brainstem Flashcards
what are the 4 categories of axon each spinal nerve carries
2 x general afferents (somatic and visceral afferents); 2 x general efferents (somatic and visceral efferents)
what do general somatic afferents carry sensation to
skin and striated muscle
what do general visceral afferents carry sensation to
organs
what do general somatic efferents carry motor function to
striated muscle
what do general visceral efferents carry motor function to
smooth muscle and glands
what extra axons are present in the brainstem not found in the spinal cord
special visceral efferent, special visceral afferent, special somatic afferent
what is the order from medial to lateral in the brainstem
GSE, SVE,GVE,GVA,SVA,GSA,SSA
what is the function of general somatic efferent
to cranial myotomes. 6 extraocular muscles(III, IV, VI), and muscles to the tonge (XII)
function special visceral efferent
viscera/branchiomotor. V- mastication etc; VII- facial expression, stapedius etc; IX,X,XI- muscles larynx, pharynx etc
function general visceral efferent
cranial parasympathetic outflow. ciliary ganglion; submandibular and parotid (VII); otic ganglion- parotid gland (IX); para to plexuses in thorax and abdomen (X)
function general visceral afferent
visceral sensation. IX and X. from carotid body and sinus; aorta; thorax; abdomen
function special visceral afferent
taste. from taste buds (VII, IX). from epiglottis (X) and soft palate (VII)
function general somatic afferent
ordinary sensation. CN V. sensation of pain, temp, touch, pressure, vibration, proprioception
function special somatic afferent
hearing and balance
where are special somatic afferent fibres found
hearing and balance - CN VIII
where are special visceral afferents found
taste- CN VII, XI, X
where are special visceral efferents found
V, VII, IX, X, XI
what happens to the neuroblasts that don’t form synapses (as more neuroblasts produced than required)
apoptosis. death of some leads to creation individual CN nuclei (run in brainstem as incomplete columns)
which nuclei are found in midbrain, pons and medulla
general somatic efferent; general visceral efferent; general somatic afferent
which nuclei are found in pons and medulla
special visceral efferent, special somatic afferent
which nuclei are found in just the medulla
general visceral afferent and special visceral afferent
if a patient can hear loud noises without external sound what can this show
damage to VII as innervates stapedius
where is info on proprioception from head taken (CNV)
mesencephalic nucleus of V
where is info from mechanoreceptors taken (CNV)
main sensory nucleus of V
where is nociceptive info taken (CNV)
spinal nucleus of V
where is info from on a) balance and b) hearing
a) semicircular canal b) hearing
which cranial nerves have sensory ganglia associated
V,VII,VIII,IX,X
what is the sensory associated with VII
geniculate
what is the sensory associated with VIII
vestibular fibres- vestibular; cochlear fibres- spiral/cochlear
what happens as the ascending tracts are in the pons
move more laterally so are vulnerable to things such as intracranial bleeds/trauma
is the Median Longitudinal Bundle close or far from the midline
close to midline, in all parts of the brainstem
what does the median longitudinal bundle connect
connects oculogyric nuclei together; connects oculogyric and vestibular nuclei (when head moves can remain focused); connect oculogyric nuclei to tectospinal tract (from tectum- controls muscle of neck)
what allows for bilateral fixation (conjugate eye movement)
posterior commissure at top of midbrain- connects right and left side so connects right and left MLB. oculogyric nuclei joined on both sides so allows for perfect coordination
what pathway controls axial muscles so maintaining stance and posture
vestibulospinal tract
what is another intrinsic tract of the brainstem that SVA and GVA fibres run in; where is it found
nucleus tractus solitaries. only in medulla
what is the role of the nucleus tractus solitarius
activate pre ganglionic autonomic neurones to elicit a response. can go direct to neurones or via visceral centres
in some cases what are activated as well as preganglionic autonomic neurones
lower motor neurones. eg vomiting reflex need contraction of abdominal muscle; coughing- intercostals contract
what are the ascending tracts that pass through the brainstem (sensory)
dorsal column medial lemniscus pathway, spinothalamic, trigeminothalamic, spinocerebellar
what are the descending tracts through the brainstem and where do they come from/to
corticospinal (cortex- ventral horn); corticobulbar (cortex- brainstem); corticopontine (cortex- pons); hypothalamic efferents
what does the corticospinal tract activate
LMNs (doesn’t synapse in brainstem)
what does the corticobulbar tract activate
motor neurones in brainstem (GVE, GSE, SVE)
what does the corticopontine tract give off
another tract to the cerebellum
what is the reticular formation
small clusters of neurones in between larger structures (nuclei and tracts)
how is the reticular formation organised
discontinuous columns- raphe is in the midline; then a lateral zone either side of the raphe
what are the only neurones in the CNS that use serotonin as the neurotransmitter
neurones in the raphe nuclei
where do neurones project from the raphe nuclei
to the spinal cord- 2 destinations: dorsal horn (analgesia) and lower lumbar and sacral parts of cord. also projects upwards to hypothalamus and cortex
what is the raphe nuclei involved in
sleep/wake state. if destroyed- insomnia. can be stimulate with drugs to prevent sleep.
