Lecture 3.2: The Heart as a Pump

Question 1

What is Negative Chronotropy?

Answer 1

A decreased rate of contraction

Question 2

What is Negative Inotropy

Answer 2

Decreased force of contraction

Question 3

What are Chronotropic Drugs?

Answer 3

• Drugs that may change the heart rate & rhythm
• Affect the electrical conduction system of the heart and the
nerves that influence it
• Such as by changing the rhythm produced by the sinoatrial node

Question 4

What is the structure of cardiac muscle cells (myocytes)? (7)

Answer 4

• Striated (less well organised than skeletal muscle cells)
• Small (diameter 20μm, length 100μm)
• Branched
• Single Nucleus (generally)
• Coupled to other myocytes
• Branching+coupling = functional syncytium
• Intercalated Disks

Question 5

What are Desmosomes? Why are they important?

Answer 5

They are intercellular junctions that provide strong adhesion between cells

Question 6

What are Fascia Adherens? Why are they important?

Answer 6

• Ribbon like structures that help stabilise
tissue
• A broad intercellular junction in the
intercalated disk of cardiac muscle anchoring
actin filaments

Question 7

What is the Mechanism of Heart Contraction (SA…etc)?

Answer 7

• Depolarisation of SA node spreads to atrial
myocytes
• Wave of depolarisation halted by fibrous
skeleton, insulates the atria from the ventricles
• Delay here allows atrial emptying
• Bridge across the fibrous skeleton, begins at
the AV node
• AP passes via Bundle of His into the right and
left bundle branches
• These deliver the AP to the Purkinje fibres
• Purkinje fibres deliver the AP to the contractile
myocytes of the ventricles

Question 8

What is Wiggers Diagram?

Answer 8

Wiggers diagram is a graphical representation of the cardiac cycle = the alternate contraction and relaxation of the heart

Question 9

What does the P wave represent?

Answer 9

Atrial Depolarisation

Question 10

What does the QRS wave represent?

Answer 10

Ventricular Depolarisation

Question 11

What does the T wave represent?

Answer 11

Ventricular Repolarisation

Question 12

Systole vs Diastole

Answer 12

• Systole occurs when the heart contracts to
pump blood out (ventricular contraction)
• Diastole occurs when the heart relaxes after
contraction (atrial contraction)

Question 13

What Valves open during Systole?

Answer 13

• Semilunar valves are open (aortic and
pulmonic)
• Atrioventricular valves are closed

Question 14

What Valves open during Diastole?

Answer 14

• Atrioventricular are open
• Aka Mitral and Tricuspid Valves

Question 15

Mitral Valve Open: Atrial vs Ventricular Pressure

Answer 15

(Ap > Vp)

Question 16

Aortic Valve Closed: Aortic vs Ventricular Pressure

Answer 16

(Aop > Vp)

Question 17

What is Diastasis?

Answer 17

Filling slows down

Question 18

What is meant by End Diastolic Volume (EDV)? In ml?

Answer 18

• It is the amount of blood that is in the ventricles
before the heart contracts
• About 120 mL

Question 19

Jugular veins openly communicate with RA therefore…?

Answer 19

… pressure changes in RA produce a visible JVP

Question 20

Atria and JVP Waves: A-Wave

Answer 20

• Caused by atrial systole
• Reflux of blood – minimal since incoming blood
has inertia

Question 21

Atria and JVP Waves: C-Wave

Answer 21

• Bulging of AV valves into atrium as they close • Jugular some distance from the AV valves,
therefore delay in seeing the wave

Question 22

Atria and JVP Waves: X-Wave

Answer 22

• Rapid drop in atrial pressure, caused by atrial
relaxation
• Base moves towards apex resulting in blood
being sucked into atria

Question 23

Atria and JVP Waves: V-Wave

Answer 23

• Increased atrial pressure as a consequence of
their filling

Question 24

Atria and JVP Waves: Y-Wave

Answer 24

• AV valves open, blood leaves ventricle, rapid
drop in atrial pressure

Question 25

Heart Sounds: S1

Answer 25

• Closure of AV valves in early systole, loudest
near apex of heart

Question 26

Heart Sounds: S2

Answer 26

• Closure of aortic and pulmonary valves
• Can sometimes be split during inspiration
producing A2 and P2 components

Question 27

Heart Sounds: S3 (occasionally heard)

Answer 27

• Heard in lean, young adults
• Blood rushing into relaxed ventricles

Question 28

Heart Sounds: S4 (basically never heard)

Answer 28

• Associated with atrial systole
• Therefore occurs before S1

Question 29

What are Abnormal Heart Sounds called?

Answer 29

Heart Murmurs

Question 30

What is Valvular Stenosis?

Answer 30

• Narrowing of valve opening
• Higher pressure gradient needed to move
blood through it

Question 31

What is Valvular Incompetence?

Answer 31

• Valve fails to seal correctly
• Resulting in regurgitation

Question 32

What are the 5 Factors Heart Murmurs are described by?

Answer 32

• Timing
• Intensity
• Pitch
• Location
• Response to Manoeuvres