Lecture 13: Brainstem, Nuclear Organization Flashcards
What is the difference of organization of spinal cord vs. brainstem?
Spinal cord has motor neurons ventrally and sensory neurons dorsally
Brainstem has motor neurons medially and sensory neurons laterally
So brainstem rotated 90 degrees
Sulcus limitans
marked the separation between motor and sensory neurons in spinal cord and brain stem
Functional columns
columns of cranial nerve nuclei in brainstem
In brainstem, how are the functional columns organized?
- 3 motor functional columns
- 3 sensory functional columns
Column 1 (most medial, GSE)
Skeletal muscle of myotomes
Exits medially
What nuclei does column 1 contain
Oculomotor nuclei
Trochlear nuclei
Abducens Nuclei
Hypoglossal Nuclei
Why are there crossed neurons coming from the oculomotor nuclei and trochlear nuclei?
The ones in oculomotor nuclei that are crossing only go to the SUPERIOR rectus
- so superior oblique and superior rectus are cross-innervated
- similarities between the two muscles
Column 2 (GVE)
PARASYMPATHETICS
exit point not touched upon in lecture
What nuclei does column 2 contain?
Edinger-Westphal nucleus (parasympathetic of oculomotor; ciliary ganglion; dilates pupil)
-functions as motor limb of light reflex and near response (accommodation)
superior salivatory nucleus = CN VII
-innervates lacrimal gland, submandibular and sublingual glands
Inferior salivatory nucleus = CN IX
-innervates parotid gland
-synapse in the otic ganglion
Dorsal motor nucleus of vagus = CN X
-responsible for innervation of thoracic and abdominal
-not involved in head and neck!
What does loss of light reflex and near response indicate?
Loss of edinger-westphal nucleus (CN III) because parasympathetics mediate the motor portion of those responses
What does loss of lacrimation mean?
Loss of Superior Salivatory nucleus, or loss of CN VII parasympathetics
What does loss of parotid gland function mean?
Hard to tell but it means a CN IX lesion
Column 3 (SVE)
muscles of facial expression and throat control; migrated medial to lateral
Exits ventrolaterally
What nuclei does column 3 contain?
motor nucleus of V (mastication)
motor nucleus of VII (facial expression)
Nucleus Ambiguus (IX, X) palate, pharynx and pharynx muscles
Parasympathetic nerves (that should be in dorsal motor nucleus of vagus) is present in nucleus ambiguous (so it has both motor and parasymp as well)
Column 4 (SVA)
Solitary Nucleus
-represents the fusion of functional columns SVA and GBA
-visceral sensory nucleus
-SVA = gustatory nucleus = taste = 7, 9, 10
-GVA = cardiorespiratory nucleus = carotid sinus, carotid body = self-regulates change blood in pressure and pH
Crosstalk to with dorsal motor nuclei in column two in order to control heart rate, etc. (since DMX controls parasympathetics of thoracic)
Column 5 (SSA)
vestibular nuclei -superior -lateral -medial -spinal Function: balance, retinal/vision
Where is the cochlear nuclei?
lateral of vestibular nuclei in column 4 of medulla
Functions as receptor of auditory stimulli
Column 6 (GSA):
Touch, proprioception, pain and temperature (sensation)
-travels with the motherfucking motor neurons of cranial nerve 5!!!!
Contains the following:
-mesencephalic nucleus and tract of V
Function: proprioception
-principle (aka chief or main) sensory nucleus of V
Function: touch
-spinal trigeminal nucleus (pars oralis):
Function: facial touch
-spinal trigeminal nucleus (pars interpolaris)
Function: tooth pulp pain
-spinal trigeminal nucleus (pars caudalis): face pain and temperature
-cochlear nuclei is wrapped around in medulla oblongata
-7, 9 and 10 also project sensation to trigeminal sensory nuclei
Mnemonic: MPS = mean people suck
Mesenphalic
Principle
Spinal
What is the significance of having the pain and temperature sensory nuclei so far below?
It means the afferent sensory neurons have to run DOWN the brainstem to synapse with its secondary sensory neuron
-that’s why CNV can be lesioned at any level of the brainstem
What is the course of sensory CNV neurons?
- primary sensory neuron has cell body in trigeminal ganglion
- secondary sensory nuclei has cell body in VPM
When you see an inferior olive, what brainstem section is it?
Upper medulla
We see representation of all 6 functional columns
-3 motor and 3 sensory
-it shows that you can have lesions of the vestibular nuclei (CN 8) and spinal trigeminal (CN 5) at the level of medulla! Which is unexpected
What is the trigeminothalamic tract?
Where secondary sensory neurons arising from spinal nucleus come together
-remember, secondary sensory neurons all cross to form this tract
By definition, secondary sensory neurons must
Cross, so that means a lesion to trigeminothalamic tract would lead to CONTRALATERAL symptoms
What part of the thalamus takes in the secondary sensory neurons of the thalamus?
Ventral Posterior Medial (VPM) nuclei
-then takes shit to S1
What types of sensory neurons inhabit the mesenphalic nucleus of V?
Mesenphalic = primary sensory neurons
- primary sensory neurons derive from neural crest cells
- sends signals to secondary sensory neurons in principal nucleus and motor nucleus of V as part of jaw jerk reflex
What does mesenphalic nucleus of V do?
It is a stretch receptor (proprioceptive) primary sensory neuron
What is the difference between VPM and VPL?
VPM = facial touch VPL = body wall touch
How do pain/temperature and touch receptors differ on face?
Touch receptors = V1, V2 and V3 = superior to inferior
Pain and temperature = onion shape
-the more inferior the spinal nucleus, the more dorsal the pain and temperature modalities
At what level do sensory neurons of principal and spinal trigeminal nucleus enter?
Mid-Pons
What happens with lesion in medulla?
Loss of pain and temperature fibers and no loss of touch
What does ICP do?
Carries spinocerebellar pathway (clarke’s nucleus) and inferior olivary nucleus
Allows for lower limb proprioception
Updates about ongoing execution to vermis and paravermal cortex
What does MCP do?
Carries neurons from pontine nuclei, cerebrocerebellum pathway
Smooth execution of movements
Motor plan to the Hemisphere
What will localize the lesion in brainstem?
It is impossible to have a brainstem vascular syndrome WITHOUT affecting a cranial nerve
-the clinical symptoms will let you know where the vascularity is disrupted in the brain stem
Brain stem has distinct lateral and medial vascular territories. What will be the effect of a vascular insult?
- a long tract will be affected
- A cranial nerve will be affected
- motor CNs in medial
- mixed CNs in lateral
So both a long tract to cranial nerve will be affected
What nuclei are in the midbrain?
i. Oculomotor
ii. Edinger-Westphal
iii. Trochlear
iv. Mesenphalic of V
What nuclei are in the Pons?
i. abducens
ii. Superior salivatory nuclei
iii. Motor trigeminal
iv. Motor facial
v. part of vestibular nuclei
vi. principal sensory nucleus of V
vii. Spinothalamic trigeminal (pars oralis)
What nuclei are in the medulla?
i. Hypoglossal nuclei
ii. Inferior salivatory nuclei
iii. Dorsal Motor of X (DMX)
iv. Nucleus ambiguous
v. Solitary nucleus (gustatory and cardiorespiratory)
vi. Vestibular nuclei
vii. Cochlear nuclei
viii. spinal trigeminal nuclei (pars interpolaris and pars caudalis)
