1.1 The Cardiovascular System Flashcards
What is the cardiovascular system?
The body’s transport system which includes the heart and the blood vessels
How is the heart divided?
Divided into 2 parts by a muscular wall called the septum.
Each part contains 2 chambers - an atrium and a ventricle.
Which chamber is smaller and why?
Atria are smaller as all they do is push the blood down into the ventricles. This doesn’t require much force so they have thinner muscular walls.
Which chamber is bigger and why?
Ventricles have much thicker muscular walls as they need to contract with greater force in order to push blood out of the heart.
Which side of the heart is larger and why?
Left side is larger as it needs to pump blood all around the body, whereas right side pumps deoxygenated blood to the lungs which is closer.
What are the blood vessels of the heart?
Vena cava
Pulmonary vein
Pulmonary artery
Aorta
What is the role of the vena cava?
Brings deoxygenated blood back to the right atrium.
What is the role of pulmonary vein?
Delivers oxygenated blood to the left atrium.
What is the role of the pulmonary artery?
Delivers deoxygenated blood to the lungs.
What is the role of the aorta?
Delivers oxygenated blood to the rest of the body.
What are the main valves in the heart?
- Tricuspid valve
- Bicuspid valve
- Semi-lunar valve
Where are the valves located?
Tricuspid = between right atrium and right ventricle Bicuspid = between left atrium and left ventricle Semi-lunar = between left and right ventricles, pulmonary artery and aorta
What is the role of valves?
Regulate blood flow by ensuring it only flows in one direction. The open to allow blood to pass through, then close to prevent back flow.
Define cardiac conduction system
Group of specialised cells located in the wall of the heart which send electrical impulses to the cardiac muscle, causing it to contract.
How is the heart muscle described?
Myogenic - capacity to generate its own impulses
How does an electrical impulse travel?
- SAN
- Impulse spreads through the aria walls causing them to contract and force blood into the ventricles.
- Passes through AVN
- Ventricular systole begins
- Passes down through bundle of His
- Passes through purkinji fibres causing the ventricles to contract
Summarise the cardiac conduction system (SAABPV)
SAN Atrial systole AVN Bundle of His Purkinje fibres Ventricular systole
What are 2 neural control mechanisms?
Sympathetic system - part of the autonomic nervous system that speeds up HR
Parasympathetic system - part of the autonomic nervous system that decreases HR
What 2 parts make up the nervous system?
Central nervous system (CNS), and the peripheral nervous system
What makes up the CNS?
Brain and spinal chord
What makes up the peripheral nervous system?
Nerve cells
How are the CNS and peripheral NS controlled?
Co-ordinated by the cardiac control centre located in the medulla oblongata.
Define medulla oblongata
The most important part of the brain as it regulates processes that keep us alive such as breathing and HR
What stimulates the cardiac control centre?
Chemoreceptors, baroreceptors, proprioceptors
Define chemoreceptors
Found in the carotid arteries and aortic arch and they sense chemical changes.
Define baroreceptors
Contain nerve endings that respond to stretching of the atrial wall caused by changes in blood pressure. They establish a set point for BP.
Define proprioceptors
Sensory nerve endings in the muscles, tendons and joints that detect changes in muscle movement.
Memory tool for receptors
Chemoreceptors = increase in CO2 = increased HR
Baroreceptors = increase in blood pressure = decreased HR
Proprioceptors = increase in muscle movement = increased HR
Define adrenaline
Stress hormone that is released by the sympathetic nerves and cardiac nerve during exercise which increases HR
Define stroke volume
Volume of blood pumped out by the ventricles in each contraction
What does stroke volume depend on?
Venous return - if this increases, so does SV
Elasticity of cardiac fibres - the more they can stretch, the greater the force of contraction which increases ejection fraction (Starling’s Law)
Define ejection fraction
% of blood pumped out by left ventricle per beat
Define diastole phase
When the heart relaxes to fill with blood
Memory tool for Starling’s Law
Increase venous return = greater diastole = cardiac muscle stretched = more force of contraction = increased ejection fraction
Define cardiac output
Volume of blood pumped out by the ventricles per minute
How do you calculate cardiac output?
SV x HR
Define cardiac hypertrophy
Thickening of the muscular wall of the heart so it becomes thicker and stronger
Define bradycardia
A decrease in resting heart rate to below 60 bpm
What can a lack of exercise lead to?
Heart disease
High blood pressure
Increased cholesterol levels
What is cardiovascular drift?
During steady state exercise heart rate slowly climbs
When does cardiovascular drift occur?
During prolonged exercise (after 10 mins) in a warm environment.
Why does cardiovascular drift occur?
When we sweat, a portion of this lost fluid comes from plasma volume. This decreases venous return and stroke volume, so HR increases to compensate and maintain a higher cardiac output.
Define blood pressure
The force exerted by the blood against the blood vessel wall.
What is the difference between systolic and diastolic pressure?
Systolic - the pressure in the arteries when the ventricles are contracting.
Diastolic - the pressure in the arteries when the ventricles are relaxing.
Define venous return
The return of blood to the right side of the heart via the vena cava.
Describe Starling’s Law
During exercise, venous return increases. This means that if more blood is being pumped back to the heart, then more blood has to be pumped out, so stroke volume increases.
What are the venous return mechanisms?
- Skeletal muscle pump
- Respiratory pump
- Pocket valves
How does the skeletal muscle pump aid venous return?
When muscles contract and relax they change shape meaning muscles press on nearby veins. This causes a pumping effect which squeezes the blood towards the heart.
How does the respiratory pump aid venous return?
When muscles contract and relax during breathing, pressure changes occur in the thoratic (chest) and abdominal cavities. This compresses nearby veins and squeezes blood to the heart.
How do pocket valves aid venous return?
Prevent back flow
What happens to oxygen during exercise?
It diffuses into capillaries, 3% dissolves into plasma, and 97% combines with haemoglobin to form oxyhemoglobin
How is oxygen stored in the muscles?
By myoglobin
Define the Bohr shift
When an increase in blood CO2 and a decrease in pH results in a reduction of the affinity of haemoglobin for oxygen.
What 3 factors are responsible for the oxyhaemoglobin dissociation curve?
- Increase in blood temp - o2 dissociates more readily.
- Partial pressure of co2 increases - oxygen dissociates faster.
- pH - decrease in blood acidity causes o2 to dissociate more quickly.
Define vascular shunt mechanism
The redistribution of cardiac output.
Why should athletes not eat less than an hour before competition?
A full gut results in blood being directed to the stomach instead of the working muscles.
What is the difference between vasoconstriction and vasodilation?
Vasoconstriction - narrowing of blood vessels to reduce blood flow into the capillaries.
Vasodilation - widening of the blood vessels to increase blood flow into the capillaries.
