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The Heart and Cardiovascular systemMuse 2440 Lecture #2 1/19/11
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Overview of today’s lesson
- Blood flow thru the heart- Conduction system (SA and AV nodes- Cardiac cycle- Hormone control of heart- Innervation control of heart- Stroke volume control- Blood vessels- Cardiovascular pathologies
Introduction to Cardiovascular System
The Pulmonary Circuit
Carries blood to and from gas exchange surfaces of
lungs
The Systemic Circuit
Carries blood to and from the body
Blood alternates between pulmonary circuit and
systemic circuit
Introduction to Cardiovascular System
Three Types of Blood Vessels
Arteries
Carry blood away from heart
Veins
Carry blood to heart
Capillaries
Networks between arteries and veins
Exchange materials between blood and tissues
Introduction to Cardiovascular System
Figure 20–1 An Overview of the Cardiovascular System.
Introduction to Cardiovascular System
Four Chambers of the Heart
Right atrium
Collects blood from systemic circuit
Right ventricle
Pumps blood to pulmonary circuit
Left atrium
Collects blood from pulmonary circuit
Left ventricle
Pumps blood to systemic circuit
Anatomy of the Heart
Figure 20–3b The Superficial Anatomy of the Heart
Figure 20–2c
Anatomy of the Heart
The Pericardium
Double lining of the pericardial cavity
Parietal pericardium
Outer layer
Forms inner layer of pericardial sac
Visceral pericardium
Inner layer of pericardium
Anatomy of the Heart
The Pericardium
Pericardial cavity
Is between parietal and visceral layers
Contains pericardial fluid
Pericardial sac
Fibrous tissue
Surrounds and stabilizes heart
Anatomy of the Heart
Figure 20–2b The Location of the Heart in the Thoracic Cavity
Anatomy of the Heart
Superficial Anatomy of the Heart
Atria
Thin-walled
Expandable outer auricle (atrial appendage)
rt auricle has some endocrine function
Sulci
Coronary sulcus: divides atria and ventricles
Anterior interventricular sulcus and posterior interventricular
sulcus:
– separate left and right ventricles
– contain blood vessels of cardiac muscle
Anatomy of the Heart
Figure 20–3a The Superficial Anatomy of the Heart
Blood flow through the heart
Deoxygenated blood enters right atrium from superior vena cava,passes from rt. atrium into rt ventricle thru the tricuspid valve. Getspumped out of right ventricle into pulmonary artery to go to lungs. Backflow is prevented by semilunar valves. Oxygenated blood returns from lungs through pulmonary veins and enters left atrium.The blood flows into the left ventricle through the mitral (bicuspid) valve. From the left ventricle, it is pumped into the aorta and out to the body.
Remember: left-leaves
Anatomy of the Heart
Figure 20–3a The Superficial Anatomy of the Heart
Anatomy of the Heart
The Heart Wall Epicardium (outer layer)
Visceral pericardium
Covers the heart
Myocardium (middle layer) Muscular wall of the heart
Concentric layers of cardiac muscle tissue
Atrial myocardium wraps around great vessels
Two divisions of ventricular myocardium
Endocardium (inner layer) Simple squamous epithelium
Anatomy of the Heart
Figure 20–4 The Heart Wall
Anatomy of the Heart
Cardiac Muscle Tissue
Intercalated discs
Interconnect cardiac muscle cells
Secured by desmosomes
Linked by gap junctions
Convey force of contraction
Propagate action potentials
Anatomy of the Heart
Figure 20–5 Cardiac Muscle Cells
Anatomy of the Heart
Figure 20–5 Cardiac Muscle Cells
Anatomy of the Heart
Figure 20–5 Cardiac Muscle Cells
Anatomy of the Heart
Figure 20–6a-b The Sectional Anatomy of the Heart.
Anatomy of the Heart
Figure 20–6a-b The Sectional Anatomy of the Heart.
