Cardiovascular Physiology Summary Notes for Dentistry (Year 1)
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Course
Biomedicine in Relation to Dentistry (4NNYBD01)
Institution
Kings College London (KCL)
Concise and easy to access notes on the physiology of the cardiovascular system for for first year dental students.
Covers the physics of the cardiovascular system (cardiac output, stroke volume, etc), cardiac cycle, electrical activity, electrocardiograms, cardiac output, control of blood pressu...
Physics of the Cardiovascular System
Definitions
• Cardiac output = Stroke volume x Heart rate
(volume of blood pumped by heart / min, ~5 L/min)
• Stroke volume = End diastolic volume – End systolic volume
(volume of blood pumped by ventricle / beat)
• Mean arterial blood pressure = Diastolic pressure + (Systolic pressure – Diastolic pressure) / 3
• Mean arterial blood pressure = Cardiac output x Total peripheral resistance
(average arterial pressure during a single cycle)
• Pulse pressure = Systolic pressure – Diastolic Pressure
Systolic pressure: maximum pressure during cycle, ~120 mmHg
Diastolic pressure: minimum pressure during cycle, ~80 mmHg
• Central (mean) venous pressure: amount of blood returning to the heart (i.e. the ability of the heart
to pump blood into the arterial system, ~0.5 mmHg
• Total peripheral resistance = (Mean arterial blood pressure - Central venous pressure) /
Cardiac Output
(sum of resistance of all peripheral vessels)
• Pulmonary vascular resistance = sum of resistance of all pulmonary vessels
• Preload: precontraction pressure in heart as blood volume builds up
• Afterload: force/resistance against which the heart pumps
• Venous Return: rate of flow of blood back to heart
Law of Flow / Darcy’s Law
• Flow = (P1 – P2) / R
• Flow ∝ pressure difference & Flow ∝ 1/resistance
• Pressure difference (driving pressure) = MABP – MVP
• (P1 – P2) flow is determined by resistance
Poiseuille’s Law
• : viscosity
• l: length of tube
• r: radius
• Small change in diameter → large change in resistance
Viscosity
• Axial Streaming: viscous drag at sides of blood vessels → fastest flow occurs in centre
of vessel → cells become aligned in fastest moving fluid
• Fahraeus-Lindquist Effect: viscosity is reduced in smaller vessels
Flow / Pressure
• Pulsatile flow progresses to laminar flow
• Number of capillaries increases → large decrease in pressure
• Pulmonary circulation pressure is lower to prevent damage to alveoli (i.e. pulmonary oedema)
• High velocity / sharp edges → disruption to laminar flow → turbulence
, Cardiac Cycle (1/2)
(1) Atrial Systole
• Patria > Pventricles (slightly) AV valves open
• Parteries > Pventricls SL valves are shut
• Most filling of ventricles takes place during diastole due to venous pressure
• Heart rate → ventricular filling takes less time → atrial contribution
• No valves between veins & atria → pressure in great veins (slightly)
(2) Isovolumetric Contraction (Ventricular Systole)
• Contraction of ventricles → ventricular pressure → AV valves shut
• 1st heart sound
• Pressure → bulge of AV valves into atria → c-wave → x descent
(3) Rapid Ejection (Ventricular Systole) (4) Reduced Ejection
• Once Pventricles > Parteries → SL valves open • Pventricles < Parteries (slightly) but blood
• Blood ejected into arteries very rapidly still flows due to momentum
• Contraction → ejection
(5) Isovolumetric Relaxation
• Flow briefly reverses → SL valves shut
• Patria slightly → dicrotic notch & 2nd heart sound
• Ejection fraction = Stroke volume / End diastolic volume (~60%)
• Diastole: ventricles relax → Pventricles
• Filling from veins → Patria (v wave)
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