Chapter 5 The Heart and Monitoring Heart Function

Question 1

Why do multicellular organisms need a mass transport system?

Answer 1

Multicellular organisms need a mass transport system because:
-there is a higher demand for nutrients and greater production of waste
-higher metabolic rate
-more active organisms which means that there is a larger number of cells respiring very quickly so a greater demand for oxygen, glucose and carbon dioxide
-the SA:V is too low for diffusion to deliver nutrients at an appropriate rate nor remove wastes at a suitable rate
-hence a transport system is needed to ensure the demand of all individual cells is met

Question 2

The Cardiac cycle: Atrial systole (and ventricle diastole)

Answer 2

During atrial systole muscles in the atrial walls contract, whereas muscles in the ventricle walls relax. This causes an increase in atrial pressure and a decrease in atrial volume, forcing the atrioventricular valves open. Blood is forced into the ventricles.

Question 3

Ventricular systole

Answer 3

During ventricular systole muscles in the ventricle walls contract only once waves of excitation pass through the Purkyne fibres, whereas muscles in the atrial walls relax. This causes an increase in ventricular pressure and a decrease in ventricular volume, forcing the atrioventricular valves closed and the semi lunar valves open. Blood is forced into the arteries.

Question 4

Complete cardiac diastole (ventricular and atria diastole)

Answer 4

-Both atria and ventricles relax
-higher pressure in pulmonary artery and aorta so semi lunar valves close to prevent backflow of blood into ventricles
atria fill with blood (increasing their pressure) due to higher pressure in the vena cava and pulmonary vein
ventricles continue to relax so pressure in atria is greater than pressure in ventricles
AV valves open and blood flows passively into ventricles
process continues

Question 5

When will valves open?

Answer 5

Valves open when the pressure behind them is greater than the pressure in front of them.

Question 6

Explain how valves close

Answer 6

Valves close when pressure in front of the valve is greater than the pressure behind.

Question 7

Control of the cardiac cycle

Answer 7

Electrical impulse is generated at sinoatrial node (SAN)
Electrical impulses sent across atrial walls.
Muscles in atrial walls contract
Layers of non-conducting collagen tissue between atria and ventricles prevents wave of excitation passing directly to ventricles.
AVN receives impulse which causes a slight delay to ensure the atria have stopped contracting before the ventricles contract.
Electrical impulse is sent down bundle of His.
Impulse sent to perkinje fibres.
Electrical impulse arrives at apex of the heart.
At apex, Purkyne fibres spread out through both ventricle walls. Waves of excitation triggers simultaneous contraction of ventricles starting at the apex ( to allow more efficient emptying of ventricles) ventricular systole occurs from the bottom of the heart upwards

Question 8

Explanation for when the calculated value is greater than the critical value

Answer 8

Calculated value is greater than the critical value
degrees freedom
there is a less than 5% probability that the difference between mean pulse rate…and… is due to chance.
rejecting the null hypothesis.
there is a statistically significant difference between…

Question 9

Explanation of calculated value

Answer 9

Calculated value is less than the critical value
degrees freedom
there is a more than 5% probability that the difference between…and…
accept the null hypothesis
there is not a statistically significant difference between…and…

Question 10

Cardiac Muscle of the heart

Answer 10

-myogenic
-muscle contracts in regular rhythm
does not fatigue
-specialised striated muscle
-fibres are branched and uninucleated
-cardiac muscle cells interconnect resulting in simultaneously contraction
intermediate contraction speed and intermediate length of contraction
cardiomyocytes supplied with oxygen and glucose by coronary artery if it becomes blocked—-> heart attack

Question 11

Function of aorta

Answer 11

-carries oxygenated blood at (high pressure as it has to force the blood over a large distance hence overall there is higher resistance within the blood vessels) from left ventricle to the body

Question 12

function of pulmonary artery

Answer 12

-carries deoxygenated blood from right ventricle to the lungs

Question 13

function of pulmonary vein

Answer 13

-carries oxygenated blood from lungs to right atrium

Question 14

Function of atria

Answer 14

-contract to generate a force to move blood at low pressure into the ventricles
pressure is low as walls of atria are thin (less cardiac muscle)
Both atria always contract simultaneously

Question 15

Function of carotid arteries

Answer 15

-blood vessels that carry oxygen-rich blood to the head, brain and face

Question 16

Function of ventricles

Answer 16

-contract to generate a force to move blood at high pressure out of the heart
Pressure is high as LV is thickest (most cardiac muscle)
LV: Forces oxygenated blood into aorta at high pressure
RV: forces deoxygenated blood into the pulmonary artery at lower pressure than LV as if it was the same, the pressure would be too high and would rupture the alveoli.
Both ventricles contract simultaneously

Question 17

Function of semilunar valves

Answer 17

AORTIC valve: found between LV and aorta so prevents backflow of blood from aorta to LV during ventricular diastole
PULMONARY valve: found between the RV and the pulmonary artery so prevents backflow of blood from pulmonary to RV during ventricular diastole.

