NS - CVS II

Question 1

What model to Cardiomyocytes follow for muscle contraction?

Answer 1

Sliding filament model

Question 2

What 3 subunits are present in Troponin?

Answer 2

1. Troponin T (TnT)- ties troponin to actin and tropomyosin
2. Troponin I (TnI)- inhibits ATPase in actin-myosin interaction
3. Troponin C (TnC)- binds calcium ions to tropomyosin to activate contraction

Question 3

What are the structures of actin and myosin?

Answer 3

Actin
* Thin filaments consisting of alpha helix strands

Myosin
* 4 light chains and 2 heavy chains with globular heads sites for ATP and actin binding

Question 4

What law describes the relationship between the length of the sarcomere and the force of contraction?

Answer 4

Frank Starling Law

Question 5

What does it mean that the cardiac muscle is myogenic?

Answer 5

Activity is drawn from the muscle- not the nerve

Question 6

What is the role of gap junctions in the heart?

Answer 6

Impulse conduction
* Have inherent pacemaker activity

Question 7

What is fibrillation?

Answer 7

Irregular unsynchronized contraction of muscle fibres

Question 8

What is the order of contraction and relaxation in the heart? (5)

Answer 8

1. Atrial Contraction
2. Atrial Relaxation
3. Ventricular Relaxation
4. Ventricular Contraction
5. Ventricular Relaxation

Question 9

How is the regulation of the heart beat achieved? (4)

Answer 9

1. Electrical and physical separation of the atrial and ventricular chambers
2. Pacemaker cells set the frequency
3. Conducting cells give a coordinated beat
4. Strength of the beat is controlled

Question 10

What is the natural pacemaker of the heart?

Answer 10

Sino-atrial node (SAN)

Question 11

What spreads the coordinated AP to the atrial muscle?

Answer 11

Internodal pathways and Bachmanns bundle

Bundle of His –> Purkinje fibres

Question 12

What is an Electrocardiogram (ECG)?

Answer 12

A diagnostic test that records the electrical activity of the heart

Question 13

How would maximal and minimal readings be shown in regards to lead placement?

Answer 13

Maximal- Leads parallel to the current flow

Minimal- Leads perpendicular to the current flow

Question 14

What causes the P,Q,R,S,T waves?

Answer 14

P- Atrial depolarisation
Q- Interventricular wall depolarisation
R- Inner ventricular wall depolarises
S- Outer ventricular wall depolarise
T- Repolarisation of ventricles