General Somatosensory Systems Flashcards
What are General Somatosensory Systems?
Somesthetic Systems or body/perception
What tissues do somatosensations are monitored by receptors?
Superficial tissues
Deep tissues
What is considered a superficial tissue?
cutaneous skin (eidermis, dermis and hypodermis)
What are deep tissues?
Skeletal muscles, tendons, ligaments, bone
What are general somatosensory modalities?
Unique sensations from somatic tissues
What are the unique sensations that occur in somatic tissues?
1) pain/noxious
2) temperature
3) Light (nondescriminitive) touch
4) Discriminitive touch (fine)
5) Proprioception
6) Vibration
What are the two main general somatosensory systems?
Spinothalammic System
Medial Lemniscus System
What is another name for spinothalmic system?
Anterolateral system
What are spinothalamic system sensations primarily concerned with?
Pain
Temperature
Nondiscriminative touch
What is the Medial Lemniscus System also known as?
Dorsal Column System
What sensations are medial lemniscus system primarily concerned with?
Discriminitive touch
Proprioception
Vibration
How many major neurons typically relay sensory information from peripheral receptors to the cerebral cortex?
3 or 4
What are primary sensory neurons?
Cell bodies in dorsal root ganglion
What are secondary sensory neurons?
Cell bodies in spinal cord or brainstem
What are tertiary sensory neurons?
Cell bodies in the thalamus
What types of neurons are interposed between major neurons?
Interneurons
Can other neurons terminate on and influence or modify secondary pathway neurons?
Yes, therefore they modify transmission of information through the pathway
What can modifications of the pathway circuitry provide?
Modifications of the sensory experience
What are medial lemniscus systems?
Pathways for sensory modalities of discriminative touch,vibration and proprioception
What is discriminative touch?
Fine touch
What are qualities of discriminative touch?
1) The ability to recognize the precise location of a tactile stimulus (eyes closed)
2) 2 point discrimination
3) Graphesthesia
4) Receptors include receptors in cutaneous areas
What is 2 point discrimination?
The ability to distinguish when 2 points are touched simultaneously. Allows and permits to recognize different textures. Resolution of 2 pt touch varies (fingertips and back have different 2 pt touch sensitivity)
What is graphesthesia?
Traced figure identification (ability to identify a familiar pattern traced on the skin with eyes closed)
What are the receptors included in cutaneous areas?
Meissner’s corpuscles and other receptors such as merkel’s endings
What qualities are included in proprioception?
1) Kinesthesia
2) Permits one to appreciate the shape, size and weight of objects (held in the hand)
3) receptors are distributed in articular and periarticular tissues and in muscles and tendons
What is kinesthesia
Information regarding the precise position of a body part (without visual aid) and in the range and direction of movement
What are the receptors found in muscles, tendons, and articular and periarticular tissues (joint capsules, ligaments)?
Neuromuscular spindles
Neurotendinous spindles
Ruffini-like endings
Small pacinian corpuscles
What are vibration sensations?
Rapidly changing or oscillating mechanical stimulus
How are vibrations elicited artificially on the body?
By a tuning fork set in motion and placed on the body
What receptors are included on vibrations?
Pacinian corpuscles
What are the primary neurons of fine touch and vibration for the body except the face?
Large pseudounipolar neurons in the dorsal root ganglia of spinal nerves
What group fibers are the collateral processes of primary neurons in fine touch and vibration for the body except the face?
Group A-beta fibers
What are the peripheral processes of the fine touch and vibration for the body except the face?
supplies a sensory receptor in peripheral tissue
What are the central processes of the fine touch and vibration for the body except the face?
1) Processes that transverse through dorsal rootlets of a spinal nerve and enter the spinal cord through the dorsal root zone
What are the functions of peripheral processes of the fine touch and vibration for the body except the face?
Transmits a “coded” message from the receptor towards the spinal cord
Where do central process (of fine touch and vibration for the entire body except the face) branch?
Enters the ipsilateral dorsal funiculus and branches into ascending and descending collaterals
What type of central process collaterals can modify cord mediated activity in fine touch and vibration for the entire body except the face?
Short ascending and descending collaterals terminate in spinal cord gray to modify cord mediated activity such as reflexes, sensory and motor activity
Where do long ascending collaterals that enter the spinal cord below T6 (of the central process of fine touch and vibration for the body except the face) travel?
Project through the ipsilateral fasciculous gracili to terminate in the nucleus gracilis on the posterior surface of the medulla
Where do long ascending collaterals that enter the spinal cord above T6 (of the central process of fine touch and vibration for the body except the face) travel?
Project through the ipsilateral fasciculus cuneatus to terminate in the nucleus cuneatus on the posterior surface of the medulla
How is the primary neuronal fibers based on location organized in the dorsal funiculus from medial to lateral?
Fasciculus gracillis
- Sacral
- Lumbar
- Below T6
Fasciculus Cuneatus
- Above T6
- Cervical
Which side of the body do neuron cell bodies located in the nucleus gracillis and cuneatus receive information in regards to fine touch in the body (excluding the face)?
Ipsilateral side of the body
Where do the neuron fibers from the nucleus gracillis and cuneatus project in regards to fine touch in the body (excluding the face)?
Project ventrally, decussate and form a fiber tract known as the medial lemniscus
Where does the medial lemniscus ascend in regards to fine touch in the body (excluding the face)?
Ascends the contralateral side of the brainstem
Where do the secondary fibers from the nucleus gracillis and nucleus cuneatus ascend through and where do they
terminate in regards to fine touch in the body (excluding the face)?
Ascend through the medulla, pons and midbrain to terminate on teritary neurons in the thalamus
What order neurons comprise the ventral posterior lateral nucleus of the thalamus for fine touch in the body (excluding the face) ?
Third order
Neuronal fibers that leave the ventral posterior lateral nucleus project through in regards to fine touch in the body (excluding the face)?
The posterior limb of the internal capsule to the post central gyrus and the posterior part of the paracentral lobule of the parietal lobe
True or false: Projection of fine touch infromation into the parietal lobe finishes the process of subjective assessment of data.
False, it initiates the process of subjective (conscious) assessment of the data
What are the primary neurons of proprioception for the body except the face?
Large pseudounipolar neurons in the dorsal root ganglia of spinal nerves
What group fibers are the collateral processes of primary neurons in proprioception for the body except the face?
Group A-alpha fibers
Group A-beta fibers