The blue-ringed octopus (Hapalochlaena) produces a highly potent neurotoxin called tetrodotoxin (TTX) in its salivary glands.
The following information has been discovered about the effects of TTX on nerve cells:
Using the information provided, explain how TTX affects the electrical activity of neurones.
A common cause of death from TTX poisoning is respiratory failure as a result of paralysis of the diaphragm.
Explain how paralysis of the diaphragm could lead to respiratory failure.
TTX also affects cardiac muscle, preventing the generation of electrical signals that coordinate the heartbeat, leading to cardiac arrest in diastole (the relaxation phase of the cardiac cycle).
Suggest and explain what effect this would have on the ability of the heart to pump blood.
Some invertebrates have unmyelinated neurones with larger axon diameters to increase conduction velocity, unlike the myelinated neurones found in vertebrates.
Why is transmission of action potentials along the axon slower in the absence of saltatory conduction?
22 exam-style questions on OCR A A Level Biology Neuronal communication. Each one has a worked solution and a mark scheme showing where the marks go.