cardiovascular physiology

bsu unversity russia

1. Cardiovascular Physiology

2. Lecture Outline
•Cardiovascular System Function
•Functional Anatomy of the Heart
•Properties of Myocardium
•Cardiac Cycle
•Cardiac Output
•Blood Pressure

3. Cardiovascular system
isthesystemofheartandblood
vesselsthatcirculatebloodthroughout
thebody.

4. Functions of cardiovascular
system
•Circulates OXYGEN and removes Carbon
Dioxide.
•Provides cells with NUTRIENTS.
•Removes the waste products of
metabolism to the excretory organs for
disposal.
•Transports HORMONES to target cells
and organs.
•Helps regulate body temperature.

5. Cardiovascular System
•Functional components of the
cardiovascular system:
1.Heart
2.Blood Vessels
3.Blood

6. What Are the Parts of the Circulatory
System?
•Two pathways come from the heart:
•The pulmonary circulationis a short loop
from the heart to the lungs, where blood is
oxygenatedand.
•The systemic circulationcarries blood
from the heart to all the other parts of the
body.

7. Pulmonary circulation
•In pulmonary circulation:
•The pulmonary artery is
a big artery that comes
from the heart. It brings
blood from the heart to
the lungs. At the lungs,
the blood picks up
oxygen and drops off
carbon dioxide. The
blood then returns to the
heart through the
pulmonary veins.

8. Systemiccirculation
Theleftsideoftheheart
pumpsbloodtotherestofthe
tissuesofthebodythroughthe
systemiccirculation:Blood
pumpedfromleftventricle
passesthroughaseriesof
bloodvessels,arterialsystem
andreachesthetissues.
Exchange of various
substancesbetweenbloodand
thetissuesoccursatthe
capillaries.Afterexchangeof
materials,bloodentersthe
venoussystemandreturnsto
rightatriumoftheheart.From
rightatrium,bloodentersthe
rightventricle.

9. The Circulatory System

10. HEART
•The heart is a muscular organ about
the size of a closed fist that functions
as a body’s circulatory pump.

11. Functionalanatomyoftheheart
Theheartislocatedin
thecenterofthethoracic
cavity.Itsitsdirectly
abovethemusclesofthe
diaphragm, which
separatesthethoraxfrom
theabdomen,andlies
beneaththesternum
betweenthetwolungs.

12. Theheartisenclosed
andanchoredinplace
byadouble-walled
fibroussacreferredto
asthepericardium.
Themembranesof
thepericardiumproduce
asmallamount
ofpericardialfluid
thatminimizesfriction
producedbythemovement
oftheheartwhenitbeats.
FUNCTIONAL ANATOMY OF THE HEART

13. Functional Anatomy of the Heart
CARDIAC MUSCLE
•Characteristics:
–Striated
–Short branched cells
–Uninucleate
–Intercalated discs

14. Functional Anatomy of the Heart
CHAMBERS
Human heart
has 4 chambers
–2 Atria
–2 Ventricles
Chambers
are separated
by septum…
Due to separate
chambers,
heart functions as double pump

15. Functional Anatomy of the Heart
VALVES
Twosetsofvalvesintheheartmaintainthe
one-wayflowofbloodasitpassesthrough
theheartchambers:
•Atrioventricular(AV)valves
•Semilunarvalves

16. Functional Anatomy of the Heart
VALVES
Eachofthesevalvesconsistsof
thinflapsofflexiblebuttough
fibroustissuewhosemovements
arepassive.
Theatrioventricular(AV)
valvesarefoundbetweenthe
atriaandtheventricles.
TherightAVvalveisatricuspid
valveandhasthreecuspsor
leaflets.TheleftAVvalve(also
referredtoasthemitralvalve)is
abicuspidvalvebecauseithas
twocusps.

17. Functional Anatomy of the Heart
VALVES
The semilunar valves
separatetheventriclesfrom
theirassociatedarteries.
Thepulmonaryvalveisfound
betweentherightventricleand
thepulmonaryarteryandthe
aorticvalveisfoundbetween
theleftventricleandtheaorta.
These valves prevent
backwardflowofbloodfrom
thepulmonaryarteryorthe
aortaintotheirpreceding
ventricleswhentheventricles
relax.Thesemilunarvalves
alsohavethreecusps.

