1. Central Nervous System:
Brain
Spinal cord

2. The Brain Performs the most complex neural functions Intelligence
Consciousness
Memory
Sensory-motor integration
Involved in innervation of the head

3. Organization of CNS
Centrally located gray matter – neuron cell bodies, interneurons, unmyelinated fibers
Externally located white matter – myelinated fibers
Additional layer of gray matter external to white matter is the Cortex
Formed from neuronal cell bodies migrating externally
Located in cerebrum and cerebellum

4. Basic Parts and Organization of the Brain
Divided into four regions
Cerebral hemispheres - Account for 83% of brain mass
Diencephalon – includes thalamus and hypothalamus
Brain stem - includes midbrain, pons, and medulla
Cerebellum – “little brain”

5. The Cerebral Hemispheres
Frontal section through forebrain
Cerebral cortex
Cerebral white matter
Deep gray matter of the cerebrum (basal ganglia)
Corpus Callosum – commissural fibers (white matter) which connects the two hemispheres

6. The Cerebral Hemispheres
Fissures – deep grooves, which separate major regions of the brain
Transverse fissure – separates cerebrum and cerebellum
Longitudinal fissure – separates cerebral hemispheres
Sulci - grooves on the surface of the cerebral hemispheres
Gyri - twisted ridges between sulci
Prominent gyri and sulci are similar in all people

7. Lobes, sulci, and fissures of the cerebral hemispheres.
Central sulcus
Precentral gyrus
Postcentral gyrus
Frontal lobe
Parietal lobe
Parieto-occipital
sulcus (on medial
surface of
hemisphere)
Lateral sulcus
Occipital lobe
Temporal lobe
Transverse
cerebral fissure
Cerebellum
Pons
(a)
Medulla
oblongata
Spinal cord
Gyrus
Cortex
(gray matter)
Sulcus
White matter
Fissure
(a deep sulcus)

8. The Cerebral Hemispheres
Central sulcus separates frontal and parietal lobes
Bordered by two gyri
Precentral gyrus
Postcentral gyrus
Parieto-occipital sulcus - separates the occipital from the parietal lobe
Lateral sulcus - separates temporal lobe from parietal and frontal lobes
Deeper sulci divide cerebrum into lobes

9. The Cerebral Hemispheres
Lobes are named for the skull bones overlying them
Frontal
Parietal
Temporal
Occipital

10. The Cerebral Cortex Home of our conscious mind
Composed of gray matter - neuronal cell bodies, dendrites, and short axons
Folds in cortex – triples its size
Approximately 40% of brain’s mass

11. The Cerebral Cortex - Functional Areas
Three general kinds of functional areas
Sensory areas
Association areas
Motor areas
Each of the major senses has a specific brain region called a primary sensory cortex
There are also multimodal association areas to process information

12. Functional Areas Of The Cerebral Cortex
Motor areas
Central sulcus
Sensory areas and related
association areas
Primary motor area
Premotor cortex
Primary somatosensory
cortex 3
Frontal
eye field 1 2 6
Somatic
sensation 4 5
Somatosensory
association area
Broca’s area
(outlined by dashes) 7 8
Gustatory cortex
(in insula)
Taste
Prefrontal cortex
Wernicke's area
(outlined by dashes)
Working memory
for spatial tasks 45 43 44 22
Executive area
for task
management 41 42 19 18 22 17
Primary visual
cortex
Working memory
for object-recall
tasks 47 11
Visual
association
area
Vision
Solving complex,
multitask problems
Auditory
association area
Hearing
Primary
auditory cortex
(a)

13. Primary Somatosensory Cortex
Located along the postcentral gyrus
Involved with conscious awareness of general somatic senses
Motor areas
Central sulcus
Sensory areas and related
association areas
Primary motor area
Premotor cortex
Primary somatosensory
cortex 3 1 2
Somatic
sensation 4 5
Somatosensory
association area 7
(a)

