Cardiovascular Principles Flashcards
How do we treat a cardiac tamponade?
Pericardiocentesis
Pericardial cavity fills with blood?
Haemopericardium/Cardiac tamponade
What are the branches of the arch of aorta (from right to left)?
Brachiocephalic trunk
Left common carotid
Left subclavian a.
From right to left, what order do the great vessels appear when look at the anterior surface of the heart?
SVC
Aorta
Pulmonary trunk
What is the coronary sinus?
Venous conduit
Drains cardiac veins to RA
Do the coronary arteries arrive just above or just below the aortic valve?
Just above
Which artery supplies the RV?
Right marginal artery
Which artery supplies the posterior interventricular septum?
Posterior descending artery (r. coronary artery branch)
What artery supplies the posterolateral LV?
Circumflex artery (l. coronary branch)
What does the left anterior descending artery supply?
Anterolateral myocardium
Apex
Interventricular septum
What causes the first heart sound?
Tricuspid and mitral valve shutting
What causes the second heart sound?
Aortic and pulmonary valves shutting
When sympathetic nerves leave the spinal cord, what can they do?
Go into ganglion at that level
Travel in sympathetic chain
Pass through without synapsing then synapse at prevertebral ganglia
Pass to adrenal medulla
What does autonomic innervation of the heart do?
Increase heart rate
Increase contractility
What does parasympathetic innervation of the heart do?
Decrease heart rate
What afferent nerves are present in the arch of aorta?
Baroreceptor reflex afferents in vagus nerve
Where are visceral afferent nerves located in the heart?
Inner aortic arch PT Around SA node Outflow tracts of RV and LV Papillary muscles SVC and IVC
Where do somatic sensory action potentials travel to?
Postcentral gurus
Of the parietal lobe
In the cerebral cortex
Where are somatic motor sensations relayed back from?
Precentral gurus
Of the frontal lobe
What is phase 4/Funny current of the pacemaker potential?
Slow sodium ion influx
Decreased potassium ion efflux
What occurs in rapid depolarisation and what phase is this in the pacemaker AP?
Rapid calcium ion influx
Phase 0
What happens during repolarisation and what phase is this?
Increased potassium ion efflux
Phase 3
Describe the spread of excitation in the heart
From SA node to AV node
From SA node through both atria
From AV node through bundle of His
From bundle of His through Purkinje fibres
What type of cell junctions allow easy conduction in the heart?
Gap junctions
What three junctions form an intercalated disc as seen in heart muscle?
Gap junctions
Desmosomes
Fascia adherens
Where is the SA node located?
Near entrance of SVC into RA
Where is the AV node located?
At base of RA near junction to RV
What are each of the phases in the ventricular muscle action potential?
Phase 0 - Rapid Na influx Phase 1 - Slow potassium efflux Phase 2 - Plateau due to Calcium influx Phase 3 - Rapid potassium efflux Phase 4 - Resting membrane potential (-90mV)
Why is the intrinsic heart rate slowed from ~100bpm to ~70bpm?
Continuous vagal tone influences SA node at rest
What is defined as sinus bradycardia?
<60bpm
What is defined as sinus tachycardia?
> 100bpm
What effects does the vagus nerve have on the heart?
Decreased SA node firing
Increased AV nodal delay
How does atropine work?
Inhibits ACh to increase HR
What effect does the vagal tone have on the pacemaker potential slope?
It is decreased
So it takes longer to reach threshold - Negative chronotropic can effect
What noradrenergic receptors play the biggest role in the heart?
Beta1
What effect does NA have on the heart pacemaker potential?
Increases slope
What is the role of desmosomes?
Provide mechanical adhesions
Ensure tension is transmitted cell to cell
What two filaments are Myofibrils made from?
Myosin (thick and dark)
Actin (thin and lighter)
How are the filaments in myofibrils arranged?
Into sarcoma reds
What is the A band?
Length of myosin
What is the I band?
Section containing only actin
What is the H zone?
Area of myosin only (ie no actin overlap)
How is a single sarcomere defined?
Segment between two Z lines
Briefly describe the process of a power stroke
In the presence of calcium ions, myosin cross bridge binds to actin
ATP on myosin is hydrolysed, bending the cross bridge
Actin pulled along
In presence of ATP, it binds to myosin
Myosin detaches and realigns
What occurs in the absence of further ATP during the power stroke?
Rigor mortis
Why are calcium ions required for initiation of the power stroke?
Pulls away the troponin-tropomyosin complex to allow myosin-actin binding
During systole, where do the calcium ions come from?
Calcium ions influx into cell
Calcium induced calcium release (CICR) from sarcoplasmic reticulum
(Contraction)
What happens to the calcium ions in the cell during diastole?
Calcium influx ceases
Calcium ions re-sequestered into SR by Calcium-ATPase
(Relaxation)
What is the refractory period?
Period of time after an AP when another cannot be generated
What is the equation for the stroke volume?
SV = EDV - ESV
What intrinsic factors determine the end diastolic volume and hence stroke volume?
Venous return
Preload
What is the preload of the heart?
The end diastolic pressure that stretches the ventricles ie the greatest length of the sarcomeres
What is the afterload of the heart?
The resistance into which it pumps
How does sympathetic stimulation increase the force of contraction?
Activated calcium channels
Greater calcium influx
How does sympathetic stimulation increase the HR?
Increased peak ventricular pressure - increased rate of change - decreased duration of systole
Increased rate of ventricular relaxation due to increased calcium efflux - decreased duration of diastole
At 75bpm, what is the approximate length of
- Diastole
- Systole
- 0.5s
2. 0.3s
What are the five events in the cardiac cycle?
- Passive filling
- Atrial contraction
- Isovolumetric ventricular contraction
- Ventricular ejection
- Isovolumetric ventricular relaxation
How full do the ventricles become during passive filling (%)?
80%