chapter 15

Which way do arteries carry blood?

away from the heart

Superior and inferior venae cavae

return oxygen-poor blood to heart

What do the pulmonary veins do?

return oxygen-rich blood from lungs to left atrium

What does the tricuspid valve separate?

right atrium and right ventricle

What does the Mitral(bicuspid) valve separate?

separates left atrium from left ventricle

What does the Aortic semilunar valve seperate?

separates left ventricle from aorta

what does the Pulmonary semilunar valve seperate?

separates right ventricle from pulmonary trunk

interatrial septum

separates the left and right atria

interventricular septum

separates the two ventricles

types of capillaries

continuous, fenestrated, sinusoids

cardiac veins

drain the myocardium of blood, Paths of veins lie nearly parallel to those of coronary arteries

wall of the heart(superficial to deep)

epicardium, myocardium, endocardium

What does the cardiovascular system consist of?

heart and blood vessels

cardiac conduction system

Specialized group of cardiac muscle cells, which initiate and distribute cardiac action potentials through myocardium

Endocardium

• Inner layer, thin • Forms inner lining of all heart chambers

Promoting angiogenesis

- Body secretes VEGF in response to blocked coronary artery - If this is not sufficient, VEGF may be able to be delivered in time-release capsules

organization of the heart

-Right side pumps to pulmonary circuit, blood returns to the left side -Left side pumps to systemic circuit, blood returns to the right side

Blood flow through the heart

1-Superior & Inferior Vena Cava, 2-Rt Atrium, 3-Tricuspid Valve, 4- Rt Ventricle, 5-Pulmonary semilunar Valve, 6- pulmonary trunk 6-Pulmonary Artery, 7- Lungs-(dump Co2, Pick up O2) 8-Pulmonary veins 9- Lt Atrium, 10- Mitral Valve (Bicuspid), 11-Lt Ventricle, 12- Aortic semilunar Valve, 13-Aortic trunk, 14- Body

heart sounds

A heartbeat through a stethoscope sounds like "lubb-dupp" Sounds are due to closing of heart valves, and vibrations associated with a sudden slowing of blood flow during contraction/relaxation of chambers

Murmur

Abnormal heart sound derived from incomplete closure of cusps of a valve

Arrhythmias(several types)

Arrhythmias: Altered heart rhythms; several types: • Fibrillation: • Uncoordinated, chaotic contraction of small areas of myocardium • Atrial fibrillation not life-threatening; ventricular fibrillation is often fatal • Tachycardia: Abnormally fast heartbeat, >100 beats/min at rest • Bradycardia: Abnormally slow heartbeat, <60 beats/min at rest • Flutter: Rapid, regular contraction of a heart chamber, 250 to 350 beats/min. • Premature Beat: Beat that occurs before expected in normal cardiac cycle; often originates from ectopic regions of heart (other than SA node) • Ectopic Pacemaker: Damage to SA node may lead to AV node taking over, and act as secondary pacemaker; 40 to 60/min, instead of 70 to 80 • Artificial Pacemaker: Device used to treat disorders of cardiac conduction system; implantable and battery-powered

precapillary sphincters

Band of smooth muscle that wraps around beginning of capillary, to regulate blood flow

blood vessels

Blood vessels are organs of the cardiovascular system Blood vessels form a closed circuit, transporting blood from heart to body cells (or lungs) and back to the heart

exchanges in capillaries

Capillaries exchange gases, nutrients, and metabolic byproducts between blood and tissue around cells. Exchange occurs by these 4 methods: Diffusion, Filtration, Osmosis and Transcytosis

What do capillaries do?

Capillaries transport blood between arteries and veins, and perform nutrient, gas, and waste exchange

Stem Cell Technology

Cardiac muscle tissue can now be cultured from altered somatic cells or from stem cells; may allow "stem cell heart patches" in the future

what is the composition of the Myocardium?

Cardiac muscle tissue separated by connective tissue and includes blood and lymph capillaries and nerve fibers

What does the pulmonary circuit do?

