CNS Facts Flashcards
Where does the Lower Motor Neuron go?
Out of the spinal cord (immediately)
Effect of lesion in frontal association areas
Personality change, difficulty planning & interacting (ex: Phineas Gage)
Where does the primary axon for pain/temperature go?
Into spinal cord posterior horn & up 1-2 vertebrae
Where does the 2nd order neuron for pain/temperature synapse?
In the thalamus
Similarities between pathways for pain/temperature & discriminative touch
-1° neuron enters spinal cord posterior horn -ascends (some distance) ipsilaterally -synapses to 2nd order neuron -2nd order neuron crosses midline -ascends contralaterally to thalamus -synapses to 3rd order neuron -projects to primary (somato)sensory cortex
Effect of lesion in primary motor cortex
Paralysis (opposite side of body)
Function of CNS
saliency filter before processing for higher cognitive function
Name 4 important components of basal ganglia & pathway(s) they’re involved in
- Caudate (direct) - Putamen (direct) - Subthalamic nucleus (indirect) - GP(i) (direct AND indirect)
Dopamine mechanism
Released by reticular formation Increase arousal & rewarding behaviours Increase motivation & rewards
Location in spinal cord of nerves controlling proximal (core) muscles
medial side of anterior horn
Spinocerebellar loop (describe)
- proprioceptive info up spinocerebellar tracts - info to all structures involved with movement INCLUDES: - thalamus -> motor cortex -> spinal cord -> limb movement - spinal cord (direct) -> trunk movement
Mechanism of reticular formation action
Receive sensory stimuli, pass on to thalamus & hypothalamus, use different neurotransmitters for different responses (Part of ARAS - ascending reticular activating system)
Effect of lesion affecting serotonin production
Insomnia, anxiety, aggression
Location of primary visual cortex
very back of occipital lobe
Pigment epithelium function & location
Beneath rods & cones; black to absorb excess light & prevent interference
Location of primary sensory cortex
directly posterior to central sulcus
Proprioception: conscious or non-conscious?
may be either
Spinocerebellar loop purpose
QUALITY CONTROL of movement (feedback from limbs used to adjust signal to core & trunk)
Enteroception: conscious or non-conscious
usually non-conscious
Which part of the brain does visual recognition?
Ventral stream
Cerebrocerebellar loop purpose
FINE MOTOR CONTROL
Basal Ganglia function
Broadly influence cortex (via thalamus excitation/inhibition, modifying ongoing AP firing) to modulate voluntary movement Integrate signals
Effect of lesion in Broca’s area
Broca’s aphasia: non-fluent speech & poor syntax/grammar (comprehension intact)
What is in the inner segment of a rod/cone cell?
Cell body with lots of mitochondria
Function: indirect pathway of basal ganglia
Prevent extraneous movement (decrease motor output)
of parallel circuits in Basal Ganglia & names
3: - motor - associative - limbic
Role of prefrontal cortex in consciousness
Consider future, behavioural appropriateness, concentration Has executive control of consciousness
Fact: unlike the cerebellum, the cortex is wired differently for different functions
(Fact)
Effect of lesion in parietal association areas (right side)
Left-side spatial neglect: don’t process objects in left half of visual field
General basal ganglia pathway
Cortex Basal Ganglia (by one of the circuits) Thalamus Cortex Behaviour
Role of temporal association areas
RECOGNITION of stimuli & patterns (incl. speech, in Wernicke’s area)
Function: cerebrocerebellum (neocerebellum)
complex movement coordination, extremity & eye movement, speech
Location of thalamic reticular nucleus
outer edge of thalamus
Norepinephrine mechanism
Released by reticular formation Thalamus: increase arousal, wakefulness, attention Increase focus
Where does the primary axon for discriminative touch go?
Into spinal cord posterior horn & ascends IPSILATERALLY to the medulla
Where in the brain do the fovea project to?
BOTH left & right sides
Vestibulocerebellar loop (describe)
- balance info from vestibular apparatus - to vestibular nuclei (in brainstem) - to spinal cord for motion, AND - to cerebellum for feedback through reticular formation to spinal cord, back to vestibular nuclei
Where does the 2nd order neuron for discriminative touch go?
