this slide will help undergraduate student to study the brain of scoliodon

1. Brain of Scoliodon
Nusrat Perween, AISC Pune 1

2. The nervous system of Scoliodon includes:
(i) The central nervous system (CNS)
(ii) The peripheral nervous system (PNS)
(iii) The autonomous nervous system (ANS)
Nusrat Perween, AISC Pune 2

3. (i) Central nervous system:
(a) Brain:
(b) Spinal cord:
(ii) Peripheral nervous system:
• cranial nerves and spinal nerves.
(iii) Autonomous nervous system:
• series of paired ganglia (sympathetic and parasympathetic)
Nusrat Perween, AISC Pune 3

4. Introduction
• Brain of shark is heavy and large
• Externally covered by cranium, made up of cartilage and two
connective tissue membranes called meninges
• thick membrane dura- mater and thin membrane close to brain
pia- mater
• Brain and spinal cord is hallow from inside and cavities called
ventricles
• Space between meninges and ventricle of brain are filled with
cerebro-spinal fluid
• Special feature- Olfactory lobes and cerebellum well developed
Nusrat Perween, AISC Pune 4

5. Brain of Scoliodon
The brain is divided into three
primary parts:
(a) Forebrain or Prosencephalon
(b) Midbrain or Mesencephalon
(c) Hindbrain or Rhombencephalon
5

6. a) Forebrain or Prosencephalon
Two part
1) Telencephalon-
i. Olfactory lobes
ii. Cerebrum
2) Diencephalon
6Dorsal view Ventral view

7. i) Olfactory lobes
• Anterior end of cerebral hemisphere
arise two stout olfactory peduncles;
each terminates into a large bilobed
olfactory lobe
1. Olfactory bulb
2. Olfactory sac
3. Olfactory peduncle
• Cavity of olfactory lobe- Rhinocoels
(1st ventricle)
• Function- sense of smell
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Nusrat Perween, AISC Pune

8. ii) Cerebrum
• 2nd part of Telencephalon
• massive undivided mass of nervous tissue
• larger than other fishes.
• Neuropore- ventrally on the cerebrum, through which terminal or pre-
olfactory nerve comes out
• Cavities – paracoels or lateral ventricles (2nd ventricle)
• Function- all voluntary activities
Nusrat Perween, AISC Pune
8

9. 2. Diencephalon
• Present behind cerebrum (The
posterior part of forebrain)
• Completely covered by cerebellum
on dorsal side
i. Epithalamus (Pineal body)
ii. Hypothalamus
iii. Infundibulum
iv. Optic chiasma
v. Pituitary gland (hypophysis)
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Nusrat Perween, AISC Pune

10. i. Anterior choroid plexus (telachoroidea):
• The roof of the diencephalon is thin, non-nervous and
highly vascular known as the anterior choroid plexus.
• Secretes cerebrospinal fluid and supplies nutrition to
cavities of brain
ii. Epithalamus:
• It comprises of epiphyris or pineal organ and habenular
gangalia
• Pineal body arises from posterior mid-dorsal end of
diencephalon
• Long and tubular
• The lateral walls of the diencephalon form two thickened
bodies called thalami.
• Function- not known, may be involved in reception of light
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11. iii. Hypothalamus
• Ventral part of diencephalon
• Very well developed in fishes
• Contains neuro-secretory cells
• Functions- secretes neuro-secretary material
iv. Infundibulum
• Arises from floor of diencephalon
• Along the sides there are thick walled sacs called
inferior lobes
• Near distal end of each inferior lobe is wrinkled
glandular sac called saccus-vasculosus
• Saccus-vasculosus is highly pigmented ,vascular and
folded
• Saccus-vasculosus function- depth reception,
secretion of ventricular fluid
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12. v. Optic chiasma
• On ventral side of brain in front of infundibulum
the two optic nerves arising from each eye ball
cross and form optic chiamsa (X)
vi. Pituitary gland
• Large in elasmobranchs
• Present on ventral side behind the infundibulum
(hidden)
• Divided into 3 parts- Anterior, dorsal and ventral
lobes
• Ventral lobe –prominent secretes TSH and FSH
• Cavity of diencephalon is called as diocoel (3rd
ventricle)
• Both cavities are join through foramen of Monro
12

13. • Dorsally and ventrally covered by
cerebellum and infundibulum
• large and consists of two round optic
lobes.
• Ventricle –optocoel connected to diocoel
by iter or aqueduct of sylvius
• Function –sense of vision
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Midbrain or mesencephalon

14. Hindbrain or Rhombencephalon
i. Cerebellum
ii. Medulla oblongata
14
Nusrat Perween, AISC Pune

15. • Highly developed cerebellum and a medulla
oblongata.
• Rhomboidal in shape
• The dorsal surface of the cerebellum shows
irregular folds
• Median longitudinal furrow – right and left
halves
• Two transverse furrow- three lobes
• Cavity – epicoel
• Function- center of co-ordination of body
movement
15
i. Cerebellum

16. • Posterior most part of brain
• Triangular in shape
• anterior end gives a pair of hollow
corpora restiformia
• The roof of the medulla oblongata is
non-nervous and highly vascular and
form posterior choroid plexus that
projects into ventricle and provide
nourishment
• The hind- brain controls swimming
movements.
• Cavity – metacoel or 4th ventricle
• Function- controls involuntary activities
16
ii. medulla oblongata or myelencephalon

17. Nusrat Perween, AISC Pune
17
Nusrat Perween, AISC Pune

18. 18
1. Olfactory lobes- Rhinocoel or 1st
ventricle
2. Cerebrum- paracoels or lateral
ventricles (2nd ventricle)
3. Diencephalon- diocoel (3rd ventricle)
4. Both diocoel are join through foramen
of Monro
5. Optic lobes- optocoel
6. Optocoel is connected to diocoel by iter
or aqueduct of sylvius
7. Cerebellum- epicoel
8. Medulla oblongata- metacoel or 4th
ventricle
Cavities or ventricles of brain