1.1 Flashcards
What is the cardiovascular system’s function
It’s the body’s transport system, It delivers oxygen and nutrients to body tissues and gathers waste products and transports heat (a byproduct of respiration) to the skin’s surface
The 2 main components of the cardiovascular system
The heart and blood vessels
4 Chambers of the heart
The right and left atria and ventricles
Function of the atria
To pump blood down into the ventricles
Why atria have thinner muscular walls
All they have to do is pump blood into the ventricles
Why ventricles have thicker muscular walls
They have to contract with greater force in order to force the blood out of the heart
Why the left side of the heart has thicker muscular walls and is larger
It needs to pump the oxygenated blood all the way around the body
Function of the right ventricle
To pump deoxygenated blood to the lungs
The main blood vessels of the heart
Vena cava (inferior and superior), Pulmonary veins and arteries (left and right), Aorta
Function of the aorta
Carries oxygenated blood from the left ventricle to the rest of the body
Function of the vena cava
Brings deoxygenated blood from the body back to the right atrium
Function of the pulmonary vein
Delivers oxygenated blood from the lungs to the left atrium
Function of the pulmonary arteries
Carries deoxygenated blood from the right ventricle to the lungs
The 4 main valves in the heart
The tricuspid, bicuspid, aortic semilunar and the pulmonary semilunar valves
The function of valves
They regulate blood flow by allowing blood to pass through and then closing to prevent back flow
Location of the tricuspid valve
Between the right atrium and ventricle
Location of the bicuspid valve
Between the left atrium and ventricle
Location of the aortic semilunar valve
Between the left ventricle and aorta
Location of the pulmonary semilunar valve
Between the right ventricle and pulmonary artery
What is the septum
The wall dividing the left and right sides of the heart
What are the chordae tendineae
Your ‘heart strings’ - in your ventricles - from top to bottom
What is the cardiac conduction system
A group of specialised cells located in the wall of the heart
Function of the cardiac conduction system
It sends impulses to the cardiac muscle, causing it to contract, Ensures HR increases during exercise to allow working muscles to receive more oxygen
Define myogenic
The ability of the heart to generate its own impulses
Sequence of the Cardiac conduction system
SAN node, A trial systole, AVN, Bundle of HIS, Bundle branches. Purkinje fibers, Ventricular systole
What is the sinoatrial node/SAN/SA node
A small mass of cardiac muscle in the wall of the right atrium
Function of the SAN (the ‘pacemaker’)
It’ generates the heartbeat with an electrical signal which spreads through the walls of the atria of the heart (causing them to contract (atrial systole) and force blood into the ventricles) as a wave (of excitation - like a Mexican Wave)
The function of the AVN/AV node/atrioventricular node
It relays the impulse between the upper and lower chambers of the heart, It delays the transmission of the cardiac impulse for about 0.1 seconds to allow the atria to fully contract before the ventricles begin to contract
Location of the AVN
In the very centre of the heart
What is the Bundle of HIS
A collection of heart muscle cells located in the septum and branches out into 2 Bundle branches
Function of the Bundle of HIS and Bundle branches
They transmit the electrical impulse for the AVN to the ventricles
Define systole
When the heart contracts
What are Purkinje fibers
Smaller bundle branches which spread through the ventricle walls
Function of the Purkinje fibers
They conduct impulses throughout the walls of the ventricles causing them to contract (ventricle systole)
What is the neural control mechanism and what is its function
Involves the sympathetic and parasympathetic nervous systems and controls the rate at which cardiac impulses are fired by the SAN
What is the parasympathetic nervous system and what is its function
It’s a part of the autonomic nervous system that decreases Heart rate (HR)
What is the sympathetic nervous system and what is its function
It’s a part of the autonomic nervous system that stimulates the heart to beat faster (increases HR, SV and Q) because sympathetic nervous impulses are sent to the SAN by the brain and there’s a decrease in parasympathetic nerve impulses
What 2 parts is the nervous system made of
The central nervous system (CNS) and the peripheral nervous system
What does the CNS consist of
The brain and the spinal cord
What does the peripheral nervous system consist of
Nerve cells that transmit info to and from the brain (relay neurones)
What coordinates the 2 nervous sytems
The cardiac control centre in the medulla oblongata in the brain
What are the 3 main types of receptors that stimulate the cardiac control centre
Baroreceptors, chemoreceptors and proprioceptors
What are chemoreceptors and where are they found
They’re tiny structures in the carotid arteries (blood vessels that carry oxygen-rich blood to the head, brain and face and are located on each side of the neck) and aortic arch.
