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290 Cards in this Set

  • Front
  • Back
what is stereognosis
ability to perceive the form of an object using touch
what is graphestheisa
ability to recognize writing on skin purely by the sensation of touch
what is the clinical term for a type of sensation
modality
a patient is experiencing extreme pain who smiles and enjoys it, has an inappropriate expression of what
affect
if a person has complete loss of sensation in a part of the skin, where will the lesion be
Peripheral (PNS)
when a person experiences loss of one sensory modality, where will the lesion be
central (CNS)
what differentiates a tract from a pathway
a tract is a bundle of axons with a common origin, course, and destinations, whereas a pathway is a series of synaptically linked neurons that share a common function; tracts are often included as parts of pathways
what distinguishes sensory info from afferent info
sensory info is consciously experience, wherease afferent info contains both conscious and subconscious input
what do the medial division fibers consist of and what do they initially run into when entering the spinal cord
large, myelinated fibrer
enter into the fasciculus gracilis or cuneatus
what do the lateral division fibers consist of and what do they initially run into when entering the spinal cord
small, unmyelinated fibers
enter into the dorsolateral sulcus
After a sensory axon enters the spinal cord, what normally occurs and how does this differ b/w medial and lateral division fibers
it bifurcates into an ascending and descending branch
medial divions: long ascending and short descending with collateral innervation of 6-8 segments
lateral division: short ascending and short descending with collateral innervation to 2-3 segments
what fibres distribute mainly to the posteromarginal nucleus, substantia gelatinosa, and the neck of the dorsal horn
lateral division fibrs

vs. the medial division fibers which have a much more widespread distribution
what functions are the medial division fibers associated with
movement reflexes, stretch reflexes, and fine localization of touch

vs. lateral division fibers carrying pain and temperature
what are the possible effects of a single spinal afferent
reflexes (via spinal cord)
perception (via thalamus/cortex)
"subconscious" data (via brainstem/cerebellum)
what is the cutaneous innervation associated with C1
nothing
starts at C2-back of head
what spinal cord segments provide cutaneous innervation to the neck
C3, 4 (shoulders are C5)
where do 1st, 2nd, and 3rd order afferents originate and terminate
1st: PNS --> DRG --> Spinal cord/brainstem