Carries oxygen-poor blood from heart to lungs, drops off carbon dioxide, picks up oxygen, flows back to heart

What are chordae tendinae?

Chordae tendineae are fibrous strings that attach cusps of tricuspid and mitral valves to papillary muscles in wall of heart

Junctional Fibers

Conduct impulses from SA node to AV node

Internodal Atrial Muscle

Conducts impulses from SA node to atria

AV (Atrioventricular) Bundle (of His)

Conducts impulses rapidly between SA node and bundle branches

AV (atrioventricular) node

Conducts impulses to AV Bundle; delays impulse, so that atria finish contracting before ventricles contract

What is the function of the Myocardium?

Contracts to pump blood from the heart chambers

parietal pericardium

Deep to fibrous pericardium; outer layer of serous membrane

Pressure and Volume Changes of a Cardiac Cycle

During a cardiac cycle, the pressure in the heart chambers rises and falls Pressure changes open and close the valves

coronary sinus

Enlarged vein into which other cardiac veins drain; drains into right atrium

Coverings of heart (Superficial to Deep)

Fibrous pericardium Parietal pericardium visceral pericardium pericardial cavity

Auricles

Flap-like projections from atria, which allow atrial expansion

What is the function of the Endocardium?

Forms a protective inner lining of the chambers and valves

What is the function of the epicardium?

Forms a protective outer covering; secretes serous fluid

What is the heart?

Heart is a hollow, cone-shaped, muscular pump; generates force to transport respiratory gases, nutrients, and wastes through body

regulation of cardiac cycle

Heart rate and volume of blood pumped change to meet requirements Cardiac center in medulla oblongata performs neural regulation of heart SA node (pacemaker) normally controls the heart rate, and heart rate changes occur due to factors that influence the SA node Sympathetic and parasympathetic fibers modify the heart rate in response to changing conditions, such as: • Physical exercise • Body temperature • Fight-or-flight response • Concentration of various ions, such as K+ and Ca+2

capillary arrangement

Higher the metabolic rate in a tissue, the denser its capillary networks. Rich capillary supply in muscle and nerve tissue, since they use a large amount of O2 and nutrients. Tissues with lower metabolic rate, such as cartilage, have fewer capillaries.

Visceral pericardium

Inner layer of serous membrane; attached to surface of heart; also called the epicardium

Purkinje Fibers

Large fibers that conduct impulses to ventricular myocardium; conduct impulses to apex first; whorled pattern of muscle in ventricles contract with twisting motion

left and right coronary arteries

Left and right coronary arteries supply blood to tissues of the heart • The coronary arteries are first 2 branches of the aorta • Branches of right coronary artery: • Posterior interventricular artery: Supplies posterior ventricles • Right marginal branch: Supplies right atrium and ventricle

Aortic valve location and function

Location-Entrance to aorta Function-Prevents blood from moving from the aorta into the left ventricle during ventricular relaxation

Pulmonary valve location and function

Location-Entrance to pulmonary trunk Function-Prevents blood from moving from the pulmonary trunk into the right ventricle during ventricular relaxation

Mitral(bicuspid) valve location and function

Location-Left atrioventricular orifice Function-Prevents blood from moving from the left ventricle into the left atrium during ventricular contraction

Tricuspid valve location and function

Location-Right atrioventricular orifice Function-Prevents blood from moving from the right ventricle into the right atrium during ventricular contraction

Left Ventricular Assist Device (LVAD)

Mechanical half-heart, used in some cases temporarily, until donor heart is available

what is the composition of the Endocardium?

Membrane of epithelium and underlying connective tissue, and includes blood vessels and specialized fibers

capillary permeability

Openings in walls of capillaries are thin slits found where endothelial cells overlap Sizes of openings vary among tissues; permeability varies with size of slits

SA (Sinoatrial) Node

Pacemaker; initiates rhythmic contractions of the heart

What are the 2 circuits of the cardiovascular system?