Anatomy of the Heart
The Right Ventricle Free edges attach to chordae tendineae
from papillary muscles of ventricle
Prevent valve from opening backward
Right atrioventricular (AV) Valve Also called tricuspid valve
Opening from right atrium to right ventricle
Has three cusps
Prevents backflow
Anatomy of the Heart
The Right Ventricle
Trabeculae carneae
Muscular ridges on internal surface of right (and
left) ventricle
Includes moderator band:
– ridge contains part of conducting system
– coordinates contractions of cardiac muscle cells
Anatomy of the Heart
The Pulmonary Circuit
Conus arteriosus (superior end of right ventricle)
leads to pulmonary trunk
Pulmonary trunk divides into left and right
pulmonary arteries
Blood flows from right ventricle to pulmonary trunk
through pulmonary valve
Pulmonary valve has three semilunar cusps
Anatomy of the Heart
The Left Atrium
Blood gathers into left and right pulmonary
veins
Pulmonary veins deliver to left atrium
Blood from left atrium passes to left ventricle
through left atrioventricular (AV) valve
A two-cusped bicuspid valve or mitral valve
Anatomy of the Heart
The Left Ventricle Holds same volume as right ventricle
Is larger; muscle is thicker and more powerful
Similar internally to right ventricle but does not have
moderator band
Systemic circulation Blood leaves left ventricle through aortic valve into
ascending aorta
Ascending aorta turns (aortic arch) and becomes
descending aorta
Anatomy of the Heart
Figure 20–6c The Sectional Anatomy of the Heart.
Anatomy of the Heart
Figure 20–7 Structural Differences between the Left and Right Ventricles
Anatomy of the Heart
The Heart Valves
Two pairs of one-way valves prevent backflow
during contraction
Atrioventricular (AV) valves
Between atria and ventricles
Blood pressure closes valve cusps during ventricular
contraction
Papillary muscles tense chordae tendineae: prevent valves
from swinging into atria
Figure 20–8
Anatomy of the Heart
The Heart Valves
Semilunar valves
Pulmonary and aortic tricuspid valves
Prevent backflow from pulmonary trunk and aorta
into ventricles
Have no muscular support
Three cusps support like tripod
Figure 20–8
Anatomy of the Heart
Aortic Sinuses
At base of ascending aorta
Sacs that prevent valve cusps from sticking to
aorta
Origin of right and left coronary arteries
Anatomy of the Heart
Figure 20–8a Valves of the Heart
Anatomy of the Heart
Figure 20–8b Valves of the Heart
Anatomy of the Heart
Figure 20–8c Valves of the Heart
Anatomy of the Heart
The Coronary Arteries
Left and right
Originate at aortic sinuses
High blood pressure, elastic rebound forces
blood through coronary arteries between
contractions
Anatomy of the Heart
Right Coronary Artery
Supplies blood to
Right atrium
Portions of both ventricles
Cells of sinoatrial (SA) and atrioventricular nodes
Marginal arteries (surface of right ventricle)
Posterior interventricular artery
Anatomy of the Heart
Left Coronary Artery
Supplies blood to
Left ventricle
Left atrium
Interventricular septum
Anatomy of the Heart
Two main branches of left coronary artery
Circumflex artery
Anterior interventricular artery
Arterial Anastomoses
Interconnect anterior and posterior interventricular
arteries
Stabilize blood supply to cardiac muscle
Anatomy of the Heart
The Cardiac Veins
Great cardiac vein
Drains blood from area of anterior interventricular artery into
coronary sinus
Anterior cardiac veins
Empties into right atrium
Posterior cardiac vein, middle cardiac vein, and
small cardiac vein
