The Heart

Question 1

Where is the precise location of the heart?

Answer 1

The thoracic cavity - in the mediastinum (space between lungs). Apex is 9 cm to the left of the midline at the level of the 5th intercostal space.

Question 2

What are the 3 layers of tissue that comprise the heart wall?

Answer 2

Pericardium (has a fluid gap within it)
Myocardium (largest)
Endocardium (innermost tissue)

Question 3

How is the pericardium divided?

Answer 3

Outer sac is the fibrous pericardium.

Inner sac is the serous pericardium.

Question 4

What are the properties of the fibrous pericardium?

Answer 4

Is continuous with the tunica adventitia of the great blood vessels above and it is inelastic, which prevents over distension of the heart.

Question 5

How is the serous pericardium subdivided?

Answer 5

Outer layer: parietal pericardium (borders fibrous pericardium).

Inner layer: visceral pericardium (adherent to the heart muscle).

Question 6

What is produced in the serous membrane?

Answer 6

Flattened epithelial cells secrete serous fluid, (pericardial fluid) into the space between the visceral and parietal layers. This allows smooth movement when the heart beats.

Question 7

Name the factors affecting heart rate

Answer 7

Gender
Autonomic activity
Age
Hormones
Exercise
Temperature
Baroreceptor reflex
Emotional State

Question 8

State the Cardiac Cycle (simplified)

Answer 8

SA node triggers
Atrial depolarization
AV node introduces delay of 0.1 seconds
AV node triggers
Down bundle of his into left and right branches
Purkinjie fibres
Ventricle Depolarization
Complete cardiac diastole (0.4 seconds)

Question 9

What is the lub sound from a heart caused by?

Answer 9

Closure of the AV valves (biscupid and mitral)

Question 10

What is the dup sound from a heart caused by?

Answer 10

Closure of the Semi-Lunar valves (Aortic and Pulmonary)

Question 11

What does the ECG show?

Answer 11

The Electrocardiogram shows the spread of electrical activity generated by the SA node as it travels through the atria, and the AV node as it travels to ventricles.

Question 12

What are the 5 waves of an ECG called?

Answer 12

P,Q,R,S and T

Question 13

Explain the P Wave

Answer 13

The 1st wave on the ECG, medium in size - it represents when impulse from SA node sweeps over atria (atrial depolarization)

Question 14

Explain the QRS complex

Answer 14

Represents the rapid spread of the impulse from the AV node down the septum to the purkinjie fibres causing ventricular depolarization.

Question 15

Explain the T Wave

Answer 15

Represents the relaxation of the ventricular muscle.

Question 16

What is cardiac output?

Answer 16

The amount of blood ejected from each ventricle every minute

Question 17

What is stroke volume?

Answer 17

The volume of blood ejected from each ventricle per contraction

Question 18

What is the equation for Cardiac Output?

Answer 18

Stroke Volume * Heart rate

Question 19

What is the healthy stroke volume at rest?

Answer 19

70ml

Question 20

What is an increase in cardiac output (for e.g during exercise) called?

Answer 20

cardiac reserve

Question 21

What is the volume of blood in a ventricle before contraction called?

Answer 21

VEDV: Ventricular end diastolic volume

also known as preload.

Question 22

What is the equation for blood pressure?

Answer 22

Cardiac Output * Peripheral Resistance

Question 23

Explain the properties and function of the myocardium.

Answer 23

Myocardium is the middle layer of the 3 layers of the heart. It is composed of specialized striated muscle, which is not under voluntary control. These muscles are arranged into fibres, (with nuclei) which branch off. The joints at where different branches meet are called intercalated discs and appear as thick dark lines. These joints ensure a separate nerve supply is not needed.

Question 24

What is secreted in the walls of the atria?

Answer 24

ANP (atrial natriuretic peptide) is secreted by specialized muscle cells in the walls of the atria.

Question 25

What supports the myocardium?

Answer 25

The Fibrous Skeleton of the heart.

Question 26

What is the endocardium?

Answer 26

A layer that lines the chambers and valves of the heart. It is a smooth membrane, and consists of flattened epithelial cells, and is continuous with the endothelial lining the blood vessels.

Question 27

How many cusps do the right and left AV valves have?

Answer 27

The right (tricuspid) valve has 3 cusps, and the left (mitral) valve has 2 cusps.

Question 28

What are cordae tendinae?

Answer 28

Strong cords which stop the valves opening the wrong way. They are supported by papillary muscles.

Question 29

How is the heart supplied with blood?

Answer 29

Left and right coronary arteries which branch from the aorta. They recieve about 5% of the blood pumped from the heart.

Question 30

How is the heart’s blood supply drained?

Answer 30

Venous drainage, venous blood is collected into a number of cardiac veins which later join the cornary sinus which opens into the right atrium.

Question 31

What is the name of the ability of the heart to generate it’s own electrical impulses called?

Answer 31

autorythmicity

Question 32

Name some hormones that can affect heart rate

Answer 32

Thyroxine and epinephrine (adrenaline)

Question 33

Which nerve supplies the SA and Av nodes and atrial muscle?

Answer 33

The vagus nerve (parasympathetic)