What is the function of chemoreceptors
To detect changes in blood acidity caused by an increase or decrease in the concentrations of oxygen and CO2 and levels of lactic acid
What are baroreceptors
They’re special sensors containing nerve endings.
Where are baroreceptors found
In tissues in the aortic arch + carotid arteries
What is the function of baroreceptors and how do they work
They respond to the stretching of the arterial wall caused by changes in blood pressure, They establish a set point and an increase above or a decrease below this point results in the baroreceptors sending impulses to the medulla oblongata. An increase in pressure causes an increase in stretch of the baroreceptor sensors and eventually results in decreased HR. A decrease in stretch causes an increase in HR. At the start of exercise, the set point increases as you don’t want your HR to slow down when going exercise.
What are proprioceptors
Sensory nerve endings
Where are proprioceptors found
Muscels + tendons
What is the function of proprioceptors and how do they work
They detect changes in muscle movement and body position. At the start of exercise, they detect an increase in muscle movement and send impulses to the medulla oblongata, which sends an impulse through the sympathetic nervous system to the SAN. When it causes the parasympathetic nervous system to stimulate the SAN, HR decreases.
What is the hormonal control mechanism
It’s the effect of hormones on HR such as the release of adrenaline
What is adrenaline
A stress hormone released by sympathetic nerves and cardiac nerve during exercise
The role of adrenaline
Causes an increase in HR by stimulating the SAN, which also increases SV and Q, means more blood is pumped to working muscles so they can receive more O2 for the energy they need
What is stroke volume (SV)
The volume of blood pumped out by the ventricles in each contraction, On average = 70ml at rest
What 3 factors affect SV
Venous return (VR), Elasticity of cardiac fibres, contractility of cardiac tissue (myocardium)
Starling’s Law
More elasticity of cardiac fibres means more blood in heart, means more force of contraction, increases ejection fraction
Ejection fraction
The percentage of blood pumped out by the ventricle per beat (usually 60% but can be 85% after training)
Elasticity of cardiac fibres
The amount they stretch during the diastole phase
Heart Rate (HR)
The no. of times the heart beats per min ( on average is 72 at rest)
What is cardiac output (Q)
The volume of blood pumped out by the heart’s ventricles per min
Cardiac output formula
Q=SVxHR
2 factors affecting cardiac output
HR and SV
HR in response to exercise
It increases in direct proportion to exercise intensity (until a certain point - max HR)
Maximal exercise example
Sprinting
Sub-maximal exercise example
Jogging
How HR responds to exercise (the sequence)
Anticipatory rise before exercise due to adrenaline, Sharp rise (due mainly to aerobic work), Sharp rise (due to anaerobic exercise) OR Steady state (as oxygen demand is met), Rapid decline (after exercise), Slower recovery (as body systems return to resting levels and the waste products are removed- E.g. lactic acid)
Cardiac hypertrophy
The thickening of the muscular wall of the heart
What causes cardiac hypertrophy
Regular aerobic exercise
Benefits of cardiac hypertrophy
The heart becomes bigger and stronger, Larger SV and Q can be reached, Bradycardia, Diastolic volume of the ventricles increases
Bradycardia
A decrease in resting HR below 60BPM
Benefit of bradycardia
Oxygen delivery to the muscles improves as there’s less oxygen needed for contractions of the heart
Cardiac output in response to exercise
It increases as the intensity of exercise increases until maximal intensity is reached and then it plateaus
Comparison of cardiac output between a trained and non trained person at rest
It’s the same (but the HR of the untrained person is higher)
Comparison of cardiac output between a trained and non trained person during maximal exercise
The trained person has a higher cardiac output (as they have the same max. HR but a larger SV)
Benefit of higher cardiac output
You can transport more oxygen to the working muscles
How distribution of blood flow changes during exercise
A higher proportion of blood passes to the working muscles and less passes to organs like the intestines (as it’s less in demand) but the amount of blood going to the brain and kidneys stays the same
Stroke volume in response to exercise
It increases as intensity increases up to 40-60% max. effort then it plateaus and begins to fall
A reason why increase in SV plateaus at 40-60% effort
