Neuroophysio Flashcards
Adaptation of Sensory Receptors
Slowly adapting (Tonic) - muscle spindle, pressure, slow pain Rapid (Phasic)- Pacinian corpuscle, fast pain
2 Sensory receptors
Specialized epithelial cells
Primary afferent neurons
Locations of the sensory pathways
First order neurons: dorsal root or spinal cord ganglia
Second order neurons: spinal cord or brainstem
Third neurons: Thalamus
Fourth order neurons: sensory area of the cerebral cortex
Somatosensory System includes
Sensations of touch, movement, temp, pain
Pathways in the Somatosensory System
Dorsal Column System
Anterolateral System
Senations in the somatosensory system
Dorsal column: fine touch, pressure, two-point discrimination, vibration, and proprioception
Anterolateral: Temperature, pain, light touch
Fibers in the somatosensory system
Dorsal Column System: Group II fibers
Anterolateral: Group III and IVq
Course of the Dorsal Column System
Primary afferent neurons (dorsal root ipsilateral to the medulla: nucleus gracilis and nucleus cuneatus)
Second order neurons: cross the midline and ascend to the contralateral thalamus
Third order neurons
Fourth order neurons
Course of the Anterolateral System
Primary afferent neurons:enter the spinal cord to the dorsal horn
2nd order: cross the midline to the anterolateral quadrant of the spinal cord and ascend to the contralateral thalamus
3rd order
4th order
Destruction of the Thalamus results to
Loss of sensation on the contralateral side
Major somatosensory areas of the cerebral cortex
SI and SII
Map of the body is called
Sensory homunculus
Largest areas represent face, hands, fingers where precisr localization is important
Receptors for pain
Free nerve endings in the skin, muscle, viscera
Neurotransmitter for pain
Substance P
Opioids- inhibition of the release of Substance P
Fibers for past and slow pain
Slow pain: C fibers (aching, burning, throbbing) poorly localized
Fast pain: Group III (rapid onset and offser) localized