19. Functional Anatomy of the Heart
The walloftheheart
Thewallofthehearthasthreelayers:
•Epicardium
•Endocardium
•Myocardium
Theoutermostlayer,theepicardium,isthethinmembrane
ontheexternalsurfaceoftheheart.Theinnermostlayer,
theendocardium,consistsofathindelicatelayerofcells
liningthechambersoftheheartandthevalveleaflets.
Theendocardiumiscontinuouswiththeendothelium,
whichlinesthebloodvessels.
Themiddlelayeristhemyocardium,whichisthe
muscularlayeroftheheart.Thisisthethickest
layer,althoughthethicknessvariesfromone
chambertothenext.Thicknessofthemyocardium
isrelatedtotheamountofworkthatagiven
chambermustperformwhenpumpingblood.

20. Properties of myocardium
•Differentcellswithintheheartare
specializedfordifferentfunctionalroles.In
general,thesespecializationsarefor
1.automaticity
2.excitability
3.conduction
4.contraction

21. Automaticity
•The specialized (pacemaker) cells of heart
spontaneously depolarize to threshold and
generate action potential. They are located in
•Sinoatrial(SA)node
Thiscellshavethehighestintrinsicrhythm(rate),making
themthepacemakerinthenormalheart.Theirintrinsic
rateis60-100beats/min.
•Atrioventricular(AV)node
Itscellshavethesecondhighestintrinsicrhythm(40-
60beats/min).Often,thesecellsbecomethepacemaker
ifSAnodecellsaredamaged.
•Purkinjefibers
Theyexhibitspontaneousdepolarizationwitharateof–35
beats/min.

22. Myocardial Physiology
Autorhythmic Cells (Pacemaker Cells)
•Characteristics of
Pacemaker Cells
–Smaller than
contractile cells
–Don’t contain many
myofibrils
–No organized
sarcomere structure
•do not contribute to
the contractile force
of the heart
normal contractile
myocardial cell
conduction myofibers
SA node cell
AV node cells

23. Automaticity
AutorhythmicCells (Pacemaker Cells)
•Characteristics of Pacemaker Cells: They
have unstablemembrane potential
•“bottoms out”at -60mV
•“drifts upward”to -40mV, forming
a pacemaker potential
•The upward “drift”allows the membrane
to reach threshold potential (-40mV) by
itself
•This is due to:
1.Leakage Na
+
causes slow depolarization
2.Ca
2+
voltage-gated channels opening as
membrane approaches threshold (Ca
2+
goes in)
At threshold additional Ca
2+
voltage-gated
channels open causing more rapid
depolarization
3. Slow K
+
voltage-gated channels open
causing an efflux of K
+
(K
+
goes out) and
a repolarization of membrane
Ca
2+
in K
+
out
Ca
2+
in
Na
+
in

24. The RMP in different cell types

25. Excitability
Contractile Cells
•Special aspects
–Intercalated discs
•Highly convoluted and
interdigitatedjunctions
–Joint adjacent cells with
»Desmosomes & fascia adherens
–Allow for synticialactivity
»With gap junctions
–More mitochondria than skeletal
muscle
–Less sarcoplasmic reticulum
•Ca
2+
also influxes from ECF reducing
storage need
–Larger t-tubules
•Internally branching
–Myocardial contractions are
graded!

26. EXCITABILITY
Phases of action potential of contractile
cells

27. Excitability
Action potential of contractile cells
•Phase 0
(depolarization)begins when
the membrane potential
reaches threshold (–40 mV).
Similar to nerve and skeletal
muscle, mediated by the
opening of voltage-gated, fast
Na+ channels
•Phase 1 (initial
repolarization) Slight
repolarization mediated by a
transient potassium current.
Sodium channels are in the
inactivated state.

28. Excitability
Action potential of contractile cells
•Phase 2 (plateau)
Depolarizationopensvoltage-gatedCa
2+
channels
andvoltage-gatedK+channels
•Phase 3(repolarization)
At this point, the Ca++ channels close and K+
channels open. The resulting efflux of K+ ions
causes the repolarization phase of the action
potential.
•Phase 4Resting membrane potential

29. Excitability
Action potential of contractile cells
•Asinneurons,cardiacmuscle
cellsundergoanabsoluteor
effectiverefractoryperiodin
which,atthepeakoftheaction
potential,thevoltage-gatedfast
Na+channelsbecomeinactivated
andincapableofopening
regardlessoffurtherstimulation.
Asaresult,theabsoluterefractory
periodlastsalmostaslongasthe
durationoftheassociated
contraction—about250msec.
Thephysiologicalsignificanceof
thisphenomenon isthatit
preventsthedevelopmentof
tetanusorspasmofthe
ventricularmyocardium.
Theeffectiverefractoryperiodisfollowedby
arelativerefractoryperiodthatlastsforthe
remaining50msecoftheventricularaction
potential.Duringthisperiod,action
potentialsmaybegenerated;however,the
myocardiumismoredifficultthannormalto
excite.

