cerebral cortex: conscious perception

cerebellum: unconscious perception (regulate muscle tone and coordinate motor function)

Dorsal Column/Medial Lemniscus Pathway

Carries information concerned with:

Dorsal Column/ Medial Lemniscus Pathway

Sensory receptors involved include:

pacinian corpuscles

joint receptors

meissner's corpuscles

golgi tendon organs

muscle spindles

DC/ML pathway:

Peripheral processes of dorsal root ganglion cells provide axons for these receptors. The central processes of the DRG cells enter the spinal cord by _____ and entering the ____.

curving medially around the posterior horn

posterior funiculus

DC/ML pathway

Ascending fibers from the caudal segmental levels shift ____ and ___ as they ascend in the ____. As the fibers from higher levels of the cord enter, they assume a more ___ position.

medially

dorsally

posterior funiculus

lateral position

DC/ML pathway

Because fibers from lower segmental levels are more medial, and fibers from higher segmental levels are more lateral, this provides a ____ to the posterior funiculus.

___ is most medial, ____ is most lateral, and ____ is in the intermediate portion.

Somatotopic organization

sacral fibers

cervical fibers

lumbar and thoracic fibers

DC/ML pathway

The posterior funiculus on each side is divided by the _____ above T6 into ____ and ____.

posterior intermediate septum

fasiculus gracilis (medial)

fasciculus cuneatus (lateral)

DC/ML pathway

Fasciculus gracilis:

present at all spinal levels

contains long ascending branches of fibers from sacral, lumbar and lower 6 thoracic dorsal roots

DC/ML pathway

Fasciculus cuneatus:

first appears around T6

contains long ascending branches of fibers from the upper 6 thoracic and cervical dorsal roots

DC/ML pathway

1st order Neuron:

neurons in the dorsal root ganglion

send their central processes ascending in the fasciculus gracilis or cuneatus

DC/ML pathway

2nd order neuron:

nucleus gracilis and nucleus cuneatus

-the central process of these neurons give rise to the internal arcuate fibers which decussate at the brain stem to form the medial lemniscus

DC/ML pathway

3rd order neuron

DC/ML pathway

decussation

from the 2nd order neurons

-the central process of these neurons give rise to the internal arcuate fibers which decussate at the brain stem to form the medial lemniscus

the medial lemniscus ascends int he contralateral half of the brain stem and terminates on the VPL nucleus of the thalamus (3rd order neuron)

DC/ML pathway

The 3rd order neurons send fibers that pass through the ____ to the ___.

posterior limb of the internal capsule (when it leaves the thalamus)

postcentral gyrus of the cerebral cortex (somatosensory cortex) in the parietal lobe

2 pt. disccrimination

kinesthetic sense

Loss of position sense in the LE's greatly impairs equilibrium, stance, gait, and results in ataxia.

nondiscriminative touch

temperature

pain

Spinothalamic tract *main one

spinomesencephalic fibers

spinoreticular fibers

spinohypothalamic fibers

Spinothalamic Tract

1st order neuron

DRG cell

axons of these neurons enter the dorsolateral fasiculus and may enter the dorsal horn or travel up the cord 1-2 segments, then enter the dorsal horn

Spinothalamic Tract

2nd order neuron

Spinothalamic Tract

3rd order neuron

Spinothalamic Tract

Terminates in the ____

Spinothalamic tract

Decussation:

axons from the 2nd order neuron cross in the anterior white commisure

one or more extra neurons may be involved PRIOR to this crossing of the anterior white commisure

Spinothalamic Tract:

After decussation, the axons of the 2nd order neuron ascend the cord in the____.

Spinomesencephalic fibers:

Neurons 1&2 are the same as the spinothalamic tract

They terminate in the:

turning eyes toward the site of pain

activating descending tracts that control pain (inhibiting pain)

Spinoreticular fibers:

neurons 1 and 2 are the same as the spinothalamic tract 

the fibers terminate :

Spinohypothalamic fibers

neurons 1 & 2 are the same as the spinothalamic tract

the fibers terminate in the _____ and are responsible for _____

hypothalamus

fight or flight (autonomic responses) and emotional responses to pain

contralateral analgesia

(lack of pain and temperature sensation)

pain sensation may still be intact a couple of levels below the lesion because they travel up before decussating

*** will still have touch because of other pathways

descending pain inhibitory pathway

endogenous or exogenous opiates

TENS/Acupuncture

Descending Pain Inhibitory Pathway

Originates in the:

Descending Pain Inhibitory Pathway:

PAG fibers project to the ____, which then project to _____.

raphe nuclei in the medulla

laminae II and III of the spinal cord

descending pain inhibitory pathway:

the projections into laminae II and III cause the release of ____ which activates _____.

serotonin

enkephalinergic neurons - inhibit pain transmission

Descending Pain Inhibitory Pathway:

There is a direct connection between the PAG and ____ which does not go through the raphe nuclei.