what does the rostral projection of the raphe nuclei interact with in schizophrenia
dopamine
what are the lateral columns of the reticular formation involved with
ascending reticular activating system. projects up into hemisphere
what are the lateral columns involved in determining
state of alertness, arousal and consciousness.
what else do the lateral columns of reticular formation give off
reticulospinal tracts. counteract effects of gravity, effect on axial muscle
what other pathways are associated with lateral zones of reticular formation
pain relief- interrupt pain in dorsal horn; visceral centres - to pregang autonomic under control of NTS
what are the 2 nuclei associated with noradrenaline in reticular formation
locus coeruleus, and tegmental nucleus
where does the tegmental nucleus project
spinal- maintain urinary continence (stimulates pre ganglionic autonomic neurones); rostral- hypothalamus involved in endocrine
where does the locus coeruleus project to
entire CNS. related to depression
what secretes dopamine, where does it project to
substantia nigra projects to corpus striatum (overall DA more restricted)
what pathways use dopamine
mesolimbic and mesocortical
which pathways are under and over active in schizophrenia
mesolimbic- overactive, mesocortical- underactive
how is the facial motor nucleus connected to the oculogyric nuclei
MLB
what are the tectum and pre tectal areas linked to
MLB
what are the small bumps on the tectum
superior and inferior colliculi
what is involved with visual reflexes
superior colliculi and pre tectal area
what is pupillary constriction achieved by (para or symp, which fibres)
parasymp system, via CNIII
what happens in pupillary constriction
retina -> pre tectal area -> CNIII (EW) -> ciliary ganglion -> constrictor pupillae
what happens in pupillary dilation
retina -> dorsolateral part of brainstem -> T1 sympathetic preganglionic neurones -> sympathetic chain -> superior cervical ganglion -> dilator pupillae muscle
what is the consensual reflex
some fibres from retina go to both sides of pre tectal area so both pupils will dilate/constrict together
if changing gaze from far to close what has to happen
medial rectus contracts to bring the eyes together, lateral rectus is inhibited
to focus light onto the retina what has to happen
pupils constricted- contract constrictor pupillae and contract ciliary muscle
where does info sensed by the retina in the light reflex go to
superior colliculus in midbrain by fibres which leave the optic nerve
in the tectum (in light reflex) fibres go to innervate motor neurones via what tracts
tectospinal and tectobulbar tracts
what happens in the tectospinal tract
retina -> superior colliculus -> tectospinal tract -> cervical cord -> LMNs to neck muscles
what happens in the tectobulbar tract
retina -> superior colliculus -> tectobulbar tract -> CNVII -> orbicularis oculi
what supplies the brainstem
vertebral arteries. vertebra-basilar system
what are the 3 small groups of arteries and what do they supply
paramedian- middle section; short circumferential- around the brainstem supply ventrolat areas; long circumferential- around brainstem also dorsolat area
what is syndrome of lower red nucleus
oculomotor nerve palsy- contralat hemiparesis, ataxia, hemiplegia; and mid brain infarction- occlusion of branch of post cerebral artery
what is syndrome of midpontine
occlusion paramedian branches basilar artery. contralateral hemiplagia
what is dorsolateral medullary syndrome
injury to lat part of medulla- tissue ischaemia and necrosis
