Pain And Temperature Pathways

Question 1

A sensory ascending pathway is in the anterolateral system on the ____ and _____ tracts.

Answer 1

Lateral spinothalmic tract

Anterior spinothalmic tract

Question 2

Rapid sharp, pricking, precise localized pain and temperature are conveyed by the _____.

A-delta fibers are _____ with a fast conduction rate.
C fibers are ______ with a slow conduction rate.

Burning, throbbing, dull, aching, diffuse pain and crude touch/pressure are conveyed by the _____. They travel through _____.

Answer 2

Direct spinothalmic pathway

Myelinated

Unmyelinated

Indirect spinothalmic system; C fibers

Question 3

What is the direct pathway?

What is the indirect pathway?

Answer 3

Receptor -> spinal cord -> lateral thalamus -> somatosensory cortices

Receptor -> spinal cord -> reticular formation -> medial thalamus -> cingulate, frontal, limbic cortices

Question 4

Primary neurons have cell bodies of pseudounipolar neurons located in the ___.

Fibers enter the spinal cord through the ____ and ascend and descend 1-2 segments in the _____.

Fibers synapse on secondary neurons in the _____ and the _____.

Answer 4

DRG

Dorsal root

Posterolateral fasciculus (Lissauer’s tract)

Substantia gelatinosa (Lamina II); nucleus proprius (Lamina IV)

Question 5

Secondary neuron axons from the substantia gelatinosa/nucleus proprius cross in the _____ and ascend in the _____ as the lateral spinothalmic tract (LSTT).

Sacral levels enter the tract first and are located in the ____ aspect of the tract. Cervical levels enter the tract last and are located in the ____ aspect of the tract.

In the medulla, the LSTT joins the VSTT and spinotectal tract to form the ____. This terminates in the ____ of the dorsal thalamus.

Answer 5

Anterior white commissure (AWC) of the SC

Contralateral anterolateral funiculus

Posterolateral; anteromedial

Spinal lemniscus; ventral posterior lateral (VPL) nucleus

Question 6

Tertiary neurons have neurons located in the _____ of the dorsal thalamus. It receives sensory info from the contralateral body via the ____.

Tertiary axons leave the VPL nucleus as thalamic radiations which course through the posterior limb of the _____ and the ______ and terminate in the _____.

Answer 6

Ventral posterior lateral nucleus

Spinal lenmiscus

Internal capsule (carries fibers from the midbrain to the thalamus)

Corona radiata

Primary somesthetic cortex (postcentral gyrus)

Question 7

Indirect spinothalmic pathway conveys what type of sensation? Most receptors are associated with viscera.

Primary fibers are _____ with slow conduction rate.

Answer 7

Deep, aching, diffuse, dull, poorly localized pain, crude touch, and firm pressure

Unmyelinated, type C fibers

Question 8

Indirect spinothalmic pathway fibers enter the spinal cord, bifurcate, and ascend/descent 1-2 segments in the ______. The primary fibers have thousands of synapses with the ____, to become secondary neurons.

Answer 8

posterolateral fasciculus (Lissaur’s tract)

Nucleus proprius (lamina IV)

Question 9

Secondary fibers from the nucleus proprius course bilaterally up the SC in the _____ to get to the reticular formation.

The fasciculus proprius is part of a diffuse neuronal net called the ____ that does what?

Slow pain info from the nucleus proprius may ascend to the thalamus as the _____.

Answer 9

Fasciculus proprius

Reticular formation: this surrounds the gray matter of the SC and extends rostrally through the core of the brainstem into the thalamus

Spinoreticular fibers

Question 10

Spinoreticular fibers terminate in the _____ of the brainstem, hypothalamus, and the _____ of the dorsal thalamus on both sides of the brain.

The projections through the reticular formation function in _____ of the organism in response to nociceptive input.

The projections to the hypothalamus and the limbic cortex function in the _____.

Answer 10

Reticular formation

Centromedian nucleus

Arousal

In the autonomic, reflex, and emotional aspects of pain.

Question 11

Indirect spinothalamic pathway lesions can cause ____.

Clinically, _____ of the spinoreticular fibers do not result in significant sensory deficits because they run _____ and _____.

Incomplete transections may allow the spinoreticular fibers to get around a lesion via the intact portion of the ____. This is the cause of _____.

Answer 11

Persistent pain

Unilateral lesions

Bilateral and diffuse

Fasciculus proprius

Persistent pain

Question 12

Pt has loss of pain and temperature below L1. Pt would have a lesion around _____.

What are common causes?

Answer 12

T11 (lateral spinothalamic tract lesion -> deficits arise 1-2 levels below the lesion on the contralateral side)

MS, penetrating injuries, compression from tumors

Question 13

____ is loss of sensations due to a hemisection of the spinal cord.

Pt has complete loss of pain and temperature sensation (spinothalamic tract) on the _____ side _____ below the level of the spinal cord lesion.

Pt has loss of discriminative touch and conscious proprioception (medial lemniscus pathway) on the ____ side below the lesion.

Pt has ____ loss of all sensation at the level of the lesion, and motor loss.

Answer 13

Brown-Sequard Syndrome

Contralateral; 1-2 levels

Ipsilateral

Ipsilateral

Question 14

____ is the formation of a fluid filled cyst in the central canal of the spinal cord; most common at the levels of ____.

The cyst pushes on the _____, affecting the crossing of the ____; this results in bilateral loss of pain/temp sensation in a _____ distribution.

Motor can be affected if cyst expands into the ____.

Symptoms?

Answer 14

Syringomyelia; C8-T1

Anterior white commissure; 2nd order neurons; shawl-like

Anterior horn

Pt burns themselves because they have loss of pain and temp

Question 15

Mechanoreceptor in the _____ muscle in the bladder wall are stretched when the bladder fills.

Impulses are sent to spinal levels of ____ via ____ and enter dorsal root to synapse on the _____.

Interneurons convey stimulus to _____. SAN contains ____ that cause the detrusor m to contract and internal sphincter to relax.

Answer 15

Detrusor m

S2-S4

Visceral afferent innervation (pelvic N)

Visceral afferent nucleus

Sacral autonomic nucleus (SAN); visceral efferent neurons (pelvic N)

Question 16

Signals for the bladder reflex are also sent from the visceral afferents to the _____ which can override the micturition reflex or increase the reflex depending on current situation.

When micturition is desired, PMC increases impulses via the ____ causing contraction of detrusor m. Somatic innervation via the _____ to the external sphincter is inhibited causing relaxation of the external sphincter and micturition.

Answer 16

Pontine micturition center (PMC)

Pelvic N (efferent)

Pudendal N

Question 17

Damage to spinal cord above sacral region (S2) causes ____. Typical micturition reflex occurs but it is no longer controlled by the PMC.

During first few days to weeks after damage to the cord, the micturition reflexes are _____ due to ____ from sudden loss of impulses from the brainstem and cerebrum. Pt’s need ____.

Micturition reflex returns and _____ occurs.

Answer 17

Reflex/automatic bladder

Suppressed; spinal shock; catheterization

Unannounced emptying

Question 18

_____ is due to lesions of the dorsal roots of S2-S4.

The micturition reflex contraction cannot occur if the ____ from the bladder to the spinal cord are destroyed, preventing transmission of stretch signals from the bladder.

Instead of emptying periodically, the bladder fills to capacity and overflows a few drops at a time through the urethra called ____. This results in large, dilated, flaccid bladder and increased bladder capacity.

Causes?

Answer 18

Atonic bladder

Sensory nerve fibers

Overflow incontinence

Crush injury to sacral region (S2-S4), damage to dorsal horn/dorsal columns, syphillis