C13 5-6 Flashcards
What are the common characteristics of pathways?
Decussation, paired tracts, series of 2-3 neurons.
Deccusation?
Cross over from one side of the body to the other. Contralateral/ipsilateral; over 90% of pathways decussate, but the point of deccusation varies
What are the components of a sensory conduction pathway?
??
What are the neurons in a sensory pathway?
First order/primary sensory neurons, second order/secondary sensory neurons, third order/tertiary sensory neurons
First order sensory neurons
Sensory neuron: dendrites are part of the receptor that detects a specific stimulus. Cell bodies: dorsal root ganglia Axon: Dorsal root
Second order sensory neurons
Interneuron: Cell body: Dorsal horn of spinal cord or a brain stem nucleus Axon: goes to thalamus or cerebellum
Third order sensory neurons
Interneuron: Cell body: Thalamus (last neuron in sensory pathway) Axon: project to the primary somatosensory cortex
Upper motor neurons?
Pyramidal cells of primary motor cortex Cell body: Primary motor cortex Axons: Lateral corticospinal tract
Lower motor neurons?
Cell body: spinal cord Axons: target spinal nerves
Dorsal root only carries?
Somatic and visceral SENSORY information INTO spinal cord
Ventral root only carries?
Somatic and visceral MOTOR information OUT of spinal cord
Lateral spinothalmic tract
Ascending spinal cord tract that carries pain and temp info (sensory info!)
Lateral corticospinal tract
Descending spinal cord tract that carries motor impulses
- List the neurons in the sensory pathway, citing the locations of their cell bodies and axons.
First order neuron: Free dendritic receptors on peripheral process –> cell body in dorsal root ganglion –> Central process/axon,
Second order neuron –> cell body in the dorsal horn –> axon up the lateral spinothalmic tract
Third order sensory neuron: cell body in thalamus –>. Axon to primary somatosensory cortex
