Neuro Somatosensory System
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The somatosensory system allows us to distinguish shapes of objects, feel deep pressure, and warmth. Receptors are found ____ in the body.
throughout the body
The somatosensory system is made up of four senses: ___, ___, ___, and __ __.
- Body position
Touch is regulated by ____receptors. These receptors are sensitive to physical distortion to the membrane such as bending, stretching, or twisting. Each type of mechanoreceptor carries its own type of information.
Mechanoreceptive axon selectivity depends on the ___ of its ending.
The membrane is ___, which opens __ channels causing ___, which then creates ___ potential AP.
- Compressed (energy to nerve terminal)
Primary ___ axons bring information from the sensory receptors to the spinal cord or brainstem. There are 4 different types of axons that carry different information which depends on the size of the axon and presence of myelin. These are:
- 1. Proprioceptors of skeletal muscle
- 2. Mechanoreceptors of skin (touch)
- 3. Pain, temperature
- 4. Temperature, pain, itch
- **Axons are in order from Fastest--Slowest
Information from receptors in the ___ enters the CNS via ___ ___.
Information from receptors below the head enters the spinal cord via __ __.
A ___ is a skin area connected to a single sensory spinal nerve which is connected to a specific part of the body.
The special senses are composed of ___ neurons, whereas the somatosensory system is composed of ___ neurons. They transmit sensory information from the __ and __ to the CNS and are found within ganglia and the dorsal root.
A peripheral axon carries AP to the cell body, information comes in and synapses in dendrites. The central process ends in the terminal butons and carries AP from the cell body to the CNS.
Primary affarent axons enter the __ __ and branch. One branch synapses on second-order __ neurons in the dorsal horn, and the other branch goes up to the brain.
(in the brainstem, synapse on Cranial nerves)
Touch pathways carry information about __ and __ __ from the lower body (the __ __) and the upper body ( the __ ___ to the somatosensory cortex. The fasciculus gracilis and cuneatus make up the dorsal column-__ __ pathway.
The trigeminal nerve carries information about touch from the __ to the somatosensory cortex.
- limb position
- Fasciculus gracilis
- fasciculus cuneatus
- medial lemniscal
The somatosensory cortex in the parietal lobe is the most complex. The size of the cortex is devoted to an area depending on the __ and __ of sensory input. The 3 areas of the parietal lobe involved are the __ __ __, __ __ __, and __ __ __. The primary somatosensory cortex receives most information from the __ and sends information to secondary and/or posterior parital cortex.
- primary somatosensory cortex
- posterior parietal cortex
- secondary somatosensory cortex
*Remember the homonculus is also located here, as well as the motor cortex
In the posterior parietal cortex, lesions usually occur in the __ hemisphere, causing neglect syndrome.
Damage can also result in __, or tactile __, meaning a person can still feel but can't identify objects by touch.
In the posterior parietal cortex, simple sensory information converge to generate complex __ representations.
Pain is detected through these kinds of receptors and is detected through the __ and __ (in the body).
Free nerve endings that signal that body tissue is being damaged/unmyelinated are called ___. They are activated by any stimuli that can cause pain (e.g. stepping on a tack opens sodium channels)
The feeling or perception of negative sensations is called __.
The process that provides the signals that trigger pain is called ___.
The ___ does not have nociceptors, but the nerves, meninges, and vessels do.
The two main pain pathways are the __ and __.
The __ pathway carries information about pain and temperature from the body to the brain.
The __ pathway carries information about pain and temperature from the face and head to the brain. (pons-->thalamus-->prim. som. cortex)
Strong __, stress, or determination can suppress feelings of pain.
___ gray matter in the midbrain can influence the raphe nuclei, depressing nociceptive neuronal activity.
These types of receptors are sensitive to temperature.
Thermoreceptors in the hypothalamus and spinal cord regulate __ __.
Thermoreceptors in the __ sense temperature in the __.
Temperature sensitivity is not uniformly distributed. Warm receptors detect 30-45 degrees C (86-115F) and cold receptors sense 10-35 degrees C (50-80F).
Temperature pathways are the same as __ pathways.
Cold receptors fire until about 20 degrees C, then cold becomes anesthetic and numbs.
Pain (spinothalamic and trigeminal)
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