Chapter 13 Part 1 Flashcards
Ventral Root
Contains efferent axons, including axons that innervate skeletal muscle.
Dorsal Root
Contains sensory axons that connect with a single segment of the spinal cord.
Spinal Nerve
Contains all of the motor, sensory, and autonomic axons of a single spinal segment.
Dorsal root ganglion
Contains cell bodies of primary sensory neurons.
Tract cell
Neuron with a long axon that conveys information from the spinal cord to the brain.
Propriospinal neuron
Neuron that begins and ends within the spinal cord.
Doral ramus
Innervates paravertebral muscles, posterior vertebral structures, and overlying cutaneous areas.
What is a significant feature of the spinal cord?
segmental organization
How is each segment of the cord connected to a specific region of the body?
by axons traveling through a pair of spinal nerves.
Where are spinal nerve found in the cervical region?
above the corresponding vertebrae, except the eighth spinal nerve
Where do spinal nerves lie in the remainder of the cord?
below the corresponding vertebrae
What does white matter surround?
gray matter
What does what matter do?
contains axons that link the cord with the brain
How is gray matter classified?
10 histologic regions, called Rexed’s laminae
What do Laminae I and II do?
process information about pain
What does the dorsal horn do?
processes sensory information
What does the lateral horn do?
processes autonomic information, and present at T1-L2 segments
What does the ventral horn do?
processes motor information
What are meninges?
layers of connective tissue that surround the spinal cord, and
are continuous with the meninges surrounding the brain
What is pia matter?
closely adheres to the spinal cord surface
What is arachnoid?
separated from the pia by cerebrospinal fluid in the subarachnoid space
What is dura?
tough, outer laye
What is the function of the spinal cord?
exchange information with brain and peripheral nerve structures and other segments
What do interneuronal circuits do?
integrate the activity from all sources and adjust output of lower motor neurons
What do interneurons do?
coordinate activity in all the muscles when a limb moves
What are stepping pattern generators?
Are adaptable neural networks that produce rhythmic output
How do stepping pattern generators work?
Contribute to stepping by activating LMNs, eliciting alternating flexion and extension at the hips and knees
How are stepping pattern generators activated?
when the person voluntarily sends signals from the brain to the CPGs in the spinal cord to initiate walking
Rexed lamina I (marginal zone)
Project neurons that receive input form small diameter afferents; once source of anteriolateral system projections
Rexed lamina II (substantia gelatinosa)
interneurons that receive input mainly from small diameter afferents; integrates feedforward and feeback inputs that modulate pain transmission
Rexed lamina III/IV (nucleus proprius)
interneurons that integrate inputs from small and large diameter afferents
Rexed lamina V/VI (base of dorsal horn)
projection neurons that receive input from both large and small diameter affterents and spinal interneurons; another source of anterolateral system projections
Rexed lamina VII (intermediate gray)
interneurons that communicate between dorsal and ventral horns; includes dorsal nucleus of Clarke
Rexed lamina VIII (motor interneurons)
interneurons in the medial aspect of ventral horn that coordinate the activities of lower motor neurons
Rexed lamina IX (motor neuron columns)
columns of lower motor neurons that govern limb musculature
Rezed lamina X (central gray)
interneurons surrounding the rudiment of the central cord
What do interneurons in inhibited circuits do?
contribute to spinal cord motor coordination
What do inhibitory interneurons provide:
Reciprocal inhibition
Recurrent inhibition
What does reciprocal inhibition do?
Decreases activity in antagonist when an agonist is active, allowing the agonist to act unoppose
separates muscles into agonists and antagonists
What is recurrent inhibition?
Effects opposite to reciprocal inhibition: inhibition of agonists and synergists, disinhibition of antagonists
What are Renshaw cells?
interneurons that produce recurrent inhibition
How are Renshaw cells stimulated?
by a recurrent collateral branch from the alpha motor neuron