Crosses midline, ascends rest of brain stem antero- (contra-)laterally to thalamus
Sight transduction mechanism for in-light (8 steps)
- Photon excites rhodopsin/iodopsin - G-protein-mediated pathway - CLOSE Na+ channels - HYPERPOLARIZE - Decrease Glutamate release onto bipolar cells - Stimulate ON bipolar cells/hyperpolarize OFF bipolar cells - Stimulate ON/inhibit OFF ganglion cells - ON ganglion cell fires (more) APs, OFF does opposite
Location of primary auditory cortex
directly below central sulcus
Location of Wernicke’s area
At intersection of parietal and temporal lobes
Light-sensitive compound in rod cells
rhodopsin
Location: spinocerebellum (paleocerebellum)
vermis & anterior lobe
Body parts’ spatial representation in the primary sensory cortex is …
proportional to functionality (same as 1° motor cortex)
Rod cell location in retina
Primarily in periphery
Differences between pathways for pain/temperature & discriminative touch
Pain/temperature: 1° neuron synapses after travelling up 1-2 vertebrae (signal goes most of the way CONTRAlaterally) Discriminative touch: 1° neuron doesn’t synapse until it reaches the medulla (signal goes most of the way IPSIlaterally)
Location: Primary sensory cortex
Immediately posterior to central sulcus
Function: spinocerebellum (paleocerebellum)
synergistic extremity movement
Brain structure primarily involved with state of consciousness
Thalamus
Role of frontal association areas
- SOCIAL interactions & “humanity” (e.g. innate morality, planning, etc.) - interact with all other parts of brain - uses all hormones involved with consciousness
(Fact) Brain structures involved with consciousness are involved in reciprocal communication
(Fact)
Function: Broca’s area
(motor) production of language (use of symbols for concepts)
Cornea function
Refraction
Name the three most important primary cortices
motor, sensory, visual (also have olfactory, gustatory, auditory)
Histamine mechanism
Released by reticular formation Increase wakefulness Increase level of consciousness
Cone cell location in retina
Primarily in/around fovea
Ganglion cell function & location
Synthesize signal from layer below (bipolar cells) & pass on to optic nerve
Bipolar cell function & location
Synthesize signal from layer below & pass on; between rods/cones & ganglion cells
Where does the 3rd order neuron for discriminative touch go?
To the primary (somato)sensory cortex
Optic nerve function
Location of nerve & artery entry into eyeball; creates blind spot (no rods/cones)
Brain structure primarily involved with content of consciousness
Cerebral cortex (esp: PREFRONTAL cortex, parietal cortex)
Effect of lesion in motor association cortex
apraxia: clumsiness (bad input to basal ganglia results in bad output to 1° motor cortex)
Where does the primary axon for discriminative touch synapse?
In the medulla
Role of parietal association areas
- ATTENTION & awareness, directing focus to most salient somatic/auditory/visual input - may be directed by/direct pre-frontal cortex - right side processes spatial awareness, left side processes temporal awareness
Where do optic nerves synapse?
Thalamus LGN (lateral geniculate nucleus)
Reason for chronic inhibition of thalamus by basal ganglia
Prevents unnecessary movement, resulting in efficient, targeted motion
Effect of lesion affecting dopamine production
Indecision, inattention
Cone cell location
On top of pigment epithelium
Cerebrocerebellar loop (describe)
- cortex -> pons -> cerebellum -> (feedback) cortex via thalamus (& red nucleus, sometimes) 2. cortex -> UMN (cross midline)-> LMN for movement
Function of Motor circuit in basal ganglia
Promote measured, coordinated body & eye movement
Horizontal cell function & location
Horizontal signal integrator (temporal & spatial), help get next layer of cells to threshold; link rods/cones & bipolar cells
Areas where language is processed:
Broca’s, Wernicke’s (& Arcuate fasciculus)
Discuss the mechanism for head and neck movement to maintain visual focus.
