Cardiovascular System and Physiology
ANATOMY
Heart
ü Hollow, muscular organ
» To accommodate blood
» Muscular since it acts as pump to draw in and out
blood
ü About the size of a fist
ü Weight – 250 – 300 g
» Females – 250 g
» Males – 300 g
ü Innervated by C3 – T4
ü Rotated sagittaly – (R) surface is more anterior than (L)
surface of the heart
ü 2/3 of the surface is located to the left
ü Coronary sinus – opening where blood from coronary
articulation drains into
ü Fossa Ovalis
» Scar tissue
» Adjacent to the coronary sinus
» Remnant of foramen ovale
§ Passageway from (R) atrium ® (L) atrium for
fetal circulation
§ Pulmonary circulation is by-passed
§ Found in fetal circulation ® will close upon birth
ü AV node
» Sends signals from atrium to ventricle
» Located at the distal part of (R) atrium
Right Ventricle
Internal Structures of the Heart
ü Apex
» Point of maximal impulse (PMI) – where pulse is heard
the loudest
» Located at 5th intercostal space in the midclavicular
line
§ Able to clinically estimate if patient has
cardiomegaly when PMI goes beyond 5th ICS
» Tilted downward, forward and to the left
» Primally composed of (L) ventricle
ü Base – comprised of (L) and (R) atrium (L > R)
Aorta
ü Largest artery
ü Passageway of blood from heart to the systemic circulation
ü Segments
» Ascending
» Arches
§ Brachiocephalic artery
o (R) Common carotid artery
o (R) Subclavian artery
§ (L) Common carotid artery
§ (L) Subclavian artery
» Descending
ü Ligamentum Arteriosus
» Scar tissue
» Remnant of ductus arteriosus
§ Closes within 2 weeks of life
» Support between the pulmonary trunk and aorta
Right Atrium
ü Opening of superior vena cava
ü SA node
» Located inferolateral surface to superior vena cava
» Pacemaker of the heart
ü Opening of pulmonic valve
ü Tricuspid Valve – has 3 cusps/leaflets
ü Chorda Tendinae
» "Heartstrings”
» Supports the cusps
» Held in position by papillary muscle
» Closed valves – chorda tendinae is taut, papillary
muscle is contracted
ü Trabecular Carnae – muscle that forms the ridges of
ventricles
ü Pectinate muscles – muscle that forms the ridges of atrium
ü Mitral/Bicuspid valve – valve that has 2 cusps/leaflets
located in left ventricle
LAYERS OF THE HEART
Pericardium
ü Protects and surrounds the whole heart
ü Ensures movement of the heart
ü Fibrous
» Inelastic, thin sheath of connective tissue
» Serves as an anchor
» Protects the heart
» Prevents overfilling – regulates blood flow
ü Parietal – extra protection
ü Visceral
» AKA epicardium
» Houses coronary vessels
ü Pericardial fluid
» Acts a lubrication for smooth movement
» ¯ PF – parietal wall meets visceral ® friction ®
pericarditis (chest pain)
Myocardium
ü Muscular layer
ü Responsible for the pumping action
ü (+) contractile cells
ü Interventricular septum
ü Interatrial septum - thinner walls than interventricular
septum
ü (L) myocardial wall is thicker and more contractile cells than
(R) due to high pressure and it pumps blood out of heart
Oxygenated blood
Lungs
Enters pulmary veins
Enters (L) atrium
Endocardium
ü
ü
ü
ü
Bicuspid valve opens
Thin layer of connective tissue
Smooth lining of heart chambers
Continues as the epithelial tissue of valves
Infective carditis – since endocardium continues as the
