolute refractory period. The absolute refractory period prevents the cardiac muscle from going into tetany and gives the heart chambers a chance to fill between contractions.

The outer layer of the heart wall together with the parietal pericardium, protect the heart by reducing friction. This outer layer is called the

epicardium

Valve defects

include stenosis (narrowing of the valves), atresia (a valve that lacks a hole for blood to travel through), and regurgitation (a valve does not close tightly enough and allows blood to flow back through). Any valve defect will alter the flow of blood through the heart.

An increase in the concentration of blood cells or plasma proteins will cause viscosity to ______ and thus _______blood pressure

increase; increase

The simultaneous contraction of the atria is caused by electrical impulses from the SA Node. true or false

true

ven/i

vein

ven/o

vein

ventricul/o

ventricle

vas/o

vessel

rhythm/o

rhythm

The atria are separated from the ventricles by?

the atrioventricular (AV) valve

The vasomotor center and the cardiac centers of the medulla oblongata are influenced by three reflexes

the baroreflex, chemoreflex, and medullary ischemic reflex

bicuspid (mitral) valve (MY-tral) lies between?

the left atrium and the left ventricle.

Neurogenic shock

is a condition of the nervous system in which stimulus to the sympathetic nervous system is lost, resulting in the inability to keep the appropriate amount of muscle tone in the tunica media of the blood vessels. This results in the pooling of blood, as opposed to the adequate pumping of blood to the body's systems.

epicardium (visceral pericardium)

is the most superficial and a more delicate layer composed of simple squamous epithelial tissue over loose areolar connective tissue. It is in direct contact with the surface of the heart. Normally, the two layers of the pericardium are close together with pericardial fluid between the layers to reduce the friction caused by the heart's pumping action. Disease or inflammation may cause the amount of pericardial fluid to increase, restricting room for the heart to expand.

The heart in its pericardium, the major arteries such as the aorta, and the esophagus are all located within a space between the lungs called the

mediastinum

Hypovolemic shock

occurs when the body undergoes severe fluid and blood loss, which results in not having enough blood to pump to meet the body's needs. Often, hypovolemic shock can be caused by internal bleeding or bleeding from cuts or injuries. It can also be caused by fluid loss through extreme perspiration, diarrhea, burns, and vomiting.

Chronotropic Factors of the Autonomic Nervous System

the nervous system does not initiate heart contractions, but it can modify their frequency. Two centers located in the medulla oblongata are the cardiac accelerator center and the cardiac inhibitory center: The cardiac accelerator center uses sympathetic neurons to stimulate the SA and AV nodes to speed up the heart rate. The cardiac inhibitory center uses parasympathetic neurons of the vagus nerve to keep the SA node at 70 to 80 beats/min (vagal tone). If the vagus nerve is severed, the SA node will typically set the pace at 100 beats/min.

Anastomoses

the second type of alternative routes, involve vessels merging together. The three types of anastomoses are explained in the following list:

TESTS USED TO ASSESS CARDIAC FUNCTION DURING ACTIVITY

Holter Monitor, stress test,

Cardiac Rhythm

How often cardiac cycles occur is determined by the pacemaker the SA node. A normal pace (sinus rhythm) is usually 70 to 80 beats per minute, although common rates may be in the range of 60 to 100 beats per minute. The SA node would set a faster pace, but the pace is normally kept in check by the autonomic nervous system through the vagus nerve. This is called vagal tone. An ectopic focus occurs when any part of the conduction system other than the SA node is setting the pace. Any cardiac muscle cell is capable of becoming a pacemaker. A nodal rhythm occurs if the AV node is the ectopic focus. Hypoxemia, caffeine, nicotine, electrolyte imbalance, and some drugs may cause an ectopic focus.

Atherosclerosis

Results in the buildup of fatty deposits within arterial walls, which causes the walls to roughen and project to the lumen (open space) within the vessel. Often begins as a result of hypertension or viral infection that weakens the arterial wall. Monocytes stick to the tunica interna at the weakened area and then proceed to the tunica media, where they become macrophages. As macrophages, they consume fats and cholesterol from the blood and develop a foamy appearance. The buildup of the fatty deposits (plaque) thickens the arterial wall and makes the lining of the artery rough. This obstructs blood flow and provides a surface to which platelets stick. Platelets complicate the condition by secreting growth factors to stimulate mitosis in the vessel walls, further reducing the size of the lumen. The narrowed, rough interior of the artery is a prime location for developing blood clots to form. If the atheroma (fatty deposit) becomes calcified, the condition is called arteriosclerosis. When atherosclerosis or arteriosclerosis obstructs the coronary arteries that supply blood to the heart, coronary artery disease, or CAD, results. If not treated, CAD can go on to cause further damage to the heart by potentially causing myocardial infarction. A variety of tests are used to diagnose CAD, such as coronary angiography, echocardiography, electrocardiography, stress test, and nuclear stress test. Treatment for CAD may include medications that lower blood pressure. Surgery may also be required to restore blood flow to the heart. Physicians may also suggest lifestyle changes that include eating a heart-healthy diet low in sodium, not smoking, reducing stress, and limiting alcohol intake. (a) a healthy artery, (b) an artery with atherosclerosis, showing plaque buildup and reduced lumen.

