Term
| Where is the heart located? |
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Definition
Posterior to the sternum
Base of heart at the level of the 3rd costal cartilage
Slightly to the left (1.2 cms)
Apex at the 5th intercostal space
7.5 cms to the left
Rotated to the left
Anterior surface of heart is the right atrium and ventricle
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Term
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Definition
| lines the inner surface of the pericardial sac |
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Term
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Definition
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Term
| Three layers of the heart wall |
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Definition
Epicardium: Outer surface of the heart
Visceral peicardium
Myocardium: Muscle wall of the heart
Concentric layers of cardiac muscle
Endocardum: inner surface
Simple squamous epithelium
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Term
| How many septum, blood vessels & valves are in the heart? |
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Definition
Septum x 2
Blood vessels to and from the heart x 6
Valves x 4
Chordae tendineae
Papillary muscles |
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Term
| Describe relaxed ventricles |
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Definition
AV valves relaxed chordae tendineae are loose
Semilunar valves closed (stops back flow)
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Term
| Describe contracting ventricles |
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Definition
AV valves pushed shut by blood, chordae tendineae and papillary muscles stop them going into atria
Semilunar valves open
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Term
| What vessels are involved in coronary circulation? |
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Definition
Coronary arteries:
Right and left coronary arteries
Cardiac veins
Great cardiac vein
Coronary sinus |
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Term
| What is coronary artery disease? |
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Definition
Blockage of coronary circulation
Reduced blood flow to the heart
Results in coronary ischemia
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Term
| What is the clinical term for a heart attack? |
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Definition
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Term
| Describe what occurs during a heart attack |
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Definition
Heart has its own blood supply (coronary arteries)
When this blood supply is blocked the heart muscle cells die from lack of oxygen
Heart attack
Myocardial infarction
Death of tissue this way
Infarct
Most commonly from severe
Coronary artery disease
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Term
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Definition
Vascular Disease
Atheromas, or fibro-fatty intimal plaques |
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Term
| What occurs when a coronary artery is obstructed? |
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Definition
Depends on where the blockage is
Downstream from the obstruction dies from ischemia (loss of blood flow) and thus hypoxia (oxygen deficiency)
Temporary and reversible ischemia
Angina pectoris
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Term
| What are three investigations used for examining myocardial infarction? |
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Definition
ECG - Echo- cardiography
Cardiac enzymes
Troponin I or T
Creatinine kinase
Technetium pyrophosphate scanning
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Term
| Describe the relation of a heart beat and a pulse |
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Definition
Heart beat = 1 contraction of the heart
Pulse = the wave of blood forced out of the ventricles causing the artery walls to expand
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Term
| Describe impulse conduction through heart |
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Definition
1. The impulse begins in the pacemaker cells of the sinoatrial node and moves down along the internodal pathways in the interatrial septum (stimulates contractile cells of both atria)
2. Impulse spreads via cell-to-cell contact across the surface of the atria. Only affects atria not ventricles.
3. There is a delay at the atrioventricular node (bundle of His), which is important as the atria must contract before the ventricles do.
4. The impulse travels along the anterioventricular bundle in the interventricular septum. Then along the bundle branches to the Purkinje fibres
5. The impulse travels to the ventricular myocardium and ventricular contraction begins (atrial contraction has stopped). Papillary muscles first. Purkinje fibres second. Starts at the apex and moves towards the base ensuring blood travels out the ventricles
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Term
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Definition
| Faster than normal heart rate (based on age and activity) |
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Term
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Definition
(brady = slowness and kardía = of the heart),
In adults this is a resting heart rate below 60 bpm
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Term
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Definition
As the action potential moves through the heart the wave of depolarisation is strong enough to be detected on the surface of the skin
Placements of the ECG leads on the body affects the wave
Measures: Height of waves
Duration of waves
Relationship between different waves
Amount of depolarisation in P wave and QRS complex
E.G. Large QRS – enlarged heart
Smaller than normal electrical signal may mean the heart mass has reduced
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Term
| What waves are measured on an ECG? |
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Definition
P wave – depolarisation of the atria. The atria begin contracting after the P wave
QRS complex – ventricles depolarise. Ventricles begin contracting after the R wave
Atrial repolarisation is not seen as it occurs during QRS (ventricular contraction)
T wave – ventricular repolarisation
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Term
| What are we looking for in an ECG? |
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Definition
