Lab 8: Cardiovascular System Flashcards
The heart is two pumps in one. What are the two pumps for? Function of each
One to pump blood to lungs (pulmonary circulation), other to pump blood to rest of tissues (systemic circulation).
Function of blood in systemic circulation?
Supplies oxygen/nutrients, carries away CO2 and waste from all tissues of body.
Function of blood in pulmonary circulation?
Take up oxygen, release CO2 through lungs.
What causes cyclic contraction of heart?
A depolarization wave originating at pacemaker and spreading through myocardium. Transmission of impulse generates electric potential which spreads to surrounding tissue.
What can influence rate of pacemaker?
ANS and chemical agents.
Define base of heart.
Cranial end
Define apex of heart.
Caudal end, slightly to the left, in contact with diaphragm.
Define ventricles.
Large posterior part, muscular chambers. L and R separated by faint groove extending obliquely across ventral surface from left of base to right of apex.
Define atria.
Two thin walled, irregularly shaped chambers at anterior end. Has auricles.
What is the coronary sulcus and what is its function?
Groove that separates atria from ventricles.
Define pulmonary trunk.
Vessels arising from right ventricle and passing toward left. Divides into right and left pulmonary arteries.
Define conus arteriosus.
Part of right ventricle that leads to pulmonary trunk.
Define aorta.
Arterial arch arising from L ventricle, dorsal to pulmonary trunk. Two major branches arise from it - brachiocephalic artery and L subclavian artery.
What is the ligamentum arteriosum and what is its function?
Short fibrous band that connects pulmonary trunk with aorta. Vestigial remains of ductus arteriosus in fetus.
Define superior vena cava.
Vein that empties into anteriodorsal side of R atrium.
Define inferior vena cava.
Vein that empties into R atrium, caudal to superior vena cava.
Define pulmonary veins.
Small vessels that empty into left atrium from lungs.
Define coronary arteries.
2 vessels on surface of heart which originate at base of aortic arch.
Define septum.
Lies between R and L halves of heart.
What can you see inside R and L atrium?
Inner surface of auricle is lined w/ parallel muscular ridges (pectinate muscle). Rest of surface is smooth.
How is R atrium separated from L atrium?
By interatrial septum.
What is located on the wall of the interatrial septum?
Fossa ovalis, oval depression.
What can you see inside R ventricle?
Internal surface of wall corrugated by muscular cords (trabeculae carneae).
What is the arterioventricular orifice and what is its function?
Oval aperture that provides communication w/ R atrium and is surrounded by tricuspid valve.
What is the chordae tendineae and what is its function?
Thin fibres that connect free border of each three cusps/flaps to muscular pillars (papillary muscles).
Where are the papillary muscles?
Anchored to wall of R ventricle.
What can you find at the opening of the pulmonary artery?
Pulmonary semilunar valves.
What can you see inside of L ventricle?
Bicuspid valve at atrioventricular orifice, which communicates w/ L atrium.
What is at opening of aorta?
Aortic semilunar valves.
5 specialized tissues associated w/ normal excitation of heart?
1) SA node - at junction of superior vena cava and R atrium
2) Atrial internodal pathway
3) AV node - in interatrial septum
4) AV bundle - bundle of His- passing into basal interventricular septum.
5) Right and left bundles.
Discuss the pacemaker activity of the SA node.
SA Node is normal pacemaker b/c of its rapid inherent rhythm. Impulses from it are conducted to depolarize other slower pacemakers and thus dominate the heart rate. Electrical activity from SA node spreads through atrial musculature creating elliptical area of depolarization. Syncytial conduction occurs in both atrial and ventricle myocardial masses, through intercalated discs where intercellular resistance at gap junctions is of such low magnitude as to allow direct electrical conduction through them.
What happens to the electrical activity from the SA node?
It spreads through atrial musculature creating elliptical area of depolarization.
What occurs in atrial and ventricle myocardial masses and what does it happen through…?
Syncytial conduction, through intercalated discs where intercellular resistance at gap junctions is at low magnitude.
Why is the intercellular resistance at low magnitude?
To allow direct electrical conduction through them.
If the SA node fails, what is the secondary pacemaker in the mammalian heart?
AV node
How do the atrial muscle fibres look surrounding AV node?
Smaller in size than elsewhere, interspersed w/ connective tissue.
Do atrial muscle fibres have high or low velocity, low or high safety factor w/ reference to conduction block?
Slow conduction velocity, low safety factor.
What are atrial muscle fibres accounted for?
The lag between atrial and ventricular depolarization.
Conduction of depolarization is syncytial through what? (4 things)
AV node, AV bundle, Purkinje fibres, ventricular musculature.
Why are 3D syncytial activation so important in ventricles?
B/c ventricles have great thickness.
What are the major factors in determining the nature of the electrocardiogram (ECG)?
Time relationship of passage of wave of depolarization throughout various regions of heart and recognition of relatively large interval between depolarization and repolarization.
What does a normal ECG of human represent?
Recording of voltage versus time.
What is the P wave in the ECG?
Low rounded upward deflection resulting from atrial depolarization.
What does the QRS complex in ECG represent and what is buried within it?
Depolarization of ventricular muscle. Buried within it is potential arising from repolarization of atria.
What does T wave in ECG represent?
Corresponds to repolarization of ventricular myocardium.
Which direction does ventricular repolarization in humans occur in respect to depolarization process?
The opposite direction. This accounts for lack of inversion of T wave and relative diminishment in its size compared to QRS complex.
Where is P-R interval measure from and what does it represent?
From beginning of P wave to beginning of QRS complex. Corresponds to time taken from excitation wave to spread from SA node to beginning of spread through ventricular musculature.
What does the QT interval represent?
Time taken from beginning of ventricular repolarization, duration depends on heart rate.
Structure of arteries?
Thicker walls to withstand pressure of blood being pumped from heart. Greater amount of smooth muscle increases strength and elasticity.
Structure of veins?
Wider inner diameters to hold more accumulated blood since blood does not flow back to heart as fast as it is pumped out. One-way valves to prevent backflow.
