Chapter 5 Heart and monitoring heart function Flashcards
Outline the benefit of a mass transport system
- moves substances around the body quickly
- shortens diffusion distance
Explain why a pumping mechanism required for a mass transport system
due to a higher demand for nutrients and production of waste (due to higher metabolic rate)
State the function of the atrioventricular valves
to prevent backflow of blood into atria from the ventricle during ventricular systole
State the function of the semilunar valves
to prevent blackflow of blood into the ventricles from the arteries during ventricular diastole
Describe the events that occur during atrial systole
- atria contract –> increased pressure
- ventricles in diastole
- AV valves open/semi-lunar valves close
- blood flows from A–>V (70% passive)
Describe the events occur during ventricular systole?
atrial diastole –> decreased pressure
ventricles in systole
AV valves close/semi-lunar valves open
blood flows from V–>arteries
Describe the events occur during total diastole
atrial diastole –> increased pressure
ventricles in diastole
AV valves open/semi-lunar valves close
blood flows passively from vena cave–>A
Explain how is the cardiac cycle controlled
the sinoatrial node (SAN) sends a wave of excitation to both atria –> atrial systole
band of fibrous collagen tissue prevents conduction of wave of excitation
atrioventricular node (AVN) delays w.o.e. and then sends out second w.o.e. from top of ventricular septum down the Bundle of His to the apex and then up the walls
causes upward contractions
Explain why monitoring heart function is so important
to look for heart/vascular diseases
to look for risk factors that contribute to CHD
Define the term stroke volume
the volume of blood pumped out of the left ventricle during the cardiac cycle
60-80cm^3
Define the term cardiac output
the volume of blood pumped out of the left ventricle each minute
State how is cardiac output calculated
stroke volume x heart rate
Describe the term ‘pulse’
the expansion of the artery wall during ventricular systole
during diastole, the elastic recoils
The pulse can be taken at radial, temporal and carotid artery or in the groin (femoral artery)
Explain how age affects the HR
decreases with age
children have faster h.r. due to growth
Exlpain how diet can affect the HR
cholesterol can block coronary arteries
saturated fats increase risk of strokes and heart disease
fruit/veg/starchy foods decrease h.r.
Explain how exercise can affect the HR
during activity + in recovery = exercise increases HR
post activity = exercise increases the strength of cardiac muscle resulting in a decreased HR
Describe how cardiac monitors can be used to analyse heart activity
electrodes placed on skin on opposites sides of the heart
result = electocardiogram
corresponds to electrical activity and pressure
State the key stages of an electrocardiogram
P = atrial excitation from SAN –> atrial systole
QRS = ventricular systole
T = repolarisation of cardiac muscle during diastole
Describe how an electrocardiogram can indicate heart abnormalities
raised ST = heart attack
small P = atrial fibrillation
deep S = ventricular hypertrophy (incr. muscle thickness)
short gaps = tachycardia
long gaps = brachycardia
Define a myocardial infarction?
when the blood supply to cardiac muscle is totally/partially cut off, preventing aerobic respiration in muscle cells
State the symptoms of a myocardial infarction
faint pulse
chest pain
nausea
ashen skin
irregular or rapid pulse
Define a cardiac arrest
When the heart no longer functions usefully as a pump
Describe what is ventricular fibrillation
rapid uncontrolled contraction of the muscles in the ventricles –> no effective movement of the blood
Describe an atheroma
a build of of WBCs that have taken up LDLs and become deposited in the lining of the artery WALLS
deposits cholesterol, dead fibres and muscle cells
restricts blood flow –> myocardial infarction
Explain how high levels of saturated fats lead to coronary heart disease
raises LDL and LDL:HDL ratio
LDLs deposit cholesterol in wall of coronary artery
causing an atheromatous plaque
reduces lumen size which reduces oxygen supply to cardiac muscle
–> coronary thrombosis
–> myocardial infarction
Label the diagram
Label the diagram
Describe the characteristics of cardiac muscle (6 marks)
o Specialised muscle as doesn’t rhythm require nerve stimulation to contract i.e. myogenic
o Muscle contracts in regular rhythm
o Does not fatigue or require rest (unlike skeleatl muscle)
o Specialised striated muscle (fainter striations compared to skeletal muscle)
o Fibres are branched and uninucleated
