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Neuroanatomy
Lectures 8-13
38
Anatomy
Post-Graduate
05/22/2014

Additional Anatomy Flashcards

 


 

Cards

Term
How do the 2 subdivisions of the ALS differ?
Definition

spinothalamis tract is a direct pathway from the spinal cord to the VPL nucleus of the thalamus for sensory-discriminitive aspects of well localized pain.

 

spinoreticulothalamic pathway - the reticular formation is an indirect path from the spinal cord to  the intralaminar thalamic nucleus is for poorly localized pain and  its affective-motivational aspects.

Term
Where do the ALS and PCMLS travle together?
Definition
Ascending in the posterior limb of the IC
Term
How does A-delta pain and C-fiber pain differ?
Definition

A-delta= fast, hot, sharp initial pain of the acute event

         = mainly synapse in lamina I (decussate and                  travel up spinothalamic tract of C/L ALS)

 

C = slow, dull,aching pain that reminds you not to reinjure       the area while its trying to heal

   = synapse mainly in lamina II -> interneurons project         to lamina V (decussate and travel up spinoreticular           tract in C/L ALS fibers ---ALSO referred pain)

Term
Dejerine -Roussy Syndrome
Definition

Thalamic Pain Syndrome,

a lesion results in severe, C/L debilitating pain

Term

Why does the primary sensory neuron bifurcate after entering the posteror root entry zone?

 

Definition

some descending branches participate in spinal reflexes

 

ascending brs. synapse in the posterior horn  or posterolateral fasciculus

 

 

Term
What is the function of the insular cortex?
Definition
discriminate the quality and intensity of stimuli (affective aspects of pain)
Term
If a there is a lesion in the C/L ALS at the same level that the primary sensory neuron synapses in the posterior horn, where will the loss of temperature sensation be?
Definition

this particular neuron will be unaffected.

The loss will be experienced 1 or 2  segments lower because decussations are oblique.

Term
Anterior cingulate cortex
Definition

Brodmann 24

part of the limbic system for emotions

activation increases when a stimulus is judged to be more unpleasant

 

If AAC is damaged, you feel pain, but you just don't care

Term
Blood supply to ALS?
Definition

PICA                                       in medulla

circumferential br. of Basilar a.   in the pons

Quadrigeminal                          in the midbrain

Term
Which tract does viseral pain follow?
Definition

2 routes:

1. ALS (referred pain: thru lamina V of posterior horn)

2. PCMLS (chronic pain: PRG -> post. column, -> C/L medial lemniscus -> VPL -> Insular cortex)

Term
What surgery can relieve intractable pain?
Definition
midline myelotomy
Term
Supplementary Motor cortex
Definition

Brodmann 6

 

Plans the sequence of muscle activations reqd to perform the movements

 

 

Term
Premotor Cortex
Definition

Brodman 6 (with supplementary motor cortex)

 

After planning, sets the proper posture for the limb in which the movement is initiated (neurons are active before M1 cells are.)

 

limb movements are guided by sensory input, NOT MEMORY

Term
Parietal motor cortex
Definition

Brodmann 5

 

Active only when reaching for an object, and hand manipulation neurons

 

Brodmann 7

 

eye-hand coordination, visually identifying a target

 

Term
Cingulate motor cortex
Definition

(B 24)   @ cingulate sulcus,

 

controls movements and gestures that occur in an emotional context

Term
Apraxia
Definition

Unable to perform voluntary movements despite having normal power and muscle tone

 

lesions to (B 5,6,7 NOT 4)

Term
What is the path of the corticospinal tract?
Definition

 

 homunculus -> posterior limb of IC ->

crus cerebri ->

basilar pons ->

medulla pyramid ->

pyrimidal decussation(85%) ->

lateral corticospinal tract ->

Term
Purpose of the corticospinal tract?
Definition

for flexion of LMNs (directly or thru interneurons)

 

precise finger movements

 

inhibits antagonist (extensor) mm. thru inhibitory interneurons

Term
Blood supply to the CST?
Definition

(circumferential and) paramedian branches of PCA 

paramedian branches of basilar artery in the pons

anterior spinal artery in the medulla & spinal cord

 

Term
Brain stem - spinal systems (4+)
Definition

EXTENSORS:

medial vestibulospinal tract (in MLF)

lateral vestibulospinal tract

medial (pontine) reticulospinal tract

lateral (medullary) reticulospinal tract

 

FLEXORS:

rubrospinal tract (C1-C3)

 

 

Term
medial vestibulospinal tract
Definition

cell bodies in medial inf. vestibular nuc. (rostral medulla)

descends  B/L in MLF

 

1. extends upper thoracic levels

2. regulates head position by reflex activation of neck extensor mm.

