Anatomy of the Brain and Cranial Nerves

1

The Nervous System can be divided in:



Central Nervous System (CNS)

 Brain and Spinal Cord 

Peripheral Nervous System (PNS)

 Cranial and spinal nerves, ganglia, sensory receptors 2

Division of the Peripheral Nervous System



Sensory

or

afferent

 Somatic  Visceral 

Motor

or

efferent

 Somatic - voluntary  Visceral or Autonomic Nervous System (ANS) - involuntary  Sympathetic  Parasympathetic 3

Major regions and landmarks

 Six regions in the adult brain  Cerebrum  Diencephalon  Mesencephalon  Pons  Cerebellum  Medulla oblongata  Brain contains extensive areas of neural cortex  Layer of gray matter on the surface of the cerebellum and cerebrum 4

The Cerebrum

5

The cerebral hemispheres

 Surface contains

gyri , sulci , fissures



Fissures



Longitudinal fissure

separates two cerebral hemispheres 

Transverse fissure

separates cerebellum from cerebrum 6

The Cerebrum

7

The cerebral hemispheres



Sulci

 Parieto-occipital sulcus separates parietal from occipital lobe  Lateral sulcus separates temporal from parietal lobe  Central sulcus separates frontal and parietal lobe 8

The cerebral hemispheres



Gyri

 Precentral gyrus  Poscentral gyrus 9

The cerebral lobes



Frontal

 Precentral gyrus  Primary motor area – conscious control of voluntary movements.  Premotor cortex – memory bank for skilled motor activities or of patterned and repetitious nature.  Broca’s area  Located on the left hemisphere. Controls speech.

10

The cerebral lobes

 Prefrontal cortex – responsible for personality, cognition, intellect. Lesion cause mental and personality disorder 

Parietal

 Primary Somatosensory Area – touch, pressure, temperature, vibration, and pain from body wall  Somatosensory association area – interprets stimulus sent by the above area. Ex: recognizes objects by touch.

11

The cerebral lobes



Temporal

 Primary Auditory area – temporal lobe.  Primary association auditory area – interprets the sound heard by above area  Wernicke’s area – only on left hemisphere, between parietal and temporal lobes. Area responsible for understanding spoken language  Olfactory area –uncus. Smell area.

12

The cerebral lobes



Occipital

 Primary visual area – perception of light  Visual association area – interprets the images seen on the area above 

Insula

 Gustatory cortex 13

Cerebral hemispheres - internal structures

 Gray matter  Cell bodies of the neurons  Dendrites  Small unmyelinated axons  Neuroglias 14

Cerebral hemispheres - internal structures

 White matter  Tracts  Association – connects 2 areas of the same hemisphere  Projection – connects upper and lower brain. Ex: internal capsule  Commissure – connects the 2 hemispheres. 15

Tracts

16

Sagittal Section

17

Cerebral hemispheres - internal structures



Corpus callosum

 Connects the 2 hemispheres 

Fornix

 Connects limbic system areas 

Septum pellucidum

 Separates the 2 lateral ventricles 18

Cerebral hemispheres - internal structures



Basal Nuclei

– regulation of voluntary motor activities. Allows smooth movements.

 Caudate Nucleus  Putamen  Globus pallidus 19

The Diencephalon

20

21

22

Diencephalon: external view

 Olfactory tract  Olfactory bulb  Optic nerve  Chiasma optic  Pituitary gland or hypophysis  Mammilary bodies – relay for olfaction 23

The diencephalon is composed of

 Epithalamus  Hypothalamus  Thalamus 24

Sagittal Section

25 Figure 14.12b

The Epithalamus

 Roof of the third ventricle  Contains

choroid plexus

 Contains

pineal gland

 Regulates sleep-awake cycle 26

The thalamus

 Relay area for impulses  Two large lobes of gray matter  Interthalamic adhesion or intermediate mass  27

