sometosensory system
Terms
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What is the censory receptor of A Alpha
(Group I II) - Proprioceptors of skeletal muscle
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What is the censory receptor of
A Beta - Mechanoreceptors of skin
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What is the censory receptor of
A Delta -
Pain, temperature
Also, mechanoreceptors of skin -
What is the censory receptor of
C fibers - Temperature and pain, Itch (form of crud touch)
- What are the fastest nerve afferents?
- Those supplying proprioceptive information from the muscle and joints
- What are the characteristics of sensory fibers with the largest diameters?
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- associated with touch, pressure, vibration
- Heavily myelinated
-fast action potential conduction
- release neurotransmitter glutamate at the terminal endings - What are the characteristics of sensory fibers with the smallest diameters?
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- lightly or unmyelinated
- pain, temperature
- slower action potential conduction
- release neuroeptide P at the terminal endings - Gray matter of spinal cord is composed of?
- nerve cells of the spinal cord
- White matter of spinal cord is composed of?
- axon cells
- What makes the white matter appear white?
- myelination of axons
- dorsal horn
- contain nerve cells involved in the processing of sensory information
- Ventral horn
- contain nerve cells that innervate skeletal muscles, involved in motor function
- Dorsal column medial lemniscal pathway carries what information?
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touch
pressure
2pt discrimination
propriception - Spinothalamic pathway carries what information?
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pain
temperature
some touch - Which sensory pathway has GOOD spatial and temporal resolution?
- Dorsal column medical lemniscal pathway
- Which sensory pathway has POOR spatial and temporal resolution?
- Spinothalamic pathway
- how is the spinal cord segmented?
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31 pairs
- 8 cervical
-12 thoracic
- 5 lumbar
- 5 sacral
- 1 sacro-coccygeal - Steps of Dorsal column Medial Lemniscal pathway?
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1) Primary order neuron in dorsal root ganglion
2) Secondary order neuron continutes to dorsal column nuclei (Medulla)
3)CROSS OVER MIDLINE
4)Tertiary order neuron reaches thalamus(opposite side of the brain)
5)Reach Primary somatosensory cortex (s1) - Steps of Spinothalamic pathway?
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1)primary order neuron in doral root ganglion
2)secondary order neuron enters spinal cord
3) CROSS OVER in spinal cord/medulla, then travel to brain in lateral region
4) tertiary order neuron reaches thalamus
5) reaches primary somatosensory cortex (intralaminar & ventrobasal nuclei) - Steps of Face sensation pathway?
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1)Large mechanoreceptor axons from face (A beta axons)
2)go through trigeminal nerve (V)
3)primary order neuron in pons area
4)CROSS OVER - contralaterally
5)Secondary order neuron in thalamus
6) Primary sensory cortex (more lateral) - which sensory fibers carry face sensory information?
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A gamma and C fibers
small pain
temperature - Wich sensory info is transimitted in the spinal cord along the SAME SIDE of the body that receives the info?
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(Tectile)
touch
pressure - Which sensory info is transmitted by crossing the midline of the spinal cord?
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Pain
temperature - What is the receptive field?
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a circular area on the skin where pressure is applied to excite the cell (+)
-small area of skin that can activate a nerve cell in the dorsal root ganglion - Describe Dorsal column nuclei?
- the next (after dorsal root ganglion) cluster of cells along the dorsal column pathway
- Do nerves in dorsal root ganglion and nerves in dorsal column nuclei have same/different receptive fields?
- they have different receptive fields
- Explain the lateral inhibition in dorsal column nerve cells
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Pressure applied to skin(dorsal column nerve cell#1) -> fire higher frequence of A.P.
When pressure is applied to different location -> freq of A.P. decreased
Activating 2nd location -> activates different nerve cell(#2)->activation of inhibitory interneuron -> prevents the excitation of dorsal column neuron#1 -
True/False?
All neuron have their won particular receptive field - TRUE
- 4 Reasons for 2point discrimination
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1)Lateral inhibition
2)High density of skin mechanoreceptors
3)small receptive field
4)more representation at the level of somatosensory cortex(more if fewer, parts of body has less receptive fields, harder to detect 2pt discr) ex. Back-not good Figer and lips-good -
True/False
Dorsal and ventral roots are paired in each spinal segment and use the same spinal nerve - T
- ________ and _________ determine the conduction velcity?
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diameter of axon
degree of myelination -
Which has slower transmission?
Pain or touch -
Pain
ex, bee sting - Why not have only big axons?
- too much space and energy
- What is dermatome?
- area of skin innervated by the dorsal roots of a single spinal segment