Lecture 33- Spinal Cord Flashcards
What are the two main functions of spinal cord?
provides a conduction pathway. Each column of white matter in the spinal cord contains bundles of axons (tracts).
Serves as an integration centre for spinal reflexes.
What does the spinal cord extend from?
Foramen magnum of skull
What prevents excessive movement of the spinal cord?
Fibrous extensions of the pia mater that anchor the spinal cord to the vertebral column and coccyx
How many nerve pairs does spinal cord have?
31
What divides the spinal cord into left and right halves?
Ventral (anterior) median fissure
Dorsal (posterior) median sulcus
Central canal
Cerebrospinal fluid filled canal that runs the length of spinal cord at its centre
What are Cervical and lumbar enlargements for?
the nerves that serve the limbs and a collection of nerve roots at the inferior end of the vertebral canal (cauda equina) that travel through the vertebral column to their intervertebral foramina
Where is Grey mater of the cord?
At the core
Where is white matter of the cord?
On the outside
What do dorsal horns of grey matter contain?
Interneurons
What to ventral horns of grey matter consist of?
Mostly cell bodies of somatic motor neurons
In thoracic and superior lumbar regions….
there are also paired lateral horns that extend laterally between the dorsal and ventral horns, and contain cell bodies of autonomic motor neurons.
Grey commissure
A bridge of grey matter that connects masses of grey matter on either side.
Ventral roots
exit the spinal cord carrying axons of motor neurons, and join with dorsal roots entering the spinal cord from peripheral receptors from outside of the spine to form spinal nerves.
Dorsal root ganglia are the cell bodies of sensory neurons.
What allows communication between the cord and brain?
White matter
Localized damage to the spinal cord or it’s roots leads to…
Paralysis (loss of motor function)
Paresthesias (loss of sensory function)
Severe damage to the ventral root or ventral horn results…
In flaccid paralysis
When upper motor neurons of primary motor cortex are damaged….
Spastic paralysis occurs
Voluntary control over skeletal muscle is lost
Damage to spinal cord occurs between….
T1 (first thoracic vertebra) and L1 (first lumbar vertebra)
Lower limbs affected
Paraplesia
Damage in cervical region, what is affected?
All four limbs
Quadriplegia
Spinal shock
Temporary loss of function caudal to the trauma
Neuronal pathways
Carry sensory and motor information to and from the brain
Function of Multineuron pathways
Cross from one side to the other (decussate)
Consist of a chain of two or three neurons
Exhibit somatotopy (a point-for-point relationship between an area of the body and a specific point in the central nervous system).
Conduction pathway examples
Lateral spinothalamic tract:
• is located in the lateral column of white matter.
• begins in spinal cord.
• ends in thalamus.
• is a sensory (ascending) tract.
Anterior (ventral) corticospinal tract:
• is located in the anterior column of white matter.
• begins in cerebral cortex.
• ends in spinal cord.
• is a motor (descending) tract.
Ascending pathways
conduct sensory impulses upward through a chain of three neurons.
Conduction pathway neurons
First-order neuron conducts the sensory info from the receptor to the spinal cord or brain stem.
Second-order neuron conducts the impulse to the thalamus.
Third-order neuron conducts the impulse to the primary somatosensory cortex of the cerebrum.
Nonspecific ascending pathways
receive input from many different types of sensory receptors, and make multiple synapses in the brain.
Specific ascending pathways
mediate precise input from a single type of sensory receptor.
Spinocerebellar tracts
convey information about muscle and tendon stretch to the cerebellum.
They are ipsilateral (don’t cross over) and only involve two neurons, not three.
Descending pathways involve…
two neurons:
upper motor neurons
lower motor neurons that innervate skeletal muscle.
Direct/pyramidal system
upper motor neurons from the cerebral cortex regulates fast, finely controlled or skilled movements.
Indirect/extrapyramidal system
upper motor neurons from the brainstem regulate muscles for balance and coarse movements
Naming conduction pathways
Location, from, to