Pulmonary circuit and systemic circuit

heart transplant

Replacement of most of a failing heart with a donor heart

4 chambers of the heart and each of their functions

Right atrium: Receives blood returning from systemic circuit (from the superior and inferior vena cavae and coronary sinus); pumps blood to right ventricle • Right ventricle: Receives blood from the right atrium; pumps blood to lungs • Left atrium: Receives blood from the pulmonary veins; pumps blood to left ventricle • Left ventricle: Receives blood from the left atrium; pumps blood to systemic circuit

What is the composition of the epicardium?

Serous membrane of connective tissue covered with epithelium and includes blood and lymph capillaries and nerve fibers; adipose tissue around large blood vessels of the heart

pericardial cavity

Space between visceral and parietal layers of serous pericardium

Left and Right Bundle Branches

Split off from AV bundle, conduct impulses to Purkinje fibers on both sides of heart

sytole ; diastole

Systole: Contraction of a heart chamber • Diastole: Relaxation of a heart chamber • The heart chambers function in regulated, coordinated manner

Ventricles

Thick-walled lower chambers; pump blood into arteries

Atria

Thin-walled upper chambers; receive blood returning to heart

fibrous pericardium

Tough outer layer, that surrounds double-layered serous membrane

What does the systemic circuit do?

Transports oxygen-rich blood and nutrients to body cells, removes wastes from cells, flows back to heart

Implantable Replacement Heart

titanium and plastic artificial heart, used in people that cannot have heart transplant, and do not have long to live

which way do veins carry blood?

toward the heart

What do blood vessels do?

transport blood throughout the body

Electrocardiogram (ECG, EKG)

• A recording of electrical changes that occur in the myocardium during the cardiac cycle • Used to assess ability of heart to conduct impulses• The deflections in the normal ECG, or waves, include: • P wave: Atrial depolarization; occurs just prior to atrial contraction • QRS complex (3 waves): Ventricular depolarization; occurs just prior to ventricular contraction • Record of atrial repolarization is "hidden" in the large QRS complex, since ventricular depolarization is a much larger event • T wave: Ventricular repolarization; occurs just prior to ventricular relaxation

types of blood vessels(5)

• Arteries: Carry blood away from the ventricles of the heart • Arterioles: Receive blood from the arteries, and carry it to the capillaries • Capillaries: Sites of exchange of substances between the blood and the body cells • Venules: Receive blood from the capillaries, and conduct it to veins • Veins: Receive blood from venules, and carry it back to the atria of the heart

Cardiac Cycle (the events that occur during a heartbeat):

• Atria contract (atrial systole) while ventricles relax (ventricular diastole) • Then ventricles contract (ventricular systole) while atria relax (atrial diastole) • Then both chambers relax briefly

During atrial systole and ventricular diastole

• Atria contract and ventricles are relaxed • The AV valves open and the semilunar valves close • Atrial systole pushes remaining 30% of blood into the ventricles, causing ventricular pressure to increase

Example of baroreceptor reflex response

• Baroreceptors in aortic arch and carotid artery sinuses detect blood pressure • Increased pressure stretches receptors • Parasympathetic cardioinhibitory reflex lowers heart rate and blood pressure

branches of the left coronary artery

• Circumflex branch: Supplies left atrium and ventricle • Anterior interventricular (left anterior descending) artery: Supplies walls of ventricles

Blood flow distribution to capillaries

• During exercise, muscle capillaries receive more blood flow, and digestive system capillaries receive less • After a meal, digestive system capillaries receive more blood flow, and muscles receive less

Characteristics of cardiac muscle cells

• Have 1 central nucleus, and form branching networks • Intercalated discs between cells contain desmosomes for structural support, and gap junctions to spread action potentials through a network of cells • Form a functional syncytium, mass of merging cells that function as a unit: 2 such masses exist in the heart :• In the atrial walls; called the atrial syncytium • In the ventricular walls; called the ventricular syncytium

fenestrated capillaries

• Have large openings in cell membranes and between endothelial cells • Found in endocrine glands, kidneys, small intestine

sinusoidal capillaries

• Have largest openings; spaces between cells are small cavities • Discontinuous • Found in liver, spleen, and red bone marrow

continuous capillaries

• Have small openings • Found in muscle, connective and nervous tissues, and skin

