Neuroanatomy and Pathways: Brainstem, Cranial Nerves, and Sensory Systems

What are the three subdivisions of the brainstem?

Midbrain, pons, medulla oblongata

What defines the border between the brainstem and spinal cord?

The foramen magnum / level of the pyramidal decussation

Name two prominent surface landmarks of the medulla oblongata.

Pyramids and olives

Which cranial nerves are associated with the medulla oblongata?

CN IX (Glossopharyngeal), CN X (Vagus), CN XI (Accessory), CN XII (Hypoglossal)

What part of the ventricular system is associated with the medulla oblongata?

Fourth ventricle

What part of the ventricular system is associated with the pons?

Fourth ventricle

Which cranial nerves are associated with the pons?

CN V (Trigeminal), CN VI (Abducens), CN VII (Facial), CN VIII (Vestibulocochlear)

What surface landmarks are associated with the midbrain?

Cerebral peduncles, superior colliculi, inferior colliculi

Which cranial nerves are associated with the midbrain?

CN III (Oculomotor), CN IV (Trochlear)

What part of the ventricular system is associated with the midbrain?

Cerebral aqueduct

Which cranial nerves are sensory only?

CN I (Olfactory), CN II (Optic), CN VIII (Vestibulocochlear)

Which cranial nerves are motor only?

CN III, CN IV, CN VI, CN XI, CN XII

Which cranial nerves are mixed (sensory and motor)?

CN V, CN VII, CN IX, CN X

What is the modality of the trigeminal nerve (CN V)?

Mixed; facial sensation and muscles of mastication

What is the modality of the facial nerve (CN VII)?

Mixed; facial expression, taste (anterior 2/3 tongue), lacrimation and salivation

What is the modality of the glossopharyngeal nerve (CN IX)?

Mixed; taste (posterior 1/3 tongue), salivation, carotid body sensation

What is the modality of the vagus nerve (CN X)?

Mixed; parasympathetic control of thoracic and abdominal organs

Which cranial nerves do NOT attach to the brainstem?

CN I (Olfactory) and CN II (Optic)

Which cranial nerve exits the dorsal brainstem?

CN IV (Trochlear)

What sensory modalities travel via the dorsal column-medial lemniscus pathway?

Fine touch, vibration, proprioception

Where is the primary (first-order) neuron located for DCML?

Dorsal root ganglion

Where does the first synapse occur in DCML?

Gracile and cuneate nuclei in the medulla

Where does the DCML pathway decussate?

In the medulla

Where is the second-order neuron located in DCML?

Medulla oblongata

Where does the third-order neuron originate?

Thalamus (VPL nucleus)

Where does DCML project in the cortex?

Primary somatosensory cortex (postcentral gyrus)

What modalities travel via the spinothalamic pathway?

Pain, temperature, crude touch

Where is the primary (first-order) neuron located for spinothalamic pathway?

Dorsal root ganglion

Where does the first synapse occur in the spinothalamic pathway?

Dorsal horn of the spinal cord

Where does the spinothalamic pathway decussate?

In the spinal cord (anterior white commissure)

Where is the second-order neuron located for spinothalamic pathway?

Spinal cord

Where does the third-order neuron originate for spinothalamic pathway?

Thalamus (VPL nucleus)

Where does the spinothalamic pathway project in the cortex?

Primary somatosensory cortex

Where does DCML cross the midline?

In the medulla

Where does the spinothalamic pathway cross the midline?

In the spinal cord

Which pathway crosses closer to the point of entry?

Spinothalamic pathway

Which sensory pathway ascends ipsilaterally before crossing?

Dorsal column-medial lemniscus