2nd: SC/BS --> crosses midline --> VP nucleus of the thalamus

3rd: VP nucleus --> PLIC --> cortex (area 3, 1, 2)
what are examples of rapidly adapting receptors
meissner's corpuscles
pacinian corpuscles
merkel's discs
ruffini corpuscles
what modalities are carried in the DCML parthway and which is unique to it
fine touch
conscious proprioception
vibration**
which division fibers are associated with DCML and in what nuclei will the 1st order synapse
medial division afferents
travel in fasciculus gracilis and cuneatus and synapse in their respective nuclei
Where do the second order neurons of the DCML pathway cross over and where do they project to?
at the medial leminiscus (immediately after leaving the nucleus gracilis and cuneatus) and project to the VPL nucleus
Where do the 3rd order neurons of the DCML pathway project to, specifically
primary sensory cortex (S1)
Below midthoracic level, into what fasciculations do axons of the DCML enter
fasciculus gracilis
after crossing over, what do the 2nd order neurons of the DCML travel in
medial lemnicus
where in the VPL do axons from the nucleus gracilis and cuneatus synapse, respectively
gracilis - lateral
cuneatus - medial
after leaving the lateral part of the VPL, where in the cortex do signals from the lower extremitiy synapse
medially (in the somatopic map - S1)
if a patient has a lesion in the medial part of the medial lemniscus, where would the deficit be
in the contralateral side of the upper extremity
on the somatopic map, what two sections separate the angle at the midline which separate the supply of MCA from ACA
angle - hip and knee
MCA/ACA - trunk and hips
what kind of touch is esp important in the DCS
time coded touch (graphesthesia/stereognosis)
what does a loss of vibration indicate
a lesion in the DCML (almost exclusively)
Which modalities are located in the ALS
pain
temperature
crude touch/pressure
Which fibers are found in the ALS
Adelta dibers (small, myelinated)
C fibers (small, unmyelinated)
What type of axonal endings (receptors) are associated with the ALS
undifferentiated (naked nerve endings)
where do Adelta and C fibers of the ALS enter the spinal cord and where do they initially travel to
enter in the lateral division of the dorsal root
ascend and descend for 1-3 segments in the dorsolateral tract (Lissauer's tract) to synapse in the dorsal horn
Where in the dorsal horn do the Adelta and C fibers synapse
Adelta: laminae I (posteromarginal nucleus) and V (nucleus proprius)
C: lamina I and II (substantia gelatinosa)
Where do the 2nd order neurons of the ALS decussate and where do they ascend
in the ventral white commissure at approx their level of origin and ascend in the ALS tract
What distinguishes the ALS from the DCML system when looking at 2nd order neurons
the 2nd order neurons of the ALS do not all go to the VPL thalamus, but split off earlier in the brainstem to synapse in mult. areas of the brain and they decussate at different level
to what areas do the 2nd order neurons of the ALS send their axons to
reticular formation
PAG
intralaminar nucleus of the thalamus (CM - centromedian)
VPL (main pathway)
what is found b/w the 1st and 2nd order neurons of the ALS and what is its purpose
an interneurons - modulates input (reduces pain)
how do the axons of the ALS distribute somatotopically
same as those of the DCML but less defined (only counts for the spinothalamic division - those going through the VPL)
How do fibers of the ALS running into the PAG function
they synapse on neurons that descend and cause release of serotonin from the raphe nuclei, which subsequently causes inhibition of 2nd order neurons of the ALS (i.e. it has an analgesic role)
complete unilateral loss of pinprick sensation can be caused by what
a lesion of the ALS in the upper spinal cord/ brainstem in the contralateral side
what type of deficits are caused by damage to the ALS
deficits in pinprick sensation, temperature, itch/tickle, and sexual sensations
what is the DRG a homolog to in the trigeminal system
sensory ganglia of CN V and the mesencephalic nucleus
what is the spinal homolog to the cheif sensory nucleus of V
dorsal column nuclei (nucleus gracilis and cuneatus)
What are the homologs in the spinal system to the spinal trigeminal nucleus and tract
spinal trigeminal nucleus: laminae I/II in the dorsal horn (posteromarginal nucleus and substantia gelatinosa)
spinal trigeminal tract: dorsolateral funiculus
how do pain and temperature sensation from the face reach the spinal trigeminal nucleus
from the receptor they travel through a ganglion and descend in the spinal trigeminal tract to the spinal trigeminal nucleus
after crossing the midline fairly quickly, in what tract do the 2nd order neurons of the trigeminal pain pathway travel and where do they synapse
VTTT and synapse in the VPM nucleus
how do the locations where the 2nd order neurons conveying pain and temp input synapse differ, regarding body and facec
VPL: body
VPM: face (think of general somatotopic arragments)
What do the 3rd order neurons of the trigeminal sensory pathway travel through and where do they synapse
travel through the PLIC to synapse in S1 (lateral portion) goes for pain, temperature, touch, and pressure
where do most of the pain pathways of the trigeminal nerve travel to before synapsing
the caudal 1/3 of the medulla
where do the 1st order neurons of touch and pressure pathways of the face have their cell bodies and where do they synapse
cell bodies in the trigeminal ganglia
synapse in the cheif sensory nucleus of CN V
in what tract do decussation axons from 2nd order neurons of touch and pressure pathway of CN V travel and where do they synapse
travel in VTTT
synapse in VPM
how do the pathwats of 2nd order neurons of touch and pressure modality of CN V different from the rest of the body
besides decussating and traveling in VTTT, some neurons remain ipsilateral and travel in DTTT to synapse on VPM
why is pinprick sensation a more reliable modality than touch and pressure in the face
b/c ALL pain fibers cross over whereas some touch and pressure fibers do not
what type of neurons are involved in proprioception of the face and where are their cell bodies located
pseudounipolar neurons - cell bodies in mesencephalic nucleus
what differentiates visceral sensation from somatic sensation
afferents, perception, and innervation (density) is different; CNS pathway is bilateral; pain is often referred
Does the NS have the capacity to create new information
no, it can only process it
how does the concept of entropy relate to the NS
in the process of transmitting information, some is always lose
where is the neuron does most of the information processing occur
axon hillock
what is the purpose of having interneurons
they aid in the processing of information
even though the individual neuron is slow, what aspect of the NS causes info processing to be fast
its parallel nature (many cells working at the same time)
what differentiates b/w transduction and representation
transduction: link b/w physical stimulus and input tp nervous system

representation: link b/w nervous system and preception
What type of potential is the receptor and how it is referred to
graded potential

referred to as a generator potential (since graded potential is genereated at sensory endings of axon)
Besides the receptor potential, what is another example of a graded potent
synaptic potential
What is the concept called which states that the receptor potetial amplitude is proportional to the number of open channels (caused by stimulus)
Amplitude modulation (AM)
how does stretching a muscle induce an action potential in the muscle spindle
when stretched, tethers b/w the ions channels induce a conformational change allowing the passage of ions
Where are action potentials usually generated at sensory terminals
at the trigger zone (first node of Ranvier)
what type of channels are found in the trigger zone of sensory terminals
voltage-sensitve channels
What does AM-FM conversion refer to
the conversion of a sensory stimulus to an action potential
What happens when the amplitude of a stimulus is increased
the frequency of action potentials increase
How does the firing rate differ when a static stimulus is applied to either a slow-adapting or fast-adapting receptor
slow-adapting: fires continuously

fast-adapting: only fires when the stimulus is applied and when it is removed
How can a continuous stream of action potentials be genereated in a fast-adapting receptor
the intensity of the stimulus must be constantly changing
What type of conversion happens at the synapse
FM-AM conversion
What happens when the action potential frequency (FM) increases at the synapse
more neurotransmitter is released (which determines the AM via the number of channels opened)
What does computation refer to regarding action potentials
the processing of various PSPs coming from different sources to determine action potential frequency
how are sensory systems segregated
by modality (vision, hearing, touch, etc)
What is meant by calling an axon a labeled line
stimulation of that axon will signal the type, location, and amplituse of the stimulus to the cortex (i.e. make us aware of its modality, location, and strength)
Which type of receptor is good for coding the intensity of a stimulus
slow-adapting (or tonic) receptors
When does the rapidly-adapting receptor fire
when the stimulus changes (always when the amplitude increases, and sometimes when it decreases)
Which type of receptor allows extraction of dynamic information regarding the stimulus (i.e. velocity and acceleration)
rapidly-adapting receptor
What type of response do the Pacinian corpuscle and the free nerve ending exert, respectively
Pacinian: rapidly-adapting

