Spinal Cord Flashcards
At the cervical thoracic border, what is the change in the vertebral level?
C1-C7 nerves exit superior to their vertebrae
C8 and T1-L5 nerves exit inferior to their vertebrae
The sacral cord ends at what level?
L2
What is the coccygeal ligament?
Dural sac terminates and gives rise to the ligament. It runs down the coccyx and attaches here
What does the dural sleeve cover? Why?
-cover spinal cord, roots, and the dorsal root ganglia due to their position with the intervetebral foramen
What do arachnoid trabeculae do?
They run from arachnoid to pia mater on the cord
What are denticulate ligaments?
-run from dura to pia/cord and help stabilize the spinal cord in the horizontal plane
The cord tapers down to _______________ at what level? Then after that it becomes what?
- tapers down to the conus medullaris at level L2
- cauda equina
What stabilizes the spinal cord in the vertical plane?
-filum terminale and coccygeal ligament outside of the dural sac
Where does the lumbar cistern begin?
L3
Is the subarachnoid space the same through every vertebral level?
Nope. They vary a lot!
What are the layers of the spinal cord in order from deep to superficial?
- spinal cord
- pia
- CSF
- arachnoid
- dural sheath
- epidural space
In the brain, the dura mater in directly attached to the skull. Is this different with the spinal cord?
- oh yea
- there is epidural space in the spinal cord filled with vessels and fat
What does the central canal do?
It runs the entire length of the cord and has a little bit of CSF since the cord developed from a fluid filled tube
What is primarily found in grey matter?
Primarily cell bodies! Neurons and glia
What is found in white matter?
- glia
- myelinated axons
Are there neuron cell bodies in white matter>
Nope
Why is there SOME stain for myelin in grey matter?
Neuron cell bodies have some myelin because some are myelinated and some are not.
In rostral-caudal order, where is there an enlargement of grey matter? Why?
- brachial plexus (C5-T1)
- Lumbar PLexus (L1-L4)
- Sacral Plexus (L4-S4)
-where you control extremities, you need more cells!
What is substantia gelatinosa?
-incoming sensory fibers carrying pain and temperature synapse
What is the lamina number where pain/temp fibers terminate and synapse?
II (2)
-in posterior/ dorsal horn
Which lamina are in the posterior/dorsal horn?
- Substantia gelatinosa (II)
- Crude(III and IV and V)
Which laminae are in intermediate grey matter?
- VII
- preganglionic sympathetic neurons
- intermediomedial cell column
Which laminae are in the anterior/ventral horn?
VIII, IX motor neurons
What laminae do crude touch fibers terminate and synapse?
III,IV,V
-in posterior/dorsal horn
Where are the preganglionic sym and para neurons located?
Intermediomedial cell column (intermediate grey space)
What are the 3 funiculi of the white matter?
- posterior
- lateral
- anterior
What is the posterior funiculus divided into?
- posterior median sulcus
- posterior median septum
- posterior intermediate sulcus
What is the anterior median fissure?
Basically the spinal cord version of a sulcus
What is the fasciculus cutaneous?
-part of the posterior funiculus that carries fine touch information for the arms and hands (T6 and above)
What is the fasciculus gracilis?
Sensory information from dorsal roots of T7 and below (legs)
What does the posterior/dorsal column system do?
-fine touch and conscious proprioception
What does the anteolateral system do?
Pain/temp/crude touch
-not spatially specific
Sensory information for the face comes from what?
Trigeminal
What are upper motor neurons?
- in precentral gyrus
- project down through the brain and spinal cord and synapse onto a lower motor neuron
What are lower motor neurons>
- in ventral/anterior horn
- send out information from upper motor neurons to the muscle
What is the ganglia that brings touch information into the cord?
The posterior root ganglion
Which kind of touch goes straight to the brain and which ones synapse in the dorsal horn and then to a tract?
