16 October 2009 Chapter 7 Sensory Physiology Quiz

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 Mc. Millan 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 1 st order synapses onto 2 nd order in spinal cord, 2 nd order axon decussates in spinal cord, travels to thalamus in contralateral anterolateral tract, synpases onto 3 rd order neuron in thalamus, which sends its axon to SSC. Right side Dorsal column-medial lemniscal tract 1 st order axons ascend in ipsilateral dorsal columns to synapses onto 2 nd order in dorsal column nuclei of brainstem, 2 nd order axon decussates in brainstem, travel to thalamus to synpases onto 3 rd order neuron, which sends it axons to SSC. 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 You. Tube video. You’ll find it very interesting! http: //michaelscomments. wordpress. com/2008/09/19/very-interesting-test-of-perception /