Empty into great cardiac vein or coronary sinus
Anatomy of the Heart
Figure 20–9a Coronary Circulation
Anatomy of the Heart
Figure 20–9b Coronary Circulation
Anatomy of the Heart
Figure 20–9c Coronary Circulation
Anatomy of the Heart
Figure 20–10 Coronary Circulation and Clinical Testing
The Conducting System
The Cardiac Cycle
Begins with action potential at SA node
Transmitted through conducting system
Produces action potentials in cardiac muscle cells
(contractile cells)
Electrocardiogram (ECG)
Electrical events in the cardiac cycle can be recorded on an
electrocardiogram (ECG)
The Conducting System
Figure 20–11 An Overview of Cardiac Physiology
The Conducting System
A system of specialized cardiac muscle
cells
Initiates and distributes electrical impulses
that stimulate contraction
Automaticity
Cardiac muscle tissue contracts automatically
The Conducting System
Structures of the Conducting System
Sinoatrial (SA) node - wall of right atrium
Atrioventricular (AV) node - junction
between atria and ventricles
Conducting cells - throughout myocardium
The Conducting System
Prepotential
Also called pacemaker potential
Resting potential of conducting cells
Gradually depolarizes toward threshold
SA node depolarizes first, establishing heart
rate
The Conducting System
Figure 20–12 The Conducting System of the Heart
The Conducting System
Heart Rate
SA node generates 80–100 action potentials
per minute
Parasympathetic stimulation slows heart rate
AV node generates 40–60 action potentials
per minute
The Conducting System
The Sinoatrial (SA) Node
In posterior wall of right atrium
Contains pacemaker cells
Connected to AV node by internodal pathways
Begins atrial activation (Step 1)
The Conducting System
Figure 20–13 Impulse Conduction through the Heart
The Conducting System
The Atrioventricular (AV) Node
In floor of right atrium
Receives impulse from SA node (Step 2)
Delays impulse (Step 3)
Atrial contraction begins
The Conducting System
Figure 20–13 Impulse Conduction through the Heart
The Conducting System
Figure 20–13 Impulse Conduction through the Heart
The Conducting System
The AV Bundle
In the septum
Carries impulse to left and right bundle
branches
Which conduct to Purkinje fibers (Step 4)
And to the moderator band
Which conducts to papillary muscles
The Conducting System
Figure 20–13 Impulse Conduction through the Heart
The Conducting System
Purkinje Fibers
Distribute impulse through ventricles (Step 5)
Atrial contraction is completed
Ventricular contraction begins
The Conducting System
Figure 20–13 Impulse Conduction through the Heart
The Conducting System
Abnormal Pacemaker Function
Bradycardia: abnormally slow heart rate
Tachycardia: abnormally fast heart rate
Ectopic pacemaker
Abnormal cells
Generate high rate of action potentials
Bypass conducting system
Disrupt ventricular contractions
The Conducting System
Electrocardiogram (ECG or EKG)
A recording of electrical events in the heart
Obtained by electrodes at specific body
locations
Abnormal patterns diagnose damage
The Conducting System
Figure 20–14b An Electrocardiogram: An ECG Printout
The Conducting System
Time Intervals Between ECG Waves
P–R interval
From start of atrial depolarization
To start of QRS complex
Q–T interval
From ventricular depolarization
To ventricular repolarization
The Conducting System
Figure 20–14a An Electrocardiogram: Electrode Placement for Recording a Standard ECG
The Conducting System
Figure 20–14b An Electrocardiogram: An ECG Printout
The Conducting System