lining of valves ® dysfunctional valves
Blood enters (L) ventricle
Myocardial cells triggered
Blood passes thru aortic valve
Aorta
Systemic circulation
CARDIAC BLOOD FLOW
(R) side – pulmonary circulation
Artery away
Venous vacuum
(L) side – systemic circulation
Movement of blood – higher pressure ® lower pressure
Superior vena cava – drains blood from head, neck, and UE
Inferior vena cava
» Drains blood from trunk and LE
» Largest blood vessel
ü Coronary sinus
» Drains blood from the heart
» Where the posterior vein, middle vein, great cardiac
vein, and small cardiac vein meet
ü
ü
ü
ü
ü
Systemic Circulation
Deoxygenated blood
SVC, IVC and CS
Enters (R) atrium
¯ pressure in veins (SVC & IVC)
­ pressure in (R) atrium
Lax chorda tendinae & papillary muscle
Tricuspid valve opens
Blood pools into (R) ventricle
Blood enters pulmonary trunk
Blood is distributed to (R) & (L) pulmonary arteries
Lungs
Coronary Circulation
ü Aortic sinus
» (R) Coronary artery – supplies RA, RV, SA node and AV
node
» (L) Coronary artery – supplies LA, LV and
interventricular septum
Aortic Sinus
(R) Coronary
Artery
(R) Posterior
Descending/
Interventricular
Artery
Marginal
Artery
(L) Coronary
Artery
(L) Anterior
Descending/
Interventricular
Artery
(L)
Circumflex
Artery
ü Coronary sulcus
» Between atrium and ventricle
» Where coronary sinus is situated
ü Coronary sinus
» Gate where blood will enter
» SCV, MV, PV, GCV all go here
» Along with anterior vein, it drains into (R) atrium
» Posterior branch
§ Posterior vein – drains blood from posterior side
of heart
§ Small cardiac vein – drains blood from (R) side of
heart
§ Middle vein – drains blood from septum
Coronary
Sinus
Anterior Vein
Posterior
Branch
Small
Cardiac Vein
Posterior Vein
ü
Anterior
Branch
Middle Vein
Great Cardiac
Vein
ü Myocardial infarction
» AKA myocardial ischemia
» Blockage in one of the arteries which will occlude the
blood flow
» Ischemia – partial obstruction
» Infarction – total blockage
» Majority of MI is caused by (L) anterior descending
artery affectation
ü
ü
ü
» Time required for the impulse to travel from atrium to
conduction system
QRS wave
» Ventricular depolarization
» Ventricular contraction, atrial relaxation
» Atrial repolarization happens simultaneously
QT interval
» Time for ventricular systole
» Time for ventricular depolarization to repolarization
» 0.32 – 0.40 ms
elevaTION – infarcTION
ST segment
depresSion – iSchemia
» End of S, beginning of T
» Ventricular repolarization starts
» ST segment elevation ® myocardial infarction
» ST segment depression ® ischemia
T wave – ventricular repolarization
CONDUCTION PATHWAYS
ü SA node
» Pacemaker
» Responsible for automaticity
§ Ability of the heart to spontaneously generate its
own impulse or action potential
» Sinus rhythm – 60 – 100 bpm
» Ability to send impulses from RA ® LA
» Needs help of Bachman’s bundle which sends impulse
from (R) atrium to (L)
ü Internodal pathway – sends impulse from SA ® AV node
ü AV node
» Sinus rhythm – 40 – 60 bpm
» O.1 sec delay
§ Allow the atrium to contract before ventricle
§ Essential to promote ventricular filling before
ventricular contraction
» Structure
§ Lesser gap junctions ® slower conduction
§ Small diameter of fibers ® slower conduction
ü Bundle of His
» AKA AV bundle