- fine touch in posterior column system goes straight to the brain
- crude tough and temp in anterolateral system synapse in the cord then go to a tract
Loss of sensation in a dermatomal pattern signifies what?
-segmental pathology of the spinal cord, dorsal root or proximal spinal nerves at the same corresponding level.
Voluntary movement is controlled by what 2 consecutive neurons?
- upper motor neurons
- lower motor neurons
Motorneurons are ______________ cell body with what kind of dentrite?
- multipolar
- large dendritic arbor
Additional descending tracts onto motorneurons do what?
-modify lowermotor neurons to the upper motor neuron for motor coordination
When testing the corticospinal system, what are you testing?
Strength and reflex, not coordination!
What is the rating scale for corticospinal system?
5-normal and can overcome resistance
3-cant overcome resistance, but can overcome gravity
1-muscle contraction, but no movement
0-nothin
Describe the patellar reflex
- tap on tendon to stretch patellar tendon and create stretch sensation (mimics what happens when knee flexes)
- stretch sensation goes through dorsal root to the cord
- activates quad muscle to cause EXTENSION at the knee
- also inhibits FLEXION
-extend the knee and simultaneously inhibit the muscle that would flex
When testing stretch reflex, you are testing different ____________ regions of the spinal cord
Horizontal
The patella response is mediated at what level?
L4
What are some deep tendon reflexes?
- biceps
- triceps
- patellar
- ankle
For stretch reflex/deep tendon reflex, where is normal on the rating scale?
In the middle! 2/4
-clinical problems can be caused by too much and too little
What is clonus? Where is it on the reflex scale?
- when you flex, you get activation of extension muscles, but an alternating of activation of opposing flexion muscles, so you get a back and forth response
- it is a 4/4 on scale. (Normal is 3/4)
What muscles actually do the movement?
Extrafusal! Intramural are just sensory (inside the muscle spindle)
Sensory arc
Secnroy fibers from intrafusal. Stretch when muscle is stretched and act as mechanoreceptors and pick up the stretch to take to the spinal cord
Motor arc
Projections to extrafusal muscle (not to spindle) actually causes movement
Muscle spindles detect what?
- velocity(how fast or slow is the stretch)
- amplitude( how much the muscle is stretched)
What do gamma motor neurons do?
- innervate intrafusal muscles miners and cause them to contract when extrafusal muscles do even though they do not actually do movement
- it helps spindle maintain sensitivity to stretch
What is the influence of the descending projections to motor neurons on the stretch reflex?
- usually inhibitory
- disruption of the inhibitory regulation results in exaggerated reflexes
What is muscle tone?
The degree of resistance to passive stretch of a specific muscle
What are some major factors that influence muscle tone?
- over excitability of lower motorneurons
- hypersensitivity of lower motorneurons
- status of upper motor neurons to synapse on lower
What is nociceptive reflex?
- pain
- normal reflex happens with leg that experiences pain, but does opposite things to the other leg to make sure it stays stable
- useful for testing arousability and motor system of a patient with impairment of consciousness
What does the sympathetic NS do for urinary function?
Urinary storage
- inhibits detrusor
- activates external sphincter
What does the parasympathetic NS do for urinary function?
- activates detrusor
- inhibits external sphincter
Describe the short reflex voiding urine
-stretch receptor neurons (from bladder filling) activate parasympathetic neurons and stimulate detrusor
Describe the long reflex of voiding urine
- stretch receptor neurons activate brain stem centers and THEn activate parasympathetic neurons to stimulate detrusor
- also inhibits onuf nucleus motorneurons to relax external sphincter
What arteries supply the cervical region? Thoracic? Lumbar? Sacral?
- Cervical: vertebral arteries
- Thoracic: posterior intercostal arteries
- Lumbar arteries
- Sacral: Lateral/medial sacral arteries
Where is the median spinal vein located?
Inside of the dura
Where is the internal venous plexus?
-between the dura and the vertebrae
Where is the external venous plexus located?
-outside of the dura AND the vertebrae
