Functional Neuroanatomy Flashcards
Which levels of the SC have a lateral horn?
Thoracic and S2-4
Where is spinothalamic / anterolateral tract found in the brain stem?
Found laterally in brain stem, close to medial lemniscus in midbrain.
Pathway for fine touch, vibration, and position from face
Synapses in ipsi trigeminal ganglion, crosses, and ascends in trigeminothalamic tract, which starts medial and then gets more lateral by the time it reaches the thalamus.
Pathway for pain, temp, and gross touch form face
Enters pons via trigeminal nerve but descends down into medulla or upper cervical SC and synapses in spinal trigeminal nucleus. Synapses, crosses, and ascends in trigeminothalamic tract
Pathway for viscerosensation
Viscerosensation ascends in viscerosensory tracts to solitary nucleus, synapses and projects bilaterally via solitariothalamic tracts, ultimately projecting to insula
Paraesthesia vs Dysesthesia
- Paraesthesia – dysfunction of peripheral somatosensory axon causing spontaneous or evoked positive somatosensory sxs that are not unpleasant / painful.
- Dysesthesias are unpleasant / painful
Allodynia
Perception of pain to stimuli that are not normally noxious
Cell pathway for vision
Photoreceptors synapse on retinal bipolar cells, which synapse on retinal ganglion cells, whose axons travel to the thalamus
Pathway from frontal eye field
- Frontal eye field → contralateral pontine horitzontal gaze center (aka pontine paramedian reticular formation / PPRF) → abducens nucleus → left lateral rectus.
- Pontine horizontal gaze center also projects to oculomotor nucleus on other side via medial longitudinal fasciculus
Where are vertical gaze and convergence centers found?
Vertical gaze center found in upper brainstem and is composed of nuclei near oculumotor nucleus. Projects to oculomotor and trochlear nuclei to cause conjugate vertical gaze. This area is also responsible for convergence.
- Tropia
- Phoria
- Exotropia
- Esotropia
- Hypertropia
- Hypotropia
- Skew
- Tropia = fixed dysconjugacy
- Phoria = intermittent dysconjugacy
- Exotropia = deviation of an eye laterally
- Esotropia = deviation of an eye medially
- Hypertropia = deviation of an eye superiorly
- Hypotropia = deviation of an eye inferiorly
- Skew = vertical dysconjugacy
Pupillary light reflex
Visual info for conscious info goes to lateral geniculate nucleus in thalamus. Unconcious info goes to bilateral pretectal nuclei, each of which receives light info from both eyes. Pretectal nuclei then project short distance to Edinger Westphal nucleus, which contains preganglionic parasympathetic neurons. These axons travel w/ ipsi occulomotor nerve to synapse on ciliary ganglion, which contains postganglionic parasympathetic neurons, which project to iris to innervate iris sphincter muscle (smooth muscle).
Term for pupils that aren’t the same size
anisocoria
Pupillary dark reflex
Info sent to hypothalamus. Sympathetic tract from hypothalamus down to T1 to synapse on lateral horn (preganglionic). Second neuron runs up sympathetic chain and ascends back to superior cervical ganglion. 3rd neuron (postganglionic) hitches a ride on arteries (carotid, etc), then finally reaches the pupil to innervate the iris dilator muscle.
Whole pathway is ipsilateral.
Corneal (blink) reflex
Mechanoreceptors trigger ipsi trigeminal nerve to brainstem. Efferent response involves bilateral facial nerves causing strong eye closure
Sound transmission to cochlea
Malleus, incus, stapes vibrate oval window. Endolymph vibrates the basilar membrane.
Which nerve innervates tensor tympani? Stapedius?
Tensor tympani innervated by CN V. Stapedius innervated by CN VII.
Pathway from cochlea to cortex
- Auditory nerve synapses in ipsi cochlear nucleus. Ascends bilaterally in lateral lemniscus to inferior colliculus in midbrain, which projects to thalamus.
- Auditory radiation = tract from thalamus to primary auditory cortex on superior temporal lobe.
Which part of vestibular system uses otoliths?
Vestibule. Senses linear acceleration and gravity.
