Cardiovascular Flashcards
What is the pericardium? What are its layers?
A tough, double-layered fibroserous sac which covers the heart.
It’s layers are:
- Fibrous pericardium: this is the most superficial layer, has loose and dense connective tissue and protects the heart, fixes it and prevent over filling
- Serous pericardium: has two layers, parietal (fused to the fibrous) and visceral (part of epicardium) both have a lubricating function
What artery supplies the Sino Atrial Node?
The right coronary artery (60%)
What artery supplies the Atrioventricular Node?
Posterior interventricular artery.
This arises from:
70% - Right coronary artery
20% - Right & Left coronary arteries
10% - Left coronary artery
Where can the apex beat be heard?
Left of the sternum, 5th intercostal space, mid-clavicular line
What is on the right heart border?
1) Superior Vena Cava
2) Right atrium
What is on the left heart border?
1) Aortic knuckle
2) Left pulmonary artery
3) Left auricle
4) Left ventricle
What is the anterior border of the heart?
Right ventricle
What is the posterior border of the heart?
Left atrium & pulmonary veins
What is the mediastinum?
Area between the right and left pleura
Where what divided the mediastinum into superior and inferior?
Plane between eternal angle & T4/5 vertebrae
How is the mediastinum into anterior, middle & superior?
By pericardium
Where would you find the SA node?
A long cresent shaped area in the crusts terminal is at the superior border of the right atrium
Where is the AV node located?
A small nodule just above the septal cusp of the tricuspid value in the inter-atrial septum
What is the thoracic duct?
A channel draining lump from below the diaphragm and above the diaphragm on the left side. It drains the lymph into the junction between the left subclavian vein and left internal jugular vein.
What is the nerve root of the greater splanchnic nerve? What does it supply?
T5-9
Supplies the foregut
What are the nerve roots of the lesser splanchnic nerve? What does it supply?
T10 & T11
Mid gut
What is the nerve root of the least splanchnic nerve? What does it supply?
T12
Hindgut
What level does the bifurcation of the aorta occur?
L4
Why is heart pain referred and where to?
Neck, shoulders, jaw, arms and stomach.
Because the heart’s sensory supply is from the cardiac plexus made up of spinal nerves T1-T4 so pain is felt in the dermatomes supplied by these nerves
What is involved in cardiac muscle contraction but not in skeletal muscle contraction (or to a lesser extent)
Calcium-induced calcium release: this is where an increase in Ca2+ in the cell causes more calcium release (part of the early plateau phase)
What are the two main baroreceptors?
1) Carotid sinus
2) Aortic Arch baroreceptors
What happens if the blood pressure decreases through baroreceptor detection?
Decreased pressure > decreased discharge rate > Fewer action potentials to medullary cardiovascular centre
This leads to:
- Increased hear rate (^symp)
- Increased contractibility (^symp)
- Arteriolar construction (^symp + angiotensin II & ADH release)
- Increased venous constriction (^symp)
What are the local factors that cause vasoconstriction?
1) Endorhelin - peptide produced by endothelium with causes constriction
2) myogenic contraction of blood vessels
What are the local factors for vasodilation?
Hypoxia Hypercapnia Decreased pH Bradykinin Increased K+ Nitric oxide Tissue breakdown products
What are the hormonal factors for vasoconstriction?
Angiotensin II
Vasopressin (ADH)
Adrenaline
What hormonal factors that cause vasodilation?
Adrenaline
ANP
How is CO2 transported in the blood?
1) In blood plasma - 10% of CO2
2) By haemoglobin - 25-30% of CO2 (combines reversible to deoxyhaemoglobin to form carbaminohaemoglobin)
3) As hydrogen bicarbonate - 60-65%
How are the hydrogen ions, produced from the production of hydrogen bicarbonate, transported?
Binds to deoxyhaemoglobin (of which it has greater affinity to than oxy), when deoxyhaemoglobin becomes oxy haemoglobin in the lungs it releases H+
This combines to bicarbonate
The carbonic acid is then catalysed by carbonic anhydrase to CO2 and H2O
CO2 then diffuses and is breathed out
What is the structure of the heart tube starting form aortic sac?
Aortic sac Bulbus Cordis Ventricle Atrium Sinus venosus Horns of sinus venosus Common Cardinal arteries
What happens in cardiac looping?
Cephalic portion: moves ventral, caudal and to the right
Atrial portion: moves dorsocranially and to the left
What is meant by preload?
The volume of blood in the left ventricle that stretches the cardiac myocytes before contraction
What is meant by after load?
The pressure again the wall of the left ventricle that must be overcome
What is meant by contractibility?
The force of contraction and change in fibre length
What is meant by elasticity in terms of the heart?
Ability to recover normal shape after systolic stress
What is Diastolic distensibility?