14. Primary Visual Cortex On medial part of the occipital lobe
Largest of all sensory areas
Receives visual information that originates on the retina
First of a series of areas processing visual input 19 18 17
Primary visual
cortex
Visual
association
area
Vision
(a)

15. Primary Auditory Cortex
Located at superior edge of the temporal lobe
Conscious awareness of sound
Impulses transmitted to primary auditory cortex
Auditory
association area
Hearing
Primary
auditory cortex
(a)

16. Olfactory Cortex
Olfactory nerves transmit impulses to the olfactory cortex
Provides conscious awareness of smells
Lies on the medial aspect of the temporal lobe 18 18
Visual association
area 34 17 28
Olfactory bulb
Primary
visual cortex
Olfactory tract
Temporal lobe
(b)
Fornix
Primary olfactory
cortex

17. Gustatory Cortex Involved in the conscious awareness of taste stimuli
Located on the “roof” of the lateral sulcus
Gustatory cortex
(in insula)
Taste
(a)

18. Functional Areas Of The Cerebral Cortex
Motor areas
Central sulcus
Sensory areas and related
association areas
Primary motor area
Premotor cortex
Primary somatosensory
cortex 3
Frontal
eye field 1 2 6
Somatic
sensation 4 5
Somatosensory
association area
Broca’s area
(outlined by dashes) 7 8
Gustatory cortex
(in insula)
Taste
Prefrontal cortex
Wernicke's area
(outlined by dashes)
Working memory
for spatial tasks 45 43 44 22
Executive area
for task
management 41 42 19 18 22 17
Primary visual
cortex
Working memory
for object-recall
tasks 47 11
Visual
association
area
Vision
Solving complex,
multitask problems
Auditory
association area
Hearing
Primary
auditory cortex
(a)

19. Motor Areas – Primary Motor Cortex
Controls motor functions
Located in precentral gyrus
Motor areas
Central sulcus
Primary motor area
Premotor cortex
Primary somatosensory
cortex 3
Frontal
eye field 1 2 6 4 5
(a)

20. The Diencephalon
Forms the center core of the forebrain, primarily composed of gray matter
Surrounded by the cerebral hemispheres
Composed of three paired structures: thalamus, hypothalamus, epithalamus
Border the third ventricle

21. The Diencephalon
Forms the center core of the forebrain, primarily composed of gray matter
Surrounded by the cerebral hemispheres
Composed of three paired structures: thalamus, hypothalamus, epithalamus
Border the third ventricle
Corpus callosum
Septum pellucidum
Fornix
Interthalamic
adhesion
(intermediate
mass of
thalamus)
Choroid plexus
Thalamus
(encloses third
ventricle)
Interventricular
foramen
Pineal body/gland
(part of epithalamus)
Corpora
quadrigemina
Hypothalamus
Cerebral
aqueduct
Optic chiasma
Pituitary gland
Midbrain
Arbor vitae
Fourth ventricle
Mammillary body
Choroid plexus
Pons
Cerebellum
Medulla oblongata
Spinal cord

22. The Thalamus Makes up 80% of the diencephalon
Contains approximately a dozen major nuclei
Act as relay stations for incoming sensory message
Every part of brain communicating with cerbral cortex relays signals through thalamic nuclei!
Is the “gateway” to the cerebral cortex

23. The Hypothalamus
Lies between the optic chiasm and the mammillary bodies
Pituitary gland projects inferiorly
Contains approximately a dozen nuclei
Main visceral control center of the body
The master gland’s master!!

24. The Diencephalon – The Hypothalamus
Functions include the following
Control of the ANS
Control of emotional responses
Regulation of body temperature
Regulation of hunger and thirst sensations
Control of behavior
Regulation of sleep-wake cycles
Control of the endocrine system
Formation of memory

25. The Diencephalon – The Epithalamus
Forms part of the “roof” (top) of the third ventricle
Consists of a tiny group of nuclei
Includes the pineal gland (pineal body)
Secretes the hormone melatonin
Under influence of the hypothalamus
Aids in control of circadian rhythm