o Cardiac muscle cells interconnect resulting in simultaneously contraction
o Contraction speed = intermediate [compared to skeletal (rapid) and smooth (slow)]
o Length of contraction = intermediate [compared to skeletal (short) and smooth (long)]
o Cardiomyocytes (cardiac muscle cells) supplied with oxygen & glucose by coronary artery if it becomes blocked -> heart attack
Describe th function of the aorta
Carries oxygenated blood from LV to the body
At high pressure (as it has to force the blood over a large distance hence overall there is a higher resitance within the blood vessels)
Largest artery
Describe the function of the atria
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)
LA: forces oxygenated blood into LV (short distance so low pressure)
RA forces deoxygenated blood into RV (short distance so low pressure)
Both atria always contract simultaneously
Describe the function of the ventricles
Contract to generate a force to move blood at high pressure out of the heart
LV: forces oxygenated blood into aorta at high pressure
Pressure is high as LV wall is the thickest (of all 4 chambers) i.e. most cardiac muscle
RV: forces deoxygenated blood into pulmonary artery at lower pressure than LV (if it was the same the pressure would be too high when it reaches the avleoli and would rupture the alveoli)
Both ventricles always contract simultaneously
State the type of valve and the function of the aortic valve
= semi-lunar valve
- found between the LV and the aorta
- prevents backflow of blood from aorta to LV during ventricular diastole
State the type of valve and the function of the pulmonary valve
= semi-lunar valve
* found between the RV and the pulmonary artery
* prevents backflow of blood from pulmonary to RV during ventricular diastole
Name the 2 atrioventricular valves
Bucuspid
Tricuspid
REMEMBER: LAB RAT (LA = bicuspid, RA = tricupsid)
Descirbe the role of the tricuspid valve
- Located between RA and RV
- Prevents backflow of blood from RV to RA during ventricular systole
- Close when pressure of RV > pressure of RA
- Ensures deoxygenated blood flows into pulmonary artery
Describe the role of the bicuspid valve
- Located between LA and LV
- Prevents backflow of blood from LV to LA during ventricular systole
- Close when pressure of LV > pressure of LA
- Ensures oxygenated blood flows into aorta
Describe the role of the septum
Separates RHS from LHS of heart
Keeps oxygenated blood separated from deoxygeanted blood
Describe the role of the vena cava
Carries deoxygenated blood from the body to the RA
Superior vena cava delivers deoxygenated blood from head
Inferior vena cava delivers deoxygenated blood from rest of body
Largest vein
Explain the importance of valves in the heart and associated blood vessels
Only open one way
Prevent the back flow of blood
Will open when the pressure behind of it is greater than the pressure in front of it
Will close when the pressure in front of it is greater than the pressure of blood behind it
Blood flows down pressure gradient (from high pressure to low pressure)
Decsribe the events that occur during atrial systole
- Ventricles relax (ventricular diastole)
- Atrial walls contract -> decreases volume of blood & increases pressure in atria
- Atria are emptied -> blood forced into ventricles
- Through atrioventricular valves (remember LAB RAT)
- Slight increase in ventricular volume & pressure as ventricles fill with blood
Describe the events that occur during ventricular systole
- Atria relax (pressure falls)
- Ventricle walls contract -> decreases volume of blood
- Pressure in ventricles rises for ~0.1s
- Pressure in ventricles -> pressure in atria atrioventricular valves are forced shut
- High pressure in V opens semi-lunar valves (aortic or pulmonary)
- Blood is forced into aorta (from LV) or pulmonary artery (from RV)
- Pressure & volume of blood in V decreases
Describe the events during diastole
- Both atria and ventricles relax (muscular walls of both A and V relax)
- Higher pressure in pulmonary artery & aorta closes semi-lunar valves (preventing backflow of blood into V)
- Atria fill with blood (increasing their pressure) due to higher pressure in the vena cava and pulmonary vein
- Ventricles continue to relax ventricular pressure <pressure in atria
- Atrioventricular valves open and blood flows into V passively (i.e. no contraction of A required)
- Process continues
Explain what causs the ‘lub-dub’ sounds of the heart beat
Lub = atrioventricular valves closing as V contract
Dub = semi-lunar valves closing from backflow of blood (from aorta and pulmonary artery) as V relax
Define the term myogenic
