Nervous system of fishes. lagler ichthyologypptx

this presentation is prepared from laglar book titled ichthyology

1. Nervous system Presented by: Faisal Sadiq

2. Cerebrospinal system brain , spinal cord, cranial and spinal nerves. Autonomic system ganglia , nerve fibers, sympathetic and parasympathetic parts

3. Central nervous system Forebrain: Telencephalon metencephalon cerebral hemispheres and tween brain Mid brain mesencephalon optic lobes Hind brain Metencephalon mylencephalon cerebellum and medulla

4. Telencephalon The most anterior region involved in olfactory reception Olfactory lobe on each side followed by olfactory bulb . Olfactory nerve or cranial nerve 1 enters this region In elasmobranches and bony fishes , terminal nerve also.

5. Diencephalon: a constriction behind telencephalon also known as tween brain Saccus dorsalis form the roof of the cavity within diencephalon. Pineal and parapineal organs; also known as epiphysial organs located slightly right and left side of the midline respectively.

6. Epitheliamic region; it consists of thalamus and hypothalamus as important conmponents

7. Pineal and parapineal organs These are linked to reception of diffuse light stimulus Pineal organ is well developed in vertically migrating fishes Hatchet fishes, catfishes and halfbeaks Its secretory roles it may be endocrine functions In sharks and bony fishes, only pineal organ is present

8. Thalamus and hypothalamus; Thalamus serves as relay centre for transfer olfactory impulses to thalamo -medullar and thalemo -spinal tract. Hypothalamus affects the endocrine system through pituitary gland.

9. Mesencephalon It is relatively large in fishes. It consists of dorsal optic tactum , which appear two optic lobes in dorsal view and ventral tagmatum . It correlate visual impressions with muscular responses. For example facing prey or swimming to moving objects.

10. Metencephalon In metencephalon , cerebellum devalope from underlying large medulla as dorsal outgrowth of 4 th ventricle. Its prominent functions are swimming equilibration, maintenance of muscular tonus, orientation in space.

11. Myelencephalon Also known as brainstem . Medulla oblongata is its main component. It is a centre to which lead the sensory nerves except those of smell and sight.

12. Cross section of spinal cord shows a central region of gray substance consisting of nerve cells and a surrounding area of white matter consisting of myelinated nerve fibers . In centre of the gray matter is central canal . Gray matter resemble letter X with paired dorsal and ventral horns. Dorsal horn receives somatic and visceral sensory fibers and ventral horn contain motor nuclei .