FISH-CENTRAL-NERVOUS-SYSTEM the part of nervous system which in invertebrates.

Consist of Brain and Spinal cord

1. FISH CENTRAL NERVOUS SYSTEM

2. The Central Nervous System The part of the nervous system which in vertebrates consist of BRAIN and SPINAL CORD, to which sensory impulses are transmitted and from which motor impulses pass out, and coordinates the activity of the entire nervous system. 2

3. 3 PNS CNS Brain and Spinal Cord Sympathetic nervous system "fight or flight" Parasympathetic nervous system "rest and repose" Somatic nervous system (voluntary) Sensory neurons registering external stimuli Autonomic nervous system (involuntary) Sensory Pathways Motor Pathways central nervous system (CNS) peripheral nervous system (PNS) Sensory neurons registering external stimuli

4. Vertebrate Brains All vertebrate brains have three basic divisions: Hindbrain Midbrain Forebrain In fishes, Hindbrain – largest portion Midbrain – processes visual information Forebrain – processes olfactory information 4

5. 5 Vertebrate Brains

6. 6 Vertebrate Brains Relative sizes of different brain regions have changed as vertebrates evolved Forebrain became the dominant feature

7. PROJECTION OF SENSORY INPUT

8. SENSORY SYSTEM OF FISH OLFACTION - In all vertebrates, the only primary sensory receptor cells in teleost are located in the olfactory mucosa and reach the glomerular layer of the olfactory bulbs. VISION - most teleosts are highly visually guided animals and some of their capabilities involving this sensory modality are impressive. MECHANORECEPTION – mechanosensory information reaches the brain via the lateral line nerves. ELECTRORECEPTION – as all other sensory systems described here, the perception of weak electric fields is a plesiomorphic character of vertebrates. AUDITION - the auditory capabilities of many teleost are impressive. Auditory signals are perceived for greater distances compared to mechanosensory signals, and the perceived frequency range is up to 3000 Hz.

9. f. VESTIBULAR SENSE - the peripheral receptor cells that mediate the sense of balance are found in the inner ear semicircular canal and olithic endorgans . g. GUSTATION - the gustatory system of fishes can be differentiated from the olfactory system primarily based on its peripheral and central anatomy. h. GENERAL VISCERAL SENSE - in addition to the special viscerosensory modality (gustation), the teleostean vagal nerve also encodes general viscerosensory stimuli from the viscera to the CNS, notably to the nucleus commissuralis of Cajal . i . SOMATOSENSATION - teleost appear to have a relay center at the spinal cord-brainstem junction for ascending somatosensory fibers similar to the dorsal column cuneate and gracile nuclei in mammals.

10. Hearing and Equilibrium in Other Vertebrates Unlike mammals, fishes have only a pair of inner ears near the brain Most fishes and aquatic amphibians also have a lateral line system along both sides of their body The lateral line system contains mechanoreceptors with hair cells that detect and respond to water movement © 2011 Pearson Education, Inc.

11. Figure 50.14 Lateral line Cross section SURROUNDING WATER FISH BODY WALL Scale Epidermis Lateral line canal Opening of lateral line canal Segmental muscle Lateral nerve Cupula Sensory hairs Hair cell Supporting cell Nerve fiber

12. The optic nerves meet at the optic chiasm near the cerebral cortex Sensations from the left visual field of both eyes are transmitted to the right side of the brain Sensations from the right visual field are transmitted to the left side of the brain © 2011 Pearson Education, Inc. Processing of Visual Information in the Brain

13. Figure 50.20 Right visual field Left visual field Right eye Left eye Optic chiasm Optic nerve Lateral geniculate nucleus Primary visual cortex

14. CEREBELLUM The teleostean cerebellum includes three parts: a. VESTIBULOLATERALIS LOBE – is likely to be homologous to the vestibulocerebellum present in all vertebrates since it receives primary octaval (presumably vestibular) as well as lateral line projections. b. CORPUS CEREBELLI – lies on top of the rostral rhombencephalon as in all vertebrates. c. VALVULA CEREBELLI – extends into the tectal ventricle.

15. AUTONOMIC NERVOUS SYSTEM A part of the vertebrate nervous system that innervates smooth and cardiac muscle and glandular tissues and governs involuntary actions ( as secretion and peristalsis) and that consist of the following: SYMPATHETIC NS - part of the ANS that contains chiefly adrenergic fibers and tends to depress secretion, decrease the tone and contractility of smooth muscle and increase heart rate. PARASYMPATHETIC NS - part of the ANS that contains chiefly cholinergic fibers that tends to induce secretion, to increase the tone and contractility of smooth muscle, and to slow heart rate, and that consist of cranial and sacral part.

16. REFERENCES DAVID H. EVANS, The Physiology of Fishes 2 nd Edition AIRHART, M. J. and KRRIEBEL, R. M., Telencephalic terminals in the major retinal synaptic lamina of the goldfish optic tectum . Brain Res.