brainstem nuclei

tbl 3

tegmentum

midbrain; anterior surface of midbrain which is connected to cerebellum via superior cerebellar peduncle

red nucleus

housed within tegmentum (midbrain); involved in motor coordination during movements

tectum

midbrain; contains the superior and inferior colliculi

superior colliculus

connected to the lateral geniculate body which help direct movement of both eyes in upward gaze; lens accommodation reflex

inferior colliculus

connected to medial geniculate body; process auditory information from cochlear nuclei

pretectal region

midbrain; contains interneurons involved in pupillary light reflex

edinger westphal nucleus

midbrain; ultimately provides innervation to iris sphincter pupillary muscle and lens ciliary muscle to mediate the pupillary light reflex and lens accommodation, respectively

lesions in midbrain

loss of function in CN III and IV; drooping of eyelid (ptosis); pupils are mid-position to dilate, sluggish to fixed reactivity

medial longitudinal fasciculus (MLF)

pons; integrates movements directed by the gaze centers (FEF) and information about head movement, and is an integral component of saccadic eye movements

lesions in MLF

failure of adduction past midline, leading to nystagmus

nuclei of CN V - sensory

receives touch and pressure sensations from face, scalp, oral cavity, and nasal cavity

nuclei of CN V - motor

sends motor impulses to muscles of mastication

superior olivary nucleus

pons; receives auditory impulses form both ears via cochlear nuclei

locus coerulus nucleus

pons; secretes norepinephrine; sends signals to areas which control arousal and REM sleep

raphe nucleus

pons; secretes serotonin; plays a role in mood, aggression, and induction of non-REM sleep

subparabrachial and medial parabrachial nuclei (pneumotaxic center)

pons; controls rate and pattern of breathing by limiting burst of AP’s in phrenic nerve

damage to pneumotaxic center

increase in depth of respiration and a decrease in respiratory rateap

apneustic center

pons; promotes inhalation by delaying the off-switch signal of the inspiratory ramp provided by the pneumotaxic center; discharges and inhibitory impulse to pneumotaxic center

lesions in pons

loss of functions in CN V, VI, VII, and VIII; pinpoint pupils, hyperventilation

medullary pyramids

paired white matter structures that contain motor fibers of corticospinal and corticobulbar tracts; pyramidal tracts decussate (cross) to opposite sides

medulla overview

• contains centers for controlling swallowing, eye movements, coughing/sneezing/vomiting

• cardiac center: regulate heartbeat

• vasomotor center: regulate blood vessel diameter

  • respiratory center: control basic rhythm of breathing

cuneate nucleus

medulla; contains information about light touch, proprioception, and vibration from ipsilateral upper limb

gracile nucleus

medulla; contains information about light touch, proprioception, and vibration from ipsilateral lower limb

nuclei of CN IX - solitary nucleus

medulla; receives taste impulses from posterior one-third of tongue, along with information from carotid sinus baroreceptors and carotid body chemoreceptors

nuclei of CN IX - spinal nucleus

medulla; receives somatic sensory impulses from internal surface of TM, middle ear, upper pharynx, soft palate, and posterior one-third of tongue

nuclei of CN IX - inferior salivatory nucleus

medulla; sends preganglionic parasympathetic fibers to otic ganglion and then to parotid gland

dorsal motor nucleus of CN X

medulla; sends motor axons to muscles of palate, larynx, and pharynx; sends pre-ganglionic parasympathetic fibers to thorax, foregut and midgut parts of GI tract

damage to dorsal nucleus of CN X

difficulty in swallowing and speech

nucleus of CN XII

medulla; sends motor axons to all muscles of the tongue, except palatoglossus

nucleus of tractus solitarius

medulla; projects to reticular formation; forms circuits that contribute to autonomic regulation

inferior olivary nucleus

medulla; regulates motor coordination and learning

nucleus ambiguus

medulla; gives rise to efferent motor fibers of CN X and CN IX

lesions in medulla

• altered consciousness, altered sleep-wake cycle, altered awakeness and alertness

• paralysis in upper/lower limbs; loss of contralateral somatic sensations from the body

• difficulty in swallowing and speaking

• loss of function in CN IX, X, XI, and XII

  • dilated pupils with fixed reactivity, abnormal breathing patterns, absent gag and cough reflexes