Question 17N.3.HL.TZ0.22
| Date | November 2017 | Marks available | [Maximum mark: 6] | Reference code | 17N.3.HL.TZ0.22 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Describe, Identify, State | Question number | 22 | Adapted from | N/A |
The micrograph shows a section of cardiac muscle.
[Source: Musculocardiaco by Goyitrina (https://commons.wikimedia.org/wiki/File:Musculocardiaco.jpg)]
Identify the structure labelled X.
[1]
intercalated disc
Describe the unique properties of cardiac muscle cells.
[4]
a. cells are myogenic/self-excitatory
b. cells are joined end to end
OR
cells are joined by intercalated disc
c. «intercalated discs» allow for faster propagation «of signal»
d. cells contract together for coordinated contraction
e. contain many mitochondria
f. cells are branching/Y-shaped
g. controlled by pacemaker/sinoatrial/SA and atrioventricular/AV nodes
[Max 4 Marks]
State an early invention that led to improved knowledge of the heart.
[1]
stethoscope
OR
electrocardiograph/ECG
Allow other valid example.