Cardiovascular

Question 1

Position of the heart=

Answer 1

.Sits in the centre-left of the chest cavity, behind the sternum.
.The lungs sit on either side and the diaphragm at the base.

Question 2

The layers of the heart=

Answer 2

1)EPICARDIUM=outer layer. The connective tissue between pericardium and rest of the heart.
2)MYOCARDIUM=middle layer. Cardiac myocytes
( striated, mononucleated and rich in mitochondria).
3)ENDOCARDIUM=inner layer. Similar to endothelium and to the inner layer of blood vessels.

Question 3

The pericardium=

Answer 3

A protective sac surrounding the heart.
Structure=
.Fibrous(outermost layer) attached to the blood vessels and the diaphragm.
.Serous(parietal and visceral layer or epicardium).
.Pericardial cavity(the space in-between) filled with pericardial fluid -ultraclean plasma (40-50 mL) and acts as a lubricant.

Question 4

Cardiac myocytes=

Answer 4

.branched
.striated-lines visible through cells and indicate the sarcomere edges
.mononucleated-rich in mitochondria.

Question 5

Chambers and valves=

Answer 5

4 Cardiac chambers= left atrium, right atrium, left ventricle and right ventricle.
4 Valves(made of fibrous tissue)= Tricuspid atrioventricular valve, mitral atrioventricular valve, pulmonary semi-lunar valve(leads to pulmonary artery) and aortic semi-lunar valve(leads to aorta)

Question 6

Sinoatrial (SA) node=

Answer 6

Depolarising pacemaker
Located in the right atrium
Responsible for atrial contraction

Question 7

Atrioventricular (AV) node=

Answer 7

In the right posterior portion of the inner atrial septum.
Oversees ventricular contraction.

Question 8

Electrical activity in the heart=

Answer 8

1)Action potential begins at SA node (pacemaker and in Right atrium.
2)Propagates via gap junctions.
3)AV node delays signal
4)Bundle of His branching to apex.
5)Purkinje fibres conduct signal to all of ventricular myocardium.

Question 9

Electrocardiogram-Basic pattern of electrical activity in the heart=

Answer 9

1)P wave=atria depolarisation (Contraction)
2)QRS interval= Ventricular depolarisation(Contraction)
& Atrial repolarisation (Relaxation)
3)Q wave – Septal depolarisation
4)R wave – Depolarisation of the majority of ventricular mass
5)S wave – Depolarisation of the Purkinje fibres
6)T wave- Ventricular repolarisation (Relaxation)
7)U wave- Late
repolarisation (of Purkinje fibres and some ventricular myocytes).

Question 10

Cardiac Excitation

Answer 10

Heart is innervated by cardio-excitatory sympathetic and
cardio-inhibitory parasympathetic nerve fibres.
Increased Heart Rate
Faster depolarisation and reduced repolarisation.
Decreased Heart Rate
Reduced depolarisation and hyperpolarisation.