Hypertension

Results when resting pressures are greater than 140/90 mmHg. Usually, there are no symptoms associated with hypertension unless the blood pressure is dangerously high. Because symptoms are absent, the disease can cause organ damage such as heart or kidney disease before individuals even know they have it. Hypertension is treated with medications that lower blood pressure and with lifestyle modifications. Physicians may suggest that patients alter their diet to limit salt intake, lose weight, reduce stress, stop smoking, and exercise. It is important to control hypertension because if left untreated, it can lead to kidney disease, heart attack, stroke, poor vision, and poor blood supply to extremities. Hypertension can also weaken small arteries and can cause aneurysms, which are weaknesses in arterial vessel walls that can balloon out and even rupture

Respiratory movements

aid in venous flow from the abdominal to the thoracic cavity

Murmur

an abnormal heart sound. It may be a functional murmur (not a problem) or a pathological murmur (possible leaky valve). The murmur often makes a ssh sound. If the heart sound is lubbssh dupp, lubbssh dupp, the AV valves may be suspected of leaking because the abnormal sound is occurring with the first sound in the cardiac cycle.

Three congenital heart defects:

an atrial septal defect, a patent ductus arteriosus, and a ventricular septal defect.

Local Control of blood pressure: Tissues can autoregulate their own blood supply in four different ways:

1) Opening of precapillary sphincters. If there is inadequate blood flow, wastes such as carbon dioxide, lactic acid, and hydrogen ions build up in the tissues. The presence of wastes stimulates vasodilation and the opening of precapillary sphincters, creating more blood flow. Increased blood flow to the capillaries brings more oxygen to the tissues (to remove the lactic acid) and removes the wastes. The waste removal ends the vasodilation and closes the precapillary sphincters. There are about a billion capillaries in the human body arranged in beds. Sphincters control the blood flow to these capillary beds, and three-fourths of the capillary beds are empty at any given time because the sphincters are closed to them. You do not have enough blood to fill all of the capillaries, nor do you have a heart strong enough to pump all the blood that would be necessary to fill all of the capillaries at any one time. This is a lot like a sprinkler system. Local control related to the body's capillaries is based solely on need. When waste builds up in an area, precapillary sphincters open and blood flow increases to take the waste away immediately when it is needed, not on a schedule. When the wastes are gone, the precapillary sphincters close, so blood is diverted to other areas where it is needed. All the tissues are fed and wastes are taken away efficiently without any more strain on the pump (heart) than is absolutely necessary. 2) Inflammation. In response to an injury or the presence of a pathogen, damaged tissues or basophils release vasodilators in the local area to stimulate inflammation. This inflammatory response dilates vessels and makes them more permeable, thereby increasing blood flow to the area. The increased blood flow delivers more white blood cells to the area to fight pathogens, which accounts for the redness, heat, and swelling associated with inflammation. 3) Reactive hyperemia. If circulation to an area is cut off for a time and then restored, vessels overdilate, flushing an area with blood. An example of this can be seen when you cross your legs at the knee. When you remove the top knee, you may notice a red area on the knee where the leg rested. Another example: If you are out in the cold so long that vessels have constricted in the skin to save heat for the core (the skin appears white) and then you come inside where it is warm, the vessels in the skin overdilate and the skin appears red. 4) Angiogenesis. Persistent buildup of metabolic waste causes new vessel growth (angiogenesis) to increase the blood supply to the area. Heart patients, depending on their condition, may be encouraged to exercise. The buildup of wastes in cardiac muscle tissue promotes the growth of new vessels to provide collateral (additional) circulation in the heart. Fast-growing cancer tumors can also stimulate angiogenesis to feed a tumor and remove its wastes. This is an important area of cancer research. If angiogenesis can be prevented in this case, the tumor can be starved and the tumor's growth may be slowed.

