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PMP101 - Health, Disease and Patient > cardiac cycle > Flashcards

cardiac cycle Flashcards

1
Q

What does the cardiac cycle consist of?

A
  • contraction = systole
    *relaxation = diastole
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2
Q

What stages occur in the mid to late diastole?

A

*ventricular filling
*atrial contraction

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3
Q

What stages occur in the ventricular systole?

A

*isovolumetric contraction point
*ventricular ejection phase

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4
Q

What phase happens in early diastole?

A

*isovolumetric relaxation

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5
Q

What happens during ventricular (atrial) filling?

A

*atrial diastole
*ventricular diastole
Relaxation Phase: Both the atria and ventricles are in a relaxed state, allowing them
to fill with blood.
*Blood Inflow: The atria receive blood from the body and lungs, while the ventricles
passively fill with blood from the atria.
*Atrioventricular Valves: The tricuspid and mitral valves remain open to facilitate the
flow of blood into the ventricles.

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6
Q

What happens in atrial diastole?

A

*relaxes + fills with blood
* Right Atrium: Receives deoxygenated blood from the body via the
superior and inferior vena cava.
* Left Atrium: Receives oxygenated blood from the lungs via the pulmonary
veins.

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7
Q

What happens in ventricular diastole?

A
  • Passive Filling: Blood flows passively from the atria into the ventricles
    through the open atrioventricular (AV) valves (tricuspid valve on the right
    side and mitral valve on the left side).
  • Rapid Filling Phase: Initially, blood flows quickly due to the pressure
    difference between the atria and ventricles
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8
Q

What happens in ventricular systole of the isovolumetric contraction?

A
  • Contraction: The ventricles begin to contract, increasing the pressure
    within the chambers.
  • Valve Status: Both the atrioventricular (tricuspid and mitral) valves and
    the semilunar (aortic and pulmonary) valves are closed.
  • Pressure Buildup: As the ventricles contract, the pressure rises rapidly.
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9
Q

what happens in the transition to ejection phase?

A
  • Transition to Ejection Phase:
  • Pressure Surpasses: When the pressure in the ventricles exceeds the
    pressure in the aorta and pulmonary artery, the semilunar valves open.
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10
Q

What happens during ventricular ejection?

A
  • Semilunar Valves Open: With the increased pressure, the aortic and
    pulmonary valves open.
  • Blood Ejection: Blood is expelled from the ventricles into the aorta and
    pulmonary artery.
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11
Q

What happens during isovolumetric relaxation?

A
  • Ventricular Diastole:
  • Relaxation: The ventricles begin to relax after the ejection of blood.
  • Valve Status: Both the aortic and pulmonary valves close to prevent
    backflow of blood into the ventricles.
  • Pressure Changes:
  • Pressure Drop: As the ventricles relax, the pressure within them drops
    rapidly.
  • Closed Valves: The atrioventricular valves (tricuspid and mitral) remain
    closed during this phase, ensuring that the blood does not flow back into
    the atria.
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12
Q

What are the two AV valves?

A

*tricuspid valve
*mitral valves

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13
Q

What do the AV valves do during the ventricular filling and atrial contraction?

A
  • The AV valves are open, allowing blood to flow from the
    atria into the ventricles.
  • During atrial contraction, the atria push the remaining blood into the ventricles, ensuring they are fully filled.
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14
Q

What do the AV valves do during isovolumetric contraction?

A

The AV valves close as the ventricles begin to contract,
preventing backflow of blood into the atria

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15
Q

What do the AV valves do during isovolumetric relaxation?

A

The AV valves remain closed until the pressure in the
ventricles drops below the pressure in the atria, at which
point they open to allow ventricular filling

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16
Q

What makes up the semi-lunar valves?

A

*pulmonary + aortic valves

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17
Q

What do the semi-lunar valves do during isovolumetric contraction?

A

The semilunar valves remain closed as the pressure builds
in the ventricles

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18
Q

What do the SL valves do during ventricular ejection?

A

When the pressure in the ventricles exceeds the pressure in
the pulmonary artery and aorta, the semilunar valves open,
allowing blood to be ejected into these arteries

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19
Q

What do the SL valves do during isovolumetric relaxation?

A

The semilunar valves close as the ventricles relax,
preventing the backflow of blood from the arteries back
into the ventricles

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20
Q

How does atrial pressure differ in the cardiac cycle?

A
  • Increases during atrial systole.
  • Decreases during ventricular systole and remains low during ventricular
    filling
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21
Q

How does ventricular pressure differ during the cardiac cycle?