Contractile Cells
Purkinje fibers distribute the stimulus to the
contractile cells, which make up most of the
muscle cells in the heart
Resting Potential
Of a ventricular cell: about –90 mV
Of an atrial cell: about –80 mV
The Conducting System
Figure 20–15 The Action Potential in Skeletal and Cardiac Muscle
The Conducting System
Refractory Period
Absolute refractory period
Long
Cardiac muscle cells cannot respond
Relative refractory period
Short
Response depends on degree of stimulus
The Conducting System
Timing of Refractory Periods
Length of cardiac action potential in
ventricular cell
250–300 msecs:
– 30 times longer than skeletal muscle fiber
– long refractory period prevents summation and tetany
The Conducting System
The Role of Calcium Ions in Cardiac
Contractions
Contraction of a cardiac muscle cell is
produced by an increase in calcium ion
concentration around myofibrils
The Conducting System
The Energy for Cardiac Contractions
Aerobic energy of heart
From mitochondrial breakdown of fatty acids and
glucose
Oxygen from circulating hemoglobin
Cardiac muscles store oxygen in myoglobin
The Cardiac Cycle
Phases of the Cardiac Cycle
Within any one chamber
Systole (contraction)
Diastole (relaxation)
The Cardiac Cycle
Figure 20–16 Phases of the Cardiac Cycle
The Cardiac Cycle
Blood Pressure
In any chamber
Rises during systole (ventricular compression) 120
Falls during diastole (vessel elasticity) 60
Blood flows from high to low pressure
Controlled by timing of contractions
Directed by one-way valves - not perfect seals
The Cardiac Cycle
Cardiac Cycle and Heart Rate
At 75 beats per minute
Cardiac cycle lasts about 800 msecs
When heart rate increases
All phases of cardiac cycle shorten, particularly
diastole
The Cardiac Cycle
Figure 20–17 Pressure and Volume Relationships in the Cardiac Cycle
The Cardiac Cycle
Heart Sounds
S1
Loud sounds Lub
Produced by AV valves
S2
Loud sounds Dub
Produced by semilunar valves
S3, S4
Soft sounds often missed
Blood flow into ventricles and atrial contraction
The Cardiac Cycle
Heart Murmur
Sounds produced by regurgitation through
valves
Example - mitral valve prolapse
The Cardiac Cycle
Figure 20–18 Heart Sounds
Cardiodynamics
Cardiac Output
CO = HR X SV
CO = cardiac output (mL/min)
HR = heart rate (beats/min)
SV = stroke volume (mL/beat)
Cardiodynamics
Factors Affecting Cardiac Output
Cardiac output
Adjusted by changes in heart rate or stroke volume
Heart rate
Adjusted by autonomic nervous system or hormones
Stroke volume
Adjusted by changing EDV or ESV
Cardiodynamics
Factors Affecting the Heart Rate
Autonomic innervation
Cardiac plexuses: innervate heart
Vagus nerves (X): carry parasympathetic preganglionic fibers
to small ganglia in cardiac plexus
Cardiac centers of medulla oblongata:
– cardioacceleratory center controls sympathetic
neurons (increases heart rate)
– cardioinhibitory center controls parasympathetic
neurons (slows heart rate)
Cardiodynamics
Autonomic Innervation Cardiac reflexes
Cardiac centers monitor:– blood pressure (baroreceptors)– arterial oxygen and carbon dioxide levels
(chemoreceptors)
Cardiac centers adjust cardiac activity Autonomic tone
Dual innervation maintains resting tone by releasing ACh and NE
Fine adjustments meet needs of other systems
Cardiodynamics
Figure 20–21 Autonomic Innervation of the Heart
Cardiodynamics
Effects on the SA Node Sympathetic and parasympathetic stimulation
Greatest at SA node (heart rate)
Membrane potential of pacemaker cells Lower than other cardiac cells
