Download CO - Moodle

Responding to ill Health
Life Science
The Cardiovascular System
Stanwhit607 (2007)
https://commons.wikimedia.org/wiki/File:Humhrt2.jpg
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Learning outcomes
Explain in detail the coronary blood supply (coronary arteries
and coronary veins).
Discuss the events of the cardiac cycle.
Explain the structure and function of the conduction system of
the heart and how this relates to normal E.C.G. pattern.
Discuss in detail the physiology of blood pressure and the
factors which influence it.
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The Cardiovascular System
(revision)
Function ??
 maintains continuous blood flow to and from all body
cells – supplies nutrients and removes wastes
Components ??
 Heart
 Blood vessels
 Blood
- ‘CARDIO’
- ‘VASCULAR’
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Double Circulation (revision)
Pulmonary circulation
 to and from lungs
Systemic circulation
 to and from body
 blood from right side of
heart only reaches left side
via the lungs – i.e. blood in
heart does not mix
UWS Staff (2015)
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Conducting System
 Heart = pump
 needs coordinated synchronised contractions of
cardiac cells
 initiated and controlled by specialised cells
i.e. conducting system:
 SA node
- pacemaker
 AV node + ‘wiring’ - conduct & spread impulse
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The pacemakers of the heart
Madhero88 (2009) Electrical_conduction_system
https://commons.wikimedia.org/wiki/File:Electrical_conduction_system_of_the_heart.svg?uselang=en-gb
Lynch (2006) Heart right anatomy
http://commons.wikimedia.org/wiki/File:Heart_right_anatomy.jpg?uselang=en-gb
Sino-atrial (SA) node (pacemaker)
 in wall of right atrium
 impulse spreads from SA node to both atria
 causes atrial contraction
Atrioventricular (AV) node
 node of neuromuscular cells at base of right atrium very
near septum
 impulse from SA node reaches AV node
 There is a pause in conduction of impulse from AV node
(until atrial contraction + filling of ventricles is
complete)
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 impulse passes from AV node to septum & then across
walls of both ventricles
(Bundle of His, R & L bundle branches, Purkinje fibres)
 ventricle contracts
NB co-ordination of heart beat – 2 atria then 2
ventricles
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Cardiac cycle
 events of one heartbeat
 systole = period of contraction
 diastole = period of relaxation
revise structure of heart & direction of blood flow in
order to understand cardiac cycle
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Cardiac cycle
Events of cardiac cycle depend on heart structure,
particularly:
 location & orientation of heart valves
 pressure of blood in different chambers
 blood vessels associated with heart
Useful animation:
http://library.med.utah.edu/kw/pharm/hyper_heart1.html
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Josiño (2010)
https://commons.wikimedia.org/wiki/File:Latidos.gif
CARDIAC CYCLE
LadyofHats (2008)
https://commons.wikimedia.org/wiki/File:Human_healthy_pumping_heart_en.svg
Cardiac cycle
1. passive ventricular filling
2. atrial systole
3. ventricular systole
4. ventricular diastole
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1. Passive ventricular filling
 blood enters R & L atria, pours passively through
open AV valves into ventricles
 atrioventricular valves open – semilunar
(pulmonary & aortic) valves shut
 atria & ventricles in diastole, pressure in each
remains constant
 pressure in ventricles does not rise, as walls
expand to receive incoming blood
 accounts for 70% of ventricular filling
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2. Atrial systole