A
  • Low during diastole (filling phase).
  • Rapidly increases during isovolumetric contraction.
  • Peaks during ventricular ejection.
  • Rapidly decreases during isovolumetric relaxation
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22
Q

How does aortic pressure differ during the cardiac cycle?

A
  • High and stable during ventricular diastole.
  • Increases and peaks during ventricular ejection.
  • Briefly rises (dicrotic notch) during isovolumetric relaxation due to the
    closure of the aortic valve.
  • Gradually decreases during the rest of the diastole
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23
Q

Describe all the characteristics to dow with the S1 heartbeat sound

A

*Cause: Closure of the mitral and tricuspid valves.
*Timing: Occurs at the beginning of isovolumetric ventricular contraction.
*Characteristics:
* Splitting: Normally slightly split (~0.04 seconds) because the mitral valve
closes slightly before the tricuspid valve. This split is usually too short to
be heard with a stethoscope, so S1 is perceived as a single sound.

24
Q

Describe all the characteristics to do with the S2 heartbeat sound

A

*Cause: Closure of the aortic and pulmonic valves.
*Timing: Occurs at the beginning of isovolumetric ventricular relaxation.
*Characteristics:
* Splitting: Physiologically split because the aortic valve closes slightly
before the pulmonic valve.
* Variability: The duration of S2 splitting changes depending on respiration,
body posture, and certain pathological conditions. For instance, the split
widens during inspiration and narrows during expiration

25
Q

What are the characteristics of the sinoatrial node?

A
  • Intrinsic Electrical Activity: The SA node is electrically unstable
    and capable of spontaneous depolarisation.
  • Rate of Depolarisation: It spontaneously depolarises at a rate of
    90-100 times per minute.
  • Impulse Generation: The SA node generates electrical impulses
    that spread throughout the atria, initiating atrial contraction
26
Q

What are the characteristics of the Atrial ventricular node?

A
  • Intrinsic Electrical Activity: The AV node is also electrically unstable and
    capable of spontaneous depolarisation, but at a slower rate than the SA
    node.
  • Rate of Depolarisation: It spontaneously depolarises at a rate of 40-60
    times per minute.
  • Impulse Generation: The AV node generates and conducts electrical
    impulses to the ventricles, ensuring coordinated ventricular contraction.
27
Q

What is the function of the inter-nodal tracks?

A

Carry electrical impulses from the SA node to the AV node, ensuring
coordinated atrial depolarisation and contraction.

28
Q

What is the function of the fibrous midline?

A

Serves as an electrical insulator, preventing direct conduction between
atria and ventricles, ensuring the impulse passes through the AV node.

29
Q

What is the function and role in conduction of the bundle of his?

A

*Function: Collects electrical impulses from the AV node and carries them to
the higher and lower parts of the ventricles, including the apex
*Role in Conduction: Ensures coordinated contraction of the ventricles for
effective blood ejection

30
Q

What is the function and role of conduction of the purkinjae fibres

A

*Function: Conduct electrical impulses rapidly to the ventricular contractile myocytes.
*Role: Ensure coordinated and efficient ventricular contraction by
synchronising the depolarisation of ventricular muscle cells.

31
Q

What is the sympathetic stimulation effect on the SA node?

A
  • Increases Rate of Depolarisation: Sympathetic nerves release
    norepinephrine (noradrenaline), which binds to beta-1 adrenergic
    receptors in the SA node.
  • Mechanism: This increases the permeability of the SA node cells
    to calcium and sodium ions, accelerating the rate of spontaneous
    depolarisation.
  • Result: Increased heart rate (positive chronotropic effect)
32
Q

What is the effect on the SA node of parasympathetic stimulation?

A

Decreases Rate of Depolarisation: Parasympathetic nerves
release acetylcholine, which binds to muscarinic receptors in the
SA node.
* Mechanism: This increases the permeability of the SA node cells
to potassium ions while decreasing their permeability to calcium
and sodium ions, slowing the rate of spontaneous depolarisation.
* Result: Decreased heart rate (negative chronotropic effect).

33
Q

What is the effect of sympathetic stimulation on the AV node?

A
  • Increases Rate of Conduction: Sympathetic nerves release
    norepinephrine (noradrenaline), which binds to beta-1 adrenergic
    receptors in the AV node.
  • Mechanism: This increases the permeability of the AV node cells
    to calcium ions, enhancing the rate of conduction.
  • Result: Faster transmission of electrical impulses from the atria to
    the ventricles, leading to a decrease in the AV nodal delay and a
    quicker coordination of atrial and ventricular contractions.
34
Q

What is the effect of parasympathetic stimulus on AV node?

