Circulatory System Flashcards
The function of the Circulatory System: (6)
Transport system
- In relation to respiratory system, it transports O2 + CO2
- In relation to excretory system, it transports waste products
- In relation to digestive system, it transports nutrients + metabolites
- In relation to endocrine system, it transports hormones
- In relation to immune system, it transports defence mechanisms (white blood cells)
- Transports heat in form of energy (vasodilate + vasoconstrict)
3 components of the circulatory system:
BLOOD
HEART
BLOOD VESSELS
What is blood? (3)
- Primary transport medium
- About 5 L
- Red blood cells (erythrocytes) + White blood cells (leukocytes) + Platelets + Plasma = Blood
RBCs = have haemoglobin which carries Oxygen
WBCs = immune response, fight against infection
Platelets = blood clotting
Plasma = fluid portion to help transport ions, nutrients etc.
What are blood vessels? (4)
- Help connect different systems
- Arteries – carry blood to tissues
- Capillary bed – main sight of gaseous exchange
- Veins – carry blood towards heart
What is the heart?
- Muscular pump to propel blood through blood vessels
What is the open circulatory system? (2)
- Common in insects
- Has a pump with blood vessels that aren’t closed therefore the haemolymph (blood equivalent) bathes the cells/tissues and then gets sucked back into the pump by negative pressure so that cycle can continue again.
What is the closed circulatory system? (3)
- Humans
- Blood stays in the blood vessels
- Pressure helps nutrients, oxygen to bathe
cells via interstitial fluid
Single loop circulatory system/Single Circulation:
- One ventricle/one atrium
Double loop circulatory system/Double Circulation: (3)
- Blood is returned to the heart before going to the other tissues
- Advantage: Allows for extra pumping of blood, ensuring blood is pumped at high speed to tissues with high metabolic rates and so the blood is pumped at high pressure
- In Amphibians and reptiles, ventricle is not separated so there is mixing of blood which accounts for the different way in which they breathe
What is the pulmonary circuit?
Deoxygenated blood that returned to the heart is pumped to the lungs via the pulmonary artery (only
artery that carries deoxygenated blood). This pulmonary artery transports the blood to the lungs where it picks up the oxygen and then oxygenated blood is transported back to the heart via the pulmonary vein (only vein that carries oxygenated blood).
What is the systemic circuit?
Allows blood to flow to head, arms, digestive system, lower limbs. Oxygenated blood exits the heart via the major artery, aorta. Aorta splits into multiple arteries and further arterioles and then into arteries where gaseous exchange in the tissues occurs. These capillaries then join to form venules with deoxygenated blood and then into veins to return deoxygenated blood back to heart.
Blood flow in human circulatory system: (6)
- Deoxygenated blood returns from body into right atrium via vena cava.
- Deoxygenated blood flows from right atrium into right
ventricle and enter the Pulmonary circuit. - The deoxygenated blood enters the pulmonary artery and goes to lungs.
- In the lungs, CO2 is released, and oxygen is picked up making oxygenated blood, flowing to the left atrium via pulmonary vein.
- Oxygenated blood flows from left atrium into left ventricle and enter the Systemic circuit.
- The oxygenated blood enters the aorta and goes to body.
Blood flow in a foetal circulatory system: (2)
For foetus, it obtains all oxygen from placenta. The oxygen rich blood from placenta mixes with the venous blood returning to right atrium. Since lungs are non-
functional, it would be a waste of energy to send blood to lungs therefore blood is rerouted via a small whole
between the 2 atria called foramen ovale. Nearly 48% of
blood that comes into right atrium flows into left atrium.
Ductus arteriosus connects pulmonary artery to aorta to
reduce blood flow to non-functional lungs. 40% is routed via the ductus arteriosus to the rest of the body to deliver oxygenated blood to cells. Therefore only 11% of blood is sent to lungs so that lungs continue to grow.