Free nerve ending: slow-adapting
Why is the range of the stimulus intensity that we can perceive limited
b/c each receptor has a physiological range of intensities at which it can response, and once the stimulus goes outside that range we can no longer preceive it
How does the CNS judge stimulus intensity
by looking at how many axons are firing due to a particular stimulus
What determines the receptive field of a particular sensory neuron
the area of skin which will elicit discharge in that central neuron
how are the receptive fields represented in the cortex
axons with adjacent RFs in the skin will also have adjacent projections and connections in the sensory cortex
What tells the CNS where the RF of a certain sensory neuron is located?
NOT the location in the sensory cortex, but the labeled line
What are derivative sensations and what are some examples of them
sensations derived from multiple primary sensations (modalities)

includes wetness, tickle, itch
Which two sensory fibers types have the fastest conduction and why
Aalpha and Abeta, because they have the largest diameter and are myelinated
Which two sensory fibers types have the slowest conduction and why
Adelta and C, because they have the smallest diamter
What differentiates C type fibers from A type fibers
C type fibers are unmyelinated and smaller
Which motor fiber type is unmyelinated
Type IV (all other myelinated with Type I being the fastests, then II, then III)
What fibers are associated w/ touch and which with pain/temperature
Touch: Aalpha and Abeta

Pain/temp.: Adelta and C
How are different sub-modalities represented in the somatosensory map
they are intermingled by segregated to some extent as the level of the individual neurons
What is acuity and how is it measured clinically
a measure of sharpness of resolution

determined by measured the two-point discrimination threshold (and taking the reciprocal)
What two factors determine the acuity at a point on the skin
receptive field size

number of RFs contacted by the stimulus
Which will have a higher innervation density, the finger or the arm, why
the finger since it has many more sensory axon RFs contacted by the stimulus
What types of stimuli are transmitted by nociceptive axons
potentially tissue-damaging stimuli (not by exacerbated touch, vibration, or temp)
How do the conduction velocity and duration of the stimulus differ b/w Adelta and C fibers
Adelta: fast, pain lasts only the duration of the stimulus

C: slow, pain outlasts the duration of the stimulus
What type of nociceptive stimuli are carried by Adelta and C fibers, respectively, and how does their onset differ
Adelta: sharp, buring, but tolerable pain, with a rapid onset

C fibers: dull, aching, intoleravle pain with a slow onset
Which type of pain has central representation similar to that of touch and which does not
Fast pain: well localized just like touch

Slow pain: not well localized, since it is relayed polysynaptically and through nonspecific nuclei of the thalamus leading to widespread coritcal representation
How does morphine exemplify the difference b/w pain and nociception
patients can still identify that the stimulus is noxious (still havs nociception) but the affect of pain is missing
What sets phantom pain, carpal tunnel syndrome, and trigeminal neuralgia apart from most forms of pain
they are not caused by tissue damage
lesions in what part of teh NS cause extreme, excruciating pain
thalamus
what is the cause of referred pain
convergence of cutaneous and visceral info onto the same neuron
how does central pain come about
chronic nociceptive input can cause pain cells in lamina V to become spontaneously active, producing central pain
what is the best way to prevent both chronic pain and addiction in cancer or burn patients, requiring morphine
use a carefully controlled systemic drip as opposed to a patient controlled drip
which types of surgical innervation for pain relief give the patient profound, by transient relief
dorsal rhizotomy
anterolateral tractotomy
what is the mechanism by which morphine analgesia works
binds to the same receptors as endogenous opoids such as endorpins, enkephalins, and dynorphins
how does activation of endogenous opoid receptors decrease pain
afferents activate neurons in the PAG, these project to the medullary nucleus raphe magnus and nucleus reticularis gigantocellularis whose descending axons cause inhibition of pain
by what mechanism do the descending axons from the medullary nucleus raphe magnus cause inhibition of pain
axons synapse to excite interneuons on the spinal cord (through 5-HT) which in turn causes the inhibition of C fibers by secreting enkephalin
by what mechanisms do the descending axons of the nucleus reticularis gigantocellularis cause inhibition of pain
axons synapse to excite interneurons in the SC (through NE) which in turn cause inhibiton of thalamic projectio neurons of the ALS through a non-opoid polysynaptic pathway
what mediates stress-induced analgesis
thalamic and cortical projections to PAG
what is the mechanism by which gate control inhibits pain
stim of large diameter fibers (by rubbing skin) excites interneuons which in turn have an inhibitory effect on C fiber synaptic transmission (thus inhibiting pain)
what types of clinical applications use the gate control concept to manage pain
acupuncture/acupressure
dorsal column stimulation
transcutaneous electric nerve sitmulation
What is it called when a single afferent neuron splits to synapse on multiple interneurons
divergence