30. Myocardial Physiology
Contractile Cells
•Skeletal Action Potential vs Contractile
Myocardial Action Potential

31. Conduction
Intrinsic Conduction System
•Consists of
“pacemaker”
cells and
conduction
pathways
–Coordinate the
contraction of the
atria and
ventricles

32. Contractility
•Initiation
–Action potential via pacemaker
cells to conduction fibers
•Excitation-Contraction Coupling
1. AP spreads along sarcolemma
•T-tubules contain voltage gated L-
type Ca
2+
channels which open upon
depolarization
•Ca
2+
entrance into myocardial cell
and opens RyR(ryanodine receptors)
Ca
2+
release channels
2.Ca
2+
(Ca
2+
from SR and ECF) binds
to troponin to initiate myosin head
attachment to actin
•Contraction

33. Contractility
•Relaxation
–Ca
2+
is transported back
into the SR and
–Ca
2+
is transported out of
the cell by a facilitated
Na
+
/Ca
2+
exchanger (NCX)
–As ICF Ca
2+
levels drop,
interactions between
myosin/actin are stopped
–Sarcomere lengthens

34. Electrocardiography
•is the recording of the electrical activity
of the heart.
•It is based on recording of
electric potentialsgenerated by heart on
different body parts (mostly on body
surface)
Electrocardiogram is graphic record
of the electrocardiography

35. Elements of ECG
1.Waves
2.Segments
3.Intervals

36. Elements of ECG
•Waves are parts of ECG, which are
located above or below the isoline.
•Segments are parts of ECG, which are
located on the isoline.
•Intervals include waves and segments.

37. Waves of ECG

38. Waves of ECG
•P waverepresentsatrial depolarization
•QRS complexrepresentsventricular
depolarization
•T wave representsventricular
repolarization
•U wave representsrepolarization of the
papillary muscles or Purkinje fibers.

39. Blood Vessels
Over 80,000 miles of blood vessels transport your blood throughout your body.
There are 3 types of blood vessels.
•Arteries:Blood vessels
that carry blood away
from the heart to other
parts of the body.
•Veins: Blood vessels
that carry blood from
the body back to the
heart.
•Capillaries: Tiny tubes
that carry blood from
the arteries to the
body’s cells, and then
back to the veins.

40. Arteries:
carries blood Away from heart
–Large
–Thick-walled, Muscular
–Elastic
–Oxygenated blood
Exception Pulmonary Artery
–Carried under great pressure
–Steady pulsating
Arterioles: smaller vessels, enter tissue

41. Capillaries
–Smallest vessel
–Microscopic
–Wall one cell thin
–Nutrients and
gases diffuse here

42. Veins:
Carries blood to heart
–Carries blood that contains
waste and CO
2
•Exception pulmonary vein
–Blood not under much
pressure
–Valvesto prevent much
gravity pull
Venules: larger than capillaries

43. Blood

44. Blood Components
Blood is made up of plasma and
formed elements
Plasma: It transports blood solids,
nutrients, hormones, and other
materials.
Formed elements:
–Erythrocytes (Red blood cells)
–Leukocytes (White blood cells)
–Platelets (thrombocytes)

45. Red blood cells
1.Made up about 99%
of the blood’s cellular
component
2.Small, disk-like shape
3.No nucleus
4.Cannot reproduce
5.Last 4 months then
rupture
6.Produced by red bone
marrow
7.Contain hemoglobin
8.Carry oxygen

46. Hemoglobin
•Hemoglobin is a
complex protein
made up of four
protein strands, plus
iron-rich heme
groups.
•Each hemoglobin
molecule can carry
four oxygen atoms.
The presence of
oxygen turns
hemoglobin bright
red.

47. White blood cells
•Nucleus present
•Types of leukocytes:
•most are neutrophils
that engulf
microorganisms
•Basophils
•Eosinophils
•Lymphocytes
Active in immune system.
Help fight disease and infection by
attacking germs that enter the body.

48. Platelets
•Platelets are cell
fragments used in
blood clotting.
•Platelets are derived
from egakaryocites.
Help blood form a clot at the
site of a wound. A clot seals a
cut and prevents excessive
blood loss.

