The Cardiovascular System: The Heart Flashcards
Thoracic cavity between two lungs
~2/3 to left of midline
surrounded by pericardium: (2 parts)
- Fibrous pericardium
- serous pericardium
Inelastic and anchors heart in place
Fibrous pericardium
Inside is ___________ - double layer around heart
serous pericardium
layer fused to fibrous pericardium
Parietal
Inner ___________ layer adheres tightly to heart
visceral
Filled with _____________ - reduces friction during beat.
pericardial fluid
Heart Wall
Epicardium
Myocardium
Endocardium
outer layer
Epicardium
cardiac muscle
Myocardium
Responsible for the pumping action of the heart
Myocardium
makes up approximately 95% of the heart wall
Myocardium
thin layer of endothelium
Endocardium
provides a smooth lining for the chambers of the
heart and covers the valves of the heart
Endocardium
“itis”
Inflammation
is an inflammation of the myocardium that usually occurs as a complication of a viral infection, rheumatic fever, or exposure to radiation or certain chemicals or medications.
Myocarditis
refers to an inflammation of the endocardium and typically involves the heart valves. Most cases are caused by bacteria (bacterial endocarditis).
Endocarditis
Tx of Myocarditis and Endocarditis
Tx- intravenous antibiotics
Chambers of the Heart
• 4 chambers
• 2 upper chambers = Atria
• 2 lower chambers = ventricles
• Wall thickness depends on work load
receive blood from blood vessels returning blood to the heart, called _______
veins
eject the blood from the heart into blood vessels called ___________
arteries
• Atria thinnest
• Right ventricle pumps to lungs & thinner than left
Wall thickness depends on work load
Forms the right border of the heart and receives blood from three veins:
the superior vena cava,
inferior vena cava, and
coronary sinus.
thin partition between the right left atrium
interatrial septum
A prominent feature of this septum is an oval depression called the __________, the remnant of the ________, an opening in the interatrial septum of the fetal heart that normally closes soon after birth
fossa ovalis
foramen ovale
blood passes from the right atrium into the right ventricle
tricuspid valve
• Forms the right border of the heart and receives blood from three veins: the superior vena cava, inferior vena cava, and coronary sinus.
• interatrial septum - thin partition between the right left atrium
• A prominent feature of this septum is an oval depression called the fossa ovalis, the remnant of the foramen ovale, an opening in the interatrial septum of the fetal heart that normally closes soon after birth
• tricuspid valve - blood passes from the right atrium into the right ventricle
Right Atrium
• forms most of the anterior surface of the heart.
• inside of the right ventricle contains a series of ridges formed by raised bundles of cardiac muscle fibers called trabeculae.
• interventricular septum – separate right ventricle from the left ventricle
• blood passes from the right ventricle through the pulmonary valve into a large artery called the pulmonary trunk, which divides into right and left pulmonary arteries and carries blood to the lungs.
Right Ventricle
forms most of the anterior surface of the heart.
Right Ventricle
inside of the right ventricle contains a series of ridges formed by raised bundles of cardiac muscle fibers called __________
trabeculae.
separate right ventricle from the left ventricle
interventricular septum
blood passes from the right ventricle through the _________ into a large artery called the ___________, which divides into right and left pulmonary arteries and carries blood to the lungs.
pulmonary valve
pulmonary trunk
• receives blood from the lungs through four pulmonary veins.
• Blood passes from the left atrium into the left ventricle through the bicuspid (mitral) valve.
• It is also called the left atrioventricular valve.
Left Atrium
receives blood from the lungs through four pulmonary veins.
Left Atrium
Blood passes from the left atrium into the left ventricle through the ____________
bicuspid (mitral) valve.
It is also called the left atrioventricular valve.
Left Atrium
• the thickest chamber of the heart, averaging 10–15 mm
• blood passes from the left ventricle through the aortic valve into the ascending aorta.
