The Cardiovascular System 1.1 2 Flashcards
What is starlings law?
(summarised)
Increased venous return - Greater diastolic filling - cardiac muscle stretched - More force of contraction - increased ejection fraction
What is the ejection fraction?
The percentage of blood pumped out by the left ventricle per beat
An average value of 60% up to 85% following a period of training
What is the cardiovascular drift?
Cardiovascular drift is characterised by a progressive decrease in Stroke Volume & arterial blood pressure. Together with an increasing HR.
Occurs during prolonged exercise (after 10 mins) in a warm environment, despite intensity of exercise remaining the same
When does the cardiovascular drift usually occur?
10 minuets of prolonged exercise
What suggestions are there as to why the cardiovascular drift occurs?
- When we sweat, a portion of this lost fluid comes from plasma volume
- The decrease in plasma volume will reduce venous return & stroke volume
- HR again increases to compensate & maintain a higher cardiac output in attempt to create more energy & cool the body down
- To minimise this cardiovascular drift it is important to maintain high fluid consumption before, during & after exercise
What is coronary heart disease and how does it occur?
Coronary arteries supply oxygenated blood to the heart.
Disease is when the arteries become blocked or start to narrow because of the gradual buildup of fatty deposits (atheroma).
This process is called atherosclerosis.
Less oxygen can be delivered to the heart, so the heart will have to beat faster to provide the body with oxygen.
Causes: high blood pressure, high cholesterol, lack of exercise and smoking
Angina - chest pain that occurs when the blood supply through the arteries is restricted.
If a fatty deposit breaks off it can cause a blood clot and block the artery, this could lead to a heart attack.
Ways to prevent heart disease: regular exercise (maintains the flexibility of blood vessels ensuring good blood flow to the heart and body)
What is a stroke and how does it occur?
A stroke is where the blood supply to the brain gets cut off
Strokes are mostly caused by a blood clot – when the blood is too thick to fit through the blood vessels it causes a blockage and no blood at all can get through
Regular exercise can reduce your blood pressure which reduces a persons risk of having a stroke as high blood pressure means arteries are more likely to get clogged and cause a stroke
other factors that increase the risk of stroke is obesity, high blood pressure, diabetes
What is high blood pressure and how is it caused?
High blood pressure is the force exerted by the blood against the blood vessel wall.
This pressure comes from the heart as it pumps the blood around the body.
High blood pressure puts extra strain on the arteries and heart, and if left untreated it increases the risk of heart attack, heart failure, kidney disease, stroke or dementia.
Regular aerobic exercise can reduce blood pressure- I which can reduce the risk of a heart attack by up to 20%.
What are cholestral levels, HDL &LDL?
LDL (low density lipoproteins) - transport cholesterol in the blood to the tissues and are classed as bad cholesterol since they are linked to an increased risk of heart disease. Usually in over 60s due to a build up of this. Encouraged to eat things high in statins e.g. grapefruit. Also tablets help to reduce this.
HDL ( high density lipoproteins)- Transport extra cholesterol in the blood back to the liver where it is broken down. These are classed as good cholesterol since they lower the risk of developing heart disease.
Regular physical activity lowers LDL and increases HDL.
What are the two types of circulation in the vascular system?
Pulmonary- Deoxygenated blood from the heart to the lungs and oxygenated blood back to the heart
Systemic- Oxygenated blood to the body from the heart and then the return of deoxygenated blood from the body to the heart
What are the 5 different blood vessles in the pathway to the heart?
Heart - Arteries - Arterioles - Capillaries -Venules - Veins - Heart
Define blood pressure
The force exerted by the blood against the blood vessle wall
What is the formula for blood pressure?
Blood pressure= blood flow X resistance
What is systolic pressure?
- The pressure in the arteries when the ventricles are contracting
What is diastolic pressure?
- The pressure in the arteries when the ventricles are relaxing
Whats the venous return?
The return of blood to the right side of the heart via the vena cava
- Up to 70% of the total volume of blood is contained in the veins at rest.
- Therefore there is a large amount of blood that can be returned to the heart when needed
Pressure in the large veins is low – this makes it hard to return blood to the heart. The large lumen offers little resistance to blood flow. What are the venus return mechanisms needed?
- The skeletal muscle pump
- The respiratory pump
- Pocket valves
What is the skeletal muscle pump?
When muscles contract and relax they change shape.
This change in shape means that the muscles press on the nearby veins causing a pumping effect and squeeze the blood towards the heart.
This squeezes the blood back to the heart.
What is the respiratory pump?
When muscles contract during breathing in and out pressure changes occur in the thoracic and abdominal cavities.
This compresses nearby veins and assists blood flowing back.
What are pocket valves?
- Pocket valves close once blood has passed through to prevent blood flowing back.
