Cardiovascular system IV - cardiac cycle, sounds & rhythms

Question 1

Systole:

Answer 1

Heart contraction

Question 2

Diastole:

Answer 2

Heart relaxation

Question 3

Stages of cardiac cycle:

Answer 3

1) Ventricular filling
Atrial contraction [ventricular filling mid-t-late diastole]

2) Isovolumetric contraction phase
Ventricular ejection phase [Ventricular systole - atria in diastole]

3) Isovolumeric relaxation [early diastole]

Question 4

Heart _______ Flow

Answer 4

Electrical

Question 5

Sino Atrial (SA) Node Pace Maker

Answer 5

Right side

Question 6

Atria Ventricular (AV) node

Answer 6

Left side

Question 7

SA node [right]

Answer 7

Specialised electrically active Myocardial tissue-Atria

Intrinsic/electrical unstable-Physiological origin of contraction

Spontaneous depolarisation,
90-100 times/min

Generates electrical activity-Impulse

Question 8

AV node [left]

Answer 8

Specialised electrically active Myocardial tissue- Atria-Ventricular mid line

Generates electrical activity-Impulse

Intrinsic/electrical unstable-

Spontaneous depolarisation,
Lower than SA (40-60 times/min)

Question 9

Inter-nodal tracks

Answer 9

Conduction/Preferential pathways (Anterior, Middle & Posterior)

Carry pulse, depolarise and contract atria (right and left)

Converge at AV node

Question 10

Fibrous mid line

Answer 10

No electrical conductivity

Question 11

Bundle of HIS (AV bundle)
The border between the two ventricles

Answer 11

Collect and carry to higher and lower part of the ventricles (Apex); 20-40 times/min

Question 12

Purkinge Fibres

Answer 12

Specialised myocardium for electrical conduction (not contraction) towards contractile myocytes (cardiac cells)

Question 13

Vagus innervation
Para sympathetic
Slows down the SA & AV nodes

Answer 13

Supresses the heart rate

Question 14

Sympathetic Innervation
Stimulate SA & AV nodes

Answer 14

Increases the heart rate

Question 15

Cardiac muscle

Answer 15

99%- contractile; 1% Auto-rhythmic cells

Question 16

Cardiac muscle structure:

Answer 16

Striated type, branched muscle fibers (myofibrils) contains single nucleus, many mitochondria and T-tubules

Connected by intercalated disks
Gap junctions- Depolarisation between cells
Desmosomes- Hold fibers together during contraction

Question 17

What are the key properties of Cardiac muscle>

Answer 17

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)
   Ability to generate and process action potential
3. Conductivity = Ability to conduct and transmit impulse through the cardiac tissue
4. Contractility = Ability to contract in response to stimulation (mechanical)

Question 18

Action p in the myocytes triggers the L type calcium to enable to bind to the RYR.

Answer 18

Excitation contraction

Question 19

Where is calcium stored?

Answer 19

In the cytoplasmic reticulum

Question 20

When is calcium released

Answer 20

Durning depolarization

Question 21

Exhitation - Contraction Coupling in Contractile Myocytes

Answer 21

7 steps

Question 22

Exhitation - Step 1 = AP

Answer 22

AP from adjacent cell excites myocytes and trigger membrane depolarisation in T-tubules

Question 23

Excitation - Step 2 Calcium enters the cells

Answer 23

Calcium enter the cells via voltage gated channel opens and calcium enters the cells

Question 24

Exhitation - Step 3 Calcium binding

Answer 24

Calcium binds to Ryanodine receptor (RYR) and induce Calcium release from SR

Question 25

Exhitation - Step 4 triggers myosin

Answer 25

Calcium binds to troponin and triggers acting-myosin complex and contraction

Question 26

Excitation - Step 5 calcium unbinds

Answer 26

Calcium unbind from troponin and pumped back into SR

Question 27

Excitation - Step 6 relaxation

Answer 27

Calcium unbinding cause relaxation and excess Ca2+ exchanged with Na+

Question 28

Excitation - Step 7 Na+ gradient maintained

Answer 28

Na+ gradient is maintained by sodium-potassium- ATPase pump.

Question 29

Cardiac cells (Myocytes)

Answer 29

-90mV (polarised)&raquo_space;> +20mV (depolarised)

Question 30

A wave of depolarisation that begins in the SA node and spreads over the heart CAUSES…

Answer 30

Contraction

Question 31

Between points P and Q there is a delay, why is this? There is a slight drop.

[see in graph - 17 lec slides]

Answer 31

So that the blood can flow from the vein to the the ATRIUM - FILL UP

Question 32

1st wave - P-wave

Answer 32

Atria depolarisation

Question 33

QRS complex - first 3 waves

Answer 33

Ventricle depolarisation

Question 34

4th wave

Answer 34

Ventricle repolarisation

Question 35

What does the graph showing SINUS rhythms show?

Answer 35

Isoelectric signal line

Question 36

PQRST Regular- Right Order

Answer 36

70-100 BPM- Sinus Rhythm
< 70 BPM- Sinus Bradycardia
>100 BPM- Sinus Tachycardia

Question 37

Sinus bradycardia

Answer 37

The rate is <60bpm
(not usually <40bpm)

Patients usually asymptomatic and no treatment is required

beta-blockers / calcium channel blockers
May also be seen in athletes and occur during sleep.

Question 38

Sinus tachycardia

Answer 38

Rate is > 100bpm, but not usually > 130bpm at rest

Occurs normally in exercise / stress.

Patient is usually asymptomatic.

Hypovolaemia / underlying medical problems

Question 39

Sinus Rhythms (ECG/EKG)

Answer 39

ECG - the wave

Question 40

Sinus Arrythmia

Answer 40

“regularly irregular”

P-P intervals varies by more than 10%

Heart Block/Disease
Respiratory Disease