Left Ventricle
the thickest chamber of the heart, averaging 10–15 mm
Left Ventricle
blood passes from the left ventricle through the _________ into the ascending aorta.
aortic valve
• Superior & inferior Vena Cavae
— Delivers deoxygenated blood to R. atrium
from body
— Coronary sinus drains heart muscle veins
• R. Atrium -> R. Ventricle
• pumps through Pulmonary Trunk
• -> R & L pulmonary arteries
• -> lungs
Great Vessels Of Heart-Right
• Pulmonary Veins from lungs
— oxygenated blood
• -> L. atriumè Left ventricle
• -> ascending aorta -> body
• Between pulmonary trunk & aortic arch is ligamentum arteriosum (fetal ductus arteriosum remnant) - which connects the arch of the aorta and pulmonary trunk.
Great Vessels Of Heart-Left
Pulmonary Veins from lungs
oxygenated blood
Between pulmonary trunk & aortic arch is _____________(fetal ductus arteriosum remnant) - which connects the arch of the aorta and pulmonary trunk.
ligamentum arteriosum
Designed to prevent back flow in response to pressure changes
Valves
Between atria and ventricles
Atrioventricular (AV) valves
Right
tricuspid valve (3 cusps)
Left
bicuspid or mitral valve
near origin of aorta & pulmonary trunk
Semilunar valves
valves respectively
Aortic & pulmonary
• Designed to prevent back flow in response to pressure changes
• Atrioventricular (AV) valves
— Between atria and ventricles
• Right = tricuspid valve (3 cusps)
• Left = bicuspid or mitral valve
• Semilunar valves near origin of aorta & pulmonary trunk
• Aortic & pulmonary valves respectively
Valves
• narrowing of a heart valve opening that restricts blood flow is known as stenosis.
• mitral stenosis - scar formation or a congenital defect causes narrowing of the mitral valve.
• Mitral valve prolapse (MVP) backflow of blood from the left ventricle into the left atrium
• aortic stenosis - aortic valve is narrowed, and in aortic insufficiency there is backflow of blood from the aorta into the left ventricle.
• Rheumatic fever - acute systemic inflammatory disease that usually occurs after a streptococcal infection of the throat.
Heart Valve Disorders
• Blood flow through vessels in myocardium = coronary circulation
• Left & right coronary arteries
— Branch from the ascending aorta and supply
oxygenated blood to the myocardium
• Most of the deoxygenated blood from the myocardium drains into a large vascular sinus in the coronary sulcus on the posterior surface of the heart, called the coronary sinus
• Empties into right atrium
Blood Supply Of Heart
Blood flow through vessels in myocardium =
coronary circulation
Branch from the ascending aorta and supply
oxygenated blood to the myocardium
Left & right coronary arteries
Most of the deoxygenated blood from the myocardium drains into a large vascular sinus in the coronary sulcus on the posterior surface of the heart, called the
coronary sinus
Empties into right atrium
Blood Supply Of Heart
only 1% of the cardiac muscle fibers become autorhythmic fibers
Conduction System
• only 1% of the cardiac muscle fibers become autorhythmic fibers;
• Two important functions:
1. They act as a pacemaker, setting the rhythm of electrical excitation that causes contraction of the heart.
2. they form the cardiac conduction system, a network of specialized cardiac muscle fibers that provide a path for each cycle of cardiac excitation to progress through the heart.
Conduction System
setting the rhythm of electrical excitation that causes contraction of the heart.
pacemaker
a network of specialized cardiac muscle fibers that provide a path for each cycle of cardiac excitation to progress through the heart.
cardiac conduction system
Two important functions of Conduction System
- pacemaker
- cardiac conduction system (CCS)
• Normally begins at sinoatrial (SA) node
• -> Atria & atria contract
• -> AV node - slows
• -> AV bundle (Bundle of His)
• -> bundle branches -> Purkinje fibers
• -> apex and up- then ventricles contract pushing the blood upward toward semilunar valve.
Sequence of AP propagate through the conduction system
• Depolarize spontaneously
• sinoatrial node ~100times /min
• also AV node ~40-60 times/min
• in ventricle ~20-35 /min
• Fastest one run runs the heart = pacemaker
• Normally the sinoatrial node
Pacemaker
Depolarize spontaneously
Pacemaker
sinoatrial node
~100times /min
also AV node
40-60 times/min
in ventricle
20-35 /min
Fastest one run runs the heart
pacemaker
Normally the sinoatrial node
pacemaker
• if the pacing rate is so slow (20–35 bpm) that blood flow to the brain is inadequate.