Rate of spontaneous depolarization depends on Resting membrane potential Rate of depolarization
ACh (parasympathetic stimulation) Slows the heart
NE (sympathetic stimulation) Speeds the heart
Cardiodynamics
Figure 20–22 Autonomic Regulation of Pacemaker Function
Cardiodynamics
Hormonal Effects on Heart Rate
Increase heart rate (by sympathetic
stimulation of SA node)
Epinephrine (E)
Norepinephrine (NE)
Thyroid hormone
Cardiodynamics
Factors Affecting the Stroke Volume
The EDV: amount of blood a ventricle contains at the
end of diastole
Filling time:
– duration of ventricular diastole
Venous return:
– rate of blood flow during ventricular diastole
Cardiodynamics
The Frank–Starling Principle
As EDV increases, stroke volume increases
Physical Limits
Ventricular expansion is limited by
Myocardial connective tissue
The cardiac (fibrous) skeleton
The pericardial sac
Cardiodynamics
End-Systolic Volume (ESV)
The amount of blood that remains in the
ventricle at the end of ventricular systole is
the ESV
Cardiodynamics
Effects of Autonomic Activity on Contractility
Sympathetic stimulation
NE released by postganglionic fibers of cardiac nerves
Epinephrine and NE released by suprarenal (adrenal)
medullae
Causes ventricles to contract with more force
Increases ejection fraction and decreases ESV
Cardiodynamics
Effects of Autonomic Activity on
Contractility
Parasympathetic activity
Acetylcholine released by vagus nerves
Reduces force of cardiac contractions
Cardiodynamics
Hormones
Many hormones affect heart contraction
Pharmaceutical drugs mimic hormone actions
Stimulate or block beta receptors
Affect calcium ions (e.g., calcium channel
blockers)
Cardiodynamics
Heart Rate Control Factors
Autonomic nervous system
Sympathetic and parasympathetic
Circulating hormones
Venous return and stretch receptors
Cardiac Reserve
The difference between resting and maximal cardiac output
Classes of Blood Vessels
Arteries Carry blood away from heart
Arterioles Are smallest branches of arteries
Capillaries Are smallest blood vessels
Location of exchange between blood and interstitial fluid
Venules Collect blood from capillaries
Veins Return blood to heart
Blood Vessels
The Largest Blood Vessels
Attach to heart
Pulmonary trunk
Carries blood from right ventricle
To pulmonary circulation
Aorta
Carries blood from left ventricle
To systemic circulation
Blood Vessels
The Smallest Blood Vessels
Capillaries
Have small diameter and thin walls
Chemicals and gases diffuse across walls
Blood Vessels
The Structure of Vessel Walls
Walls have three layers:
Tunica intima
Tunica media
Tunica externa
Blood Vessels
The Tunica Intima
Is the innermost layer
Includes
The endothelial lining
Connective tissue layer
Internal elastic membrane:
– in arteries, is a layer of elastic fibers in outer margin of
tunica intima
Blood Vessels
The Tunica Media
Is the middle layer
Contains concentric sheets of smooth muscle in loose
connective tissue
Binds to inner and outer layers
External elastic membrane of the tunica media
Separates tunica media from tunica externa
Blood Vessels
The Tunica Externa Is outer layer Contains connective tissue sheath Anchors vessel to adjacent tissues in arteries
Contain collagen Elastic fibers
In veins Contains elastic fibers Smooth muscle cells
Vasa vasorum (“vessels of vessels”) Small arteries and veins In walls of large arteries and veins Supply cells of tunica media and tunica externa
Blood Vessels
Figure 21–1 Comparisons of a Typical Artery and a Typical Vein.
