MEDULLA
[Figure]: "Schematic of the Medulla"
A. Pyramids

1. Motor Fibers going to Corticothalamic Tract
2. Ipsilateral at this point, will decussate at medullo-spinal junction

B. Inferior Olive

1. Cerebellar afferent system
2. Lesions may occur in degerative conditions
3. Example is olivopontocerebellar atrophy

C. Medial Lemniscus

1. Continuation of dorsal column system, already crossed (at Nucleus gracilis and cuneatus)
2. Fibers of the second order neurons are en route to Ventral Posterolateral Thalamus

D. Spinal Nucleus and Tract of Cranial Nerve (CN) V

1. Pain and temperature sensation to the face, ipsilateral side
2. Complex path

E. Nucleus Ambiguous (NA)

1. Motor fibers to CN IX, X, and XI (recurrent laryngeal nerve)
2. Controls muscles of pharynx and larynx

F. Nucleus and Tractus Solitarius

1. Information from CN X about viscera
2. Taste inputs from CN VII (anterior 2/3) and IX (posterior)

G. Hypoglossal (CN XII) Nucleus

1. Motor neurons for tongue
2. Lesions will cause tongue to deviate to the ipsilateral side

H. Dorsal Motor Vagus

1. Main Parasympathetic Nucleus
2. Ipsilateral input to glands, heart, bronchioles, stomach, proximal bowel

I. Vestibular Nucleus

1. Balance System (CN VIII) - lesions cause ipsilateral deviation

J. Reticular Formation

1. Influences many basic functions
2. Respiration
3. Heart Rate
4. Blood Pressure
5. Sympathetic Outflow

K. Locus Ceruleus

1. Norepinephrine outflow

PONS
[Figure]: "Schematic of the Pons"

A. Pontine Nuclei

1. Major relay stations between Cerebral Cortex and Cerebellum
2. Fibers from Cerebrum descend from Peduncles into Pontine Nuclei

B. Medial Lemniscus

1. Continuation of ascending (sensory fibers), already crossed (at N. gracilis and cuneatus)
2. Fibers of the 2nd order neurons are en route to Ventral Posterolateral Thalamus (VPT)
3. The VPT routes form the spinothalamic tracts

C. Cranial Nuclei

1. Facial (CN VII) Nucleus [1]
   1. Motor neurons for most facial muscles
   2. Motor nucleus in caudal pons
   3. Peripheral fibers of nervus intermedius portion of CN VII initiate salivary, lacrimal and mucous secretion
   4. Sensory cells located in geniculate ganglion continue distally as chorda tympani nerve
   5. Chorda tympani nerve also carries taste fibers from nucleus of fascia solitarius
2. Cochlear (CN VIII) Nucleus - hearing and balance
3. Main Sensory and Motor Nucleus of CN V (Trigeminal)
   1. Main sensory receive afferent inputs
   2. CN V motor controls some of the jaw muscles (see below)
4. Abducens (CN VI) Nucleus - lateral rectus muscle of the eye

D. Summary of CN V Nuclei

1. Spinal V for Pain and Temperature (compre with Spinothalamic)
2. Main Sensory V for Discriminative Touch (compare with Dorsal Columns)
3. Motor V for jaw power (compare with Corticospinal)
4. Mesencephalic V for unconsious joint and jaw muscle afferents (compare with cerebellum)

E. Medial Longitudinal Fasciculus

1. Sight fine tuning
2. Lateral gaze, connection between VI (ipsilateral) and III (contralateral)

F. Cerebellar Peduncles

1. Inferior - ascending phase of spinocerebellar tracts
2. Middle - principal input from cerebrum to cerebellum
3. Superior - found in Midbrain, input from cerebellum

MIDBRAIN
[Figure]: "Schematic of the Midbrain"

A. Basis Pedunculi (Cerebral Peduncles)

1. Corticospinal Tract fibers from ipsilateral hemisphere
2. Descending Corticopontine and Corticomedullary Fibers

B. Substantia Nigra

1. Dopaminergic Neurons ascending to Corpus Striatum and cerebral cortex (mainly anterior)
2. Destroyed in Parkinson's Disease

