1. Cranial Nerves & Brain dissection
Lab 19
Cranial Nerves &
Brain dissection

2. Today Intro to the brain The cranial nerves
Human and sheep brain anatomy
Get to work
CLEAN UP

3. Practical 4
Thurs 12/6
50 points: about half brain models and half book figures (with a few fresh brains too)
Know:
List of brain parts on objectives (names and locations only; you will need to know functions on the exam though)
The 12 cranial nerves: names, locations, & functions (shown in blue in this lecture)

4. Brief intro to the brain
External structures
cerebral hemispheres
cerebrum
midbrain
cerebellum
pons
medulla
central sulcus
precentral gyrus
postcentral gyrus
lateral sulcus
longitudinal fissure
frontal lobe
parietal lobe
occipital lobe
temporal lobe
Internal structures:
corpus callosum
basal ganglia (nucleus)
Caudate
Putamen
internal capsule
thalamus
hypothalamus
hippocampus
amygdala
pineal gland
pituitary gland
reticular formation
fornix
substantia nigra
cingulate gyrus
optic chiasm
lateral ventricles
mammilary bodies
corpora quadrigemina
inferior colliculus
superior colliculus

5. Major Regions and Landmarks
Figure 14–1

6. Regions of the Adult Brain
Telencephalon (cerebrum) – cortex, white matter, and basal nuclei
Diencephalon – thalamus, hypothalamus, and epithalamus
Mesencephalon –midbrain (brain stem)
Metencephalon – pons (brain stem), cerebellum
Myelencephalon – medulla oblongata (brain stem)

7. Some terms nucleus: collection of neuron cell bodies in the CNS
tract: collection of axons in the CNS
ganglia: collection of neuron cell bodies in the PNS
nerve: collection of axons in the PNS
Cranial nerves
Spinal nerves

8. Tour through the brain
From caudal/inferior to rostral/superior

9. The Brain Stem Includes: mesencephalon (midbrain) pons
medulla oblongata
Note: some consider the diencephalon part of the brain stem as well

10. Anatomy: Brain stem
Most cranial nerves are located in the brain stem

11. Posterior view

12. Medulla Oblongata

13. Cerebellum

14. Cerebellum – side view

15. Mesencephalon

16. Mesencephalon

17. The Diencephalon Thalamus Hypothalamus Pineal gland Pituitary gland
Figure 14–5a

18. Telencephalon Cerebrum Basal nuclei
Largest part of brain, includes huge wrinkly cerebral hemispheres
Basal nuclei

19. The Basal Nuclei (Ganglia)
Figure 14–14b, c

20. Lateral Ventricles

21. The Limbic System
Figure 14–11a

22. The Cerebral Cortex 4 Lobes: frontal parietal temporal occipital
Figure 14–12b

23. Cerebral Cortex landmarks
Lateral sulcus
Longitudinal fissure
Central sulcus
Precentral gyrus (primary motor)
Postcentral gyrus (primary sensory)
Association areas are for integrating information

24. Motor and Sensory Areas of the Cortex
Central sulcus separates motor and sensory areas
Figure 14–15a

25. Cranial Nerves

26. Cranial Nerves
12 pairs connected to brain
Figure 14–18

27. Cranial Nerves
Figure 13.5a

28. Cranial Nerves Twelve pairs of cranial nerves arise from the brain
They have sensory, motor, or both sensory and motor functions (mixed)
Each nerve is identified by a number (I through XII) and a name
Four cranial nerves carry parasympathetic fibers that serve muscles and glands

29. 3 main types of Cranial Nerves
Sensory nerves:
carry somatic (touch) or special sensory information
Motor nerves:
axons of somatic motor neurons
Mixed nerves:
mixture of motor and sensory fibers

30. Cranial Nerves
I – Olfactory
II – Optic
III – Occulomotor
IV – Trochlear
V – Trigeminal
VI – Abducens
VII – Facial
VIII – Vestibulococlear
IX – Glossopharyngeal
X – Vagus
XI – Accessory
XII – Hypoglossal
On Occasion, Our Trusty Truck Acts Funny; Very Good Vehicle Anyhow

31. Summary of Function of Cranial Nerves
Figure 13.5b

32. You need to learn:
Names
Numbers
Locations
Main functions (in blue)

33. Anterior View
Lateral view

34. The Olfactory Nerves (I)
Figure 14–19

35. Olfactory Nerves (I) Don’t originate or enter brainstem
Primary function:
special sensory (smell)
Arises from the olfactory epithelium
Passes through the cribriform plate of the ethmoid bone
Fibers run through the olfactory bulb and terminate in the primary olfactory cortex
Functions solely by carrying afferent impulses for the sense of smell

