Applicable for A-Level, IB, DSE, AP-Level Exams

Biological Molecules    Cell Structure    Cell Transport    Immunology    Exchange    Mass Transport    DNA, Genes & Protein Synthesis    Genetic Diversity    Biodiversity    Photosynthesis    Respiration    Energy & Ecosystems    Stimuli and Response    Nervous Coordination & Muscles    Homeostasis    Inheritance    Populations & Evolution    Ecosystems    Gene Expression    Recombinant DNA Technology   

Survival and Response

Animals and plants respond to stimuli for survival. In plants, IAA act as a plant growth factor and promotes growth in the shoots and inhibits growth in the roots. This causes phototropism and gravitropism as an effect.

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Receptors are responsible to convert stimuli into action potentials. The Panician Corpuscle is an example of a pressure receptor within your skin to detect touch. As pressure is applied, it deforms the membrane with stretch-mediated sodium ion channels. This causes more Na+ ions to enter the sensory neurone, causing a generator potential which will cause an action potential if a threshold voltage is reached.

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Control of Heart Rate

The heart is myogenic and contracts by itself. When the baroreceptors detect there is a low blood pressure in the carotid arteries, impulses are sent to the medulla oblongata. More impulses are sent along the sympathetic nerve to the SAN. The SAN spreads a wave of electrical activity which causes atrial systole. The atria is allowed the fill before ventricles contract. This is because electrical impulses are sent to the AVN, down the Bundle of His and Purkyne Fibres. This causes ventricular systole from the bottom up.

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