49. The Cardiac Cycle:
Events of the cardiac
cycle

50. •He developed the
modern criteria of
phase analysis of
the cardiac cycle
(1921).
21st APS President (1949-1950)
Carl J. Wiggers
(1883-1963)

51. •Cardiac cycle refers to all events associated
with blood flow through the heart. A single
cycle of cardiac activity can be divided into
two basic phases:
–Systole–contraction of heart muscle
–Diastole–relaxation of heart muscle
The Cardiac Cycle

52. The Cardiac Cycle

53. The Cardiac Cycle (0,8 sec)
Ventricular Systole(0,33 sec)
•Period of Isovolumic Contraction(0,08sec)
Phase 1. Asynchronouscontraction(0,05sec)
Phase 2. Isovolumic contraction(0,03 sec)
•Period of Ejection(0,25sec)
Phase 3. Rapid ejection(0,12 sec)
Phase 4. Reduced ejection(0,13 sec)
Ventricular Diastole(0,47 sec)
•Period of Isovolumic Relaxation (0,12 sec)
Phase 5. Protodiastole(0,04 sec)
Phase 6. Isovolumic relaxation (0,08 sec)
•Period of filling (0,35 sec)
Phase 7. Rapid filling(0,08 sec)
Phase 8. Reduced filling (0,17 sec)
Phase 9. Presystole (0,1 sec)

55. Phase 1.Asynchronouscontraction
•The beginning of this phase
= the end of Presystole (phase 9) = the end of diastole
•The endof this phase
= the beginningof Isovolumic contraction (phase 2)
The beginning of phase
AV valves are open
SL valves are closed
The end of phase
AV valves are closed
SL valves are closed
Duringthisphase:
•Ventricular contraction
•The ventricular cavity volume
doesn't change
•The ventricular cavity pressure
doesn't change

56. Phase 2.Isovolumic contraction
•The beginning of this phase
= the end of Asynchronouscontraction(phase 1)
•The endof this phase
= the beginningof Rapid ejection phase(phase 3)
Duringthisphase,
Ventricular contraction
The ventricular cavity volume doesn't change
The ventricular cavity pressure increases
The beginning of phase
AV valves are closed
SL valves are closed
The end of phase
AV valves are
closed
SL valves are open

57. Phase 3.Rapid ejection
•The beginning of this phase
= the end of Isovolumiccontraction(phase 2)
•The endof this phase
= the beginningof Reduced ejection(phase 4)
The beginning of phase
AV valves are closed
•SL valves are open
The end of phase
AV valves are
closed
SL valves are
openDuringthisphase:
Ventricular contraction
2/3rd of stroke volume rapid ejected
The ventricular cavity volume decreases
The pressure inside the ventricles rises
to 120 mmHg

58. Phase 4.Reduced ejection
•The beginning of this phase
= the end of Rapid ejection (phase 3)
•The endof this phase
= the beginningof Protodiastole (phase 5)
= the end of Systole = the beginningof Diastole
The beginning of phase
•AV valves are closed
•SL valves are open
•The end of phase
•AV valves are closed
•SL valves are open
Duringthisphase:
•Ventricular contraction
•1/3rd of stroke volume slow ejected
•The ventricular cavity volume decreases
•The pressure inside the ventricles decreases slightly

59. Phase 5.Protodiastole
•The beginning of this phase
= the end of Reduced ejection (phase 4)
•The endof this phase
= the beginningof .Isovolumic relaxation (phase 6)
The beginning of phase
•AV valves are closed
•SL valves are open
The end of phase
•AV valves are closed
•SL valves are closed
Duringthisphase:
•Theventriclesare relaxing
•Theventriclesaren’t filling
•The ventricular cavity volume doesn't change
•The pressure inside the ventricles doesn't change

60. Phase 6.Isovolumic relaxation
The beginning of this phase
= the end of Protodiastole(phase 5)
•The endof this phase = the beginning
of Rapid filling(phase 7)
The beginning of phase
•AV valves are closed
•SL valves are closed
The end of phase
•AV valves are open
•SL valves are closed
Duringthisphase,
Theventriclesare relaxing
Theventriclesaren’t filling
The ventricular cavity volume
doesn't chan
The pressure inside the
ventricles increases
significantly

61. Phase 7.Rapid filling
•The beginning of this phase
= the end of Isovolumicrelaxati(phase 6)
•The endof this phase
= the beginningof Reduced ventricular filling (phase 8)
The beginning of
phase
AV valves are open
SL valves are
closed
The end of phase
AV valves are open
SL valves are
closed
Duringthisphase:
Theventriclesare relaxing
Theventriclesare rapid filling
The ventricular cavity volume increases
The pressure inside the ventricles increases
slightly

62. Phase 8.Reduced filling
The beginning of this phase
= the end of Rapid filling (phase 7)
The endof this phase
= the beginningof Presystole(phase 9)
The beginning of phase
•AV valves are open
•SL valves are closed
•The end of phase
•AV valves are open
•SL valves are closed
Duringthisphase,
Theventriclesare relaxing
Theventriclesare slow
filling
The ventricular cavity
volume increases
The pressure inside the
ventricles increases slightly