• artificial pacemaker - a device that sends out small electrical currents to stimulate the heart to contract.
• A pacemaker consists of a battery and impulse generator and is usually implanted beneath the skin just inferior to the clavicle.
• Many of the newer pacemakers, referred to as activity-adjusted pacemakers, automatically speed up the heartbeat during exercise.
Artificial Pacemakers
if the pacing rate is so slow (20–35 bpm) that blood flow to the brain is ________
inadequate
a device that sends out small electrical currents to stimulate the heart to contract.
artificial pacemaker
A pacemaker consists of a battery and impulse generator and is usually implanted beneath the skin just inferior to the __________.
clavicle
Many of the newer pacemakers, referred to as ____________, automatically speed up the heartbeat during exercise.
activity-adjusted pacemakers
Recording of currents from cardiac conduction on skin
electrocardiogram (EKG or ECG)
is a composite record of action potentials produced by all the heart muscle fibers during each heartbeat.
ECG
3 waves
P wave
QRS complex
T-wave
represents atrial depolarization
P wave
• Contraction begins right after peak
• Repolarization is masked in QRS
P wave
• rapid ventricular depolarization
• Contraction of ventricle
QRS complex
• ventricular repolarization
• Just after ventricles relax
T-wave
indicate enlargement of an atrium;
Larger P waves
may indicate a myocardial infarction
Enlarged Q wave
generally indicates enlarged ventricles
Enlarged R wave
If ______ is flatter than normal = heart muscle is receiving insufficient oxygen—exp, in coronary artery disease.
T wave
The _______ in hyperkalemia (high blood K level).
T wave may be elevated
in coronary artery disease and rheumatic fever.
P–Q interval lengthens
_______ in acute myocardial infarction and depressed when the heart muscle receives insufficient oxygen.
S–T segment is elevated
________ by myocardial damage, myocardial ischemia (decreased blood flow), or conduction abnormalities.
Q–T interval may be lengthened
A single ______ includes all the events associated with one heartbeat.
cardiac cycle
cardiac cycle consists of :
systole and diastole of the atria PLUS
systole and diastole of the ventricles
lasts about 0.1 sec, the atria are contracting
(P -wave). The ventricles are relaxed (diastole).
atrial systole
which lasts about 0.3 sec, the ventricles are contracting. The atria are relaxed in (atrial diastole).
ventricular systole
Ventricular pressure drops below atrial pressure & AV valves open -> ventricular filling occurs
after T-wave -> ventricular diastole
Finishes filling ventricle (25mL)
After P-wave -> atrial systole
• Pressure pushes AV valves closed
• Pushes semilunar valves open and ejection occurs
• Ejection until ventricle relaxes enough for arterial pressure to close semilunar valves
After QRS -> ventricular systole
Cardiac cycle
- Relaxation period
- Atrial systole
- Ventricular systole
the volume ejected per beat from each ventricle, equals end-diastolic volume minus end-systolic volume
Stroke volume (SV = EDV - ESV)
At rest, the stroke volume is about _____
130 mL - 60mL = 70 mL (a little more than 2 oz).
is the volume of blood ejected from the left ventricle (or the right ventricle) into the aorta (or pulmonary trunk) each minute.
Cardiac output (CO)
Cardiac output equals the Stroke volume, multiplied by the Heart rate (HR)
CO(mL/min) = SV(mL/beat) • HR (beats/min)
Three factors regulate SV and ensure that the left and right ventricles pump equal volumes of blood:
Preload
Contractility
Afterload
the degree of stretch on the heart before it contracts
preload
the forcefulness of contraction of individual ventricular muscle fibers
contractility
the pressure that must be exceeded before ejection of blood from the ventricles can occur.
afterload
• Degree of stretch = Frank-Starling law
— Increase diastolic Volume increases strength of contraction -> increased S.V.
— Increased venous return -> increased S.V.