At a higher HR, there’s a shorter diastolic phase (the ventricles don’t have as much time to fill up)
(Coronary) Heart disease (CHD)
When coronary arteries (supplying blood to the heart) become blocked or narrow due to a gradual build-up of atheroma
Atheroma
A fatty deposit found in the inner lining of an artery
Atherosclerosis
When arteries harden and narrow as they become clogged up by atheroma
Causes of atherosclerosis
High blood pressure, high cholesterol levels, lack of exercise and smoking
Angina
Chest pain that occurs when the blood supply, through the coronary arteries, to the cardiac muscle is constricted
Cause of a blood clot
If a piece of atheroma breaks off in the coronary artery, resulting in a blockage
Causes of a heart attack
When the supply of oxygenated blood to the heart muscle is cut off (a blood clot in the coronary arteries)
Benefits of regular exercise on the cardiovascular system
A healthy and efficient heart (increased SV due to stronger and bigger heart), It maintains the flexibility of blood vessels - ensures good blood flow, normal blood pressure and low cholesterol levels
The recommended minimum of moderate exercise per week E.g. Brisk walking
150 mins
Blood pressure
The force exerted by the blood against the blood vessel wall (due to the heart pumping), Blood flow x resistance
Consequences of high blood pressure
Increased strain on the heart and arteries - causing increased risk of heart attack, heart failure, kidney disease, strokes and dementia
How to reduce blood pressure
Regular aerobic exercise
The effect of regular aerobic exercise on blood pressure and the risk of heart disease
It lowers systolic and diastolic blood pressure by up to 5-10 mmHg which reduces the risk of heart disease by up to 20%
Types of cholesterol
LDL (low density lipoproteins - ‘bad’) and HDL (high density lipoproteins - ‘good’)
The role of LDL
It transports cholesterol in the blood to the tissues
Why is LDL ‘bad’
It’s linked to an increased risk of heart disease
The role of HDL
It transports excess cholesterol in the blood back to the liver where it’s broken down
Why is HDL ‘good’
It lowers the risk of developing heart disease
The effect of regular physical activity on cholesterol levels
It lowers levels of LDL and significantly increases levels of HDL
A stroke
When the blood supply to the brain is cut off causing damage to brain cells which start to die
Consequences of a stroke
Brain exercise injury, disability and death
Types of stroke
Ischaemic strokes (the most common) and haemorrhagic strokes
An ischaemic stroke
Occurs when a blood clot stops blood supply to the brain
A haemorrhagic stroke
Occurs when a weakened blood vessel supplying blood to the brain bursts
How regular exercise reduces risk of strokes
It helps you to lower your blood pressure and maintain a healthy weight which can reduce your risk of stroke by 27%
Steady state
Where the athlete is able to meet the oxygen demand with the oxygen supply so HR remains constant
Cardiovascular drift
When HR slowly climbs during ‘steady state’, It’s a progressive decrease in SV and arterial blood pressure and a progressive rise in HR
When does cardiovascular drift occur
During prolonged exercise (after 10 minutes) in a warm environment with a constant exercise intensity
Why cardiovascular drift occurs
When we sweat, we lose fluid volume, some of which is our plasma volume, which reduces venous return (VR) and SV - means HR increases to compensate and maintain a higher cardiac output to create energy to cool you down
How to minimise cardiovascular drift
Maintain high fluid consumption before and during exercise
Types of circulation
Pulmonary (lungs) and systemic (body)
Sequence of blood vessels
Arteries, arterioles, capillaries, venules, veins
Features of veins
Blood is at a low pressure, Valves, Wide lumen, Thin muscle/elastic tissue layers
Features of arteries
High pressure blood, Wide muscle/elastic tissue layer, Smooth inner layer, Small lumen
Features of capillaries
Only wide enough for one red blood cell to pass through - slows down blood flow and allows exchange of nutrients with the tissues by diffusion
Impact of (systolic) blood pressure on blood flow + VR
Higher (systolic) blood pressure means higher blood flow + VR
Systolic (blood) pressure
The pressure in the arteries when the ventricles are contracting
Diastolic (blood) pressure
The pressure in the arteries as the ventricles contract
Where blood pressure is measured
At the brachial artery in the upper arm
A typical resting blood pressure
120/80 mmHg (mm of mercury)
What determines blood pressure
