Central Somatosensory System Flashcards
What is managed at the spinal level in local neural circuits or by cerebellum to adjust movements and posture
Somatosensory Information
Where does perception (interpretation of sensation) take place?
Thalamus and cerebral cortex
Why is sensory feedback important?
Goal-directed movement
Why are patients with somatosensory deficits more prone to injury?
They are unable to percieve excessive pressure, temperature, or stretch due to joint damage
What is the following disorder called?
Individual is not able to percieve physical pain in any part of the body when injured
Congenital Insensitivity to pain
What do pathways with high accuracy signals transmit?
Acurate signals about location, size, and intensity of stimulation
In high-accuracy pathways a ____ of information similar to anatomic organization of the body is established
Somatotopic arrangement
What is the following a definition of?
When a specific part of the body is associated with a distinct location in the central nervous system
Somatotopic arrangment
Where in the body do we see somatotopic arrangment?
In the spinal cord
What is somatotopically organized where it recieves information form the hands in a specific location and information from the feet in another location?
primary somatosensory cortex
Where is the map of the parts of the somatosensory cortex that corresponds to specific parts of the body created and represented?
Sensory homunculus
Are low-accurary pathways organized somatotopically?
No they are not well localized
In the 3-neuron pathway where does the first neuron bring information from?
From a peripheral receptor into the central nervous system
In a 3-neuron pathway what does the second neuron do?
Signals information to the thalamus
In a 3-neuron pathway what does the third neuron do?
Conveys information from the thalamus to the somatosensory cortex
What is the following a definiton of?
bundle of axons with the same origin and common termination
tract, column, leminscus, or fasicle
All the same thing
What are somatosensory pathways named after?
Origin and termination of the tract that contains the second neuron in the sequence
What is the following somatosensory information pathway called?
This pathway conveys information about location and type of stimulation to conscious awareness in the cerebral cortex
Conscious Relay Pathway
What is the following somatosensory information pathway called?
This pathway transmits information to many locations in the brainstem and cerebrum and use pathways with variable numbers of nuerons
Divergent Pathway
Which pathway transmits information with high accuracy?
Conscious Relay Pathway
What is the following somatosensory information pathway called?
This pathway transmits nonconscious proprioceptive and other movement-related information to the cerebellum
Nonconscious Relay Pathway
What Conscious Relay Pathway is this?
- Light touch and conscious proprioception
- Terminates in the primary somatosensory cortex
Dorsal Column Medial Leminscus
What Conscious Relay Pathway is this?
- Fast nocicpetion and temperature
- Terminates in the primary somatosensory cortex
Spinothalamic
What Divergent Pathway is this?
- Slow nociception
- Terminates in the periaqeductal gray of midbrain, superior colliculus
Spinomesencephalic
What Divergent Pathway is this?
- Slow nociception
- Terminates in the reticular formation
Spinoreticular
What Divergent Pathway is this?
- Slow nociception
- Terminates in the amygdala, ventral striatum of basal ganglia, insular cortex
Spinolimbic
What Nonconscious Relay Pathway is this?
- Movement-related information
- Terminates in the cerebellum
Spinocerebellar
What type of information does the dorsal columns in conscious relay pathways carry?
Light touch and conscious proprioception
What type of information do the anterolateral columns of the conscoius relay pathway carry?
Nociceptive, temperature, and crude touch
Tracts with information for discriminative percption of stimuli localized with fine resolution are processed by what?
Cerebral cortex
In the DCML pathway what happens when the sensory receptor is stimulated by light touch or conscious perpeption?
DCML: dorsal column medial leminscus
the receptor depolarizes generating an axon potential that is transmitted along distal axon and then proximal axon in the PNS
Where does the proximal axon go when it is stimulated by DCML pathway?
It enters the spinal cord via the dorsal root and ascends in the ipsilateral dorsal column
Where do axons from the lower limb and lower trunk (below T6) reside in?
Medial section of the dosral column
What is the following a defintion of?
Medial section of the dorsal column
Fasciculus Gracilis
Where do axons from the upper trunk, upper limb, and neck (above T6) reside?