36. The Optic Nerves (II)
Figure 14–20

37. Optic Nerves (II) Enter diencephalon Primary function:
special sensory (vision)
Arises from the retina of the eye
Optic nerves pass through the optic canals and converge at the optic chiasm
They continue to the thalamus (diencephalon) where they synapse

38. CNs III,IV,VI
All motor only
All innervate eye muscles

39. The Oculomotor Nerves (III)
Figure 14–21

40. Oculomotor Nerves (III)
Primary function:
motor (many eyeball movements, pupil constriction, controlling lens shape)
Origin:
mesencephalon
Destination:
somatic motor: 4 extrinsic eye muscles:
visceral motor: parasympathetic NS cell bodies in the ciliary ganglion, got to intrinsic eye muscles

41. The Trochlear Nerves (IV)
Figure 14–21

42. Trochlear Nerves (IV) Smallest CN Primary function: Origin:
motor (eye movement: looking down)
Origin:
mesencephalon
Destination:
superior oblique muscle (that’s it!)

43. The Abducens Nerves (VI)
Figure 14–21

44. The Abducens Nerves (VI)
Primary function:
motor (eye movement: looking to the side)
Origin:
pons
Destination:
lateral rectus muscle (just one eye muscle)

45. The Trigeminal Nerves (V)
Figure 14–22

46. Trigeminal Nerves (V) Largest CN – it’s huge! Primary function:
mixed (sensory and motor) to face
All sensory from face; motor for chewing
Three branches
ophthalmic branch (sensory)
maxillary branch (sensory)
mandibular branch (sensory and motor)
Destinations
sensory: sensory nuclei in pons
motor: muscles of mastication

47. The Facial Nerves (VII)
Figure 14–23

48. Facial Nerves (VII) Primary function: sensory: motor: **Bell’s Palsy
mixed (sensory and motor) to face
Motor to facial muscles; taste
sensory:
taste receptors on anterior 2/3 of tongue
motor:
Facial muscles, parasympathetic to lacrimal and salivary glands
**Bell’s Palsy

49. The Vestibulocochlear Nerves (VIII)
Figure 14–24

50. Vestibulocochlear Nerves (VIII)
Primary function: special sensory
vestibular branch:
balance and equilibrium
cochlear branch:
hearing
Origin: receptors of inner ear
Destination: nuclei in both pons and medulla

51. The Glossopharyngeal Nerves (IX)
Figure 14–25

52. Glossopharyngeal Nerves (IX)
Primary function:
mixed (sensory and motor) to head and neck
Mainly: swallowing, some salivary gland function
Origins:
sensory:
posterior 1/3 of tongue
part of pharynx and palate
carotid bodies (blood pressure/CO2 sensors)
motor:
motor nuclei of medulla

53. The Vagus Nerves (X)
Figure 14–26

54. Vagus Nerves (X) Primary function:
mixed (sensory and motor) of thorax and abdomen
Only CN that extends beyond head and neck
“Mr. parasympathetic” motor to para-NS
Runs outside of spinal cord to visceral organs
Originates in medulla

55. The Accessory Nerves (XI)
Figure 14–27

56. Accessory Nerves (XI) Primary function: Origin: Two roots:
motor to muscles of neck and upper back
Origin:
motor nuclei of spinal cord and medulla oblongata
Two roots:
The spinal root passes upward into the cranium via the foramen magnum
The accessory nerve leaves the cranium via the jugular foramen
Destinations:
voluntary muscles of palate, pharynx, and larynx
sternocleidomastoid and trapezius muscles

57. The Hypoglossal Nerves (XII)
Figure 14–27

58. Hypoglossal Nerves (XII)
Primary function:
motor (tongue movements)
Origin:
motor nuclei of medulla
Destination:
muscles of tongue which aid in speech

59. Gross Anatomy of the human brain

60. Human brain

61. Midsagittal

62. Coronal

63. InferiorView

64. Sheep brain

65. Sheep brain inferior view

66. Midsagittal

67. Anterior View

68. Follow instructions in lab book
look at the meninges
start by examining the external brain
Ventral surface first, then dorsal
then look internally without cutting (fig 19.12)
cut it midsagittally to see inside
Try a coronal cut to see what you can find
Review Sheet due next Thursday

69. To find: Meninges Cranial nerves I – XII (?)
fissures and sulci on surface, lobes
pineal gland
corpora quadrigemina (part of midbrain)
midbrain
pons
medulla
cerebellum
mamillary body (just one)
optic chiasm
corpus callosum (central)
fornix
lateral ventricles
choroid plexus (inside ventricles)
hypothalmus
“pituitatry gland” (hangs off hypothalamus
arbor vitae (inside cerebellum)