1. The Central Nervous System Part A
Chapter 12
The Central Nervous System Part A

2. Objectives:
• List, label and identify meninges, parts of the brain, match and select from a given list with 100% accuracy • List the functions of the different parts of the brain, match and select from a given list with 100% accuracy • Identify and label gross anatomy and sectional anatomy of the spinal cord • List some of the diagnostic procedures for assessing CNS dysfunction • Write short descriptions explaining the principles of EEG, brain wave patterns, memory, consciousness and their dysfunctions

3. Central Nervous System (CNS)
CNS – composed of:
The brain, and
Spinal cord
Evolutional Cephalization:
involves:
Elaboration of the anterior portion of the CNS
Increase in number of neurons in the head
Highest level is reached in the human brain

4. Embryonic Development
First 26 days of development:
Ectoderm thickens forming neural plate
Neural plate invaginates, forming the neural groove
Neural groove fuses dorsally and forms the neural tube
Neural tube detaches, sinks deeper
Neural tube forms the CNS

5. Primary Brain Vesicles
Anteriorly the neural tube expands and constricts
It forms three primary brain vesicles:
Prosencephalon:
The forebrain
Mesencephalon:
The midbrain
Rhombencephalon:
The hindbrain

6. Secondary Brain Vesicles
In week 5, secondary brain vesicles form:
Forebrain gives rise to:
Telencephalon
Diencephalon
Midbrain remains as:
Mesencephalon
Hindbrain gives rise to:
Metencephalon
Myelencephalon

7. Adult Brain Structures
Fates of the secondary brain vesicles:
Telencephalon :
Cerebrum: cortex, white matter, and basal nuclei
Diencephalon:
Thalamus, hypothalamus, and epithalamus
Retina of the eye
Mesencephalon:
Brain stem: midbrain
Metencephalon:
Brain stem: pons
Cerebellum (not part of brain stem)
Myelencephalon:
Brain stem: medulla oblongata

8. Adult Brain Structures
Figure 12.2c, d

9. Adult Neural Canal Regions
Adult structures derived from the neural canal:
Telencephalon:
Lateral ventricles
Diencephalon:
Third ventricle
Mesencephalon:
Cerebral aqueduct
Metencephalon & myelencephalon:
Fourth ventricle

10. Adult Neural Canal Regions
Figure 12.2c, e

11. The Brain Composed of wrinkled, pinkish gray tissue
Surface anatomy includes:
Cerebral hemispheres
Cerebellum
Brain stem

12. Brain Lobes
Figure 12.6a–b

13. Basic Pattern of the Central Nervous System
Spinal Cord
Central cavity surrounded by a gray matter core
External white matter composed of myelinated fiber tracts
Brain
Similar to spinal cord but with additional areas of gray matter
Cerebrum has grey matter in nuclei and additional gray matter in the cortex
Cerebellum has gray matter in nuclei

14. Ventricles of the Brain
The ventricles are:
Expansions of the lumen of the embryonic neural tube
Continuous with one another & with the central canal of the spinal cord
Lined with ciliated ?????? cells
Filled with cerebrospinal fluid

15. Ventricles of the Brain
The ventricles include:
The lateral ventricles:
Paired C-shaped found in the telencephalon
The third ventricle:
Found in the diencephalon
The fourth ventricle:
found in the hindbrain (metencephalon & myelencephalon) dorsal to the pons

16. Ventricles of the Brain
Figure 12.5

17. Major Lobes, Gyri, and Sulci of the Cerebral Hemisphere
Shallow grooves divide the hemispheres into five lobes:
Frontal
Parietal
Temporal
Occipital
insula
Central sulcus:
Separates the frontal and the parietal lobes

18. Brain Lobes
Figure 12.6a–b

19. Major Lobes, Gyri, and Sulci of the Cerebral Hemisphere
Parieto-occipital sulcus:
Separates the parietal and occipital lobes, (can only be seen medially)
Lateral sulcus:
Separates both the frontal lobes from the temporal lobes
Precentral and postcentral gyri:
Border the central sulcus anteriorly & posteriorly, respectively.

