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DS1102 > Week 2 - Cardiovascular Physiology > Flashcards

Week 2 - Cardiovascular Physiology Flashcards

1
Q

What does functional syncytium mean

A

describes how cardiac chamber muscles contract as one

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2
Q

Describe cardiac muscle cells

A
  • contract via sliding filament mechanisms
  • cells are short, branched and interconnected
  • intercalated and contains gap junctions allowing the flow the ions between them - hence they transfer AP to all cells surrounding them allowing them to move as one unit
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3
Q

Explain Phase 0 of action potential in contraction cells

A

Phase 0 = Depolarization

Due to a stimulus (usually an action potential from a neighboring cell) the voltage gated sodium channels open, allowing a rapid influx of Na+ into the cell, causing a rapid depolarization.

The membrane potential rapidly rises from around -90mV to approx +20mV

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4
Q

Explain Phase 1 of action potential in contraction cells

A

Phase 1: Initial Repolarisation

Na+ channels close and K+ open causing a brief influx of K+ out of the cell.

This causes a slight repolarization dropping the membrane potential slightly

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5
Q

Explain phase 2 of action potential in contraction cells

A

Phase 2: Plateau

Ca+2 channel opens causing a movement of Ca+2 into the cell, however this is balanced by K+ channels and K+ leaving the cell

The membrane potential remains relatively stable. The influx Ca+2 is crucial for the contraction of cardiac muscle.

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6
Q

Explain phase 3 in action potential in contraction cells

A

Phase 3 : Rapid repolarization

Ca+2 channels close and more K+ channels open allowing a significant efflux of K+

The membrane potential rapidly returns to the resting level

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7
Q

Explain phase 4 in action potential in contraction cells

A

Phase 4: Resting Membrane Potential

The cell returns to its resting state maintained primarily by the Na+/K+ ATPase pump, which pumps Na+ out and K+ into the cell, and the K+ channels that allow K+ to leak out.

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8
Q

What are SA Nodes

A

The heart’s natural pacemaker
It generates electrical impulses at regular intervals.
These impulses initiate the heart beat by causing the atria to contract

a node made up of specialised cells h is where AP are continuously generated

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9
Q

Describe the sequence of nodes passing electric signals through the heart

A
  1. SA mode

SA node generates impulses

  1. AV node

the impulses pause (0.1s) at the AV node

  1. AV bundle (Bundle of His)

the AV node bundle connects the atria to the ventricles

  1. Bundle branches

The bundle branches conduct the impulses through the interventricular septum

  1. Endocardial network (purkinje fibres)

The subendocardial conducting network depolarizes the contractile cells of both ventricles

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10
Q

What’s the function of the Atrioventricular (AV) Node

A

Briefly delays the electric signal before allowing it to pass into the ventricles (approx 0.1s) to ensure that the atria have enough time to fully contract and empty their blood into the ventricles before the ventricles contract

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11
Q

What is the function of the bundle of His (AV bundle)

A

The pathway that carries the electrical impulses from the AV node down into the ventricles.
This is the only electrical connection between the atria and ventricles

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12
Q

What is the function of the bundle branches

A

There divided into 2 branches within the interventricular septum (one for each ventricle)
the right bundle branch directs the electrical impulses to the right ventricle
Left bundle branch directs them to the left ventricle
These branches conduct the impulses rapidly to ensure the coordinated contraction of both ventricles.

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13
Q

What is the function of the purkinje fibers (endocardial network)

A

Located - spread throughout the inner walls of the ventricles, extending from the end of the bundle branches
Function - distribute the electrical impulses across the ventricles causing them to contract simultaneously from bottom up

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14
Q
A

SA Node

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15
Q
A

AV Node

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16
Q
A

Endocardial network (purkinje fibres)

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17
Q

Explain the formation of action potential in pacemaker cells

A
  • doesn’t have a sable resting membrane potential because of Na+ leak channels are always having ions into the cell (always open)
  1. Pacemaker potential

This slow depolarization is due to both opening of Na+ channels and closing of K+ channels.

  1. Depolarization

The action potential begins when the pacemaker potential reaches a threshold voltage. Depolarization is due to Ca+2 influx through Ca2+ channels

  1. Repolarization

Repolarization due to Ca+2 channels inactivating and K+ cannels opening allowing flow of K+ into the cell which brings the membrane potential back to its most negative voltage.

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18
Q

What are differences between pacemaker cell action potentials and other APs

A
  • In Pacemaker action potential depolarisation is caused by Ca+2 rather than Na+ influx
  • There is no resting membrane potential
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19
Q

What are ECGs

A

Electrocardiograms
An electrocardiogram is a graphical representation of the electrical currents of the heart. This graph can show the depolarization and repolarization of cardiac muscle.