» Divides into (R) and (L) bundle branches ® Purkinje
fibers (35 bpm)
ü Latent pacemaker – can function for SA node
SA node
Bachman's
bundle
Internodal
pathway
(R) & (L) bundle
branches
Bundle of His
AV node
Purkinje fibers
Ventricles
ELECTROCARDIOGRAM
ü P wave
» Atrial depolarixation
» Time both atrium contract for blood to move into
ventricle
ü PR interval
» Start of P, end of Q
» 0.12 – 0.20 ms
INTRINSIC CONDUCTION
ü Gap junctions
» Allows transport of ions, molecules and impulses from
one cell to another
» Formed by connexons – allows bi-directional flow
ü Desmosome – intercellular junction which promotes strong
adhesion between 2 cells
ü Intercallated disc (ICD) – gap junctions + desmosome
ü T-tubules
» Invagination in contractile cells
» Has a lot of L-type Ca+ cells
» Should be in proximity with sarcoplasmic reticulum
ü Ryanodine receptor – opens channel so that Ca+ ions from
SR ® sarcolemma
ü Tropomyosin – covers actin to prevent contraction
Contractile Cell Action Potential
ü Contractile cells
» Actin, myosin, tropomyosin, troponin
» RMP – -90 mV
ü Phase 0
» Upstroke
» Due to entry of Na+ ions
ü Phase 1
» Initial repolarization
» Efflux of K+ due to opening of K-channels
ü Phase 2
» Plateau
» L-type Ca+ and K+ are open simultaneously
ü Phase 3
» Repolarization
» Due to efflux of K+ ions
ü Phase 4 – resting membrane potential
Nodal Cells
Nodal Cells Action Potential
ü Nodal cells
» SA node, AV node, bundle of His and Purkinje fibers
» Unstable resting membrane potential – -50 – -60 mV
ü Phase 0
» Upstroke
» Due to entry of Ca+ ions
ü Phase 3 – repolarization
ü Phase 4 – resting membrane potential
Funny Na+
channels open
(-55 mV)
SA node is
stimulated
T-type Ca+
channels open
40 mV)
Ca+ ions form Ltype Ca+
channels sent to
contractile cell via
gap junctions
L-type Ca+
channels open
(40 mV)
L-type Ca+
channels open (10
mV)
K+ channels open
(initial
repolarization)
Plateau
CCC binds wiht
Ryanodine
receptor
Ca binds to a
protein in SR
(forms CaCalmodulin
complex)
T-tubules open
which inceases
Ca+ ions in
sarcolemma
CCC induces Ca+
release from SR
Ca+ binds with
Troponin C
Tropomyosin
unwinds
Voltage-gated Na+
channels open
(upstroke) (0 mV)
Powerstroke
Crossbridge
Actin head is
exposed
EXTRINSIC CONDUCTION
Epinephrine
binds to beta1 adrenergic
receptor
Activates Gstimulatory
protein
Adenylate
Cyclase is
activated
Catalyze ATP
into cyclic
AMP
Voltage-gated
Na+
channels
open
(upstroke)
Ca+ ions is
sent to
contractile
cell via gap
junctions
L-type Ca+
channels is
open
Protein
kinase A is
activaed
L-type Ca+
channels
open
K+ channels
opens (inital
repolarization)
Plateau
T-tubules
open which
inceases Ca+
ions in
sarcolemma
Ca+ binds
with Troponin
C
CCC induces
Ca+ release
from SR
CCC binds
wiht
Ryanodine
receptor
Ca binds to a
protein in SR
(forms CaCalmodulin
complex)
Tropomyosin
unwinds
Actin head is
exposed
Crossbridge
(Powerstroke)
Increase HR
Contractile Cells
Epinephrine
binds to beta-1
adrenergic
receptor
Activates Gstimulatory
protein
Adenylate
Cyclase is
activated
L-type Ca+
channels is
open
Protein kinase
A is activaed
Catalyze ATP
into cyclic
AMP
(-
Protein Kinase A
also binds to
phospholamban
in SR
Increase Ca+
in SR
Increase HR
Parasympathetic Nervous System
ü G-inhibitory protein is divided into:
