Comparison of Brain in Various Vertebrates

Learn about the comparison of brain in various vertebrates.

Comparison: Vertebrates # Elasmobranch:

1. The brain is enclosed within a cartilaginous cranium. It is divisible into a forebrain, made up of telencephalon and thalamencephalon; a midbrain or mesencephalon and a hindbrain consists of metencephalon and myelencephalon. The various lobes of the brain are situated in a straight line.

2. Olfactory lobes – The two olfactory lobes are large and anteriorly connected with the cerebral hemispheres by a stalk-like olfactory peduncle. It is concerned with the sense of small. The nasal sacs are large. Evidently, the olfactory sense is highly developed. The corpus striatum is bulging.

3. Cerebral hemisphere – It is undivided and without any median groove. The cerebral hemisphere is thickened both in the floor and in the roof. It is the seat of memory, intelligence and consciousness.

4. Thalamencephalon – It is posterior to the fore brain. On the nonnervous vascular roof is a small rounded pineal body representing the third ancestral eye. The floor bears the infundibulum with a pituitary body. The pituitary body is glandular and secretes different hormones of varied functions.

The two sides of the infundibulum bear two thin walled oval sacs, the lobi-inferiores, which are produced posteriorly into sacci vasculosi. It is believed to act as pressure receptor. An optic chiasma is present in front of the infundibulum.

5. Mesencephalon – It is very large, bears a pair of oval optic lobes dorsally and longitudinal nerve fibres like crura cerebri of higher animals ventrally. The optic lobes control vision.

6. Metencephalon – It consists of a very large dorsal cerebellum. It overlaps the potic lobes in front and medulla oblongata behind. It is the centre for coordination of muscular movement and partly for balance also.

7. Myelence phalon – It is also known as medull oblongata. It gradually tapers behind to end in the spinal cord. Anteriorly, It is produced into ear-shaped lappets, the corpora restiforma.

8. The brain is hollow and bears several intercommunicated cavities of unequal dimensions. Cerebrospinal fluid circulates through these cavities or ventricles and the spinal cord. The cavities in the cerebral hemispheres are called first and second ventricles, connected with the third ventricle of the thalamencephalon by a narrow foramen of Monro.

The third ventricle is connected with the optocoeles in the optic lobes and with the fourth ventricle in the medull oblonagata by a narrow aqueduct of sylvius or iter.

9. Ten pairs of cranial nerves arise from the brain.

Comparison: Vertebrates # Teleost:

1. The brain is enclosed within a bony cranium. It is divisible into a forebrain, made up of telencephalon and thalamencephalon; a midbrain or mesencephalon and a hindbrain consists of metencephalon and myelencephalon. The various lobes of the brain are situated in a straight line.

2. Olfactory lobes – The telencephalon has a nonnervous roof and the olfactory bulbs are placed in front of the cerebral hemispheres. It is concerned with the sense of smell.

3. Cerebral hemispheres – These are two, almost round, and will developed and are the seat of memory, intelligence and consciousness. The roof of the cerebral hemisphere is thin.

4. Thalamencephalon – It is well developed and the sides are produced into optic thalami, the seat of vision and possibly balance also. The floor and roof both are thin. On the roof, is a small rounded pineal body, representing the third ancestral eye. It is attached to the epiphysis.

The floor bears a hypophysis with a pituitary body, which is glandular and secretes different hormones of varied functions. The two sides of the hypophysis bear two thin-walled oval sacs, the lobiinferiores, which are produced behind the pituitary body and meet each other in the middle line.

A pair of sacci vasculosi are present The optic nerves do not form a chiasma, but simply cross one another or decussate. On leaving the brain, the right nerve goes to the left and left one goes to the right eye.

5. Mesencephalon – It bears a pair of oval optic lobes dorsally and longitudinal nerve fibres like crura cerebri ventrally. The optic lobes control vision.

6. Metencephalon – It consists of a large cerebellum, the anterior part of which pushes forward under the roof of the mesencephalon to form the valvula cerebelli. This is very characteristic of teleost fishes, and overlaps medulla oblongata behind. It is the centre for coordination of muscular movement and partly for balance also.

7. Myelencephalon – It is also known as medulla oblongata. It gradually tapers behind to end in the spinal cord. The roof of the myelencephalon is open.