 

 

Term
lateral vestibulospinal tract
Definition

cell bodies in lateral vestibular nuc (pons)

(-) inputs: cerebellum cortex

(+) inputs: vestibular apparatus(CN VIII) & cerebellar nuc.

 

control or paravertebral and proximal limb extensor mm. (+) related to balance and posture, (-) interneurons for flexion

 

predominantly I/L, make rapid adjustments to posture

 

Term
Reticulospinal tracts (med & lat)
Definition

both I/L

 

Med. RST: from pontine reticular formation to spinal

(+) effect on axial and leg extensors for posture

 

Lat. RST: from medullary reticular formation

(-) influence on girdle & prox. appendicular extensors 

 

Term
purpose of Spinoreticular Fibers?
Definition

afferent (ascending)

 

they influence the pontine nuclei (corticreticular fibers)

Term
regulation of posture in brainstem spinal pathways
Definition

FEEDFORWARD: postural responses precede limb movement (corticospinal tract)

 

FEEDBACK: sensory inputs detect postural instability (vestibulospinal tract)

Term
Decorticate rigidity
Definition

toes point & arms flex in

supratentorial lesion (diencephalon/ cortex area)

patient exhibits altered consciousness

U/L or B/L

presents "at rest" or w/ painful stimulus

 

Term
DECEREBRATE RIGIDITY
Definition

toes point and elbows extend

supratentorial lesion with herniation thru tentorial notch into the midbrain and pons

 

(diencephalic stage: altered consciousness, but small reactive pupils,lethargy)

(after herniation: comatose, pupils are fixed and dilated, Cheyne-Stokes respirations, poor prognosis)

Term
Which descending pathway influences LMNs to flexor mm?
Definition

medial reticulospinal tract

lateral corticospinal tract

 

Term
Which descending pathway influences LMNs to extensor mm?
Definition

medial vestibulospinal tract (MLF)

lateral reticulospinal tract

medial reticoluspinal tract

lateral vestibulospinal tract

Term
myasthenia gravis
Definition

Disease affecting...

 

axons of LMNs form neuromuscular junctions, ACh binds ACH receptors

 

muscle starts out strong then gets weaker, lose some motor units

Term

Intrafusal fibers are inn. by?

 

Extrafusal fibers are inn. by?

 

 

Definition

INTRAFUSAL: NUCLEAR BAG

mechanoreceptive sensory (IA) fibers

(respond to the rate of change in muscle length)

gamma motor neurons (dynamic, at the poles)

 

INTRAFUSAL: NUCLEAR CHAIN

mechanoreceptive sensory (II) fibers

(respond to changes in length)

gamma motor neurons (static, at the poles) 

 

EXTRAFUSAL:

Alpha motor fibers

Term
Myotatic stretch reflex
Definition

tap on a tendon causes change in muscle length (passive stretch) detected by 1a sensory neuron

 

1. Gamma motor neurons fire to adjust intrafusal fibers tothe appropriate length for stretch and tone.

2. This activates 1a sensory neuron (increase AP firng rate) forms (+) synapse directly on the alpha motor neuron 

3.  producing the muscle contraction. (Extrafusal fibers contract, so the intrafusal fibers would slacken, if not for the gamma motor neurons.) 

Term
Reciprocal Inhibition
Definition
1a sensory neuron forms (+) synapse on 1a inhibitory interneuron -> it synapses on alpha motor neuron to the antagonist mm.
Term
withdrawal reflex
Definition

painful cutaneous input activates

(+) interneurons synapse on  alpha motor neurons to flexors, withdrawing the limb from danger

 

(-) interneurons synapse on the alpha motor neurons to the antagonists/ extensors, allowing the withdrawal of the limb from danger

Term
crossed-extension reflex
Definition

occurs in the C/L limb in conjuntion with the withdrawal reflex to maintain balance

 

The A-delta or C-fibers that  transmit pain  to the spinal cord  synapse on interneurons that cross the midline to activate (+) and (-) interneurons in the C/L spinal cord

Term

 

posterior cord syndrome

Definition

affects PCMLS

discriminitive touch loss localizes the level...

therefore, you lose the entire reflex, too

 

Common causes:

tabes dorsalis

Vit B12 Deficiency

Term
Anterior Cord Syndrome
Definition

Affects ALS and CST

if ASA is occluded: B/L deficits

 

if branches of ASA:

motor function - I/L below decussation, C/L above

sensory pain and temp: affects C/L 1 or 2 segments below

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