(vs. convergence)
what is the mechanism called by which a reflex pathway be inhibited through higher centers
gating
what are the two types of gating control mechanisms and how does each work
gating by interneurons: descending control signal directly inhibits interneuron

gating by presynaptic inhibition: descending control signal causes presynaptic inhibition of excitatory input into the interneuron/motor neuron
by what mechanism can a single stimulus cause a reflex, that far outlasts the stimulus itself
reverberating circuits: interneurons synapse on each other, creating a circle that continuously activates itself and the motor reflex
How does the spinal cord maintain the rhythmic alternating activity (half-center model) as seen in walking
both flexors and extensors are stimulated simulataneously, but inhibitory interneurons allow only one of the antagonisitic muscle groups to contract at once; when the inhibition of one group dies out the antagonisistic muscle group will contract, until the cycle repeats itself
how is stiffness of the joint generated, as in holding a heavier object
normally, contraction of flexors causes the extensors to relax; but by causing inhibition of the Ia inhibitory interneuron innervating the extensors, dual contraction is possible and stiffness in the joint is generated
what is the interneuron called that creates a negative feedback loop b/w a motor neuron and itself
renshaw cell (inhibitory interneuron) - prevents muscular damage from tetanus
what does stimulation of the renshaw cell cause
inhibition of the agonisitc muscle group and disinhibition of the antagonist muscle group
what are the three negative feedback systems that control muscle stretch, muscle forece, and firing rate of motor neurons
stretch: muscle spindle

force: golgi tendon organ

firing: renshaw cell
which internuron has a larger number of convergence inputs, making it a very important integrating system for motor imput
Ib inhibitory interneurons (receives input from Ib afferents, joint afferents, cutaneous afferents, and descending pathways)
when pinching skin on the ventral aspect of the leg, which muscle group contracts and which is inhibited
anterior group (underlying pinched skin) contracts while the posterior group is inhibited
when stepping on a nail with the right foot, interneurons innervating what muscles are excited
excitationn if right flexors and left exntensors; inhibition of right extensors and left flexors
what happens to the scratch reflex when the stimulus generating the reflex is increased in intensity
both amplitude and duration of the scratch reflex is increased (but rhythm remains constant)
what occurs when the intensity of stimulation of the mesencephalic locomotor region is increased in a walking animal
speed of movement increases with increased stimulus (from slow walk to gallop)
where is goal-directed locomotion generated
in supraspinal systems
what differentiates the comatose patient with a lesion to the upper brain stem from one with a lesion to the cortex in comparing their response to a noxious stimulus
upper brain stem: decebrate posture (arms extended)

cortex: decorticate posture (arms flexed)
what types of movement are generated by the cortex and spinal corrd
cortex: voluntary movement

spinal cord: reflex response and rhythmic motor patterns
what charachterizes rhythmic motor patterens and what are some examples
initiation and termination are voluntary, but the on-going sequence is stereotyped

e.g. walking, running, chewing
What two systems are used to regulate slow and rapid movements
slow movements: negative feedback systems (does NOT use advance inforamtion)

Rapid movments: feedforward control system (use advance information)
What are the two main types of intrafusal muscle fibers found in the muscle spindle and what are their subtypes
Dynamic: dynamic nuclear bag fibers

Static: static nuclear bag fibers and static nuclear chain fibers
What type of afferent axons are associated with the static intrafusal muscle fibers
Type II (whereas type Ia axons are associated with both static and dynamic intrafusal fibers)
What are the efferent axons associated with the intrafusal muscle fibers
dynamic gamma motor axon

static gamma motor axon
Where is the golgi tendon organ located and in what fashion
b/w the tendon and the muscle, connected in series to the muscle

(vs. the muscle spindle being connected in parallel)
by what mechanism does the golgi tendon organ generate an AP
stretching of the muscle causes the encapsulated organ to lengthen, and in effect causes the Ib afferent axons to become compressed by the collagen fibers that comprise the golgi tendon organ
What aspect of the muscle contraction does the golgi tendon organ register
muscle force


(vs. the muscle spindle registering muscle length)
What happens to the frequency of APs generated by the muscle spinsle and golgi tendon organ when a muscle contracts
muscle spindle: decreases (since muscle length decreases)

GTO: increases (since the force on the muscle increases)
What happens to the frequency of APs generated by the muscle spinsle and golgi tendon organ when a muscle stretches
both increase, but that of the muscle spindle does so to a greater extent (b/c length increases more than force)
When a muscle undergoes stretch, what happens to the frequency of APs registered at the Type Ia and tpye II axons of the muscle spindle
Type Ia: increase drastically (since it reads both static and dynamic changes)

Type II: simple decrease in AP frequency
When a muscle contracts (via stim of alpha motor neurons), what prevents the muscle spindle from becoming limp
simultaneous firing from gamma motor neurons causing the muscle spindle to contract, thus allowing it to continue registering muscle length
how does the firing frequency of type Ia axons differ when either the static or dynamic gamma fibers are stimulated
static gamma fibers: baseline firing frequency increases, everything else remains the same

dynamic gamma fibers: baseline does not change much, but firing frequency during dynamic phase is greatly enhanced
how does stimulation of dynamic gamma motor neurons cause an increase in sensitivity of the dynamic nuclear bag fibers
the dynamic gamma motor neurons innervate the polar regoin of a fiber, causing teh ends of the fiber to become more viscous and thus less stretchy; the central regions, where Ia axons are located, wii therefore experience more stretch
What is the difference in firing frequency of the static and dynamic gamma motor neurons when comparing fast walking and imposed movments
Fast walking: high static/low dynamic