Blood Vessels
Differences between Arteries and Veins Arteries and veins run side by side
Arteries have thicker walls and higher blood pressure
Collapsed artery has small, round lumen (internal
space)
Vein has a large, flat lumen
Vein lining contracts, artery lining does not
Artery lining folds
Arteries more elastic
Veins have valves
Structure and Function of Arteries
Arteries and Pressure Elasticity allows arteries to absorb pressure waves
that come with each heartbeat
Contractility Arteries change diameter
Controlled by sympathetic division of ANS
Vasoconstriction:
– the contraction of arterial smooth muscle by the ANS
Vasodilatation:
– the relaxation of arterial smooth muscle
– enlarging the lumen
Structure and Function of Arteries
Vasoconstriction and Vasodilation
Affect
Afterload on heart
Peripheral blood pressure
Capillary blood flow
Structure and Function of Arteries
Arteries
From heart to capillaries, arteries change
From elastic arteries
To muscular arteries
To arterioles
Structure and Function of Arteries
Elastic Arteries
Also called conducting arteries
Large vessels (e.g., pulmonary trunk and
aorta)
Tunica media has many elastic fibers and few
muscle cells
Elasticity evens out pulse force
Structure and Function of Arteries
Muscular Arteries
Also called distribution arteries
Are medium sized (most arteries)
Tunica media has many muscle cells
Structure and Function of Arteries
Arterioles Are small
Have little or no tunica externa
Have thin or incomplete tunica media
Artery Diameter Small muscular arteries and arterioles
Change with sympathetic or endocrine stimulation
Constricted arteries oppose blood flow
– resistance (R):
» resistance vessels: arterioles
Structure and Function of Arteries
Aneurysm
A bulge in an arterial wall
Is caused by weak spot in elastic fibers
Pressure may rupture vessel
Structure and Function of Arteries
Figure 21–2 Histological Structure of Blood Vessels
Structure and Function of Arteries
Figure 21–3 A Plaque within an Artery
Structure and Function of Capillaries
Capillaries
Are smallest vessels with thin walls
Microscopic capillary networks permeate all active
tissues
Capillary function
Location of all exchange functions of cardiovascular system
Materials diffuse between blood and interstitial fluid
Structure and Function of Capillaries
Capillary Structure
Endothelial tube, inside thin basal lamina
No tunica media
No tunica externa
Diameter is similar to red blood cell
Structure and Function of Capillaries
Continuous Capillaries
Have complete endothelial lining
Are found in all tissues except epithelia and
cartilage
Functions of continuous capillaries
Permit diffusion of water, small solutes, and lipid-
soluble materials
Block blood cells and plasma proteins
Structure and Function of Capillaries
Specialized Continuous Capillaries
Are in CNS and thymus
Have very restricted permeability
For example, the blood–brain barrier
Structure and Function of Capillaries
Fenestrated Capillaries
Have pores in endothelial lining
Permit rapid exchange of water and larger solutes
between plasma and interstitial fluid
Are found in
Choroid plexus
Endocrine organs
Kidneys
Intestinal tract
Structure and Function of Capillaries
Sinusoids (sinusoidal capillaries) Have gaps between adjacent endothelial cells
Liver Spleen Bone marrow Endocrine organs
Permit free exchange Of water and large plasma proteins Between blood and interstitial fluid
Phagocytic cells monitor blood at sinusoids
Structure and Function of Capillaries
Figure 21–4 Capillary Structure
Structure and Function of Capillaries
Figure 21–4 Capillary Structure
Structure and Function of Capillaries
Arteriovenous Anastomoses
Direct connections between arterioles and
venules
Bypass the capillary bed
Structure and Function of Capillaries
Capillary Sphincter
Guards entrance to each capillary
Opens and closes, causing capillary blood to
flow in pulses
Structure and Function of Capillaries
Vasomotion
Contraction and relaxation cycle of capillary
sphincters
Causes blood flow in capillary beds to
constantly change routes
Structure and Function of Veins
Veins
Collect blood from capillaries in tissues and organs
Return blood to heart
Are larger in diameter than arteries
Have thinner walls than arteries
Have lower blood pressure
Structure and Function of Veins
Vein Categories
Venules Very small veins Collect blood from capillaries
Medium-sized veins Thin tunica media and few smooth muscle cells Tunica externa with longitudinal bundles of elastic fibers
