Cardiac Cycle and Output

Question 1

What are the 5 Stages of the Cardiac Cycle?

Answer 1

1. Ventricular Filling
2. Atrial Contraction
3. Isometric Ventricular Contraction (Systole)
4. Ventricular Ejection
5. Isometric Ventricular Relaxation

Question 2

During Ventricular Filling, to What Percentage does the ventricle Fill To?

Answer 2

80%

Question 3

During Ventricular Filling, does the Pressure Within The Ventricle have to be Greater Or Lesser than the Pressure Within The Atrium

Answer 3

Lesser

Question 4

During Atrial Contraction, what Percentage of the Ventricular Volume is Pumped Into The Ventricle?

Answer 4

The remaining 20% left over from ventricular filling

Question 5

Atrial Contraction is Triggered by…

Answer 5

SA node firing

Question 6

During Isovolumetric Ventricular Contraction, what happens to the Bicuspid/Mitral and Tricuspid valves?

Answer 6

They are pushed closed

Question 7

During Isovolumetric Ventricular Contraction, will the semilunar valves open?

Answer 7

No, because the pressure within the ventricle is still rising to the same level as arterial pressure

Question 8

During Isovolumetric Ventricular Contraction, are any Valves open?

Answer 8

No

Question 9

During Ventricular Ejection, does the Ventricle still keep contracting?

Answer 9

Yes

Question 10

During Ventricular Ejection, does the Pressure Within The Ventricle have to be Greater Or Lesser than the Arterial Pressure?

Answer 10

Greater

Question 11

During Isovolumetric Ventricular Relaxation, does blood Enter The Ventricle?

Answer 11

No

Question 12

What is the Formula for Cardiac Output?

Answer 12

CO = Heart Rate (How Fast) x Stroke Volume (How Much Blood)

Question 13

What is a Normal Cardiac Output at Rest?

Answer 13

4-7 Litres per Minute

Question 14

What is the Average Resting Stroke Volume?

Answer 14

70ml

Question 15

What is the Formula for Cardiac Reserve?

Answer 15

Cardiac Reserve = CO_Max - CO_Rest

Question 16

What 3 Factors regulate Stroke Volume?

Answer 16

Preload, Contractility and Afterload

Question 17

What is Preload?

Answer 17

The Stretch on the heart before it contracts

Question 18

What is Contractility?

Answer 18

The forcefulness of contraction in the heart

Question 19

What is Afterload?

Answer 19

The pressure that the ventricle has to work against during ventricular ejection (arterial pressure)

Question 20

What is the Frank-Starling Law Of The Heart?

Answer 20

The more blood goes in, the more blood goes out

Question 21

What is an example of a Positive Inotrophic Agent?

Answer 21

Ca²⁺ Ions

Question 22

What is an example of a Negative Inotrophic Agent?

Answer 22

K⁺ ions

Question 23

When does the First Heart Sound Occur?

Answer 23

During isometric ventricullar contraction (Systole) as the blood experiences turbulence against the closed Mitral/Bicuspid and Tricuspid valves

Question 24

When does the Second Heart Sound Occur?

Answer 24

During isometric ventricular relaxation as the blood experiences turbulence against the closed pulmonary and aortic valves

Question 25

What causes **Depolarisation** in a **Ventricular Contractile Fibre** during an **Action Potential**?

Answer 25

Rapid opening of voltage-gated fast Na⁺ channels causing rapid influx of Na⁺

Question 26

What causes the **Plateu** in a **Cardiac Action Potential**?

Answer 26

The influx of Ca²⁺ as slow voltage-gated Ca²⁺ channels open and the outflux of K⁺ as some K⁺ open

Question 27

What causes **Repolarisation** in a **Ventricular Contractile Fibre** during an **Action Potential**?

Answer 27

The closing of Ca²⁺ channels and the K⁺ outflow when more voltage-gated K⁺ channels open

Question 28

What does an **ECG** measure?

Answer 28

The sum of all the electrical activity in the heart

Question 29

What does the **P Wave** indicate?

Answer 29

Atrial depolarisation

Question 30

What is the **QRS Complex**?

Answer 30

Onset of ventricular depolarisation

Question 31

What is the **T Wave**?

Answer 31

Ventricular repolarisation

Question 32

What inputs into the **Cardiovascular Centre** in the **Medulla**?

Answer 32

Higher Brain Centres (Cerebral Cortex, Limbic System, Hypothalamus) Proprioreceptors (Monitoring joint movement) Baroreceptors (Monitoring Blood Pressure) Chemoreceptors (Monitoring Blood Acidity, CO₂ and O₂)

Question 33

**Vagus Nerves** are **Sympathetic** or **Parasympathetic**? What do they do to the **Heart**?

Answer 33

Parasympathetic, Decreases heart rate

Question 34

Is the **Vagus Nerve** always **Active**?

Answer 34

Yes, just to different degrees depending on demand

Question 35

**Cardiac Accelerator Nerves** are **Sympathetic** or **Parasympathetic**? What do they do to the **Heart**?

Answer 35

Sympathetic, Increases heart rate and contractility

Question 36

**Vasomotor Nerves** are **Sympathetic** or **Parasympathetic**? What do they do to **Blood Vessels**?

Answer 36

Sympathetic, Cause vasoconstriction

Question 37

On the **Heart**, **Parasympathetic** **Nerves** use what **Neurotransmitter**?

Answer 37

Acetylcholine

Question 38

On the **Heart**, **Sympathetic Nerves** use what **Neurotransmitter**?

Answer 38

Noradrenaline/Norepinephrine

Question 39

How do **Baroreceptor****s**measure**Blood Pressure**?

Answer 39

By measuring stretch in the blood vessels

Question 40

Where are **Baroreceptors** found?

Answer 40

In the carotid sinus and the arch of the aorta. Cardiopulmonary Baroreceptors found in the major veins of the heart and in the lungs