17. Blood Vessels + The Cardiac Cycle

Question 1

What are the structural differences of arteries and veins?

Answer 1

Arteries have thick elastic tunica media while veins have approx equal media and external.
Veins have valves

Question 2

Which vessels are known as resistance vessels?

Answer 2

Arterioles

Question 3

What are the two types of venules?

Answer 3

Post capillary (smallest, very porous) and muscular (no exchange, thicker walls)

Question 4

How is cardiac output defined?

Answer 4

Strove volume x Heart rate

Volume of blood ejected by one ventricle in 1 minute

Question 5

What are the important rules of the cardiac cycle?

Answer 5

Atria contract, followed by ventricles with 0.1 s delay
L and R ventricles eject the same amount of blood
Each beat takes ~0.85s

Question 6

What is the purpose of the annulus fibrosis?

Answer 6

It is an electrical insulator to prevent the passage of electric signal from the atria to the ventricles - must travel through bundle branches in heart walls

Question 7

What does the PQRST wave represent?

Answer 7

P wave - atrial depolarisation
QRS complex - ventricular depolarisation (begins at apex) and atrial reploarisation
T wave - ventricular repolarisation

Question 8

How long is each stage of the cardiac cycle?

Answer 8

Ventricular filling - 0.5s
Isovolumetric contraction - 0.05s
Ejection - 0.3s
Isovolumetric relaxation - 0.08s

Question 9

What is the typical end diastolic volume?

Answer 9

120 mL

Question 10

What causes the closing of the AV valves?

Answer 10

When the pressure of the ventricles exceeds the pressure of the atria

Question 11

How is stroke volume calculated?

Answer 11

2/3 of EDV, amount of blood ejected in one beat. 120*0.66=70-80 mL

Question 12

In which stage do the semilunar valves open?

Answer 12

Ejection, allow blood into pulmonary circuit and aorta

Question 13

What is the sinoatrial node?

Answer 13

A collection of my oysters that spontaneously depolarise at regular intervals. The pacemaker of the heart

Question 14

What is responsible for a nervous change in heart rate?

Answer 14

The rate at which the myocytes depolarise.
Sympathetic NS - increase HR
PS NS - decrease HR

Question 15

What is responsible for setting the basal heart rate?

Answer 15

The vagus nerve. Allows PS innervation of myocytes, causing decreased rate of depolarisation

Question 16

How does the sympathetic NS affect the heart?

Where do these fibres originate?

Answer 16

Originate from T1-T5 spinal nerves
Increase AV conduction velocity
Decrease myocyte AP length 
Increase rate of relaxation
Increase contractile force