no nerve stimulation required to make the cardiac muscles contract
remember: only cardiac muscle is myogenic
Describe how the cardiac cycle is controlled
Thois would be a 6 marker, level of response, question so make sure you give details in the correct order and provide sufficient detail
- Wave of electrical excitation starts in sino-atrial node (specialised patch of muscle found in the wall of the right atrium); SAN = pacemaker
- Impulse passes from SAN to atrial muscle
- Causes atria to contract together i.e. initiates heartbeat
- Layer of non-conducting collagen (fibrous) tissue between atria and ventricles prevents wave of excitation passing directly to ventricles
- Electrical activity of SAN is picked up by atrio-ventricular node (AVN) in the septum between the atria
- AVN delays electrical activity by 0.1s
- Electrical activity is sent from AVN to Bundle of His (specialised conducting muscle fibres made up of Purkyne fibres)
- Electrical activity spreads from the Bundle of His down 2 branches of the Purkyne fibres in the septum
- Electrical activity arrives at apex of the heart
- At apex Purkyne fibres spread out through both ventricle walls
- Wave of excitation triggers simultaneous contraction of ventricles starting at the apex (to allow more efficient emptying of ventricles) i.e. ventricular systole occurs from the bottom of the heart upwards
Explain why it is importatnt that the V contract after the A
If both ventricles contracted at the same time:
o The V would generate a higher pressure than the A
o This would force the A-V valves to shut
o Blood in the A would consequently NOT enter the V
o Blood would be forced back into the veins
o This would place strain on the heart
o And decrease the volume of blood moved through the heart
o Hence less blood would be oxygenated
o Poorer transport system and gas exchange
State the 2 nerves that regulate the HR
1) accelerator nerve (sympathetic nervous system)
2) vagus nerve (parasympathetic nervous system)
Describe the role of the vagus nerve in regulating the HR
(vagus nerve)
* is part of the parasympathetic nervous system
* this nerve uses acetylcholine as the neurotransmitter
* it decreases the HR
Describe the role of the accelerator nerve in regulating the HR
accelerator nerve
* is part of the sympathetic nervous system
* this nerve uses noradrenaline as neurotransmitter
* it increases the HR
Name the neurotransmitter involved in the regulation of the HR
Adrenaline
State the formula used to calculate the cardiac output.
State the most apprropriate units for CO
CO = SV x HR
units = cm3 min-1
remember the ‘3’ and ‘-1’ are superscript - It won;t let me do that here :(
Suggest why the HR is more accurately determined by counting the PR in 30s and then doubling the value rather than couting the PR for 60s
Less likely to get a counting error in shorter time period
Less likely to be affected by fluctations due to envoironmental disturbances
Hence value is more accurate
Outline how to accurately measure a patient’s HR
- If the resting heart rate is to be determined, you must have been resting for at least 10 minutes. The exercise heart rate is obtained while you are exercising
- The patient must be in the sitting position
- To measure the pulse at the wrist, place the index and middle finger over the underside of the opposite wrist, below the base of the thumb
- Press firmly with flat fingers until you feel the pulse. To measure the pulse on the temple, place the index and middle finger just to the side of the head, in the soft, hollow area of the temple (where the temporal artery is positioned). Press firmly until the pulse is located
- Once you find the pulse, count the beats for 10 seconds, or for 30 seconds and multiply by 6 or 2 accordingly (to calculate beats per minute)
- Repeat 3 times and take a MEAN (increases reliability)
REMEMBER: use the term mean (not average)
Explain why the HR increases during (strenuous exercise)
- Skeletal muscles contract at higher rate
- Hence higher demand for oxygen & glucose
- Hence volume of blood being circulated needs to **increase **dramatically
- Hence HR and SV both increase (HR from 72 to 140bpm & SV from 70 to 150cm3 per beat)
- Heart muscle also 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)
Remember: your answer must be comparative. This means you must say highER, greatER, MORE throughout your answer
State 3 natural factors which affect a person’s HR
- Age = children have higher HR than adults (HR decreases with age)
- Genetics = tendency for lower/higher HR inherited
- Diseases = some affect HR e.g. CF increases HR (and pulmonary blood pressure)
