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

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17 Mar 2012
School
Department
Course
NROC64H3S Sensory and Motor Systems
Lecture 5 02.12.12
Introduction
- 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
Touch
- What Receptors are Involved?
Types of layers of skin Hairy and
hairless/glaborous, EPIDERMIS/outer and
DERMIS/inner
Functions: Protect, prevent evaporation, provide
direct contact with world
Mechanoreceptors
Majority of somatosensory receptors
Skin, hear, blood vessels, organs, gum
UNMYLENIATED AXON BRANCHES’ W/
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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