8.5 the heart

Question 1

how does deoxygenated blood travel through the heart

Answer 1

it comes from the body and and if it comes from the upper body it enters the right atrium through the superior vena cava and if it comes from the lower upper body it enters through the inferior vena cava. at first the pressure is low but as blood flows in the pressure builds up and the tricuspid valve opens and blood flows through into the right ventricle so it is in both the right atrium and right ventricle and then the right atrium contracts and forces all the blood into the right ventricle and then the tricuspid valves shut to prevent the backflow of blood, the right ventricle then contracts fully and forces the deoxy blood through the semi-lunar valves into the pulmonary artery which transports the deoxy blood to the capilary beds of the lungs

Question 2

how does oxygenated blood travel through the heart

Answer 2

it comes from the lungs and enters the heart through the pulmonary veins to the left atrium at first the pressure is low but as blood flows in the pressure builds up and the bicuspid valve opens and blood flows through into the left ventricle so it is in both the left atrium and left ventricle and then the left atrium contracts and forces all the blood into the left ventricle and then the bicuspid valves shut to prevent the backflow of blood, the left ventricle then contracts fully and forces the oxy blood through the semi-lunar valves into the aorta which transports the oxy blood to the capillary beds of the lungs body

Question 3

what do the coronary arterys do

Answer 3

it supplys the cardiac muscle with the oxygenated blood it needs to keep contacting and relaxing

Question 4

what prevents the heart from over filling with blood

Answer 4

the heart is surrounded by inelastic pericardial membranes to prevent the heart from over-distending with blood

Question 5

what is the heart made of and what does this mean

Answer 5

its made of cardiac muscle which means it doesnt get fatigued and need to rest

Question 6

which side of the heart does deoxygenated blood pass through

Answer 6

the right side

Question 7

which side of the heart does oxygenated blood pass through

Answer 7

the left side

Question 8

what do the tendinous cords do

Answer 8

make sure that the valves arent turned inside out by pressures exerted when the ventricles contracts

Question 9

which side of the hearts muscular wall is thicker

Answer 9

the left side

Question 10

why is the muscular wall on the left side of the heart thicker than the right

Answer 10

because the lungs are relatively close to the heart and are much smaller than the rest of the body so the right side of heart has to pump the blood a relatively short distance and only has to overcome the resistance of the pulmonary circulation, the left side has to produce sufficient force to overcome the resistance of the aorta and the arterial systems of the whole body and move the blood under pressure to the whole body

Question 11

what does the septum do

Answer 11

it separates the left and right sides of the heart so the oxygenated and deoxygenated blood never mixes

Question 12

whats the cardiac cycle

Answer 12

it describes the events in a single heart beat

Question 13

how long does the cardiac cycle last (a single heartbeat)

Answer 13

0.8 seconds approx

Question 14

what happens in diastole

Answer 14

the heart relaxes, the atria and then the ventricles fill with blood, the volume and pressure of the blood in the heart build as the heart fills, but the pressure in the arteries in kept at a minimum

Question 15

what happens is systole

Answer 15

the atria contract closely followed by the ventricles the pressure inside the heart increases dramatically and blood is forced outside the right side of the heart to the lungs and forced out of the left side of the heart to the main body circulation, the volume and pressure of blood in the heart are low at the end of systole and the blood pressure in the arteries is at a maximum

Question 16

whats the sounds of the heart beat made by

Answer 16

blood pressure closing the heart valves

Question 17

what causes the first sound of the heartbeat

Answer 17

it comes as blood is forced against the atrio-ventricular valves (tricuspid and bicuspid) as the ventricles contracts

Question 18

what causes the second sound of the heartbeat

Answer 18

it comes as the backflow of blood closed the semi-lunar valves in the aorta and pulmonary artery as the ventricles relax

Question 19

the heart is myogenic what does this mean

Answer 19

it can generate/maintain its heartbeat by itself

Question 20

what is the benefit of the heart being myogenic

Answer 20

it prevents the body wasting resources maintain the basic heartbeat

Question 21

what is the basic rhythm of the heart maintained by

Answer 21

a wave of electrical excitation rather like a nerve impulse

Question 22

whats tachycardia and if its severe how can it be treated

Answer 22

when the heart beat is very rapid over 100bpm eg during exercise or when frightened
if abnormal can be cause by electrical control in the heart treated by med/surgery

Question 23

whats bradycardia and if its severe how can it be treated

Answer 23

when the heart beat is very slow below 60bpm when people are fit
if severe may need an artificial pacemaker to keep the heartbeating steadily

Question 24

whats ectopic heatbeat

Answer 24

extra heart beats that are out of rhythm its an extra heart beat followed by a longer than normal pause most people has one a day but many more can be severe and can be linked to a serious condition

Question 25

whats artial fibrillation and what causes it

Answer 25

this is an example of arrythmia an abnormal rhythm of the heart
rapid electrical impulses are generated in the atria they contract very fast up to 400x a minute however they dont contract properly and only some impulses are passed onto the ventricle which contracts much less often as a result the heart doesnt pump blood very effectively

Question 26

what does an electrocardiogram (ECG) measure

Answer 26

the spread of electrical excitation throughout the heart as it contracts
its doesnt directly measure the electrical activity of the heart it measures tiny electrical differences on the skin which result from electrical activity of the heart

Question 27

where does the wave of electrical excitation begin

Answer 27

in the pacemaker area, the sino-arterial node (SAN)

Question 28

what does the sino-arterial node do

Answer 28

it causes the atria to contract and in so initiates a heatbeat, a layer of non-conducting tissues prevent the excitation passing directly to the ventricles

Question 29

what picks up the electrical activity from the

Answer 29

the atrio-ventricular node (AVN)

Question 30

what do the atrio-ventricular nodes do

Answer 30

they impose a slight delay before stimulating the bundle of His

Question 31

what are His and where do they penetrate

Answer 31

they are a bundle of conducting tissue made up of purkyne fibres, which penetrate through the septum between the ventricles

Question 32

what does the bundle of His do

Answer 32

they split into two branches and conduct the wave of excitation to the apex (bottom) of the heart

Question 33

why does the AVN need to delay the wave of excitation

Answer 33

to make sure the atria have finished contracting before the ventricles begin to contract

Question 34

how is the contraction of the ventricles triggered using purkyne fibres

Answer 34

at the apex of the heart the purkyne fibres spread out through the walls of the ventricles the spread of excitation triggers the contraction of the ventricles, contraction starts at the apex to allow more efficient emptying of the ventricles