imposed movement: low static/high dynamic

beam walking: high static/high dynamic
When a type Ia axon from a muscle spindle enters the spinal cord, what does it synapse on?
an excitatory neuron of the homonymous muscle, an excititatory neuon of a synergistic muscle, and an inhibitory neuron of an antagonistic muscle
by what mechanism does the inverse myotatic reflex work
- muscle contraction increases the force generated by the muscle; this leads to increased firing frequency of type Ib afferents via the goligi tendon organ; type Ib afferents synpase on inhibitory interneuons in the spinal cord causing inhibition of muscle contraction; the type Ib afferents also synapses on excitatory interneuon innervating the antagonisitic muscle
Tracts in which part of the brainstem act on flexor-biased muscles
lateral parts

(vs. medial for extensor)
which corticies add to the descendin corticobulbospinal tracts
primary motor cortex
primary sensory cortex
premotor cortex (supplementary motor area)
posterior parietal cortex
what parts of the body does the corticobulbar tract innervate
head and face
which corticospinal tract innervates the axial musculature
ventral

(vs. lateral innervating the appendicular muscle)
What is the key distinction b/w the sensory and motor homunculi
the motor homunculus has a larger representation of for the hand
where in the internal capsule do the motor tracts innervating the head and neck travel
corticobulbar tracts run through the genu of the internal capsule
where in the internal capsule do the corticospinal tracts travel
PLIC
which arteries supply most of the internal capsule and which supplies only the ventral part of the posterior limb
most if the IC: medial and lateral striate arteries

ventral PL: anterior choroidal
Where do corticospinal fibers decussate
at the pyramidal decussation
After decussating, in what part of the spinal cord do the lateral corticospinal fibers travel?
lateral funiculus
How does the path of the ventral corticospinal fibers differ from those of the lateral corticospinal fibers?
ventral fibers do not decussate, travel in the anterior funiculus (vs. lateral), and terminate on the medial motor cell groups (vs. lateral)
What differentiates upper motor neurons from lower motor neurons
lower motor neurons connect directly to the muscle

upper motor neurons then, lie proximal to the LMN
What is the major tract associated with upper motor neuron disease
corticospinal tract
What changes in reflexes are seen in upper motor neuron disease?
increased muscle stretch reflex
Babinski/Bing sign present
Abdominal/cremasteric reflexes not present
Which motor neuron disease is associated with spastic weakness and clonus
UMN disease
What word defines a series of involuntary muscular contractions due to sudden stretching of the muscle?
clonus
What is characteristic of a Hoffmann's sign?
flicking the terminal phalanx of the third or fourth finger causes flexion of the terminal phalanx of the thumb and/or index finger
What type of gait is seen frequently following stroke (and is also associated with upper motor neuron disease)?
hemiparetic gait (weakness on one side while walking)
Where does the corticorubral tract terminate?
red nucleus

vs. corticoreticular tract terminating in the reticular formatoin
What type of lesion is associated with one-sided drooping of the lower face?
corticobulbar lesions (contralateral side)
Which motor tract travels close to the lateral corticospinal tract and is thus flexor-biased?
rubrospinal tract
What type of movement is associated with the rubrospinal tract?
voluntary, fine activity of distal extremities; coarser activity of proximal flexors
Damage to which spinal tract causes hand movements to become clumsy?
rubrospinal tract
After taking away all of the nuclei and tracts in the brain stem, what is left?
reticular formation
Which tract carries out reflexive control of posture?
reticulospinal tract
Which reticulospinal tract is flexor-biased and which is extensor-biased?
flexor-biased: medullary reticulospinal tract

extensor-biased: pontine reticulospinal tract
Which spinal cord tracts maintain posture and reflexes by controlling the midline extensor muscles, and how does each accomplish this specifically?
lateral vestibulospinal tract: keeps center of gravity b/w feet

medial vestibulospinal tract: provides a stable platform for the eyes (cervical levels only)
Where does the tectospinal tract originate and what is its function?
superior colliculus: helps coordinate eye and head movement
Which tract is located all around the spinal cord gray matter and what is its function?
propriospinal tract: coordinate activity of axial and distal musculature
Which motor nuclei are interconnected with long propriospinal neurons and which with short propriospinal neurons?
long: medial motor nuclei

short: lateral motor nuclei
What types of muscle paralysis are associated with upper motor neuron disease and lower motor neuron disease, respectively?
UMN: spastic paralysis

LMN: flaccid paralysis
What clinical signs are associated with lower motor neuron disease?
flaccid muscle weakness / paralysis
muscle wasting
decreased or absent MSR
muscle fasciculations/fibrillations
sensory deficits (stocking/glove; following dermatomes or parts of dermatomes)
What are poliomyelitis and amyotrophic lateral sclerosis (ALS) examples of?
LMN
What does damage to CN VII (nucleus of nerve) lead to?
Bell's Palsy
What causes Brown-Sequard syndrome and how does it present clinically?
lateral hemisection of the spinal cord: leads to ipsilateral loss of vibration and proprioception, and contralateral loss of pain and temperature (also ipsilateral spastic paralysis)
What types of muscle paralysis are associated with upper motor neuron disease and lower motor neuron disease, respectively?
UMN: spastic paralysis