The (type of) blood vessel and the distance from the heart
How distance from the heart affects blood pressure
Further from the heart means lower blood pressure
Why venous return (active) mechanisms are needed
Low blood pressure in the veins (+ a low pressure gradient due to low venous blood pressure + right atrial blood pressure) makes it difficult to return blood to the heart + their large lumen offers little resistance to blood flow, During exercise, extra VR mechanisms are needed to meet the increased oxygen demand + because HR increases
Venous return
The return of blood to the heart via the vena cava,The percentage of our total volume of blood contained in the veins at rest
The percentage of our total volume of blood contained in the veins at rest
70
What is the benefit of having lots of blood contained in the veins at rest
It can be returned to the heart when needed, such as in exercise (venous return increases)
Starling’s law
If venous return (VR) increases, the heart contracts with greater force, which increases ejection fraction + SV (means that, normally, VR = SV)
Venous return mechanisms
The skeletal muscle pump, the respiratory pump, pocket valves (there’s also smooth muscle, gravity and the suction pump action of the heart)
The skeletal muscle pump
As muscles contract and relax, they change shape and press on nearby veins - causes a pump effect - squeezes blood to the heart
The respiratory pump
When muscles contract + relax during breathing, pressure changes occur in the thoracic (chest) and abdominal (stomach cavities) - causes nearby veins to be compressed - assists venous return
Pocket valves
They ensure blood flows in one direction + prevent backflow by closing after they’ve allowed blood through
Smooth muscle (as a venous return mechanism)
It’s located in the veins as a very thin layer + it helps squeeze blood back to the heart
Gravity (as a venous return mechanism)
It aids VR from the upper body
Why it’s important to maintain VR during exercise
It ensures skeletal muscles are receiving enough oxygen to meet the demands of exercise
The VR mechanisms used at rest
Valves + smooth muscle
Why the respiratory pump and skeletal muscle pump are effective during exercise
Our muscles are constantly contracting and our breathing is elevated
Why it’s important to maintain VR mechanism after exercise
It avoids blood pooling (blood collecting in the veins)
Why an active cool down is important (relating to VR mechanisms)
It keeps the skeletal muscle pump and respiratory pump working
The pressure gradient
It’s (mean systemic) venous pressure minus the right atrial pressure
Factors affecting VR
The pressure gradient and venous resistance
Why the pressure gradient is volatile
Venous blood pressure right atrial pressure are normally both low - so small changes can really affect the pressure gradient - affects VR (e.g. during inspiration - small changes in blood pressure between the atria + abdominal cavity largely increases the pressure gradient driving VR from the peripheral circulation (circulation to + from your extremities) to the right atrium)
The key role of oxygen during exercise
It is involved in energy production (from respiration - which we use during exercise), during exercise, it diffuses into the capillaries supplying the skeletal muscles; 3% dissolves into plasma + 97% combines with haemoglobin to form oxyhaemoglobin
Plasma
The fluid part of blood (mainly water) that surrounds blood cells + transports them
Haemoglobin
An iron-containing pigment found in red blood cells, which combines with oxygen to form oxyhaemoglobin. When fully saturated, it will carry 4 oxygen molecules - occurs when (partial) pressure of oxygen in the blood is high e.g. in the alveolar capillaries of the lungs
Myoglobin (‘muscle haemoglobin’)
An iron-containing muscle pigment in slow-twitch muscle fibres which has a higher affinity for oxygen than haemoglobin. It stores the oxygen in the muscle fibres for rapid use during exercise. it has a high affinity for oxygen + will store the oxygen for the mitochondria until it’s used by the muscles
Mitochondria
Often referred to as the ‘powerhouse’ of the cell as respiration + energy production occur there. They are where aerobic respiration occurs within muscles
Oxyhaemoglobin dissociation
Oxygen is released (at the tissues) from oxyhaemoglobin (and goes to the tissues) due to the low (partial) pressure of oxygen that exists there
The oxyhaemoglobin dissociation curve
Helps us understand how haemoglobin in our blood transports + release oxygen showing the relationship between the partial pressure of oxygen (in tissues + the lungs) and he % saturation of haemoglobin with oxygen. Higher partial pressure means a higher % saturation of haemoglobin
