Presentation on theme: "Somatic Sensation of the Face and Head"— Presentation transcript:
1 Somatic Sensation of the Face and Head 04. The Trigeminal SystemSomatic Sensation of the Face and Head
2 Objectives:Outline the two pathways for facial sensation from the head.Contrast facial sensation from the head and somatic sensation from the body. In what ways are they similar? Different? Try drawing this on the Haines atlas diagram at the end of the lecture.Diagram the corneal reflex: the afferent and efferent limbs as well as nuclei involved in the brainstem.If a person does not blink, how would you determine if the problem were in the sensory (afferent) limb, motor (efferent) limb, or brainstem interconnections for the corneal reflex?Explain how a single, small medullary vascular lesion could abolish pain and temperature from the face on the right side and pain and temperature from the body on the left side. What vessel is most likely occluded?
3 Peripheral Receptors and Sensation Structures served by trigeminal systemCN V-1CN V-2CN V-3?Great auricular nerve (C2-C3)
4 How many neurons in sensory pathway? DCML/ALSPeripheral ganglion (DRG)Spinal cord, medullaVPL nucleus of the thalamusTrigeminal systemPeripheral ganglion (Trig. gang.)2 nuclei in brainstem (pons, medulla, sp cord)VPM nucleus of the thalamus
7 Second-Order Trigeminal Neurons Originate in two brain stem nuclei:Principal (chief) trigeminal nucleusSpinal (descending) trigeminal nucleusYoung, Young and Tolbert, 2008 Fig
8 III. Second-Order Trigeminal Neurons A. Principal (chief) trigeminal nucleusMediates fine touch, joint position, vibration.Located in pons lateral to motor nucleus of CN V.This would be equivalent to what nucleus of the brainstem? _____________Young, Young and Tolbert, 2008 Fig
9 III. Second-Order Trigeminal Neurons B. Spinal (descending) trigeminal nucleusMediates pain and temperature.Spinal (descending) trigeminal tractDescends caudally as far as C2-C3 and is continuous with dorsal horn.This would be equivalent to what region in the spinal cord? _____________Young, Young and Tolbert, 2008 Fig
10 III. Second-Order Trigeminal Neurons C. Ascending Trigeminal PathwaysAxons of second-order neurons form the trigeminothalamic pathway to the VPM nucleus of the thalamus.Axons from neurons in the chief sensory nucleus carry sensations such as: _____Axons from neurons in the spinal trigeminal nucleus carry sensations such as: ____Secondary sensory neuronSecondary sensory neuronYoung, Young and Tolbert, 2008 Fig
11 IV. Third Order NeuronsProject from VPM in the thalamus to the Postcentral gyrus (primary sensory cortex)Axons course through the internal capsule
12 V. Primary Somatosensory Cortex, Postcentral Gyrus There are four different body maps to help extract texture, form, and motion that come from the head and body.Name them:1. DCML (vibration, fine touch, proprioception)2. ALS (pain, temperature)3. Trigeminal system (vibration, fine touch)4. Trigeminal system (pain, temperature)
13 VI. Association Somatosensory Cortex Posterior Superior Parietal Areas 5 and 7 of Brodmann.
14 Self-assessment: When you think you have mastered the pathways, select 2 colors in both a dark and light shade. Use the dark color for the body and the lighter color for the face pathways.e.g. Light blue-Trigeminothalamic (ventral)Dark blue – ALSPink – trigeminothalamic (dorsal) from chiefRed – DCMLAnimation