- Sight maps to superior colliculus (past lateral geniculate nucleus) - Tectospinal tract originates in & crosses midline in brainstem - Nerves descend contralaterally to move head & neck
Effect of lesion in temporal association areas
Agnosia: inability to recognize
Function: Subthalamic nucleus
Basal ganglia indirect pathway: when excited, stimulate GP(i)
Location of primary motor cortex
directly anterior to central sulcus
Role of thalamus in consciousness
Modulates responsiveness by adjusting what does/doesn’t reach cortex: prioritizes, discriminates & relays
Location: cerebrocerebellum (neocerebellum)
posterior lobe
Rod cell location
On top of pigment epithelium
Role of thalamic reticular nucleus (input, output & function)
Input: ARAS Output: to rest of thalamus, cortex, ARAS Function: coordinate 40Hz signal to cortex for consciousness
Cerebellum lobe size increases with…
function & complexity
Body parts’ spatial representation in the primary motor cortex is…
proportional to functionality (same as 1° sensory cortex)
Lens function
Change shape to aid cornea with refraction, invert image
Location: primary motor cortex
immediately anterior to central sulcus
Brain structure primarily involved with modulating level of consciousness
Brainstem
What is in the outer segment of a rod/cone cell?
Rod/Cone portion; contain disks of light-sensitive compounds
Function: direct pathway of basal ganglia
Promote targeted, efficient movement (increase motor output)
Mechanism: indirect pathway of basal ganglia
- Subthalamic nucleus (basal ganglia component) stimulates GP(i) (basal ganglia component) - Increase thalamic inhibition - Decrease cortical excitation - Decrease motor output
Exteroception: where are receptors?
many in skin
Location of Broca’s area
in frontal lobe
Discuss the mechanism for balance compensation.
- Vestibulospinal tract descends ipsilaterally - Innervates core on same side - Innervates flexors/extensors of limbs on opposite side (crosses midline at level of synapse)
Role of cortex in consciousness
Ascribe meaning & significance (what to do)
Rod cell function
Detect motion, low acuity; function in very low-light settings (e.g. dusk/night) because very sensitive
Which part of the brain does spatial vision?
Dorsal stream
Limbic circuit pathway (basal ganglia)
Emotional processing areas Basal Ganglia Thalamus Cortex –> Motion for emotion
Function of thalamus
gatekeeper to consciousness
Targets of proprioceptive information
- cortex (conscious, travels w/discriminative touch) - cerebellum (unconscious corrections, travels up spinocerebellar tract WITHOUT EVER CROSSING THE MIDLINE - only ipsilateral)
Where does the 2nd order neuron for discriminative touch synapse?
In the thalamus
Effect of lesion in primary sensory cortex
poor localization of stimuli (not total loss of function as in paralysis)
2 components of pain/temperature signal
Localization (1° sensory cortex) “Ouch” (Limbic system, association cortices)
Acetylcholine mechanism (w.r.t. consciousness)
Released by reticular formation Activates thalamus, increasing arousal
Location: vestibulocerebellum (archicerebellum)
flocculonodular lobe & vermis
How does cross-body visual control work? (what projects where?)
Left hemisphere: right half of visual field, left-side fibers from each optic nerve Right hemisphere: left half of visual field, right-side fibers from each optic nerve
Where do optic fibers cross?
Optic chiasm
Location of anterior lobe of cerebellum
front-top
Reticular formation function
Use different neurotransmitters to influence level of consciousness and cerebral output to spinal cord
Where does the upper motor neuron go?
- Descends ipsilaterally through cortex, midbrain, pons, medulla - Crosses midline in caudal medulla if part of lateral corticospinal tract - Travels down anterior horn of lateral column of spinal cord
of functional regions in cerebellum, and names
3 (in order of development): - vestibulocerebellum (archicerebellum) - spinocerebellum (paleocerebellum) - cerebrocerebellum (neocerebellum)
Light-sensitive compound in cone cells
iodopsin (3 kinds: R, G, B)
Motor circuit pathway (basal ganglia)
Motor/Sensory cortices Basal ganglia Thalamus 1° motor cortex –> Muscle Movement
Where is motor control located in the brain?
1° motor cortex (entire body mapped to here)
Location in spinal cord of nerves controlling distal (limb) muscles
lateral side of anterior horn
Effect of lesion in arcuate fasciculus
Conduction aphasia: inability to repeat back words (language comprehension & production individually intact)
Where does the 3rd order neuron for pain/temperature go?
