by Daniel merga from KEAMED University college Ethiopia Finfinne

1. NERVOUS SYSTEM
BY: SOLOMON E.

2. Functions of the Nervous System
1. Sensory input – gathering information
• To monitor changes occurring inside and
outside the body (changes = stimuli)
2. Integration –
• to process and interpret sensory input
and decide if action is needed.
3. Motor output
• A response to integrated stimuli
• The response activates muscles or glands

3. Structural Classification of the
Nervous System
• Central nervous system (CNS)
• Brain
• Spinal cord
• Peripheral nervous system (PNS)
• Nerve outside the brain and spinal cord
 Spinal nerves
 Cranial nerves

4. Functional Classification of the
Peripheral Nervous System
 Sensory (afferent) division
 Nerve fibers that carry information to the central
nervous system
 Motor (efferent) division
 Nerve fibers that carry impulses away from the
central nervous system
 Two subdivisions
 Somatic nervous system = voluntary
 Autonomic nervous system = involuntary

5. Nervous Tissue: Neurons
• Neurons = nerve cells
• Cells specialized to transmit messages
• Major regions of neurons
• Cell body – nucleus and metabolic center
of the cell
• Processes – fibers that extend from the
cell body (dendrites and axons)

6. Neuron Anatomy
• Extensions outside the
cell body
• Dendrites – conduct
impulses toward the
cell body
• Axons – conduct
impulses away from
the cell body

7. Axons and Nerve Impulses
• Axons end in axonal terminals
• Axonal terminals contain vesicles with
neurotransmitters
• Axonal terminals are separated from the
next neuron by a gap
• Synaptic cleft – gap between adjacent
neurons
• Synapse – junction between nerves

8. Functional Classification of
Neurons
• Sensory (afferent) neurons
• Carry impulses from the sensory receptors to the CNS
• Cutaneous sense organs
• Proprioceptors – detect stretch or tension
• Motor (efferent) neurons
• Carry impulses from the central nervous system to
viscera, muscles, or glands
• Interneurons (association neurons)
• Found in neural pathways in the central nervous system
• Connect sensory and motor neurons

9. Neuron Classification

10. Structural Classification of Neurons
• Multipolar neurons
– many extensions
from the cell body
• Bipolar neurons –
one axon and one
dendrite
• Unipolar neurons
– have a short
single process
leaving the cell
body

11. Central Nervous System (CNS)
Regions of the
Brain
•Cerebral
hemispheres
(cerebrum)
•Diencephalon
•Brain stem
•Cerebellum

12. Regions of the Brain: Cerebrum
 Cerebral Hemispheres
(Cerebrum)
 Paired (left and
right) superior
parts of the brain
 Includes more than
half of the brain
mass
 The surface is
made of ridges
(gyri) and grooves
(sulci)

13. Regions of the Brain: Cerebrum
 Lobes of the cerebrum
 Fissures (deep
grooves) divide the
cerebrum into lobes
 Surface lobes of the
cerebrum
 Frontal lobe
 Parietal lobe
 Occipital lobe
 Temporal lobe

14. Regions of the Brain: Cerebrum
 Specialized areas of the cerebrum
 Primary somatic sensory area
 Receives impulses from the body’s sensory
receptors
 Located in parietal lobe
 Primary motor area
 Sends impulses to skeletal muscles
 Located in frontal lobe
 Broca’s area
 Involved in our ability to speak

15. Regions of the Brain: Cerebrum

16. Specialized Area of the Cerebrum
• Cerebral areas involved in special senses
• Gustatory area (taste)[in insula]
• Visual area[occipital lobe]
• Auditory area
• Olfactory area
• Interpretation areas of the cerebrum
• Speech/language region
• Language comprehension region
• General interpretation area

17. Layers of the Cerebrum
 Layers of the cerebrum
 Gray matter—outer layer in the cerebral cortex
 composed mostly of neuron cell bodies
 White matter—fiber tracts inside the gray
matter
 Example: corpus callosum connects
hemispheres
 Basal nuclei—islands of gray matter buried within
the white matter