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20
Q

What is the normal sequence of a EGC divided into

A
  • P wave
  • QRS complex - (more ventricle muscle causes the signal to be bigger than P wave)

Q Wave - Initial negative deflection
R Wave - Positive deflection following the Q wave
S Wave - Negative deflection following the R wave

  • T wave
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21
Q

What does the P wave represent

A

atrial depolarisation

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22
Q

What does the QRS complex represent

A

depolarization of ventricles (more ventricle muscle hence causes this signal to be bigger than P wave)

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23
Q

What occurs in the ST segment

A

ventricles depolarising

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24
Q

What does T wave represent

A

Ventricular repolarization

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25
Q

What are the intervals and segments of an ECG

A

P-R Interval
- Atrial excitation to ventricular excitation
- Can be P-Q intival

S-T segment
- Vebtricular myocardium is depolarised

Q-T Interval
- Ventricular depolarisation to ventricular repolarisation

R-R interval
- Ventricular cycle
- Used for heart rate

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26
Q

What is cardiac Output

A

= how much blood is pumped into the aorta in 1 minute

= Quantity of blood that flows through the circulation

= stroke volume x heart rate

= venous return = how much blood returns (since the amount of blood that leaves the heart is the same as the amount of blood that enters)

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27
Q

What does cardiac output depend on

A

how many heart beats and how hard the heart contracts

  • How many times the heart beats
  • how much blood is in the ventricles
  • how much pressure is developed in the ventricles
  • how much pressure there is in the arteries
28
Q

What is stroke volume

A

Stroke volume = volume of blood pumped out of one ventricle with each beat

Stroke volume = the end diastolic volume (EDV) MINUS the end systolic volume (ESV of the ventricle

EDV - ESV = Stroke volume

29
Q

What is venous return

A

quantity of blood flowing from veins into the right atrium each minute - this is the most important factor in determining stroke volume

30
Q

What is preload - Frank-starling law of the heart

A

States that the more blood pumped into the heart then the more the heart muscle is stretched.

More stretch = stronger contraction = more blood ejected

31
Q

What is sympathetic stimulation

A

part of the autonomic nervous system responsible for the body’s “fight or flight response

32
Q

What is sympathetic impulses in the heart

A

These impulses influence the hearts function by increasing heart rate and the force of the heart’s contractions. This hence enhances cardiac output to meet the body’s increased demands during stress or physical activity.

33
Q

What is parasympathetic stimulation

A

the actions of the parasympathetic nervous system (PNS) a part of the autonomic nervous system responsible for promoting “rest and digest” functions in the body. This system helps conserve energy and maintain normal bodily functions during restful periods.

These signals are controled by the vagus

34
Q

What is parasympathetic impulses in the heart

A

In the heart parasympathetic impulses help regulate heart function, particularly by slowing the heart rate and reducing the force of heart contractions.

35
Q

What is blood pressure

A

the force blood applies on blood vessels

36
Q

What is diastolic pressure

A

the lower of the 2 numbers in a blood pressure reading reading and represents the pressure in the arteries when the heart is at rest between beats. It also represents the resistance of the small arteries and the condition of the arterial walls.

37
Q

What is systolic Pressure

A

the higher of the 2 numbers in a blood pressure reading and represents the pressure in the arteries when the heart contracts and pumps blood into the body.

Systolic pressure indicates the maximum pressure exerted on the artery walls when the heart contracts. It reflects the force with which the heart is pumping blood and the condition of the arteries.

38
Q

What is pulse pressure

A

Difference between systolic and diastolic pressure

39
Q

What measures changes of blood pressure in the body

A

baroreceptors

40
Q

What do the baroreceptors mainly provide feedback to

A
  • Cardioacceleratory
  • cardioinhibitory
  • vasomotor centres
41
Q

What is the bodies response to low blood pressure

A
  1. Stimulus - low blood pressure
  2. Baroreceptos are inhibited
  3. Impulses from baroreceptors activate cardioacceleratory center and situlate vasomotor center
  4. a) Sympathetic impulses to heart increase, heart rate increase, contractility increase, CO increase
    b) Vasomotor fibers stimulate vasoconstriction causing resistance to increase - diameter of blood vessels decrease
  5. increase in CO and resistance returns blood pressure to homeostatic range
42
Q

What is the bodies response to high blood pressure

A
  1. Stimulus - blood pressure increases
  2. Baroreceptors are stimulated
  3. Increases impulses from baroreceptors stimulate cardioinhibitory center
  4. a) Decrease in sympathetic impulses to heart causing decrease in heart rate, contractility and CO
    b) decrease in rate of vasomotor impulses allows vasodilation (increase in blood vessel diameter) causing resistance to decrease
  5. Decrease in CO and resistance returns blood pressure to homeostatic range
43
Q

