Nervous System

Neurotransmitters

Neurotransmitter Location Precursor Metabolites
Acetylcholine Basal nucleus of Meynert - Acetate & Choline
Dopamine Ventral tegmentum
Substantia nigra
Tyrosine Homovanillic acid (HVA)
Norepinephrine Nucleus ceruleus Tyrosine Vanillylmandelic acid (VMA)
Epinephrine Adrenal medulla Tyrosine Vanillylmandelic acid (VMA)
Serotonin Raphe nucleus Tryptophan 5-hydroxyindoleacetic acid (5-HIAA)
Histamine - Histidine -
Glutamate - Glutamate -
GABA Nucleus accumbens Glutamate -
Glycine - Glycine -
Opioid - - -

Cerebral Cortex

Layers

  • Molecular layer
  • External granular layer
  • External pyramidal layer
  • Internal granular layer
  • Internal pyramidal layer
  • Multiform layer

Cells

  • Horizontal [Cajal] cell
  • Granular cell
  • Pyramidal cella
  • Fusiform cell
  • Martinotti cell

Cerebral Medulla

Projections

  • Corona radiata
  • Internal capsule

Associations

  • Uncinate
  • Superior longitudinal
  • Inferior longitudinal
  • Superior occipitofrontal
  • Inferior occipitofrontal

Commissures

  • Fornix commissure
  • Anterior commissure
  • Corpus callosum

Thalamus

Nucleus Function
Lateral geniculate nucleus (LGN) Vision
Medial geniculate nucleus (MGN) Audition
Ventral anterior (VA)
Ventral lateral (VL)
Motion
Ventral posterolateral (VPL) Sensation below the neck
Ventral posteromedial (VPM) Sensation above the neck

Hypothalamus

Nucleus Function
Lateral Hunger
Ventromedial Satiety
Anterior Parasympathetic
Posterior Sympathetic
Suprachiasmatic Circadian rhythm
Supraoptic Vasopressin
Paraventricular Oxytocin

Cerebellum

Layers

Structure Input Output
Molecular layer - -
Purkinje layer Cerebellar cortex Cerebellar nuclei
Granular layer Mossy fiber Purkinje cell

Fibers

Structure Input Output
Mossy fiber Cerebrum & Spinal cord Granule cell
Climbing fiber Inferior olivary nucleus Purkinje cell

Cells

Structure Input Output
Basket cell - Purkinje cell
Stellate cell - Purkinje cell
Granule cell Mossy fiber Purkinje cell
Purkinje cell Cerebellar cortex Cerebellar nuclei

Nuclei

Structure Input Output
Dentate nucleus - -
Emboliform nucleus - -
Globose nucleus - -
Fastigial nucleus - -

Cerebellum

Basal Ganglion

  • Striatum: putamen & caudate nucleus
  • Lentiform nucleus: putamen & globus pallidus

Limbic System

  • Fimbria
  • Dentate gyrus
  • Hippocampus
  • Subiculum
  • Cingulate gyrus
  • Uncus
  • Parahippocampus
  • Amygdala

Arterial Supply of the Brain

Dural Venous Sinuses

Ventricular System of the Brain

  • Choroid plexus
  • Lateral ventricles
  • 3rd ventricle
  • Cerebral aqueduct of Sylvius
  • 4th ventricle
  • Central canal
  • Subarachnoid space
  • Arachnoid granulations

Arachnoid Granulation

Groups of Cranial Nerves

Group Cranial Nerves
Pure sensory nerves I & II & VIII
Pure motor nerves III & IV & VI & XI & XII
Mixed sensory & motor nerves
Branchial arch innervation
V & VII & IX & X
Parasympathetic nucleus III & VII & IX & X
Solitary nucleus VII & IX & X
Ambiguous nucleus IX & X & XI

Afferent Pathways

Pathway Function 1° Neuron 2° Neuron 3° Neuron
CN I SVA Olfactory epithelium Olfactory bulb -
CN II SSA Retina Thalamus :: LGN -
CN V GSA Trigeminal ganglion Trigeminal nucleus Thalamus :: VPM
CN VII SVA Geniculate ganglion Solitary nucleus Thalamus
CN VIII SSA Vestibular ganglion Vestibular nucleus Thalamus :: MGN
    Spiral ganglion Cochlear nucleus Thalamus :: MGN
CN IX GVA Superior & Inferior ganglion Solitary nucleus Thalamus
CN X GVA Superior & Inferior ganglion Solitary nucleus Thalamus

Somatic Efferent Pathways

Pyramidal

  • Lateral corticospinal tract
  • Ventral corticospinal tract

Extrapyramidal

  • Tectospinal tract
  • Rubrospinal tract
  • Vestibulospinal tract
  • Reticulospinal tract

