The cardiovascular system Flashcards
average heart rate of an adult
70 beats per minute
structure of the heart; apex & base
apex of the heart; point area at the BOTTOM, which sits slightly to the left
base of the heart; area at the TOP, where big blood vessels are attacted
location of the heart?
within the thoracic cavity (chest) in a space between the lungs. the apex of the heart points slightly to the left. concave area of the left lung (two lobes) provides space for this.
heart sits behind the sternum (breastbone) which protects it, along with the pericardial sac which contains pericardial fluid (lubrication for movement).
what is pericardectomy?
removal of the pericardial sac, which can be due to pericarditis. inflammation of this sac (pericarditis) can cause excess fluid to be produced and surround the heart, putting pressure on the organ and restricting its pumping function- tamponade.
chambers of the heart
there are four chambers; two atria & two ventricles
Left Atrium (LA) - upper left Left Ventricle (LV) - lower left
Right Atrium (RA) - upper right Right Ventricle (RV) - lower right
heart valves
Right atrio-ventricular (AV/tricuspid) valve
- lies between the Right atrium and Right ventricle at the bottom.
- blood going from the atrium down to the RV has to pass this AV valve
- valve has three flaps (tri-cuspid)
Left atrio-ventricular (bicuspid/mitral) valve
- lies between the Left atrium & Left ventricle
- blood going from the left atrium down to the left ventricle has to pass this AV valve
- this valve has two flaps (bi-cuspid)
Aortic Valve
- found between the Left ventricle & entrance to the aorta
- blood is pumped UP from the LV to the Aorta, then out to the body
Pulmonary Valve
- found between the Right ventricle & entrance to the pulmonary artery
- blood is pumped UP from the RV to the Pulmonary artery, then to the lungs
valve flaps notes;
pressure from heart contraction during the cardiac cycle and movement of blood puts pressure on flaps to open & close
the flaps being attached to the wall of the ventricle by tough cords stops them from being turned inside out during these processes of pressure
what does the heart wall do and what is it made of?
the heart wall allows the heart to beat and pump blood; there are three layers and a surrounding sac
pericardial sac
-outer most layer which protects the heart and wraps around the organ
epicardium
-similar to the epidermis. space between epicardium and pericardium (pericardial layer) is is filled with the pericardial fluid
myocardium
- found between epicardium and endocardium
- thickest of the layers
- ‘myo’ means muscle and this layer is therefore the muscle of the heart
- most of heart wall is made from muscle tissue
endocardium
-inner most layer which lines the chambers of the heart
cardiac muscle tissue points;
muscle tissue in the heart is cardiac muscle tissue. this is only found in the heart within the body and here is where cardiac muscle cells exist.
cardiac muscle cell points;
- striations give cardiac muscles their branched patterned appearance, allow cardiac muscle cells to function and provide attacthment points.
- branched cells, meaning they branch to meet and connect to other neighbouring cardiac muscle cells
- where these two cells meet, there is a structure called intercalated disc which help to bind these cardiac cells together
- intercalated discs bind myocytes together both mechanically but also electronically. as each cell becomes electrical activated, the electrical signal passes through the branches, the discs and then the neighbouring cell- this allows heart muscles to work effectively and the heart to contract.
two names for cardiac muscle cells?
myocardial cells
myocytes
how heart valves work;
pressure from the blood build-up makes the valves open/close.
when the atrium contracts, it squeezes this chamber’s blood, causing a pressure build-up and the AV to open
when this happens, blood in the RA is squeezed into the RV. once filled, this valve will close due to release of pressure from the blood. this chamber then contracts, squeezing the blood and increasing pressure on the next valve.
what are intrinsic & extrinsic factors?
intrinsic;
-processes controlled by the heart itself and that trigger each contraction. (processes that trigger the beat of the heart come from within the heart).
extrinsic factors;
-that come from outside the heart, which modify and adjust the heart’s activity. meaning; although the heart can can set its won rhythm, outside factors can adjust this.
what is the heart’s conduction system?
the network of nodes, cells and signals that control the heart’s heartbeat
what is the SA node?
where is is located?
how active is it in one minute?
what does it do?
also known as the heart’s natural pacemaker.