Large veins Have all three tunica layers Thick tunica externa Thin tunica media
Structure and Function of Veins
Venous Valves
Folds of tunica intima
Prevent blood from flowing backward
Compression pushes blood toward heart
Structure and Function of Veins
Figure 21–6 The Function of Valves in the Venous System
Blood Vessels
The Distribution of Blood
Heart, arteries, and capillaries
30–35% of blood volume
Venous system
60–65%:
– 1/3 of venous blood is in the large venous networks of the liver,
bone marrow, and skin
Blood Vessels
Figure 21–7 The Distribution of Blood in the CardiovascularSystem
Blood Vessels
Capacitance of a Blood Vessel
The ability to stretch
Relationship between blood volume and blood
pressure
Veins (capacitance vessels) stretch more
than arteries
Blood Vessels
Venous Response to Blood Loss
Vasomotor centers stimulate sympathetic
nerves
Systemic veins constrict (venoconstriction)
Veins in liver, skin, and lungs redistribute venous
reserve
Pressure and Resistance
Pressure (P)
The heart generates P to overcome resistance
Absolute pressure is less important than pressure
gradient
The Pressure Gradient (P)
Circulatory pressure = pressure gradient
The difference between
Pressure at the heart
And pressure at peripheral capillary beds
Pressure and Resistance
Force (F)
Is proportional to the pressure difference (P)
Divided by R
Pressure and Resistance
Measuring Pressure
Blood pressure (BP)
Arterial pressure (mm Hg)
Capillary hydrostatic pressure (CHP)
Pressure within the capillary beds
Venous pressure
Pressure in the venous system
Pressure and Resistance
Turbulence
Swirling action that disturbs smooth flow of
liquid
Occurs in heart chambers and great vessels
Atherosclerotic plaques cause abnormal
turbulence
Pressure and Resistance
Figure 21–12 Forces Acting across Capillary Walls
Pressure and Resistance
Fluid Recycling Water continuously moves out of capillaries, and back
into bloodstream via the lymphoid system and serves
to Ensure constant plasma and interstitial fluid communication
Accelerate distribution of nutrients, hormones, and dissolved
gases through tissues
Transport insoluble lipids and tissue proteins that cannot
cross capillary walls
Flush bacterial toxins and chemicals to immune system
tissues
Cardiovascular Regulation
Figure 21–13 Short-Term and Long-Term Cardiovascular Responses
Cardiovascular Regulation
Reflex Control of Cardiovascular Function
Cardiovascular centers monitor arterial blood
Baroreceptor reflexes:
– respond to changes in blood pressure
Chemoreceptor reflexes:
– respond to changes in chemical composition, particularly
pH and dissolved gases
Cardiovascular Regulation
Baroreceptor Reflexes Stretch receptors in walls of
Carotid sinuses: maintain blood flow to brain
Aortic sinuses: monitor start of systemic circuit
Right atrium: monitors end of systemic circuit
When blood pressure rises, CV centers Decrease cardiac output
Cause peripheral vasodilation
When blood pressure falls, CV centers Increase cardiac output
Cause peripheral vasoconstriction
Cardiovascular Regulation
Figure 21–14 Baroreceptor Reflexes of the Carotid and Aortic Sinuses
Cardiovascular Regulation
Hormones and Cardiovascular Regulation
Hormones have short-term and long-term
effects on cardiovascular regulation
For example, E and NE from suprarenal
medullae stimulate cardiac output and
peripheral vasoconstriction
Cardiovascular Regulation
Antidiuretic Hormone (ADH)
Released by neurohypophysis (posterior lobe of
pituitary)
Elevates blood pressure
Reduces water loss at kidneys
ADH responds to
Low blood volume
High plasma osmotic concentration
Circulating angiotensin II
Cardiovascular Regulation
Angiotensin II
Responds to fall in renal blood pressure
Stimulates
Aldosterone production
ADH production
Thirst
Cardiac output
Peripheral vasoconstriction
Cardiovascular Regulation
Erythropoietin (EPO)
Released at kidneys
Responds to low blood pressure, low O2
content in blood
Stimulates red blood cell production
Cardiovascular Regulation
Natriuretic Peptides
Atrial natriuretic peptide (ANP)
Produced by cells in right atrium
Brain natriuretic peptide (BNP)
Produced by ventricular muscle cells
Respond to excessive diastolic stretching
Lower blood volume and blood pressure
Reduce stress on heart
Cardiovascular Regulation
Figure 21–16a The Hormonal Regulation of Blood Pressure and Blood Volume.
Cardiovascular Regulation
Figure 21–16b The Hormonal Regulation of Blood Pressure and Blood Volume.