Endorphins

• enkephelains
• dynorphin
• B-endorphin

morphine

others (heroin)

they depress respiration when given systemically

- can be given locally as an epidural

PAG, Raphe, and dorsal horn

decreased consciousness

TENS (transcutaneous electrical nerve stimulation) and Acupuncture

Activates _____.

Collaterals from these stimulate ______.

These release ____ which inhibits ____.

large-diameter myelinated fibers

enkephalinergic interneurons in the dorsal horn

enkephalin

release of substance p (helps block pain transmission)

sympathetic fibers

dorsal roots

dorsal horn tract cells

Common Referred Pain:

Diaphragm -->

Esophagus -->

Heart -->

superior shoulder (C3-C4)

substernal

L chest, shoulder, medial L arm (T1-T8)

Common Referred Pain:

Stomach -->

Gall bladder -->

Appendix -->

Kidney -->

epigastric area

lower, anterior border of R rib cage or mid-scapular area

McBurney's Point

L inguinal region or lumbar spine

UE (above T1):

Cuneocerebellar tract

Rostral spinocerebellar tract

LE (below T1):

Dorsal spinocerebellar tract (DSCT)

Ventral Spinocerebellar Tract (VSCT)

muscle length

changes in muscle length

tension in tendons

touch and pressure from skin to the cerebellum for subconscious control of movements

GTO's

muscle spindles

touch and pressure receptors

Dorsal SpinoCerebellar Tract (DSCT):

this tract caries information regarding:

unconscious sensation, to the cerebellum from the LOWER 1/2 of the body (T1 and below)

proprioception

muscle spindles (type Ia and II fibers)

GTO's (type Ib fibers)

touch and pressure receptors

Dorsal SpinoCerebellar Tract (DSCT)

1st order neuron

Dorsal Spinocerebellar Tract (DSCT)

2nd order neuron

located in the dorsal nucleus of Clarke (nucleus dorsalis) located only in T1-L2

afferents below L2 travel upwards in posterior columns and synapse on nucleus dorsalis neurons

Dorsal SpinoCerebellar Tract (DSCT)

Neurons of the nucleus dorsalis give rise to large fibers that ascend in the _____. These fibers become incorporated in the ______ once they reach the medulla and they terminate in the_____.

posterolateral part of the lateral funiculus

inferior cerebellar peduncle

ipsilateral cerebellum

Cuneocerebellar Tract:

analogous to _____ but  ______

DSCT

converys information from the upper 1/2 of the body

Cuneocerebellar Tract:

1st order neuron

Cuneocerebellar Tract:

axons from the 2nd order neurons enter the ___ and terminate in the ____

inferior cerebellar peduncle

cerebellum on ipsilateral side from origin

Ventral Spinocerebellar Tract (VSCT):

carries information regarding:

unconscious sensation to the cerebellum from the lower 1/2 of the body (T1 and below)

transmits information being carried to the spinal cord from descending motor pathways (planned movement)

Ventral Spinocerebellar Tract (VSCT)

Sensory Receptors:

muscle spindle (type Ia and type II)

GTO's (type Ib fibers)

touch and pressure receptors

Same as DSCT but also includes inputs from descending motor pathways

Ventral Spinocerebellar Tract (VSCT)

1st order neurons:

cells in laminae V, VI, and VII in lumbar segments

*decussate immediately in anterior white commisure

Ventral Spinocerebellar Tract (VSCT)

after the 1st order neurons deccusate, they form a tract in the contralateral ____ just anterior to the _____

lateral funiculus

dorsal spinocerebellar tract

Ventral Spinocerebellar Tract (VSCT):

In the upper pons, the tract enters the _____ to reach the cerebellum. The fibers ______ in the cerebellum.

superior cerebellar peduncle

decussate again (double crossing)

Ventral Spinocerebellar Tract (VSCT)

This tract conveys information related to :

Rostral Spinocerebellar Tract:

conveys infomation regarding:

the upper 1/2 of the body

relays information from descending motor pathways

analogous to VSCT but for the upper 1/2 of the body

Rostral Spinocerebellar Tract:

1st order neuron

cells in the posterior horn of the cervical enlargement

axons from these cells ascend UNCROSSED in the lateral funiculus

Rostral Spinocerebellar Tract:

the axons of the 1st order neuron reach the cerebellum by traveling through the:

inferior cerebellar peduncle (most)

superior cerebellar peduncle (some)