Nervous System of Scoliodon | Shark | Diagram

The nervous system of Scoliodon consists of three parts :
1. Central nervous system.
2. Peripheral nervous system.
3. Autonomic nervous system.

1. Central Nervous System of Scoliodon

• It includes the brain and spinal cord of the Scoliodon.

A. The Brain of Scoliodon

• • • The brain of Scoliodon lies enclosed within the chondrocranium.
    • It is covered with meninges.
    • It is made of the same three basic parts forebrain, midbrain, and hindbrain.

I) Forebrain

• • • It is the anterior part of the brain.
    • It is subdivided into two parts and they are cerebrum and diencephalon.

a) Cerebrum

• • • It is also known as the cerebral hemisphere.
    • It is the anteriormost part of the brain as well as the forebrain.
    • It is undivided and has no mid-dorsal groove indicating the right and left cerebral hemispheres of higher vertebrate animals.
    • From either antero-lateral side of the cerebrum arises an olfactory lobe.
    • The midventral portion of the cerebrum has a small aperture called the neuropore.
    • A terminal nerve comes out of each neuropore to innervate the mucous membrane of the olfactory sacs.

b) Diencephalon

• • • Diencephalon is located posterior to the cerebrum.
    • It is completely hidden by the cerebellum.
    • The roof of the diencephalon is called the anterior choroid plexus.
    • A pineal body or epiphysis of unknown function is present at the mid-dorsal region of the diencephalon.
    • Ventrally, at the anterior margin of the diencephalon, lies the optic chiasma.
    • The optic chiasma is formed by the crossing of the two optic nerves.
    • Just behind the chiasma, the floor gives off the infundibulum.

II) Midbrain

• • • It is the middle portion of the brain.
    • It consists of a pair of large and rounded option lobes or corpora bigemina.
    • Optic lobes are mainly responsible for the sense of sight.
    • The oculomotor and trochlear cranial nerves arise from the midbrain.

III) Hindbrain

• • • It is the posterior portion of the brain.
    • It comprises two parts, cerebellum and medulla oblongata.

a) Cerebellum

• • • It is rhomboidal in shape.
    • The dorsal surface of the cerebellum shows irregular folds
    • It is divided into three lobes by two transverse furrows.
    • Sometimes, a median longitudinal furrow may also divide the cerebellum into right and left halves.
    • It is the center of co-ordination of body movement.

b) Medulla Oblongata

• • • It is the posteriormost part of the brain.
    • It is triangular in shape.
    • It continues posteriorly into the spinal cord.
    • V, VI, VII, VII, IX and X cranial nerves arise from the medulla oblongata.

B. Spinal Cord of Scoliodon

• • • The spinal cord extends from the medulla oblongata almost to the end of the tail.
    • It is protected by the neural canal of vertebrae.
    • In structure, it resembles that of higher vertebrates in having dorsal and ventral fissures, central canal, and inner grey and outer white matter.

2. Peripheral Nervous System of Scoliodon

• It includes cranial nerves and spinal nerves of the Scoliodon.

A. Cranial Nerves of Scoliodon

• • • The brain gives off 10 pairs of cranial nerves.
    • They are identified by their serial Roman numbers as well as names.

All ten pairs of cranial nerves of Scoliodon are given below:-

B. Spinal Nerves of Scoliodon

• • • Several pairs of spinal nerves arise from spinal cord.
    • Each nerve, originates by two roots, a sensory dorsal root and a motor ventral root.
    • Each spinal nerve divides into three branches; ramus dorsalis, ramus ventralis and ramus communicans.

3. Autonomic Nervous System of Scoliodon

• It includes a series of paired and irregularly arranged ganglia in the dorsal wall of posterior cardinal sinuses, and in dorsal parts of kidneys.
• The gastric ganglion is the largest ganglion.
• There is usu­ally one ganglion in each segment.

———– THE END ———-

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4. External Morphology of Scoliodon with Diagram | Dog fish
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6. Respiratory System of Scoliodon | Dog Fish | Diagram
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8. General Characters of All Classes of Vertebrates.

Reference:

1. Nervous system of Scoliodon – Youtube

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