The Cardio Vascular System - Cardiac Cycle, Sounds, Rhythms (w8)

Question 1

What is a systole ?

Answer 1

Heart contraction

Question 2

What is a diastole ?

Answer 2

Heart relaxation

Question 3

What are the three main phases to the cardiac cycle ?

Answer 3

1) ventricular filling
2) ventricular systole
3) early diastole

Question 4

What happens during the ventricular ejection phase ?

Answer 4

The blood is ejected forcefully though the semi lunar valves, through aorta and pulmonary artery.

Question 5

What causes the LUBb (s1) sound in the isovolumetric conraction phase of the cardiac cycle ?

Answer 5

The closure of the AV valves

Question 6

What causes the DUBb (s2) sound in the isovolumetric contraction phase of the cardiac cycle ?

Answer 6

The closure of the SL valves

Question 7

What is sound 3 in the early vertical area filling phase of the cardiac cycle caused by ?

Answer 7

Th tensing of the chordae tendineae and the atrioventricular ring.
Adults : ventricular systole failure, normal in children

Question 8

What causes sound 4 in the atrial contraction phase of the cardiac cycle ?

Answer 8

The vibration of the ventricular wall, stiff verticle, hypertrophy or ischemic ventricle

Question 9

What are the two main heart sounds ?

Answer 9

Sound 1 - LUBb
Sound 2 - DUBb

Question 10

What happens at the (SA) Sino Atrial node (pace-maker) ?

Answer 10

• There is specialized electrically active myocardial tissue found in the atria. You can also find pacemaker cells in the right atrium which involuntarily generate pulses.
• spontaneous depolarization occurs around 90-100 times/min
• overall in generates electrical activity- impulse

Question 11

What are contractile myocytes ?

Answer 11

Cardiac cells

Question 12

What is vagus inner action responsible for ?

Answer 12

Reducing heart beat.
- is parasympathetic
- slows down SA and AV nodes

Question 13

What do the SA node and AV act as ?

Answer 13

• SA = pacemaker
• AV = collecting node

Question 14

What does sympathetic innervation do ?

Answer 14

Stimulated the AV and SA nodes

Question 15

What is composition of cardiac muscle ?

Answer 15

-99% contractile
-1% autorhythmic cells

Question 16

What happens at the gap junctions between cardiac muscle cells ?

Answer 16

Depolarization of the cells just to generate action potential and give stimulus for calcium to be released causing muscle contraction.

Question 17

What occurs at the demosomes ?

Answer 17

They hold the muscle fibers together during muscle contraction

Question 18

What are the 4 key properties of the cardiac muscle ?

Answer 18

1) auto-rhythmicity : ability to initiate heartbeat, consistent and continuous at regular pace without any external stimuli.
2) excitability : ability to respond to stimuli of adequate strength and duration (threshold or more) and the ability to generate and process action potentials.
3) conductivity : ability to conduct and transmit impulse through the cardiac tissue.
4) contractility : ability to contract in repose to a stimulation (mechanical)

Question 19

Describe the excitation process of contraction coupling in contractile myocytes …

Answer 19

1)AP from adjacent cell excites myocytes and trigger membrane depolarisation in T-tubules.
2)Calcium enter the cells via voltage gated channel opens and calcium enters the cells
3)Calcium binds to Ryanodine receptor (RYR) and induce Calcium release from SR
4)Calcium binds to troponin and triggers acting-myosin complex and contraction
5)Calcium unbind from troponin and pumped back into SR
6)Calcium unbinding cause relaxation and excess Ca2+ exchanged with Na+
7)Na+ gradient is maintained by sodium-potassium- ATPase pump

Question 20

During a sinus rhythm (ECG/EKG) what do the following equate to: p wave, QRS complex and T wave ?

Answer 20

P wave - atria depolarisation
QRS complex - ventricle depolarization
T wave - ventricle repolarisation

Question 21

What is sinus bradycardia ?

Answer 21

When the hearty rate is less than 60bpm (not usually less than 40bpm)
- patients usually are asymptomatic and no treatment is required.
- can be caused by hypertension drug e.g. beta-blockers / calcium channel blocker (amlodapine)
- may also be seen in athletes and occur during sleep.

Question 22

What is sinus tachycardia ?

Answer 22

Rate is > 100bpm, but not usually > 130bpm at rest
-Occurs normally in exercise / stress.
-Patient is usually asymptomatic.
-Hypovolaemia / underlying medical problems

Question 23

What are conduction and contraction in cardiac cells coordinated by ?

Answer 23

Both mechanical and electrical activity.