As baby takes first breath, the change in pressure causes close in a valve over the foramen ovule to prevent mixing of blood. Smooth muscle around ductus arteriosus constricts, forming closure so that it becomes
a filament. This ensures blood flows back to lungs to form double loop system. If foramen ovale does not
close, lead to whole in the heart (ASD – arterial septal defect).
What are the differences between arteries and veins? (6)
Direction of blood, Blood content, Blood pressure, Valves, Wall and Lumen (central tube).
Blood vessels
Artery → _______ → capillaries → _______ → Veins
arterioles
venules
Both arteries and veins contain same 3 basic layers:
- Tunica intima = endothelium + loose connective tissue
- Tunica media = smooth muscle
- Tunica externa = collagen fibres
Fluid within the blood vessels has a different composition to the ______ fluid.
interstitial
Two opposing pressures control movement of fluid:
- Hydrostatitc/Fluid pressure – pressure exerted by blood
- Osmotic pressure (due to osmosis) – due to high content of proteins, cells etc in blood, fluid will driven back into the capillaries
If ______ pressure is higher than the _____ pressure, this can cause yoru solutes to be forced out of the blood vessels into the interstitial fluid.
hydrostatic
osmotic pressure
At the arterial end of the capillary, your
hydrostatic pressure __ osmotic pressure. This
leads to a ______ pressure, causing the fluid to
be foroced out into the interstitial fluid by
_______.
> positive
As the bood moves into the middle of the capillary, hydrostatic pressure lessons and hydrostatic pressure ___ osmotic pressure, leading to__________________.
=
no net movement of fluid
At the venous end, hydrostatic pressure ___
osmotic pressure which causes fluid to be
_______ back into the capillaries.
<
reabsorbed
(24 L) 80% fluid filtered out of arterial end is reabsrobed at the ______ end
(20 L). Excess 4 L is drained from______ system.
venous
lymphatic
What is the function of the lymphatic system? (2)
- Removal of excess interstital fluid that is not reabsrobed
- Filtrates interstitial fluid
Runs parallel to the lymphatic system.
Once excess _______ fluid drains into lymphatic capillaries, it is termed lymph. Lymphatic capillaries combine into collecting vessels which then are filtered through lymph _____ (site of lymphocyte multiplication). After filtering, lymph is returned to circulatory system via _____ _____ (subclavian vein) at the base of the neck.
interstitial
nodes
collecting ducts
What is Elephantiasis? (3)
- Enlargment of body region due to obstruction of lymphatic system
- A symptom of Lymphatic filariasis caused by a parasitic worm which damages the lymphatic system
- Prevents drainage of excess interstitial fluids
The Heart
- In ______ chest cavity
- Protected by ribcage and ______
- Central in thoracic cavity, slightly shifted to the left due to location of _____
- Central compartment of thoracic cavity = ________ (above diaphragm between lungs)
- Heart is surrounded by double membrane = _________ → filled with fluid which helps reduce friction by ______ heart with every heartbeat
thoracic
sternum
liver
mediastinum
pericardium
lubricating
How is blood circulated around the body? (5)
- Deoxygenated blood returns from head and arms via superior (from top) vena cava and the inferior (from bottom lower body) vena cava.
- Drain into the right atrium.
- Blood flows into right ventricle via atriaventricular valve. As ventricles contract, blood is pushed out through semilunar valve into pulmonary artery which splits into 2, one going to right lung and one to left.
- Blood offloads CO2 and picks up O2 and returns to left atrium via pulmonary veins.
- Flows through atriaventricular valve into left ventricle and as heart contracts, pushes blood out of a semilunar
valve into the great artery, aorta. There are 3 branched off the aorta. Top branches go to upper body and bottom aorta ends go to lower body.
