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35 Cards in this Set
- Front
- Back
"soma to sensory"
soma & sensory |
soma=body; sensory= sensation
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3 seperate but interacting systems of the somatosensory system
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exteroceptive system (senses external stimuli that are applied to the skin)
proprioceptive system (sesnes information about the position of the body from receptors in muscles, joints, and organs of balance |
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3 stimuli that the exteroreceptive somatosensory system senses:
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1. mechanical stimuli= touch
2. thermal stimuli= temperature 3. nociceptive stimuli= pain |
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What does the somatosensory system sense?
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external and internal sensory information from your body
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How does the hierarchal organization of somatosensory system work?
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Association cortex
Secondary Sensory cortex Primary sensory cortex Thalamus Receptors |
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Free nerve endings
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cutaneous receptors- receptors on the skin- that respond to temperature change and pain
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Pacinian corpuscles
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cutaneous receptors located underneath the skin (but before the fat) that respond to touch BUT ONLY TO RAPID VIBRATIONS
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Merkel's disks and Ruffini endings
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cutaneous receptors (receptors of the skin) that adapt slowly; gradual skin indentations and skin stretch
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What are all the cutaneous receptors?
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free nerve endings, Pacinian corpuscles, Merkel's disks, and Ruffini endings
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Organization of somatosensory processing: dorsal root
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where axons carrying sensory information from the cutaneous receptors gather to enter the spinal cord
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organization of somatosensory processing: dermatome
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the area of the body that sends sensory information into the dorsal roots
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*sensory neurons travel into the ------ and synapse on neurons in the ----- which will carry the information to the brain
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Sensory neurons travel into the DORSAL ROOT and synapse on neurons in the DORSAL HORN (DORSAL ROOT GANGLIA) which will carry the information to the brain
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2 major ascending sensory pathways: (& their responsibilities)
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1. dorsal-column medial lemniscus system: touch & proprioception
2. anterolateral system: pain & temperature |
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what is the organization of the DORSAL-COLUMN MEDIAL LEMNISCUS SYSTEM
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7. SOMATOSENSORY ASSOCIATION CORTICES<--
6. SECONDARY SOMATOSENSORY CORTEX<-- 5. PRIMARY SOMATOSENSORY CORTEX<-- 4. VENTRAL POSTERIOR NUCLEI (THALAMUS)<----- 3. dorsal column nuclei (medulla) (CROSS OVER) 2. spinal cord 1. touch receptors |
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what is the organization of the ANTEROLATERAL SYSTEM
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6. SOMATOSENSORY ASSOCIATION CORTICES
5. SECONDARY SOMATOSENSORY CORTEX 4. PRIMARY SOMATOSENSORY CORTEX 3. THALAMIC NUCLEI 2. spinal cord (cross over) 1. temperature and pain receptors |
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How to the tracts of the anterolateral system differ?
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The 3 tracts of the anterolateral system differ:
-in whether or not they synapse (and where) prior to reaching the thalamus -where in the thalamus they synapse |
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What are the three tracts of the anterolateral system?
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1. spinothalamic (up the cord & into the thalamus- ventral posterior nucleus)
2. spinoreticular (synapse reticular activatig system; 3rd order neurons to the thalamus- parafascicular nurclei and intralaminar nuclei) 3. spinotectal (synapse in the tectum) |
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somatosensory cortex- what is the organization?
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The organization of the somatosensory system is somatotopic (organized according to a map of the body's surfaces- the map being called the somatosensory homunculus)
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somatosensory homunculus
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map or the body's surface in the somatosensory cortex
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main characteristics of the somatosensory system
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-somatotopic (organized according to a map of the body's surfaces)
-map=somatosensory homunculus -"strips" corresponding to each sensation we feel (e.g., touch vs. temperature) -Association cortex- in the posterior parietal lobe |
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where is the association cortex?
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in the posterior parietal lobe
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Reorganization
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-Reorganization is the major process through which function is restored in the CNS after damage
-Even in adults, our brains are capable of reorganizing themselves in response to experience or damage |
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phantom limb
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Happens after reorganization, phantom limb is the sensation that a limb is still attached to the body after amputation
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phantom pain
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happens after reorganization, phantom pain is the sensation of pain in a limb that has been amputated
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Phantom pain elicited by?
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Phantom pain can be elicited by touching other parts of an amputee's body
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In amputees, what needs to be stimulated to produce pain in missing fingers?
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In amputees with phantom pain, stimulation of the lips produces pain in the missing fingers--> imaging shows that the lip cortical area on the contralateral side of the brain has moved into the finger cortical area
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Pain vs. Nociception
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The sensation of pain and the affect (emotion) of pain are anatomically and functionally seperated: the anterior cingulate cortex mediates the emotion of pain
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Which part of the brain mediates the emotion of pain?
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the anterior cingulate cortex mediates the emotion of pain
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Descending pain control; which systems can control pain?
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-Neurons in areas of the mesencephalon (specially, in the periaqueductal gray, PAG) can control pain
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Descending pain control: how do you reduce reduction of pain?
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-Electrical stimulation or the direct delivery of opiates to the neurons in the mesencephalon (especially, in the periaqueductal gray) can produce analgesia (pain reduction). The same opiate systems mediate the analgesic effect of stress.
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Which opiate systems mediate the analgesic effect of stress?
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The neurons in areas of the mesencephalon (specially, in the periaqueductal gray) have opiate systems that mediate the analegsic effect of stress
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How do endogenous opiates work?
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Endogenous opiates (endorphins) increase the activity of pariaqueductal gray neurons that stimulate serotonergic neurons in the raphe nuclei. The serotonin output stimulates inhibitory interneurons that enter the spinal cord
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What can spinal injuries do to one's sensitivity to pain?
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Spinal injuries can damage descending pain-control tracts and result in increased sensitivity to pain
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Pain control: gate theory
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-two types of nociceptive nerve fibers terminate in the dorsal spinal cord:
1. Ao: fast, relatively thick myelinated fibers 2. C: small, unmyelinated fibers Other large-diameter A & B fibers do not transmit pain stimuli |
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Pain control: gate theory (i, ii, iii)
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i. NO STIMULATION. The inhibitory interneuron (I) blocks the signal in the projection neuron (P). The "gate is closed" and therefore NO PAIN.
ii. NON-PAINFUL STIMULATION. Large nerve fibers are activated primarily. This activates the projection neuron (P), but also activates the inhibitory interneuron (I) which then blocks the signal in the projection neuron (P). The "gate is closed" and therefore NO PAIN. iii. PAIN STIMULATION. Small nerve fibers become active. They activate the projection neurons (P) and block the inhibitory interneuron (I). Because activity of the inhibitory interneuron is blocked, it cannot block the output of the projection neuron. The "gate is open," therefore, PAIN!!! |