» Alpha-1
» Beta-1
Releases Acetylcholine
» Gamma-1
Releases Acetylcholine
AcH binds wiht Muscarinic-2
receptor
AcH binds wiht Muscarinic-2
receptor
G-inhibitory protein activated
G-inhibitory protein activated
Alpha-1 inhibits adenylate
cyclase
Beta1 & Gamma-1 stimulates
K+ channels
Inhibits protein kinase A
K+ efflux
L-type Ca+ channels is
inhibited
Repolarization
(-) Ca+
Decrease HR
Decrease HR
ü Needs help from the autonomic nervous system
ü Adenylate cyclase – present in nodal cell membrane
Sympathetic Nervous System
ü Excitatory
ü Releases epinephrine and norepinephrine
CARDIAC CYCLE
Factors
ü Atrial vs Ventricular pressure
ü Arterial pressure
» Pulmonary trunk
» Aorta
ü Atrioventricular valve
» Mitral
» Tricuspid
ü Semilunar valve
» Aortic valve
» Pulmonic valve
ü ECG
Atrial VS Arterial VS
Ventricular Ventricular
pressure
pressure
Terms
ü Diastole – ventricular filling
ü Systole – contraction or ejection into arteries
Phases
Mid to Late Ventricular Diastole
ü AKA Period of Rapid Filling
» 1/3 – 75% fast
» 2/3 – continuous
» 3/3 – 25% slow
ü Atrial pressure < ventricle
ü High pressure in both atrium
ü Blood will then move from atrium (high pressure) ®
ventricles (low pressure)
ü AV valves are open
» Pulmonary artery – 10 mmHg
» Aorta – 80 mmHg
ü Semilunar valves are closed
ü ECG – P wave
Isovolumetric Contraction
isoVolumetric
blood in Ventricle
Ventricular contraction
Mid to late
ventricular
diastole
Isovolumetric
contraction
Mid to late
ventricular
systole
Isovolumetric
relaxation
A>V
A>V
Open
Closed
P
wave
A<V
A>V
Closed
(S1)
Closed
QRS
wave
A<V
A<V
Closed
Open
QRS
wave
A<V
A>V
Closed
Closed
(S2)
T
wave
CARDIAC OUTPUT
ü Amount of blood pumped out of the heart per minute
ü CO = HR x SV
» 70 bpm x 70 mL = 5000 mL/min
ü (N) – 5 – 6 L/min
Mid to Late Ventricular Systole
Stroke Volume
ü End Diastolic Volume
» Blood in the ventricles after ejection
» 50 – 70 mL
ü Atrial < ventricular pressure
ü AV valves are closed
ü Semilunar valves are closed (due to some back flow of
blood from arteries)
» Produces S2 (“dub”)
ü ECG – T wave
ECG
Other Sounds
Heart Rate
Isovolumetric Relaxation
Semilunar
valves
ü S3
ven3cular gallop
» Ventricular gallop
» Brought about by blood turbulence during ventricular
filling
» S3 can be normal in children
» If (+) – CHF
ü S4
4tri4l gallop
» Atrial gallop
» Atrial contraction – extra force to pump blood out to
ventricles
» If (+) – cardiac problem
ü End Diastolic Volume
» Volume of blood in ventricles before ventricular
contraction or after atrial contraction
» 120 – 140 mL (130 mL)
ü Atrial < ventricular pressure
» (R) ventricle – 7 mmHg
» (L) ventricle – 60 mmHg
ü Blood goes up until it hits and closes the AV valves
» Produces S1 (“lub”)
ü Semilunar valves are closed
ü Still no emptying
ü ECG – QRS wave
ü AKA Period of Ejection
ü Atrial < ventricular pressure
ü Ventricular pressure can overcome arterial pressure
» (R) ventricle – 7 mmHg
» (L) ventricle – 120 mmHg
ü AV valves are closed
ü Semilunar valves are open
ü ECG – QRS wave
AV
valves
Increase HR
§ Sympathetic nervous
system
§ Hormones
o T3 – triiodothyronine
o T4 – thyroxine
§ Increase in Ca+
§ Decrease in K+
Decrease HR
§ Parasympathetic nervous
system
§ Decrease in Ca+
§ Increase in K+
ü Chronotropy