To the primary (somato)sensory cortex
Location of flocculonodular lobe of cerebellum
front middle: 2 flocculi, 1 on either side, and 1 nodule in center, below peduncles
Serotonin mechanism
Released by reticular formation Promotes quiet, wakefull state Feel settled, content, well
Location: primary visual cortex
Very back of occipital lobe
Amacrine cell function & location
Horizontal signal integrator (temporal & spatial), help get next layer of cells to threshold; link bipolar cells & ganglion cells
Function: direct & indirect pathways of basal ganglia, in concert
Streamline movement by balancing each other out
Where does the upper motor neuron synapse, and to what?
In the anterior horn of the spinal cord, to the Lower Motor Neuron (LMN)?
Discuss the mechanism for changing muscle tone.
- Reticular formation (in brain stem) integrates signals to determine necessary muscle tone - Controls other regions of brain stem - Lateral & medial vestibulospinal tract, & reticulospinal tract descend ipsilaterally - Cross midline at level of synapse
Function of associative circuit in basal ganglia
control cognition, as relates to motion - learn what does and doesn’t lead to goal (role decreases as learning progresses)
Location of association cortices
all of brain except for primary cortical areas
Function of limbic circuit in basal ganglia
For movement: EMOTION (facial expression, posture, etc.) & MOTIVATION (decision whether, where to move)
What is the first neuron in the transmission pathway for the motor system?
Upper Motor Neuron (UMN)
Effect of lesion affecting norephinephrine production
Low levels of arousal
Effect of lesion in Wernicke’s area
Wernicke’s aphasia: non-sensical speech, made-up words, difficulty in comprehension (fluency, syntax, grammar, word structure intact)
Function: vestibulocerebellum (archicerebellum)
trunk control
Function: Caudate & Putamen
Basal ganglia direct pathway: when excited, inhibit GP(i)
of lobes in cerebellum, and names
3: - anterior - posterior - flocculonodular
Cerebellum function (general)
Modulate/adjust firing of Upper Motor Neurons based on internal & external factors
Location of posterior lobe of cerebellum
middle/back-top, front-bottom
Function of basal ganglia
control movement by controlling cortical output
Mechanism: direct pathway of basal ganglia
- Cortex excites caudate & putamen (basal ganglia components) - inhibit GP(i) (basal ganglia component) - decrease thalamic inhibition - increase cortical excitation - increase motor output
Thalamus is under _______ _______ by the basal ganglia
chronic inhibition (release-inhibition model: incr/decr inhibition to modulate movement)
Function of limbic system
Emotion & saliency filtering
spinal tracts most be coordinated so that core movement compensates for limb movement on the opposite side of the body (fact)
(fact)
Motor system function
Control limb movement, posture, core, balance, etc.
Where do enteroceptive signals go?
cerebellum
Function: Wernicke’s area
(sensory) language comprehension
Where does the 2nd order neuron for pain/temperature go?
Crosses midline, ascends in antero- (contra-)lateral system to brain stem (modulation), to thalamus
Effect of lesion affecting histamine production
Drawsiness
Associative Circuit pathway (basal ganglia)
Frontal/temporal lobe Basal Ganglia (Spinal cord, if necessary) Thalamus Cortex (FEEDBACK) –> Learning
Cone cell function
Detect colours, provide high visual acuity; require large amounts of light
Function: GP(i)
Basal ganglia pathways: when excited (indirect), increase thalamus inhibition; when inhibited (direct), decrease thalamus inhibition
Organization of primary sensory cortex
Strips parallel to central sulcus are linked to different types of receptor (e.g. muscle, skin, joints; rapidly-, slowly-adapting)
Where does the primary axon for pain/temperature synapse?
1-2 vertebrae above where it enters the spinal cord
Vestibulocerebellar loop purpose
BALANCE (stabilize trunk, stabilize image on fovea)
Effect of lesion in sensory association cortex
Tactile agnosia - can’t make sense of stimuli Astereognosis - can’t identify objects in hand
Effect of lesions in basal ganglia
Inhibit desired motor output (affecting direct pathway) or prevent suppression of superfluous movement (affecting indirect pathway)
