Cerebral hemisphereOne of two long smooth bodies, narrow in front and wider behind. A deep groove runs between the two.
Optic lobeOne of two large round bodies in front of the cerebellum. Together they are the widest part of the brain.
CerebellumA narrow band across the brain, just behind the optic lobes. In the frog it is very small.
Medulla oblongataThe hind part of the brain, a widening of the spinal cord. Several pairs of cranial nerves leave its sides.
Olfactory lobeThe front end of the brain, fused with its partner. The nerves of smell begin here.
Olfactory nerveThe first cranial nerve. It runs forward from the olfactory lobe to the nose.
DiencephalonThe part between the hemispheres and the optic lobes. It is also called the thalamencephalon.
Pineal bodyA small outgrowth on the roof of the diencephalon. It is also called the epiphysis.
Fourth ventricleA three-cornered hollow on top of the medulla. Its thin roof carries a web of blood vessels, the choroid plexus.
Spinal cordThe cord that runs back from the brain inside the backbone.
From below 5
Optic nerveThe nerve of sight, from the eye. All of its fibers cross to the other side of the brain.
Optic chiasmThe place where the two optic nerves cross. It lies under the diencephalon.
InfundibulumA flat two-lobed swelling just behind the optic chiasm.
Pituitary bodyA small body behind the infundibulum and partly covered by it. It is also called the hypophysis.
Cranial nervesNerves that leave the brain itself; a frog has ten pairs. Most of them leave from the sides of the medulla.
How this list was compiled: Every name checked on 2026-10-01 in two sources. S. J. Holmes, The Biology of the Frog (1906, public domain), the brain, https://archive.org/details/biologyoffrog01holm. A. Ecker, The Anatomy of the Frog, English edition by G. Haslam (1889, public domain), the brain: general description, https://archive.org/details/anatomyoffrog00ecke. R. W. Hegner, College Zoology (1912, public domain), the brain of the frog, https://archive.org/details/collegezoology00hegn. Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work
How it works
A frog brain labeled in two views, front end to the left. From above it shows the parts in order from the nose to the spinal cord. From below it shows where the optic nerves cross. It is a plan, not to scale.
Read the full guide
From above
Start at the left. The olfactory nerves lead into the olfactory lobes, then come the two cerebral hemispheres. The diencephalon, with the pineal body on it, lies between them and the optic lobes, the widest part of the brain. The cerebellum is only a narrow band. Behind it the medulla oblongata, with the fourth ventricle open on top, tapers into the spinal cord.
From below
Switch to Below. The optic nerves cross at the optic chiasm. Just behind it are the infundibulum and the pituitary body. The roots of the cranial nerves leave the sides of the medulla. Press Quiz me to name each part yourself.
In most animals with backbones the cerebellum is large. In the frog it is only a narrow fold.
Questions and answers
What are the parts of a frog's brain?
From front to back: the olfactory lobes, two cerebral hemispheres, the diencephalon, two optic lobes, the cerebellum and the medulla oblongata, which runs into the spinal cord.
How big is the cerebellum of a frog?
Very small. It is only a narrow fold across the brain, just behind the optic lobes. In most other animals with backbones it is a large part of the brain.
How many cranial nerves does a frog have?
Ten pairs. The first, the olfactory nerves, run to the nose, and the second, the optic nerves, run to the eyes. Several of the others leave from the sides of the medulla oblongata.
Where is the optic chiasm on a frog brain?
On the underside, below the diencephalon. It is the place where the two optic nerves cross. In the frog all of the fibers cross to the other side.