63. Phase 9.Presystole
•The beginning of this phase
= the end of Reduced filling (phase 8)
•The endof this phase
= the beginningof ventricular systole(phase 1)
= the beginningof ventricular systole
= the end of ventricular diastole
The beginning of phase
•AV valves are open
•SL valves are closed
The end of phase
•AV valves are open
•SL valves are closed

64. Phase 9.Presystole
Duringthisphase,
•During ventricular relaxationbloodflowsfrom
atria to ventricles. When both atria contracts
almost simultaneously and pupms remaining 25%
ofbloodflowsin respective ventricles (therefore
even when if atrial fails to function it is unlikely to
be noticed unless a personexercises).
•Theventriclesare rapid filling
•The ventricular cavity volume increases
•The pressure inside the ventricles increases
slightly

65. IntracardiacPressure

66. Cardiac Cycle
Blood Volumes & Pressure

67. Cardiac Output
•Cardiac Output (CO) is the volume pumped by
the left ventricle each minute
–influenced by
•Stroke Volume (SV)
EDV –ESV = SV
135ml –65ml = 70ml
•Heart Rate (HR) bpm
–CO = SV x HR
(70ml/b x 72bpm = 5040 ml/min
=5.04L/min)

68. Blood Vessel Structure
•enables specific functions
–Aorta
•absorb pulse pressure
(systolic pressure –diastolic
pressure) and release
energy creating diastolic
pulse
–Large arteries
•conduct and distribute blood
to regional areas
–Arterioles
•Regulate flow to tissues and
regulate MAP (mean arterial
pressure)

69. –Capillaries
•Allow for exchange
–Venules
•Collect and direct
blood to the veins
–Veins
•Return blood to heart
and act as a blood
reservoir
Blood Vessel Structure

70. Physical Characteristics of the
Circulation

71. •Hemodynamicsis the description of the
laws which govern blood flow within the
vasculature.
•Ultimately, all blood flow between two
points within the vasculature is actuated
by differences in the pressure of blood
between those two points.

72. Interrelationships Among
Pressure, Flow, and
Resistance

73. Blood flow through a vessel is
determined by2factors:
•pressure gradientalong the vessel
(pressure difference of the blood between
the two ends of the vessel)
•vascular resistance (impediment to blood
flow through the vessel)

74. The flow through the vessel can be
calculated by the following formula, which is
called Ohm’s law :
Q = (P1 -P2) / R
•in which Qis blood flow,
•(P1 -P2)is the pressure difference
between the two ends of the vessel,
•Ris the resistance.

75. Blood Pressure
–Systolic Pressure
•The pressure that is created when the ventricles
contract
•Usually around 120 mm Hg

76. Blood Pressure
–Diastolic Pressure
•The pressure that is created by the recoil of the
aorta AND the closure of the aortic semilunar valve
•Usually around 80 mm Hg

77. Blood Pressure
Pulse Pressure
•Pulse Pressure=Systolic Pressure -Diastolic
Pressure
•The difference between the systolic and diastolic
pressures
–Usually 40 mm Hg (120 mm Hg –80 mm Hg)
•Only applies to arteries
Mean Arterial Pressure
•We can determine the average pressure within the
arterial system = Mean Arterial Pressure (MAP)
MAP = Diastolic Pressure + 1/3 Pulse
Pressure
MAP = 80 mm Hg + 1/3( 120 mm Hg –80 mm
Hg)
MAP = 93 mm Hg

78. QUESTIONS
1.The cardiovascular system. Functions. The pulmonary and systemic circuits.
2.The heart muscle cells. Structure.
3.Propertiesofthe cardiacmuscle.
4.Automaticity of the heart. Pasemakercells.
5.Conductivity of the heart. Conductive system of the heart.
6.Excitability of the heart. Cardiac Action potential . The refractory periods of the cardiac muscle.
7.Contractility of the heart. Mechanism of cardiac muscle cell contraction.
8.The normal electrocardiogram.
9.Elements of ECG.
10.Mechanical events in the heart: cardiac cycle . Steps of the cardiac cycle .
11.Electrical events of cardiac cycle.
12.The origin of the heart sounds.
13.Ventricularvolume-pressureloop.
14.Stroke volume. Control of stroke volume. Ejectionfraction.
15.Cardiac output (CO). Regulation of CO .
16.Types and characteristics of blood vessels.
17.Relationship between blood flow, pressure and resistance.
18.Pressures in the cardiovascular system. Arterial pressure in the systemic circulation: diastolic,
systolic, pulse and mean arterial pressures.
19.Neural Regulation of Blood Pressure.