Download The Heart

Cardiovascular Physiology
Chapter 15
Cardiovascular System
Functions:
• Transports materials absorbed from the GIT
• Circulates O2 / CO2
• Distributes hormones
• Transports other compounds, cell products, wastes,
nutrients....
• Important in the body’s defense
• Essential in regulation of body temperature and
homeostasis
The Cardiovascular System is
Composed of
 Blood
 Heart
 Blood Vessels
arteries, arterioles, capillaries
venules, and veins
• Double pump
• Primarily cardiac muscle
• About the side of a fist
Heart
External Heart Anatomy
The Coronary circulation
supplies the heart cells.
Coronary Arteries are
supplied from the base of
the aorta during diastole
Cardiac veins empty into
the coronary sinus and
then into the right atrium
The Heart
• Major portion of the heart, myocardium, consists
largely of cardiac muscle
Wall of the Heart
•Epicardium (visceral pericardium)
•Myocardium (cardiac muscle)
•Endocardium ( epithelial and connective tissue)
The Heart
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Mammals have a four chambered heart
Two atria and two ventricles.
Right side of the heart pumps blood to the lungs
Left side pumps blood to the tissues
Closed circulatory system
Passage of Blood through the Heart
• Deoxygenated blood does not mix with oxygen-rich
blood.
• Blood must go through the lungs to pass from right
side to left side of the heart.
• Right ventricle sends blood through lungs.
Pulmonary circulation
• Left ventricle sends blood throughout the body.
Systemic circulation
Systemic and Pulmonary Circulation
Blood flow through the heart
Two pathways
http://www.youtube.com/watch?v=Rj_qD0SEGGk
Blood Vessels
•Arteries and arterioles
carry blood away from
the heart
•Capillaries are the site
of gas and nutrient
exchange
•Veins and venules
carry blood back to the
heart
Aorta/major arteries
• Stiff and springy
• Elastic layer (elastin) allows for elastic recoil
Abdominal aortic aneurysm (AAA)
• > 90% are/have been smokers
• Distends aorta
• Why?
Artery
Thick walls
Connective tissue and
smooth muscle
Arteriole
• Less elastic, some smooth muscle fibers
Capillaries
• Smallest diameter blood vessels
• Exchange of material with tissues
• Capillary beds are present in all regions of the body.
• Walls are endothelium only
• Semipermeable
Exchange at the capillaries
• Most cells within 0.1 mm of a capillary
• 50,000 miles of capillaries
• More metabolic, more capillaries
Metarterioles
• Can redirect blood flow
Why?
Exchange in the Capillaries
Venous system
• Venules- smallest, similar to capillaries except show
convergence
• Veins- more numerous than arteries, larger diameter, hold
more blood, blood reservoir
• Closer to surface of body (arm hanging)
Blood Volumes in Vessels
Venous valves
The movement of blood through the veins is
not dependent on cardiac contraction
Excellent
Summary
Slide
The Heartbeat
Each heartbeat is referred to as a cardiac
cycle.
– Systole - Contraction of heart muscle
– Diastole - Relaxation of heart muscle
Electrical conductance that causes contraction
of the heart
Atrial fibrillation
• Uncoordinated activity of contractile cells in atria
• Blood still gets into ventricles
• Some stays on walls of atria, clot can dislodge, stroke
Ventricular fibrillation
• Uncoordinated activity of contractile cells in
ventricles
• Doesn’t pump enough blood out
• Death
Electrocardiogram (ECG)
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Reflects electrical activity in the heart
Sum of all action potentials occurring in the heart
Waves- deflections from baseline
Segments- between two waves
Interval- waves and segments
Major components of an ECG
Regulation of Cardiac Cycle
• Physical exercise
• Body temperature
• Concentration of various ions
potassium
calcium
• Parasympathetic impulses decrease heart action
• Sympathetic impulses increase heart action
• Cardiac center regulates autonomic impulses to the heart
Regulation of Cardiac Cycle
Autonomic nerve impulses alter the
activities of the S-A and A-V nodes
Extrinsic Control of Heartbeat
• Cardiac control center in the medulla
oblongata can alter the beat of the heart
by way of the autonomic system
– Parasympathetic system
– Sympathetic system
• Hormones epinephrine and
norepinephrine are released by the
adrenal medulla and also stimulate the
heart
Blood pressure
• Heart pumping causes blood pressure
• Pressure without volume change
Arterial Blood Pressure
Blood Pressure – force the blood exerts against the inner
walls of the blood vessels
Arterial Blood Pressure
rises when ventricles contract
falls when ventricles relax
systolic pressure – maximum pressure
diastolic pressure – minimum pressure
Freq. written as a fraction 120/60
systolic 120 mm Hg, diastolic 60 mm Hg
Measuring Blood Pressure with a
Sphygmomanometer
Factors That Influence
Arterial Blood Pressure
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Blood volume
increases
Heart rate
increases
Stroke volume
increases
Blood pressure increases
Blood viscosity
increases
Peripheral resistance
increases
46
Cardiac output
• Regulated by mechanical, neural and
chemical factors
• Equal to heart rate X stroke volume
• Example pt with a pulse of 72
72 beats/min X 70 ml= 5,040 ml
Control of Blood Pressure
• Blood
pressure (BP) is determined by cardiac
output (CO) and peripheral resistance (PR)
BP = CO x PR
• Homeostasis requires regulation of CO and PR
https://www.youtube.com/watch?v=X9ZZ6t
cxArI&index=25&list=PL8dPuuaLjXtOAKed
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Dysfunction/disorders/disease of
the cardiovascular system
• Disorders of the heart and blood vessels
account for more than half of all deaths in the
US
• Coronary heart disease is involved in majority
of deaths
A few terms, just for fun!
• Tachycardia- increased heart rate (adults >100
bpm)
• Bradycardia- slow heart rate (adults <60 bpm)
• Atherosclerosis- hardening of the arteries
• Arrhythmia- irregular heart rhythm
• Angina- chest pain
• Aneurysm- localized bulge in the wall of a blood
vessel
• Thrombosis- blood clot
Heart attack
• Myocardial infarction- heart tissue death
• Can cause arrhythmias
Orthostatic Hypotension
• Decrease in blood pressure upon standing
• Blood evenly distributed, pools upon standing
• Decrease in venous return and bp, compensate with
increased cardiac output, peripheral resistance, MAP
Moon face
Syncope (fainting)
• Vasovagal- body overreacts to certain stimuli (blood,
needles, emotional stress), drop in heart rate and
blood pressure
• Ground parade- standing too long, blood in legs
doesn’t return to heart
Coronary heart disease
• Atherosclerosis, prevents blood flow to heart
• Thrombosis
• Blood supply to parts of the heart is severely
decreased or stops completely
Hypertension
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Chronically elevated BP
Inherited, for the most part
Baroreceptors adapt, consider high BP normal
Damages lining of blood vessels
(atherosclerotic plaques)
Hypertension
• Heart attempts to compensate but can’t
• Blood flow decreases, fluid in lungs (pulmonary
edema)
• Positive feedback: lack of oxygen weakens heart even
more
• Leads to congestive heart failure