Top answers

What are the roles of the sinoatrial node (SAN) and the atrio-ventricular node (AVN)?

The heart muscle is myogenic and initiates a heartbeat through an electrical conduction system; both the sinoatrial node and atrio-ventricular node are essential in this mechanism. The sinoatrial node (SAN) ...
SP
Answered by Shelby P. • Biology tutor
50635 Views

What events occur during the cardiac cycle?

Within the heart the atria contract creating a high pressure and squeezing blood into the ventricles. The semi lunar valves are closed so pressure within the ventricles builds up.Pressure within the ventricl...
JH
Answered by James H. • Biology tutor
11858 Views

Describe how negative feedback is used to control blood glucose concentration (6 marks)

Throughout your answer to this question make sure that you are cramming as much key language into it as possible! Phrases like 'islets of Langerhans', 'beta/alpha cells', and 'transporter proteins' will all ...
MH
Answered by Matt H. • Biology tutor
21146 Views

How does a deletion of a base in the DNA base sequence lead to a mutated protein?

It is important to note that bases on the DNA (and mRNA) are read in separate sets of 3s along a DNA/(mRNA) stand (this is called a triplet code in DNA, or the codon in mRNA). So, if a base is deleted, the w...
FS
Answered by Febi S. • Biology tutor
17610 Views

What are the events in the cardiac cycle?

The cardiac cycle is the series of events that leads to blood being pumped to the lungs and around the body. The cycle begins with the SAN (sino-atrial node). This is the hearts 'pacemaker'. It sends out a n...
TC
Answered by Thomas C. • Biology tutor
9206 Views