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Study​ ​Guide:​ ​Neuro​ ​Exam​ ​#3
Movement
● Mirror​ ​neurons:​ ​-active​ ​during​ ​prep​ ​for​ ​a​ ​movement​ ​and​ ​while​ ​observing​ ​someone​ ​else
doing​ ​the​ ​same/​ ​similar​ ​movement
-may​ ​be​ ​important​ ​for​ ​understanding,​ ​identifying,​ ​imitating​ ​(i
...
​ ​social)
-not​ ​just​ ​biological​ ​movement,​ ​but​ ​movement​ ​with​ ​intent
● Descending​ ​movement​ ​pathways:

-messages​ ​from​ ​the​ ​brain​ ​must​ ​reach​ ​the​ ​medulla
and​ ​spinal​ ​cord​ ​in​ ​order​ ​to​ ​control​ ​the​ ​muscles
-corticospinal​ ​tracts:​ ​cerebral​ ​cortex​ ​→​ ​spinal​ ​cord
1)​ ​Lateral​ ​Corticospinal​ ​Tract
2)​ ​Medial​ ​Corticospinal​ ​Tract

● Lateral:​ ​-Fine​ ​movements
-controls​ ​movement​ ​in​ ​peripheral​ ​areas​ ​(hands​ ​and​ ​feet)
-set​ ​of​ ​axons​ ​from​ ​M1,​ ​surrounding​ ​areas,​ ​and​ ​red​ ​nucleus​ ​to​ ​spinal​ ​cord
-red​ ​nucleus:​ ​midbrain​ ​area​ ​with​ ​output​ ​mainly​ ​to​ ​arm​ ​muscles
-decussates
● Medial:​ ​-Posture/​ ​Overall​ ​tone​ ​of​ ​musculature
-set​ ​of​ ​axons​ ​from​ ​many​ ​parts​ ​of​ ​the​ ​cortex​ ​including​ ​the​ ​reticular​ ​formation,
midbrain​ ​tectum,​ ​and​ ​vestibular​ ​nucleus​​ ​(balance/​ ​where​ ​you​ ​are​ ​in​ ​space)
-does​ ​not​ ​decussate
● Cerebellum:

-establishing​ ​new​ ​motor​ ​programs,​ ​execution​ ​of​ ​a​ ​sequence​ ​of​ ​actions
-possibly​ ​involved​ ​in​ ​ability​ ​to​ ​shift​ ​attention​ ​and​ ​attend​ ​to​ ​visual​ ​stimuli
-receives​ ​input​ ​from​ ​spinal​ ​cord,​ ​sensory​ ​system​ ​and​ ​cerebral​ ​cortex,​ ​and
sends​ ​it​ ​to​ ​the​ ​cerebellar​ ​cortex​ ​(surface)

● Cerebellar​ ​ataxia:​ ​man​ ​could​ ​not​ ​put​ ​his​ ​finger​ ​to​ ​his​ ​nose​ ​(did​ ​not​ ​know​ ​the​ ​destination)
● Cerebellar​ ​cortex​ ​neurons​ ​are​ ​arranged​ ​in​ ​precise​ ​geometric​ ​patterns:​ ​(regular​ ​patterns
allow​ ​for​ ​outputs​ ​of​ ​well-controlled​ ​duration)

