Lesson 2 of 11 · 6 min
Neural system in animals
NCERT §18.1
A Hydra has no brain at all, yet it still pulls in its tentacles when touched. A cockroach has a small brain. Meher has a brain and a spinal cord. The building block is the same in all three.
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In short
In all animals the neural system is made of neurons, highly specialised cells that can detect, receive and transmit different kinds of stimuli.
Lower invertebrates have a very simple arrangement: in Hydra the neural system is a network of neurons.
Insects have a better organised system, with a brain, a number of ganglia and neural tissues.
Vertebrates have a still more developed neural system.