Anatomy&Physiology

Question 0

3 layers of the heart

Answer 0

Endocardium
Myocardium
Epicardium

Question 1

Define:
Pulmonary circulation
Systemic circulation

Answer 1

P- Carries blood b/w the heart and the lungs

S - carries blood b/w the heart and the rest of the body

Question 2

One way blood flow of the heart is ensured by…

Answer 2

The coordinated action of the four heart valves: atrioventricular (mitral and tricuspid) and semilunar (pulmonary and aortic) valves.

Question 3

SA node

Answer 3

Commonly referred to as the pacemaker of the heart.
Has a innate Rhythm, spontaneously discharged an electrical signal every .8-.9secs, generated a heart rate of ~70 bpm.
Also subject to hormonal control with adrenalin increasing HR as well as force of contraction

Question 4

AV node

Answer 4

Acts as an electrical connection b/w the atria and the ventricles.
Located at the base of the right atrium, transmits impulses from the atria to the ventricles but only after a short delay (~0.1secs) to ensure all the blood has been pumped from the atria b4 the ventricles contract.

Question 5

P-wave

Answer 5

Represents atrial depolarisation

Question 6

The PR interval

Answer 6

Represents conduction through the AV node and the bundle of his.

Question 7

The QRS complex

Answer 7

Represents depolarisation on the ventricles.

Question 8

The T-wave

Answer 8

Represents repolarisation of the ventricles.

Question 9

Describe how the autonomic nervous system affect the heart

Answer 9

Parasympathetic - vagus nerve, reduces HR

Sympathetic - accelerator nerve, increases HR and can also increase the force with which the atria ventricles contract.

Question 10

Describe AF

Answer 10

Most common arrhythmia. Normal control of heart rhythm by the SA node is disrupted leading to rapid and irregular electrical signals that cause atrial quiver. Reduces efficiency of blood being pumped into the ventricles.

Question 11

Consequences of AF

Answer 11

Pooling of blood-> blood clots (thrombus) on the wall of the atria.
Dislodge - embolism
Stroke
Pulmonary embolism
Fluid retention - peripheral and pulmonary oedema.

Question 12

Heart rhythm in AF

Answer 12

Rapid and irregular atrial activity - 350-600bpm, causing atrial quiver rather then contract.
AV node contracts irregular and rapid - 120-189bpm.
Reduced cardiac efficiency.

Question 13

Pathogenesis of AF

Answer 13

Atrial fibrosis is the formation of excess fibrous connective tissue in the walls of the atria.
A.fibrosis and AF go hand in hand
Fibrosis can extend to the SA and AV nodes.
Fibrotic tissue does not conduct electrical signals

Question 14

Caused of atrial fibrosis

Answer 14

Hypertension
Congestive heart failure
Valvular disease

Question 15

What is the blood made up of.

Answer 15

Erythrocytes - RBCs 45%
Leukocytes - WBCs and platelets <1%
Plasma - 55%

Question 16

Haemostasis

Answer 16

Circulatory systems ability to prevent blood loss from a damaged vessel.

Question 17

Primary Harmostasis

Answer 17

Occurs in seconds
Stimulated by exposed collagen
Bought on by activation, aggregation and adhesion of platelets to form a platelet plug

Question 18

Secondary haemostasis

Answer 18

When damage to the endothelium exposes tissue factor (layer beneath collagen).
Activation of coagulation cascade and the production of thrombin, which converts fibrinogen into fibrin to reinforce the platelet plug

Question 19

What system breaks down fibrin

Answer 19

Fibrinolytic system

Question 20

Goal of coagulation

Answer 20

To transform liquid blood into a solid thrombus

Question 21

A thrombus consists of…

Answer 21

Fibrin strands

Blood cells

Question 22

Four phases of coagulation?

Answer 22

Stimulus- exposed collagen and tissue factor
Initiation - platelet activation : platelet plug. Thrombin amplifies
Amplification phase - large scale production of thrombin; positive feedback
Thrombin formation - conversion of fibrinogen to fibrin to form a fibrin clot

Fibrin network together with activated platelets and RBCs forms an insoluble clot.

Question 23

Role of thrombin in haemostasis

Answer 23

• Central player in thrombus formation
• Most potent stimulus for platelet activation
• amplifies coagulation through positive feedback
• responsible for converting fibrinogen to fibrin

Question 24

What blocks fee and clot bound thrombin?

Answer 24

Dabigatran (pradaxa) is an oral direct thrombin inhibitor.

Question 25

2 probable mechanisms for halting the coagulation cascade …

Answer 25

Generation of anti-thrombin - factor IXa and Xa and

Activation of the fibrinolytic system