Frog Nervous System

The frog's nervous system, like that of other vertebrates, is organised around a central nervous system — the brain and spinal cord — connected to the rest of the body by a peripheral system of cranial and spinal nerves. The brain lies protected within the bony cranium and, though small compared with that of a mammal, is clearly divisible into the same three primary regions recognisable across the vertebrates: the forebrain, midbrain and hindbrain.

The forebrain is the most anterior region and is itself made up of several parts. A pair of olfactory lobes at the very front receive input from the olfactory (smell) receptors in the nasal cavity. Behind them lie the paired cerebral hemispheres, which in the frog are relatively small and are concerned mainly with integrating incoming sensory information rather than with the extensive higher-order processing seen in mammals. Behind the cerebral hemispheres lies the diencephalon, a narrow central region bearing the pineal body (a light-sensitive structure sometimes called the 'third eye') above and connected below to the pituitary gland, the master endocrine gland that regulates many of the frog's other hormone-secreting organs.

The midbrain in the frog is dominated by a conspicuous pair of rounded optic lobes, which — unlike in mammals, where vision is processed mainly in the cerebral cortex — serve as the frog's principal centre for processing visual information and for general sensory-motor coordination, reflecting how important vision is to a frog's predatory strike and its escape from predators.

The hindbrain consists of two parts. The cerebellum, a small transverse fold lying just behind the optic lobes, is concerned with coordinating muscular movement and maintaining balance and posture, particularly important for a frog that alternates between swimming and jumping. The medulla oblongata, the most posterior part of the brain, controls a number of vital involuntary functions and passes without a sharp boundary into the spinal cord, which runs the length of the frog's short vertebral column, protected within the neural canal of the vertebrae. …