C. Red Nucleus

1. Part of extrapyramidal motor system
2. Input from cerebellum via superior crebellar peduncle
3. Rubrospinal tract
4. Influences flexor tone (proximal arm muscles)

D. Superior Cerebellar Peduncle

1. Bulk of Cerebellar Outflow
2. Fibers cross in prominent decussation then travel to Thalamus (Ventrolateral Nucleus)
3. Also receives fibers from Ventrolateral Spinocerebellar Tract
4. Lesions cause profound intention and postural tremor

E. Oculomotor Nucleus (CN III)

1. Controls 4 muscles of vision
   1. Medial Rectus
   2. Inferior Rectus
   3. Superior Rectus
   4. Inferior Oblique
2. Note that CN VI controls lateral rectus and CN IV controls suprior oblique

F. Edinger-Wetphal Nucleus

1. Parasympathetic control for eye
2. Focus and pupillary control

G. Pretectum
H. Periaquaductal Gray

1. Reticular Formation activating system
2. Lesions here may cause profound coma
3. CN III nucleus is in this region

I. Colliculi

1. Receive contrlateral inputs
2. Superior Colliculi: Primitive processing centers for visual information
3. Inferior Colliculi: Primitive processing centers for auditory information

A. Neocerebellum

1. Lateral Hemispheres
   1. Intention Tremor
   2. Dysdiadochokinesis
   3. Dysmetric Saccades
   4. Dysarthria
   5. Mild hypotonia
   6. Explosive Speech
2. Cerebellar Nuclei

B. Paleocerebellum

1. Anterior and Vermis
2. Trucal Instability
3. Wide Based Gait

C. Archecerebellum

1. Flocculus and Nodulus (Posterior)
2. Eye movement problems
3. Vestibular problems

THALAMUS
[Figure]: "Schematic of the Corpus Striatum"

A. Overview

1. Relay system for all sensory and motor system inputs to neocortex (except smell)
2. Certain forms of perception (such as pain) may be mediated here

B. Ventroposterolateral and Ventroposteromedial Thalamus

1. Somatosensory inputs from:
   1. Spinothalamic tract
   2. Dorsal columns via medial lemniscus

C. Medial and Lateral Geniculates

1. Medial - Audition
2. Lateral - Vision

D. Ventralis Lateralis

1. Most important motor nucleus of thalamus
2. Fibers from:
   1. Cerebellum
   2. Basal Ganglia
   3. Motor cortex
3. Output to motor cortex

E. Anterior Nuclei (Association)

1. Important relays linking limbic system to cortex
2. Receive fibers from:
   1. Fornix (outflow of hippocampus)
   2. Hypothalamus via mamilllary bodies / tracts
   3. Called Circuit of Papez

F. Reticular Nuclei

1. Intralaminar thalamic nuclei
2. Rostral Extent of reticular formation

G. Basal Ganglia
[Figure]: "Schematic of the Corpus Striatum"

1. Conponents of extrampyramidal motor system
2. Globus Pallidus
3. Corpus Striatum (Caudate + Putamen)
4. Subthalamic Nucleus
5. Fields of Forel

H. Thalamic Lesions

1. Small strokes (forming lacunes)
   1. Diminished pain and temperature sensation
   2. Localized motor deficits
   3. Cortical function is preserved
   4. Usually due to occlusion of deep perforating branch of posterior cerebral artery
2. Thalamic Pain Syndrome of Dejerine-Roussy
   1. Burning pain to Contralateral face and body
   2. Years after onset of thalamic injury
3. Massive hemorrhage
   1. Pretectal region mass effect
   2. Paresis of upgaze and irritative accomodation
   3. Dense sensory deficit
4. Abnormal activity in Parkinson's Disease

A. Constituents

1. Hippocampus
   1. Primary memory processing (recording)
   2. Presence of neural stem cells in dentate gyrus [5]
2. Olfactory Association Cortex
3. Amygdala
4. Anterior Thlamus
5. Cingulate Cortex