The pathway of blood flow through the heart

1)Blood enters the right atrium of the heart from the superior and inferior venae cavae. 2 Blood passes through the tricuspid valve to the right ventricle. 3 Blood is forced through the pulmonary valve to the pulmonary trunk. 4 Blood travels through the pulmonary trunk to the pulmonary arteries. 5 Blood travels to the lungs, where CO2 is unloaded and O2 is loaded. 6 Blood returns to the heart from the lungs through the four pulmonary veins to enter the left atrium. 7 Blood passes through the bicuspid (mitral) valve to the left ventricle. 8 Blood is forced through the aortic valve to the aorta. 9 Blood travels from the aorta to the rest of the body. 10 Blood returns to the heart through the superior and inferior venae cavae. Steps 4 to 6 illustrate the circulation of blood through the lungs. Steps 8 to 10 illustrate the circulation of blood through the body. Violet arrows indicate oxygen-poor blood, while orange arrows indicate oxygen-rich blood. the right side of the heart pumps blood to the lungs and back (pulmonary circuit). At the lungs, CO2 is unloaded from the blood and O2 is loaded into the blood. Once the blood is returned from the lungs, the left side of the heart pumps blood out to all parts of the body to be returned once again to the right side of the heart (systemic circuit). At the tissues of the body, O2 is unloaded and CO2 is loaded.

Cardiac Conduction System

1. A heartbeat (heart contraction) is started by the sinoatrial (SA) node, a patch of specialized cardiac muscle cells located in the wall of the right atrium near the opening for the superior vena cava. The SA node is the heart's pacemaker. 2. From the SA node, modified cardiac muscle cells carry electrical impulses across the myocardium of both atria, causing them to depolarize and contract together as one (shown by black arrows). 3. While step 2 is happening, other modified cardiac muscle cells carry electrical impulses from the SA node to the atrioventricular (AV) node, located on the right atrium's interatrial septum. It is from this node that the ventricles will be stimulated to contract. 4. The atrioventricular (AV) bundle (bundle of His) divides into branches that continue to carry the electrical impulses from the AV node down the interventricular septum toward the heart's apex. Collagen fibers of the heart's fibrous skeleton insulate the specialized cardiac muscle cells, so the electrical impulses go only to their proper destination. 5. Purkinje fibers (per-KIN-jee) fan out from the ends of the AV bundle to the walls of the ventricles, stimulating the cardiac muscle cells of the ventricular myocardium to depolarize and contract.

The endocrine system can also be used to maintain homeostasis by regulating blood pressure and flow by the use of the following four hormones:

1. ADH (also called vasopressin). ADH targets the kidney to cause water retention. By preventing water loss in urine, blood volume and therefore pressure are maintained. 2. Aldosterone. This mineralocorticoid targets the kidney to cause sodium to be retained in the blood. Water follows the sodium, so again, by preventing water loss in urine, blood volume and pressure are maintained. 3. Angiotensin II. Angiotensin II is a vasoconstrictor produced by the liver when blood pressure falls below homeostasis. Widespread vasoconstriction increases blood pressure. 4. Epinephrine. Epinephrine complements the sympathetic nervous system by causing vasoconstriction, which limits blood flow to most vessels except those vessels going to cardiac and skeletal muscle.

Five mechanisms aid in venous return

1. Pressure gradient. Even though there is less pressure in the veins than in the arteries, the pressure in veins due to the action of the heart does propel blood toward the heart. 2. Gravity. Blood moves through veins above the heart due to gravity, and it flows downhill. 3. Thoracic pump. The chest expands every time a breath is inhaled. This increases the volume and decreases the pressure within the chest. As air rushes in to equalize the pressure, blood in the veins of the abdominal cavity is sucked into the inferior vena cava of the thoracic cavity by the same principle. 4. Cardiac suction. You were introduced to this mechanism during the cardiac-cycle discussion. Atria return to shape during atrial diastole. This creates less pressure in the atria than in the superior and inferior venae cavae and the pulmonary veins, so blood is sucked into the atria from the veins. 5. Skeletal muscle pump. This mechanism is especially effective in the limbs. Skeletal muscle action massages blood through the veins, while the valves in the veins prevent backflow. Ventricular contractions force blood out of the heart under pressure. That same pressure causes blood to continue on its journey through the arteries, capillaries, and veins (to a lesser extent) as blood is returned to the heart.

Blood flows from the inferior vena cavae to the right atrium to the right ventricle. After the right ventricle, trace the flow of blood through the structures.

1. Pulmonary trunk 2. Lungs 3. Pulmonary veins 4. Left atrium 5. Left ventricle 6. Aorta

If the cardiovascular systems maintain homeostasis within a normal blood pressure range, there may be little to no effect of aging on the hearts. If hypertensive there may be dramatic changes. These changes include the following:

1. Vascular resistance increases with age in individuals with hypertension. This increases afterload, which then requires higher diastolic and mean arterial pressure to move the same amount of blood through the system. 2. Decreased resting stroke volume decreases cardiac output, which means the heart becomes less efficient. 3. The vessels thicken and become less elastic. This makes the vasculature more susceptible to developing atherosclerosis (discussed in the final section of this chapter).

The two types of thrombophlebitis are

1. deep venous thrombosis, which affects deep veins; and 2. superficial thrombophlebitis, which affects veins close to the skin's surface.

