Brainstem and Cranial Nuclei

Question 1

what are the three functions of the brainstem

Answer 1

1. A Conduit – longitudinal tracts to and from the brain and cerebellum and spinal cord
2. Cranial nerve functions via brainstem nuclei
3. And integrative & modulatory functions through the reticulum

Question 2

what are the boundaries of the brainstem

Answer 2

Anterior:
• Clivus
• Nerves & vessels Posterior:
• Cerebellum & attachments
nferiorly:
• Foramen magnum & spinal cord
Superiorly:
• Tentorium cerebelli & diencephalon

Question 3

Corticospinal descending pathway

A brainstem lesion of the lateral corticospinal tract will produce contralateral UMN signs

Answer 3

Carries motor information from the cortex to lower motor neurons in the spinal cord.
• 90% decussate in the medullary pyramids
• 10% remain ipsilateral until bilaterally
innervating LMNs in the spinal cord

Question 4

Corticobulbar descending pathways.

A brainstem lesion of these tracts will produce effects dependant on where the lesion is
Corticobulbar pathways

Answer 4

Carry motor information from the motor cortex to motor nuclei of the brainstem.
• Innervation from this pathway is bilateral with the fibre decussation occurring at the level of the nucleus

Question 5

Medical lemniscal
pathway

Brainstem lesion of this tract produces contralateral loss of JPS and discriminating touch.

Answer 5

carries JPS and mechanical information (discriminating touch vibration & pressure etc) from the dorsal columns
• Pathway decussates after the gracile/cuneate nuclei and ascends medially to the thalamus
• Pathway terminates in the sensory cortex

Question 6

Spinal lemniscal pathway is

Brainstem lesion of this tract produces a
contralateral loss of pain and temperature sensation.

Answer 6

the extension of the spinothalamic tract through the Brainstem, it carries pain and temperature sensation
• Pathway decussates quickly in the spinal cord and ascends laterally to the thalamus
• Pathway terminates in the sensory cortex

Question 7

Spinocerebellar tract

Brainstem lesion of this tract produces an ipsilateral defect.

Answer 7

carries proprioceptive information. Tract ascends ipsilaterally in the lateral portion of the brainstem to the pons, where it enters the brainstem.

Question 8

where is the reticulum found

Answer 8

Found throughout the brainstem, located in the central tegmentum.

Question 9

what is the reticulum

Answer 9

Diffuse network of neurons without detectable nuclei but which work predominantly in groups of neurotransmitter related networks.

Question 10

what is the reticulum responsible for

Answer 10

wide variety of functions, eg regulation of pain sensation, arousal of the cortex and modulation of descending motor output

Question 11

ranial nerves follow the rule of 4,

Answer 11

• There are 4 cranial nerves in or above the midbrain
• There are 4 cranial nerves in the Pons
• There are 4 cranial nerves in the medulla

Question 12

Oculomotor nucleus (Oculomotor N. 3)

Answer 12

Function: control of extraocular eye muscles except superior oblique and lateral rectus

Question 13

Trochlear nucleus (Trochlear N. 4)

Answer 13

Function: control of superior oblique muscle of the eye

Question 14

Abducens nucleus (Abducens N. 6)

Answer 14

Function: control of lateral rectus muscle of the eye

Question 15

Hypoglossal nucleus (Hypoglossal N. 12)

Answer 15

Function: control of tongue muscles

Question 16

Trigeminal motor nucleus (Trigeminal N. 5)

Answer 16

unction: Controls muscles of mastication

Question 17

Facial nucleus (Facial N. 7)

Answer 17

Function: control of muscles of facial expression (NB ventral to the Vestibulocochlear nucleus)

Question 18

Nucleus ambiguus

Answer 18

function: Motor to pharynx and larynx

Question 19

Accessory nucleus

Answer 19

function: Motor to sternocleidomastoid and trapezius muscles

Question 20

chewing

Answer 20

5

Question 21

grimace

Answer 21

7

Question 22

swallow

Answer 22

9-10

Question 23

speak

Answer 23

9-10

Question 24

shrug

Answer 24

11

Question 25

Edinger-Westphal nucleus (Occulomotor N. 3)

Answer 25

Function: control of pupillary constriction and lens accommodation

Question 26

Superior Salivatory nucleus (Facial N. 7)

Answer 26

Function: control of lacrimal sublingual and submandibular glands, salivary glands (Facial N. 7 & Glossopharyngeal N. 9) NB Nucleus Ambiguus also supplies N. 9

Question 27

Inferior Salivatory nucleus (Glossopharyngeal N. 9)

Answer 27

Function: control of parotid gland

Question 28

Dorsal motor nucleus of the Vagus (Vagus N. 10)

Answer 28

Function: secretomotor to lungs and gut; control of heart rate

Question 29

Trigeminal mesencephalic – somatic sensory

Answer 29

Function: Proprioception from the mouth

Question 30

Trigeminal pontine (principal) – somatic sensory nucleus
(Trigeminal N. 5)

Answer 30

Function: Discriminating touch from face

Question 31

Vestibulocochlear nucleus (Occulomotor N. 8) - Special sensory

Answer 31

Function: Balance and hearing

Question 32

Solitary nucleus - Visceral sensory

Answer 32

Function: Taste (Facial N. 7, Glossopharyngeal N. 9, Vagus N. 10), carotid baroceptors (Glossopharyngeal N. 9) & visceral afferent from pharynx, larynx lungs, gut (Vagus N. 10)

Question 33

Trigeminal spinal nucleus (Trigeminal N. 5) – somatic sensory

Answer 33

Function: pain and temperature sensation from face, back of tongue, pharynx larynx and ear