Diving into the Depths: Unraveling the Wonders of the Fish Nervous System Beneath the sparkling surface of oceans and rivers unfolds a hidden world of silent ballet, electrifying signals, and exquisite sensory perception. Here, where sunlight fades into an emerald gloom, the fish nervous system reigns supreme, an invisible conductor orchestrating the lives of countless aquatic marvels. Unlike the grand orchestration of our own, their symphony plays out in a condensed score, yet resonates with complexity and wonder. A Streamlined Masterpiece: While mammals boast a three-part nervous system, the fish world operates on a streamlined architecture. Their central nervous system (CNS), nestled within the skull, combines processing power and communication lines into one streamlined unit. The brain, though smaller than ours, acts as the command center, analyzing sensory information and issuing instructions through a network of nerves that course through their slender bodies. The spinal cord, running along the back like a luminous highway, relays messages between brain and muscle, ensuring their every fin flick and twitch is precisely coordinated. Sensing the Secrets of the Water: Unbeholden to the limitations of terrestrial sight and sound, fish have honed their senses to excel in the aquatic realm. Their vision, often keen and adaptable, paints the underwater world in vivid hues, letting them track prey, navigate through coral reefs, and avoid lurking predators. Smell and taste take on amplified roles, with exquisite chemoreceptors detecting dissolved chemicals like a gourmet savoring the finest spices. They can sniff out food, sense danger, and even detect potential mates with a precision that puts our noses to shame. But the water offers secrets beyond these familiar senses. The lateral line system, a series of sensory cells lining their bodies, acts like an underwater radar. By detecting subtle changes in water pressure, they sense approaching predators, navigate currents, and even communicate with each other in ways we can only dream of understanding. And for some, like the majestic sharks, the world hums with an electric symphony. Electroreception allows them to perceive the faintest electrical fields, aiding in hunting, guiding through murky waters, and even revealing the hidden emotions of their kin. Masters of Movement: Fish dance through the water with an effortless grace that belies the intricate calculations powering their every movement. The cerebellum, housed within the brain, acts as a master choreographer, fine-tuning muscle coordination for balance and smooth swimming. The optic tectum, a specialized area dedicated to vision, processes visual information with lightning speed, allowing them to track prey and avoid obstacles in the blink of an eye. Every fin beat, every twist and turn, is orchestrated by the symphony of nerves relaying signals from brain to muscle, translating thought into fluid motion.

1. PRESENTED BY: KHADEEJA AZHAR
MAHNOOR BAIG

3. INTRODUCTION:
In fishes nervous system is the primary mechanism
to coordinating and integrating body activities
The stimuli are received by the nervous system through
sense organs.
Functioning of nervous system- based on the
electrical properties of it's functional units-
neurons
 Nervous system is derived from ectoderm
Nervous system divisible into:
Central nervous system
Peripheral nervous system
Autonomous nervous system

5.  Fish possess a well developed nervous system consisting of
brain, spinal cord and the nerves whose function is to
coordinate the activities of the body.
 Brain: shows considerable variations in its size in relation to the
body in different species and does not occupy the entire cranial
cavity. The space b/w cranium and brain is full of gelatinous
substance.
 Fish typically have quite small brains relative to body size
compared with other vertebrates. › 1/5th size of similarly sized
mammal or bird.
 But, in is some fishes like mormyrids and have large brains.

6.  Teleostean brain is divided into three region:
 Prosencephalon (fore brain)
 Mesencephalon (mid brain)
 Rhombencephalon (hind brain)

12. o Two ganglios of almost equal size are present in
the epithalamus and are called the habenulae.
o Hebenulae receives a massive afferent input
from the pineal gland and a moderate input
from the olfactory region and telencephalon.
o The grandular pineal body arise from dorsal
wall of dicephalon and is considered to be an
endocrine gland.

13.  Hypothalamus exercises control over the
endocrine system of the fish through
hypophysis. It contains neurosecretory cells
and their secretions are carried to the
hypophysis, influencing its activities.

14. o Mesencephalon consist of dorsally situated
optic tectum and ventral situated tegmentum.
o The optic tectum forms two optic lobes.
o The optic tectum projects into optocoel and
forms a pair of torus longitudinalis which is a
characteristic feature of all the teleost.
Function as a correlation centre for
photostatic and gravistatic area of brain

17.  Metencephalon consists of cerebellum.
 The cerebellum is a single lobed structure that is usually very large,
typically cerebellum is the biggest part of brain.
 Hagfish and lampreys have relatively small cerebellum but at the other
hand, the cerebellum of mormyrids (Elephant fish) is massively
developed.
 Metencephalon is particularly involved in swimming & in balance, as it
maintains body posture by coordinating muscular activities.

18.  Myelencephalon also called as
brain stem.
 It is the most posterior part of
the brain.
 It controls the functions of the
muscles and body organs.
 In case of bony fishes,
Myelencephalon or brain stem is
concerned with respiration and
osmoregulation.

21. The spinal nerves arise in pairs from the spinal
cord and are metamerically arranged.
Each spinal nerve has a dorsal and a ventral root
originating from spinal cord and is of a mixed type
containing both sensory and motor fibres.
Both the roots join to form the mixed nerve
which emerges out of the vertebral column
through the inter- vertebral aperture. The dorsal
root is mainly sensory while the ventral one
contains motor fibres.

22. Ten pairs of cranial nerves in
fishes:
› First pair- Olfactory nerve
› Second pair- Optic nerve
› Third pair-Oculomotor nerve
› Forth pair- Trochlear nerve
› Fifth pair- Trigeminal nerve
› Sixth pair- Abduscens nerve
› Seventh pair – Facial nerve
› Eighth pair- Auditory nerve
› Ninth pair- Glossopharyngeal
› Tenth pair- Vagus nerves

23.  OLFACTORY NERVE: It carries smell impulse.
 OPTIC NERVE: It carries visual impulse.
 OCULOMOTOR NERVE: It allows movement of the
eye muscles & constriction of pupil.
 TROCHLEAR NERVE: It enables movement of
oblique muscles of eyes. Oblique muscles are the
muscles which are responsible for eye movement.
 TRIGEMINAL NERVE: This nerve is responsible for
sending pain, touch and temperature sensations
from face to brain.

24.  ABDUCENS NERVE: The abducens nerve functions to
innervate the lateral rectus muscles of eyeball.
 FACIAL NERVE: It control facial movements by
innervating facial muscles.
 AUDITORY NERVE: Also called cochlear nerve, is cranial
nerve responsible for hearing. It is the sensory nerve
that transfers auditory information from the cochlea(
auditory area of the inner ear) to the brain.
 GLOSSOPHARYNGEAL NERVE: It has both sensory(
sensation) and motor (movement) functions. It is
responsible for taste & swallowing.
 VAGUS NERVE: It is responsible for the regulation of
internal organ functions, such as digestion, heart rate &
respiratory rate.

25.  The autonomic nervous system consists of
ganglia, fibers, and of both the sympathetic and
parasympathetic parts.
 Autonomic nervous system is generally less
prominent in fish. This system does not possess
many typical functions of a nervous system, and is
placed under this category mainly because its
parts are closely connected to either the brain or
spinal cord.

26.  This system is composed of parasympathetic
and sympathetic parts, used to activate and
inactivate muscles of different parts of body
systems.
 Ganglia, the main component of this system,
contain fibers used to connect the nervous
system to the muscles of the body.