18. Diencephalon
• Sits on top of the
brain stem
• Enclosed by the
cerebral heispheres
• Made of three parts
• Thalamus
• Hypothalamus
• Epithalamus

19. Diencephalon

20. Thalamus
• Surrounds the third ventricle
• The relay station for sensory impulses
• Transfers impulses to the correct part of
the cortex for localization and
interpretation

21. Hypothalamus
• Under the thalamus
• Important autonomic nervous system center
• Helps regulate body temperature
• Controls water balance
• Regulates metabolism
• An important part of the limbic system
(emotions)
• The pituitary gland is attached to the
hypothalamus

22. Epithalamus
• Forms the roof of the third ventricle
• Houses the pineal body (an endocrine
gland)
• Includes the choroid plexus – forms
cerebrospinal fluid

23. Brain Stem
• Attaches to
the spinal
cord
• Parts of the
brain stem
• Midbrain
• Pons
• Medulla
oblongata

24. Brain Stem
• Midbrain
 Mostly composed of tracts of nerve fibers
 Has two bulging fiber tracts—cerebral peduncles
 Has four rounded protrusions- corpora quadrigemina
 Reflex centers for vision and hearing
 Cerebral aqueduct – 3rd-4th ventricles
• Pons
 The bulging center part of the brain stem
 Mostly composed of fiber tracts
 Includes nuclei involved in the control of breathing

25. Medulla Oblongata
• The lowest part of the brain stem
• Merges into the spinal cord
• Includes important fiber tracts
• Contains important control centers
• Heart rate control
• Blood pressure regulation
• Breathing
• Swallowing
• Vomiting

26. Cerebellum
• Two hemispheres
with convoluted
surfaces
• Provides
involuntary
coordination of
body movements

27. Protection of the Central Nervous
System
 Scalp and skin
 Skull and
vertebral
column
 Meninges
 Cerebrospinal
fluid (CSF)
 Blood-brain
barrier

28. Meninges
• Dura mater
• Double-layered external covering
• Periosteum – attached to surface of the skull
• Meningeal layer – outer covering of the brain
• Folds inward in several areas
• Arachnoid layer- Middle layer
• Web-like
• Pia mater- Internal layer
• Clings to the surface of the brain

29. Cerebrospinal Fluid
• Similar to blood plasma composition
• Formed by the choroid plexus
• Forms a watery cushion to protect the
brain
• Circulated in arachnoid space,
ventricles, and central canal of the
spinal cord

30. Ventricles and Location of
the Cerebrospinal Fluid

31. Blood Brain Barrier
• Includes the least permeable capillaries
of the body
• Excludes many potentially harmful
substances
• Useless against some substances
• Fats and fat soluble molecules
• Respiratory gases
• Alcohol
• Nicotine
• Anesthesia

32. Spinal Cord
• Extends from the medulla oblongata
to the region of T12
• Below T12 is the cauda equina (a
collection of spinal nerves)
• Enlargements occur in the cervical
and lumbar regions
 Extends from the foramen
magnum of the skull to the first or
second lumbar vertebra
 31 pairs of spinal nerves arise
from the spinal cord
 Cauda equina is a collection of
spinal nerves at the inferior end

33. Spinal Cord Anatomy
 Internal gray matter is mostly cell bodies
 Dorsal (posterior) horns
 Anterior (ventral) horns
 Gray matter surrounds the central canal
 Central canal is filled with cerebrospinal
fluid
 Exterior white mater—conduction tracts
 Dorsal, lateral, ventral columns

34. Spinal Cord Anatomy
 Meninges cover the spinal cord
 Spinal nerves leave at the level of each vertebrae
 Dorsal root
 Associated with the dorsal root ganglia—
collections of cell bodies outside the
central nervous system
 Ventral root
 Contains axons