A
  • Decreases Rate of Conduction: Parasympathetic nerves release
    acetylcholine, which binds to muscarinic receptors in the AV node.
  • Mechanism: This increases the permeability of the AV node cells
    to potassium ions while decreasing their permeability to calcium
    ions, slowing the rate of conduction.
  • Result: Slower transmission of electrical impulses through the AV
    node, leading to an increase in the AV nodal delay and more
    regulated timing of atrial and ventricular contractions
35
Q

What are the two types of cardiac muscle cells?

A
  • Contractile Cells (99%): Responsible for the actual contraction and
    pumping action of the heart.
  • Autorhythmic Cells (1%): Specialised cells that generate and conduct
    electrical impulses, initiating and regulating the heartbeat
36
Q

What is the structure of cardiac muscle?

A

*striated muscle fibres
*nucleaus
*mitochondria
*T-TUBULES
*intercalated disks
*gap junctions
*desosomes

37
Q

What are the key properties of cardiac muscle?

A

*Autorhythmicity
*excitability
*conductivity
*contractility

38
Q

What is step 1/2 of the contraction mechanism?

A

*AP from adjacent cells excites myocytes and triggers membrane depolarisation in T-tubules

*Depolarisation causes voltage-gated
calcium channels to open, allowing calcium ions (Ca2+) to enter the cells
from the extracellular space

39
Q

What is step 3 of the contraction mechanism?

A

The influx of calcium ions binds to ryanodine receptors (RYR) on the sarcoplasmic reticulum (SR), inducing the release of additional calcium from the SR into the cytoplasm

40
Q

What is step 4 of the contraction mechanism?

A

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

41
Q

What is step 5 of the contraction mechanism?

A

Calcium unbound from troponin and
pumped back into SR

42
Q

What is step 6 of the contraction mechanism?

A

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

43
Q

What is step 7 of the contraction mechanism?

A

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

44
Q
A

*The P wave on an electrocardiogram (ECG) represents atrial depolarisation initiated
by the SA node.
*In sinus rhythm, P waves are consistent in shape and occur before each QRS
complex.

45
Q
A

*The PR interval is the time from the onset of the P wave to the start of the QRS
complex, representing the time taken for the electrical impulse to travel from the
atria to the ventricles.
*A normal PR interval ranges from 0.12 to 0.20 seconds.

46
Q
A

*The QRS complex represents ventricular depolarisation.
*In sinus rhythm, the QRS complexes are narrow (less than 0.12 seconds) and follow
each P wave.

47
Q
A

AS = 0.1 seconds
VS = 0.3 seconds
Diastole = 0.4 seconds

48
Q
A

At a normal resting heart rate of about 70 BPM, one cardiac cycle takes approximately 0.86 seconds

49
Q

What are the three sinus rhythm conditions?

A

*Sinus Bradycardia (<60BPM but PQRST regular and right order)

*Sinus Tachycardia (>100 BPM but PQRST regular and right order)

*Sinus Arrhythmia (Irregular BPM, PQRST rhythm and order)

50
Q

What is sinus bradycardia?

A
  • Sinus bradycardia is a slower-than-normal sinus rhythm with a heart rate
    of less than 60 beats per minute.
  • It can occur in well-trained athletes, during sleep, or as a result of
    medications or certain medical conditions.
51
Q

What is sinus tachycardia?

A

*Sinus tachycardia is a faster-than-normal sinus rhythm with a heart rate
greater than 100 beats per minute.
* It can occur due to exercise, stress, fever, or other conditions that
increase the body’s demand for oxygen

52
Q

What is sinus arrhythima?

A
  • Sinus arrhythmia is a normal variation in the sinus rhythm where the heart rate varies with the respiratory cycle.
  • It is most commonly seen in children and young adults and is considered a normal finding.
53
Q

How can sinus bradycardia be managed?

A
  • Beta-blockers or calcium channel blockers may be used if
    necessary
54
Q

What is the occurrence of sinus tachycardia?

A
  • Normal during exercise or stress.
  • Patients are usually asymptomatic.
  • May be associated with hypovolaemia or underlying medical
    problems.
55
Q

What are some associated diseases to sinus arrhythmia?

A

*Heart Block/Disease: Sinus arrhythmia can be associated with various forms of heart block or underlying heart disease.
*Respiratory Disease: It can also be associated with respiratory conditions, often influenced by changes in intrathoracic pressure during breathing

PMP101 - Health, Disease and Patient (20 decks)

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