What is the cardiac cycle? (3)
- Cardiac Diastole (0.4 s)
- Atrial Systole (0.1 s)
- Ventricular Systole (0.3 s)
What is cardiac diastole? (4)
- Relaxation between heart beats
- Atriaventricular valves are open
- Blood flows from great veins and pulmonary veins into the appropriate atrium and ventricle
- Heart is filling with blood
What is atrial systole? (2)
- Contraction of atria
- Blood is pumped from atria into ventricles
What is ventricular systole? (4)
- Contraction of ventricles
- Atriaventricular valves are closed
- Atria continue to receive blood
- Ventricular contraction forces the blood out into the
pulmonary artery + aorta trhough the semilunar valve
Valves of the heart
4 main valves → prevent backflow of blood during cardiac cycle
Include:
- 2 atrioventricular valves (AV)
Tricuspid valve on right side
Bicuspid/mitral valve on left side - 2 semilunar valves (SL)
Pulmonary valve (seperates right ventricle from pulmonary artery)
Aortic valve (seperates left ventricle from aorta)
Opening and closing of valves is a passive process that reacts to changes in blood ______.
pressure
What happens In the left side of the heart during diastole? (3)
- In diastole, blood flows from the left atria to left ventricle therefore the bicuspid valve is open.
- Your chordae tendineae are in low tension and are attached to relaxed papillary muscle.
- Aortic valve is closed
What happens in the left side of the heart during ventricular systole? (3)
- In ventricular systole, bicuspid valve closes to prevent back flow of blood into artery.
- Your chordae tendinae are now at high tension and your papillary muscles are contracted and hold the
atrioventricular valve so that they don’t push too back into the atria. - Aortic valve is forced open and blood flows into the aorta and pulmonary artery
Systole: ‘Lub’ S1 =
when AV valves close at the end of Atrial systole and start of Ventricular systole when blood is pushed into aorta + pulmonary artery
Diastole: ‘Dub’ S2 =
when semilunar valves close during diastole to prevent back flow of blood from arteries
Lub Dub Lub Dub
Heart murmur =
sound of blood pushing back through valves
Cardiac muscle =
myocardium
Has combined properties of skeletal + smooth muscle
What are Sarcomeres in cardiac muscle?
= actin + myosin filaments (for the contraction of muscles) → striated appearance
What are intercalated disks? in cardiac muscle?
→ connection between 2 connected muscle cells → tight junctions held together by desmosomes
What are gap junctions?
Also have gap junctions → communication → allows diffusion of ions a + for fast transmission of action potential → supporting the synchronized contraction of cardiac tissue
Action potential (tells cardaic muscle when to ______)
contract
Specialized cardiac muscle cells are used for _____ + _______ of action potential
Electrochemical gradient is measured in (mV)
conduction
initiation
How is the action potential initated?
Resting membrane potential is – in inside of cell. When channels open, sodium can move into the cells
which causes electrochemical gradient to become more + = depolarization → known as initiation of action
potential
What is repolarization?
Potassium channels open pumping ions out of cell, bringing membrane potential to – resting potential =
repolarization
Membrane potentials differ for the contractile muscle cells vs the ________ cells (specialized cardiac
muscle cells)
autorhythmic
For _______ muscle cells, there is a change in the membrane potential curve due to calcium ions to ensure no contraction is held for too long. So that it has long _______ period, not multiple action potentials coming in. Need muscle to relax fully.
contractile
refraction
What does 1% of cardiac tissue have?
1% of cardiac tissue has specialized cells that halep transmit electrical signals throughout the cardiac muscle
to allow contraction of muscle. These cells are not nervous tissue but specialized conducting fibres.