the Sino-Atrial Node is located in the RA and becomes spontaneously active roughly 70 times every minute.
its cells generate an electrical impulse without outside help (if all NS supply to the heart was removed; the heart would still beat, as the NS can modify the heartbeat but not trigger it).
when the SA node becomes electrically active, this activity quickly spreads through cardiac muscle in the heart’s wall of the atria (this is assisted by the myocardial cells and their intercalated discs).
this wave of electrical activity spread through the myocytes causes them to contract, and therefore the atria to contract, causing the pumping of blood into the ventricles.
cardiac skeleton
a sheet of fibrous tissue which stretches across the heart and lies between the atria and ventricles (split the top chambers from the bottom).
it acts as an insulating barrier and stops/blocks the electrical signal travelling directly down to the ventricles.
what is the AV node/what part of the conduction system is it?
where is it located?
this node is located on the floor of the RA.
Atrio-ventricular node is the second part of the heart’s conduction system that is activated by the electrical signal as it spreads through the atria. once it reaches this node, it slightly delays for about one tenth of a second and is not passed on immediately.
when it does pass on, its passed to the AV-bundle.
AV Bundle
Bundle branches are where AV bundles split into two separate bundle branches which allows the electrical signal to travel down them towards the apex of the heart.
purkinje fibres
when the signal reaches the apex, the signal travels back up the way through purkinje fibres; which are branches that spread out deliver the electrical signal to cardiac muscle cells in the wall of each ventricle. - this then causes the two ventricles to contract and which pumps the blood out of the heart.
why is the electrical signal sent down to the apex before coming back upwards?
the purkinje fibres start at the apex (bottom) of the heart.
as a result, the areas of the ventricles (bottom) closest to the purkinje fibres will contract first, meaning the ventricles will contract/squeeze similar to how a toothpaste tube is squeezed from the bottom up, to get the most out; to get the most blood out of the heart and into the body.
if the electrical signal made the ventricle contract at the top and didn’t travel down and up, it would be like squeezing toothpaste from the top, a less efficient way of getting a lot out.
two stages of cardiac cycle;
systole
-term for contractions; the pressure in the blood vessels when the heart has contracted and pumped blood at a high pressure into the circulation
diastole
-a term for relaxation; blood pressure between contractions, when the heart is relaxing
how long does the cardiac cycle last?
around 800 milliseconds (0.8 of a second)
what is an ECG?
an electrocardiogram allows us to investigate heart activity and state in a non-invasive way.
it is a useful tool for assessing heart function. electrodes are attached to the skin’s surface which allows for the electrical activity to be recorded and monitored; producing spikes and blips on a machine.
ECG Waves;
blips and spikes demonstrating heart activity produce a sequence which corresponds to this. these waves have names (a lettering system);
P wave; Atrial Activation
- these waves correspond to activation of the atria.
- shows the electrical signal sweeping across the atria (which makes the heart contract)
QRS waves; Ventricular Activation
-this (one) wave shows the electrical signal passing through the ventricles, which makes the ventricles contract
T wave; Ventricular Relaxation
-shows the ventricles recovering and going back to normal (relaxing)
why is there no wave on an ECG that corresponds (shows) atrial relaxation?
because the atria begin to relax at exactly the same time the ventricles start to contract and so the QRS wave conceals the wave for Atrial Relaxation
what are blood vessels?
blood vessels allow the transportation of blood and all its essential components to be carried around the body to be used & disposed of.
what is found in ALL arterial walls?
tunica intima- lines the inside
tunica media- thick middle
tunica externa- outside layer
two structures & their functions within blood vessel walls?
tunica media contains both elastic fibres and smooth muscle cells;
elastic;
-within the tunica media often moreso in bigger arteries (to handle their higher pressure of blood, e.g. aorta)
muscular
- smaller arteries often have more smooth muscle tissue
- this allows them to contract/relax which changes diameter of muscular arteries to be altered
- vasoconstriction & vasodilation adjusts flow to different areas of the body
arteriole points;
- very narrow arteries (smallest)
- have a lot of smooth muscle tissue in their walls which assists them with their main function; blood pressure adjustments
capillary notes;
- only 1-cell thick
- allows gas exchange between O2 & co2 to happen efficiently- quickly & easily
*
veins notes;
- carry deoxygenated blood from the body back to the heart
- this blood is at a low pressure than in the arteries and this moves slower, veins have valves to prevent a back-flow of blood (less force = less speed)
- veins close and open, allowing the blood moving at some pace upwards, squeezing it through like opening/closing doors
- by the time the blood has made its way from the heart down to the feet, the pressure within the veins in the legs is very low (less pressure to push the blood along).
