Control of the heartbeat and cardiac outputEdexcel A-Level Biology A: Flashcards

What these 14 flashcards ask

What does myogenic mean?
Where is the sinoatrial node and what does it do?
Why does non-conducting fibrous tissue lie between the atria and ventricles?
What is the purpose of the AVN delay (about 0.1 s)?
What are the roles of the bundle of His and Purkyne fibres?
What does the P wave of an ECG represent?
What do the QRS complex and T wave represent?
How is heart rate calculated from an ECG?
Define tachycardia and bradycardia.
What is cardiac output and how is it calculated?
Which nerves change heart rate and how?
Where are chemoreceptors that detect CO₂ and pH changes found?
How is minute ventilation calculated?
Why is soda lime used in a spirometer?

Exam questions on Control of the heartbeat and cardiac output

A researcher removes the heart from an anaesthetised frog and places it in oxygenated saline solution at room temperature. All nerves to the heart have been cut. The isolated heart continues to beat rhythmically for several hours.
Explain why the isolated heart continues to beat after its nerves have been cut, naming the structure that sets its rhythm.2 marks
A 55-year-old man attends a cardiology clinic complaining of a fluttering sensation in his chest. A technician attaches electrodes to his chest and records an electrocardiogram (ECG) while he rests. The trace shows a normal sequence of P wave, QRS complex and T wave, with a constant interval of 0.50 s between the R peaks of successive heartbeats.
Another patient's ECG shows no regular P waves, QRS complexes or T waves, only rapid, irregular, disorganised electrical activity. Deduce what this indicates about the ventricles and explain why this is a medical emergency.2 marks
A student volunteers for a spirometer investigation. She breathes from a closed spirometer chamber containing soda lime, which absorbs carbon dioxide, and a pen recorder traces the volume of gas in the chamber. At rest her tidal volume is 0.50 dm³ and her breathing rate is 14 breaths per minute. After five minutes of cycling these values are 2.0 dm³ and 28 breaths per minute. The trace shows her oxygen consumption rising from 0.30 dm³ min⁻¹ at rest to 2.4 dm³ min⁻¹ during cycling.
Calculate the student's minute ventilation at rest and during cycling, and state how many times greater it was during cycling.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).