35. Spinal Cord Anatomy

36. Peripheral Nervous System
• Nerves and ganglia outside the central nervous
system
• Nerve = bundle of neuron fibers
• Neuron fibers are bundled by connective tissue
• The PNS functions to convey impulses to and
from the brain or spinal cord.
• The nerves of the PNS are classified as
• cranial nerves or
• spinal nerves

37. Structure of a Nerve
• Endoneurium
surrounds each fiber
• Groups of fibers are
bound into fascicles
by perineurium
• Fascicles are bound
together by
epineurium

38. Classification of Nerves
• Mixed nerves – both sensory and motor
fibers
• Afferent (sensory) nerves – carry
impulses toward the CNS
• Efferent (motor) nerves – carry impulses
away from the CNS

39. • Cranial nerves
– 12 pairs of nerves that mostly serve the head and
neck
– The cranial nerves are designated by roman
numerals
– Their names indicate the structures innervated or
the principal functions of the nerves
– Only the pair of vagus nerves extend to thoracic
and abdominal cavities
39

40. I. Olfactory Nerve
.Sense of smell
.Damage causes impaired sense of smell
40

41. II. Optic Nerve
-Provides vision
-Damage causes blindness in visual field
41

42. III. Oculomotor Nerve
Eye movement, opening of eyelid, constriction of
pupil, focusing
Damage causes drooping eyelid, dilated pupil, double
vision, difficulty focusing and inability to move eye in
certain directions 42

43. IV. Trochlear Nerve
-Eye movement (superior oblique muscle)
-Damage causes double vision and inability
to rotate eye inferolaterally
43

44. V. Trigeminal Nerve
..Sensory to face
(touch, pain and
temperature) and
muscles of
mastication
..Damage
produces loss of
sensation and
impaired
chewing
44

45. VI. Abducens Nerve
-Provides eye movement (lateral rectus m.)
-Damage results in inability to rotate eye
laterally and at rest eye rotates medially
45

46. VII. Facial Nerve
• Motor - facial
expressions; salivary
glands and tear, nasal
and palatine glands
• Sensory - taste on
anterior 2/3’s of
tongue
• Damage produces
sagging facial
muscles and
disturbed sense of
taste (no sweet and
salty)

47. VIII. Vestibulocochlear Nerve
-Provides hearing and sense of balance
-Damage produces deafness, dizziness,
nausea, loss of balance and nystagmus 47

48. IX. Glossopharyngeal Nerve
• Swallowing,
salivation, gagging
and respiration
• Sensations from
posterior 1/3 of
tongue
• Damage results in
loss of bitter and
sour taste and
impaired
swallowing

49. X. Vagus Nerve
• Swallowing,
speech, regulation
of viscera
• Damage causes
hoarseness or loss
of voice, impaired
swallowing and
fatal if both are cut

50. XI. Accessory Nerve
• Swallowing,
head, neck and
shoulder
movement
– damage causes
impaired head,
neck, shoulder
movement;
head turns
towards injured
side

51. XII. Hypoglossal Nerve
• Tongue movements
for speech, food
manipulation and
swallowing
– if both are
damaged – can’t
protrude tongue
– if one side is
damaged – tongue
deviates towards
injured side

52. Spinal Nerves
• There is a
pair of spinal
nerves at the
level of each
vertebrae.

53. Autonomic Nervous System
• The involuntary branch of the nervous
system
• Consists of only motor nerves
• Divided into two divisions
• Sympathetic division
• Parasympathetic division

54. Autonomic Functioning
• Sympathetic – “fight-or-flight”
• Response to unusual stimulus
• Takes over to increase activities
• Remember as the “E” division = exercise,
excitement, emergency, and embarrassment

55. Autonomic Functioning
• Parasympathetic – housekeeping
activites
• Conserves energy
• Maintains daily necessary body functions
• Remember as the “D” division - digestion,
defecation, and diuresis