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16 October 2009
Chapter 7 Sensory Physiology
Quiz on Cranial
Nerves: Wednesday
Lab next week:
Sensory Physiology
and the
Auditory System
Receptors:
Encapsulated
5 different receptor types (but not all in the same cell)
• Receptors for
gustation
Figure 7.08
Stimulus
Localization
& Intensity
Receptive fields of different
neurons often overlap such
that any patch of skin may
have several receptors of the
same type (modality) and
receptors of different types
(different modalities I.e. touch,
pain temperature, etc.)
Overlapping receptive fields of
touch receptors (Meissners,
Merkels) allow for more
precise localization of a
stimulus via the mechanism of
lateral inhibition (next slide.)
Figure 7.09
Stimulus
Localization
& Intensity
Lateral inhibition exaggerates the
difference in stimulus intensity
detected by adjacent neurons.
Figure 7.10
Stimulus
Localization
& Intensity
Lateral inhibition
improves stimulus
localization.
Demonstration:
circles in carpet of
McMillan Theater =
receptive fields
Somatosensory: sensation of touch,
vibration, pain, and temperature
Misleading diagram: implies
different receptor types
connected to one sensory axon.
Deep
Superficial
Sustained stimulus
Fluctuating stimulus
Figure 7.15
Stimulus
Localization
& Modality
& Intensity
Three neurons
to the cortex!
Labeled Line
Wilder Penfield, neurosurgeon and epilepsy
Figure 7.14
=Post-central gyrus
Thalamus
Damage to specific areas (stroke) is
correlated with specific sensory deficits.
Figure 7.19
Right side
Anterolateral (spinothalamic) tract
1st order synapses onto 2nd order in spinal cord, 2nd
order axon decussates in spinal cord, travels to
thalamus in contralateral anterolateral tract, synpases
onto 3rd order neuron in thalamus, which sends its
axon to SSC.
Right side
Dorsal column-medial lemniscal tract
1st order axons ascend in ipsilateral dorsal columns
to synapses onto 2nd order in dorsal column nuclei of
brainstem, 2nd order axon decussates in brainstem,
travel to thalamus to synpases onto 3 rd order neuron,
which sends it axons to SSC.
Right side
Right side
Proprioception
Figure 7.20
Somatotopy in the SSC (post-central gyrus.)
Homunculus: representation of body in the SSC;
somatic sensations from adjacent parts of the body are processed by adjacent regions of SSC, with
those body regions more densely innervated by sensory receptors occupying more cortical tissue.
Dermatomes
Figure 7.18
Referred Pain
Watch this 2-3 minute YouTube video.
You’ll find it very interesting!
http://michaelscomments.wordpress.com/2008/09/19/very-interesting-test-of-perception
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