1) Purkinje​ ​cells:​ ​flat​ ​parallel​ ​cells​ ​in​ ​sequential​ ​planes,​ ​inhibitory​ ​→​ ​to​ ​the​ ​nuclei​ ​of​ ​the
cerebellum​ ​and​ ​vestibular
nuclei,​ ​then​ ​to​ ​the​ ​midbrain
and​ ​thalamus
More​ ​purkinje​ ​cells​ ​=​ ​greater​ ​duration​ ​of​ ​response
2) Parallel​ ​fibers:​ ​axons​ ​parallel​ ​to​ ​one​ ​another;​ ​perpendicular​ ​to​ ​planes​ ​of​ ​Purkinje​ ​cells,
Excitatory​ ​(excite​ ​the​ ​Purkinje​ ​cells)
​ ​ ​ ​+
​ ​ ​ ​ ​ ​ ​ ​ ​Cerebral​ ​→​ ​Parallel​ ​fibers​ ​→​ ​Purkinje​ ​cells​ ​→​ ​Cerebellar​ ​and​ ​Vestibular​ ​Nuclei​ ​→​ ​Midbrain
Cortex
and​ ​Thalamus
● Basal​ ​Ganglia:
-group​ ​of​ ​large​ ​cortical​ ​structures​ ​in​ ​the​ ​forebrain
-initiating​ ​actions​ ​not​ ​guided​ ​by​ ​a​ ​stimulus
-striatum​ ​=​ ​caudate/putamen
1)​ ​caudate​ ​nucleus​ ​(wrapped)
2)​ ​putamen​ ​(egg-like)
3)​ ​globus​ ​pallidus
-select​ ​a​ ​movement​ ​to​ ​make​ ​by​ ​ceasing​ ​to​ ​inhibit​ ​it
● Disinhibition:​ ​suppression​ ​of​ ​motor​ ​programs
that​ ​are​ ​vying​ ​for​ ​control​ ​of​ ​our​ ​musculature,
and​ ​releasing​ ​a​ ​single​ ​motor​ ​program​ ​that​ ​we
actually​ ​need
● Cortex​ ​can​ ​only​ ​effectively​ ​stimulate​ ​the
striatum​ ​in​ ​the​ ​presence​ ​of​ ​dopamine
● Pallidum​ ​is​ ​the​ ​one​ ​that​ ​cuts​ ​of​ ​constant​ ​motion​ ​from​ ​happening,​ ​and​ ​striatum​ ​is​ ​the​ ​one
that​ ​ultimately​ ​allows​ ​a​ ​movement​ ​to​ ​occur
● Pallidum​ ​activity​ ​is​ ​tonically​ ​high,​ ​but​ ​striatum​ ​activity​ ​is​ ​tonically​ ​low​ ​(tonic​ ​=​ ​baseline)
● Substantia​ ​Nigra:​ ​dopamine-releasing​ ​axons​ ​to​ ​the​ ​cortex-striatum​ ​connection
● Parkinson’s:​ ​movement​ ​disorder​ ​in​ ​which​ ​this​ ​pathway​ ​is​ ​damaged,​ ​especially​ ​substantia
nigra,​ ​impairment​ ​in​ ​initiating​ ​spontaneous​ ​motion​ ​in​ ​the​ ​absence​ ​of​ ​stimuli​ ​to​ ​guide​ ​the
action,​ ​inability​ ​to​ ​control​ ​tremors,​ ​less​ ​stimulation​ ​of​ ​cortex​ ​and​ ​slower​ ​onset​ ​of
movements
● L-dopa​ ​is​ ​primary​ ​treatment​ ​for​ ​Parkinson’s,​ ​precursor​ ​to​ ​dopamine​ ​that​ ​easily​ ​crosses
blood-brain​ ​barrier;​ ​does​ ​not​ ​prevent​ ​continued​ ​loss​ ​of​ ​neurons

Sleep​ ​&​ ​Circadian​ ​Cycles
● Endogenous​ ​circannual​ ​rhythms:​ ​internal​ ​mechanisms​ ​that​ ​operate​ ​on​ ​a​ ​yearly​ ​or​ ​monthly
scale ex
...
​ ​Sleep/wakefulness,​ ​when​ ​to​ ​eat,​ ​body​ ​temp,​ ​urination
● Zeitgeber:​ ​a​ ​stimulus​ ​that​ ​resets​ ​the​ ​circadian​ ​rhythm
ex
...
​ ​½​ ​a​ ​second
​ ​ ​-K-complex:​ ​sharp,​ ​high​ ​amplitude​ ​-​ ​wave​ ​followed​ ​by​ ​a​ ​smaller,​ ​slower​ ​+​ ​wave
● Stage​ ​3+4:

