Week 3 Objective 2: contrast stimuli touch, temp, nociceptive receptors: trace sensory pathways from point of origin to the sensory cortex

Question 1

First order neurons

Answer 1

primary neurons

come from peripheries

cell body in the dorsal root ganglia

enter spine through dorsal roots

synapse in spinal cord with secondary neuron

Question 2

Second order neuron

Answer 2

originate in spinal cord gray matter

travels through spinal cord in one of the myelinated columns

decussates

synapses in the thalamus with tertiary neurons

Question 3

Tertiary neurons

Answer 3

travel through internal capsule (myelinated pathway between thalamus and some basal nuclei)

synapses in the seomatosensory cortex

Question 4

Two point discrimination touch

Answer 4

travels in dorsal column medial lemniscal pathway

refers to ability to distinguish two separate points as close as 2 millimeters apart

Question 5

Lateral inhibition is important in two point discrimination how

Answer 5

blocks lateral spread of excitatory signals, thereby increasing degree of contrast in the cerebral cortex

lateral inhibition occurs at each synaptic level:

dorsal column nuclei
ventrobasal nuclei of thalamus
somatosensory cortex

Question 6

Where does lateral inhibition occur?

Answer 6

1. dorsal column nuceli
2. ventrobasal nuclei of thalamus
3. somatosensory cortex

Question 7

Signals from the lower limb would travel in what area of the spinal cord?

Answer 7

dorsal, most medial (gracilis)

dorsal column medial lemniscal pathway

Question 8

Signals from the upper limbs would travel in what area of the spinal cord?

Answer 8

dorsal, lateral (cuneatus)

dorsal column medial lemniscal pathway

Question 9

Axons in the fasciculus gracilis synapse where?

Answer 9

in the lower medullar in the nucleus gracilis

Question 10

Axons in the fasciculus cuneatus synapse where?

Answer 10

in the lower medulla in the nucleus cuneatus

Question 11

Dorsal column medial lemniscus travel how?

Answer 11

travel through the brain stem as paired tracts referred to as the medial lemniscus

Question 12

Secondary neurons synapse where?

Answer 12

in the basolateral nucleus of the thalamus with tertiary neurons

Question 13

tertiary neurons travel…

Answer 13

through the internal capsule to the somatosensory cortex

Question 14

Where do secondary neurons decussate in the medial lemniscus pathway?

Answer 14

in the nucleus gracilis or nucleus cuneatus of the medulla

Question 15

Pain Pathways: Receptor type, trait, and characteristics of “fast pain”

Answer 15

nociceptors, free endings

.1 second 
not felt in "deep" tissues 
mechanical and thermal 
carried by A-sigma fibers 
typically terminate in lamina I (lamina marginalis) of the dorsal horns of the spinal cord

Question 16

Pain Pathways: Receptor type, trait, and characteristics of “fast pain”

Answer 16

Use C type fibers

described as “throbbing” “aching” “burnings” chronic, nauseous

1 sec or more
mechanical, thermal, chemical stimuli

terminates in layers ii and iii, substantia gelatinosa

Question 17

What pathway does pain travel in?

Answer 17

anterolateral pathways

Question 18

Primary pain fibers synapse….

Answer 18

in the dorsal horn of the spinal cord, layers I, II, III with the secondary fibers

Question 19

Secondary fibers: when do they decussate?

Answer 19

immediate, and THEN make up the anterolateral pathway

Question 20

fast pain fibers make up the ___________ tracts

what kind of neurotransmitter does it use?

Answer 20

neospinothalamic tracts, and synapse terminate in the ventrobasal nuclei of the thalamus

delta fibers, they use glutamate

Question 21

slow pain fibers make up the ______ tracts

Answer 21

paleospinothalamic pathway

Question 22

most of the paleospinothalamic fibers end

what kind of neurotransmitter does it use?

Answer 22

most of them terminate in the brain stem, a few go to the thalamus

glutamate and substance “P”

glutamate is instantaneous; P is released more slowly

Question 23

Ventrobasal nuclei of the Thalamus vs throughout brain stem

which of those is the synapsing description of secondary paleospinothalamic pain fibers and which is secondary neospinothalamic pain fibers

Answer 23

neo - ventrospinothalamic

paleo - throughout brain stem

Question 24

Brown Sequard Syndrome

Answer 24

results when there is a hemisection of the spinal cord

results in loss of motor functions in all segments below the level off the transection

sensations of pain, heat, and cold (spinothalamic pw) are lost on the opposite side of the body in dermatomes TWO TO SIX SEGMENTS BELOW THE LEVELS OF THE TRANSECTION

kinetesthetic sensations such as body position, vibrations, two pt discrimination, are lost on the same side of the body as the transection

Question 25

Analgesia system

Answer 25

consists of paraaquaductal gray and paraventricular regions of brainstem, 3rd ventricle

Question 26

the two associated nuclei in the analgesia system consist of

Answer 26

the ralph magnus nucleus and the reticular nuclei in medulla

pain inhibitory complex in dorsal horns of spinal cord

Question 27

Thermal sensations

“kinds”

fibers involved

Answer 27

Cold, warm, and pain

Warmth: c type fibers, free nerve endings
Cold: more numerous than warmth, type A delta myelinated endings

Cold/warm receptors: thought to be stimulated by changes in metabolic rates.

Thermal pathways are parallel to those for pain signals

Question 28

Referred Pain: when it occurs, fibers that carry it, and traits

Answer 28

occurs when visceral pain fibers are stimulated and stimulate pain fibers

carried by C type fibers

diffuse, rather than localized

can result from ischemia