Lec6: Fixed action patterns and central nervous system

TL;DR

Animal behaviors, like prey-catching and escape responses, are controlled by specialized neurons in the nervous system such as command neurons. Giant axons in some animals allow for extremely rapid conduction of action potentials.

Transcript

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Key Insights

• 👻 Animals have specialized neurons and sensory structures that allow them to detect and respond to specific stimuli in their environment.
• 😟 Nervous system adaptations, such as the presence of giant axons or the evolution of the myelin sheath, enable animals to transmit electrical signals quickly and efficiently.

Questions & Answers

Q: How do wandering spiders catch prey without a web?

Wandering spiders use sensory hairs on their legs to detect small movements and disturbances in the air caused by potential prey. This allows them to accurately locate and catch insects even without the use of a web.

Q: What is the advantage of having giant axons in animals like squid?

Giant axons allow for extremely rapid conduction of action potentials, which enables fast responses to stimuli. This is particularly useful for animals like squid that need to quickly react to their environment.

Q: What is a command neuron?

A command neuron is a neuron that, when stimulated, can elicit a whole sequence of movements or a specific behavior. In invertebrate animals, such as crayfish, these neurons can be identified and their activation can trigger escape responses or other behaviors.

Q: How does the myelin sheath affect the conduction of action potentials?

The myelin sheath insulates the axon and increases the capacitance of the membrane while decreasing the resistance. This allows for faster and more efficient conduction of action potentials by preventing loss of electrical charge along the axon.

Summary & Key Takeaways

• Some animals, like the wandering spider, use sensory hairs to detect prey movements in the air, while others, like toads, rely on giant neurons in their retinas to detect small moving stimuli.

• The nervous system of animals is specialized to elicit fixed-action patterns, such as prey-catching and escape responses, through the activation of specific neurons.

• The use of giant axons in animals like squid allows for rapid conduction of action potentials, while the evolution of the myelin sheath in vertebrates enables efficient transmission of electrical signals.