-slow​ ​wave​ ​sleep​ ​(SWS)
-EEG​ ​recording​ ​of​ ​slow,​ ​large​ ​amplitude​ ​wave,​ ​slowing​ ​of​ ​heart,
breathing,​ ​and​ ​brain​ ​activity
-Highly​ ​synchronized​ ​neuronal​ ​activity

● Paradoxical/​ ​REM​ ​sleep:-rapid​ ​eye​ ​movements
-deep​ ​in​ ​some​ ​ways,​ ​light​ ​in​ ​other​ ​ways
-EEG​ ​waves​ ​are​ ​irregular,​ ​low​ ​voltage,​ ​fast
-postural​ ​muscles​ ​of​ ​body​ ​are​ ​more​ ​relaxed​ ​than​ ​in​ ​other​ ​stages
● When​ ​one​ ​falls​ ​asleep,​ ​they​ ​progress​ ​through​ ​stages​ ​1,2,3,4​ ​in​ ​order
● After​ ​~1​ ​hr,​ ​they​ ​cycle​ ​back​ ​from​ ​4,3,2,​ ​then​ ​REM
● Each​ ​cycle​ ​is​ ​about​ ​90​ ​mins
● Stages​ ​3​ ​+4​ ​sleep​ ​predominate​ ​early​ ​in​ ​the​ ​night
-length​ ​of​ ​stage​ ​decreases​ ​as​ ​the​ ​night​ ​progresses
● REM​ ​is​ ​mostly​ ​later​ ​in​ ​the​ ​night
-length​ ​increases​ ​as​ ​the​ ​night​ ​progresses
-associated​ ​with​ ​dreaming

● Reticular​ ​formation:​ ​part​ ​of​ ​the​ ​midbrain​ ​that​ ​extends​ ​from​ ​medulla​ ​→​ ​forebrain,​ ​arousal
● Pontomesencephalon:​ ​ ​-part​ ​of​ ​midbrain​​ ​that​ ​contributes​ ​to​ ​cortical​ ​arousal
-axons​ ​extend​ ​to​ ​hypothalamus,​ ​thalamus,​ ​and​ ​basal​ ​forebrain,
which​ ​release​ ​Ach​ ​and​ ​glutamate
-produce​ ​excitatory​ ​effects​ ​all​ ​over​ ​cortex
-awakens​ ​people,​ ​increases​ ​wakefulness
● Locus​ ​coeruleus

-in​ ​pons​,​ ​axons​ ​release​ ​norepinephrine​​ ​to​ ​increase​ ​wakefulness
-usually​ ​dormant​ ​while​ ​asleep

● Hypothalamus​ ​has​ ​neurons​ ​that​ ​release​ ​“histamine”​ ​(excitatory)
● Antihistamines​ ​produce​ ​sleepiness
● Orexin-​ ​peptide​ ​neurotransmitter:​ ​-lateral​ ​nucleus​ ​of​ ​hypothalamus,​ ​ability​ ​to​ ​stay​ ​awake
-stimulates​ ​Ach-releasing​ ​cells​ ​in​ ​basal​ ​forebrain
(wakefulness)
● If​ ​the​ ​pons​ ​remains​ ​in​ ​REM​ ​and​ ​the​ ​other​ ​brain​ ​areas​ ​wake​ ​up​ ​→​ ​inability​ ​to​ ​move​ ​body
● Narcolepsy

-suddenly​ ​attacks​ ​of​ ​sleepiness
-cataplexy:​ ​muscle​ ​weakness​ ​triggered​ ​by​ ​strong​ ​emotions
-lack​ ​of​ ​hypothalamic​ ​cells​ ​that​ ​release​ ​orexin​ ​(a
...
a
...
​ ​bloodstream
● Responses​ ​to​ ​Leptin:
Peripheral​ ​signal​ ​→​ ​Arcuate​ ​nucleus​ ​→​ ​paraventricular​ ​nucleus​ ​→​ ​CRH​ ​“full”
(change​ ​in​ ​leptin)

