Cardio-vascular System Flashcards
What is diastole?
Period when the ventricles and atria relax, allowing blood to flow into them
What happens during diastole?
- The atria relaxes, allowing blood to flow into them and the atrioventricular valves shut, preventing blood flow into ventricles
- Pressure builds in atria and the atrioventricular valves open so blood flows into relaxed ventricles
What is systole?
Period when the ventricles and atria are contracting, allowing blood to flow out of the heart
What happens during systole?
- The atria contracts, allowing remaining blood to flow into ventricles
- Ventricles contract which raises the blood pressure and forces open the semilunar valves which allows blood to be forced out of the aorta and PA
What is the definition of health?
A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity
What is the definition of fitness?
The ability to meet the demands of the environment
What is the definition of stroke volume?
Amount of blood ejected from the heart per beat
What is the definition of cardiac output?
Amount of blood ejected from heart per minute
What does stroke volume depend on?
Venous return
Elasticity of cardiac fibres
Cardiac tissue contractility
What is the definition of venous return?
The volume of blood returning to the heart via the veins - if venous return increases, SV increases
What is meant by the elasticity of cardiac fibres?
The stretch of cardiac fibres during diastole
What does Starling’s Law state?
The greater the venous return, the greater the stroke volume is.
What is anticipatory rise?
The increase in HR is caused by increased activity of the sympathetic nervous system causing the adrenal glands to release adrenaline into the bloodstream.
What is sub-maximal exercise?
Any activity that doesn’t exceed 85% max heart rate and causes CO to remain relatively unchanged
What is maximal exercise?
Cardiac output increases significantly in untrained individuals.
What is blood redistribution controlled by?
Th process of Vasomotor Control in the Medulla Oblongata
What do chemoreceptors pass on to the Vasomotor centre?
If they detect an increase in CO2 and blood acidity
Which nerves does the Vasomotor Centre stimulate?
The sympathetic nerves located in the walls of blood vessels
What do sympathetic nerves do?
They cause the arterioles and pre-capillary sphincters to constrict and dilate, decreasing blood flow to non-essential areas and increasing blood flow to the working muscles
What is the heart?
The heart is myogenic - generates its own impulses through its pacemaker - the SA node
When is haemoglobin fully saturated?
When 4 oxygen molecules are bound to it
When is haemoglobin partially saturated?
When only a few oxygen molecules are bound to it
What does the amount of oxygen binding to haemoglobin depend on?
The partial pressure in the blood
If PO2 is high, oxygen will readily combine with haemoglobin
What does myoglobin do?
Transports the oxygen dissociated from the haemoglobin to the mitochondria
What are the factors which affect haemoglobin saturation?
Decrease in blood activity
Increase in blood temperature
Increase in partial pressure of CO2 concentration
What is the order of the cardiac cycle?
- The Sino-atrial node sends an impulse across the atria which stimulates them to contract
- Diastole stage - The impulse arrives at the atrioventricular node, where it is delayed, allowing the ventricles to fill with blood
- The impulse then travels down the bundle of His which is in the septum
- Systole stage - The impulse travels along the Purkinje fibres which branch along the base of the right and left ventricles and cause the ventricles to contract
What is vascular shunt?
Controlled by the vasomotor centre in the Medulla Oblongata which alters the diameter of the arteries via the sympathetic nervous system
What is the SA node?
A small mass of cardiac muscle found in the wall of the RA that generates the heart beat
What is the AV node?
Relays the impulse between the upper and lower sections of the heart
What is the bundle of his?
A collection of heart muscle cells that transmit electrical impulses from the AV node via the bundle branches to ventricles
What are Purkinje fibres?
Muscle fibres that conduct impulses in the walls of ventricles
What do proprioceptors do?
Detect changes in movement and stimulate the inspiratory control centre to increase inspiration when moving
What do baroreceptors do?
Detect changes in blood pressure. When blood pressure drops, this initiates an increase in HR.
What do stretch receptors do?
Detect the stretch of the lungs which accompanies exercise and stimulates the expiratory control centre to increase expiration
What are pre-capillary sphincters?
They’re tiny rings of muscle located at the opening of the capillaries.
What do pre-capillary sphincters do?
- Aids blood redistribution by constricting or dilating
- When they constrict, the blood flow is restricted through the capillary
- When they dilate, blood flow is increased
- During exercise, the capillary networks supplying skeletal muscle will be dilated to increase blood flow and saturate the tissues with oxygen.