Sensory Pathways III

Question 1

Fasciculus gracilis

Answer 1

-pathway of conscious proprioception (pelvic limb)
-neurons running through dorsal funiculus
-spinal segments caudal to T6 (caudal thoracic, lumbar, sacral, and caudal segments)

Question 2

Fasciculus cuneatus

Answer 2

-pathway of conscious proprioception (thoracic limb)
-neurons running through lateral dorsal funiculus
-spinal segments cranial to T6 (cervical and cranial thoracic segments)

Question 3

Motor and descending pathways

Answer 3

-Pyramidal tracts
-Extrapyramidal tracts

Question 4

Sensory and ascending pathways

Answer 4

-dorsal column of medial lemniscus system
-spinocerebellar tracts
-anterolateral system

Question 5

Proprioception

Answer 5

-awareness of body in space

Question 6

Exteroception

Answer 6

-detection of external stimuli (including pressure, touch, temperature, vibrations, and smell/taste/vision/hearing)

Question 7

Enterception (interoception)

Answer 7

-detection of the internal stimuli (including pressure, touch, temperature)

Question 8

Nociception

Answer 8

-detection of noxious (harmful, unpleasant, painful) stimuli
>stimuli is forceful enough that it could cause tissue damage
»includes mechanical pressure (not light touch) and temperature

Question 9

Nociceptor receptors

Answer 9

-nitric oxide receptors (with bare nerve endings)
>these receptors have a high threshold, and are not easily activated

Question 10

Where are nociceptor receptors located?

Answer 10

-located diffusely throughout the body in high numbers
>skin (superficial/deep)
>muscle
>GIT

Question 11

Brain regions of nociception

Answer 11

-sensory neuron/periphery to spinal cord where it synapses on interneurons and travels up spinal cord through cerebral cortex (medulla, pons) to synapse on thalamus
-Neuron from thalamus to somatosensory cortex

Question 12

Spinal pathways for nociception

Answer 12

-Spinothalamic tract (comes from spinal cord and synapses on thalamus)
>largely crossed (contralateral)= lateral spinothalamic tract (lateral funiculus, ventral) AND ventral spinothalamic tract (ventral funiculus)
**there will also be a small lateral and ventral spinothalamic tract that stays same side (ipsilateral)

Question 13

Loss of pain

Answer 13

-would mean there is a very severe injury to spinothalamic tract because the nociception pathway has multiple parts in the cord and transmits in both contralateral and ipsilateral, so if no sensation then everything damaged severely
>poor prognosis if animal has no deep pain

Question 14

Multi-synaptic pathway of nociception

Answer 14

-interneurons in grey matter send pathways in lateral and ventral funiculus
-can/will have multiple synapses along the way and multiple synapses on multiple nuclei in the brain

Question 15

Somatotopy

Answer 15

-defined areas of the peripheral body corresponding to specific regions of the somatosensory cortex (SSC) in the brain

> pathways that terminate in the SSC are not organized at random, and neurons coming from various peripheral receptors are not synapsing in the same locations
ascending pathways at various locations of SSC