SA node discharges
atrial contraction, ventricles in diastole
30% of ventricular filling
AV valves open, semilunar valves shut
pressure rises in both atria & ventricles
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3. Ventricular systole
 impulse from AV node  ventricular contraction,
ventricular pressure rises , AV valves shut
 when ventricular pressure  than BP in systemic &
pulmonary arteries semilunar (pulmonary) valves
open
 atria in diastole - filling passively, ventricles in systole
 AV valves open then shut, semilunar valves shut then
open
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4. Ventricular diastole
 ventricles relax, pressure falls, semilunar valves
shut
 ventricular pressure falls below atrial pressure, AV
valves open
 back to passive ventricular filling
 atria in diastole, ventricles in diastole
AV valves shut then open,
semilunar valves open then shut
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Click slide to
start animation
Cardiac Cycle
AV (inlet) valve
SL (outlet) valve
P
ventricle
contracting
relaxing
relaxed
P
PP
UWS Staff (2015)
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Electrocardiogram
 Diagnostic tool (powerful)
 Evaluates electrical events in heart via currents
generated in body fluids
 Detects: Mis, Conduction blocks, Arrhythmias
 3 recognised wave forms
 P wave
=
A contraction
 QRS complex =
V contraction; A repolarization
 T wave
=
V repolarization
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ELECTROCARDIOGRAM (ECG)
Anthony Atkielski (2007) SinusRhythmLabels
https://commons.wikimedia.org/wiki/File:SinusRhythmLabels.svg?uselang=en-gb
Interpretation of ECG
 P wave: atrial depolarisation - atria about to contract
 Q, R, S waves: ventricular depolarisation – ventricles
about to contract; and atrial repolarization
(relaxation of atrial muscle)
 T wave: ventricular repolarization (relaxation of
ventricular muscle)
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ECG – examples of diagnosis
Normal
Bundle branch
block
Madhero88 (2010)
https://commons.wikimedia.org/wiki/File:ECGbasic.svg
https://commons.wikimedia.org/wiki/File:Bundle_branch_block.svg
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Coronary Arteries
Patrick J. Lynch, (2010)
https://commons.wikimedia.org/wiki/File:Coronary_arteries.svg?uselang=en-gb
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Coronary Arteries
Anatomist90 (2011)
https://commons.wikimedia.org/wiki/File:Coronary_arteries_1.jpg?uselang=en-gb
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When does blood flow through coronary circulation?
Only during diastole, when aortic valve ‘closes’,
opening access to coronary circulation
NOTE:
increased heart rate > period of diastole shortens
> decrease blood flow > conflict with the needs of the heart
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PHYSIOLOGY OF BP
 BP
 pressure exerted by blood on vessel wall
 Where does this pressure come from ??
• BP drives blood flow – maintains oxygen supply to
organs of the body – brain and heart in particular
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Pressure in the Vascular System
OpenStax College (2013)
https://commons.wikimedia.org/wiki/File:2109_Systemic_Blood_Pressure.jpg
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Clinically:
 BP = pressure in large arteries
(~ same throughout body)
 BP is not constant PULSATILE:
 max. (systole)
= ventricular contraction
 min. (diastole)
= ventricular relaxation
Icternol (2015)
https://commons.wikimedia.org/wiki/File:Augmentation-index.PNG
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Blood Pressure Values
 normal range:
systolic: 90 - 140 mmHg
diastolic: 60 - 90 mmHg
 BPs within this range  NORMOTENSIVE
if SP > 140 mmHg
or DP > 90 mmHg
 HYPERTENSIVE
 if SP < 90 mmHg
or DP < 60 mmHg
 HYPOTENSIVE
Both dangerous
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Blood Pressure Determinants
1. cardiac output (CO)
2. peripheral resistance (PR)
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Note: Total Blood Volume also helps
determine blood pressure
 ~ 5 Litres in average person
 does not vary greatly
 i.e. total blood vol. NOT used to control BP
however:
 volume of blood in arteries does dictate BP
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1. Cardiac Output (CO)
 volume of blood pumped out of ventricle per minute
CO = heart rate x stroke volume
(beats/min)
(mL)
SV - vol. of blood pumped out by ventricle per
heart beat
CO = 75 x 70
- typically 70 mL
= 5250 mL/min
= 5.25 L/min
HR - typically 75 bts/min
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1. Cardiac Output (CO)
 CO same for both left and right ventricles
 HR + SV can be rapidly changed, thus changing CO
 changes in CO can be used to rapidly control BP
e.g. haemorrhage
 BP
 HR
 SV
 CO
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2. Peripheral Resistance
 total vascular resistance to flow
 Can change with vessel length (doesn’t vary) and
blood viscosity (may vary with disease)
 Vessel radius is the major mechanism
determining peripheral resistance
 radius   Resistance
due mainly to:
 arterioles = chief resistance vessels
 arteriole resistance + hence peripheral resistance
can be rapidly changed to control BP
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Further Determinant
Venous return
 ‘the heart can only pump out what it gets in’
 i.e. ventricle must fill before it can pump –
this is determined by the volume of blood
returning via the veins to the heart
i.e. venous return
 venous return   CO
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Factors Influencing BP
BP = CO x p.resistance
HR x
ANS:
 sympathetic

SV
arteriolar
resistance
 CO
 arteriolar resistance
 parasympathetic 
 CO
 changes in BP are corrected for by the ANS
(-ve feedback)
some hormones
 e.g. Adrenaline 
 CO
 arteriolar resistance 36
Factors Influencing BP (contd)
 temperature
e.g. fever   HR   CO
 emotions (higher brain)
anger
 CO
fear

 arteriolar resistance
anxiety
  BP
• endocrine systems controlling blood volume can
influence BP
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Summary
 Conducting system
 Cardiac cycle
 Coronary circulation
 VITAL to maintain BP
 Main determinants: - CO
-Blood volume (in arteries)
- Peripheral resistance
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