Circulatory system Flashcards
What is the function of the circulatory system
Works to carry oxygen, nutrients and hormones to cell, whilst removing waste products such as carbon dioxide
Does blood flow unidirectionally or bidirectionally
Unidirectionally
WHat does it mean by ‘humans have a closed circulatory system’?
Physically separated from the rest of the body
Consists of vessels and pumps (heart acts as a driver of fluid around the body)
What do arteries do
Carry blood away from the heart
What do veins do
Carry blood towards the heart
Whyy does blood flow continuously around the body
Because it needs to transport oxygen and other materials around the body
What are the 3 main types of blood vessels
Arteries, veins and capillaries
What do capillaries do
Capillaries are tiny blood vessels that transport blood, nutrients and oxygen to cells in your organs and body systems.
What are the key differences between the three main types of blood vessels
What is blood
Blood is considered a connective tissue made up of cellular elements, suspended in a fluid matrix. It makes up a quarter of ECF (blood and plasma)
It also acts as a buffer between cells and external environment
What is the main blood composition
92% water
7% protein
1% dissolved organic molecules such as lipids, glucose
What is erythropoiesis
Describes the process of blood formation
It is controlled by the glycoprotein erythropoietin (EPO) + some cytokines (which is largely produced by kidney)
What is the trigger for EPO release
Hypoxia (low oxygen levels). If it is like this, it triggers the bone marrow to produce more red blood cells
What is blood doping
It is used to improve athletic performance by artificially improving body’s ability to transport O2 to tissues/muscles
What are 3 common methods of blood doping
Blood transfusions
Injection of EPO
Injection of synthetic O2 carriers
What is the heart
It is the workhorse of the body. It generates a pressure to force blood continuously around the body. Composed predominantly of cardiac muscle
Explain the nature of the electrical activity in the heart
The SA node can begin the depolarisation. This means that the right atrium and the left atrium starts to depolarise. this signal then has to travel to the AV node which delays the signal transfer, and ultimately delays the contraction of the ventricles until atrium is free of blood. The charge then carries through the bundles of his which shifts depolarisation to the bottom of the heart. These purkinje fibres then spread the depolarisation back up to the top of the heart and also causes a contraction of the ventricles to shift blood up (with aortic valves closed).
Explain the process of the mechanical events of the heart
1) late diastole - both sets of chambers are relaxed and ventricles fill passively
2) Atrial systole - atrial contraction forces a small amount of additional blood into ventricles
3) Isovulmic ventricular contraction - first phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves
4) Ventricular ejection - as ventricular pressure rises and exceeds pressure in arteries, the semilunar valves open and blood is ejected
5) Isovolumic ventricular relaxation - as ventricles relax, pressure in ventricles falls. Blood flows back into cusps of semilunar valves and snaps them closed
The process then repeats itself
Explain the process of a red blood cell arriving at the right atrium through the heart
Red blood cells arrive in the right atrium through both the superior and inferior vena cava.
It then travels through the tricuspid valve into the right ventricle where it is then pumped through the semilunar valves to the pulmonary arteries which carry blood away from the heart to the lungs. The blood so far is deoxygenated
The oxygenated blood then returns from the lung through the pulmonary veins into the left atrium, which is then pumped through the bicuspid/mitral valve into the left ventricle. It is then pumped through the aortic semilunar valve towards the aorta which will then deliver oxygen rich blood to the rest of the body
What is stroke volume
It is the volume ejected by the heart for each contraction
Does our heart contract to maximum force? Why or why not
It rarely contracts to maximum force. At rest, after each beat, blood remains in the heart (around 65mL). This stops ventricular walls rubbing against each other as it can cause damage and also allows us to alter how much blood is ejected in the next heartbeat
What is the formula for cardiac output
CO = SV x HR
How can HR be altered by autonomic nervous system
By changes to depolarisation of autorhytmic cells
What are the different blood vessels that the blood passes through, in decreasing blood pressure order
Aorta (highest pressure)
Arteries
Arterioles
Capillaries
Venules
Veins
Vena Cava (least pressure)
What is the nature of blood flow in the body
From areas of high to low blood pressure
Is the arterial system under high or low blood pressure
High blood pressure
Is the venous system under high or low blood pressure
Low blood pressure
What does systole mean
Pressure in arteries when heart has contracted
What does diastole mean
Pressure in arteries when heart has fully relaxed
What is the blood pressure normally given as?
x/y mmHg
where x is the systolic pressure
y is the diastolic pressure
What is postural hypotension
It is when we don’t move our legs, and the blood thus cant return to the heart. This is because standing causes blood to “pool” in our feet.
If not enough blood is returning to the head, we faint to ‘rectify’ the problem
What are the 3 main mechanisms of exchange in capillaries
Movement between endothelium (diffusion)
Transcytosis (endocytosis and exocytosis of some vesicles o create temporary channels for liquid to move out)
Bulk flow
What is bulk flow
Bulk flow is the movement of a mass of fluid that is due to the presence of a pressure gradient.
Why is fluid lost from blood to interstitium when exchange occurs in capillaries
This is mainly due to bulk flow. At the arterial end, there is a higher hydrostatic pressure in the capillary leading to greater fluid loss on that end. Meanwhile, at the venous end, due to a lower hydrostatic pressure and higher osmotic pressure, more fluid is absorbed into the capillary. However, overall, there is more fluid loss in the arterial end than fluid gain in venous end, leading to a net loss of fluid into the blood
Filtration: Dominant at the arterial end due to higher hydrostatic pressure in the capillary.
Reabsorption: Dominant at the venous end due to lower hydrostatic pressure and relatively higher osmotic pressure.
What is the function of the lymphatic system in relation to the loss of fluid
Returns excess interstitial fluid and filters it before returning it back into the bloodstream
What gives the pulsing sensation when we place our fingers to an artery
When the heart empties and blood is put into arteries, it is like a ‘wave’, causing the arteries to expand, thus pushing the blood further, and causing the pulsing sensation
