Spinal Cord

Question 1

Describe how sensory information enters the spinal cord and the structures involved

Answer 1

1)Sensory info (from skin ex.) enters through the spinal nerve 2) Runs along dorsal root : a. Cell body is in the dorsal root ganglion 3) Once in the spinal cord, the info gets transferred up into the brain (this fiber will then cross over in the brainstem and go to the thalamus on the opposite side) 4) Eventually, the spinal motor neuron located in the ventral horn receives instructions 5) The neuron in the ventral horn has its own neuron that moves the info out through the ventral root and it joins the spinal nerve and goes out to a muscle fiber to instruct it to “contract” etc. *Remember: Dorsal side is for sensory (dorsal=detection). The ventral root (or anterior root) is for motor actions.

Question 2

Describe how motor info leaves the spinal cord and the structures involved

Answer 2

Motor is leaving the spinal cord and going out to the periphery. 2) Upper motor neuron on the opposite side of the brain, its axon crosses in the brainstem and descends in the spinal cord 3) Spinal motor neuron in the ventral horn recieves instructions 4) Neuron has its axon that runs along the ventral root, joins the spinal nerve again with the sensory fibers. 5) Continues out to the periphery where it goes to talk to a muscle fiber and cause it to contract(dorsal side is for sensory, think dorsal detection, the ventral root or anterior root is motor action)

Question 3

Define a reflex arc, listing steps and the CNS structures involved

Answer 3

2 components: a) afferent limb- Sensory- CNS- carries the info INTO the CNS b) Efferent limb- Motor- effector organ (ie. skeletal m)-carries info OUT towards effector organ
* Reflexes involve direct connection btn sensory fibers and spinal motor neurons. a reflex is an immediate, involuntary motor response to a specific sensory stimulus