Question 17

Function of Atrio-ventricular valves

Answer 17

Right atrioventricular valve:
prevents backflow of blood from RV to RA during ventricular systole.
closes when pressure in RV is greater than the pressure in RA
ensures deoxygenated blood flows into pulmonary artery.
Left atrioventricular valves: prevents backflow of blood from LV to LA during ventricular systole.
closes when the pressure of LV is greater than pressure of LA
ensures oxygenated blood flows into the aorta

Question 17

Function of septum

Answer 17

-separates RHS from LHS so keeps oxygenated blood separated from deoxygenated blood

Question 18

Function of vena cava

Answer 18

-carries deoxygenated blood from the body to RA
superior vena cava delivers deoxygenated blood from head
Inferior vena cava delivers oxygenated blood from rest of body

Question 18

Function of chordae tendinae

Answer 18

-holds valves in place
-attaches valves to muscle wall of the ventricles
-prevents valves inverting when under pressure (during ventricular systole)

Question 19

Function of Bundle of His and Purkyne fibres

Answer 19

Bundle of His is located in septum and Purkyne fibres located in walls of ventricles
AVN stimulates Bundle of His
Bundle of His conducts wave of excitation to apex of heart

Question 19

Stroke volume

Answer 19

volume of blood pumped out of LV during each cardiac cycle

Question 19

Cardiac Output

Answer 19

volume of blood pumped out of the LV each minute

Question 19

Heart rate

Answer 19

number of beats per minute

Question 19

Equation for CO

Answer 19

CO=SVXHR (cm cubed min -1)

Question 19

Measuring pulse rate

Answer 19

Count number of beats in an artery in 30s and then double (less prone to counting errors so more accurate)

Question 19

What is pulse?

Answer 19

distension of artery wall as blood surges through artery with ventricular systole, followed by elastic recoil of artery wall during ventricular diastole

Question 20

Different places to measure pulse

Answer 20

radial artery-wrist
femoral artery-groin
carotid artery-neck
temporal artery-temples
Need to use place where artery is close to the surface of skin and passes over bone

Question 21

Advantages of measuring pulse rate by counting

Answer 21

-quick
-easy
-little equipment and skill needed

Question 22

Why does heart rate increase during strenuous exercise?

Answer 22

-skeletal muscles contract at a higher rate
-higher demand for oxygen and glucose
-volume of blood being circulated needs to increase dramatically
HR and Sv both increase
heart muscle contracts more strongly—>greater contraction—>greater force of ejection
skeletal muscles also contract more frequently—-> veins compressed more by skeletal muscles—-> greater venous return (to remove lactic acid, carbon dioxide, heat from contracting muscles)

Question 23

Factors that affect heart rate

Answer 23

Age= HR decreases with age
Genetics= tendency for lower HR/higher HR inherited
diseases= some affect HR CF increases HR

Question 24

Lifestyle factors that affect heart rate

Answer 24

-PAL——> as increased physical activity level, increased HR Training decreases resting HR due to increased SV and so some cardiac output achieved at lower HR
Smoking=nicotine=increases HR as stimulates release of neurotransmitter noradrenaline which increases electrical activity of SAN
Diet=diet rich in fruit and veg decrease heart rate, diets rich in saturated lipids increase heart rate

Question 25

What would happen if both ventricles contract at the same time?

Answer 25

If both ventricles contracted at the same time:
-the V would generate a higher pressure than the A
-forcing the A-V valves to shut
-Blood in the A would consequently not enter the V
-Blood will be forced back into the veins
-placing strain on the heart
and decrease the volume of blood moved through the heart
-less blood would be oxygenated
-poorer transport system and gas exchange

Question 26

What is the SAN?

Answer 26

-a pacemaker
-patch of non-conducting tissue
-myogenic so does not require an input from the brain
-starts the wave of excitation which generates the electrical activity causing the atria to contract.

Question 27

What are the 2 nerves that regulate the heart rate?

Answer 27

-accelerator nerve (sympathetic nervous system)=this nerve uses noradrenaline as neurotransmitter which increases the HR.
-vagus nerve (parasympathetic neurotransmitter)= this nerve uses acetycholine as neurotransmitter which decreases HR.
The neurotransmitter adrenaline also regulates HR.