Effects of Exercise on Cardiac Output

A morning run with a resting heart rate and resting cardiac output. Once the run has started, proprioceptors in the joints, muscles, and tendons alert the cardiac accelerator center in the medulla oblongata of the increased activity level. The center sends messages along sympathetic neurons to increase their heart rates. Th muscles are doing increased aerobic respiration, which causes more metabolic wastes to build up in the tissues. Locally, vasodilation and the opening of precapillary sphincters in the muscles increase blood flow, so more of the accumulating wastes are carried away in the blood. This stimulates a chemoreflex to increase blood flow to the lungs. If you make a habit of regular exercise, the chronic buildup of wastes stimulates angiogenesis to improve the collateral circulation in their coronary arteries. As you continue to run, the muscles are massaging their veins, which increases the venous return to the heart. This added preload results in a greater stroke volume because the heart must pump out what it receives. So the heart rates and stroke volumes have increased during the run, and these increases, together, greatly increase their cardiac output. Their cardiac reserve may easily be four to five times larger than their resting cardiac output.

CT angiography

A noninvasive way to perform coronary angiography using computed tomography.

Stress test

A test that monitors the heart's electrical activity, blood pressure, and heart rate while the patient is exercising.

Electrocardiography (ECG or EKG)

A test that records the heart's electrical activity and shows certain problems, such as abnormal heartbeats or damage to the heart.

Echocardiography

A test that uses sound waves to create a picture of the heart.

Venography

A test used to view vessels in the body. Contrast dye is injected into the vein. The movement of the dye through the vein is monitored by X-ray.

Cardiac catheterization

A procedure in which contrast dye is injected through a catheter into the heart. The movement of the dye through the valves, heart chambers, and coronary arteries is monitored by X-ray.

Nuclear heart scan

A procedure that uses a radioactive dye to view the heart.

The structural differences of arteries and veins:

Along with direction of blood flow and location, the histology of the walls of arteries, veins, and capillaries also differs. (a) artery, (b) vein, (c) micrograph showing cross sections of a small artery (arteriole) at the bottom and a small vein (venule) at the top.

Arrhythmia

An abnormal heart rhythm. One cause is heart block, in which one part of the heart's conduction system fails to send its signals. If the ventricles do not receive the signals from the SA node via the AV node and AV bundle, they will beat at their own pace of 20 to 40 beats per minute. Their contractions, however slow, will not be coordinated with the contractions of the atria, and the efficiency of the heart will be compromised.

Ultrasound

An imaging technique, using sound waves, to visualize internal structures.

A fetal heart is different than a normal heart

An opening called the foramen ovale is located in the interatrial septum. This opening allows blood in fetal circulation to bypass the right ventricle and the lungs. There is also a blood vessel called the ductus arteriosus that connects the aorta and the pulmonary artery. A fetus does not need to send blood to its own lungs because it receives oxygenated blood from its mother. Once the baby is born, the foramen ovale closes and becomes the fossa ovalis. The ductus arteriosus also closes, completely separating the blood within the aorta and the pulmonary artery

Angioplasty or coronary bypass surgery

Blocked coronary arteries can be treated through angioplasty or coronary bypass surgery. Angioplasty involves threading a balloon-tipped catheter through a vessel in the leg to the blocked coronary artery. The balloon is inflated within the blockage to open the vessel lumen. A stent may be used as part of the balloon system to hold the vessel open after the catheter is withdrawn. Coronary bypass surgery involves harvesting a vessel and inserting its ends before and after the obstruction to effectively bypass the blockage. Several vessels can be used, like the great saphenous vein of the leg or a collateral branch of a mammary artery. But, The anatomy of the walls of arteries differs from that of veins in regard to how much pressure the vessels can withstand.

Blood pressure is usually measured in the?

Brachial artery by using a sphygmomanomete that has a pressure cuff and a device to inflate the cuff. The original instruments (sphygmomanometers) measured blood pressure as the amount of pressure necessary to lift a column of mercury a certain distance, so the units for blood pressure are millimeters of mercury (mmHg). Newer sphygmomanometers typically use a dial to indicate pressure using the same units. Two pressures are recorded and expressed as systolic pressure/diastolic pressure. For example, a normal blood pressure for a 20- to 30-year-old is 120/72 mmHg. The systolic pressure created in the brachial artery during ventricular systole is 120 mmHg. The diastolic pressure created in the brachial artery during ventricular diastole is 72 mmHg.

carditis

Can be caused by rheumatic fever (inflammation of the heart), which affects all of the heart layers including the valves. Damage caused by this disease can be long-lasting and affect an individual years later, resulting in chronic rheumatic heart disease. In this case, the heart's valves have undergone stenosis (a narrowing or constricting of the valves) from the presence of the group A streptococcal infection. Arrhythmias and ventricular dysfunction can also result from chronic rheumatic heart disease. Depending on how severe the heart damage is, heart failure may also occur. Rheumatic fever is diagnosed by physical examination and by testing for group A streptococcal infection. Electrocardiograms (explained later in the chapter) are done to assess the damage to the heart. Treatment for recurring carditis associated with rheumatic fever may include nonsteroidal anti-inflammatory drugs or corticosteroids to treat the inflammation.

