Download Cardiovascular System

Heart
• Considered to be a duel pump because
the both sides work independently of one
another.
• The right side pumps blood to the lungs.
– (pulmonary circulation)
• The left side pumps blood to all of the
other organs of the body
– (systemic circulation)
Pathway of Blood Through the Heart and Lungs
Major Vessels of the Heart
• Vessels returning blood to the heart include:
– Superior and inferior venae cavae
– Right and left pulmonary veins
• Vessels carrying blood away from the heart
include:
– Pulmonary trunk, which splits into right and left
pulmonary arteries
– Ascending aorta (three branches) –, left
common carotid, and subclavian arteries
Figure 19.5a
Figure 19.5b
Ventricles of the Heart
• Ventricles eject
blood from the
heart
– Right ventricle
pumps blood into
the pulmonary
trunk which will go
to the lungs.
• Left ventricle
pumps blood into
the aorta which will
go to the rest of
the body
Atrioventricular Heart Valves
•
•
Heart valves ensure unidirectional blood flow
through the heart.
Atrioventricular (AV) valves lie between the atria
and the ventricles.
–
–
•
•
Tricuspid Right
Bicuspid (Mitral) Left
AV valves prevent backflow of blood into the atria
when ventricles contract.
Chordae tendineae anchor AV valves to papillary
muscles
–
First heart sound (LUB) when valves close
• During diastole there is less pressure in the in ventricle. AV Valves
open and filling the ventricle.
• During systole the AV valves prevent the back flow of blood into the
atrium.
– Failure to prevent the blood from going back into the atria (systolic heart
murmur)
Semilunar Heart Valves
• Aortic semilunar valve lies between the left
ventricle and the aorta.
• Pulmonary semilunar valve lies between
the right ventricle and pulmonary trunk
– Semilunar valves prevent backflow of blood
into the ventricles.
• Second heart sound (DUB) when valves
close.
Figure 19.9b
• During ventricular systole the semilunar valves allow blood
to be ejected from the ventricles into the aorta and
pulmonary trunk.
• During diastole they prevent the back flow of blood back
into the ventricles.
– Failure to prevent the backflow of blood into the ventricles.
(diastolic murmur)
Coronary Arteries
• Left coronary artery (LCA)
– anterior interventricular branch
• supplies blood to interventricular
septum and anterior walls of
ventricles
– circumflex branch
• passes around left side of heart in
coronary sulcus, supplies left atrium
and posterior wall of left ventricle
• Right coronary artery (RCA)
– right marginal branch
• supplies lateral R atrium and ventricle
– posterior interventricular branch
• supplies posterior walls of ventricles
• Cardiac muscle is short and striated.
• Ability to beat independent of
stimulation from the nervous
system.
– ANS
• Functional syncytium:
– intercalated discs connect
cardiac cells which allow free
passage of ions.
– This allows the spread of action
potentials from one myocyte to
another.
• The result is a coordinated
contraction that moves the
blood out of the heart.
Major Vessels
Figure 20.23a
Figure 20.27
Figure 20.28a
Mesenteric Vessels
Blood Pressure (BP)
• Force per unit area exerted on the wall of a
blood vessel by its contained blood.
– Expressed in millimeters of mercury (mm Hg)
– Measured in reference to systemic arterial BP
in large arteries near the heart.
• The differences in BP within the vascular system
provide the driving force that keeps blood
moving from higher to lower pressure areas.
Resistance
• Resistance – opposition to flow
– Measure of the amount of friction blood
encounters as it passes through vessels.
– Generally encountered in the systemic
circulation.
– Referred to as peripheral resistance (PR)
• The three important sources of resistance are
blood viscosity, total blood vessel length, and
blood vessel diameter.
Resistance Factors: Viscosity and Vessel Length
• Resistance factors that remain relatively
constant are:
– Blood viscosity – thickness or “stickiness” of the
blood the greater the resistance.
– Blood vessel length – the longer the vessel, the
greater the resistance encountered.
• Diameter- Smaller diameter arterioles are the
major determinants of peripheral resistance
– Fatty plaques from atherosclerosis: decreases both
diameter and elasticity of vessel which results in:
• Cause turbulent blood flow
• Dramatically increase resistance due to turbulence
Blood Flow, Blood Pressure, and
Resistance
• Blood flow (F) is directly proportional to the
difference in blood pressure
– If P increases, blood flow speeds up; if P
decreases, blood flow declines
• Blood flow is inversely proportional to
resistance (R)
– If R increases, blood flow decreases
• R is more important than P in influencing
local blood pressure.
EKG
Why Get an EKG
• Unexplained chest pain, or reduced blood flow
to the heart (ischemia), shortness of breath,
dizziness, fainting, or rapid and irregular
heartbeats (palpitations).
• Identify ventricle hypertrophy and other changes
of the myocardium.
• Check how well mechanical devices, such as
pacemakers or defibrillators implanted in the
heart, are working to control a normal heartbeat.
Electrocardiography
• Electrical activity is recorded by
electrocardiogram (ECG)
• P wave corresponds to depolarization of SA
node resulting in atrial systole
• QRS complex corresponds to ventricular
depolarization resulting in Ventricular contraction
and blood being ejected from the heart.
– Atrial repolarization is hidden with in QRS complex
• ST segment - ventricular systole
• T wave corresponds to ventricular repolarization
EKG
Normal Sinus Rhythm
• The heart is being paced by the SA node. There is a degree of
regularity between all components of EKG
• Normal heart rate ranges between 60-100bpm.
– 75bpm( average) dependent on activity.
• Find a QRS that falls on a solid black line.
• Then count 300-150-100-75-60-50-43 for each successive black
line. Distance between QRS complexes are 5 black lines =60 Beats
per minute
Sinus Bradycardia
(SB) is defined as a sinus rhythm with a rate below 60 bpm.
• Normally found in well trained persons and during sleep.
• May also be found in patients post myocardial infarction
• Beta Blockers reduce sympathetic input to the heart
reducing both cardiac workload and blood pressure.
– If on this medication heart rate is not a valid measure of exertion.
Tachycardia
• Defined as a heart rate greater than 100bpm
– This is a perfectly normal rhythm if you are exercising.
• Heart beats faster under the influence of the SNS in order to meet
the bodies increased demand of oxygen.
• Stress, anxiety, or underline pathology may result in an elevated
HR.
– Context is important.
Atrial Fibrillation
• Multiple ectopic foci fire chaotically in the atrium
• This diminished the atriums ability to contract and results
in pooling in the atrium.
– (High risk of blood clot formation =need blood thinners)
– Loss of atrial kick = reduced SV
– May lead to a more severe arrhythmia.
Premature Ventricular Contraction
(PVC)
Ventricles contract before the atria in a cardiac
cycle
The SA node is not pacing the heart here.
– typically caused by emotional stress, lack of sleep,
smoking or stimulants (caffeine) which initiate an AP
in the ventricles
Ventricular Tachycardia( V-Tach)
• Heart rate greater then 150 that originates from an irritable foci in
the ventricle.
• It is a regular rhythm but is hemo-dynamically inefficient. The heart
CO will be very poor due to reduced ventricular filling.
• Reduced CO leads to poor coronary perfusion.
• Will lead to Ventricular Fibrillation
Ventricular Fibrillation( V-FIB)
• This is the most dangerous rhythm. There is no discernable pattern.
• Multiple areas of the ventricles are initiating impulses at the same
time resulting in a quivering heart instead of a contracting heart.
• The heart will not efficiently fill up with blood.
– Oxygen will not be delivered to the tissues.
– Toe tag is eminent unless a defibrillator ( AED) is near.