26. The Brain Stem Several general functions
Produces automatic behaviors necessary for survival
Passageway for all fiber tracts running between the cerebrum and spinal cord
Heavily involved with the innervation of the face and head
10 of the 12 pairs of cranial nerves attach to it

27. The Brain Stem
Includes the midbrain, pons, and medulla oblongata

28. The Brain Stem – The Midbrain
The midbrain processes visual and auditory information and generates involuntary somatic motor responses
Has reticular activing system-arousal of the whole brain
Has nuclei for cranial nerves II and IV
Has ascending and descending tracts

29. The Brain Stem – The Midbrain
Lies between the diencephalon and the pons
Cerebral peduncles located on the ventral surface of the brain, contain pyramidal (corticospinal) tracts
Superior cerebellar peduncles - connect midbrain to the cerebellum

30. The Brain Stem – The Midbrain
Corpora quadrigemina (quad-ri-gemina)
The largest nuclei
Divided into the superior and inferior colliculi
Superior colliculi – nuclei that act in visual reflexes
Inferior colliculi – nuclei that act in reflexive response to sound

31. The Brain Stem – Dorsal View
Figure 13.13c

32. The Brain Stem – The Pons
A “bridge” between the midbrain and medulla oblongata
Pons contains the nuclei of cranial nerves
V – Trigeminal nerve
VI – Abducens nerve
VII – Facial nerve
Motor tracts coming from the cerebral cortex
Pontine nuclei
Connect portions of the cerebral cortex and cerebellum
Send axons to cerebellum through the middle cerebellar peduncles

33. The Brain Stem – The Medulla Oblongata
The core of the medulla contains
Much of the reticular formation
Nuclei then influence autonomic functions
Cardiac center
Vasomotor center
The medullary respiratory center
Centers for hiccupping, sneezing, swallowing, and coughing

34. Functional Brain Systems – The Reticular Formation
Figure 13.29

35. The Brain Stem – The Medulla Oblongata
Most caudal level of the brain stem
Is continuous with the spinal cord
Choroid plexus lies in the roof of the fourth ventricle
Cranial nerves VIII–XII attach to the medulla
External landmarks of medulla
Pyramids of the medulla lie on its ventral surface
Decussation of the pyramids - crossing over of motor tracts
Inferior cerebellar peduncles - fiber tracts connecting medulla and cerebellum

36. The Cerebellum Located dorsal to the pons and medulla
Smoothes and coordinates body movements
Helps maintain equilibrium
Consists of two cerebellar hemispheres
Cortex – gray matter
Arbor vitae - internal white matter
Thick tracts connecting the cerebellum to the brain stem are superior, middle, inferior cerebellar peduncles

37. The Cerebellum Composed of Cortex – gray matter
Arbor vitae - internal white matter
Thick tracts connecting the cerebellum to the brain stem are
Superior cerebellar peduncles
Middle cerebellar peduncles
Inferior cerebellar peduncles
Fibers to and from the cerebellum are ipsilateral -run to and from the same side of the body

38. The Cerebellum
Cerebellum receives information from the cerebral cortex
On equilibrium
On current movements of
Limbs, neck, and trunk

39. Ventricles of the Brain
Expansions of the brain’s central cavity
Filled with cerebrospinal fluid
Lined with ependymal cells
Continuous with each other
Continuous with the central canal of the spinal cord

40. Ventricles of the Brain
Lateral ventricles – located in cerebral hemispheres
Horseshoe-shaped from bending of the cerebral hemispheres
Third ventricle – lies in diencephalon
Connected with lateral ventricles by interventricular foramen
Cerebral aqueduct – connects 3rd and 4th ventricles
Fourth ventricle – lies in hindbrain
Connects to the central canal of the spinal cord

41. Protection of the Brain
The brain is protected from injury by
The skull
Meninges
Cerebrospinal fluid
Blood-brain barrier

42. Cerebrospinal Fluid (CSF)
Formed in choroid plexuses in the brain ventricles
Choroid plexus is
Located in all four ventricles
Composed of ependymal cells and capillaries
Arises from blood ml/day

