Spinal Cord Flashcards
Which part of the spinal cord is made of grey matter?
The middle (that looks like an X)
Which part of the spinal cord is made of white matter?
The outside
What are the four levels of spinal cord?
• Cervical
• Thoracic
• Lumbar
• Sacral
Which part of the spinal grey matter does information come into?
Dorsal horn
Which part of the spinal grey matter does information leave from?
Ventral grey matter
Where are motor neurones located in the spinal cord?
Ventral spinal cord
What does somatotopic mean?
That space is related to locations on the body such that adjacent neurones in the neural tissue respond selectively to stimuli presented to adjacent locations in the body (i.e. further in spine, further in body)
What are the two major descending systems of spinal white matter?
• Lateral descending system
• Medial descending system
What are the two major ascending systems?
• Dorsal column pathway
• Spinothalamic pathway
What are the two tracts that make up the lateral descending system?
• Corticospinal (from cortex)
• Rubrospinal (from red nucleus)
What are the two tracts that make up the medial descending system?
• Vestibulospinal (from vestibular nuclei)
• Reticulospinal (from reticular nuclei)
Describe the structure of the lateral descending system
• Fibres of the lateral system are in the dorso-lateral part of the spinal cord
• They connect to motor neurones in the lateral part of the ventral horn
What are the functions of the lateral descending system?
• Corticospinal fibres control movement of every part of the body and is very important for individual finger use
• Other descending fibres, primarily the rubrospinal tract, can compensate partially for the loss of descending corticospinal input
Describe the structure of the medial descending system
• Fibres of the medial system are in the ventro-medial part of the white matter
• They connect to motor neurones in the medial part of the ventral horn
What are the functions of the medial descending system?
• Control of balance and posture
• Vestibulospinal tract retains balance when the body is moved (external disturbance)
• Reticulospinal tract helps us retain posture and balance during our own volitional movements (internal disturbance)
What does the dorsal column pathway do?
Carries sensory information from the joint and skin about:
• Fine touch
• Vibration
• Two-point discrimination
• Proprioception from the skin and joints
What does the lateral spinothalamic tract do?
Conveys:
• Crude touch (a sense of being touched without knowledge of where)
• Pain
• Temperature
What does DRG stand for and what are they?
• Dorsal root ganglion
• Cell bodies of incoming sensory neurones which sit outside the spine
How many pairs of spinal nerves are there?
31
What is a dermatome?
An area of the skin supplied by nerves from a single spinal root
What is two-point discrimination?
The ability to discern that two nearby objects are touching the skin
Why are there spinal enlargements?
The arms and legs have many highly innervates muscles and a high density of sensory receptors so need more nerves
What are the two types of tetanic contractions?
Unfused and fused
What is the size principle?
With increasing strength of input onto motor neurones, smaller motor neurones are recruited first and fire action potentials before larger motor neurones are recruited
