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Ch 15 Sensory Paths
Ch 15 Sensory pathways and the somatic nervous system
| Question | Answer |
|---|---|
| first order neuron | sensory neurons that deliver sensations to the CNS; found in the dorsal root ganglion or cranial nerve ganglion |
| second order neurons | an interneuron located in the brain stem or spinal cord. Crosses over to the opposite side of the CNS at some point |
| third-order neuron | neurons that reach conscious awareness after synapsing with a second neuron. Located in the thalamus and synapses with the primary sensory cortex of the cerebral hemisphere |
| spinothalamic pathway | carries sensations of poorly localized touch, pressure, pain, and temperature. Contains two tracts: anterior/ventral and lateral tracts. Delivers sensations to reflex centers in the brain stem and larger tracts carry information to cerebral cortex |
| Sensations bound for the cerebral cortex ascend within ___ or ____ | the anterior spinothalamic tract or lateral spinothalamic tract |
| Phantom Limb | caused by activity in the sensory neurons or interneurons along the spinothalamic pathway |
| anterior spinothalamic tracts carry ____ and ____ | crude touch and pressure sensations |
| lateral spinothalamic tracts carry ___ and ___ | pain and temperature sensations |
| posterior column pathway | carries sensations of highly localized (fine) touch, pressure, vibration, and proprioception. begins at peripheral receptor and ends at the primary sensory cortex. Crosses over at medulla oblongata. |
| spinocerebellar pathway | carries proprioception information about skeletal muscles, tendown, and joints to cerebellum. Contains the posterior and anterior spinocerebellar tracts. |
| posterior spinocerebellar tracts are dominated by axons that ___ (do or don't) cross over | don't They reach the cerebellum by the inferior cerebellar peduncle of that side |
| anterior spinocerebellar tracts are dominated by axons that ___ (do or don't) cross over) | do cross over. |
| Referred pain | pain felt in a specific part of the body surface that originates elsewhere |
| The spinal tracts of the posterior column pathway are ___ and ____ | fasciculus gracilis and fasciculus cuneatus |
| fasciculus gracilis | 1st order neuron of the spinal tract of the posterior column pathway that carry information from the inferior half of the body and synapse with the nucleus gracilis in the medulla oblongata |
| fasciculus cuneatus | 1st order neuron of the spinal tract of the posterior column pathway that carry information from the superior half of the trunk, upper limbs and neck and synapse in the nucleus cuneatus |
| decussation | crossing of an axon from left to right or vice versa |
| medial lemniscus | tract on opposite side of the brain that carries information from either fasciculus cuneatus or fasciculus gracilis and synapses with third order neurons |
| in the spinocerebellar pathway, axons of first order neurons synapse on interneurons in ____ | dorsal gray horns |
| anterior spinocerebellar tracts reach the cerebellum by ___ | the superior cerebellar peduncle. They do a double crossing over: once in the spine and once in the cerebellum to be on the same side the stimulus originated. Eventually reaches purkinje cells |
| Cranial Nerves ___, ____, ____, and ____ carry visceral sensory information from the mouth, palate, pharynx, larynx, trachea, esophagus, and associated vessel and glands | V, VII, IX, and X |
| solitary nucleus | major sorting center in the medulla oblongata of visceral sensory information |
| the somatic nervous system controls ____ | contractions of skeletal muscles |
| the ANS controls ___, such as ____, ____, ____, and ____ | visceral effectors such as smooth muscle, cardiac muscle, glands, and adipocytes. |
| Two motor neurons of Somatic Motor Pathways | Upper Motor neurons and lower motor neurons |
| Upper motor neurons | cell body lies in the CNS and synapses on lower motor neuron |
| Lower motor neurons | cell bodies lie in nucleus of the brain stem or spinal cord; innervates a single motor unit in a skeletal muscle. Will make the muscle contract. damage will eliminate voluntary function |
| three motor pathways of the Somatic Motor System | corticospinal pathway, medial pathway, and lateral pathway |
| corticospinal pathway | aka pyramidal system, provides voluntary control over skeletal muscles. starts at the pyramidal cells of the primary motor cortex direct pathway from upper to lower motor neurons |
| three descending tracts of Corticospinal Pathway | Three descending tracts are corticobulbar, lateral/anterior corticospinal. Tracts enter white matter of internal capsule, descend brain stem, emerge on either side of cerebral peduncles |
| Corticobulbar tracts | synapse on lower motor neurons in the motor nuclei of CN III, IV, V, VI, VII, IX, XI, and XII. Innervates motor centers of medial and lateral pathways. Controls skeletal muscles of eye, jaw, face, some neck and pharynx |
| Corticospinal tracts | synapse on lower motor neurons in anterior gray horns of spinal cord. Appear as the pyramids. Two types: lateral and anterior |
| Lateral Corticospinal tracts | Most of corticospinal tracts will go to lateral corticospinal tracts on opposite side of the spinal cord |
| Anterior Corticospinal tracts | Uncrossed corticospinal tracts until reaches the anterior white commissure. Synapse on lower motor neurons in the anterior gray horns |
| Medial pathway | help control gross movements of trunk and proximal limb muscles. Upper motor neurons are in the vestibular nuclei, the superior and inferior colliculi and the reticular formation |
| lateral pathway | control the distal limb muscles that perform more precise movements |
| vestibulospinal tracts | descending fibers of the vestibular nuclei information for medial pathway. direct information for head tilting/position of head |
| tectospinal tracts | axons of upper motor neurons of the corpora quadragemina, i.e the colliculi for medial pathway. Cross opposite side immediately before descent to lower motor neurons. Direct reflex movements to sound or sight |
| reticulospinal tract | carries information from reticular formation for medial pathway. do not cross over |
| rubrospinal tract | carries information from red nuclei for lateral pathway. does cross over |
| basal nuclei and cerebellum process __ and __ over muscle contractions | feedback and coordination |
| two major pathways of basal nuclei | 1.) synapse in the thalamic neurons whose axons extend to the premotor cortex 2.) second group of axons synapses in reticular formation altering output of reticulospinal tracts |
| Two distinct population of interneurons in basal nuclei | ACh, or excitatory, and GABA, or inhibitory |
| The cerebellum monitors ____ and ____ | vesitular sensations (balance) and proprioception (position) |
Created by:
drubin676