Cardiovascular System

Arteries

Transports oxygenated blood away from the heart towards distal organs/tissues under high pressure

Veins

Transport deoxygenated blood towards the heart away from the distal organs/tissues under low pressure

Capillaries

Connect arteries to veins, responsible for gaseous exchange

Heart rate

Number of complete cardiac cycles in one minute (70 bm at rest)

Stroke volume

Volume of blood leaving the heart each beat (70 ml at rest) 

Cardiac output

Volume of blood leaving the heart per minute (5l at rest)  - Q = SV x HR 

What are the two atrioventricular valves?

Tricuspid + mitral/bicuspid

What are the two semilunar valves?

Aortic + pulmonary valves

2 aspects of semilunar valves

No attachments

Work based on pressure of blood flow

What are the three layers of the heart?

Pericardium

Myocardium

Endocardium

Pericardium fluid function

Fluid in the pericardial space reduces friction created by movement of the heart pumping blood

3 aspects of myocardium

Contain cardiomyocytes

Thickest layer

Contain coronary arteries which provide blood supply

3 aspects of cardiomyocytes

Striated

Contain many mitochondria

Have auto-rhythmicity

2 aspects of endocardium

Single celled

Contain endothelial cells

How does the cardiac cycle start?

Blood enters the right atrium via the inferior and superior vena cava.

What happens after blood enters the right atrium?

The right atrium fills and blood begins to passively flow into the right ventricle

What happens after the passive flow into the right ventricle?

The right atrium contracts and the tricuspid valve closes to prevent blood backflow. 

What happens after right atrium contraction?

The right ventricle contracts and blood leaves the ventricle via the pulmonary valve into the pulmonary artery, and to the pulmonary circulatory system (lungs). 

What happens after the right ventricle contracts?

Oxygenated blood returns to the left atrium via the pulmonary vein. 

What happens after blood returns to the left atrium?

Blood passively flows into the left ventricle. 

What happens after blood flows into the left ventricle?

The left atrium contracts and the bicuspid/mitral valve closes to prevent blood backflow. 

What happens after the left atrium contracts?

The left ventricle contracts and blood leaves the ventricle via the aortic valve into the aorta, and then to the systemic circulatory system (rest of body). 

How does the conduction system start?

The sino-atrial node transmits the impulse across the atria. 

What happens after the impulse reaches the atria?

The impulse travels across the atria via the intermodal tracts, Brachmann’s Bundle and atrioventricular node which delays the impulse for atrial contraction + ventricular filling.  

What happens after the AV node delays the impulse?

The impulse reaches the Bundle of His which splits the impulse in two into the left and right bundle branches. 

What happens after the impulse is split?

The impulse then reaches the base of the ventricles at the Purkinje fibres which causes a contraction from the apex of the heart upwards. 

Preload

Level of stretch of the ventricles before contraction, caused by blood returning and filling the heart (increased in heart failure and regurgitation of cardiac valves) 

Contractility

Strength at a given length of muscle, dependant of amount of calcium present

Afterload

Force that impedes ventricular contraction, caused by vessel pressure (increased in hypertension and vasoconstriction – leads to increased cardiac workload) 

Receptors during exercise 2 parts

Chemoreceptors detect increased carbon dioxide + lactic acid levels 

Baroreceptors detect increased stretch on vessel walls  

Receptors during rest 2 parts

Chemoreceptors detect increased oxygen and decreased lactic acid/carbon dioxide 

Baroreceptors detect a decreased stretch on vessel walls

Sympathetic nervous system during exercise 3 parts

Sympathetic release of adrenaline and noradrenaline 

Information is relayed to the cardiac control centre in the medulla oblongata 

Sympathetic nervous system increases stimulation of the sino-atrial node via the accelerator nerve to increase heart rate  

Parasympathetic nervous system during rest 3 parts

Parasympathetic inhibition of adrenaline and noradrenaline

This information is related to the cardiac control centre in the medulla oblongata 

Parasympathetic nervous system decreases stimulation of the sino-atrial node via the vagus nerve to decrease heart rate 

Preload during exercise

Preload increases resulting in more blood filling the ventricle before contraction increasing stroke volume 

Preload during rest

Preload decreases resulting in less blood filling the ventricle before contraction decreasing stroke volume 

Contractility during exercise

Contractility increases causing the heart muscle to have stronger contractions increasing stroke volume  

Contractility during rest

Contractility decreases causing the heart muscle to have weaker contractions decreasing stroke volume  

Afterload during exercise

Afterload increases which creates more cardiac resistance decreasing stroke volume 

Afterload during rest

Afterload decreases which creates less cardiac resistance increasing stroke volume 

Overall result during exercise

HR + SV increase - increasing Q

Overall result during rest

HR + SV decrease - decreasing Q

Blood pressure

Driving force that moves blood throughout the circulatory system and allows it to reach vital organs

3 primary functions of BP

Nutrient + oxygen delivery, waste removal and immune response 

Healthy adult BP

120 (systole)/80 (diastole)

End diastolic volume

Amount of blood in the ventricles before contraction 

End systolic volume

Amount of blood in the ventricles after contraction 

Ejection fraction

Percentage of EDV ejected during each contraction (70ml SV/120ml EDV) = 58% 

P wave

Indicates atrial depolarization

PR interval

Time between atrial and ventricular contraction

QRS complex

Reflects ventricular contraction

ST segment

Period between ventricular contraction and repolarization

T wave

Ventricular recovery

4 things an ECG can detect

Arrythmias

MIs

Structural problems

Electrolyte imbalances

4 modifiable risk factors for CVD

Smoking

High BP

Obesity

Excess Alcohol

4 non-modifiable risk factors for CVD

Age

Sex

Type 1 diabetes

Ethnicity

Atherosclerosis

Thickening of the arteries caused by a build-up of plaque in artery lining + vessel walls 

What can atherosclerosis cause? 2 parts

Angina/unstable

NSTEMI/STEMI

Percutaneous Coronary Intervention (PCI)

Using a balloon and stent to increase lumen of the narrowed artery + is non-invasive

Primary PCI (PPCI)

More specialised treatment for an active MI(STEMI) 

Coronary Artery Bypass Graft (CABG)

A graft is taken from the radial artery (arm), the saphenous vein (leg) or chest left internal mammary artery (LIMA) 

When is CABG performed?

When 3 main coronary arteries are blocked

What is used to create blood flow past the narrowing (CABG)

Blood vessels