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Physiology 1 > Cardiac Cycle > Flashcards

Cardiac Cycle Flashcards

1
Q

Where do the vaina drain into

A

These veins drain into the

inferior vena cava that drains into the right atrium.

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2
Q

Describe flow of blood from right atrium to left ventricle - brief

A

From the right atrium, the blood flows into the
right ventricle. The right ventricle then contracts in systole and the blood leaves the heart through
the pulmonary artery that goes to the lungs. At the lungs, the blood is oxygenated then moves back
to the heart via the pulmonary vein and drains into the left atrium.
The blood then moves down into
the left ventricle that contracts to send the blood around the body via the aorta leaving the heart.

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3
Q

Role of arteries and veins

A

The heart is the driving force of this cycle. The arteries distribute the blood the heart pumps and the
veins act as a reservoir of blood.

The capillaries are the site of exchange.

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4
Q

What regulates the heart

A

The heart is regulated by a pacemaker known as the sinoatrial node (SA node). This is a group of cells
located in the wall of the right atrium that has the ability to spontaneously produce an action
potential that travels through the heart via electrical conduction systems.

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5
Q

What influences the rate of heart regulation

A 
The rate this action 
potential is produced is influenced by nerves that supply it. Part of the potential moves down the 
atrioventricular node (AV node) that electrically connects the right atrium with the right ventricle.
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6
Q

Where does the av node send its electrical current to

A

The AV node then sends the action potential into the right ventricle via Bundles of His

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7
Q

Why does the sa node have a different resting potential than other cells

A

The SA node
has a different resting potential and electrical activity compared to other cells. This is because when
a cell of the SA node reaches its resting potential of -50 or -60 mV, it is unstable and sodium ion
channels called IF channels are triggered that allows sodium into the cell causing slow depolarisation
of the cell.

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8
Q

What happens when sa node reaches -40mv

A

When this depolarisation reaches a level of around -40mV, voltage gated calcium channels(no voltage gated sodium channels) are triggered to open causing calcium influx and rapid
depolarisation (inside is now more positive than the
outside).

  1. The next stage is that the calcium channels are
    then closed and voltage gated potassium channels are
    opened causing potassium to leave the cell.
  2. The result of this is repolarisation until it reaches its negative -60mV
    threshold that triggers the funny current.
  3. The cycle thenrepeats (see the cycle on the right).
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9
Q

What does the action potential do to the cardiac muscle

A

This action potential then spreads to the cardiac muscle causing them to depolarise.

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10
Q

Why is the san important for the cardiac cells

A

These muscle
cells do not have a funny current but are in fact stimulated to contract by depolarisation from the
SAN. This stimulates the opening of voltage gated sodium channels in the muscle cell that causes
depolarisation.

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11
Q

How does depolarisation occur

A

Voltage gated calcium channels open very slowly after the initial depolarisation,
meaning there is some repolarisation caused by the sodium/potassium ATPase (calcium influx not
fast enough yet). The calcium influx causes some calcium induced calcium release (still not enough
calcium). The sodium channels are at this stage beginning to close contributing to this initial
repolarisation.

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12
Q

What does opening of channels prevent

A

However, the opening of the calcium channels fully prevents the repolarisation from
taking full affect. This causes a plateau phase that is a balance between potassium channels that now
open, and calcium channels as well as some contribution from chloride
channels.

However, when the calcium channels shut and the potassium
channels open fully, there is rapid repolarisation such that there is in fact some
hyperpolarisation.

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13
Q

What is the role of atpase pump

A

The ATPase pump then restores the ion concentrations in the
refractory period before the cell is ready for stimulus by the SAN.

This cycle of
conduction passes across the heart in stages (see right) that is delayed between
the atria and ventricles.

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14
Q

How is the electrical activity of the heart represented

A

The electrical activity of the heart can be represented by an electrocardiogram
(also ECG and see right)

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15
Q

What does the p part signify

A

The P signifies when the atria depolarise and contract.

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16
Q

What does the p r segment show

A

The segment from P

to R is caused by the delay the AVN causes between the atria and ventricles.

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17
Q

What is the QRs complex

A

The QRS complex is the

8ventricular depolarisation and contraction, with the atria repolarising simultaneously.

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18
Q

What is the phase between s and t

A

The phase
between S and T is the time when the ventricles are contracting and therefore emptying with the T
wave signifying ventricular repolarisation.

19
Q

What happens in the TP interval

A

The TP interval is the period when the ventricles relax and

fill with blood.

20
Q

Where does blood enter the heart

A

Blood enters the heart through the superior or inferior vena cava emptying into the right atrium.