LMN: flaccid paralysis
What clinical signs are associated with lower motor neuron disease?
flaccid muscle weakness / paralysis
muscle wasting
decreased or absent MSR
muscle fasciculations/fibrillations
sensory deficits (stocking/glove; following dermatomes or parts of dermatomes)
What are poliomyelitis and amyotrophic lateral sclerosis (ALS) examples of?
LMN
What does damage to CN VII (nucleus of nerve) lead to?
Bell's Palsy
What causes Brown-Sequard syndrome and how does it present clinically?
lateral hemisection of the spinal cord: leads to ipsilateral loss of vibration and proprioception, and contralateral loss of pain and temperature (also ipsilateral spastic paralysis)
After the acute phase following transection of the spinal cord, which functions return to normal?
Flaccid paralysis, no spinal reflexes, drop in BP, no vascular or visceral reflexes
After the acute phase following transection of the spinal cord, which functions return to normal?
BP, vascular/visceral reflections, reactions of extensor muscles
What happens to MSRs below the level of the transected spinal cord section in the chronic state?
increased response (due to the lack of inhibtion from higher centers)
How does the latency differ between the muscle proprioceptors and vestibular/visual receptors?
proprioceptors: 70-100 msec

vestibular/visual: 140-200 msec

stretch reflex latency: 50 msec
Which muscles respond, and in what order, when the platform with a person standing on it moves backwards?
Gastrocnemius --> hamstrings --> paraspinals

distal to proximal

(vs. anterior tibialis --> quadriceps --> abdominals when moving forward)
By what mechanism are adjustments to posture made when comparing expected and unexpected disturbances?
expected: feed-forward system makes postural adjustments prior to disturbance

unexpected: feedback system corrects for postural adjustment after the disturbance
What does the vestibulocollic reflex do?
keeps the head stable by counteracting head movements
Which reflex contracts limb muscles to counteract sway of the body?
vestibulospinal reflex
If vestibular reflexes are destroyed, which reflexes become predominant?
Neck reflexes (cervicocollic reflex/ cerviospinal reflex)
In the cervicospinal reflex, what does bending the neck forward elicit?
flexion of the upper extremities
Which nuclei facilitate motor neurons to axial muscles and extensor muscles?
Pontine reticular nuclei
Which nuclei facilitate flexor motor neurons, inhibit back and neck motor neurons, and inhibit limb extensor motor neurons?
medullary reticular nuclei
Which structure integrates vestibular and other sensory inputs with voluntary motor commands from the cortex?
reticular formation
What type of posture is associated with a lesion above the red nucleus?
decorticate posture (flexion)
In a lesion below the red nucleus, what is found clinically and how is this treated?
hyperextension of the extremities

treated by cutting the dorsal roots
Which posture in comatose patients carries a better prognosis?
decorticate
What is the term that describes the use of different motor strategies to achieve the same end-result?
motor equivalence

(e.g. writing on paper and blackboard = different muscle groups, but same end-result)
Which processes associated with voluntary movements occur in the posterior parietal cortex, premotor area, and primary motor cortex, respectively?
posterior parietal cortex: integrates sensory inpit

premotor area: planning

primary motor cortex: performs movement
Which neuron actually send the motor signal from the cortex to the alpha motor neuron in the spinal cord?
pyramidal neuron running through the corticospinal tract (= pyramidal tract)
In the case of an S1 disk herniation, which motor neuron can be affected?
LMN (alpha motor neuron)
What is the purpose of transcranial magnetic induction?
test the CST for functionality (causes discharge of pyramidal neurons)
How does the result of a fMRI differ when comparing a sequential and non-sequential finger sequence?
Sequential: visible in motor cortex

Non-sequential: also involves supplemental motor cortex
How does the concept of divergence relate to the pyramidal neuron?
one pyramidal neuron can innervate several muscles (regarding a single joint)

convergence states that many pyramidal neurons are needed to forcefully contact a muscle
What concept, regarding cortical representation of muscles, allows for the creation of a wide variety of muscle synergies?
the overlap and intermingling of cortical motor cells innervating synergisitc muscles (i.e. those in the hand)
Which muscle groups, in general, respond to corticospinal neuron firing?
flexors
What aspect of muscle contraction is the red nucleus associated with?
dynamic force (speed of movement)
Which population of motor neurons encode the direction of movement?
M-I neurons (each neuron fires when movement is in their preferred direction)
Which muscles and what types of movement are associated with the primary motor cortex?
distal muscles and fine digital movement
Which area of the cortex controls conditioned and skilled movements?
primary motor cortex
What is the function of the premotor area?
receive sensory input from the posterior parietal cortex; then preparse M-1 for the impending motor act (=planning)
What does the length of the readiness potential preceding a motor act depend on?
complexity of the motor act
When a person is asked to do a mental rehearsal of a finger movement sequence, which cortical area is stimulated?
Supplemental motor area (SMA) - vs. both SMA and M-I when actual sequence is performed
What does a unilateral lesion of the SMA lead to?
deficit in coordinating the use of both hands
Which Brodmann's areas provide sensory input to the posterior parietal cortex?
Area 5 (proprioception)

