Exam 2 Lecture 1 Flashcards
What does the spinal cord connect?
Brain to the body and the body to the brain
What vertebrae does the spinal cord end at?
L1-L2
Where is the spinal cord located?
- Within the vertebral foramen (canal)
- Posterior to the vertebral bodies
Which nervous system is the spinal cord part of and what does this mean for regeneration?
Central Nervous System
-If injured, it CANNOT regenerate
What are the two “enlargements” of the spinal cord?
- Cervical region (contains the cervical plexus)
- Lumbar region (contains the lumbar plexus)
What is different in regards to the length of the spinal cord in young children vs adults?
- In young children, the spinal cord extends from C1 to nearly the bottom of the sacrum
- As the child grows, the vertebral column grows proportionally more than the spinal cord so the cord is “pulled up” to the adult position
Which direction does the spinal cord taper and what is this called?
- Tapers inferiorly
- Conus medullaris
What is the role of the Filum Terminale?
Anchors the spinal cord to the sacrum
What does a child with a “tethered cord” have?
Scar tissue preventing the spinal cord from moving superiorly
What are the four sections of the spinal cord?
- Cervical
- Thoracic
- Lumbar
- Sacral
How many spinal cord segments and vertebrae does the cervical region have?
- Spinal cord segments - 8
- Vertebrae - 7
How many total spinal cord segments are there and how many are in each region?
30 total
- Cervical = 8
- Thoracic = 12
- Lumbar = 5
- Sacral = 5
How many spinal nerves does each spinal cord segment have?
2 (R and L)
Where do spinal nerves exit in the cervical region?
SUPERIOR to the corresponding vertebrae
Where do spinal nerves exit in the thoracic, lumbar and sacral regions?
INFERIOR to the corresponding vertebrae
What is the cauda equina?
- Lumbar and sacral spinal nerve fibers within the vertebral canal, inferior to L2 form this
- Because the spinal cord ends at L2, lumbar and sacral spinal nerves must run inferiorly within the vertebral column before they can exit at their designated vertebrae
Where in the spinal cord is the grey matter located?
Internally
Where in the spinal cord is the white matter located?
Externally
What makes up the grey matter?
- Neuron cell bodies to and from peripheral structures (skin, muscles)
- “Butterfly”
What makes up the white matter?
-Nerves connecting body to/from brain
As you move inferiorly down the spinal cord, how do the amounts of grey and white matter change?
More grey matter as you move inferiorly, less white matter
-Sacral has the most grey matter, cervical has the least
What is grey matter divided into?
Horns
- Ventral/anterior horn
- Lateral horn
- Dorsal/posterior horn
What type of neurons does the anterior horn contain and what do they innervate?
Voluntary motor neurons (innervate skeletal muscle)
What type of neurons does the lateral horn contain and what do they innervate?
Autonomic motor neurons (innervate smooth and cardiac muscle)
T1-L2 and S2-S4 only
What type of neurons does the dorsal root ganglion contain and what do they innervate?
Sensory neurons (innervate skin, subQ tissue, etc)
Cross section of spinal cord labeled
Spinal nerves emerge from the cord as one of 2 roots:
- Anterior/ventral root: motor axons (voluntary motor neurons, T1-L2 or S3-S4 are autonomic motor neurons)
- Posterior/dorsal root: sensory axons
Where do dorsal and ventral roots join together and what do they form?
Join together as they penetrate the DURA MATER and they form SPINAL NERVES
Spinal nerves emerging from the spinal cord form _______
Plexuses
What are the three major plexuses?
- Cervical Plexus (C1-C4) - phrenic nerve (C2, 3, 4)
-
Brachial Plexus (C5-T1) - innervates UEs and skin
- Lumbosacral Plexus (L1-S5) - LEs, femoral and sciatic nerves
Axons in the white matter transmit action potentials in which direction?
Superiorly AND Inferiorly
What are found within each region of the white matter?
Tracts (bundles of axons) that are organized by their function
What is the white matter organized into?
Regions or columns (funiculus):
- Dorsal/posterior
- Lateral
- Ventral/anterior
Which direction does the descending tract in the white matter convey action potentials?
INFERIORLY
-Brain to body (move your foot)
Which direction does the ascending tract in the white matter relay action potentials?
SUPERIORLY
-Body to brain (step on something hot)
What is a dermatome?
Region of skin innervated by one spinal cord segment (one pair of spinal nerves)
What is a myotome?
Functional group of muscles innervated by a spinal cord segment (pair of spinal nerves)
What is a first order neuron?
- Part of peripheral nerves
- Receptor
- Afferent axon - can be myelinated or un-myelinated
What is a second order neuron?
- Starts in spinal cord, ends in brain
- Part of spinal cord white matter - ascending tracts
What is a third order neuron?
- Found in the brain, allows conscious perception of a stimulus
- Ends on the post central gyrus (primary somatosensory cortex)
