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Kimberle M. Jacobs, PhD Sanger 11-046 827-2135 [email protected] midline LEARNING NEURONAL PATHWAYS REQUIRES REPETITION 1. Details of pathway: Where are cell bodies located, where is the synapse made, where do axons cross the midline, first structure, second structure, etc. SpinalCord 2. Location of nuclei and tracts within brain sections Cortex Thalamus Somatosensory Systems – All senses other than Olfaction, Gustation, Audition, Vision, and Vestibular Sensation: Modalities Touch (and Pressure), Vibration Sense, Proprioception, Kinesthesia, Stereognosis, Pain & Temperature Proprioception - sense of static and dynamic position of limbs and body Kinesthesia - the ability to feel movements of the limbs and body Stereognosis – ability to recognize objects based on touch alone A. Pain and Temperature B. Fine Discrimination Touch Non-conscious Proprioception Conscious Somatosensation Spinocerebellar Tracts BODY HEAD (IPSILATERAL) Trigeminal System PAIN & Temp Fine Touch Pain Lateral SpinoThalamic Dorsal Column System Spinal Touch Principal (Main) Information reaching consciousness goes to the Neocortex, Nonconscious Sensory Information goes to the Cerebellum Somatosensory Information Travels from receptors in the Periphery (skin) to Consciousness in the Cortex The axons of the neurons carry action potentials that transmit the sensory signal. These pathways involve a serial chain. The first order neuron sends it’s axon to synapse with the second order neuron’s soma and dendrites. There are 4 neurons in the serial chain and 3 synapses. The Basic Plan for Somatosensory Information to Consciousness Quaternary (4o ) 4 C o rte x : rig h t le ft Te r t ia r y o (3 ) 3 Thalamus: left R e c e p to r right S e c o n d a ry o (2C r o s s e s ) o Primary (1 ) Crossing occurs either in spinal cord OR brainstem 2 1 S k in • Adequate Stimulus – The stimulus modality to which a sense organ responds optimally. • Generator Potentials are depolarizations in receptors that are graded relative to the intensity and form of the stimulus. 2nd order neuron is located either in spinal cord OR brainstem Spinal Cord Dorsal Root Ganglion Action Potential Initiation Site left Midline Outside the CNS! right Key Elements of the Basic Plan: SS to Consciousness The basic plan for somatosensory information to consciousness involves 4 neurons and 3 synapses. Cell bodies of the primary afferents are located outside of the central nervous system (in the dorsal root ganglion for body information and in the Trigeminal ganglion for head information). Cell bodies of the second order neurons are located either in the spinal cord (anterolateral system) or in the brainstem (dorsal column system). The axon of the second order neuron crosses the midline. Cell bodies of the third order neurons are located in the thalamus (within VPL for body information and VPM for head information). The fourth order neuron is located within the Primary Somatosensory cortex (Brodman’s areas 3, 1, 2). If you lesion the pathway before it crosses you create IPSILATERAL deficits (loss of sensation on the same side of the body as the lesion). If you lesion the pathway after it crosses you create CONTRALATERAL deficits (loss of sensation on the opposite side of the body as the lesion). If you lesion the pathway AS it is crossing, you create BILATERAL deficits (both sides of the body affected). Before = IPSI, After = CONTRA PERCEPTION Cortex LEFT RIGHT After Crossing Before Crossing Thalamus CONTRA STIMULUS Skin This is the site of lost sensation after the lesion IPSI Lesion is ipsilateral to the receptor that begins coding the stimulus Midline Spinal Cord Non-conscious Proprioception Conscious Somatosensation Spinocerebellar