CVS physiology 1

Question 1

What is pressure difference equal to?

Answer 1

Mean arterial pressure - central venous pressure.

Question 2

What is resistance of blood vessels controlled by?

Answer 2

Radius of blood vessel to the power of 4

Question 3

How is the blood flow of vascular beds arranged?

Answer 3

In parallel

Question 4

What is the main structural difference between the aorta and other arteries?

Answer 4

Aorta = elastic wall

Arteries = muscular wall

Question 5

What do veins act as?

Answer 5

Capacitance vessels

Question 6

What do arterioles act as?

Answer 6

Resistance vessels

Question 7

What is the comparison in time of an action potential in cardiac muscle and skeletal muscle?

Answer 7

Cardiac muscle - 250msec

Skeletal muscle - 2msec

Question 8

Why is it important for cardiac muscle to create a long action potential?

Answer 8

Long action potential creates a long refractory period, preventing tetanus contraction

Question 9

In cardiac muscle, what does the release of Ca2+ regulate?

Answer 9

Strength of contraction

Question 10

What is a distinct feature of pacemaker cells?

Answer 10

Unstable resting membrane potential

Question 11

What causes the initial depolarisation in non-pacemaker cells?

Answer 11

Increased permeability to Na+

Question 12

What causes the plateau in non-pacemaker cells?

Answer 12

Increased permeability to Ca2+ (L type)

Decreased permeability to K+

Question 13

What causes the repolarisation in non-pacemaker cells?

Answer 13

Decreased permeability to Ca2+

Increased permeability to K+

Question 14

What causes an action potential in pacemaker cells?

Answer 14

Increased permeability to Ca2+ (L type)

Question 15

What causes the pacemaker potential?

Answer 15

Gradual decreased permeability to K+

Early increased permeability to Na+ (F type)

Late increased permeability to Ca2+ (T type)

Question 16

Where are the fastest pacemaker cells usually located?

Answer 16

Sinoatrial node

Question 17

Where is the sinoatrial node located?

Answer 17

In the upper wall of the right atrium

Question 18

What is the atrioventricular node?

Answer 18

It generates an electrical charge that causes the ventricles to contract

Question 19

What is the only non-conducting part of the heart?

Answer 19

Annulus fibrosis

Question 20

What creates almost simultaneous contraction in the ventricles?

Answer 20

Bundle of his and purkinje fibres

Question 21

What creates the delay between atrial and ventricular contraction?

Answer 21

Atrioventricular node

Question 22

What creates the P wave in an ECG?

Answer 22

Atrial depolarisation (contraction)

Question 23

What creates the QRS complex in an ECG?

Answer 23

Ventricular depolarisation (contraction)

Question 24

What creates the T wave in an ECG?

Answer 24

Ventricular repolarisation (relaxation)

Question 25

What does SLL II ECG record?

Answer 25

Potential difference of left leg with respect to right arm

Question 26

What is the PR interval?

Answer 26

Beginning of P wave to beginning of QRS complex (normally 0.12-0.2 secs)

Question 27

What is normal time for QRS complex?

Answer 27

0.08 secs

Question 28

What is the QT interval?

Answer 28

Beginning of QRS complex to end of T wave (normally 0.42 secs at 60bpm)

Question 29

Why is there an initial dip in the QRS complex?

Answer 29

As the interventricular septum depolarises from left to right (away from left leg)

Question 30

What creates the spike in the QRS complex?

Answer 30

most of the ventricle depolarises from the endocardial to the epicardial surface (travelling in direction of left leg)