↘​ ​lateral​ ​hypothalamus​ ​→​ ​orexin​ ​“hungry”

● CRH​ ​=​ ​corticotropin​ ​releasing​ ​hormone

● MSH/​ ​CART​ ​peptides​ ​diminish​ ​appetite​ ​=​ ​anorectic
● NPY/​ ​AgRP​ ​peptides​ ​increase​ ​appetite​ ​=​ ​orexigenic
● There​ ​are​ ​other,​ ​fast-acting​ ​satiety​ ​signals​ ​that​ ​control​ ​eating​ ​over​ ​shorter​ ​time​ ​scales
● Ghrelin-​ ​peptide​ ​released​ ​from​ ​stomach​ ​into​ ​bloodstream​ ​when​ ​stomach​ ​is​ ​empty​ ​,
activates​ ​NPY/​ ​AgRP​ ​pathway​ ​(stimulates​ ​appetite)
● Cholecystokinin​ ​(CCK)-​ ​peptide​ ​released​ ​from​ ​intestines​ ​in​ ​response​ ​to​ ​fatty​ ​foods,
activates​ ​vagus​ ​nerve​ ​which​ ​then​ ​activates​ ​the​ ​MSH/​ ​CART​ ​pathway​ ​(inhibits​ ​appetite)
● These​ ​gastrointestinal​ ​(GI)​ ​cues​ ​coordinate​ ​meals​ ​over​ ​the​ ​course​ ​of​ ​hours

● Gastric​ ​fistula​ ​experiment-​ ​hole​ ​cut​ ​in​ ​stomach​ ​and​ ​the​ ​food​ ​never​ ​reaches​ ​the​ ​intestines,
so​ ​the​ ​person​ ​never​ ​feels​ ​full;​ ​this​ ​proves​ ​that​ ​CCK​ ​(peptide​ ​that​ ​signals​ ​fullness)​ ​is
produced​ ​in​ ​the​ ​intestines
● Dopamine​ ​is​ ​also​ ​involved​ ​in​ ​terms​ ​of​ ​pleasure​ ​that​ ​comes​ ​from​ ​food​ ​(leptin​ ​and
dopamine​ ​are​ ​located​ ​in​ ​same​ ​area,​ ​makes​ ​sense​ ​evolutionarily)
● Dopaminergic​ ​neurons​ ​in​ ​the​ ​VTA​ ​express​ ​dopamine​ ​receptors,​ ​and​ ​a​ ​subset​ ​of​ ​these
dopaminergic​ ​neurons​ ​contain​ ​leptin​ ​receptors​ ​that​ ​control​ ​feeling​ ​of​ ​satisfaction
specifically​ ​from​ ​food
● VTA​ ​(ventral​ ​tegmental​ ​area;​ ​associated​ ​with​ ​pleasure)
Reproductive​ ​Behavior
● “Default”​ ​program​ ​is​ ​female,​ ​and​ ​male​ ​phenotype​ ​is​ ​conferred​ ​by​ ​the​ ​SRY​ ​gene
● Sex​ ​hormones​ ​early​ ​in​ ​life​ ​bind​ ​to​ ​receptors​ ​in​ ​specific​ ​areas​ ​of​ ​the​ ​hypothalamus,
amygdala,​ ​and​ ​other​ ​brain​ ​areas:​ ​produce​ ​anatomical​ ​and​ ​physiological​ ​differences
● Female​ ​is​ ​XX,​ ​male​ ​is​ ​XY
● However,​ ​if​ ​a​ ​male​ ​has​ ​the​ ​XY​ ​gene​ ​and​ ​not​ ​the​ ​SRY​ ​gene,​ ​he​ ​is​ ​infertile,​ ​and​ ​if​ ​a​ ​female
has​ ​the​ ​SRY​ ​gene​ ​she​ ​is​ ​infertile
● The​ ​developing​ ​testes​ ​produce​ ​androgens​ ​that​ ​increase​ ​the​ ​growth​ ​of​ ​specifically​ ​male
organs
● Testes​ ​also​ ​produce​ ​Müllerian​ ​Inhibiting​ ​Hormone​ ​(MIH)​ ​which​ ​inhibits​ ​the​ ​production
of​ ​estrogen
● Females​ ​do​ ​not​ ​have​ ​the​ ​SRY​ ​gene​ ​and​ ​their​ ​gonads​ ​develop​ ​into​ ​ovaries
(egg-producing)
● Testes​ ​produce​ ​more​ ​androgens​ ​than​ ​estrogens,​ ​primarily​ ​female​ ​hormones​ ​(androgens
and​ ​estrogens​ ​are​ ​steroids)
● Organizing​ ​effects:​ ​early,​ ​sensitive​ ​stages​ ​of​ ​development​ ​(before​ ​birth)​ ​that​ ​determine
whether​ ​one​ ​will​ ​develop​ ​male​ ​or​ ​female​ ​characteristics
● Activating​ ​effects:​ ​occur​ ​at​ ​any​ ​time​ ​during​ ​life,​ ​temporary​ ​activation​ ​for​ ​a​ ​particular
response
● Sexually​ ​dimorphic​ ​nucleus:​ ​area​ ​in​ ​the​ ​anterior​ ​hypothalamus​ ​that​ ​is​ ​larger​ ​in​ ​males:
contributes​ ​to​ ​control​ ​of​ ​male​ ​sexual​ ​behavior