- walking/movement of the legs can assist with venous return (pushing blood upwards/onwards, back to the heart) due to our leg muscles having to contract for us to do this.
double circulation of CVS
CVS is a double-circulatory system as blood passes through the heart twice per individual circuit.
Pulmonary circulation
-between the heart and lungs
Systemic circulation
-between the heart and rest of the body
pulmonary circulation points;
- moves blood between the heart and lungs
- from from the right ventricle through the pulmonary ARTERIES to the lungs
- right pulmonary artery goes to the R lung
- left pulmonary artery goes to the L lung
- gas exchange takes place via the respiratory membrane (via capillary bloodstream and alveoli membrane/wall)
- this newly oxygenated blood is then returned to the heart via the left and right pulmonary veins; both of which entering the left atrium.
systemic circulation points;
- moves blood between the heart & rest of body
- freshly oxygenated blood leaves the heart via the LA into the aorta into the rest of the body
- aorta is a large elastic artery which can manage the high pressure blood ejected from the heart
- the aorta branches into smaller and smaller arteries
- the blood (now deoxygenated) now returns back to the heart; RA, through a big vein called the vena cava, two of which;
- inferior; veneous return from lower part of body
- superior; veneous return from top parts of body
the heart’s personal blood supply is called?
coronary arteries; the heart is an organ that requires its own blood supply to live and function effectively.
these arteries are off-shoots of the aorta, meaning their blood is rich in oxygen
how many times can the heart beat in one life time?
3 million times
two systems involved in extrinsic factors;
NS & Endocrine System
NS involvement with extrinsic factors;
the part of the NS involved in extrinsic factors is the autonomic NS, which subdivides into the sympathetic & parasympathetic systems;
both of these systems have an affect on the heart’s rate, as they both send axons to the heart’s SA Node (heart’s pace maker).
parasympathetic NS
-its nerve cells release the neurotransmitter ACh which slows down the heart rate
sympathetic NS
-its nerve cells release the neurotransmitter noradrenaline which increases our heart rate
the NS can also have an impact on the strength of each heart contraction; force it generates and how powerfully it contracts. - only the sympathetic NS can have any significant affect, as it sends axons to the myocardium (muscle cells of heart) which causes a greater contraction and therefore a greater BP.
endocrine system extrinsic factor
some of the sympathetic nerve cells can send messages to the adrenal glands which causes them to release adrenal (Adr) and noradrenaline (Na) into the bloodstream, which eventually reaches the heart.
these hormones have the same affect as the sympathetic NS’s nerve cells, as they can increase heart rate and force of each contraction- therefore also BP.
(fight or flight)
what is cardiac output (CO) ?
the amount of blood pumped out of the heart in a single minute. two things can affect CO;
1- heart RATE. each heart beat represents blood being ejected from the heart to the body. the faster the heart beat, the more blood pumped out (increased CO)
2-stroke VOLUME. the amount of blood pumped out by a single heart beat. the greater the strength and force of the heart, the greater volume of blood pumped out
therefore, CO is equal to heart rate X stroke volume.
example of CO calculation;
If jed, whilst at rest, has the following;
HR; 70bpm
SV; 80mL
CO=70 X 80 = 5600mL
CO is expressed in Litres, so we have to convert mL to L; divide by 1000…
5600 divided by 1000 equals 5.6L
Jed’s CO = 5.6L / amount of blood is heart beats per minute
normal cardiac output (resting adult)
5-6 Litres of blood per minute
why is there a pause of the electrical signal during the cardiac cycle at the AV node?
to allow the ventricles to efficiently fill with blood before its too soon
what is the cardiac notch?
the inner dip of the left lung which gives room to the heart in the chest