State 3 lifesytle (also called environmental) factors which affect a person’s HR
- Physical activity level = increased PAL -> inc HR for duration of exercise & straight after (but over time leads to decreased HR). Training decreases resting HR (due to increased SV and so same CO is achieved at lower HR)
- Smoking = nicotine -> inc HR (as stimulates release of neurotransmitter noradrenaline -> increases electrical activity of SAN)
- Diet = diet rich in fruit & veg & CBH -> dec HR; diets rich in saturated lipids -> inc HR
Explain the purpose of an ECG
- ECGs measure spread of electrical excitation through heart
- Process = electrocardiography
- ECGs don’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
- Results can be monitored on computer screen or printed out
- Changes in peaks can be used to detect and diagnose heart conditions
Assess the level of risk of giving a patient an ECG
Level of risk = very low/none
- Because this procedure merely monitors the electrical impulses and does not emit electricity
- Hence no risk of shock
- During an exercise electrocardiogram, some patients experience arrhythmias or heart distress
Label AND annotate this typical ECG
Make sure you have both a label AND an annotation for each area of the ECG
Explain the significance of the P wave on an ECG
wave of excitation passing over atria walls (i.e. depolarisation of atria resulting in atria contraction)
Explain the significance of the T wave on an ECG
repolarisation (recovery) of ventricles (recovery of the atria is masked by QRS)
Explain the significance of the QRS segment in an ECG
wave of excitation passing over ventricles walls (i.e. depolarisation of ventricles)
Which part of the ECG trace indicates the ventricules are filling. Justify your answer.
T to Q
reason: ventricles are relaxed
Explain the significance of the difference in height of any waves on an ECG
The height of any wave indicates how much electrical charge is passing through the heart: bigger wave = more electrical charge = stronger contraction
Which part of the ECG trace indicates the ventricles are contracting?
Q to T
Identify the medical condition shown in this ECG trace.
Justify your answer.
Ventricular fibrillation
reason: there is no regular pattern to ECG
Identify the medical condition shown in this ECG trace.
Justify your answer.
Atrial fibrillation
Reasons:
There is no distinct P waves
*The P-R interval is not easily identifiable
Describe the effects of VF
- Victim has no blood circulation
- Usually unconscious
- Almost certainly fatal: causes cardiac arrest
- The person having VF suddenly collapses or falls unconscious, because the brain and muscles have stopped receiving blood from the heart
Describe the treatment for a patient with VF
- Immediate use of defibrillator
- May need coronary bypass surgery
- Most common complication of VF is sudden death
- For survivors of VF, complications include coma, reduced mental acuity, and neurological problems similar to those seen after a stroke
Suggest what physiological events may cause a person to go into VF
- Muscle in ventricle walls flutter
- Possibly due to myocardial infarction
Suggest what physiological events may lead to a person going into AF
- Most common cause = abnormalities or damage to the heart’s structure
- High blood pressure
- Heart attacks
- Coronary artery disease
- Abnormal heart valves
- Congenital heart defects you’re born with
- Hyperthyroidism
Describe the most appropriate treatment for a person with AF
- Medication to prevent a stroke
- Medication to control the heart rate or rhythm
- Cardioversion – where the heart is given a controlled electric shock to restore normal rhythm
NB: AF is not usually life-threatening
Describe the effects of AF
- Increased risk of stroke
- Increased risk of heart failure
- Chronic fatigue
- Additional heart rhythm problems
- Inconsistent blood supply
Identify the medical condition shown in this ECG trace.
Justify your answer.
Bradycardia
- Resting HR is very slow
- Longer gaps between QRS complexes
- P waves and height of QRS peaks are both similar to a normal trace
- Defined as resting HR between 40-60 bpm
- ECG looks normal except delay between waves of more than one second
- Long gap between T wave and next P wave
Describe the effects of bradycardia
- Usually no effect
- If severe may cause tiredness
- Due to insufficient blood flow to organs
Suggest what physiological events can lead to bradycardia
- Could be the sign of an active/healthy person
- Could be an inactive SAN
State how bradycardia can be treated
- Artificial pacemaker to replace SAN
Identify the medical condition shown in this ECG trace.
Justify your answer.
