16 October 2009

Chapter 7 Sensory Physiology

Quiz on Cranial Nerves: Wednesday

Lab next week:Sensory Physiology

and theAuditory System

Receptors:

Encapsulated

• Receptors for gustation

5 different receptor types (but not all in the same cell)

Figure 7.08

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.)

Stimulus Localization& Intensity

Figure 7.09

Lateral inhibition exaggerates the difference in stimulus intensity detected by adjacent neurons.

Stimulus Localization& Intensity

Figure 7.10

Lateral inhibition improves stimulus

localization.

Stimulus Localization& Intensity

Demonstration: circles in carpet of

McMillan Theater = receptive fields

Somatosensory: sensation of touch, vibration, pain, and temperature

Deep

Superficial

Sustained stimulus

Fluctuating stimulus

Misleading diagram: implies different receptor types

connected to one sensory axon.

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

Damage to specific areas (stroke) is correlated with specific sensory deficits.

Thalamus

Figure 7.19

Anterolateral (spinothalamic) tract1st 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.

Dorsal column-medial lemniscal tract1st 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 3rd order neuron, which sends it axons to SSC.

Right side

Right sideRight side

Right side

Proprioception

Figure 7.20

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.

Somatotopy in the SSC (post-central gyrus.)

Dermatomes

Figure 7.18

Referred Pain

http://michaelscomments.wordpress.com/2008/09/19/very-interesting-test-of-perception/

Watch this 2-3 minute YouTube video. You’ll find it very interesting!