Cardiovascular System Flashcards
what are the three layers of the heart wall?
- EPIDCARDIUM
outer protective layer - MYOCARDIUM
muscular middle
layer
can undergo cardiac
hypertrophy - ENDOCARDIUM
thin inner layer
the cardiovascular system is composed of three main parts…
- the heart
- the blood vessels
- the blood
the main functions of the cardiovascular system (3)
- transport of nutrients and removal of waste products
- blood cell production
- thermoregulation
why is the heart known as a double pump system? (3)
- because it has two circuits that are constantly at work
- the pulmonary circuit carries deoxygenated blood to the lungs and oxygenated blood back to the heart
- the systemic circuit carries oxygenated blood to the body tissues and deoxygenated blood back to the heart
the conduction system (4)
SINOATRIAL NODE
- the heart’s natural pacemaker
- sends an electrical signal that tells the heart to beat.
- this signal starts in the upper right part of the heart and allows the atria to fill with blood
ATRIOVENTRICULAR NODE
- after the signal from the SA node causes the atria to contract, the AV node slows the signal down slightly before sending it to the ventricles
- this delay allows the atria to empty fully before the ventricles contract
BUNDLE OF HIS
- the electrical signal travels from the AV node to the bundle of His, which splits into two branches. one for each ventricle.
PURKINJE FIBRES
- spread the electrical signal throughout the ventricles
- this causes them to contract and pump blood out of the heart
how does the SA node generate its own electrical signals? (2)
- it receives messages from the PNS and the SNS to adjust the heart rate, either by increasing it or decreasing it.
- the cells within the SA node are classed as ‘self-excitable’
define heart rate
the number of times at which the heart beats per minute
define bradycardia
a decrease in resting heart rate to below 60 BPM
define stroke volume
the volume of blood pumped out of the left ventricle per beat
what is the average stroke volume at rest?
70 ML
how is stroke volume determined? (3)
-
venous return
- if the venous return increases, stroke volume will also increase -
elasticity of the cardiac fibres
- the degree of the stretch during the diastole phase
- the greater the degree of stretch = greater force of contraction = greater SV -
contractility of the cardiac tissues
- the greater the contraction of cardiac tissues = greater force of contraction = greater SV
define ejection fraction
the percentage of blood pumped out of the left ventricle, per beat
define venous return
the volume of blood returning to the heart via the veins
list the five mechanisms of venous return
- pocket valves
- skeletal muscle pump
- respiratory pump
- smooth muscle
- gravity
pocket valves (3)
- located in the veins
- prevent the backflow of blood
- helps blood move in one direction (towards the heart)
skeletal muscle pump (3)
- during upright posture
- skeletal muscles compress underlying veins and contract them
- this increases blood flow back to the heart
respiratory pump (4)
- during inspiration, the diaphragm moves down
- this expands the thoracic cavity; decreases intra-thoracic pressure; expands the lungs
- change in pressure is transmitted across the walls of the heart
- this lowers right atrial pressure, facilitating venous return
smooth muscle (2)
- smooth muscle undergoes vasodilation and vasoconstriction
- through this widening and narrowing of the internal diameter, stroke volume can be increased
gravity (3)
- blood from the upper body is aided in its return by gravity
- when stood up, the blood naturally flows to the lower extremities
- therefore, blood in the lower body has to work against gravity to return to the heart
define cardiac output
the volume of blood pumped out of the left ventricle, per minute
what is the average cardiac output at rest?
5 L
what is the equation for cardiac output?
HR (heart rate) x SV (stroke volume)
what are the changes in heart rate during exercise? (3)
- heart rate increases
- how much it increases depends on the intensity of the exercise
- increase in HR is directly proportional to exercise intensity
what are the changes in stroke volume during exercise? (4)
- stroke volume increases as exercise increases
- only increases until around 40-60% of maximum intensity
- after this SV begins to drop off slightly
- this is because the duration of the diastole phase decreases, meaning the heart isn’t pumping out as much blood per contraction.
what are the changes in cardiac output during exercise? (3)
- increases
- because the cardiac muscle (myocardium) can get physically bigger and stronger
- this means more blood can be pumped out the left ventricle, per beat and therefore per minute
describe and explain the heart rate response during maximal exercise (5)
- before exercise starts, there is an anticipatory rise due to the secretion of adrenaline, which stimulates the sinoatrial node to make the heart contract faster and stronger
- when exercise begins, there is a sharp rise in heart rate due to mainly anaerobic work (because at this time, there isn’t a sufficient amount of oxygen for aerobic work)
- towards the end of exercise, the heart rises more due to maximal workloads stressing the anaerobic system
- when exercise ends, there is a rapid decline in heart rate as soon as the exercise stops, because there is a decrease in the demand for oxygen by the working muscles
- after exercise, there is a slow recovery as the body systems return to resting levels
where is the cardiac control centre found?
in the medulla oblongata of the brain
how many sub-divisions does the cardiac control centre have?
TWO
- sympathetic nervous system
- parasympathetic nervous system
sympathetic nervous system (2)
- speeds up heart rate via the accelerator nerve
- releases the hormones epinephrine and norepinephrine
parasympathetic nervous system (2)
- slows down heart rate via the vagus nerve
- releases a hormone called acetylcholine
what happens to the SNS and PNS during rest and during exercise? (3)
- at rest, the PNS is in control of heart rate
- at the beginning of exercise, your body removes the parasympathetic stimulation, which enables the heart rate to gradually increase
- as exercise increases in intensity, the sympathetic nervous system becomes more dominant and takes control of heart rate
list the three ways in which the cardiac control centre regulates heart rate
- neural control
- hormonal control
- intrinsic control
neural control (3)
- involves receptors detecting changes in the body as a result of increased physical activity
- they send messages to the CCC, and in turn the ANS sends a message to the SA node
- this will either be done via the accelerator nerve or the vagus nerve
list the four types of receptors that detect change during physical exercise
(P C B T)
proprioceptors
chemoreceptors
baroreceptors
thermoreceptors
proprioceptors (2)
- pick up movement within the joints and muscles
- increased intensity = increased amounts of movement
e.g. muscle spindle
chemoreceptors (3)
- pick up chemical changes, such as lowered pH in the blood and a decrease in oxygen
- increase in intensity = increase in CO2 and lactic acid
- found in : muscle tissue, the aorta, the carotid artery
baroreceptors (3)
- pick up changes in blood pressure
- increase in intensity = increased blood pressure
- found in: the aorta, the carotid artery
thermoreceptors (3)
- pick up changes in body temperature and muscle temperature
- increase in intensity = increased body temperature
- found in: the skin, skeletal muscle, and the liver
hormonal control (4)
- before and during exercise, adrenaline and noradrenaline is released into the blood stream
- these hormones act directly on the SA node, stimulating an increase in HR
- both also aid the redistribution of blood to the muscles through vasodilation and vasoconstriction
- when intensity begins to drop, the hormone acetylcholine takes over to lower HR
intrinsic control (2)
- the heart internally controlling itself
- two factors to consider:
TEMPERATURE - increased temp of cardiac muscle = sped up nerve impulses = increased HR
STARLING’S LAW - as venous return increases, so does SV