The pressure required to fill the ventricle to the same diastolic volume
What is meant by compliance?
How easily the heart chamber expands when filled with blood
What is formed from the 1st aortic arch?
Maxillary artery
What is formed from the 2nd aortic arch?
Hyoid and Stapedial arteries
What is formed from the 3rd aortic arch?
Common carotid artery and first part of internal carotid
What is formed from the 4th aortic arch?
Left: Part of the arch of the aorta
Right: Right subclavian artery
What is formed from the 5th aortic arch?
There isn’t one
What is formed from the 6th aortic arch?
Left: Left pulmonary artery and ductus arteriosus
Right: Right pulmonary artery
What is the nernst equation?
E = 60 log (concentration outside/concentration inside)
What does the the nerest equation calculate?
The potential associated with ionic concentration gradients
What pump is responsible for the membrane potential?
Na+/K+ pump
What is responsible for the action potential spike (depolarisation)?
Voltage gated Na+ channels opening (influx of Na+)
What is responsible for the prolongation of the action potential?
Voltage gated Ca2+ channels opening (influx of Ca2+)
What is responsible for the repolarisation?
Voltage gated K+ channels opening (outflow of K+)
What happens to the voltage gated Na+ channels when the voltage alters?
They change shape
At what voltage do the voltage gated Na+ channels open?
Between -70mV and -50mV
What inactivates the Na+ channels?
They close after a short period of time - time controlled closure
Whta re the characteristic features of the voltage gated calcium channels?
1) Slower than the fast Na+ channels
2) Remain open longer
3) Na+ also passes through them
What are the voltage gated calcium channels responsible for?
The plateau phase
What ion/s are moving in phase 0?
Na+ - IN
What ion/s are moving in phase 1?
K+ and Cl- - OUT
What ion/s are moving in phase 2?
Ca2+ - IN
K+ - OUT
What ion/s are moving in phase 3?
K+ - OUT
What ion/s are moving in phase 4?
K+ - IN
Na+ - OUT
List the three structures that the action potential passes through into the cell in excitation contraction coupling
1) Membrane
2) Transverse tubules
3) Sarcoplasmic reticulum
What happens as a result of the arrival of the action potential in excitation contraction coupling?
Ca2+ is released
Where is the Ca2+ released from?
1) T tubules (unique to heart)
2) Sarcoplasmic reticulum (as in skeletal muscles)
Whta is the role of Ca2+ presence in the sarcoplasm?
It causes muscle contraction through allowing the binding of myosin head to actin
Briefly describe the propagation of the action potential in cardiac cells
1) Action potential spreads over cell membrane
2) Positive charge from Na+ affects adjacent cells
3) Depolarisation occurs
4) Newly depolarised cells also cause depolarisation
How do the ions travel between cardiac myocytes?
Directly through gap junctions
What is the speed of conduction in atrial and ventricular fibres?
0.3 to 0.5 m/s
What is the speed of conduction in purkinje fibres?
4m/s
What is the role of the SA node?
Determines the rate at which the heart beats - it initiates depolarisation
What is the resting membrane potential for the SA node?
-55 to -60 mV
Describe the generation of the action potential in the SA node
1) Slow Na+ inflow
2) Membrane potential moves towards threshold for discharge
3) Fast Na+ channels close
4) Action potential driven by Ca2+ channels (inflow)
5) Repolarisation occurs through K+ Outflow
What does automaticity mean in relation to cardiac myocytes?
That they have the ability to genertae an action potential and depolarise themselves
How does automaticity vary in the heart cells?
Greatest in the SA node, rate of spontaneous discharge decreases down the heart
The AV node delays the impulse from the atria to the ventricles, why?
It allows atria to empty all the blood into the ventricles
How does the AV node delay impulses?
1) There are less gap junctions in the AV node
2) The fibres of the AV node are smaller than the atria fibres
What happens in the absolute refractory period in the heart in terms of the membrane?
The Na+ and Ca2+ channels are closed
What is the normal refractory period of the ventricles?
0.25s
What is the role of the absolute refractory period?
1) Prevents excessive contraction
2) Allows time for the heart to fill
Does the relative refractory period occur before or after the absolute?
After
What causes there to be a relative refractory period?
1) Some Na+ channels are still inactivated
2) K+ channels are still open
What does the relative refractory period mean?
That only strong stimuli can cause an action potential
What does the sympathetic input do to the heart?
1) Increases heart rate
2) Increases force of contraction
3) Increases cardiac output
What does the parasympathetic input do to the heart?
1) Decreases heart rate
2) Decreases force of contraction
3) Decreases cardiac output
What is the term used that means something increases/decreases heart rate?
Positively chronotropic
What is the term used that means something increases/decreases force of contraction?
Positively inotropic