Other factors that affect heart rate

• Impulses from hypothalamus and cerebrum • Body temperature • Levels of K+ and Ca+2

Stretch Receptors in venae cavae

• Increase in blood pressure stretches receptors • Sympathetic cardioaccelerator reflex increase heart rate and force of contraction, to lower venous pressure

Baroreceptor reflexes

• Involve cardiac control center in medulla oblongata • Balance inhibitory and excitatory effects of parasympathetic and sympathetic fibers • Contains a cardioinhibitor reflex center and a cardioaccelerator reflex center

Myocardium

• Middle layer; thickest layer • Composed of cardiac muscle tissue

epicardium

• Outer layer, thin • Also called visceral pericardium • Reduces friction

Sympathetic impulses that innervate heart

• Reach heart on accelerator nerves • Increase heart rate, due to influence on SA and AV nodes, atrial and ventricular myocardium

Parasympathetic impulses that innervate heart

• Reach heart via vagus nerves • Lower SA node rate of 100 beats/min to 60 to 80 beats/min • Decrease heart rate, due to influence on SA and AV nodes

skeleton of the heart(4 bullet points)

• Rings of dense connective tissue surround origins of pulmonary trunk and aorta, and orifices between atria and ventricles. • Provide attachments for heart valves and muscle fibers • Prevent excess dilation of heart chambers during contraction - These rings, along with other fibrous masses in the interventricular septum, make up the skeleton of the heart.

Size and location of the heart

• Size of fist, varies with body size, averages 14 cm long, 9 cm wide • Located in inside thoracic cavity, in mediastinum, behind sternum, above diaphragm, near lungs • Broad base lies beneath the 2nd rib • Pointed apex lies at the 5th intercostal space -Hollow, cone-shaped organ, containing double pump • Divided into left and right halves

Arterioles

• Smaller and thinner-walled than arteries (same 3 layers or tunics) • Walls of middle and outer layers become thinner as arterioles become smaller Both arteries and arterioles can undergo vasoconstriction and vasodilation

Capillaries

• Smallest-diameter blood vessels • Connect the smallest arterioles and the smallest venules • Extensions of the inner lining of arterioles • Walls consist of endothelium (simple squamous epithelium) only • Semipermeable; exchange substances between blood and tissue fluid • Capillary blood flow regulated mainly by precapillary sphincters: smooth muscle surrounding capillary when it branches off arteriole or metarteriole

"Lubb"

• The first heart sound (S1) • Occurs during ventricular systole • Associated with closing of the AV valves

"Dupp"

• The second heart sound (S2) • Occurs during ventricular diastole • Associated with closing of the pulmonary and aortic semilunar valves

Arteries

• Thick, strong wall, thicker than walls of veins • 3 layers or tunics • Transport blood under high blood pressure • Give rise to smaller arterioles

Preventing angiogenesis

• Tumors secrete VEGF to nourish themselves • Antiangiogenesis drugs are used to treat cancer and age-related macular degeneration

3 layers of arteries

• Tunica interna (intima): innermost layer, endothelium • Tunica media: smooth muscle and elastic tissue • Tunica externa (adventitia): outer layer, connective tissue

early ventricular diastole

• Ventricular pressure is lower than atrial pressure • Atria and ventricles are relaxed • AV valves open, and semilunar valves are closed • About 70% of blood flows passively from atria into ventricles

During ventricular systole and atrial diastole

• When ventricular pressure rises about atrial pressure, AV valves close • Chordae tendineae prevent the cusps of the valves from bulging too far backward into the atria • Atria relax • Blood flows into atria from venae cavae and pulmonary veins • Ventricular pressure continues to increase, and opens the semilunar valves • Blood flows into the pulmonary trunk and aorta