Applied anatomy of the heart Flashcards
What 3 types of fibres make up the cardiac plexus?
1) General visceral afferent
2) Parasympathetic via vagus
3) Sympathetic via sympathetic trunk
Effect of parasympathetic nervous system on the heart
Reduces heart rate and reduces force of contractability
Stimulates cardioinhibitory centre
Effect of sympathetic nervous system on the heart
Increases heart rate and increases force of contractibility
Stimulates cardioaccelaratory centre
Where does cardioinhibitory centre send axons to?
SAN and AVN
Where do you find pre and post ganglionic axons from cardioaccelaratory centre
Pre= thoracic spinal cord Post= Neurons to AVN and SAN
Where do you find cardioinhibitory and cardioacceleratory centres
In the reticular formation of the medulla
Describe the anatomical position of the cardiac plexus
Anterior to bifurcation of the trachea
Posterior to arch of the aorta
What causes cardiac pain
Ischaemia which stimulates sensory nerve endings in myocardium
Where is cardiac pain usually referred to
T1-T4
Somtimes T5-T9
Why is cardiac pain referred?
Somatic afferents from skins ascend in the same spinal segment as visceral sensory fibres- brain confuses the signals
From where is coronary circulation derived?
Ascending aorta
What does the left coronary artery divide into
Left marginal
Left anterior descending/ anterior interventricular
Circumflex
What does the right coronary artery divide into
Right marginal
Which vessel supplies the SAN
right coronary artery
Which vessel ‘decides’ the dominance of the heart- how
Posterior interventricular
If it comes mainly from right coronary artery= right dominance
If it comes mainly from circumflex= left dominance
Where are conducting fibres of the heart found
Interventricular septum
Describe distribution of blood supply to interventricular septum
LAD provides anterior 2/3
PDA provides posterior 1/3
What is bundle branch block
Ischaemic bundle branch ceases to properly conduct so uses altered pathways for depolorisation eg through myocytes
Effect of bundle branch block
Depolarisation is slower
Prolonged QRS
Loss of ventricular synchrony
Define atrial remodelling
Any persistent change in atrium structure
Define cardiac remodelling
Structural changes associated with cardiac dynsfunction (increased myocyte mass)
Define cardiac dysfunction
Altered relationship between preload and stroke volume
3 main causes of pathological remodelling
Pressure overload, volume overload and cardiac injury
What can causes pressure overload
hypertension and aortic stenosis
What can cause volume overload
Caused by valvular regurgitation or hypervolaemia
Define valvular regurgitation
Backward flow so increased volume in the first chamber
Define hypervolaemia
Increased fluid levels in the blood
5 molecular changes that occur during ventricular hypertrophy
- Increased sarcomeres
- Synthesis of abnormal proteins
- Decreased capillary: myocyte
- Apoptosis of myocytes
- Increased fibrous tissue
What is concentric hypertrophy
Thickening of the ventricular wall due to the paralell addition of sarcomeres
What is eccentrial hypertrophy
Dilation of the ventricular wall due to the addition of sarcomeres in sequence
Main causes of each type of ventricular hypertrophy
Concentric= aortic stenosis, chronic hypertention Eccentric= aortic and mitral regurgitation, systolic dysfunction, hypervolaemia
Effect of concentric hypertrophy
Increased afterload, less compliant, compromised ventricular filling
Effect of eccentric hypetrophy
Increased oxygen demands, decreased mechanial effects
What happens to cusps and cordae tendonies during rheumatic disease
Cusps fibrose
Cordae tendinae soften
What is mitral regurgitation and its two most common causes
Abnormal regurgitation in left atrium
MItral valve prolapse, rheumatic heart disease
Effect of mitral regurgitation
Reduced CO, pulmonary oedema
Describe murmur heard for mitral regurgitation
Mitral closed throughout
Pansystolic (louder at late systole)
Heard at apex
Why does aortic stenosis lead to concentric ventricular hypertrophy
Left ventricle has to generate increased pressure in order to overcome increased afterload. INcreased muscle mass allows ventricle to generate increased force necessary to propel blood past obstruction
Describe murmur heard with aortic stenosis
Turbulence as blood pushing through stenotic aortic valve
Mid systolic typically
Heard at tight intercostal space
Is aortic stenosis murmur more or less severe if heard early or late
Late- time taken to generate pressure to pass through stenotic valve
Effect of mitral valve stenosis (4)
- L atrium needs higher pressure to overcome stenosis
- Atrial kick larger leading to atrial enlargement and increased pressure leading to oedema
- Reduced ventricular filling, reduced CO
- Can lead to AF
Describe murmur of mitral stenosis
Diastolic murmur
Soft and rumbling
Effect of aortic regurgitation
Blood goes back into the LV during diastole
Chronic volume overload–> stretching and elongation of myocardial fibres
LV dilation
Decreased CO
Increased preload
Describe murmur of aortic regurgitation
Rheumatic
Complex and absent
Where does the cardiac plexus of nerves flie
Anterior to bifurcation of the trachea
Posterior to arch of the aorta
What makes up the anterior and posterior/ base surface of heart
Anterior= mainly right ventricle Posterior= Left atrium (some right atrium)
What makes up the diaphgramatic surface of heart
RV/LV
Mainly LV
Which coronary artery is most commonly occluded
LAD
Which ECG leads give information about LAD
V1, V2, V3, V4`
What ECGS leads give information about the diagonal branch of LAD
1, avL, V5, V6
What ECG leads give info about RCA
2,3 avF
Name 4 leads that give lateral view of the heart
1, aVL
v5, v6
Name 3 leads that give inferior view of the heart
2, 3, aVF
Name 2 leads that give view of the septum
V1. V2
Name 2 leads that give anterior view of the heart
V3, V4