Thin-walled vessels that connect the smallest arterioles to the smallest venules are?

Capillaries

TESTS USED TO VISUALIZE CORONARY VESSELS, ARTERIES, AND VEINS

Cardiac cath, CT angiography, Ultrasound, venography

By staying aerobic, cardiac muscle cells avoid fatigue, oxygen debt, and the buildup of lactic acid. Cardiac muscle cells also have the following special adaptations that enable them to use aerobic respiration almost exclusively:

Cardiac muscle cells have many very large mitochondria to perform aerobic respiration. Cardiac muscle cells are rich in myoglobin (protein for storing oxygen). Cardiac muscle cells are rich in glycogen (a starch that can be converted to glucose to be used as fuel). Cardiac muscle cells can use a variety of fuels as energy sources (glucose, fatty acids, amino acids, and ketones). Some cardiac muscle cells are further adapted to generate and carry electrical impulses.

Blood pressure is the force of the blood against the vessel walls, and it is dependent on three things:

Cardiac output, blood volume, and resistance. You can use a garden hose as an analogy for the vessel. Cardiac output is a factor because it takes into account the force of ventricular contractions. (How strong is the pump for the hose?) Blood volume makes a difference because more blood exerts a greater force on the vessel walls. (How far is the hose's water faucet turned on?) Resistance makes a difference in these three ways: 1) Blood viscosity (thickness). The amount of albumins and red blood cells determines the thickness of blood. Thicker blood offers more resistance to flow and requires more pressure to get it to move. (What if the hose contained honey instead of water?) 2) Vessel length. The greater the vessel length, the more friction occurs between the blood and the vessel walls. Friction slows the blood. (What would be the force of the same amount of water coming out of a 100-foot hose versus a 10-foot hose?) Vessel length becomes a factor in people who are obese. More pressure is needed to propel blood through their longer system of vessels to feed their increased tissue mass. 3) Vessel radius. Vessel radius becomes a factor because the smaller the radius, the more blood comes in contact with the walls of the vessel. (What happens to the amount of flow if the hose diameter is reduced?) Vessel radius (through vasoconstriction and vasodilation) can be controlled in several different ways to regulate blood pressure.

Other cardiovascular disorders

Cardiac tamonade A buildup of excessive fluid within the pericardium. Rheumatic heart disease Heart disease caused by rheumatic fever, which results in carditis and valve stenosis.

Chemoreflex

Chemoreceptors monitor oxygen, carbon dioxide, and pH. If oxygen levels fall, carbon dioxide levels rise, and pH falls, the vasomotor center will initiate widespread vessel constriction. This increases blood pressure, increasing blood flow to the lungs for more gas exchange. Oxygen levels then rise, carbon dioxide levels fall, and pH also rises.

Hypotension

Chronic low pressure below 90/60 mmHg. It can be caused by dehydration, blood loss, or anemia.

Heart CT scan

Computed tomography of the heart.

Congenital Heart Defects

Congenital defects are those present at birth. The heart is an organ that has a unique physiology during gestation, which changes once the baby is born. There are times when that transition is not complete, resulting in congenital heart defects such as patent ductus arteriosus (PDA). Once the baby is born, the ductus arteriosus should close, resulting in a completely separate aorta and pulmonary artery. When the ductus arteriosus does not close after birth, a patent ductus arteriosus results. Because the aorta remains open to the pulmonary artery, deoxygenated blood and oxygenated blood mix. This can cause the heart to become overworked and increase the pressure in the arteries in the lungs. The most common symptom of a PDA is a heart murmur. Babies can also experience difficulty breathing and feeding and poor growth. PDAs can be treated with medication or surgical procedures to close the ductus arteriosus.

Inflammatory cardiac disorders

Endocarditis- Inflammation of the endocardium. Myocarditis Inflammation of the myocardium. Pericarditis Inflammation of the pericardium.

Chronotropic Effects of Chemicals

Epinephrine from the adrenal medulla has a positive chronotropic effect on heart rate, as it complements the sympathetic nervous system. Other positive chronotropic chemicals are caffeine, norepinephrine, nicotine, and thyroid hormone. Potassium ions have a negative chronotropic effect because they interfere with repolarization of the myocardium. Increased potassium can slow the heart. Potassium ions are used as part of a lethal injection to stop a heart.

Hepatic Portal Route Example between the intestines and the liver.