B. Amygdala

1. Mediates the four "F's:"
2. Fight
3. Flight
4. Feeding
5. Sex

A. Supraoptic and Paraventricular Nuclei [2]

1. Anterior to thalamus, region above optic chiasm
2. Neurosecretory fibers to posterior pituitary
   1. Supraoptic - ADH (vasopressin)
   2. Paraventricular - Oxytocin
3. ADH
   1. Nonapeptide with arginine in the 8th position
   2. Carrier protein is neurophysin II
   3. Regulates water homeostasis and effects on blood pressure
4. Abnormal ADH Regulation
   1. Increased production: Syndrome of Inappropriate ADH
   2. Decreased production / insensitivity: Diabetes Insipidus
5. Oxytocin
   1. Released from posterior pituitary neurons by suckling response in lactating females
   2. Carrier protein is neurophysin I
   3. Key role in parturition and milk letdown in mammals

B. Specific Areas

1. Anterior
   1. Supraoptic and Paraventricular
   2. Nuclei involved in cooling centers - Cutaneous vasodilation and Sweating
2. Medial - "Satiety Center"
3. Lateral - "Feeding Center"

C. Mammillary Bodies

1. Posterior hypothalamus; many projections from hippocampus via Fornix
2. Deterioration in Wernicke's Encephalopathy (Thiamine Deficiency)

CEREBRAL CORTEX
[Figure]: "Schematic of the Brain"

A. Regions

1. Broca's Area - Speech motor, fluidity
2. Wernicke's Area - Comprehension, repetition, abnormal writing
3. Motor Area
4. Premotor Area
5. Sensory Areas
   1. Parietal - somatosensory
   2. Superior Temporal - auditory
   3. Occipital - visual
6. Frontal Cortex [3]
   1. Association ("filing" function)
   2. Working memory
   3. Episodic memory
7. Cognitive Function [4]
   1. Brain left hemisphere is usually involved in cognitive function
   2. High grade stenosis of Left, but not Right, internal carotid artery associated with ~6X increased risk for cognitive deficits and 2.X risk of congnitive decline

B. Principle White Matter Tracts

1. Corona Radiata (Internal Capsule)
   1. Anterior Radiation - premotor and motor descending to pyramids and cerebellum
   2. Anterior Parietal Radiation - thalamocortical, somatosensory
   3. Auditory Radiation - from lateral geniculate to superior temporal cortex
   4. optic Radiation - from medial geniculate to occipital cortex
2. Corpus Callosum - largest commisure
3. Anterior and POsterior Commissures
4. Optic Chiasm
   1. Neurons travelling from eye come together here (then diverge)
   2. Carries CN II (optic) neurons to vision centers

C. Cerebral Circulation

1. Internal Carotid Arteries
   [Figure]: "Arteries of the Head"
   1. Anterior cerebral artery
   2. Middle cerebral artery - direct continuation of internal carotid artery
   3. Posterior cerebral artery
2. External Carotid Arteries - arteries of the skull and outside the brain
3. Vertebral Arteries
   [Figure]: "Circle of Willis"

D. Ventricles

1. Sites of cerebrospinal fluid (CSF) production, storage and flow
2. Lateral ventricles (2)
   1. Sites of CSF production
   2. Surrounding areas contain critical neurons and precursors
   3. Subventricular zone along lateral wall contains highest levels of neuronal stem cells [5]
   4. Dentate gyrus of hipoocampus also contains white matter
3. Medial ventricle

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References

1. Gilden DH. 2004. NEJM. 351(13):1323
2. Bichet DG. 1998. Am J Med. 105(5):431
3. Budson AE and Price BH. 2005. NEJM. 352(7):692
4. Johnston SC, O'Meara ES, Manolio TA, et al. 2004. Ann Intern Med. 140(4):237
5. Sanai N, Alvarez-Buylia A, Berger MS. 2005. NEJM. 353(8):811