The cardiovascular system

Question 1

average heart rate of an adult

Answer 1

70 beats per minute

Question 2

structure of the heart; apex & base

Answer 2

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

Question 3

location of the heart?

Answer 3

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).

Question 4

what is pericardectomy?

Answer 4

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.

Question 5

chambers of the heart

Answer 5

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

Question 6

heart valves

Answer 6

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

Question 7

valve flaps notes;

Answer 7

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

Question 8

what does the heart wall do and what is it made of?

Answer 8

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

Question 9

cardiac muscle tissue points;

Answer 9

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.

Question 10

cardiac muscle cell points;

Answer 10

• 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.

Question 11

two names for cardiac muscle cells?

Answer 11

myocardial cells

myocytes

Question 12

how heart valves work;

Answer 12

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.

Question 13

what are intrinsic & extrinsic factors?

Answer 13

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.

Question 14

what is the heart’s conduction system?

Answer 14

the network of nodes, cells and signals that control the heart’s heartbeat

Question 15

what is the SA node?
where is is located?
how active is it in one minute?
what does it do?

Answer 15

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.

Question 16

cardiac skeleton

Answer 16

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.

Question 17

what is the AV node/what part of the conduction system is it?
where is it located?

Answer 17

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.

Question 18

AV Bundle

Answer 18

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.

Question 19

purkinje fibres

Answer 19

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.

Question 20

why is the electrical signal sent down to the apex before coming back upwards?

Answer 20

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.

Question 21

two stages of cardiac cycle;

Answer 21

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

Question 22

how long does the cardiac cycle last?

Answer 22

around 800 milliseconds (0.8 of a second)

Question 23

what is an ECG?

Answer 23

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.

Question 24

ECG Waves;

Answer 24

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)

Question 25

why is there no wave on an ECG that corresponds (shows) atrial relaxation?

Answer 25

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

Question 26

what are blood vessels?

Answer 26

blood vessels allow the transportation of blood and all its essential components to be carried around the body to be used & disposed of.

Question 27

what is found in ALL arterial walls?

Answer 27

tunica intima- lines the inside
tunica media- thick middle
tunica externa- outside layer

Question 28

two structures & their functions within blood vessel walls?

Answer 28

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

Question 29

arteriole points;

Answer 29

• very narrow arteries (smallest)
• have a lot of smooth muscle tissue in their walls which assists them with their main function; blood pressure adjustments

Question 30

capillary notes;

Answer 30

• only 1-cell thick
• allows gas exchange between O2 & co2 to happen efficiently- quickly & easily

*

Question 31

veins notes;

Answer 31

• 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.

Question 32

double circulation of CVS

Answer 32

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

Question 33

pulmonary circulation points;

Answer 33

• 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.

Question 34

systemic circulation points;

Answer 34

• 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

Question 35

the heart’s personal blood supply is called?

Answer 35

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

Question 36

how many times can the heart beat in one life time?

Answer 36

3 million times

Question 37

two systems involved in extrinsic factors;

Answer 37

NS & Endocrine System

Question 38

NS involvement with extrinsic factors;

Answer 38

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.

Question 39

endocrine system extrinsic factor

Answer 39

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)

Question 40

what is cardiac output (CO) ?

Answer 40

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.

Question 41

example of CO calculation;

Answer 41

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

Question 42

normal cardiac output (resting adult)

Answer 42

5-6 Litres of blood per minute

Question 43

why is there a pause of the electrical signal during the cardiac cycle at the AV node?

Answer 43

to allow the ventricles to efficiently fill with blood before its too soon

Question 44

what is the cardiac notch?

Answer 44

the inner dip of the left lung which gives room to the heart in the chest