How oxyhaemoglobin dissociation varies between rest and exercise (in the tissues)
At rest, haemoglobin only gives up 23% of its oxygen to muscles (so is no longer fully saturated) but this % increases during exercise as the demand for oxygen increases from working muscles so the dissociation of oxygen from haemoglobin in the blood capillaries to the muscle tissue occurs more readily
The Bohr shift
When an increase in blood CO2 + a decrease in pH results in a reduction of the affinity of haemoglobin for oxygen (the shift to the right on the graph showing the effect of partial pressure of oxygen (mmHg) on the % saturation of haemoglobin with oxygen - an ‘s’ shaped graph)
Factors responsible for the increase in the dissociation of oxygen from haemoglobin (means more oxygen is available for working muscles)
Increase in blood temperature, Increase in partial pressure of CO2, Decrease in blood pH (due to more CO2) causes the Bohr shift
Vascular shunt mechanism (shunting)
The redistribution/redirecting of blood flow (cardiac output) to areas where it’s most needed (e.g. redirecting more blood to working muscles during exercise to meet the increased oxygen demand
The effect of exercise on blood distribution
During exercise, blood supply to the intestines, kidneys, skeleton, brain and skin increase (from 20-25%, 20%, 3-5%, 15% and 4-5% to 3-5%, 2-4%, 0.5-1%, 3-4% and 1-2% respectively) and blood supply to skeletal muscle increases from 15-20% (about 0.75 of the 5 litres (cardiac output) per min) to 80-85% (about 20 of the 25 litres cardiac output per min) but the blood supply to the cardiac muscle remains the same
Why performers should ensure they leave an hour between eating and competing
A full gut would mean more blood being directed to the stomach instead of the working muscles, which would mean that the muscles would have less of an oxygen supply (as blood flow to the brain must remain constant to ensure brain function as the brain needs oxygen for energy and the heart requires a good oxygen supply so it can faster + blood goes to the skin as energy is needed to cool the body down), which would have a detrimental effect on performance
What controls blood pressure and blood flow (by redistribution of blood)
The vasomotor centre, located in the medulla oblongata of the brain, which is stimulated by the different types of receptors
How the vasomotor centre redistributes blood
Through vasodilation + vasoconstriction (+ the stimulation of sympathetic nerves in the walls of the blood vessels)
Vasodilation
The widening of the blood vessels to increase the flow of blood into the capillaries e.g. in the arterioles supplying working muscles during exercise to meet the oxygen demand
Vasoconstriction
The narrowing of the blood vessels to reduce blood flow into the capillaries e.g. in the arterioles supplying non-essential organs (e.g. the intestines and liver) during exercise
How stimulation of sympathetic nerves affects blood flow
When it increases, it causes vasoconstriction + when it decreases, it causes vasodilation
Pre-capillary sphincters
They aid blood distribution, They’re tiny rings of muscle located at the opening of capillaries, When they contract, they restrict blood flow through the capillary + when they relax - they increase blood flow e.g. during exercise - capillary networks supplying skeletal muscle will relax pre-capillary sphincters to increase blood flow + saturate the tissues with oxygen
Why redistribution of blood is important
It increases the oxygen supply to working muscles, It removes waste products from muscles, such as CO2 + lactic acid, It ensures more blood goes to the skin during exercise to regulate body temperature + get rid of heat through radiation, evaporation + sweating,It directs more blood to the heart as it’s a muscle - so requires more oxygen during exercise
Arterio-venous difference (A-VO2 diff)
The difference between the oxygen content of the arterial blood arriving at the muscles and the venous blood leaving the muscle
How arterio-venous difference varies
It’s low at rest as not much oxygen is required by the muscles but it’s high during exercise as much more oxygen is needed from the blood for the muscles
How changes in arterio-venous difference affect gas exchange at the alveoli
If it increases, more oxygen is taken in and more carbon dioxide is removed
How training affects arterio-venous difference
It increases with trained athletes as they can extract a greater amount of oxygen from the blood