Which blood pressure is higher, systolic or diastolic

A

systolic

44
Q

What is pulse pressure and mean arterial pressure

A

Pulse pressure = systolic - diastolic
Mean pressure = diastolic + pulse pressure / 3

45
Q

To increase flow how must pressure and resistance change

A
  • increase pressure
  • decrease resistance
46
Q

To increase pressure how mut resistance and flow change

A
  • flow in must increase
    or
  • resistance must increase
47
Q

What is the most important factor controlling blood flow

A

blood vessel diameter

48
Q

What are the steps in the cardiac cycle

A

Phase 1 - Passive ventricular filling
Phase 2 - Atrial Contraction
Phase 3 - Isovolumetric ventricular contraction
Phase 4 - Ventricular ejection
Phase 5 - Isovolumetric ventricular relaxation

49
Q

What occurs in phase 1 - passive ventricular filling - in the cardiac cycle

A
  • The heart is filling with blood
  • AV valve is open
  • Where pulmonary vein pressure is the highest
  • Neither the atrium or ventricle are contracting
  • Blood volume rises to about 80% capacity
  • Pressure in the heart increases slowly
  • Blood pressure is dropping in the aorta as it loses blood
  • atria pressure is lower than pulmonary vein but higher than ventricle
50
Q

What occurs in phase 2 - atrial contraction - of the cardiac cycle

A
  • Atria contract putting additional blood into the ventricles
  • Where the P wave occurs
  • Initial atria depolarisation causes contraction - decreasing atria volume - increase pressure - causing blood to flow from the atria into the ventricle
  • Atrial pressure is higher than ventricle pressure
  • Aorta pressure continues to decrease as blood continues to go into the other parts of the body
51
Q

What occurs in phase 3 - isovolumetric ventricular contraction - of the cardiac cycle

A
  • ventricles start to contract causing the AV valve to shut producing a sound which is heard as the first sound in the heart beat
  • heart muscle contracts causing volume of the ventricles to decrease - increasing pressure - however the aorta pressure is still higher hence there is no movement of blood
  • pulmonary vein pressure is lower than atria
  • atria pressure is lower than ventricle
  • ventricle pressure is rising and is higher than atria but lower than aorta
  • Aorta pressure is high but decreasing
52
Q

What occurs in phase 4 - ventricular ejection of the cardiac cycle

A
  • Ventricle pressure increases and become higher than aorta and atria pressure causing ventricles to contract and pump blood into the aorta
  • Pulmonary vein pressure is lower than atria
  • atria pressure is lower than ventricle
  • Ventricular pressure is higher than atria and aorta
  • aorta pressure is increasing but lower than ventricle
53
Q

What occurs in phase 5 - isovolumetric ventricular relaxation - of the cardiac cycle

A
  • Semilunar valve closes (making a second sound)
  • Ventricle starts to relax however there is a bit of time between the relaxation and then the AV value opening - hence no movement of blood in this phase
  • The phase ends when the AV valve opens again
  • Pulmonary vein pressure is lower than atria
  • atria pressure is lower than ventricle
  • ventricular pressure is decrease but is higher than atria and lower than aorta
  • aorta pressure is higher than ventricle
54
Q

what is end diastolic volume

A

the amount of volume which fills the heart

55
Q

what is end systolic volume

A

the small amount of blood left over in the heart after contraction

56
Q

what is the equation for stroke volume

A

end diastolic volume - end systolic volume

57
Q

What is afterload

A

the pressure that the left ventricle needs to work against to pump blood into the aorta and through the systemic circulation

58
Q

What are the 3 layers which form the wall of a blood vessel

A
  • Tunica intima (innermost layer)
  • Tunica Media (middle layer)
  • Tunica externa (outer most layer)
59
Q

Which branch of the autonomic nervous system innervates blood vessels

A

Sympathetic nervous system

60
Q

Which layer of the blood vessel wall does the sympathetic nervous system innervate

A

tunica media (middle layer)

61
Q

What are the effectors which the sympathetic nervous system create

A

norepinephrine (noradrenaline) and to a lesser extent epinephrine (adrenaline)

62
Q

where are baroreceptors found

A
  • carotid sinus (at the bifurcation of the common carotid arteries)
  • aortic arch
63
Q

What factor does the kidney influence to maintain blood pressure

A
  • blood volume - as the kidney’s control the amount of fluid excreted or retained
64
Q

What happens to the blood pressure when you rise from lying down to a standing position

A

gravity causes blood to pool in the lower extremities, which can lead to a temporary decrease in blood pressure

65
Q

Why is there a constant and low blood pressure in the capillaries.

A

allows for effective and efficient diffusion of gases into the blood, without the risk of pressure induced damage.

66
Q
A

DS1102 (30 decks)

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