GS - Structure and function of Brainstem Flashcards
What are all the cranial nerves ?
I Olfactory
Il Optic
III Oculomotor
IV Trochlea
V Trigeminal
VI Abducens
Vll Facial
Vlll Vestibulocochlear
IX Glossopharyngeal
X Vagus
Xl Accessory
Xll Hypoglossal
Most cranial nerves emerge from the ventral aspect of the brain/brainstem while their
associated nuclei are located dorsally. Which cranial nerve is the exception and is
known to be the smallest and also crosses over soon after it emerges?
IV Trochlea - emerges from posterior
Where is cranial nerves grey matter found?
Dorsal brainstem
Cranial nerves grey matter is intermittent as separate blobs in the dorsal brain stem (seen once cerebellum removed)
How is motor, visceral and sensory nuclei arranged in the brainstem and how does this change going down to the spinal cord?
During development the CSF filled IV ventricle of the brain opens out and relocates sensory grey matter into lateral positions (as seen in image 2)
This is why the somatic sensory grey matter nuclei of cranial nerves are positioned lateral to the more central somatic motor grey matter
Spinal cord positions;
- Motor is Ventral (Red)
- Visceral is lateral (Yellow)
- Sensory is dorsal (Blue)
What is the general rule for motor and sensory nuclei in the brainstem?
Motor = Medial
Sensory = To Side (Lateral)
Some of the somatic motor nuclei (labelled red) are close to the midline
Some of the somatic sensory nuclei (labelled blue and light green) are more lateral
The parasympathetic (PS) nuclei are found at an intermediate location. This rule is more consistent in lower brainstem although it is not a hard and fast rule for all cranial nerve components and is less consistent as one ascends up the brainstem….
Where do most cranial nerves emerge from and where is the cranial nuclei located?
Grey matter nuclei are located at the back of the brainstem (dorsal) and cranial nerves exit ventrally
What Somatic nuclei do we have, what is their function, what do they supply and where are they located?
Somatic motor nuclei - Drive of Eye and Tongue muscles;
Eye;
- III Oculomotor (all external ocular muscles to eye except LR6 SO4)
- IV Trochlear (Superior Oblique)
- VI Abducens (Lateral rectus)
Tongue;
- XII Hypoglossal (tongue muscles)
Remember as these nerves are all factors of 12!
What Autonomic motor (general visceromotor/parasympathetic) nuclei do we have, what is their function, what do they supply and where are they located?
Autonomic motor (general visceromotor/parasympathetic);
- III Oculomotor parasympathetic nucleus/Edinger-Westphal nucleus (Pupillary constriction and accommodation)
- VII (from facial) Superior salivatory nucelus (lacrimal, sublingual and submandibular glands)
- IX (Glossopharyngeal) Inferior salivatory nucelus (parotid gland)
- X Dorsal motor nucelus of vagus (secretomotor to gut, lungs and heart)
What Special visceral motor (SVE/brachiomotor) nuclei do we have, what is their function, what do they supply and where are they located?
“Chew, Grimace, Swallow, Speak, Shrug”
- V Trigeminal motor nucelus (muscles of mastication)
- VII Facial motor nucelus (muscles of facial expression)
- Nucelus ambiguus (pharynx, larynx, IX - stylopharangeus, X - Swallowing, phonation muscles)
- Nucleus ambigus (XI- SCM snd neck)
What are the general rules to remember motor components from scratch ?
MOTOR COMPONENTS
FROM SCRATCH
(all CNS except special sense I, II and VIII)
Choose what it does?
(1) Does nerve control eye or tongue movement?
- Ill, IV, VI and XII
(2) Does it control “chewing, grimacing, swallowing, talking,
shrugging shoulders (muscles of jaw, face, pharynx and
larynx, SCM+trapezius)
V, VII, IX and X and XI
Is there glands or smooth muscle control to ADD into these - Ill (eye), Vll and IX (salivation), X vagus functions
What Somatic sensory nuclei (trigeminal nuclei) do we have, what is their function, what do they supply and where are they located?
Somatic sensory nuclei (trigeminal nuclei);
- Trigeminal mesencephalic Nucleus of V (proprioception of mouth/jaw)
- Trigeminal principal Nucleus of V (fine touch from face, vibration, light touch)
- Trigeminal spinal Nucleus of V (pain, temp, coarse touch - face, back of tongue, pharynx, larynx and ear)
(Think of spinal nuclei as a continuation of the spinal cord dorsal horn of sensory matter)
Remember - somatic sensory input into spinal nucelus via nerves VII (ear, small), X (larynx-pharynx, ear) and via IX (tongue, pharynx and ear)
What Special Somatic sensory nuclei do we have, what is their function, what do they supply and where are they located?
Special Somatic sensory = Head and Neck
Vestibulocochlear nuclei (hearing and balance)
II Vision (somatic)
VIII Hearing and balance (somatic)
These are PURE sensory and have no other motor and sensory components!
These inputs are specialised for conscious sensation in head and neck and do not have comparable elements in spinal cord
What Visceral sensory nuclei do we have, what is their function, what do they supply and where are they located?
Visceral sensory nuclei (special and general visceral sensory into solitary nucleus)
TASTE;
VII - Taste anterior tongue
IX - Taste posterior tongue
X - Taste Epiglottis
Solitary nucelus - Taste - VII, IX, X
Solitary nucelus - Baroreceptors and chemoreceptors - IX, X
(general visceral sensory input from chemoreceptor and baroreceptor input into IX and X also feeds into the solitary nucelus)
Remember taste inputs are specialised for head and neck while general visceral sensory correspond to autonomic sensory in spinal cord.
Note olfactory I (smell) is also a visceral sensory nerve and is pure sensory in cerebral cortex
How do we build all cranial nerves from scratch ?
Building Cranial Nerves (CNS) from scratch;
Ask first is it special sensory - l, Il and Vlll (pure, no other components put these” aside”) - ALL other CNS have MOTOR components
MOTOR CNs DIVIDE into:
Somatic - eye or tongue - Ill, IV, VI or Xll
OR
SVE - chew, grimace, swallow, talk, shrug” -V, Vll, IX, X or Xl
(now ADD parasympathetic to - Ill (eye), Vll and IX ( for salivation), X (vagus functions)
SENSORY components (remaining) DIVIDE into those that feed into either:
- CN V nuclei V (and Vll, IX and X)
OR
- Solitary nucleus taste from Vll, IX and X general visceral sense from IX and X
How do we test cranial nerves clinically ?
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Name the parts of the brainstem in the midbrain?
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Name the parts of the brainstem in the medulla?
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What is the general rule for tracts and whether they are medial or lateral in brainstem?
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What vessels supply the medulla?
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What vessels supply the pons?
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