area 7 (visual and auditory)
How does sensory information in the cortex reach M-I?
from area 5 to area 7 (integration); then on to the premotor cortex (planning); and into M1 (execution)
What is the purpose of area 7's projection to the lateral cerebellum?
provides it with sensory information used to correct actions during target orientation movements
In general terms, how do the basal ganglia exert their effect on motor output?
indirectly, by modifying the activity of corticobulbospinal tract
What are the two major functions associated with the basal ganglia?
initation of voluntary movement

inhibition of involuntary movement
Which components of the basal ganglia are part of the lenticular nucleus, (neo)striatum, and corpus striatum, respectively?
lentiform: putamen + GP

striatum: caudate + putamen

Corpus striatum: caudate + putamen + GP
What are the receptive elements of the basal ganglia and from where do they receive input?
putamen and caudate: receive input from all areas of the cerebral cortex
How does the cortical input differ between the putamen, head of the caudate, and body/tail of the caudate?
Putamen: motor functions

head of caudate: frontal lobes limbic areas

body/tail of the caudate: parietal/occipital/ temporal lobes
Which part of the basal ganglia is responsible for the emotional disturbances associated with basal ganglia disorders?
head of the caudate (since ot receives input from the frontal lobe and limbic areas)
How do the direct and indirect pathways of the basal ganglia differ?
direct: putamen --> GPm

indirect: putamen --> GPl --> STn --> GPm
Which substance has a profound modulatory influence on the putamen and caudate, and where is this substance produced?
DA - produced in the pars compacta of the substantia nigra
How do the caudate and putamen downregulate the activity of the substantia nigra?
intranuclear connections exist b/w the caudate and putamen with the pars reticulata of the substantia nigra that exert an inhibitory effect through GABA and substance P
After input into the basal ganglia converge on the medial globus pallidus, where do the major projections travel to?
VA/VL and CM of thalamus
Through which structures do outputs from the medial globus pallidus exert an effect on eye movements and posture?
superior colliculus and reticular formation
By what mechanism does the DIRECT pathway of the basal ganglia generate excitatory effects on the cortical motor areas?
through disinhibition (i.e. inhibiting the inhibitory effects on the VA/VL)
By what mechanism does the INDIRECT pathway of the basal ganglia generate excitatory effects on the cortical motor areas?
through inhibition (i.e. by inhibiting the excitatory effects of the STn on the inhibition of the VA/VL)
Besides modulation of movement, what other areas do the basal ganglia affect?
cognition
reward
mood regulation
When a disorder is present affecting the prefrontal channel or limbic channel of the basal ganglia, respectively, what function is impaired?
prefrontal channel: cognition

limbic channel:emotion/affect
What are the basal ganglia input nuclei and cortical output nuclei associated with the limbic channel?
input: nucleus accumbens, ventral caudate, ventral putamen

output: anterior cingulate, oribital frontal cortex
What two structures make up the thalamic fasciculus and how are the pathways of these two structures different?
Ansa lenticularis: from GPm it hooks around the IC to the VA/VL

Lenticular fasciculus: from GPm through IC to VA/VL
Which involuntary movements are associated with basal ganglia disease?
tremors
athetosis (writhing motions)
chorea (abrupt movements)
hemiballismus (violent flailing of limbs)
dystonia (persistant distorted position)
What causes hemiballismus?
subthalamic lesion
What is the difference between akinesia and bradykinesia?
akinesia: difficulty initiating movements

bradykinesia: slowness in executing movements
By what mechanism does a lack of dopamine cause decreased excitation of the premotor cortex in Parkinson's?
a lack of DA causes diminished inhibition of the GPm by the caudate/putamen. leading to an increase in the inhibition caused by the GPm on the VA/VL and thus decreased excitation of the premotor area
What disease are a blank expression and reduced eye-blink frequency associated with?
parkinson's
Does damage to the basal ganglia cause ipsilateral or contralateral motor effects?
contralateral (since descending motor tracts decussate)
What is the cause of Huntington's disease and which structures are affected?
gene mutation in huntington gene (autosomal dominant)

involves degeneration of the caudate/putamen and layer III of te cerebral cortex
What personality changes accompany Huntington's?
depression
apathy
hostility
slowed thought processes and forgetfulness
How does Huntington's disease cause increased excitation of the premotor cortex?
insult to the caudate/putamen leads to an increased inhibition of the GPm; this is turn means less tonic inhibition of the VA/VL and thus increase excitation of the premotor cortex
What is the key difference between the mechanisms affecting the basal ganglia in Parkinson's and Huntington's?
parkinson's: diminished inhibition of the GPm
Huntingtons: increased inhibition of the GPm

remember GPm causes inhibtion of VA/VL
What is the main function of the cerebellum and how does it execute this function?
comparator:

compares intention (cortical connections) with performance (proprioceptive info), and compensates for errors
What differentiates internal feedback from external feedback?
of the cerebellum
internal (what should be happening): from the cortex

external (what is happening): from proprioceptors
After receiving the internal and external feedback, what is the cerebellar response?
indirectly adjusts motor activity through connections with the motor and premotor cortices and brainstem to motor nuclei
What are the nuclei of the cerebellum?
Dentate nucleus; Interposed nuclei (= emboliform & globose); Fastigial nucleus
What is carried in each of the cerebellar peduncles?
Inferior: input from the spinocerebellar tracts