• When HR exceeds about 160 beats/min, SV usually declines due to the short filling time
• High back pressure in artery -> decreased S.V. — Slows semilunar valve opening
Control of Stroke Volume (S.V.) Preload
Degree of stretch
Frank-Starling law
When HR exceeds about 160 beats/min, _________ due to the short filling time
SV usually declines
• positive inotropic agents - substances that increase contractility
— Ex. stimulation of the sympathetic div of ANS, hormones such as Epi & NE increase Ca2+ level and drug digitalis.
• negative inotropic agents - decrease contractility
— Ex. inhibition of the sympathetic div of the ANS, anoxia, acidosis, some anesthetics, and increased K level in the interstitial fluid have negative inotropic effects.
• Calcium channel blockers - reduce Ca2+ inflow
Control of Stroke Volume (S.V.)
Contraction
- substances that increase contractility
Ex. stimulation of the sympathetic div of ANS, hormones such as Epi & NE increase Ca2+ level and drug digitalis.
positive inotropic agents
- decrease contractility
Ex. inhibition of the sympathetic div of the ANS, anoxia, acidosis, some anesthetics, and increased K level in the interstitial fluid have negative inotropic effects.
negative inotropic agents
reduce Ca2+ inflow
Calcium channel blockers
• pressure that must be overcome before a semilunar valve can open.
• increase in afterload causes stroke volume to decrease,
• More blood remains in the ventricles at the end of systole.
• Conditions that can increase afterload include hypertension and narrowing of arteries by atherosclerosis
Control of Stroke Volume (S.V.) Afterload
___________ causes stroke volume to decrease
increase in afterload
• loss of pumping efficiency by the heart.
• Causes: coronary artery disease, congenital defects, long-term high blood pressure, myocardial infarctions, and valve disorders.
• As a result, blood backs up in the lungs and causes pulmonary edema, that can cause suffocation if left untreated.
• If right ventricle fails first, blood backs up in the systemic veins and, over time, the kidneys cause an increase in blood volume. Resulting peripheral edema - most noticeable in the feet and ankles.
Congestive Heart Failure
loss of pumping efficiency by the heart.
Congestive Heart Failure
As a result, blood backs up in the lungs and causes ________, that can cause suffocation if left untreated.
pulmonary edema
If right ventricle fails first, blood backs up in the systemic veins and, over time, the kidneys cause an increase in blood volume. Resulting ___________- most noticeable in the feet and ankles.
peripheral edema
• Pacemaker adjusted by nerves
— Cardiovascular center in Medulla
• Parasympathetic- ACh slows
— via vagus nerve (CN X)
• Sympathetic - Norepinephrine speeds
• Sensory input for control:
— Baroreceptors (aortic arch & carotid sinus)-monitor the stretching of major arteries and veins caused by the pressure of the blood flowing.
— Chemoreceptors- O2, CO2, pH
Controls- Heart Rate
adjusted by nerves
Pacemaker
ACh slows
Parasympathetic
Norepinephrine speeds
Sympathetic
Sensory input for control
• Baroreceptors (aortic arch & carotid sinus)
• Chemoreceptors
monitor the stretching of major arteries and veins caused by the pressure of the blood flowing.
Baroreceptors (aortic arch & carotid sinus)
O2, CO2, pH
Chemoreceptors
• Epinephrine & norepinephrine increase
H.R.
• Thyroid hormones stimulate H.R.
• Hyperthyroidism causes tachycardia
Hormones
Hyperthyroidism causes
tachycardia
• Increased Na+ or K+ decrease H.R. &
contraction force
• Increased Ca2+ increases H.R. &
contraction force
Ions
Increased ______ decrease H.R. &
contraction force
Na+ or K+
Increased ______ increases H.R. &
contraction force
Ca2+
• Aerobic exercise (longer than 20 min) strengthens cardiovascular system:
• Brisk walking, running, bicycling, cross-country skiing, and swimming are examples of aerobic activities.
• Well trained athlete -> doubles maximum C.O.
• Resting C.O. about the same but resting H.R.
decreased (40–60 bpm)
• Regular exercise also helps to reduce blood pressure, anxiety, and depression; control weight; and increase the body’s ability to dissolve blood clots.
Exercise and the Heart
