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.

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)

Thalamic Pain Syndrome,

a lesion results in severe, C/L debilitating pain

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

some descending branches participate in spinal reflexes

ascending brs. synapse in the posterior horn  or posterolateral fasciculus

this particular neuron will be unaffected.

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

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

PICA                                       in medulla

circumferential br. of Basilar a.   in the pons

Quadrigeminal                          in the midbrain

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)

Brodmann 6

Plans the sequence of muscle activations reqd to perform the movements

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

Brodmann 5

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

Brodmann 7

eye-hand coordination, visually identifying a target

(B 24)   @ cingulate sulcus,

controls movements and gestures that occur in an emotional context

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

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

 homunculus -> posterior limb of IC ->

crus cerebri ->

basilar pons ->

medulla pyramid ->

pyrimidal decussation(85%) ->

lateral corticospinal tract ->

for flexion of LMNs (directly or thru interneurons)

precise finger movements

inhibits antagonist (extensor) mm. thru inhibitory interneurons

(circumferential and) paramedian branches of PCA 

paramedian branches of basilar artery in the pons

anterior spinal artery in the medulla & spinal cord

EXTENSORS:

medial vestibulospinal tract (in MLF)

lateral vestibulospinal tract

medial (pontine) reticulospinal tract

lateral (medullary) reticulospinal tract

FLEXORS:

rubrospinal tract (C1-C3)

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.

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

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 

afferent (ascending)

they influence the pontine nuclei (corticreticular fibers)

FEEDFORWARD: postural responses precede limb movement (corticospinal tract)

FEEDBACK: sensory inputs detect postural instability (vestibulospinal tract)

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

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)

medial reticulospinal tract

lateral corticospinal tract

medial vestibulospinal tract (MLF)

lateral reticulospinal tract

medial reticoluspinal tract

lateral vestibulospinal tract

Disease affecting...

axons of LMNs form neuromuscular junctions, ACh binds ACH receptors

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

Intrafusal fibers are inn. by?

Extrafusal fibers are inn. by?

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

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.) 

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

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

posterior cord syndrome

affects PCMLS

discriminitive touch loss localizes the level...

therefore, you lose the entire reflex, too

Common causes:

tabes dorsalis

Vit B12 Deficiency

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