Question 28

Invstigating the effect of exercise and pulse rate

Answer 28

IV= Age, gender, BMI, diet, training programme- shoud be at least 10 subjects (individual people)
DV= heart rate (or recovery rate)
CV= agae, gender, diet, level or intensity of training, PAL, BMI (unless these are the independent variable obviously)

Question 29

Health and safety for experiment on investigating effect of exercise and pulse rate

Answer 29

-ensure no subject has serious health conditions like asthma

Question 30

Processing data

Answer 30

-calculate mean to reduce the effect of any anamalous results

-calculate standard deviation to asses reliability of data
-size of SD indicates the spread of the data about the mean and the smaller the standard deviation, the more reliable data
Standard error=SD/ square root of N
-calculate t-test: to determine if there is a significant difference between the mean values for each IV category
state null hypothesis: there is no significant difference between the mean HR for “IV category” and the mean HR for “IV Category 2”

Question 31

What do ECGs measure?

Answer 31

ECGs measure spread of electrical excitation through heart through electrocardiography
-doesn’t directly measure electrical activity of the heart but measures small electrical differences in skin which occur as a result of the electrical activity of the heart

Question 32

Why are there no risks to electrocardiograms?

Answer 32

-no risks as this procedure monitors the electrical impulses and does not emit electricity
-no risk of shock

Question 33

Function of P wave

Answer 33

-wave of excitation passing over atroa walls (depolarisation of atria resulting in atria contraction)

Question 34

Function of QRS wave

Answer 34

wave of excitation passing over ventricle walls (depolarisation of ventricles)

Question 35

Function of T wave

Answer 35

repolarisation of ventricles

Question 36

Q——-T

Answer 36

Contraction time

Question 37

T——Q

Answer 37

filling time (ventricles are relaxed)

Question 38

What does height of wave indicate?

Answer 38

-indicates how much electrical charge is passing through the heart: bigger the wave: more electrical charge:stronger connection

Question 39

How to recognise a heart attack?

Answer 39

-chest pain, heavy crushing pressure, tightness, squeezing in the centre of the chest, pain travelling from chest to arms, jaw, neck, back and abdomen
-lightheaded or dizziness
-profuse sweating
-shortness of breath
-cold ashen looking skin and blue lips
-rapid and weak pulse which may be irregular
nausa or vomitting
anxiety
coughing
unexpected collapse

Question 40

How to assist someone having a heart attack

Answer 40

-call 999-inform ambulance control that it is a suspected heart attack
make person rest while waiting for an ambulance
sit person in W position-sitting up at about 75 degrees to ground with knees bent
300mg aspirin
medication for angina
monitor constantly and record pulse and breathing rate

Question 41

Treatment of cardiac arrest

Answer 41

-if person becomes unconscious follwing suspected heart attack they may be in cardiac arrest
-usually occurs as a result of ventricular fibrilation
results in no effective blood circulation
appear not to be breathing
not moving
don’t respond to any stimulation such as being touched or spoken to

Question 42

How to perfom CPR (Cardiopulmonary resuscitation)

Answer 42

-check airway and for breathing by tilting head back
carry out chest compressions on adult
place heel of your hand on the sternum at the centre of the person’s chest
place your other hand on top of your other hand and interlock fingers
using your body weight, keep your elbows locked straight and press straight down vertically
press down firmly and quickly by 4-5 cm and then relax
after each compression release all pressure on the person’s chestwithout lsoing contact between the hands and sternum
aim to do chest compresions at a rate of 100-120 compressions a minute
repeat x30 then give mouth to mouth resuscitation twice
repeat this 30:2 ratio until an ambulance arrives

Question 43

What happens during a cardiac arrest?

Answer 43

-supply of blood to region of cardiac muscle is disrupted
-area of cardiac muscle does not receive sufficient oxygen
-cardiac muscle in atrial or ventricular walls contract rapidly and irregularly
-ventricles do not fill fully as no ventricular diastole to allow filling
-blood isnt pumped out of ventricles
patient stops breathing due to lack of oxygen supply

Question 44

Using a defibrillator

Answer 44

-use an automated external defibrillator
-AED=Safe, portable elctrical device
-AED helps to establish a regular heartbeat during cardiac arrest by monitoring the person’s heartbeat and giving them an eectrical shock if necessary
-apply two electrodes pads to chest
-pads placed in diagonal line across chest with heart position in the middle
-reading on machine shows if heart is fibrillating
-if it is then AED applies electrical discharge
-stops the chaotic electrical activity of fibrillation and allows heart to restore regular rhythm determined by SAN.