8. The brain is hollow and bears several intercommunicated cavities of unequal dimensions. Cerebrospinal fluid circulates through these cavities or ventricles and the spinal cord. The cavities in the cerebral hemispheres are called first and second ventricles, connected with the third ventricle of the thalamencephalon by a narrow foramen of Monro.

The third ventricle is connected with the optocoeles in the optic lobes and with the fourth ventricle in the medull oblonagata by a narrow aqueduct of sylvius or iter.

9. Ten pairs of cranial nerves arise from the brain.

Comparison: Vertebrates # Bufo:

1. The brain is enclosed within a bony cranium. It is divisible into a forebrain, made up of telencephalon and thalamencephalon; a midbrain or mesencephalon and a hindbrain consists of metencephalon and myelencephalon. The various lobes of the brain are situated in a straight line.  

2. Olfactory lobes – The telencephalon has a nonnervous roof and the olfactory bulbs are placed in front of the cerebral hemispheres. It is concerned with the sense of smell.

3. Cerebral hemispheres – These are two, elongateoval and well-developed. (Rest as in teleost).

4. Thalamencephalon – It is well developed and the sides are produced into optic thalami, the seat of vision and possibly balance also. The floor and the roof both are thin. On the roof, is a thin stalk, the epiphysis bearing a small rounded pineal body, representing the third ancestral eye.

On the floor, is a hypophysis bearing a pituitary body, which is glandular and secretes different hormones of varied functions. An optic chiasma is present in front of the hypophysis.

5. Mesencephalon – It bears a paired of rounded optic lobes dorsally constituting the corpora bigemina and two longitudinal bands, crura cerebriventrally. The optic lobes control vision.

6. Metencephalon – It consists of a narrow, dorsal transverse band placed just behind the optic lobes and known as cerebellum. It is the centre for coordination of muscular movement and partly for balance also.

7. Myelencephalon – It gradually tapers behind to end in the spinal cord. The roof of the myelencephalon is open.

8. The brain is hollow and bears several intercommunicated cavities of unequal dimensions. Cerebrospinal fluid circulates through these cavities or ventricles and the spinal cord. The cavities in the cerebral hemispheres are called first and second ventricles, connected with the third ventricle of the thalamencephalon by a narrow foramen of Monro.

The third ventricle is connected with the optocoeles in the optic lobes and with the fourth ventricle in the medull oblonagata by a narrow aqueduct of sylvius or iter.

9. Ten pairs of cranial nerves arise from the brain.

Comparison: Vertebrates # Calotes:

1. The brain is enclosed within a bony cranium. It is divisible into a forebrain, made up of telencephalon and thalamencephalon; a midbrain or mesencephalon and a hindbrain consists of metencephalon and myelencephalon. The various lobes of the brain are situated in a straight line.

2. Olfactory lobes – The telencephalon has a nonnervous roof and the olfactory lober are connected with the anterior ends of the cerebral hemispheres by long and slender peduncles.

3. Cerebral hemispheres – These are two, almost semicircular and well developed. (Rest as in teleost).

4. Thalamencephalon – It is well developed and the sides are produced into optic thalami, the seat of vision and possibly balance also. The floor and the roof both are thin. On the roof, is a thin stalk, the epiphysis bearing a small rounded pineal body, representing the third ancestral eye.

On the floor, is a hypophysis bearing a pituitary body, which is glandular and secretes different hormones of varied functions. An optic chiasma is present in front of the hypophysis.

5. Mesencephalon – It bears a paired of rounded optic lobes dorsally constituting the corpora bigemina and two longitudinal bands, crura cerebriventrally. The optic lobes control vision.

6. Metencephalon – It consists of a small semicircular flap, the cerebellum which partly overlaps the medulla oblongata posteriorly. It is the centre for coordination of muscular movement and partly for balance also.

7. Myelencephalon – It is also known as medulla oblongata. It gradually tapers behind to end in the spinal cord. The roof of the myelencephalon is open.

8. The brain is hollow and bears several intercommunicated cavities of unequal dimensions. Cerebrospinal fluid circulates through these cavities or ventricles and the spinal cord. The cavities in the cerebral hemispheres are called first and second ventricles, connected with the third ventricle of the thalamencephalon by a narrow foramen of Monro.

The third ventricle is connected with the optocoeles in the optic lobes and with the fourth ventricle in the medull oblonagata by a narrow aqueduct of sylvius or iter.