Sinoatrial (SA) node: (2)
- Located where the superior vena cava enters the right atrium
- Is a specialized cardiac tissue is the pacemaker as it initiates each heartbeat
Atrioventricular (AV) node: (3)
- Known as gate keeper
- Located between atria and ventricles
- As the signal has been transferred between the atria, the AV node delays the signal to give atria enough
time to complete their contraction
Atrioventricular bundle:
- As signal moves down ventricles it goes down bundle of His
The signal then goes down the ______ septum (muscle layer between ventricles) where the
specialized cardia tissue splits into 2 bundle branches, transmitting the signal to each ventricles
They the split into ______ fibres (fine root-like fibres) which transmit signal throughout ventricle, allowing
coordinated conduction
interventricular
purkinje
Process of the cardiac conduction system: (5)
- SA node fires, generating impulse
- Myogenic (heartbeat originates in heartbeat in its self)
- Autorhythmic (spontaneous depolarization generating action potential)
- The above allow heart to beat even when out of body
- Autonomic nervous system can increase or decrease the firing rate of SA node
- 60 – 100 impulse/minute - Action potential generated flows through atrial myocardium
- Initiates contraction of atria during atrial systole - AV node fires
- Delays signal allowing atria enough time to complete contraction
- A lot of connective tissue lie between atria and ventricles to prevent conduction to spread to ventricles - Spread of electrical signal down AV bundle
- Purkinje fibres distribute excitation through ventricular myocardium
- Have direct contact with myocardial cells to allow action potential to go through quickly between gap
junctions
Contraction of ventricles starts at _____ and squeezes blood out of ventricles.
apex
What happens if SA node fails to generate heartbeat?
AV node takes over and generates heartbeat at a much slower rate. At about 40 – 60 beats/minute.
What happens if If AV and SA node fail?
The bundle branches will generate the autorythmic impulse at about 20 – 40 beats/minute.
What is an electrocardiogram?
Electrical signals can be viewed via a Electrocardiogram (ECG/EKG). Helps us see the electrical activity of the heart. Shows all action potentials occuring.
Waves are named by alphabets starting from P.
What does each letter mean?
P – contraction of atrium
QRS – largest wave – contraction of ventricles
T – repolarization of membrane potential
Delay in signal caused by AV node is a ____ ___ known as PR segment.
Atrial depolarization coincides with the _____ wave therefore no separate wave show for atrial repolarization.
flat
QRS
How is this visualised on an electrocardiogram?
How is action potential shown on the electrocardiogram?
Action potential spreads from SA node to the AV node causing atrial systole
P – shows depolarization of atria inducing atrial systole
Flat line shows AV node slowing down action potential
QRS – action potential spreads through the bundle of His, bundle branches + Purkinje fibres causing ventricular depolarization which induces ventricular systole
As action potentials pass out the ventricles, ventricular diastole is induced → ventricular repolarization is shown by T
What is blood pressure? (2)
- The pressure exerted by the blood againts the walls of the blood vessels
- When you take your pulse, you feel the constriction/dilation of the blood vessels as the blood exerts pressure on the walls
In arteries:
- Elastic fibres in artery walls stretch + recoil
What happens in the arteries during Systole?
- Ventricles contract
- Semilunar valves open and blood flows into arteries (aorta + pulmonary artery)
- Arteries expand as blood moves through under high pressure
- Systolic blood pressure = pressure exerted by blood on artery walls following ejection of blood from
ventricles
Normal systolic blood pressure: 100 – 120 mmHg
In arteries:
- Elastic fibres in artery walls stretch + recoil
What happens in the arteries during diastole?
- Ventricles relax
- Semilunar valves close preventing back flow
- Elastic recoil of arteries sends blood forward having lower pressure on artery walls
- Diastolic blood pressure = pressure exerted by blood on artery walls following relaxation of ventricle
Normal diastolic blood pressue: 60 – 80 mmHg
When measuring blood pressure, first number is _____ and second is ______. Systolic is over diastolic.
systolic
diastolic
Aortic pressure graph:
What is pulse pressure?
Difference between systolic and diastolic =
pulse pressure
Why do capillaries have low pressure?
Network of capillaries have a large cross-sectional area because there are hundreds of small ones. This increase
in cross sectional area from the arteries causes the pressure in the capillaries to decrease.
Has a slow flow of blood allowing more time for gaseous exchange + exchange in nutrients.
Pressure changes in Systemic circuit vs Pulmonary circuit: (4)
- We normally consider the Systemic circuit but there is also the Pulmonary circuit which differ in pressure.
- Pulmonary circuit functions at a much lower pressure. There is a lower resistance to blood flow in the pulmonary circuit which comes from much less smooth muscle in the artery walls as well as much wider + shorter vein.
