Date | November 2020 | Marks available | 4 | Reference code | 20N.2.SL.tz0.4 |
Level | Standard Level | Paper | Paper 2 | Time zone | time zone 0 |
Command term | Describe | Question number | 4 | Adapted from | N/A |
Question
State the function of platelets in response to a skin cut.
Describe the pathway of the electrical impulse during excitation of the heart muscle.
Markscheme
platelets help form a clot / scab at the site of the cut;
pacemaker/SA node fires initiate electrical impulse;
impulse travels across the atria walls;
impulse arrives at the AV node <base of the right atrium>;
impulse passes from the AV node down to the bundle of His <through the septum>;
passes down the <left and right> bundle branches <to the apex of the heart>;
travels up through the Purkinje fibres <to stimulate the rest of the ventricles>;
Accept an annotated diagram.
Responses must be in chronological order to be credited, not just a list.
Examiners report
Generally answered correctly.
Generally answered correctly to obtain at least 2 or 3 marks.