21
Q

Describe the flow of blood in the right side of the heart - right atrium tooooo left ventricle

A
  1. The right atrium then fills with passage to the right ventricle blocked by a one way valve called the tricuspid valve (has other names).
  2. The blood flows into the right ventricle through this valve and
    collects there due to a second valve between the right ventricle and the pulmonary artery being closed.
  3. This valve is known as the pulmonary valve. The pressure in the right ventricle will eventually open however before this, the right atrium contracts to force more blood into the right ventricle
    causing it to stretch.
  4. The tricuspid valve then shuts with the right atrium relaxing and then right ventricle contracts.
  5. This increases the pressure on the pulmonary valve forcing blood into the pulmonary artery.
  6. This blood then travels to the lungs for oxygenation and then returns to the heart via pulmonary veins (2 of them) to empty into the left atrium.
  7. This blood then passes through into the left ventricle via the mitral
    valve.
  8. This increases the pressure in the left ventricle causing it to fill up with the blood prevented from leaving by the aortic valve.
  9. The left atrium then contracts to empty more blood into the left ventricle causing it to stretch.
  10. The mitral valve then shuts and the left ventricle then
    contracts forcing blood through the aortic valve into the
    aorta to be carried around the body.
  11. The blood leaves at a very high pressure.
22
Q

What is the right ventricle , left ventricle pressure value at systole

A

The in the right ventricle is 25/5 mmHg during systole and diastole respectively. The pressure in the left
ventricle is 120/80 mmHg during systole and diastole respectively.

23
Q

When is there a rise in pressure in the ventricles - what is the name

A

There is a phase during the cardiac cycle when the ventricles are contracting however neither the
aortic nor pulmonary valves open. This causes a rise in pressure in the ventricles as the tricuspid and
mitral valves are unidirectional. This phase is known as isovolumetric contraction (pressure without
change in volume).

24
Q

What happens to the ventricles when the left atrium contracts

A

The pressure in the left ventricle varies over time. When the left atrium contacts, the pressure in the
left ventricle rises slightly. This stimulates the mitral valve to close and the left ventricle contracts
during isovolumetric contraction causing a sharp rise in pressure.

25
Q

What Happens when the pressure in the left ventricle is greater than the aorta

A

When the pressure in the left
ventricle is greater than that in the aorta, the aortic valve opens and blood is ejected. The ventricle
then empties until the pressure in the aorta is greater than that in the left ventricle and this causes
the aortic valve to slam shut.

26
Q

When happens after isovokumetric relaxation

A

The pressure then continues to drop in isovolumetric relaxation until it
is below the pressure in the left atrium which causes the mitral valve to open. The cycle then
restarts.

27
Q

Compare the volume of atria and ventricles during each phase

A

The left ventricular volume also changes over a heartbeat. Initially during ventricular diastole, the
volume is quite high as the ventricle is relaxed.

28
Q

When do atria reach maximum isovolumetric contraction

A

During atrial systole, the volume increases further
and remains at its maximum level during isovolumetric contraction (around 120 ml) before it decreases sharply when the aortic valve opens.

The ejection is very rapid to begin with but slows
down towards the end of ventricular systole.

29
Q

When is left ventricular volume at its lowest

A

Left ventricular volume is at its lowest during
isovolumetric relaxation (around 40 ml). The volume then increases again when the mitral valve
opens and blood empties at a rapid rate at first that slows as the ventricle fills. The cycle then
repeats.

30
Q

How can stroke volume be calculated

A

Stroke volume can be calculated by subtracting the end diastolic volume (EDV) of the left
ventricle by the end systolic volume (ESV) (EDV – ESV).

31
Q

What can be illustrated on a pressure volume loop graph

A

The ventricular pressure and volume can be considered on one graph
(see right) called the ventricular pressure-volume loop. This graph
becomes a different shape when the heart is working abnormally.

32
Q

What is the area inside the loop of the graph equivalent to

A

The area inside the loop is equal to the work done by the heart.

33
Q

What happens during heart failure

A

During heart failure, the heart is working hard but not pumping very much which means the heart needs more oxygen to enable it to meet body demands. This spirals out of control eventually causing heart attack.

34
Q

Role of jugular vein

A

The jugular vein drains from the head
straight into superior vena cava into the
right atrium.

35
Q

Why is the pressure in the jugular vein equal to the vena cava

A

There is no valve between the vena cava and the right
atrium meaning the pressure of the right atrium is the same in the
jugular vein.

36
Q

What can be a sign of heart failure

A

In some heart failures, the pressure of the heart is
distorted which affects the jugular vein causing it to bulge.

The
pressure of the right hand side of the heart can be viewed on the left.

37
Q

What does the A wave represent

A

The A wave is when the atrium contracts and blood moves into the
right ventricle out of the atrium. The pressure in the atrium then
drops as it empties and then refills during the X phase.

38
Q

What causes v wave and y wave

A

When the atrium is full and tense and the

tricuspid valve is closed, this is the V wave and the opening of the tricuspid valve is the Y descent.

39
Q

How can pressure changes in the heart be measured

A

These pressure changes can be measured using the jugular vein.
The heart can have 4 possible different sounds.

40
Q

What is responsible for lub sound / s1

A

The sound made by the closure of the tricuspid and

mitral valves are known as S1 or ‘lub’.

41
Q

What is s2 sound produced

A

The sound made by the closure of the pulmonary and aortic
valves are known as S2 or ‘dub’. The opening of these valves do not really make a sound. These are
the two main sounds of the heart.

42
Q

What is the s3 sound

A

S3 is a sound associated with turbulent blood flow into ventricles.
It is associated with the end of the first third of diastole and is detected especially in older people.

43
Q

What is the s4 sound

A

S4 is a sound associated with forceful atrial contraction caused by the ventricle not expanding very well
due to it being stiff. This is also a sound that is associated with older people as well.

Physiology 1 (67 decks)

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