2. The heart

Question 1

How heavy is the heart?

Answer 1

250 - 350 grams

Question 2

Where is the heart located?

Answer 2

2/3 offset left of the midline of the sternum

Question 3

Where is the heart within?

Answer 3

The mediastinum

Question 4

What encloses the heart?

Answer 4

The pericardium

Question 5

What is a function of the pericardium?

Answer 5

Attaches heart to surrounding tissues

Question 6

What is the pericardium?

Answer 6

A tough double layered membranous sac

Question 7

What are the two layers of the pericardium and where are they present?

Answer 7

1. Visceral layer (attached to heart surface)

2. Parietal layer (outer pericardial layer)

Question 8

What is the function of the lubricating fluid between pericardial layers?

Answer 8

Reduces friction during movement of heart with contraction

Question 9

Left circuit

Answer 9

Systemic circuit

Question 10

Right circuit

Answer 10

Pulmonary circuit

Question 11

Why are there no valves between the atria and veins?

Answer 11

As back flow isn’t a significant problem here

Question 12

Describe the fibrous skeleton of the valves

Answer 12

Four interconnecting rings of dense connective tissue of the heart surround and support the four heart valves

Question 13

What happens when pressure is greater behind the valve?

Answer 13

It opens

Question 14

What happens when there is greater pressure in front of the valve?

Answer 14

It closes

Question 15

Where does the heart receive most of its blood supply?

Answer 15

Through the coronary circulation during diastole

Question 16

Why is coronary blood flow adjusted?

Answer 16

In response to changes in the heart’s O2 requirements.

Question 17

What are cardiac muscles connected by?

Answer 17

Intercalated discs.

Question 18

Cardiac muscle automaticity:

Answer 18

The heart contracts rhythmically as a result of action potentials that it generates by itself

Question 19

What makes up 99% of cardiac cells?

Answer 19

Contractile cells

Question 20

What is the function of autorhythmic cells?

Answer 20

Initiate and conduct the action potentials responsible for contraction of working cells

Question 21

What are the specialised pacemaker areas?

Answer 21

‒ Sinoatrial node (SA node)
‒ Atrioventricular node (AV node)
‒ Bundle of His
‒ Purkinje fibres

Question 22

What is the rate of cardiac muscle controlled by and what does it control?

Answer 22

ANS:
‒ Sympathetic & parasympathetic
‒ Control of rate & contractile strength

Question 23

Central output to: (nervous system)

Answer 23

• Parasympathetic NS (vagus nerve)
• Sympathetic NS via rostral ventrolateral medulla
• Sympathetic chain

Question 24

x 7 properties of an effective heart

Answer 24

• Regular contractions at appropriate rate for metabolism
• Guaranteed time for ventricular filling after atrial & ventricular contractions
• Contraction duration long enough for physical movement of fluid
• Contractile strength sufficient to generate appropriate pressures
• Ventricular pressure directed towards exit valves
• Coordination of left & right, and atrial & ventricular contractions
• Matched volumes of emptying & filling

Question 25

What is cardiac adaptation in physical training dependent on?

Answer 25

Types, duration and intensity of training.

Question 26

What does isotonic stress (eg cycling) lead to?

Answer 26

Volume load and chamber dilation

Question 27

What does isometric stress (eg weightlifting) lead to?

Answer 27

Pressure load and chamber hypertrophy

Question 28

Heart muscle hypertrophy diagram

Answer 28