W2 CVS Refresher

Question 1

Where do carotid arteries take blood?

Answer 1

Takes blood to upper part of body, face and head.

Question 2

What is the process of blood flow? (2)

Answer 2

1. Atrial Kick
   atria contract
   ventricles contract
   heart squeezes out all blood
2. Cardiac twist

Lub Dub
lub- SLV opens
dub- semi-lunar valve closes

Question 3

Haemodynamic cycle:
What is systole and diastole?
What are the stages of the cardiac cycle?

Answer 3

Heart contraction & Relaxation

Ventricular filling
Atrial contraction
Isovolumetric contraction phase
Ventricular ejection phase
Isovolumetric relaxation

Question 4

Heart (Electrical flow):
What are the components? (6)

Answer 4

SAN
AVN
Fibrous midline- no electrical conductivity
Inter-nodal tracks
Bundle of His
Purkinje fibres

Question 5

What does the cardiac muscle consist of?
(%)

What happens as Gap Junctions and Desmosomes

Answer 5

99%- contractile; 1% Autorhythmic cells

• Striated type, branched muscle fibres (myofibrils) contain a single nucleus, many mitochondria and T-tubules
• Connected by intercalated disks
  Gap junctions=Depolarisation between cells
  Desmosomes=Hold fibres together during contraction

Question 6

What is the function of the Bundle of His?

Answer 6

Bundle of HIS (AV bundle)
-Collect and carry to higher and lower part of the ventricles (Apex); 20-40 times/min

Question 7

What is the function of the Purkinje fibres?

Answer 7

Specialised myocardium for electrical
conduction (not contraction) towards
contractile myocytes (cardiac cells)
(they stimulate ventricles to contract)

Question 8

What is the role of an artificial pacemaker?

Answer 8

Stimulates electrical impulses

Question 9

What are the components involved in the process of electrical flow? (6)

Answer 9

1. SA node
2. AV node
3. Collecting duct
4. Bundle of His
5. Purkinje fibres

Question 10

What are the key properties of cardiac muscle? (4)

Answer 10

1. Auto-rhythmicity:
   Ability to initiate heartbeat, consistent and continuous at a regular pace without any external stimuli
2. Excitability:
   Ability to respond to stimuli of adequate strength and duration (threshold or more)
   Ability to generate and process action potential
3. Conductivity:
   Ability to conduct and transmit impulse through the cardiac tissue
4. Contractility:
   Ability to contract in response to stimulation (mechanical)

Question 11

What are the steps in Excitation- Contraction Coupling in Contractile Myocytes?

Answer 11

Depolarisation at L type channel, calcium enters
L-type calcium channel (voltage gated)
Acts on Ca2+ in sarcoplasmic reticulum (Calcium sparking) to release further calcium
Calcium binds to troponin (actin-myosin complex)

1. AP from adjacent cell excites myocytes and trigger membrane depolarisation in T-tubules.
2. Calcium enter the cells via voltage gated
   ion channel, opens and calcium enters the cells
3. Calcium binds to Ryanodine receptor (RYR) and induces further Calcium release from SR
4. Calcium binds to troponin and triggers actino-myosin complex and contraction
5. Calcium unbind from troponin and pumped back into SR
6. Calcium unbinding cause relaxation and excess Ca2+ exchanged with Na+
7. Na+ gradient is maintained by sodium-potassium- ATPase pump

Question 12

Sinus rhythms (ECG/EKG)
what are the meanings of P QRS T?

Answer 12

P- Atrial contraction
QRS- Ventricular depolarisation
T- Ventricular repolarisation

Question 13

How long is a cardiac cycle?

Answer 13

0.8secs
so 75 BPM is normal
HR= 60/0.8 = 75 bpm average

Question 14

What is the normal heart rate?

Answer 14

60-100= Average
<60 = Sinus Bradychardia
>100 BPM Sinus Tachycardia