Spinal Tracts

Tract Side Functions
Dorsal column Ipsilateral Proprioception
Touch
Pressure
Vibration
Spinothalamic tract Contralateral Pain
Temperature
Lateral corticospinal tract Ipsilateral Motion
Ventral corticospinal tract Contralateral Motion

Pathway of Dorsal Column-Medial Lemniscus System

Neuron Level Side Structure
1° Neuron Periphery Ipsilateral Peripheral nerve
  Periphery Ipsilateral Dorsal root ganglion
  Spinal cord Ipsilateral Dorsal column:
Gracile fasciculus
Cuneate fasciculus
2° Neuron Medulla Ipsilateral Gracile nucleus
Cuneate nucleus
  Medulla Decussation Internal arcuate fiber
  Medulla Contralateral Medial lemniscus
3° Neuron Thalamus Contralateral VPL nucleus
  Cerebrum Contralateral Internal capsule
  Cerebrum Contralateral 1° somatic cortex

Pathway of Anterolateral System

Neuron Level Side Structure
1° Neuron Periphery Ipsilateral Peripheral nerve
  Periphery Ipsilateral Dorsal root ganglion
2° Neuron Spinal cord Ipsilateral Substantia gelatinosa
Nucleus proprius
  Spinal cord Decussation Anterior white commissure
  Spinal cord Contralateral Spinothalamic tract
3° Neuron Thalamus Contralateral VPL nucleus
  Cerebrum Contralateral Internal capsule
  Cerebrum Contralateral 1° somatic cortex

Pathway of Corticospinal Tract

Neuron Level Side Structure
1° Neuron Cerebrum Ipsilateral 1° motor cortex
  Cerebrum Ipsilateral Internal capsule
  Midbrain Ipsilateral Cerebral peduncle
  Medulla Decussation Pyramidal decussation
  Spinal cord Contralateral Lateral corticospinal tract
2° Neuron Spinal cord Contralateral Anterior horn
  Periphery Contralateral Ventral root

Structures in the Spinal Cord

Structure Level
Cervical enlargement C5 ~ T1
Lateral horn :: sympathetic T1 ~ L2
Lumbosacral enlargement L2 ~ S2
Lateral horn :: parasympathetic S2 ~ S4
Cervical plexus C5 ~ T1
Intercostal nerve T1 ~ T11
Lumbosacral plexus T12 ~ S4
Lumbar puncture L3 ~ L5

Afferent Neurons

Neuron Fiber Sensation
I - Proprioception
II A-β Touch
Pressure
Stretch
Vibration
III A-δ Sharp pain
Cold
IV C Dull pain
Warm

Cutaneous Sensory Receptors

Receptor Location Sensation Adaption
Meissner corpuscle Papillary dermis Touch Rapid
Merkel disc Papillary dermis Pressure Slow
Ruffini corpuscle Reticular dermis Stretch Slow
Pacinian corpuscle Subcutis Vibration Rapid
Free nerve endings Papillary dermis Pain
Temperature
Rapid
Slow

Cranial Nerve Reflexes

Reflex Afferent Efferent
Pupillary CN II CN III
Corneal CN V1 CN VII
Lacrimation CN V1 CN VII
Jaw jerk CN V3 CN V3
Vestibulo-ocular CN VIII CN III & IV & VI
Acoustic CN VIII CN VII
Gag CN IX CN X

Spinal Nerve Motor Functions and Reflexes

Nerve Motor Function Reflex
C5 Elbow flexion Biceps reflex
Brachioradialis reflex
C6 Wrist extension -
C7 Elbow extension Triceps reflex
C8 Finger flexion -
T1 Finger abduction -
L2 Hip flexion -
L3 Knee extension -
L4 Ankle dorsiflexion Patellar reflex
L5 Big toe extension -
S1 Ankle plantar flexion
Hip extension
Achilles reflex

Primitive Reflexes

  • Babinski reflex
  • Galant reflex
  • Grasping reflex
    • Palmar reflex
    • Plantar reflex
  • Moro reflex
  • Parachute reflex
  • Rooting reflex
  • Sucking reflex
  • Tonic neck reflex

Factors Affecting Cerebral Blood Flow

Sleep-Wake Cycle

Stage Waves Disorders
Awake :: eyes open β wave -
Awake :: eyes closed α wave -
NREM sleep N1 θ wave -
NREM sleep N2 Sleep spindles
K complexes
Bruxism
NREM sleep N3 δ wave Sleep terrors
Sleepwalking
Bedwetting
REM sleep β wave Dreaming
Nightmares
Tumescence

Neurologic Examination

Muscle Power (MP)

Grade ROM Anti-Gravity Anti-Resistance
0 - - -
1 +/- - -
2 + - -
3 + + -
4 + + +
5 ++ + +

Deep Tendon Reflex (DTR)

Grade Response
0 None
1 Low
2 Normal
3 High
4 Clonus