This is an 187 page note deck that discusses the following topics regarding the Cardiovascular System:
Introduction to The Heart 3
Haemodynamics 7
Cardiac Cycle 15
Control of Cardiac Output 27
Electrical and Molecular Mechanisms in the Heart and Vasculature 36
Autonomic Control of the Cardiovascu...
electrical and molecular mechanisms of the heart and vasculature
autonomic control of cardiovascular system
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Cardiovascular System
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CARDIOVASCUL
SYSTEM
,Introduction to The Heart .....................................................................
Haemodynamics .................................................................................
Cardiac Cycle .....................................................................................
Control of Cardiac Output ...................................................................
Electrical and Molecular Mechanisms in the Heart and Vasculature ........
Autonomic Control of the Cardiovascular System...................................
Control of Blood Pressure ....................................................................
Understanding Arrhythmias: Actions of drugs on the cardiovascular syste
Special Circulations .............................................................................
Chest Pain and Acute Coronary Syndromes ..........................................
Investigation of Acute Coronary Syndromes ..........................................
The Pathophysiology of Heart Failure ...................................................
Heart Failure Investigation and Management ........................................
Haemodynamic Shock .........................................................................
Peripheral Arterial and Venous Disease ................................................
,INTRODUCTION TO THE HEART
Why do we need a cardiovascular system?
All living cells are metabolically active and use oxygen and produce carbon d
celled or tiny organisms can get oxygen and nutrients directly by diffusion fr
environment. However, larger organisms need a system for getting the oxyge
close to the cells.
The capillaries are where diffusion takes place.
Capillaries are composed of a single layer of
endothelial cells surrounded by basal lamina.
The heart also needs a blood supply. The left
ventricle is filled with oxygenated blood. The
left ventricle receives oxygenated blood from
the lungs but if something cuts off the supply of blood to the heart then we c
the cardiac tissue, even if the chamber is filled with oxygenated blood. The c
centimetre thick, therefore it would take half a day to receive the oxygen via
However, the distance of the cells from the source of the oxygen and nutrien
the muscle wall of the left ventricle will be seriously damaged if the vessels s
blocked.
Coronary arteries are vital to supply well oxygenated blood to the myocardiu
coronary arteries are blocked, the heart will die as oxygen cannot be supplied
muscle.
However, end arteries have few anastomoses* which mean, they do not conn
very much. Therefore, they are prone to atheroma which is narrowing due to
plaque formation.
*Anastomoses: A connection between
two things that are normally diverging
or branching.
,This is an anterior view of the heart showing the coronary arteries.
This is an anterior view of the heart showing cardiac veins.
,The Pericardial Sac
The Heart in situ
,Layers of the pericardium
Transverse pericardial sinus
It is important to know where the oblique sinus is.
,H A E M O DY N A M I C S
Plasma, serum and blood composition.
Serum is plasma without clotting factors. Whole blood viscosity changes are
uncommon (polcythaemia (Red blood cells), thrombocythaemia (platelets),
(white blood cells)).
Sludgey/thick blood can lead to dry
gangrene in peripheries.
Minor changes to plasma viscosity typically
from acute phase plasma proteins:
• fibrinogen
• compliment
• c-reactive protein (CRP) - result of
inflammation.
These proteins are used to measure plasma viscosity and are an indicator of
We typically measure CRP clinically.
We usually add heparin to prevent coagulation.
Movement of blood.
Movement of blood from one area of the CVS to another is vital and factors w
this are involved in ‘haemodynamics’. The metabolic demands of the body d
of the blood.
Blood is a mixture of cells and plasma and is considered fluid for modelling.
from relative high to low pressure regions.
,Laminar flow is smooth, maintaining energy and typical of most arteries, art
and veins. It is also silent.
Turbulent flow is disorganised and energy is lost in the ventricles and stenos
changing direction of vessels (branching). This is usually because pressure in
which flow can match it linearly.
Flow and pressure.
Fluid (blood) moves from an area of higher to lower
pressure, along a pressure gradient.
Flow and pressure in the circulation pulsate but for
basic considerations - think of a column with constant
head of pressure and steady state of flow.
Flow is volume transferred per unit time (L/min).
Pressure is force per unit area - mmHg used as
surrogate when measuring blood pressure though the
SI unit is Pascal.
Flow and resistance.
Flow is directly proportional to (P1-P2) which is the
pressure difference.
Therefore, flow = K(P1-P2) and K is conductance (measure of ease of flow).
R is resistance which is measure of difficult of flow- a reciprocal of K (1/K).
Flow = Difference in Pressure/Resistance.
R = P1-P2/Flow so the difference in mean pressure needed to move one uni
steady state - mmHg min/L. Therefore, if resistance increases and flow is m
pressure difference has to rise.
,Smallest arteries and arterioles contribute to the greatest component of total
resistance - the biggest jump in pressure across vessel class.
Arterioles are the seat of total peripheral resistance.
Resistance in the pulmonary circulation is much lower than systemic system
wider vessels.
The right ventricular muscle is smaller as the pressure needed to get blood t
pulmonary system is much less than the left ventricle.
Flow and Velocity.
Velocity needs to be considered and not confused with flow. Velocity is the d
moves in a given time (cm/s).
Flow (F) of blood in a vessel is related to velocity:
At constant radius, changes in V are proportionate to F.
At constant flow, V is inversely related to radius squared.
Velocity and Area.
Consider the capillaries where the cross sectional area is vast and thousand
than that of aorta or named arteries.
Velocity at the capillary level is much slower than at the aorta or large arterie
important because you meet metabolic demands, supply oxygen tot he tissue
happen slower to allow time for that to happen.
Velocity increases again as vessel merge into larger veins and into the vena c
, Below 70 mmHg - organ perfusion becomes impaired.
We have pressure on y and time on x axis. This is one cardiac cycle. The low
when the ventricles fill and ejects blood out of it, and we have a peak systolic
120 mmHg, and it has a lot of elastin in it and pushes that blood through th
circulation.
We have a diachotic notch. Blood pressure is regulated variable and if you in
usually due to hypertension or exercise, but when asleep it is slower. It chan
and is different but it is regulated physiologically. The pulse pressure is diffe
the systolic and end diastolic pressure. The mean arterial pressure is an aver
pressure during one cardiac cycle so there is a pressure difference throughou
system. The average pressure is the mean arterial pressure. This is equal the
pressure and 1/3 of the pulse pressure.
We can guesstamate. That is not arithmetic mean but it is time weighted an
under the curve/time.
Organ perfusion is compromised if the blood pressure ever drops below 70 m
organs are perfused sufficiently.
Pulse pressure.
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