Nervous System
Layers of Scalp {SCALP}
- Skin
- Connective tissue
- Aponeurosis
- Loose connective tissue
- Periosteum
Brain Sutures and Fontanels
Cranial Passages
| Passage | Nerves | Vessels |
|---|---|---|
| Cribriform plate | CN I | - |
| Optic canal | CN II | Ophthalmic artery |
| Superior orbital fissure | CN III & IV & V1 & VI | Ophthalmic vein |
| Inferior orbital fissure | CN V2 | Ophthalmic vein |
| Foramen rotundum | CN V2 | - |
| Foramen ovale | CN V3 | - |
| Foramen spinosum | - | Middle meningeal artery |
| Internal auditory meatus | CN VII & VIII | - |
| Jugular foramen | CN IX & X & XI | Jugular vein |
| Hypoglossal canal | CN XII | - |
| Foramen magnum | Brainstem | Vertebral artery |
| Common tendinous ring | CN II & III & V1 & VI | Ophthalmic artery |
| Cavernous sinus | CN III & IV & V1 & V2 & VI | Internal carotid artery |
Cavernous Sinus
Cranial Parasympathetic Ganglia
| Ganglion | Nerve | Innervation |
|---|---|---|
| Ciliary ganglion | CN III | Sphincter pupillae Ciliary muscle |
| Pterygopalatine ganglion | CN VII | Lacrimal gland Nasal glands |
| Submandibular ganglion | CN VII | Submandibular gland Sublingual glands |
| Otic ganglion | CN IX | Parotid gland |
Branches of Facial Nerve
| Mnemonic | Branch |
|---|---|
| The | Temporal nerve |
| Zebra | Zygomatic nerve |
| Brought | Buccal nerve |
| My | Masseteric nerve |
| Car | Cervical nerve |
Vertebral Ligaments {SIFPA}
- Supraspinous ligament
- Interspinous ligament
- Flavum ligament
- Posterior longitudinal ligament
- Anterior longitudinal ligament
Types of Neurons
Blood Brain Barrier
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 cell
- 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 | - | - |
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 |