Cardiovascular Adaptation
The Cardiovascular Response to Exercise
Light exercise Extensive vasodilation occurs:
– increasing circulation
Venous return increases:
– with muscle contractions
Cardiac output rises:
– due to rise in venous return (Frank–Starling principle)
and atrial stretching
Cardiovascular Adaptation
The Cardiovascular Response to Exercise
Heavy exercise Activates sympathetic nervous system
Cardiac output increases to maximum:
– about four times resting level
Restricts blood flow to “nonessential” organs (e.g., digestive system)
Redirects blood flow to skeletal muscles, lungs, and heart
Blood supply to brain is unaffected
Cardiovascular Adaptation
Cardiovascular Adaptation
Short-Term Elevation of Blood Pressure
Carotid and aortic reflexes
Increase cardiac output (increasing heart rate)
Cause peripheral vasoconstriction
Sympathetic nervous system
Triggers hypothalamus
Further constricts arterioles
Venoconstriction improves venous return
Cardiovascular Adaptation
Short-Term Elevation of Blood Pressure
Hormonal effects
Increase cardiac output
Increase peripheral vasoconstriction (E, NE,
ADH, angiotensin II)
Cardiovascular Adaptation
Long-Term Restoration of Blood Volume
Recall of fluids from interstitial spaces
Aldosterone and ADH promote fluid retention
and reabsorption
Thirst increases
Erythropoietin stimulates red blood cell
production
Cardiovascular Adaptation
Vascular Supply to Special Regions
Through organs with separate mechanisms to
control blood flow
Brain
Heart
Lungs
Cardiovascular Adaptation
Blood Flow to the Brain
Is top priority
Brain has high oxygen demand
When peripheral vessels constrict, cerebral
vessels dilate, normalizing blood flow
Cardiovascular Adaptation
Stroke
Also called cerebrovascular accident (CVA)
Blockage or rupture in a cerebral artery
Stops blood flow
Cardiovascular Adaptation
Heart Attack
A blockage of coronary blood flow
Can cause
Angina (chest pain)
Tissue damage
Heart failure
Death
Fetal and Maternal Circulation
Cardiovascular Changes at Birth Newborn breathes air
Lungs expand Pulmonary vessels expand
Reduced resistance allows blood flow
Rising O2 causes ductus arteriosus constriction
Rising left atrium pressure closes foramen ovale
Pulmonary circulation provides O2
Fetal and Maternal Circulation
Fetal Pulmonary Circulation Bypasses
• Foramen ovale: Interatrial opening
Covered by valve-like flap
Directs blood from right to left atrium
• Ductus arteriosus:
Short vessel
Connects pulmonary and aortic trunks
Fetal and Maternal Circulation
Figure 21–33a Fetal Circulation: Blood Flow to and from the Placenta
Fetal and Maternal Circulation
Figure 21–33b Fetal Circulation: Blood Flow Through the Neonatal Heart
Fetal and Maternal Circulation
Figure 21–34 Congenital Cardiovascular Problems
Aging and the Cardiovascular System
Cardiovascular capabilities decline with
age
Age-related changes occur in
Blood
Heart
Blood vessels
Aging and the Cardiovascular System
Three Age-Related Changes in Blood
Decreased hematocrit
Peripheral blockage by blood clot (thrombus)
Pooling of blood in legs
Due to venous valve deterioration
Aging and the Cardiovascular System
Five Age-Related Changes in the Heart
Reduced maximum cardiac output
Changes in nodal and conducting cells
Reduced elasticity of cardiac (fibrous) skeleton
Progressive atherosclerosis
Replacement of damaged cardiac muscle cells by
scar tissue
Aging and the Cardiovascular System
Three Age-Related Changes in Blood Vessels
Arteries become less elastic
Pressure change can cause aneurysm
Calcium deposits on vessel walls
Can cause stroke or infarction
Thrombi can form
At atherosclerotic plaques