Segments (extend from the end of one wave to the start of the next)
P-R interval – start of atrial depolarisation to start of ventricular depolarisation (QRS)
More than 200 msec = damaged conduction pathway
Q-T interval
Ventricular de- and re- polarisation
Cardiac arrhythmias
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Term
| 4 phases of the cardiac cycle |
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Definition
Atrial systole - contraction
Atrial diastole - relaxation
Ventricular systole - contraction
Ventricular diastole - relaxation
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Term
| Describe systole and diastole |
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Definition
Systole - contraction
Diastole - relaxation
Systole - high blood pressure in chambers
Diastole - low blood pressure in chambers |
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Term
| What are the two main sounds with closing of heart valves |
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Definition
“Lubb” – Start of ventricular contraction, when atrio- ventricular valves close
“Dubb” – Start of ventricular filling when the semilunar valves close
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Term
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Definition
the volume of blood pumped out by the ventricles in one minute
About 5-6 litres per minute in adults
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Term
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Definition
The amount of blood pumped out of each ventricle with each contraction
SV = End-Diastolic volume minus End-Systolic volume
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Term
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Definition
| Amount of blood in the ventricles at the end of ventricular diastole |
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Term
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Definition
| Amount of blood in the ventricles at the end of ventricular systole |
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Term
| How is cardiac output calculated? |
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Definition
Stroke Volume x Heart Rate = Cardiac Output
eg
80 mls x 75 bpm = 6000mls per minute (6 litres)
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Term
| What are the factors that influence cardiac output? |
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Definition
Heart rate affected by:
Autonomic innervation
Hormones
Stroke volume affected by:
End-diastolic volume
End systolic volume |
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Term
| What is Autonomic innervation? |
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Definition
Sympathetic and parasympathetic divisions of the autonomic nervous system innervate the heart via the cardiac plexus
Cardioacceleratory centre (sympathetic)
Cardioinhibitory centre (parasympathetic)
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Term
| What four hormones influence cardiac output? |
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Definition
Increase heart rate by their effect on the sinoatrial node:
Epinephrine
Norepinephrine
Thyroid hormone
Increase heart rate by their effect on the contractile muscle cells:
Epinephrine
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Term
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Definition
| is the difference between the End-Diastolic Volume and the End-Systolic Volume |
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Term
| How is End-Diastolic volume influenced? |
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Definition
End-Diastolic Volume (amount of blood in a ventricle before it contracts) is influenced by:
1. Filling time - duration of ventricular diastole
Depends entirely on heart rate, fast = less filling time
2. Venous return – the rate of blood flow back to the heart
Velocity of blood flow
Pressure gradients
Sympathetic nerve activity
Skeletal muscle activity
Thoracic/abdominal pressure
Valves
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Term
| How is End-systolic volume influenced? |
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Definition
End-systolic volume (amount of blood in a ventricle after it contracts) influenced by:
1.Preload – the stretching of ventricular muscle cells during ventricular diastole (increase EDV, increased preload)
2. Contractility – the amount of force produced during a contraction (increased due to increased calcium entry into the cardiac muscle cells)
Sympathetic NS increases contractility (positive inotropic action)
Parasympathetic NS decreases contractility (negative inotropic action)
Hormones (e.g. Epinephrine) have positive inotropic actions
Drugs have positive inotropic actions (e.g. Dopamine) and negative inotropic actions (e.g. Beta-blockers)
3. Afterload – tension required to force open the semilunar valves (increased by any factor that decreases blood flow |
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Term
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Definition
The pressure exerted by blood on the walls of the blood vessels that contain it
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Term
| What is the difference between systolic and diastolic blood pressure and mean arterial pressure? |
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Definition
Systolic blood pressure (SBP) peak pressure in the arteries during cardiac systole
Diastolic blood pressure (DBP) minimum pressure in the arteries during cardiac diastole
Pulse pressure – difference between SBP and DBP
Mean arterial pressure (MAP) an estimate of the average blood pressure
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Term
| Normal arterial blood pressure: |
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Definition
SBP = 90-120 mm/Hg)
DBP = 60-80 mm/Hg
MAP = 70-95 mm/Hg
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Term
| Blood pressure is influenced by: |
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Definition
Vascular pressure gradients: pressure difference between the ends of a blood vessel
Vascular resistance: force that opposes the movement of blood through a vessel
Blood flow and velocity: volume and speed blood flows through a vessel
Venous return: amount of blood arriving at the right atrium each minute
Cardiac output and Heart rate
Baroreceptors: stimulated by changes in pressure
Chemoreceptors: stimulated by changes in checmicals
Vasomotor centre: controls blood vessel diametre
Autoregulation: local adjustment of blood flow (vasodilation) |
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