9. Twelve pairs of cranial nerves arise from the brain.

Comparison: Vertebrates # Columba:

1. The brain is enclosed within a bony cranium. It is divisible into a forebrain, made up of telencephalon and thalamencephalon; a midbrain or mesencephalon and a hindbrain consists of metencephalon and myelencephalon. The various lobes of the brain are situated in a straight line.

The brain is more compact due to the appearance of flexure.

2. Olfactory lobes – The telencephalon has a nonnervous roof and the olfactory lobes are connected with the anterior ends of the cerebral hemispheres, which are poorly developed.

3. Cerebral hemispheres – These are two, large and extend behind to meet the cerebellum, covering the thalamencephalon dorsally. These are the seat of memory, consciousness and intelligence.

4. Thalamencephalon – It is well developed and the sides are produced into optic thalami, the seat of vision and possibly balance also. The floor and the roof both are thin. On the roof, is a thin stalk, the epiphysis bearing a small rounded pineal body, representing the third ancestral eye.

5. Mesence Phalon – It bears a pair of large, rounded laterally placed optic lobes constituting the corporabigemina and two longitudinal brand, cruracerebri ventrally. The optic lobes control vision.

6. Metencephalon – It consists of a comparatively large elongated cerebellum and is divisible into a large middle lobe, the surface of which is marked by grooves and a pair of small lateral lobes or floccule. It is the centre for coordination of muscular movement and partly for balance also. The 4^th ventricle is hidden by the cerebellum.

7. Myelencephalon – It is also known as medulla oblongata. It gradually tapers behind to end in the spinal cord. It has a well-marked ventral flexure. The fourhte ventricle is without any roof.

8. The brain is hollow and bears several intercommunicated cavities of unequal dimensions. Cerebrospinal fluid circulates through these cavities or ventricles and the spinal cord. The cavities in the cerebral hemispheres are called first and second ventricles, connected with the third ventricle of the thalamencephalon by a narrow foramen of Monro.

The third ventricle is connected with the optocoeles in the optic lobes and with the fourth ventricle in the medull oblonagata by a narrow aqueduct of sylvius or iter.

9. Twelve pairs of cranial nerves arise from the brain.

Comparison: Vertebrates # Cavia:

1. The brain in Cavia is similar to that in a bird.  

2. Olfactory lobes – The telencephalon has a nonnervous roof and the olfactory lobes are connected with the anterior ends of the cerebral hemispheres, which are poorly developed.

3. Cerebral hemispheres – The two cerebral hemispheres are large, long and narrow in front and posteriorly cover the optic lobes. The surface of the hemispheres is marked into convolutions by depressions or fissures and the lobes are frontal, temporal, parietal and occipital. The two hemispheres are connected by a transverse band of fibres, the corpus callosum. Corpus striatum is another band of connective nerve tissue below the ventricles. These are the seat of memory, intelligence and consciousness.

4. Thalamencephalon – It is small and thick as the side walls are produced into large optic thalami, the seat of vision and possibly balanced also. On the roof, is an epiphysis bearing the pineal body, representing the third ancestral eye. On the floor, is a hypophysis bearing a glandular pituitary body which secretes different hormones of varied functions. A rounded elevation, the corpus geniculatum is placed anterior to each optic thalamus. The hypophysis is prolonged posteriorly into a rounded mass, the corpus mammilare.

5. Mesencephalon – It bears a pair of large rounded dorsal optic lobes, thecorpora quadrigemina and two prominent, ventral longitudinal bands, the crura cerebri. The optic lobes control vision

6. Metencephalon – It consists of acomparatively large, elongated cerebellum subdivided into a median vermis and two lateral lobes. The vermis is marked by grooves and the lateral lobes bear floccule. A abnd of transverse fibres connect the two halves of the cerebellum and is known as pons varoli. The metencephalon is the centre for coordination of muscular movement and partly for balance also.

7. Myelencephalon – It is also known as medulla oblongata. It gradually tapers behind to end in the spinal cord. It has a well-marked ventral flexure. The fourhte ventricle is without any roof.

8. The brain is hollow and bears several intercommunicated cavities of unequal dimensions. Cerebrospinal fluid circulates through these cavities or ventricles and the spinal cord. The cavities in the cerebral hemispheres are called first and second ventricles, connected with the third ventricle of the thalamencephalon by a narrow foramen of Monro.

The third ventricle is connected with the optocoeles in the optic lobes and with the fourth ventricle in the medull oblonagata by a narrow aqueduct of sylvius or iter.

9. Twelve pairs of cranial nerves arise from the brain.