Neurophysiology 2: Somatosensation And Ascending Tracts (Lecture 76) Flashcards
What are somatosensory receptors for?
General senses are relatively simple in structure and physiology
What do somatosensory receptors consist of?
Primary afferent neuron
(May or may not be encapsulated)
What are four examples of somatosensory receptors?
Thermoreceptors, nociceptors, mechanoreceptors, Proprioceptors
Once a primary afferent neuron fires, where does the signal go?
Up the nerve fiber of the primary afferent neuron Or the nucleus of the trigeminal nerve for structures of the head
Out of the sensory functions, which one has the largest fibers? Smallest?
Largest fibers: Proprioceptors
Smallest fibers: pain, temperature, itch
Do larger or smaller fibers have faster conduction velocity?
Larger fibers= faster
smaller fibers = slower
What are the functions of the spinal cord?
Conduction-afferent and efferent (structural and functional link between brain and body)
Neural integration
Reflexes
What is contained in the grey matter of the spinal cord?
Neuronal cell bodies
What does the dorsal horn house?
Axons of sensory neurons and cell bodies of interneurons
What does the ventral horn house?
Cell bodies of somatic motor neurons
What does the lateral horn house?
Cell bodies of autonomic motor neurons
Only present T1-L3
What does gray commissure of the spinal cord contain?
Contains unmyleinated axons connecting left and right gray matter
What does the white matter within the spinal cord contain?
Myelinated axons
What is contained within the myelinated axons of the white matter of the spinal cord?
Columns or funiculi
Tracts or fasciculi
Describe the conscious somatosensory projection pathway
First-order neuron
-from body, enter the spinal chord via dorsal root
-from head, enter via cranial nerve (trigeminal)
Second order neuron
-projects from the CNS cranially
-decussation to contralateral side
-end in thalamus
Third order neuron
-thalamus to primary somatosensory cortex of cerebrum
What is the fasciculus cuneatus?
Fiber bundle that carries tactile and proprioceptive information from cranial trunk and thoracic limb
What is the fasciculus gracilis?
Fiber bundle that carries tactile and proprioceptive information I from caudal trunk and pelvic limbs
What do the fasciculus cuneatus and gracilis both detect?
Conscious proprioception , touch, pressure, vibration
In subconscious proprioception, at least ______ neuron pathways leading to the ______ cerebellum .
2
Ipsilateral
What does the spinocerebellar tract do?
Relays unconscious proprioceptive information from the caudal trunk and pelvic limbs
What does the spinocuneocerebellar (cuneocerebellar) tract do?
Relays unconscious proprioceptive information from the cranial trunk and thoracic limbs
What type of pathways are nocicpetive pathways?
Complex, multisynpatic, ipsilateral and contralateral pathways
What is the clinical significance of nocicpetive pathways?
Loss of nocicpetion is a poor prognostic indicator
What two tracts are associated with nociceptive pathways ?
Spinothalamic tract
Spinocervicothalamic tract
What do viscerosensory afferent (GVA) travel with?
ANS fibers
What tract do viscerosensory afferent (GVA) travel?
Spinothalmic tract
Ascend to cerebrum for conscious perception
What is referred pain?
Many somatic and visceral sensory neurons send signals via the same ascending tracts within spinal cords. Somatosensory cortex is unable to determine true source
Ex: heart attack
What fibers make of viscerosensory afferent (GVA)?
A delta and C fibers
