Sensory Tracts

Question 1

Complexity of response depends on?

Answer 1

• where processing occurs

* where motor response initiated

Question 2

3 main sensory tracts that deliver somatic sensory information to the sensory cortex of the cerebral or cerebellar hemispheres

Answer 2

1) first order neuron
2) second order neuron
3) third order neuron

Question 3

95% of information passes

Answer 3

The thalamus

Question 4

First order neuron

Answer 4

• sensory neuron that delivers the sensations to the CNS; first neuron to arrive to CNS
• its cell body is in the dorsal root ganglion
• arrives from PNS to CNS at level of spinal cord through the dorsal root ganglion to brain stem

Question 5

Second order neuron

Answer 5

• the axon of the first order neuron synapses with the second order neuron when arrives to brain stem.
• cell body may be located either in spinal cord or brain stem

Question 6

Third order neuron

Answer 6

• tracts ending at cerebral cortex
• second order neuron synapses on third order neuron when arrives to thalamus
• axon of third order neuron carries sensory information from thalamus to the appropriate sensory area of cerebral cortex

Question 7

Sensory homunculus

Answer 7

More sensory receptors on different body parts

Example: lips, hands

Question 8

Areas of body that are medial will be

Answer 8

Lateral in cerebral cortex

Question 9

Areas of the body that are lateral will be

Answer 9

Medial in cerebral cortex

Question 10

Sensory modality arrangement

Answer 10

• sensory fibers are arranged within the spinal cord according to the type of sensory information carried by the individual neurons.
• posterior side > sensory fibers carrying fine touch, pressure, and vibration
• lateral side > sensory fibers carrying pain and temperature
• anterior side > sensory fibers carrying crude touch

Question 11

Medial-lateral rule

Answer 11

• most sensory nerves entering the spinal cord at more inferior level travel more medially with a sensory tract than sensory nerves entering the cord at a more superior level.
• information coming inferiorly will be medial
• information coming superiorly will be lateral

Question 12

Somatopic arrangement

Answer 12

• ascending sensory fibers are arranged within individual tracts according to their site of origin with the body
• example: lower limb, hip, trunk, upper limb

Question 13

Major ascending tracts

Answer 13

1) posterior column
2) spinocerebellar tract
3) spinothalamic tract

Question 14

Spinocerebellar tracts

Answer 14

• 2 neurons
• start at spinal cord > end at cerebellum

1) posterior spinocerebellar tract
2) anterior spinocerebellar tract

• both crossover at spinal cord but cross back to original entrance.

Question 15

Spinothalamic tracts

Answer 15

• 3 neurons
• start at spinal cord > end at thalamus

1) anterior spinothalamic tract
2) lateral spinothalamic tract

• both cross over at spinal cord but on different sides. One anteriorly and one laterally

Question 16

Posterior columns

Answer 16

• crossover at medulla oblongata
• start at spinal cord > end at thalamus
Posteriorly
• 2 neurons

Question 17

Sensory receptors monitor conditions

Answer 17

Inside the body and in external environments