Pathway from vestibular nucleus to cortex
Vestibular nucleus –> lateral lemniscus –> thalamus –> insula
Vestibular nuclei also connect to cerebellum to control movements as well as to brainstem to control eye movements
Smell pathway
Olfactory nerve is actually a bunch of little “nervelets”. Connects to olfactory bulb, which is CNS. Bulb axons make up olfactory tract, which projects bilaterally to primary olfactory cortex on medial temporal lobe near hippocampus. Only sense that does not go through the thalamus before going to cortex
Which CN’s carry taste info?
CN VII, IX, and X
Where do vagus and glossopharyngeal nerves synapse?
Ambiguus nucleus
- Palsy
- Hemiparesis / plegia
- Paraparesis / plegia
- Diparesis / plegia
- Monoparesis / plegia
- Palsy – another term for weakness that does not distinguish b/w paresis and plegia
- Hemiparesis / plegia – unilateral weakness / paralysis
- Paraparesis / plegia – bilateral leg weakness / paralysis
- Diparesis / plegia – weakness of all 4 limbs that is worse in legs
- Monoparesis / plegia – weakness / paralysis of one limb
What is normal reflex?
What is 4/4 reflex?
Normal reflex is 2/4. 4 = increased reflux + reflex spread or clonus.
Strength 0-5
0 = no muscle contraction 1 = contraction without movement 2 = movement but inability to overcome gravity 3 = antigravity strength but no resistance to the examiner 4 = some resistance to the examiner but not full strength 5 = full strength.
LMN signs
hyporeflexia, hypotonia, atrophy, fasciculations
UMN signs
hyperreflexia, spasticity, extensor plantar response
Arm UMN damage
Distal muscles are weaker, extensor / supinator muscles are weaker. Pronator drift, slow fine finger movements
Leg UMN damage
Distal muscles are weaker than proximal muscles, flexors are weaker than extensors, and dorsiflexion is weaker than plantarflexion.
Hemiparetic gait.
Reflexive limb withdrawal
Complex motor reflex that occurs when a noxious stimulus to a limb activates LMN’s at multiple spinal levels causing movement of multiple joints leading to withdrawal of limb. UMN dysfunction may cause increased reflexive limb withdrawal to noxious or nonnoxious stimuli
Paratonia
Type of hypertonia in which pxs are unable to relax muscles voluntarily. Gets worse the harder they try, and gets better w/ distraction. Seen in pxs w/ damage to frontal association cortex
Anterior corticospinal tract
Minority of axons that do not decussate at pyramidal decussation descend in ipsi anterior column of SC and control movement of torso / neck
Corticobulbar tract
UMN’s going from motor cortex to brain stem. Most get bilateral innervation, except for lower face, which only gets CONTRA innervation. Lips innervated by the facial nerve for speaking. Unilateral dysfunction of nerves to lower face cause dysarthria (abnormal enunciation) and dysphagia
Where does each cerebellar peduncle attach?
Inferior cerebellar peduncle connects to medulla. Middle connects to pons. Superior connects to midbrain
Pathway for correcting info from lateral cerebellum
Correcting info from lateral cerebellum is sent to dentate nucleus. Dentatothalamic tract crosses in the upper brainstem prior to synapsing in contra thalamus.
Dysmetria
limb misses target
Intention tremor
When limb approaches target. Due to damage in lateral cerebellum.
- Dyskinesia
- Chorea
- Athetosis
- Myoclonus
- Ballism
- Dyskinesia – abnormal movements / postures w/o weakness.
- Chorea – involuntary, fast, irregular, mostly distal limb movements that may resemble dancing
- Athetosis – involuntary, slow, writhing, mostly distal limb movements that may resemble movement of snakes
- Myoclonus – involuntary, small, fast movements (jerks), usually of the torso and proximal limbs, simultaneously
- Ballism – involuntary, fast, large proximal limb movements
Dystonia
- Involuntary sustained contraction of one or more muscles causing abnormal movement posture
- Muscles may hypertrophy
- Dystonic tremor may occur which is produced w/ movements that lengthen the effected muscles
Prosody
Emotional content of speech / inflection
Where is ascending arousal system found?
Ascending arousal system scattered throughout reticular formation in brainstem. Also in thalamus and cortex.
Prosopagnosia
inability to visually recognize familiar faces
Anosognosia
inability to perceive neurological deficit such as weakness or sensory loss. Often occurs w/ lesions of right association sensory cortex
