parts of nervous system neuron nerve fibers and nerve trunk cranial nerves

1. The nervous system
Chapter one
Dr. Haydar muneer Salih

2. Before we begin !
Define Anatomy?

3. • Anatomy came from Greek word
Ana = up , tome = cutting
Scientific study of body structure

4. What is nervous system (define) ?
Nervous system is the system which
responds to the internal and external
environments in order to maintain the
internal environment and manipulate the
external environment for survival and
existence

5. PARTS OF NERVOUS SYSTEM
1. Central nervous system (CNS):
a. Brain:
b. Spinal cord:
2. Peripheral nervous system (PNS)
It includes those parts of nervous system
which lie outside the central nervous
system. It consists of twelve pairs of cranial
nerves, thirty one pairs of spinal nerves,
somatic and special sense receptors and the
autonomic nervous system

7. Brain
• It lies in the cranial cavity and continues as the
spinal cord. It consists of following parts
1. Forebrain
a. Cerebrum
b. Diencephalon
2. Midbrain
3. Hind brain
pons
medulla oblongata
cerebellum

8. Brain

9. Brain

10. Spinal cord
• It is also known as spinal medulla. It is the caudal,
elongated part of central nervous system which
occupies the upper 2/3rd of the vertebral canal.
• spinal cord segment. There are 31 pair of spinal
nerves hence, 31 spinal cord segments. These are
• 8 cervical segments
• 12 thoracic segments
• 5 lumbar segments
• 5 sacral segments
• 1 coccygeal segment

11. Spinal cord

13. Peripheral nervous system
As mentioned earlier it consist of
• 31 spinal nerves and 12 cranial nerves
• Somatic nervous system: This deals with the changes
in the external environment
• Autonomic nervous system: It has two components
namely:
a. Sympathetic nervous system
b. Parasympathetic nervous system
• It is concerned with the regulation of visceral
functions that maintain the internal homeostasis and
works mostly at the unconscious level

15. Nerve fiber & nerve trunk

16. Ganglia

17. Synapse

18. CRANIAL NERVES
I. Olfactory
II. Optic
III. Oculomotor
IV. Trochlear
V. Trigeminal
VI. Abducent
VII. Facial
VIII. Vestibulocochlear
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XII. Hypoglossal

19. CRANIAL NERVES
• The olfactory I, optic II, and
vestibulocochlear nerves VIII are entirely
sensory;
• The Oculomotor III, trochlear IV, abducent
VI, accessory XI, and hypoglossal nerves XII
are entirely motor;
• And the remaining nerves are mixed.

21. OLIFACTORY NERVE ( CN I)
• The olfactory nerves arise from olfactory
receptor nerve cells in the olfactory
mucous membrane. The olfactory
mucous membrane is situated in the
upper part of the nasal cavity above the
level of the superior concha. Bundles of
these olfactory nerve fibers pass through
the openings of the cribriform plate of
the ethmoid bone

22. OLIFACTORY NERVE (CN I)

23. OPTIC NERVE (CN II)
• It carries special sensory fibers for vision.
These fibers return information to the
brain from photoreceptors in the retina.
Neuronal processes leave the retinal
receptors, join into small bundles, and
are carried by the optic nerves to other
components of the visual system in the
brain. The optic nerves enter the cranial
cavity through the optic canals

24. OPTIC NERVE (CN II)

25. OCULOMOTOR NERVE (CN III )
• The oculomotor nerve emerges on the
anterior surface of the midbrain.
• The oculomotor nerve supplies the
following:
The extrinsic muscles of the eye
The intrinsic muscles of the eye

26. OCULOMOTOR NERVE (CN III )

27. TROCHLEAR NERVE (CN IV)
• The trochlear nerve is the most slender
of the cranial nerves. It then passes
forward through the middle cranial fossa
in the lateral wall of the cavernous sinus
and enters the orbit through the superior
orbital fissure.
• The trochlear nerve supplies: The
superior oblique muscle of the eyeball
(extrinsic muscle).

28. ABDUCENT NERVE (CN VI)
• This small nerve emerges from the
anterior surface of the hindbrain. It
passes forward with the internal carotid
artery through the cavernous sinus in the
middle cranial fossa and enters the orbit
through the superior orbital fissure. The
abducent nerve supplies the lateral
rectus muscle and is therefore
responsible for turning the eye laterally

30. Vestibulocochlear Nerve (CN VIII)
• The vestibulocochlear nerve is a sensory
nerve that consists of two sets of fibers:
vestibular (balance) and cochlear
(hearing). It attaches to the lateral
surface of the brainstem, between the
pons and medulla, after emerging from
the internal acoustic meatus and crossing
the posterior cranial fossa.

32. Glossopharyngeal Nerve (CN IX)
• The glossopharyngeal nerve is a motor
and sensory nerve.
• It emerges from the anterior surface of
the medulla oblongata.
• It leaves the skull by passing through the
jugular foramen.

33. Glossopharyngeal Nerve (CN IX)

34. VAGUS NERVE (CN X)
• The vagus nerve is composed of motor and
sensory fibers.
• It emerges from the anterior surface of the
medulla oblongata.
• The nerve leaves the skull through the jugular
foramen. The cranial root of the accessory
nerve joins the vagus nerve.
• The vagus nerve descends through the neck
alongside the carotid arteries and internal
jugular vein within the carotid sheath

35. VAGUS NERVE (CN X)

36. ACCESSORY NERVE (CN XI)
• Cranial Root
The cranial root emerges from the anterior
surface of the medulla oblongata. The nerve runs
laterally in the posterior cranial fossa and joins
the spinal root.
• Spinal Root
The spinal root arises from nerve cells in the
anterior gray column (horn) of the upper five
segments of the cervical part of the spinal cord.
• The two roots unite and leave the skull through
the jugular foramen

37. ACCESSORY NERVE (CN XI)

38. HYPOGLOSSAL NERVE (CN XII )
• The hypoglossal nerve is a motor nerve.
It emerges on the anterior surface of the
medulla oblongata, crosses the posterior
cranial fossa, and leaves the skull through
the hypoglossal canal. The nerve then
passes
• downward and forward in the neck and
crosses the internal and external carotid
arteries to reach the tongue

39. HYPOGLOSSAL NERVE (CN XII )

42. Brain

44. CRANIAL NERVES
I. Olfactory
II. Optic
III. Oculomotor
IV. Trochlear
V. Trigeminal
VI. Abducent
VII. Facial
VIII. Vestibulocochlear
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XII. Hypoglossal

45. CRANIAL NERVES
• The olfactory I, optic II, and
vestibulocochlear nerves VIII are entirely
sensory;
• The Oculomotor III, trochlear IV, abducent
VI, accessory XI, and hypoglossal nerves XII
are entirely motor;
• And the remaining nerves are mixed.

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