In this route, blood travels from the heart to arteries to capillary beds in the small intestine and other digestive organs. Here, digested nutrients are absorbed into the blood through capillaries. Blood then travels through small veins leading to the hepatic portal vein (intervening vessels) to capillary beds in the liver, where the nutrients are processed. Blood then exits the liver via the hepatic vein on its way back to the heart. Again, blood travels through two capillary beds in this route before returning to the heart. Diagram of circulatory system routes. Note that blood travels from the mesenteric artery to capillaries in the small intestine, where nutrients are absorbed, and on to the hepatic portal vein that delivers blood to a second bed of capillaries in the liver, where the absorbed materials are processed.

Mitral valve prolapse

Inability of the valve to close causes regurgitation (backflow) of blood to the left atrium.

Thrombophlebitis

Inflammation of a vein, caused by thrombosis (formation of a blood clot in a blood vessel). There are many causes of thrombosis, including surgery, immobility, and pathological conditions that cause the blood to clot abnormally. Symptoms of thrombophlebitis include inflammation of the body part with the affected vein, pain, redness, and tenderness over the inflamed vein. Thrombophlebitis is diagnosed using tests that allow physicians to visualize the vein, such as ultrasound and venography. Although superficial thrombophlebitis does not usually cause any major health issue, deep venous thrombosis can result in chronic pain and swelling and pulmonary embolism (a blood clot that has traveled to the lungs). Treatment involves controlling the pain with analgesics, treating any infection that might be present, controlling the inflammation with nonsteroidal anti-inflammatory drugs, using anticoagulants to thin the blood, and administering thrombolytic drugs designed to dissolve the blood clot. If severe, the vein can be surgically removed. a) normal blood flow compared to thrombus within vein, (b) inflammation caused by deep venous thrombosis.

Endocarditis

Inflammation of the inside lining of the heart. The inflammation associated with endocarditis affects the tissue lining the heart chambers and covering the valves. Endocarditis is commonly caused by a bacterial infection. The bacteria can stick to the heart's endocardium and eventually grow into a vegetation (mass of bacterial growth) in the heart chamber or on the valve. The vegetation will interfere with the valve's function, allowing blood to regurgitate (leak) into the heart chamber. Untreated endocarditis can lead to congestive heart failure, arrhythmias, or the formation of emboli from pieces of vegetation that might have broken off and are traveling in the blood vessels.

Myocarditis

Inflammation of the myocardium, is usually caused by a viral, bacterial, or fungal infection that makes its way to the heart's myocardium. If left untreated, myocarditis can result in heart failure, cardiomyopathy (disease of the heart muscle), or pericarditis.

Pericarditis

Inflammation of the pericardium, can be associated with other medical conditions such as autoimmune disorders, cancers, HIV, hypothyroidism, and kidney failure. It can also result from a heart attack, surgery, or an injury to the thoracic cavity. If the inflammation of the pericardium is not treated, it can cause arrhythmias or cardiac tamponade or it can restrict the heart's movement, which may lead to heart failure.

The specialized junction between cardiac muscle cells that enable the fast transmission of electrical impulses from one cell to another are called?

Intercalated disks

Blood pressure and flow can be regulated BY

Locally (by the tissues), hormonally (by the endocrine system), or neurally (by the nervous system).

Capillaries

Microscopic capillaries are the smallest of all the vessels. Their one wall is composed of endothelium—only one cell thick with its basement membrane This thin-walled anatomy is necessary so that fluids and other materials can be exchanged between the tissues and the capillary blood. For example, oxygen is loaded to the red blood cells in the capillaries in the lungs, while carbon dioxide is being unloaded from the capillary blood to the lungs so that it can be exhaled. Blood cells move through the capillaries in single file to ensure the maximum transfer of materials. The body has approximately a billion capillaries arranged in capillary beds, yet not every cell is bordered by a capillary. From the capillaries, blood moves to the smallest of the veins—the venules.

Congestive Heart Failure

Occurs if one of the ventricles is not working as efficiently as the other. If the right ventricle's output exceeds the left ventricular output, more blood is going to the lungs than can return to the left side of the heart. Blood pressure then builds in the lungs, forcing more fluid out into the pulmonary tissue (pulmonary edema), which interferes with gas exchange in the lungs. If the left ventricle's output exceeds the output of the right ventricle, the pressure builds out in the systemic circuit and systemic edema results. This can be seen as swelling of the hands, fingers, and feet but also leads to enlargement of the liver and kidney damage. The relative amount of blood ejected from each side of the heart is shown with blue arrows. (a) Left-sided heart failure leads to pulmonary edema. (b) Right-sided heart failure leads to systemic edema.

Cardiac Cycle

One complete contraction and relaxation of the heart. This cycle may be repeated 70 to 80 times every minute. Systole is contraction, and diastole is relaxation. These terms can be used for individual chambers, but if no chamber is specified, they usually refer to the action of the ventricles.

