Lec. 1/2/3

Question 1

Describe the basic organization of the nervous system

Answer 1

CNS

PNS -> Autonomic (sympathetic, parasympathetic)
-> Somatic -> (efferent/motor, afferent/sensory)

Question 2

What are the 4 main functions of sensory information?

Answer 2

1. Perception
2. Control of movements
3. Regulation of function of internal organs
4. Maintenance of arousal

Question 3

What’s a modality? And a submodality?

Answer 3

Modality -> quality of sensation (sight/touch/hearing/etc.)

Submodality -> components of said modality

Question 4

What are the 2 parallel pathways somatic sensory information?

What is each pathway conveying?

Answer 4

Fine touch, proprioception -> Dorsal column-medial lemniscal pathway

Pain, temperature -> anterolateral pathway

Question 5

What are the 4 types of sensory fibers? What sense does each convey?

Answer 5

Aα, Αβ -> Fine touch + proprioception

Αδ, C -> Pain + Temperature

Question 6

Name and describe the pathway for proprioception + fine touch

Answer 6

Dorsal column-medial lemniscal pathway.

1. Aα & Aβ fibers (from sensory neurons) enter the dorsal column)
2. Synapse with dorsal column nuclei in the brainstem
3. Dorsal column nuclei cross the midline
4. Dorsal column nuclei project to the thalamus
5. Thalamus neurons synapse in the cortex

Question 7

Name and describe the pathway for pain + temperature

Answer 7

Anterolateral pathway.

1. Aδ & C fibers from nocirecepting neurons enter the dorsal column
2. They immediately synapse to the anterolateral column.
3. Dorsal neurons immediately crossover and project to the thalamus.
4. Thalamus neurons synapse in the cortex

Question 8

What are the clinical implications of the parallel of sensory information?

Answer 8

Due to crossover differences:

touch/proprioception crosses over in brain stem

Pain/temperature crosses over in dorsal column

A partial lesion in the spinal cord can remove some of the senses in the left/right while preserving the other

Question 9

What results in lesioning half of the spinal cord?

Answer 9

Ipsilateral side to lesion:
Fine touch damaged
Pain/temp persevered

Contralateral to lesion:
Fine touch preserved
Pain/temp damaged

Question 10

How are submodalities spread out by different axons?

Answer 10

Each submodality is mediated by a specific receptor

Question 11

What is combinatorial processing?

Answer 11

Perceived sensations are caused by activation of multiple receptor types and ingestion of parallel channels in brain

Question 12

What are Incoming vs outgoing fibers called?

Answer 12

Afferent -> incoming

Efferent -> outgoing

Question 13

Describe the diameter of the 4 sensory fibers, and what the implications are for propagation speed?

Answer 13

Aα -> Highly myelinated
Aβ -> Highly myelinated

Aδ -> free nerve endings
C -> free nerve endings

So Aα & Aβ are fast propagating, meaning fine touch and proprioception travel fast than Aδ & C which are slow propagating