» (+) factors – increase HR
» (-) factors – decrease HR
ü Amount of blood pumped out per heartbeat
ü Factors that affect stroke volume
» Preload
§ Amount of stretch
§ ­ Preload, ­ Stroke volume
§ End diastolic volume
o ­ in venous return ® ­ EDV ® ­ stretch
§ Factors that affect ­ venous return
o Presence of good calves
o Milking action of muscles
o Increasing abdominal pressure
§ Frank-Starling Law – ­ stretch, ­ contraction
» Contractility
§ Inotropy
o (+) – increase in contractility
o (-) – decrease in contractility
§ ­ Contractility, ­ Stroke volume
» Afterload
§ AKA Systemic Vascular Resistance (SVR)
o Amount of resistance the heart must
overcome so that blood will exit from
ventricle towards systemic circulation
§ AKA Aortic resistance (80 mmHg)
§ ­ Afterload, ¯ Stroke volume
ü Stroke volume = End diastolic volume – End systolic volume
» 130 – 60 = 70 mL
FUNDAMENTALS OF BLOOD PRESSURE
ü Blood Pressure = CO x TPR
ü ­ BP = ­ CO & TPR
§ Normal pressure of the aorta
§ 80 mmHg
» Pulse pressure = SBP – DBP
» Mean Arterial Pressure
§ MAP = 𝐷𝐵𝑃 +
§ MAP = 𝐷𝐵𝑃 +
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§ MAP = ~93 mmHg
ü 1 mL = 1 cm3
ü Cardiac output is flow
CARDIAC COMPENSATORY MECHANISM
Baroreceptor Reflex
ü Stimulus – pressure
ü Parasympathetic nervous system ® stimulates vasomotor
tone ® vasodilation ® ¯ HR
Chemoreceptor Reflex
ü Stimulus – O2
Aortic and
Carotid sinus
Muscarinic-2
receptor
Flow
ü V = F/A
ü ­ flow, ­ velocity
ü ­ cross-sectional area, ¯ velocity
» Aorta – smallest cross-sectional area
» Capillary – highest cross-sectional area
» Exchange of nutrients happen in the capillary network
® slowest flow
» Blood needs to be delivered right away to tissues that
need oxygenated blood ® fastest blood flow in the
aorta
Total Peripheral Resistance (TPR)
ü TPR –
Inhibits
adenylate
cyclase
» R = 8 nl/πr4
» Factors that influence TPR
§ Viscosity (n)
§ Length (l)
§ Diameter (πr4)
ü Laminar flow – greater resistance when in periphery
(compared to central) due to contact in the epithelial lining
ü Turbulent flow – ­ flow, ­ velocity
ü Perfusion pressure
» PP = mean arterial pressure (MAP) – central venous
pressure (CVP)
» Central Venous Pressure (CVP)
§ (R) atrial pressure
§ 3 – 8 mmHg
» Systolic BP
§ Pressure ventricles needed to overcome aortic
pressure
§ 120 mmHg
» Diastolic BP
Nucleus
Tractus
Solitarius
Parasympathetic
NS releases AcH
Cardiac
Accessory
Center
(-) Calcium
Decrease HR
ü Increase in O2 – hypertension
ü Decrease in O2 – hypotension
ü Same mechanism as baroreceptor reflex
Renin-Angiotensin-Aldosterone System
ü Only activated during hypotension
ü Angiotensin II – potent vasoconstrictor
Liver releases Angiotensinogen
Kidneys releases Renin
Renin acts on angiotensinogen
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(%&)&*+,-%
ü Pouiseuilles’s equation
Sends signal to
Vagus nerve
Angiotensin I is produced
Angiotensin 1 flows to lungs
Angiotensin 1 acts on angiotensin converting enzyme from lungs
Angiotensin II is produced
Angiotensin activates adrenal gland
Adrenal gland secretes aldosterone
­ Na+ and H20 reabsoprtion
­ Blood volume
­ HR
Bainbridge Reflex
ü Stimulus – (R) atrium distention
ü Sympathetic nervous system ® increase HR to prevent
pooling of blood in (R) atrium