There are three factors that affect stroke volume:

Preload is the amount of tension in the myocardium of the ventricular walls. If the walls have been stretched by the amount of blood entering, the ventricles will contract more forcibly. This follows the Frank-Starling law of the heart, which basically states that the heart must pump out the amount of blood it receives. If more blood comes in, more blood must go out. Contractility refers to the responsiveness of the cardiac muscle to contract. Stretching smooth muscle makes it more likely to contract, but this works differently. In this case, calcium makes cardiac muscle more excitable, resulting in greater contractility. Afterload concerns the pressure in the pulmonary trunk and aorta during diastole. As you may remember from the cardiac-cycle discussion, the ventricles return to shape after systole. Blood pressure is then higher in the arteries than in the ventricles, so blood tries to flow back to the ventricles. The cuplike valves in the pulmonary trunk and aorta catch the blood, and this closes the valves. The increased pressure of the blood in these vessels is afterload. This pressure on the valves must first be overcome before the ventricles can eject additional blood.

The three types of sensors that feed information to the centers in the medulla oblongata are

Proprioceptors. these nerve endings are located in the body's muscles, joints, and tendons. The information they send alerts the centers to any change in the body's activity level. Baroreceptors. These sensors are located in the aorta and carotid arteries. They maintain homeostasis by alerting the centers to any changes in blood pressure. If blood pressure falls, the cardiac accelerator center stimulates the SA and AV nodes to increase the heart rate in an effort to restore blood pressure to homeostasis. Chemoreceptors. These sensors monitor pH, carbon dioxide, and oxygen in the blood. They are located at the aortic arch, on carotid arteries, and in the medulla oblongata. Although these sensors do have an effect on heart rate, they are much more important for setting the respiratory rate.

At the base of the pulmonary trunk lies the _______ valve that allows blood to leave the right ventricle and pass to the lungs.

Pulmonary valve

Describe the path of a blood cell from the superior vena cava as it makes its way through the heart.

Right atrium>Right ventricle>pulmonary artery>lung> pulmonary vein> left atrium>left ventricle>aorta

Mean arterial pressure (MAP)

The average pressure arteries must be able to withstand. It is determined by the following equation: MAP = diastolic pressure + ⅓ pulse pressure. But if this is an average, why isn't the equation simply systolic pressure + diastolic pressure divided by 2? This would be the case if the amount of time of ventricular systole in the cardiac cycle was the same as the amount of time of ventricular diastole, but the cardiac cycle includes a rest between heartbeats. So there is more time in a relaxed state than in a contracted state. Blood pressure is further altered by arteries expanding and then recoiling, so pressure does not reach a peak and then drop to zero. The MAP for the 20- to 30-year-old in our example is 72 + ⅓(48) = 88 mmHg.

What is the pulmonary circuit?

The circuit which carries deoxygenated blood to the lungs to get oxygenated and then back to the heart.

Pulmonary circulation (pulmonary circuit)

The microscopic capillaries and the microscopic air sacs in the lungs are greatly enlarged for clarity. he red and blue colors for the vessels indicate the amount of oxygen in the blood. Red is oxygen-rich, while blue is oxygen-poor. Some mistake thinking arteries are always shown in red and veins are always shown in blue. Example of the error of that misconception: The pulmonary arteries are shown in blue because they are carrying oxygen-poor blood away from the heart to the lungs. Pulmonary veins are shown in red because they are returning oxygen-rich blood to the heart. It is better to know arteries and veins by direction of flow than by color in an illustration. Arteries carry blood away from the heart, and veins carry blood to the heart.

Pericardium

The pericardial sac is part of the pericardium—a serous membrane. The pericardium is a fluid-filled, double-walled membrane. The pericardial sac (parietal pericardium) anchors the heart to the great vessels (aorta and venae cavae), the posterior wall of the thorax, the sternum, and the diaphragm. It has a tough outer fibrous layer that does not allow for expansion. It also has a thin serous lining of epithelial tissue.

Heart Sounds during the Cardiac Cycle

The sounds you hear—lubb-dupp, lubb-dupp, lubb-dupp—are caused not by the valves themselves but by the turbulence of the blood when the valves close. The lubb corresponds to the turbulence on the AV valves, and the dupp corresponds to the turbulence created when the pulmonary and aortic valves close. The pause between heart sounds corresponds to the rest between heartbeats.

Pulse pressure indicates?

The surge of pressure that small arteries must withstand with each ventricular contraction. It is determined by this equation: Pulse pressure = systolic pressure − diastolic pressure. The pulse pressure for our 20- to 30-year-old is 120 − 72 = 48 mmHg. As stroke volume increases, pulse pressure also increases.