43. Cerebrospinal Fluid
Fills the hollow cavities of the brain and spinal cord
Provides a liquid cushion for the spinal cord and brain
Other functions
Nourishes brain and spinal cord
Removes wastes
Carries chemical signals between parts of the CNS

44. Cerebrospinal Fluid (CSF)
Figure 13.32b

45. Blood Brain Barrier Extensive impermeable capillaries & sinuses
Perivascular feet of astrocytes cover and wrap around capillaries and promote tight junction formation
Protects brain from hormones & circulating chemicals
Prevents most blood-borne toxins from entering the brain
Not an absolute barrier
Nutrients such as oxygen pass through
Allows alcohol, nicotine, and anesthetics through
Many glucose transporters
Figure 9-6: The blood-brain barrier

46. Meninges Functions of meninges Cover and protect the CNS
Enclose and protect the vessels that supply the CNS
Contain the cerebrospinal fluid between pia and arachnoid maters

47. Meninges Dura Mater Arachnoid Mater Pia Mater
Strongest of the meninges
Composed of two layers: periosteal layer & meningeal layer
Arachnoid Mater
Located beneath the dura mater
Arachnoid villi - Project through the dura mater, allow CSF to pass into the dural blood sinuses
Pia Mater
Delicate connective tissue, clings tightly to the surface of the brain
Follows all convolutions of the cortex

48. The Spinal Cord Functions of the spinal cord
Spinal nerves attach to it
Provides two-way conduction pathway
Major center for reflexes
Location of the spinal cord
Runs through the vertebral canal
Extends from the foramen magnum to the level of the vertebra L1 or L2

49. The Spinal Cord
Cervical and lumbar enlargements - where nerves for upper and lower limbs arise
Conus medullaris - the inferior end of the spinal cord
Cauda equina - collection of spinal nerve roots
Filum terminale - long filament of connective tissue, attaches to the coccyx inferiorly

50. Spinal Cord Segments
Indicate the region of the spinal cord from which spinal nerves emerge
Designated by the spinal nerve that issues from it
T1 is the region where the first thoracic nerve emerges

51. The Spinal Cord Two deep grooves run the length of the cord
Posterior median sulcus
Anterior median fissure

52. White Matter of the Spinal Cord
White columns
Dorsal (posterior) funiculus
Ventral (anterior) funiculus
Lateral funiculus
Composed of myelinated axons
Allow communication between spinal cord and brain

53. White Matter of the Spinal Cord
Fibers classified by type
Ascending fibers - afferent (sensory)
Descending fibers – efferent (motor)
Commisural fibers

54. Major Fiber Tracts in White Matter of the Spinal Cord
Figure 13.34

55. Gray Matter of the Spinal Cord
Shaped like the letter “H”
Gray commissure – contains the central canal
Dorsal horns consist of interneurons
Ventral and lateral horns contain cell bodies of motor neurons

56. Organization of the Gray Matter of the Spinal Cord
Divided according to somatic and visceral regions
SS – somatic sensory
VS – visceral sensory
VM – visceral motor
SM – somatic motor

57. Protection of the Spinal Cord
Protected by vertebrae, meninges, and CSF
Meninges
Dura mater – a single layer surrounding spinal cord
Arachnoid mater – lies deep to the dura mater
Pia mater – innermost layer, delicate layer of connective tissue

58. Ascending Pathways Conduct general somatic sensory impulses
Chains of neurons composed of
First-, second-, and third-order neurons
Four main ascending pathways
Dorsal column pathway
Spinothalamic pathway
Posterior spinocerebellar pathway
Anterior spinocerebellar pathway

59. Descending Pathways Most motor pathways
Decussate at some point along their course
Consist of a chain of two or three neurons
Tracts arranged according to the body region they supply
All pathways are paired - one of each on each side of the body
Deliver motor instructions from the brain to the spinal cord
Divided into two groups
Pyramidal (corticospinal) tracts
Other motor pathways
Tectospinal tracts
Vestibulospinal tract
Rubrospinal tract
Reticulospinal tract