0826 - The Brainstem

Question 1

What are the patten generators and associated nuclei of the medulla?

Answer 1

Runs from pyramidal decussation to pons.
Patterns - Swallowing, vomiting, coughing, sneezing.
Contains pre-motor nuclei innervating CNn IX, X

Question 2

What are the patten generators and associated nuclei of the pons?

Answer 2

Chewing

Supratrigeminal premotor nucleus

Question 3

What are the patten generators and associated nuclei of the midbrain?

Answer 3

Conjugate eye movements

Premotor nuclei innervating III, IV, VI (gaze centre)

Question 4

What are the patten generators and associated nuclei of the pons/midbrain?

Answer 4

Locomotor pattern generators - walking and posture

Pedunculo-pontine nucleus and part of locus coeruleus, input to reticulospinal.

Question 5

What is the function of nucleus solitarius? Which nerves?

Answer 5

Map information from internal environment (taste - VII, IX; blood chemistry IX, X; gut sensations, X) and relay to cardiovascular and cardiorespiratory control.

Question 6

What are the four broad functions of the brainstem? Outline each.

Answer 6

Pattern generators for complex motor patterns
Mapping the internal environment (CN to solitary nucleus, pain to reticular formation, superior colliculi, periaqueductal grey).
Cardiorespiratory control
Cerebro-medullary bottleneck - Very vulnerable to any injury.

Question 7

How do tracts change from spinal cord to medulla? (Motor, visceral, sensory)

Answer 7

Motor - ventral to medial
SY/visceral - lateral to intermediate
Sensory - Dorsal to lateral.

Question 8

Where do the cerebellar peduncles sit in the brainstem?

Answer 8

Inferior - open medulla

Middle and superior - pons.

Question 9

What is the functional difference between the base, tectum, and the tegmentum of the brainstem?

Answer 9

Base (ventral surface to half way to ventricle) contains motor fibres, cortico-cerebellar fibres, and cranial nerve axons.
Tectum (roof of ventricle) contains superior and inferior colliculi.
Tegmentum (floor of ventricle) - Contains cranial nerve nuclei, sensory tracts, and nuclei of reticular formation.

Question 10

Which CN’s connect to the brainstem? Where do they connect?

Answer 10

CNs III-XII (all except I (olfactory), and II (oculomotor). They connect ‘evenly’ in a rule of 4’s if you count I and II first.
III and IV connect to midbrain. III in interpeduncular fossa at level of sup colliculi. IV below inf colliculi, immediately crossing over.
V-VIII connect to pons. V on bulb of pons. Rest emerge from ponto-medullary junction - VI medially, VII and VIII laterally, with VIII being larger.
IX-XII connect to medulla. IX-XI emerge just lateral to the olives, XII between pyramid and olives).

Question 11

Which CN nuclei are contained in the midbrain? How are they laid out?

Answer 11

III - At level of superior colliculs - Motor, medial.
IV - At level of inferior colliculus - motor, medial
V - Somatosensory
CN nuclei are generally close to ventricular system.

Question 12

Which CN nuclei are contained in the pons? How are they laid out?

Answer 12

V somatosensory (goes along brainstem)
V motor - muscles of mastication. Shifted into somatosensory/n. ambiguus column.
VI - Motor, medial between middle cerebellar peduncles.
VII Somaticsensory and taste
VII - Motor. Shifted into somatosensory/n. ambiguus column.
CN nuclei are generally close to ventricular system.

Question 13

Which CN nuclei are contained in the medulla? How are they laid out?

Answer 13

V Somatosensory
Spinal Trigeminal nucleus (sensory) is dorsal in closed medulla. Lateral to cuneate nucleus.
Nucleus Ambiguus - pharynx, larynx, and palate from IX and X. Shifted into somatosensory/n. ambiguus column.
VIII - contains multiple nuclei, but all are in rostral open medulla close to inferior cerebellar peduncle.
(XI) - Motor
XII - Motor -
Medullary nuclei are more elongated than in rest of brainstem.
CN nuclei are generally close to ventricular system.

Question 14

How are sensory and motor nuclei laid out in the brainstem?

Answer 14

Sensory is lateral, motor is medial, with autonomic between them.

Question 15

Which CN nuclei spans entire brainstem?

Answer 15

Somatosensory nucleus of V - on lateral aspect of brainstem, close to dorsal column. ALL somatosensory inputs go here, including from CNs VII, IX, X.

Question 16

Where do all autonomic sensory inputs to CNs end up?

Answer 16

Nucleus solitarius - in medulla, still lateral, but just medial to somatosensory nucleus of V. Carries info from VII, IX, X.
Taste, chemoreception, visceral sensation goes here.

Question 17

Which CN’s carry autonomic motor information? Where are their nuclei?

Answer 17

III - Edinger Westphal nucleus, just lateral to motor nucleus of III in midbrain. (Pupillary constriction)
VII - Superior salivary nucleus, in Pons, just lateral to VI nucleus. (Lacrimal, submandib, sublingual)
IX - Inferior salivary nucleus, in open medulla.(parotid).
X - Dorsal nucleus of X, just lateral to nucleus of XII.

Question 18

What are the four columns of CN nuclei in the brainstem?

Answer 18

Medial-lateral
Motor (III, IV, VI, XII)
Autonomic motor (EW, Sup and Inf Salivary, DMN Vagus)
Autonomic Sensory (Solitarius) and Branchial motor (V, VII, Ambiguus)
Somatir Sensory (sensory V and Vestibular cochlear)
A rule of 4, again if you think that I and II are pure sensory.

Question 19

What is the role of the brainstem in respiratory and cardiovascular control?

Answer 19

Solitary Nucleus and tract in dorsolateral medulla. Chemoreceptor inputs about blood chemistry from CNVII (taste), IX (carotid sinus), X (aortic sinus). Outputs to reticular formation, hypothalamus (endocrine responses), thalamus (taste), and Para and SY control centre. Integrates it all and makes an image of the internal environment for the rest of the brain.
Respiratory controlled by dorsal (inspiration) and ventral (expiration) respiratory nuclei, and medial parabrachial nucleus (ultimate pacemaker).
Cardiovascular controlled by DMNX (para - barovagal), and lateral reticular (decrease SY tone in vasculature - barosympathetic)