Ascending Pathways PDF

Ascending pathways László Ákos Kovács MD. Ph.D. University of Pécs, Medical School 30.10.2020.  Definitions Peripheral nerve: nerve fiber bundle(s) in the peripheral nervous system (e.g.: femoral nerve) Tract: nerve fiber bundle(s) in the central nervous system (e.g.: dorsal lem...

Ascending pathways László Ákos Kovács MD. Ph.D. University of Pécs, Medical School 30.10.2020.  Definitions Peripheral nerve: nerve fiber bundle(s) in the peripheral nervous system (e.g.: femoral nerve) Tract: nerve fiber bundle(s) in the central nervous system (e.g.: dorsal lemniscus, pyramidal tract) Ascending tracts receive information from the peripheral nervous system and send it via spinal cord and brainstem to the higher-order centers of the central nervous system.  Type (quality) of sensations: Epicritic sensations: Protopathic sensations: „Fine” touch Crude touch Vibration Temperature Proprioception Pain mechanoreceptors, Golgi mechanoreceptors, tendon organ, muscle thermoreceptors, spindle nociceptors  Epicritic sensations - Object’s shape, form recognition - Two point discriminations - Vibration - Proprioception (tension of muscles tendons,…) mechanoreceptors (Meissner’s corpuscles, Pacinian corpuscles) muscle spindle, golgi tendon organ) Dorsal column, medial lemniscus system (red and blue) Trigeminothalamic tracts – epicritic and conscious proprioceptive informations coming from the face (green) Attention please! This schematic figure does not mark the synaptic connections! Dorsal column, Cerebral cortex medial lemniscus system (postcentral gyrus) Thalamus (ventral postero-lateral nucleus) Third-order Cuneate Medial neuron nucleus lemniscus Cuneate Gracile fasciculus nucleus Second-order First-order neuron neuron Spinal Gracile ganglion fasciculus Trigeminothalamic tracts – epicritic (+conscious Cerebral cortex proprioceptive) informations (postcentral gyrus) coming from the face Thalamus (ventral postero- medial nucleus) Third- order neuron Dorsal First- trigeminal ordr lemniscus neuron (Ventral) Trigeminal Trigeminal lemniscus ganglion Second-order Principal sensory nucleus neuron for the trigeminal nerve  Protopathic sensations - Crude touch and pressure (texture, wearing suit) - Temperature (cold, hot) - Pain - (Itching) mechanoreceptors, thermoreceptors, nociceptors Spinothalamic tract (purple) (Ventralis) Trigeminal lemniscus – protopathic sensations coming from the face (brown) Attention please! This schematic figure does not mark the synaptic connections! Spinothalamic tract Cerebral cortex (postcentral gyrus) Thalamus (ventral postero-lateral nucleus) Third- order neuron Spinal ganglion First- Spinothalamic order tract neuron Second-order neuron Intermediate grey matter  Cerebral cortex (Ventral) Trigeminal Third- (postcentral gyrus) lemniscus – protopathic order sensations coming from the neuron face Thalamus (ventral postero- medial nucleus) First- order neuron (Ventral) Trigeminal Trigeminal lemniscus ganglion Second -order Spinal tract nucleus for neuron trigeminal nerve Spinocerebellar and trigeminocerebellar tracts (unconscious proprioceptive informations) Good to know! Cuneocerebellar tract Cerebellum The third-order neurons are Rostrocerebellar located in the tract cerebellum Dorsal Ventral Trigeminocerebellar spinocerebellar tract spinocerebellar tract tract Functional remarks I. A sensory homonculus and the cortical somatotopy Organs and skin areas are represented different level (areas) on the surface of the sensory cortex If our receptive fields and our receptors representation (density) would be the same on the body (surface) this would be the real view of our body Functional remarks II. Somatotopic organization in the spinal cord and thalamus Sacral Lumbal Thoracal Cervical Head and face Neck and the body (trunk and limbs) Sacral Lumbal Cervical Thoracal Functional remarks III. Functional organization for spinothalamic tract Lateral part (carrying information from thermoreceptors and nociceptors) The spinothalamic tract is also known as Anterior part (carrying antero-lateral system information from mechanoreceptors) Functional remarks IV. Other targets of the spinothalamic tract (axon collaterals) Thalamic nuclei Centromedian (centromedian nucleus): nucleus co-activates brain centers helping to memorize the happenings and associate it with emotions (such as anger, sadness) Periaqueductal gray matter Brainstem centers: activate the body to avoid the potential threat (pain) and also help to decrease the pain (analgesia). Reticular formation Spinal cord has own short (some segments long) tracts that divide and share the incoming informations (pain) (Lissauer zone, Fasciculus proprius)  Functional remarks V. Head Zones Dermatomes Gallbladder Diaphragm Dermatome: skin area innervated by spinal Oesophagus Hearth nerve. Liver Head zone: visceral (gallbladder) Stomach pain is project (radiate) to the dermatome (cause: the second Kidneys Bowels order neurons located urethers in the same nuclei (zone), where the informations converged in the spinal cord, thus the higher order centers cannot differentiate the origin of the pain. Medical cases (reports) I. Myelopathies e.g.: Funicular myelosis Cause: shortage of B12 vitamin (cobalamin), or folic- acid can lead to demyelination of dorsal column’s myelin sheats. Symptoms: Spinal ataxia (patient cannot feel the floor properly, and walks unsteadily) Lhermitte-sign: eletric shock- like pain feeling during head tilting www.regitankönyvtar.hu  Below the injury level: Medical cases (reports) II. Brown-Sequard syndrome: lesion at spinal cord level Sensory loss of pain, itching and temperature feeling Sensory loss of fine touch and proprioception Thank you for your attention! Summary and questions: -What is the locations of the first-order neurons? What type of neurons they are? -Which tracts are crossing and which are not? -Why we remember better, why we feel sadness/angry during, after painful stimuli? -Where the visceral pains project to (to which dermatomes)? Why the Head zones are important for us? -Which nucleus/area is the guard of the brain? (Which nucleus facilitates the ascending informations)