The hypothalamus

 Autonomic center for regulation of body temperature, water balance, etc  Secretes hormones  Mammilary bodies – relay station for olfaction  Pituitary glands – secretes hormones  Optic chiasm 28

The Brain Stem



Midbrain

 Cerebral Aqueduct – connects third and forth ventricles  Cerebral peduncles – connects pons to cerebrum  Corpora quadrigemina  Superior colliculi – visual reflex center  Inferior colliculi – auditory reflex center 29

The Brain Stem



Pons

 Consists of tracts and nuclei  Connects brain to lower CNS •

Medulla Oblongata

• Tracts • Decussation of the pyramids • Autonomic reflex centers – heart rate, blood pressure, vomiting, swallowing, respiratory rhythm • Olives 30

PART 2

31

Cerebellum

 Two hemispheres connected by the vermis  Arbor vitae – white matter  Cortex of gray matter 32

The Cerebellum

33

The Cerebellum

34

The cranial meninges



Dura mater

 Falx cerebri-formed by dura mater that dips into the longitudinal fissure and separates the 2 hemispheres  Falx cerebelli – separate the two cerebellar hemispheres 35

The cranial meninges – dura mater

 Superior sagittal Sinus – collects blood from the brain  Tentorium cerebelli – separates the cerebrum from the cerebellum 36

The cranial meninges



Arachnoid

 Subarachnoid space   Arachnoid villi – projections of the mater that protrude through the dura  Filled with CSF For the CSF to drain back to the venous circulation 37

The cranial meninges



Pia mater

 Highly vascular  Covers the entire brain  Meningites 38

The Relationship among the Brain, Cranium, and Meninges

39

Ventricles of the brain

 Filled with cerebrospinal fluid (CSF) 

Lateral ventricles

 Septum pellucidum  Interventricular foramina or foramen of Monro 40

Ventricles of the brain



Third ventricle

 Cerebral aqueduct 

Forth ventricle

 3 Apertures 41

Ventricles of the Brain

42

Cerebrospinal fluid (CSF)

 CSF cushions delicate neural structures  Supports the brain  Pathway of CSF  Produced at the

Choroid plexus

 Travels through the apertures on the 4 th ventricle to the subarachnoid space  Diffuses across the arachnoid villus (granulation) into the superior sagittal sinus 43

The Circulation of CSF

44

Cranial Nerves

 12 pairs of cranial nerves  To help to remember  “

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O

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O

ccasionally

T

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T

rigonometry

A

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F

ells

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loomy

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ague

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ypoactive ” 45

The Cranial Nerves PLAY

46

Cranial Nerves

I Number II III IV V Name Major Functions Olfactory (sens) Smell Optic (sens) Oculomotor (mot) Trochlear (mot) Vision Eye movement Eye movement Trigeminal (mix) Chewing muscles, head and face sensation 47

VI

Cranial nerves

Abducens (mot) VII VIII Facial (mix) Vestibulocochlear (sen) Eye movement Face expression, taste Vestibular: posture and balance Cochlear: hearing 48

IX X XI

Cranial Nerves

XII Glossopharingeal (mix) Vagus (mix) Accessory (mot) Hypoglossal (mot) Swallowing, taste, general sensation for pharynx Visceral muscle movement and taste sensation Swallowing, and head movement Movement of tongue for speaking, swallowing and mixing food 49

Brain Dissection 

Whole Brain

 Pia-Arachnoid  Gyrus  Sulcus  Fissure  Transverse  Longitudinal  Cerebrum 50

Brain Dissection  Pons  Medulla Oblongata  Cerebellum  Cranial nerves:  I (bulb, tract)  II (nerve, chiasma)  III 51

Brain Dissection  Colliculi  Superior  Inferior  Pineal Gland 52

Brain Dissection 

Sagittal Cut

 Diencephalon  Epithalamus  Thalamus  Hypothalamus  Ventricles  Lateral, third, forth 53

Brain Dissection  Septum pellucidum  Corpus callosum  Fornix  Arbor vitae (cerebellum) 54