Cardiovascular system IV - cardiac cycle, sounds & rhythms Flashcards

1
Q

Systole:

A

Heart contraction

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2
Q

Diastole:

A

Heart relaxation

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3
Q

Stages of cardiac cycle:

A

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]

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4
Q

Heart _______ Flow

A

Electrical

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5
Q

Sino Atrial (SA) Node Pace Maker

A

Right side

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6
Q

Atria Ventricular (AV) node

A

Left side

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7
Q

SA node [right]

A

Specialised electrically active Myocardial tissue-Atria

Intrinsic/electrical unstable-Physiological origin of contraction

Spontaneous depolarisation,
90-100 times/min

Generates electrical activity-Impulse

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8
Q

AV node [left]

A

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)

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9
Q

Inter-nodal tracks

A

Conduction/Preferential pathways (Anterior, Middle & Posterior)

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

Converge at AV node

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10
Q

Fibrous mid line

A

No electrical conductivity

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11
Q

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

A

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

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12
Q

Purkinge Fibres

A

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

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13
Q

Vagus innervation
Para sympathetic
Slows down the SA & AV nodes

A

Supresses the heart rate

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14
Q

Sympathetic Innervation
Stimulate SA & AV nodes

A

Increases the heart rate

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15
Q

Cardiac muscle

A

99%- contractile; 1% Auto-rhythmic cells

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16
Q

Cardiac muscle structure:

A

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

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17
Q

What are the key properties of Cardiac muscle>

A
  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)
18
Q

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

A

Excitation contraction

19
Q

Where is calcium stored?

A

In the cytoplasmic reticulum

20
Q

When is calcium released

A

Durning depolarization

21
Q

Exhitation - Contraction Coupling in Contractile Myocytes

22
Q

Exhitation - Step 1 = AP

A

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

23
Q

Excitation - Step 2 Calcium enters the cells

A

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

24
Q

Exhitation - Step 3 Calcium binding

A

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

25
Exhitation - Step 4 triggers myosin
Calcium binds to troponin and triggers acting-myosin complex and contraction
26
Excitation - Step 5 calcium unbinds
Calcium unbind from troponin and pumped back into SR
27
Excitation - Step 6 relaxation
Calcium unbinding cause relaxation and excess Ca2+ exchanged with Na+
28
Excitation - Step 7 Na+ gradient maintained
Na+ gradient is maintained by sodium-potassium- ATPase pump.
29
Cardiac cells (Myocytes)
-90mV (polarised) >>> +20mV (depolarised)
30
A wave of depolarisation that begins in the SA node and spreads over the heart CAUSES...
Contraction
31
Between points P and Q there is a delay, why is this? There is a slight drop. [see in graph - 17 lec slides]
So that the blood can flow from the vein to the the ATRIUM - FILL UP
32
1st wave - P-wave
Atria depolarisation
33
QRS complex - first 3 waves
Ventricle depolarisation
34
4th wave
Ventricle repolarisation
35
What does the graph showing SINUS rhythms show?
Isoelectric signal line
36
PQRST Regular- Right Order
70-100 BPM- Sinus Rhythm < 70 BPM- Sinus Bradycardia >100 BPM- Sinus Tachycardia
37
Sinus bradycardia
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.
38
Sinus tachycardia
Rate is > 100bpm, but not usually > 130bpm at rest Occurs normally in exercise / stress. Patient is usually asymptomatic. Hypovolaemia / underlying medical problems
39
Sinus Rhythms (ECG/EKG)
ECG - the wave
40
Sinus Arrythmia
"regularly irregular" P-P intervals varies by more than 10% Heart Block/Disease Respiratory Disease