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Describe the electrical conduction system of the heart and how it initiates the heart beat

The sinoatrial node (SAN) is the pacemaker of the heart and initiates a wave of excitation (impulse) at a regular interval. This wave of excitation sweeps across the walls of the atria and in doing so causes...
JM
Answered by James M. • Biology tutor
11701 Views

How does the volume in the lungs change as we breathe?

As humans breathe in, the ribcage moves upwards and outwards. As this happens, the diaphragm flattens and moves down. This allows air to move into the lungs causing an increase in volume within the lungs. Th...
RW
Answered by Rebecca W. • Biology tutor
3650 Views

Why is the model of the structure of biological membranes described as ‘fluid mosaic’?

The biological membrane is a complex, heterogenous structure, built by two lipid layers with proteins and molecules immersed and in it. Its properties were developed due to the fact that its main function is...
MS
Answered by Martyna S. • Biology tutor
4430 Views

What are the four chambers of the heart and what do they do?

The four chambers are called the right atrium, the left atrium, the right ventricle and the left ventricle. Deoxygenated blood enters the right atrium and is pumped into the right ventricle. The blood is the...
HM
Answered by Hannah M. • Biology tutor
8910 Views

How to do a genetic cross to work out the offspring phenotype probabilites?

Construct a punnet square, putting the gametes of one parent in the first vertical column and the other parent in the first horizontal column. Next carry out the cross by combining the gametes in the squares...
GR
Answered by Georgia R. • Biology tutor
5192 Views