- Since the lungs are not too far from the heart, the blood does not need to travel at high pressure to reach the
lungs. - We do not want high pressure in the capillaries because a high blood pressure would result in fluid being pushed out of the blood vessels into the lungs which is unfavourable.
How to measure blood pressure?
- Upper left arm
- Person sitting up straight
- Blood pressure cuff should be at the level of heart
- Use a sphygmomanometer (column of mercury indicating pressure in mmHg)
- Pump the cuff and listen with stethoscope at brachial artery until you can no longer hear a pulse (artery
is completely blocked) - Once you can’t hear a sound, release the cuff slowly and listen for some sounds → Korotkoff sounds
(systolic is high enough to have blood squeeze into blood vessel) - First Korotkoff sound is your systolic blood pressure
- As you slowly release cuff, you hear a pulsing sound as blood is released slowly
- As pressure is released, Korotkoff sounds disappear, you hear a smooth whoosh sound, as no more
resistance to blood flow, which is our diastolic pressure
What is hypertension? (3)
– systolic blood pressure of 140 mmHg + or a diastolic blood pressure of 90 mmHg +
- You cannot diagnose hypertension from one measurement as high blood pressure can be a result of stress (white coat syndrome → being in a new place like a clinic, hospital can naturally elevate your BP)
- If after several readings, BP does not go down, then it can be classified as Hypertension
Hypertension + Obesity are 2 main risk factors leading to the development of __________ disease.
High blood pressure can damage blood vessels leading to ____________/
cardiovascular
atherosclerosis
What is Atherosclerosis? (10)
build-up of cholesterol plaque in the walls of arteries and the reduced blood flow to vital organs
1. Damage to endothelium, inner wall
2. Fats, cholesterol, and cellular waste products accumulate at the inner wall
3. Chemical reactions cause cholesterol molecules to oxidise
4. This initiates an inflammatory response as endothelial cells signal call for help
5. Monocytes from bloodstream travel to damage site which are then transformed into macrophages
which eat and digest cholesterol molecules
6. These macrophages accumulate to form foam cells and further form plaque
7. As plaque increases in size, arterial wall thickens and hardens
8. Smooth muscle cells travel to the plaque and form a cap
9. The cap can erode, and plaque can go downstream the bloodstream and contribute to clot formation
10. Leads to less blood flow potentially killing tissue
What happens if plaque ruptures or a clot forms in one of the arteries?
If a plaque ruptures or a clot form in one of the arteries that supply the heart with oxygen (coronary artery), it
may cause acute coronary syndrome which includes a range of conditions associated with sudden reduced
blood flow to the heart.
Blockage can cause unstable angina (chest pain) or a myocardial infarction (heart attack)
What is Acute Coronary Syndrome?
1 or more condition caused by blockage of blood flow
Cause of reduced blood flow is atherosclerosis when plaque forms. If plaque enters bloodstream can make
clot leading to coronary artery blockage.
Coronary artery spasm →
→ sudden temporary tightening of coronary artery due to stress, drugs, smoking etc.
Coronary artery dissection →
→ wall of artery separates blocking blood flow
Blockage leads to death of heart muscle leading to heart attack/myocardial _______.
Infarction
Symptoms of acute coronary syndrome: (6)
- Shortness of breath
- Dizziness
- Nausea
- Sweating
- Angina
- Arm pain
What are some treatments of acute coronary syndrome? (7)
- Oxygen therapy
- Aspirin to thin blood to prevent blood clots
- Thrombolytic drugs → clot busters can help break the clots
- Nitro glycerine + morphine can relax coronary arteries to relieve angina
- Beta blockers reduce speed of heart and its need for O2
- Coronary angioplasty → balloon tip catheter is inserted into blocked artery and inflated which then
leaves a mesh called a stent to force artery open - Coronary artery bypass graft → blocked areas of coronary artery are bypassed with veins or artificial
graft material
