Lecture 3: Pain & Temperature Pathways

Question 1

What is the difference between the neospinothalamic pathway and the paleospinothalamic pathway?

Answer 1

Neospinothalamic pathway = direct spinothalamic pathway -> fast pain (highly localized, sharp, pricking)

Paleospinothalamic pathway = indirect spinothalamic pathway -> slow pain (burning, dull, aching, diffuse)

Question 2

What type of pain is conveyed by C fibers?

Answer 2

Slow pain -> dull, aching, burning, diffuse

**unmyelinated!

Question 3

T/F: unilateral lesions of the indirect spinothalamic pathway do not result in significant sensory deficits

Answer 3

True

Question 4

What fiber type is myelinated and conducts fast pain?

Answer 4

A-Delta fibers

**C fibers can conduct fast pain but they are much slower and more commonly conduct slow pain

Question 5

Where do secondary neurons of the direct spinothalamic pathway decussate?

Answer 5

In the anterior white commissure (spinal cord)

Question 6

***The spinal lemniscus is comprised of which of the following?
A. Axons of secondary neurons
B. Axons of tertiary neurons
C. Central process of a primary neuron
D. Peripheral process of a primary neuron

Answer 6

A. Axons of a secondary neuron

Question 7

***A lesion of the right spinothalamic tract at T6 would result in which of the following?
A. Left T4
B. Left T6
C. Left T8
D. Right T4
E. Right T8

Answer 7

C. Left T8

**Unilateral lesions of the lateral spinothalamic tract result in contralateral loss of pain and temperature sensation 2 sensory dermatomal segments below level of lesion

Question 8

What sensations does the ventral spinothalamic pathway modulate?

Answer 8

Light (passive) touch, crude tactile sensations and pressure

Question 9

What is Brown-Sequard syndrome?

Answer 9

Hemisection of the spinal cord causing pain and temp from contralateral side of the body and loss of discriminative touch and conscious proprioception on ipsilateral side below

Ipsilateral loss of ALL sensation at level

Question 10

What is syringomyelia?

Answer 10

Formation of fluid filled cyst (syrinx) within the spinal canal (central canal) usually at C8-T1 affecting sensation of pain and temperature due to disruption of anterior white commissure, with some motor loss as well

Question 11

If a pt presents after burning themselves on stove, iron, etc and state they werent aware that they were burning themselves because of loss of pain/temperature sensation in the upper limbs, what is one of the first conditions you should suspect?

Answer 11

Syringomyelia

Question 12

How are micturition impulses sent to the brain?

Answer 12

1. Mechanoreceptor s in bladder wall are stretched when bladder fills
2. Impulses are sent to S2-S4 via visceral afferent innervation (pelvic n) and enter dorsal root to synapse on visceral afferent nucleus
3. Interneurons convey stimulus to sacral autonomic nucleus which sends efferents to detrusor m
4. Signals also sent from visceral afferents to pontine micturition center which can override micturition reflex or increase reflex depending on situation

Question 13

What effect does interneurons stimulus to sacral autonomic nucleus have on the bladder?

Answer 13

Visceral efferent neurons sent from sacral autonomic nucleus will cause the detrusor m to contract and internal sphincter to relax

Question 14

When micturition is desired, what effect does the pontine micturition center have on the bladder?

Answer 14

Increases impulses via the pelvic nerve (efferent) causing contraction of detrusor m. Also, somatic innervation via pudendal nerve to external sphincter is inhibited causing relaxation and micturition

Question 15

What is atonic bladder do to?

Answer 15

Lesions of the dorsal roots of S2-S4

Question 16

What happens with atonic bladder?

Answer 16

Micturition reflex contraction cant occur if the sensory nerve fibers from the bladder to the spinal cord are destroyed, thereby preventing transmission of stretch signals from th ebladder

Instead of emptying periodically, the bladder fills to capacity and overflows a dew drops at a time thorugh the urethra -> overflow incontinence

Results in a large, dilated, flaccid badder and increased bladder capacity -> voluntary voiding is possible but incomplete

Question 17

What are common causes of atonic bladder?

Answer 17

Crush injury to sacral region or disease such as syphilis

Question 18

What is reflex/autonomic bladder caused by?

Answer 18

Spinal cord damage above the sacral region (S2)

Question 19

What is characteristic of reflex/autonomic badder?

Answer 19

Typical micturition reflexes can still occur, but they are no longer controlled by the brain

During the first few days to several weeks after damage to the cord, micturition reflexes are suppressed due to spinal shock from sudden loss impulses from brainstem and cerebrum (pt requires catheter) -> micturition reflex returns and unannounced emptying occurs