-example​ ​of​ ​sexual​ ​dimorphism:​ ​spinal​ ​nucleus​ ​of​ ​the​ ​bulbocavernosus​ ​(SNB)​ ​-​ ​erections
● Females​ ​have​ ​cyclical​ ​patterns​ ​of​ ​hormone​ ​release​ ​(ex
...
​ ​ ​This​ ​might​ ​be​ ​explained​ ​by​ ​different​ ​levels​ ​of​ ​vasopressin
...
​ ​increased​ ​heart​ ​rate,​ ​sweating​ ​→​ ​fear
● Anecdotal​ ​support​ ​for​ ​this​ ​theory:
-people​ ​with​ ​botox​ ​report​ ​lower​ ​levels​ ​of​ ​emotionality
-reading​ ​comics​ ​is​ ​more​ ​funny​ ​when​ ​holding​ ​a​ ​pen​ ​between​ ​teeth​ ​rather​ ​than​ ​lips
-people​ ​with​ ​pure​ ​autonomic​ ​failure​ ​(​dysfunction​ ​of​ ​many​ ​of​ ​the​ ​processes​ ​controlled​ ​by
the​ ​autonomic​ ​nervous​ ​system,​ ​such​ ​as​ ​control​ ​of​ ​blood​ ​pressure)​ ​report​ ​lower​ ​levels​ ​of
emotionality
-beta​ ​blockers​,​ ​(adrenergic​ ​antagonists)​ ​commonly​ ​used​ ​to​ ​treat​ ​heart​ ​conditions,​ ​can​ ​also
eliminate​ ​emotions
● Complex​ ​emotions​ ​are​ ​not​ ​localized​ ​to​ ​discrete​ ​brain​ ​areas
● Limbic​ ​systems​ ​-affects​ ​‘emotional’​ ​behaviors
​ ​ ​ ​-amygdala,​ ​hippocampus,​ ​thalamus,​ ​septum​ ​(pleasure/reproduction),​ ​fornix,​ ​etc
...
​ ​someone​ ​about​ ​to​ ​hurt​ ​you
-conditioned​ ​threats:​ ​cause​ ​fear​ ​after​ ​being​ ​learned ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ex

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