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Lecture 5

NROC64H3 Lecture Notes - Lecture 5: Medial Lemniscus, Spinothalamic Tract, Spinal Cord

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Matthias Niemeier

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NROC64H3S Sensory and Motor Systems
Lecture 5 02.12.12
- Somatic Sensation
Body able to feel itself & environment, ache chill
Responsible for touch and pain
Somatic Sensory system: Different from other systems Receptors: Distributed throughout and respond to
different types of stimuli
- What Receptors are Involved?
Types of layers of skin Hairy and
hairless/glaborous, EPIDERMIS/outer and
Functions: Protect, prevent evaporation, provide
direct contact with world
Majority of somatosensory receptors
Skin, hear, blood vessels, organs, gum
mechano. Ion channels
Pacinian corpuscles, Ruffini’s
endings, Meissner’s
corpuscles, Merkel’s disks,
Krause end bulbs
Ake Vallbo and colleagues-
Primary Afferent Neurons
Receptive Field Size and
Adaptation Rate
Skin slip, 1st contact, pattern
texture recognition, lateral
stretch, hand shape
What causes Frequency Tuning? Onion-like encapsulation
of Pacinian corpuscles
2-Point Discrimination: Density of receptors, neural
capacity, convergence, receptive field size, special mechanisms
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Primary Afferent Axons
Includes Gray matter, white
matter, dorsal root, dorsal root
ganglion, central root, spinal nerve
and the sensory receptor
Spinal Cord: Spinal segments (30)
spinal nerves, w/I 4 decisions
Spinal cord ends ~3rd lumber
vertebra: Cauda equine, lumbar
puncture, anaesthetics
Dermatones: Area OF SKIN Innervated by dorsal roots of 1
spinal segment, 1-1 correspondence, shingles, herniated disk
Sensory Organization of SC: Division of spinal gray matter:
Dorsal Horn, Intermediate Zone, Ventral Horn - Myelinated
A-beta axons (touch sensitive)
Dorsal Column-Medial Lemniscal Pathway:
Medulla Cessation
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