Tracts BODY HEAD (IPSILATERAL) Trigeminal System PAIN & Temp Fine Touch Pain Lateral SpinoThalamic Dorsal Column System Spinal Touch Principal (Main) Information reaching consciousness goes to the Neocortex, Nonconscious Sensory Information goes to the Cerebellum Pain and Temperature Pathway: Anterior Lateral System QUATERNARY 4o sy na ps e I II III Primary Somatosensory Cortex 4 IV V TERTIARY 3o VI Thalamus 3 VPL Lateral Spinothalamic Tract Crosses the midline in the Ventral White Commissure Of the Spinal Cord 2 Spinal Cord: Dorsal Horn SECONDARY 2o *ascend 2-3 spinal levels PRIMARY 1o Receptor (skin) MIDLINE DRG 1 in Lissauer’s Tract (cap on dorsal horn) Spinal Cord: Lateral Funiculus Dermatomes & Lissauer’s Tract Dermatome - the area of skin innervated by the sensory portion of a single cranial or spinal nerve. Primary afferents entering at T4 will synapse mainly in T2. Lesion at T2 in spinal cord: Area affected will include T4 since that is where the axons originally entered the spinal cord. Key Elements - Lateral Spinothalamic Pathway Transmits pain and temperature sensation from the body. Located laterally in the spinal cord and remains relatively lateral through the brainstem and midbrain – (you will need to know the exact location – shown to you in video). Crosses in the spinal cord. Called the Lateral Spinothalamic Tract AFTER crossing in the spinal cord. The tract travels from the spinal cord to the thalamus. Key Questions for the Lateral Spinothalamic Tract Where are the cell bodies of origin? Means where are the cell bodies connected to the axons that make up the tract – not where are the first order cell bodies. - Contralateral Dorsal Horn of the Spinal Cord Where does it project or terminate? Means where do those axons SYNAPSE? - Ipsilateral Ventral Posterior Lateral (VPL) of the Thalamus Thalamus MIDLINE Lateral Spinothalamic Tract Spinal Cord: Dorsal Horn SECONDARY 2o Spinal Cord: Lateral Funiculus Somatotopy is Maintained Throughout all CNS Levels S L C T Lateral Spinothalamic Tract – Symptoms Associated with Lesions LEFT RIGHT The Anterior Lateral System (ALS) The Lateral Spinothalamic Tract together with the Anterior Spinothalamic Tract is known as the ALS Anterior Spinothalamic Tract – Coarse or ‘light’ Touch Sy na p s e s in SI C o rte x Sy na p s e s in VPL C o lla te ra ls to Re tic ula r Fo rm a tio n Upper Medulla A s c e nd s in A nte rio r Funic ulus Ve ntra l White C o m m is s ure CROSSES Lower Medulla midline Sy na p s e s in D o rs a l H o rn Spinal cord Lateral Spinothalamic Tract Sk in Anterior Spinothalamic Tract Non-conscious Proprioception Conscious Somatosensation Spinocerebellar Tracts BODY HEAD Trigeminal System PAIN & Temp Fine Touch Pain Lateral SpinoThalamic Dorsal Column System Spinal Touch Principal (Main) (IPSILATERAL) Trigeminal Nerve – Sensory Component – pain, temperature, touch, position sense Trigeminal Ganglion Opthalmic Maxillary Mandibular TRIGEMINAL NUCLEUS Mesencephalic Nucleus (Proprioceptive) Main Sensory Nucleus (fine touch, pressure) Human Brain Coloring Book, 6-11 Spinal Trigeminal Nucleus (pain, temp) Axons of Trigeminal Ganglion Cells Synapse in the Trigeminal NUCLEUS Trigeminal NUCLEUS Trigeminal Ganglion Opthalmic MIDBRAIN Maxillary Mandibular SPINAL CORD Human Brain Coloring Book, 6-12 TRIGEMINAL NUCLEUS Mesencephalic Nucleus (Proprioceptive) Main Sensory Nucleus (fine touch, pressure) Spinal Trigeminal Nucleus (pain, temp) Trigeminal System: All branches of the Trigeminal Nerve project to each of 3 components of the Trigeminal Nucleus Tr igeminal NUCLEUS Mesencephal ic Tr igeminal Nucl eus Tr igeminal Ner ve Opthalmic Maxillary Mandibular Br anches of t he Tr igeminal (V) Ner ve Proprioception Tr ig e min a l G a n g l io n 1 Main