20. Brain Lobes
Figure 12.6a–b

21. Cerebral Hemispheres Superior part of the brain (83% of brain mass)
Contain:
elevated ridges called gyri
shallow grooves called sulci
deep grooves called fissures
Separated into two parts by longitudinal fissure
Separated from cerebellum by transverse fissure
Have three basic regions:
cortex
white matter
basal nuclei

22. Cerebral Cortex The cortex is the superficial gray matter
It accounts for 40% of the brain mass
It enables sensation, communication, memory, understanding, and voluntary movements
Each hemisphere acts contralaterally (controls the opposite side of the body)
Hemispheres are not equal in function
Conscious behavior involves the entire cortex
( No functional area acts alone)

23. Functional Areas of the Cerebral Cortex
The three types of functional areas are:
Motor areas:
Control voluntary movement
Sensory areas:
Conscious awareness of sensation
Association areas:
Integrate diverse information
Note: All neurons in the cortex are interneurons

24. Functional Areas of the Cerebral Cortex
Figure 12.8a

25. Cerebral Cortex: Motor Areas
They control voluntary movements
Lie in the posterior part of the frontal lobe
They include:
Primary (somatic) motor cortex
Premotor cortex
Frontal eye field
Broca’s area

26. Primary Motor Cortex Located: Pyramidal cells: Allows:
In the precentral gyrus
Pyramidal cells:
Large neurons called pyramidal cells
Their axons:
Descend to the spinal cord
Make up the pyramidal (cortico-spinal) tracts
Allows:
Conscious control of the precise voluntary movements of skeletal muscles

27. Functional Areas of the Cerebral Cortex
Figure 12.8a

28. Premotor Cortex Located: Controls motor skills that are: Involved in:
Just anterior to precentral gyrus
Controls motor skills that are:
Learned
Repetitious, or
patterned
Involved in:
The planning of movements

29. Functional Areas of the Cerebral Cortex
Figure 12.8a

30. Broca’s Area Broca’s area
Located anteroinferiorly to the premotor area
Present in one hemisphere (usually the left)
A motor speech area (directs tongue muscles)
Is active as one prepares to speak

31. Functional Areas of the Cerebral Cortex
Figure 12.8a

32. Frontal Eye Field Frontal eye field Located: Controls:
Anterior to the premotor cortex
Superior to Broca’s area
Controls:
Voluntary eye movement

33. Functional Areas of the Cerebral Cortex
Figure 12.8a

34. Cerebral Cortex: Sensory Areas
Concerned with conscious awareness of sensation
Found in insular, parietal, occipital, & temporal lobes
They include:
Primary somatosensory cortex
Somatosensory association cortex
Visual and auditory areas
Olfactory (smell)
gustatory (taste)
vestibular (equilibrium) cortices

35. Functional Areas of the Cerebral Cortex
Figure 12.8a

36. Lateralization of Cortical Function
Each hemisphere has abilities not shared with its partner
Cerebral dominance:
Designates the hemisphere dominant for language
Left hemisphere:
Usually controls language, math, and logic i.e. dominant hemisphere
Right hemisphere
Controls conceptual skills, emotion, and artistic skills

37. Which side dominates
Most right handed people (90%) use the left side hemisphere most
The other 10% are either reversed or use both sides equally
Some left handed people are ambidextrous (equal hemisphere use),
This was once thought to result in dyslexia (hemisphere confusion)

38. Cerebral White Matter
Consists of myelinated fibers bundled into large tracts
Responsible for communication between:
Various cerebral areas
The cerebral cortex & the lower CNS centers

39. Cerebral White Matter Fibers and tracts: They include:
Classified according to the direction they run
They include:
Commissures
Association fibers
Projection fibers

40. Cerebral White Matter Commissures: Association fibers:
Run horizontally
Connect corresponding gray areas of the two hemispheres
Association fibers:
Connect different parts of the same hemi- sphere

41. Cerebral White Matter (cont’d)
Projection fibers:
Run vertically
Some enter hemispheres from the lower brain or cord centers
Others leave the cortex to the lower centers
Tie the cortex to:
The rest of the nervous system
The body’s receptors & effectors

42. Fiber Tracts in White Matter
Figure 12.10a

43. Fiber Tracts in White Matter
Figure 12.10b

44. Fiber Tracts in White Matter
Figure 12.10b

45. Basal Nuclei Include: Basal nuclei are: Found:
Masses of gray (cortical) matter
Found:
Deep within the cerebral white matter
Include:
The caudate, putamen, & globus pallidus
Together the putamen & globus pallidus are called lentiform (lens-shaped)
Collectively, the lentiform & caudate are called corpus striatum
Striation appearance is due to internal capsule running through them

46. Break Slide Biol2401._______ Monday, April 01, ’13