A&P chapter 15

Where does the pointed apex lie?

at the 5th intercostal space

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

cardiac cycle

atria contracts (atrial systole) while ventricles relax (ventricular diastole) THEN ventricles contract (ventricular systole) while atria relax (atrial diastole) THEN both chambers relax briefly

cardiac muscle cells in the atrial walls

atrial syncytium

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

Where does the base of the heart lie?

beneath the second rib

Branches of the right coronary artery

posterior interventricular artery: supplies posterior ventricles. right marginal branch: supplies right atrium and ventricle

the rings of dene connective tissue also

provide attachments for heart valves and muscle fibers and prevent excess dilation of heart chambers during contraction.

Two closed circuits (pathways) are included in the cardiovascular system

pulmonary circuit and systemic circuit

Right side of the heart

pumps blood to the pulmonary circuit, blood returns to the left side

Left side of the heart

pumps to the systemic circuit, blood returns to the right side

Sympathetic impulses that innervate heart

reach heart on accelerator nerves increase heart reate, 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/minute to 60-80 beats/min decrease heart rate, due to influence ono SA and AV nodes

Right atrium

receives blood returning from systemic circuit (from the superior and inferior vena cava and coronary sinus); pumps blood to right ventricle

What is "hidden" in the large QRS complex?

record of atrial replorization is "hidden" since the ventricular or depolorization is a much larger event

Heart transplant

replacement of most of a failing heart with a donor heart

pulmonary valves

return blood from lungs to left atrium

superior and inferior vena cavae

return oxygen poor blood to the heart

Interatrial septum

separates left and right atria

interventricular septum

separates left and right ventricles

Mitral (bicuspid) valve

separates left atrium from left ventricle

aortic semilunar valve

separates left ventricle from aorta

tricuspid valve

separates right atrium from right ventricle

pulmonary semilunar valve

separates right ventricle from pulmonary trunk

The size of the heart

size of fist, varies with body size, averages 14 cm long, 9cm wide

cardiac muscle in the ventricular walls

called the ventricular syncytium

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

pulmonary circuit

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

Branches of the left coronary artery

circumflex branch: supplies left atrium and ventricle Anterior interventricular (left anterior descending) artery: supplies walls of ventricles

Junctional fibers

conducts impulses from SA node to AV node

Internodal atrial muscle

conducts impulses from SA node to atria

Systole

contraction of the heart chamber

parietal pericardium

deep to fibrous pericardium, outer layer of serous membrane

Coronary sinus

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

Portions of the pericardium

fibrous pericardium, parietal pericardium, visceral pericardium, pericardial cavity

chordae tendinae

fibrous strings that attach cusps of tricuspid and mitral valves to papillary muscle in the wall of the heart

Auricles

flap-like projections from atria, which allow atrial expansion

The heart wall

has 3 distinct layers

Regulation of the cardiac cycle

heart rate and volume of blood pumped change to meet requirements

pericardial cavity

space between visceral and parietal layers of serous pericardium

Visceral pericardium

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

HEART

is a hollow, cone-shaped organ, containing a double pump, it is divided into left and right halves

Heart

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

cardiovascular system

Consists of the heart and blood vessels

Cardiac conduction system

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

Diastole

relaxation of the heart chamber

(Erythrocytes ) red blood cells)

44% total blood volume, carry oxygen around the body on an iron-containing protein(hemoglobin)

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

Heart sounds

A heartbeat through a stethescope 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

Left Ventricular Assist Device (LVAD)

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

Cardiac center is __________________________ performs neural regulation of heart

medulla oblongota

AV (atrioventricular) bundle

Conducts impulses rapidly between AV node and bundle branches

AV (atrioventricular) node

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

pericardium (pericardial sac)

Covering over heart and proximal ends of large blood vessels

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

Characteristics of cardiac muscle cells

Have 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

Where is the heart located?

Inside the thoracic cavity, in mediastinum, behind sternum, above diaphragm, near lungs

The deflections in the normal ECG, or waves include:

P WAVE: atrial depolorization; occurs just prior ro atrial contraction QRS COMPLEX (3 waves): ventricular depolorization; occurs just prior to ventricular contraction

Left ventricle

Receives blood from the left atrium; pumps blood to systemic circuit

Left atrium

Receives blood from the pulmonary veins pumps blood to left ventricle

Right ventricle

Receives blood from the right atrium; pumps blood to lungs

Left and right bundle branches

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

SA node (pacemaker)

normally controls the heart rate, and heart rate changes occur due to factors that influence the SA node

"Lubb"

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

How do the heart chambers function?

The heart chambers function in a regulated coordinated manner

"Dupp"

The second heart sound (S2) occurs during ventricular diastole associated with closing of the pulmonary and aortic semilunar valves

Epicardium

outer layer, thin. forms inner lining of all heart chambers

What make up the skeleton of the heart?

These rings along with other fibrous masses in the interventricular septum make up the skeleton of the heart

Atria

Thin-walled upper chambers; receive blood returning to heart

SA (sinoatrial) node

pacemaker, initiates rhythmic contractions of the heart

Cardiac veins drain blood from myocardium

paths of veins lie nearly parallel to those of coronary arteries

Murmur

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

The coronary arteries

are the first two branches of the aorta

Left and right coronary arteries

supply blood tissues of the heart

rings of dense connective tissue

surround origins of pulmonary trunk and aorta, and orifices between atria and ventricles

CARDIAC CYCLE

the events that occur during a heartbeat

Ventricles

thick-walled lower chambers; pump blood into arteries

Fibrous pericardium

tough, outer Layer that surrounds double-layered serous membrane

Arteries

transport blood away from the heart

Capilllaries

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

Blood vessels

transport blood throughout the body

Veins

transport blood to the heart

systemic circuit

transports oxygen rich blood and nutrients to body cells, removes waste from cells, flows back to the heart

Early in the ventricular diastole

ventricular pressure is lower than the 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

T wave

ventricular repolorization; occurs just prior to ventricular relaxation

During ventricular systole and atrial diastole

when ventricular pressure rises about atrial pressure, AV valves close CHORDAE TENDINAE prevent the cusps of the valves from bulging too far backward into the atria atria relax blood flows into atria from venae cavae and pulmoonary veins ventricular pressure continues to increase, and opens semilunar valves Blood flows into the pulmonary trunk and aorta