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Neuro Chapter 7
Term | Definition |
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Somatosensory System | How sensation is carried from your PNS to your CNS and how it is processed. PNS awareness of: -Pain -Temperature -Touch -Conscious proprioception |
Hierarchy of Sensory Fibers | Specialized Receptors Stimuli into Neural Signal Single NerveFiber Sensory Fiber Bundle Spinal Nerve Dorsal Root Ganglia Dorsal Column Nuclei Spinal Motorneurons-reflex Reticular Formation-going to brain Thalamus Primary & Assoc Sensory Cortex |
Somatotopic organization in tracts and cortex | Meaning there is information traveling through nerves made specifically for that type of info and different parts of brain will process that information. |
Mechanoreceptive Sensation | Mechanical displacement of nerve endings Responsible for touch (fine and diffuse), pressure, vibration, kinesthesia (sensation of movement of limbs and the speech organs) |
Thermoreceptive | Cold and Heat sensation |
Nociceptive | Pain sensation |
Adaptiveness of receptors | Reduction of response to stimuli over time (following initial stimulation, how soon can you tune out that stimuli, ex: pressure you feel when sitting, eventually you no longer feel it so theses receptors are very adaptive.) |
Sensory Receptors with Encapsulated Endings | -Responsible for tactile sensation -Highly Adaptive Two types: Pacinian corpuscle Meissner’s corpuscle |
Sensory Receptors with Free Nerve Endings | Responsible for sensation of pain, temp, some tactile -Nonadapting |
Sensory Receptors with Expanded Tip Endings | -Responsible for tactile and temp sensation -Moderately adapting (i.e. you can get use to very cold or hot weather over time) |
3 order neuron organization | Transfer of stimulus from PNS to brain. Goes thru 3 neuron organization: 1st Order:Dorsal Root Ganglion 2nd Order:Enter CNS @ spinal cord or brainstem Project to opposite side crossing midline to thalamus 3rd Order: Thalamus neurons project to cortex |
Dorsal Column-Medial Lemniscal (or Epicritic System) | Type of Somato-sensory system that deals with Important for position sense of speech muscles (proprioception), awareness of limb movement (kinestheia) and skilled movements such as fine and deep touch. -Deccussation occurs at level of brain stem |
Proprioception | Awareness of limb position and where in space is jaw or tongue |
Kinesthesia | Awareness of limb movement. Is structure moving or not. |
Anterolateral (or Protopathic System) | Most primitive Somato-sensory system. -Responsible for Pain, temperature and diffuse touch Two important tracts: Lateral spinothalamic tract Anterior spinothalamic tract -Decussates at level of spinal cord |
Stereognosis | Fine touch discrimination |
Graphesthesia | Recognizing numbers written on body Two and multiple point touch Deep touch |
Meissner’s and Pacinian Corpuscles | -Type of Receptor in the Dorsal Column-Medial Lemniscal System -Encapsulated end receptors -Highly sensitive and adaptable |
Muscle Spindle Organs | -Type of Receptor in the Dorsal Column-Medial Lemniscal System. Important for: -Kinesthesia -Proprioception |
Neural Pathways in the Dorsal Column-Medial Lemniscal System | Two patways: 1) Fasciculus Gracilis 2) Fasciculus Cuneatus Both pathways are located in the spinal column. Mediate discriminative touch from different body areas; follow the 3-neuron organization |
Path of the Neural Pathways in the Dorsal Column-Medial Lemniscal System | 1st order neurons enters at Spinal Ganglion 2nd order neurons found in the Gracilis or Cuneatus Nucleus 3rd order neurons go through the Medial Lemniscus to Thalamus 3rd order neurons take through Thalamus to the sensory Cortex |
Fasciculus Gracilis | Neural tract/bundle -Starts at the Sacral to Midthoracic Level and goes almost whole length of spinal cord -Responsible for sensation of the Lower Body |
Fasciculus Cuneatus | -Neural tract/bundle -Found only Above Midthoracic Level -Important for sensation in the Upper Body |
Nucleus Gracilis and Nucleus Cuneatus | Name change when Fasciculus Gracilis and Fasciculus Cuneatus enter the Medulla |
Medial Lemnicus | The Nucleus Gracilis and Nucleus Cuneatus fuse together at level of the mid brain to make one nerve bundle |
Where is pain processed? | Pain is processed (how much it hurts) at level of thalamus, hypothalamus, hypocampus and the reticular formation in the brainstem. However WHERE you feel the pain is processed at the level of the cortex. |
Lesion above Midline crossing in the Dorsal Column-Medial Lemniscal System | Lesions above the brainstem will be located contralaterally to the loss of sensation (lesion in brain will cause loss of sensation on opposite side of lesion) |
Lesions below midline crossing in the Dorsal Column-Medial Lemniscal System | Lesions below the brainstem will be located ipsilaterally to the loss of sensation (i.e. Lesions in spinal cord will cause loss of sensation on same side of lesion) |
Romberg Test | Tests used to judge integrity of the Dorsal Column-Medial Lemniscal System Ask patient to stand with eyes closed. -If they loose balance probably loosing proprioception in lower body |
Main Receptors for the Lateral Spinothalamic Tract | Free Nerve Endings |
Nocicoceptors | Receptors for pain in the Lateral Spinothalamic Tract |
Substantia Gelatinosa and Substantia Proprius | Where 1st order neurons connect with 2nd order neurons BEFORE decussation |
Lesion above midline crossing in Anterolateral System | Midline crossing is at the spinal cord for the Anterolateral System. Therefore Brainstem and most spinal cord lesions result in a contralateral loss of pain etc... |
Lesion below midline crossing in Anterolateral System | Midline crossing is at the spinal cord for the Anterolateral System. -Lesion in PNS or area of spinal cord BEFORE the midline crossing will result in symptoms n the same side or ipsilaterally. |
Dermatome | Refers to the sensory area innervated by the neurons in a single dorsal root ganglion |
Referred pain | When pain is located one part of the body with no pain receptors so it is felt in another site (ex the heart pain maybe felt in arms upper chest) |
Analgesia | Altered pain sensation where there is No pain sensation. Can happen if Dorsal root Ganglia is cut off. |
Hypolgesia | Decreased pain (higher threshold) |
Hyperalgesia | Increased pain (lower threshold) |
Discrimination of Diffuse touch in Anterolateral System | Ability to tell where touch is coming from (if you have a person close eyes and you touch a particular part of body, person cannot locate where the touch is coming from) |