CVS physiology 1 Flashcards
What is pressure difference equal to?
Mean arterial pressure - central venous pressure.
What is resistance of blood vessels controlled by?
Radius of blood vessel to the power of 4
How is the blood flow of vascular beds arranged?
In parallel
What is the main structural difference between the aorta and other arteries?
Aorta = elastic wall
Arteries = muscular wall
What do veins act as?
Capacitance vessels
What do arterioles act as?
Resistance vessels
What is the comparison in time of an action potential in cardiac muscle and skeletal muscle?
Cardiac muscle - 250msec
Skeletal muscle - 2msec
Why is it important for cardiac muscle to create a long action potential?
Long action potential creates a long refractory period, preventing tetanus contraction
In cardiac muscle, what does the release of Ca2+ regulate?
Strength of contraction
What is a distinct feature of pacemaker cells?
Unstable resting membrane potential
What causes the initial depolarisation in non-pacemaker cells?
Increased permeability to Na+
What causes the plateau in non-pacemaker cells?
Increased permeability to Ca2+ (L type)
Decreased permeability to K+
What causes the repolarisation in non-pacemaker cells?
Decreased permeability to Ca2+
Increased permeability to K+
What causes an action potential in pacemaker cells?
Increased permeability to Ca2+ (L type)
What causes the pacemaker potential?
Gradual decreased permeability to K+
Early increased permeability to Na+ (F type)
Late increased permeability to Ca2+ (T type)
Where are the fastest pacemaker cells usually located?
Sinoatrial node
Where is the sinoatrial node located?
In the upper wall of the right atrium
What is the atrioventricular node?
It generates an electrical charge that causes the ventricles to contract
What is the only non-conducting part of the heart?
Annulus fibrosis
What creates almost simultaneous contraction in the ventricles?
Bundle of his and purkinje fibres
What creates the delay between atrial and ventricular contraction?
Atrioventricular node
What creates the P wave in an ECG?
Atrial depolarisation (contraction)
What creates the QRS complex in an ECG?
Ventricular depolarisation (contraction)
What creates the T wave in an ECG?
Ventricular repolarisation (relaxation)
What does SLL II ECG record?
Potential difference of left leg with respect to right arm
What is the PR interval?
Beginning of P wave to beginning of QRS complex (normally 0.12-0.2 secs)
What is normal time for QRS complex?
0.08 secs
What is the QT interval?
Beginning of QRS complex to end of T wave (normally 0.42 secs at 60bpm)
Why is there an initial dip in the QRS complex?
As the interventricular septum depolarises from left to right (away from left leg)
What creates the spike in the QRS complex?
most of the ventricle depolarises from the endocardial to the epicardial surface (travelling in direction of left leg)