Lateral section of the dorsal column
What is the following a defintion of?
Lateral section of the dorsal column
Fasciculus Cuneatus
Axons that enter in fasciculus gracilis synapse with what?
Second-order neurons in the nucleus gracilis of the medulla
Axons in the fasciculus cuneatus synapse with what?
second-order neurons in the nucleus cuneatus of the medulla
Where are these axons from?
These axons decussate as internal arcuate fibers, then ascend to the thalamus as the contralateral medical lemniscus tract
axons from second-order neuron
Where do second-order neurons synapse?
Area of the thalamus called ventral posterolatral nucleus
What do third-order neurons connect?
Ventral Posterolateral nucleus to the thalamus to the somatosensory cortex
What is the pathway that the sensory information of light touch and conscous proprioception take?
Ascends and synpases in the ventral posterior lateral nucleus of the thalamus on third order neurons to the primary somatosensory cortex
Where is the primary somatosensory cortex located?
In the postcentral gyrus
Which area of the brain as the following function?
Analyzing information from the primary somatosesory cortex and the thalamus to provide sterogenesis and memory of the tractile and spatial environment
Secondary somatosensory area
Where is the secondary somatosensory area located?
Located posterior to the primary somatosensory cortex
What is the following a defintion of?
The area of the primary somatosensory cortex devotes to a specfic part of the body; surrounds the cortex
Homunculus
What does the homunculus illustrate?
Proportions and arrangement of cortical areas that contain representation of the surface of the body
Which two pathways ascend together in the anterolateral spinal cord?
- Conscious Relay Pathway
- Divergent Pathway
What do the free nerve endings in first-order neurons respond to?
Noxious mechanical stimulation or to noxious meachnothermal stimulation
How do the peripheral axons of the A(delta) fibers transmit information?
From free nerve endings along lightly myelinated axons to the cell body
Which axon is this?
Enters spinal cord then branches to several levels of the spinal cord in the dosrolateral tract before entering and terminating inthe dorsal horn
Central axon
Which axon is this?
This axon crosses the midline in the anterior commissure, then ascends to the thalamus in the spinothalamic trat
Axon of the second-order neuron
Which neuron is this?
This axon arises from ventral posterolateral nucleus and projects to the primary and secondary somatosensory cortices
Third-order neuron
What is the following somatosensory information called?
Conveys nondiscriminative tractile information and is transmitted by C fibers
Crude touch
Where does crude touch project?
Anterior and posterior insula
What is discriminative temperature information detected by?
Specialized free nerve endings of small myelinated and unmyelinated neurons
A(delta) fibers carry impulses produced by ___
cooling
C fibers carry information regarding ____
Heat
In the spinothalamic tract fibers carrying information from the lower body are found ____
laterally
In the spinothalamic tract fibers from higher levels are found ____
Medially
Ascending axons in the spinothalamic tract are ____ neurons and most ascend ____
second order; contralaterally
Where do the second-order neurons in the dorsal column and spinothalamic tracts end?
Ventral posterolateral nueclus of the thalamus
Third-order neurons from dorsal column and spinothalamic pathways project from the ____ to the ____ cortex,
Thalamus; Primary Somatosensory Cortex
Responses the nociception depend on a divergent ascending group of neurons called the ____
Medial nociception system
Where do medial nociception system projection neurons synapse?
Medial locations in the CNS
What are the first-order neurons of the slow nociceptive pathways?
Small, unmyelinated C fiber that transmits information to the spinal cord the same way it does as first-order neuronin spinothalamic pathway
Aching, poorly localized pain is which slow nociceptive tract?
Spinolimbic
Which two areas of the midbrain does spinoemesencephallic tract transmit slow nocicpetive information?
Superior colliculus and peraqueductal gray
What is the role of superior colliculus?
Visual reflexes
What is the role of periaqueductal gray?
Activiates descending tracts that moduclated incoming nocieptive signals and is part of descending nociceptive control system
Where does spinoreticular ascending tract terminate?
Brainstem Reticular Formation