Tachycardia
- Resting HR is very high
- Shorter gaps between QRS complexes
- Defined as resting HR above 100bpm
- ECG shows very small gap between T wave and P wave of next cardiac cycle
Suggest what physiological events can lead to tachycardia
- A reaction to certain medications
- Congenital (present at birth) electrical pathway abnormalities in the heart
- Congenital abnormalities of the heart
- Consuming excess alcohol
- coronary artery disease (atherosclerosis), heart valve disease, heart failure, heart muscle disease (cardiomyopathy), tumours, or infections
- Hypertension
- Hyperthyroidism (overactive thyroid gland)
- Smoking
- Certain lung diseases
Describe the effects of tachycardia
- Rapid HR = less time for the atria and ventricles to fill
- Hence less blood is pumped to the body with each heartbeat
- Overtime drop in blood pressure
- Also increases the workload of the heart increasing myocardial (heart muscle) O2 demand
Describe the treatment for tachycardia
- Varies depending on what caused the condition, the patient’s age and general health, and other factors
- Aim = address the cause of the tachycardia
- May try to slow the rate i.e. prevent subsequent episodes of tachycardia to reduce risk complications
Identify the medical condition shown in this ECG trace.
Justify your answer.
- Myocardial infarction
- Peaks and troughs of ECG are less distinct and not as regular
- S-T portion is higher than normal (ST elevation)
Describe the effects of a myocardial infarction
- Leads to the formation of a blood clot (coronary thrombosis)
- Blood supply to part of heart muscle is partly or full blocked
- Cardiac muscle cells deprived of oxygen
- Cardiac cells stop contracting
Describe the 3 main types of treatment for a myocardial infarction
- Aspirin
- Thrombolytics
- Anticoagulants
Explain how aspirin is used therapeutically to treat an MI
- Aspirin: stops blood from clotting
- Nitro-glycerine: dilates blood vessels
- Pain relieve: relieve pain and is often given intravenously
Explain how thrombolytic drugs are used therapeutically to treat an MI
- Thrombolytics: break up clots. Most effective when taken within 2 hours of the heart attack and are not given after 12 hours have elapsed. These drugs may be given with other anticoagulants (blood thinners)
Explain how anticoagulants are used therapeutically to treat an MI
- Anticoagulants: make blood less likely to form clots e.g. heparin
State the most common cause of an MI
An occlusion of coronary artery following the rupture of an atherosclerotic plaque
Describe how to use a defibrillator
Apply two electrode 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 (“electrical shock”)
This stops the chaotic electrical activity of fibrillation & allows heart to restore regular rhythm determined by SAN
What is an AED?
Use an automated external defibrillator (AED)
AED = safe, portable electrical device
AED helps to establish a regular heartbeat during a cardiac arrest by monitoring the person’s heartbeat and giving them an electric shock if necessary
Describe the events that occur during a cardiac arrest
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 & irregularly
Ventricles do not fill fully (as no ventricular diastole to allow filling)
Blood isn’t pumped out of ventricles
Patient stops breathing due to lack of oxygen supply
Describe how to carry out CPR
- Check airway and for breathing by tilting head back
- Carry out chest compressions (on adult)
- Place the 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 your fingers
- Using your body weight, keep your elbows locked straight & press straight down vertically (using your body weight)
- Press down firmly & quickly by 4-5cm then relax
- After each compression release all pressure on the person’s chest without losing contact between the hands and sternum
- Aim to do the chest compressions at a rate of 100-120 compressions a minute
- Repeat x30 then give mouth-to-mouth resuscitation (expired air resuscitation) twice
- Repeat this on 30:2 ratio until an ambulance arrives
Describe 3 signs that a person may be having a cardiac arrest
o they appear not to be breathing
o they’re not moving
o they don’t respond to any stimulation; such as being touched or spoken to
State 5 common signs of a heart attack
chest pain – a sensation of heavy crushing pressure, tightness or squeezing in the centre of the chest
pain in other parts of the body – it can feel as if the pain is travelling from the chest to the arms (usually the left arm is affected, but it can affect both arms), jaw, neck, back and abdomen
feeling lightheaded or dizzy
profuse sweating
shortness of breath
cold ashen-looking skin and blue lips
rapid, weak pulse which may be irregular
feeling sick (nausea) or being sick (vomiting)
an overwhelming sense of anxiety (similar to having a panic attack)
coughing or wheezing
unexpected collapse