(like normal valves)
What are some other factors that aid the venous return?
A very thin layer of smooth muscle in the walls of the veins - this helps squeeze blood back towards the heart
Gravity helps the blood return to the heart from the upper body
The suction pump action of the heart
What is the impact of blood pressure on venous return?
When systolic (contract) blood pressure increases, there is also an increase in venous return
When systolic pressure decreases there is a decrease in venous return
What is the impact of a pressure gradient between the right atrium and the vena cava on venous return?
Blood pressure in both the right atrium & peripheral veins is normally very low = low pressure gradient driving venous return.
Therefore even small changes in the right atrium or peripheral veins can cause a large change in the pressure gradient.
This will significantly affect the return of blood to the right atrium.
Explain the transportation of oxygen
When fully saturated haemoglobin will carry 4 oxygen molecules
This happens when partial pressure of oxygen in the blood is high
At the tissues, oxygen is released from the oxyhaemoglobin due to lower pressure of oxygen in the tissues – this is known as oxygen dissociation
In the muscles oxygen is stored by myoglobin – this loves oxygen and will store it for the mitochondria until it is used by the muscles
Mitochondria are the centres in the muscle where aerobic respiration takes place.
What is the vascular shunt mechanism?
The redistribution of cardiac output
(during exercise the skeletal muscles require more oxygen so more blood needs to be redirected in order to meet this increase in oxygen demand)
What is vasoconstriction and vasolidation?
Vasolidation- The widening of the blood vessels to increase the flow into the capillaries
Vasoconstriction - The narrowing of the blood vessels to reduce blood flow into the capillaries
How is blood flow controlled?
Both blood pressure and blood flow are controlled by the vasomotor centre which is found in the medulla oblongata of the brain.
Chemoreceptors detect chemical changes e.g. increased carbon dioxide and lactic acids.
They send a signal to the vasomotor centre which redistributes blood flow through
* Vasodilation
* Vasoconstriction
How does redirection of blood flow occur?
It occurs through stimulation of the sympathetic nerves located in the walls of the blood vessel
Redistribution of blood is important to…?
Increase the supply of oxygen to the working muscles
Remove waste products from the muscles, such as carbon dioxide and lactic acid
Ensure more blood goes to the skin during exercise
Direct more blood to the heart during exercise
What is aterio- venous oxygen difference? (A-VO2 diff)
The difference between the oxygen content of the arterial blood arriving at the muscles and the venous blood leaving the muscles.
What is the A-VO2 diff like at rest & at exercise?
At rest:
- The arterio-venous difference is low as not much oxygen is required by the muscles
During exercise:
- Much more oxygen is needed from the blood for the muscles so the arterio-venous difference is high
- This increase will affect gaseous exchange at the alveoli so more oxygen is taken in & more carbon dioxide is removed
- Training also increases the arterio-venous difference as trained performers can extract a greater amount of oxygen from the blood
What is ventilation?
- Getting air into and out of the lungs
What is external respiration?
Gaseous exchange between the lungs & blood
Transport of gases
What is internal respiration?
Exchange of gases between the blood in the capillaries and the body cells
What is cellular respiration?
- The metabolic reactions and processes that take place in a cell to obtain energy from fuels such as glucose
What suggestions are there as to why the cardio vascular drift happens?
- When we sweat, a portion of this lost fluid comes from the plasma volume (this makes the blood more viscous/thicker)
- This decrease in plasma volume will reduce venous return & stroke volume
What is the Bohr shift?
- When an increase in blood carbon dioxide & a decrease in pH results in a reduction of the affinity of haemoglobin for oxygen
What does the oxyhaemoglobin dissociation curve show?
- Helps us to understand how haemoglobin in our blood transports & releases oxygen
- The curve represents the relationship between oxygen & haemoglobin
During exercise why does the S-shaped oxygen dissociation curve shift to the right?
- S-shaped curve shifts to the right because when muscles require more oxygen, the dissociation of oxygen from haemoglobin in the blood capillaries to the muscle tissue occurs more readily
- This shift to the right is known as the Bohr Shift
- On tissues there is a low partial pressure of oxygen & a high partial pressure of CO2, so haemoglobin unloads at this point- Meaning that even more oxygen is avaliable to the tissues
What 3 factors are responsible for this increase in the dissociation of oxygen from haemoglobin?
- Increase in blood temperature- When blood & muscle temperature increases during exercise, oxygen will dissociate from haemoglobin more readily
- Partial Pressure of carbon dioxide increases- As the level of blood carbon dioxide rises during exercise, oxygen will dissociate faster from haemoglobin
- pH- More CO2 will lower the pH in the blood, a drop in blood pH will cause oxygen to dissociate from haemoglobin more quickly (Bohr Shift)