Heart Wall

Three layers of the heart wall—the epicardium, the myocardium, and the endocardium. These layers are described in the following list: The epicardium is the most superficial layer, composed of simple squamous epithelial tissue over loose areolar connective tissue. The myocardium is composed of cardiac muscle tissue and a fibrous skeleton of collagen and elastic fibers and is the thickest layer of the heart. The cardiac muscle of the myocardium does the heart's work by contracting to pump blood out of the heart and then relaxing so that the heart can refill. The muscle is arranged in a spiral pattern, which creates a twisting or wringing motion when the heart contracts. The collagen fibers in the myocardium are nonconductive, so they act as insulators for cells carrying electrical signals within the heart wall. These fibers also give structural support to the heart around the valves and the vessel openings. The elastic fibers in this layer enable the heart to return to shape after contractions. The endocardium lines the four chambers of the heart. Like the epicardium, it is also composed of simple squamous epithelial tissue over loose areolar connective tissue. Extensions of the epicardium cover the surface of the heart's valves and continue on as the lining of vessels.

Three basic tunic layers are:

Tunica externa is the outermost layer of the vessel wall. It is composed of loose connective tissue, which serves to anchor the vessel to surrounding tissue and provide passage for nerves and small vessels supplying blood to the external wall. Internal walls are fed by diffusion. Tunica media is the middle layer of the vessel wall. It is the thickest layer, composed mostly of smooth muscle. This tunic is more muscular in arteries than in veins of comparable size. There may be elastic fibers in this layer, depending on the vessel. Tunica interna is the lining of the vessel wall. It is composed of endothelium (simple squamous epithelial tissue and fibrous tissue). It is vital that this layer is very smooth and secretes a chemical to repel platelets so that blood can easily flow through the vessel.

Arteries and veins have three basic layers to their walls, called

Tunics

Medium Veins

Unlike venules, medium veins do have smooth muscle in the tunica media of their walls. Examples of medium veins are the radial and ulnar veins in the forearms. Many of these veins, especially in the limbs, have valves formed by folds of the tunica interna. The valves help direct the flow of blood to the heart by preventing backflow.

Septic shock

can be caused by any microorganism that causes an infection. Usually, people who suffer from septic shock either are very young or elderly or have a compromised immune system. In either case, the person does not have the ability to fight the infection, so it takes over and eventually enters the bloodstream. The infection causes very low blood pressure, which can lead to organ dysfunction and shock.

Cardiogenic shock

happens when the heart cannot pump enough blood to meet the body's needs. This can be caused by a variety of factors such as damage of the heart muscle from a heart attack, extreme arrhythmias, dysfunctional valves, or a rupture in the heart's ventricular septum.

coron/o

heart

Arterial pressure points

heart rate varies on a minute-by-minute basis. However, at rest, the normal heart rate for adult males is 64 to 72 beats/min and for adult females is 72 to 80 beats/min. The human heart may at times beat too fast or too slow. Tachycardia and bradycardia are two of the conditions in which this may be the case.

Shock

is a serious, life-threatening condition characterized by the body's organ systems not getting enough blood flow to sustain normal function. In any category of shock, the low blood pressure interferes with normal blood circulation, preventing organs from getting enough blood to function properly. Symptoms of shock include cyanosis, chest pain, confusion, dizziness, rapid and weak pulse, shallow breathing, and, in some cases, loss of consciousness. Shock is an emergency situation that requires immediate attention. Emergency medical assistance should be obtained and first-aid procedures for treatment of shock should be performed until help arrives.

Rheumatic heart disease

is an inflammatory condition of the heart associated with rheumatic fever, which causes inflammation in various body systems. Rheumatic fever is caused by a group A streptococcal bacterial infection, usually in cases of untreated inflammation of the pharynx—

Cardiac output

is the amount of blood ejected by each ventricle of the heart each minute. This output is highly adjustable to meet the needs and activity level of the body. Cardiac output (CO) is calculated by multiplying the heart rate (HR: beats per minute) by the stroke volume (SV: the amount of blood ejected from each ventricle per beat). So CO = HR × SV. If the heart rate is 75 beats/min and the stroke volume is 70 mL/beat, then the cardiac output equals 5,250 mL/min. The volume of blood in the body is typically 4 to 6 liters. At this heart rate and stroke volume, all of the blood in the body is pumped through the heart in 1 minute. Exercise can greatly increase cardiac output. The difference between the cardiac output of a heart at rest and the maximum cardiac output the heart can achieve is the cardiac reserve. Aerobic exercise and training can increase the cardiac reserve and make the heart work more efficiently

Blood flow

is the amount of blood flowing to an area in a given amount of time, and it is usually expressed in milliliters per minute (mL/min).

Atrial fibrillation

is the most common type of arrhythmia. In this case, the "faulty" electrical signals cause the atria to beat very rapidly in an irregular pattern. An irregular, fast atrial contraction results in pooling of the blood in the atria and an uncoordinated heartbeat. When the contractions of the atria and ventricles are not in sync, blood is not efficiently pumped out of the ventricles or to the rest of the body. Atrial fibrillation can result in stroke or heart failure if not monitored and treated.

There are two types of alternative systemic routes in the body:

portal routes and anastomoses.