Tr igeminal Nucl eus 1 Touch 1 Spinal Tr igeminal Nucl eus 2 Second Order Oral Nucleus Main Nuc to pontomedullary junction Interpolar Nucleus 2 2 Spinal Trigeminal Nucleus Pain and Temp Caudal Nucleus C3 spinal cord Trigeminal System Tr igeminal NUCLEUS Mesencephal ic Tr igeminal Nucl eus Tr igeminal Ner ve Opthalmic Maxillary Mandibular Br anches of t he Tr igeminal (V) Ner ve Proprioception Tr ig e min a l G a n g l io n 1 2 1 2 2 1 Main Tr igeminal Nucl eus Touch Spinal Tr igeminal Nucl eus First Order 2 2 2 Second Order Pain and Temp Trigeminal System Tr igeminal NUCLEUS Tr igeminal Ner ve Opthalmic Maxillary Mandibular Br anches of t he Tr igeminal (V) Ner ve Tr igeminal Gangl ion 1 1 Proprioception 1 1 2 1 Mesencephal ic Tr igeminal Nucl eus 2 2 1 Main Tr igeminal Nucl eus Touch Spinal Tr igeminal Nucl eus First Order 2 2 2 Second Order Pain and Temp Trigeminal System Tr igeminal NUCLEUS Tr igeminal Ner ve Opthalmic Maxillary Mandibular Br anches of t he Tr igeminal (V) Ner ve 1 1 Tr igeminal Gangl ion 2 Main Tr igeminal Nucl eus 2 Touch 2 1 Proprioception 1 1 1 Mesencephal ic Tr igeminal Nucl eus 1 Spinal Tr igeminal Nucl eus 2 2 2 Pain and Temp Similarities between Body and Face Pathways The trigeminal ganglion is functionally similar to the dorsal root ganglion. Both contain cell bodies of the PRIMARY AFFERENT pseudo-unipolar neurons. The Mesencephalic Nucleus of V is a special case because it is the only place within the CENTRAL nervous system that contains primary afferent cell bodies. Trigeminal Nucleus: Spinal Component = Pain & Temp C o rte x 1 Mandibular V II Br anches I X of t he Tr igeminal (V) Ner ve X 2 2 2 1 1 1 2 2 2 VPM MIDLINE Maxillary 1 Spinal Trigeminal TRACT Main 1 T h a la m u s Spinal Opthalmic Tr igeminal Gangl ion 1 1 1 4 Ret icul ar For mat ion 3 VPL Tr igeminal Ner ve Mesencepahl ic Tr igeminal NUCLEUS V E N T R A L T R IG E M IN 0 T H A L A M IC T R A C T Key Questions for the Tracts Spinal Trigeminal Tract Where are the cell bodies of origin? - Ipsilateral Cranial Nerve Ganglia of V, VII, IX, and X Where does it project or terminate? - Ipsilateral Spinal Trigeminal Nucleus C o rte x 1 2 2 2 Mandibular V II 1 Br anches I X of t he Tr igeminal (V) Ner ve X 1 1 2 2 2 VPM T h a la m u s MIDLINE 1 Spinal Trigeminal TRACT Main 1 1 1 1 Ret icul ar For mat ion 3 VPL Tr igeminal Gangl ion Maxillary Where does it project or terminate? - Ipsilateral VPM of the Thalamus Tr igeminal Ner ve Opthalmic Where are the cell bodies of origin? - Contralateral Trigeminal Nucleus 4 Spinal Ventral Trigeminothalamic Tract Mesencepahl ic Tr igeminal NUCLEUS V E N T R A L T R IG E M IN 0T H A L A M IC T R A C T Spinal Trigeminal Pathways Left Right Ventral Trigeminothalamic tract Left Right Lesions and Clinical Deficits - Syringomyelia Gliosis and cavitation in midline of the spinal cord – CSF enters the cord. The larger the cavitation, the more tracts affected. One possible cause is a Chiari Malformation. Other causes include trauma, infection. (anything that compresses the CSF) Symptoms: Bilateral loss of pain and temperature at the level of the lesion (segments involved). Area of lesion http://www.asap4sm.com/ Lesions and Clinical Deficits - Wallenberg’s Lateral Medullary (Wallenberg’s) Syndrome – Symptoms include loss of pain and temperature on the ipsilateral head/face, contralateral loss of pain and temperature in the body, and ataxia. Spinal Trigeminal Tract Trigeminal Nucleus Dorsal Spinocerebellar Tract Ventral Spinocerebellar Tract ALS (lateral spinothalamic tract) Non-conscious Proprioception Conscious Somatosensation Spinocerebellar Tracts BODY HEAD Trigeminal System PAIN & Temp Fine Touch Pain Lateral SpinoThalamic Dorsal Column System Spinal Touch Principal (Main) (IPSILATERAL)