On exposing palm wine to air for some days, it becomes sour owing to the conversion of

The nervous system coordinates body activities. Central nervous system (CNS): brain and spinal cord. Peripheral nervous system: nerves connecting CNS to rest of body.

Neurons transmit signals: sensory (from receptors to CNS), motor (from CNS to muscles/glands), relay (connect neurons). Signal travels as electrical impulse along neuron, chemical at synapse.

Reflex arc: stimulus → receptor → sensory neuron → relay neuron → motor neuron → effector → response. Reflexes are fast, automatic, protective. Brain involved in conscious decisions and complex processing.