middle: input from the cerebral cortex

superior: output to red nucleus, thalamus, cerebral cortex
Which three arteries supply the cerebellum?
SCA
AICA
PICA
How is output generated in the cerebellum?
purkinje cells in the cerebellar cortex cause inibition of the deep cerebellar nuclei; these nuclei than project out of the cerebellum
How do mossy fibers and climbing fibers affect the cerebellar output?
they synapse both on the deep cerebellar nuclei directly and indirectly by synapsing in the cerebellar cortex (both fiber types are excitatory)
Where do mossy fibers arise from and how do the exert their effect on Purkinje cells?
spinocerebellar tracts, vestibular nuclei, reticular formation, pontine nuclei
- influence perkinje cells indirectly through synapses with excitatory granule cells
Where do climbing fibers arise from and how do the exert their effect on Purkinje cells?
inferior olivary nucleus (contains inputs from all parts of snensory and motor systems:

"climb" around purkinje somata and dendrites
What are the cerebellar functions associated with the lateral hemisphere, intermediate hemisphere, and vermis/flocculonodular lobe, respectively?
lateral: motor planning for the extremities

intermediate: distal limb coordination

vermis/flocculonodular: proximal lumb/trunk coordination and balance/ vestibulo-ocular reflexes
Which regions of the cerebellum influence the lateral corticospinal tracts?
lateral and intermediate hemispheres
By which tracts does the vermis/flocculonodular lobe influence proximal limb and trunk coordination?
anterior corticospinal tract, reticulospinal tract, vestibulospinal tract, tectospinal tract
Which regions of the cerebellum influence the medial longitudinal fasciculus and what functions are controlled this way?
vermis/flocculonodular: controls balance/ vestibulo-ocular reflexes
What are the three functional divisions of the cerebellum and which anatomical structures make up each of them?
cerebrocerebellum: lateral hemisphere/dentate nucleus

spinocerebellum: intermediate hemisphere/vermis/ part of the fastigial nucleus/ interposed nuclei

vestibulocerebellum: flocculonodular lobe/ part of the fastigal nucleus
Where do the inputs and outputs to the vestibulocerebellum come from, respectively?
inputs: semicircular canals, vestibular nuclei, lateral geniculate nucleus, superior colliculus, visual cortex

outputs: medial and lateral vestibular nuclei
Problems with what functions are associated with damage to the vestibulocerebellum?
stance and gait
Which tracts are associated with the spinocerebellum and how are they divided functionally?
cuneocerebellar tract and rostral SCPT: upper limbs

Dorsal SCT and Ventral SCT: lower limb
Which nucleus in the spinal cord gives rise to the dorsal spinocerebellar tract?
nucleus dorsalis (Clarke's nucleus) - monitors info from the muscle spindles, GTOs, and joint receptors
Which spinocerebellar tracts monitor descending information and transmit this back to the cerebellum?
ventral SCT (lower limb) and rostral SCT (upper limb): both originate from spinal border cells
Which is the only tract of the spinocerebellum associated solely with the superior cerebellar peduncle?
Ventral SCT: all others run through the ICP (although the rostal SCT also projections through the SCP)
Which spinocerebellar tract receives information from the muscle spindles, GTOs, and joint receptors of the upper limb and neck?
cuneocerebellar tract (from accessory cuneate nucleus - lies lateral to the cuneate nucleus)
What do cerebellar fibers comingle with when entering the VA/VL?
fibers from the thalamic fasciculus
What functions are associated with the spinocerebellum?
controls execution of ongoing movement: regulates muscle tone
Where do spinocerebellar outputs associated with the vermis and intermediate hemispheres travel to, respectively?
vermis: medial cell columns

intermediate hemispheres: lateral cell columns
Where are the cell bodies of the cerebrocerebellum located and where do they synapse?
cell bodies in the PMA, SMA, M1, PP: synapse on the deep pontine nuclei
On which side do symptoms of cerebellar damage manifest themselves and why?
ipsilateral: since output from the cerebellum decussates twice before reaching musculature (one up to the cortex, and once coming down it)
From what structure does output created in the cerebrocerebellum originate and where does it project to?
dentate nucleus: projects to the red nucleus and VA/VL
What clinical sign is associated with damage to the vermis?
loss of balance towards the side of the lesion
What function is associated with the cerebrocerebellum?
timing of movements
What problems are associated with a lesion to the lateral hemisphere or dentate nucleus of the cerebellum?
timing of initiation of movements, terminal tremor, temporal coordination of multiple joints, spatial coordination of hand and finger muscles
How does modification of cerebellar activity occur?
through practice and learning
How does passive limb movement differ between cerebellar damage and damage to the basal ganglia?
cerebellum: reduced resistance (hypotonia/pendular reflexes)

basal ganglia: increased resistance
How is ataxia defined?
difficultly in executing voluntary movements
What are the clinical terms used describing errors in range/force of movement, inability to sustain rhythmic alternating movements, and tremor at the end of movement, respectively?
dysmetria

dysdiadochokinesiea

terminal tremor
What type of gait is associated with midline damage to the cerebellum and why?
"drunken sailor's gait"

due to lack of axial musculature control
What problem associated with the eyes is common in cerebellar damage?
nystagmus
What does titubation refer to?
a trunk tremor while sitting or walking (due to cerebellar damage)