Lec 5 Flashcards
How many spinal segments are there in total?
How many in each:
Cervical -
Thoracic -
Lumbar -
Sacral -
Coccygeal -
31 total
Cervical - 8
Thoracic - 12
Lumbar - 5
Sacral - 5
Coccygeal - 1
What holds the spinal cord in place? and where attach?
(Name 3)
Meningeal layers
Denticulate ligaments - attach to outer layer (meningeal layer of dura in spinal cord because there is no periosteal layer)
Filum terminale - connects to end of coccyx to hold in place
What vertebra does the spinal cord end at?
L1-L2 vert. Then nerve roots (cauda equina) and filum terminale extend down.
What is the significance of Rexed’s IXth lamina
It has somatotopic organization and houses most of the motor neurons.
What is a myotome
A myotome is a group of muscles innervated by the motor neurons of a single spinal nerve root.
(must confirm)
How does myotome differ to muscle unit, and motor unit
Muscle unit - one motor neuron and all the muscle fibres it innervates within A SINGLE MUSCLE.
Motor unit - a single motor neuron and all the muscle fibres it innervates (can be across multiple muscles).
Myotome is a spinal segment and all the muscles innervated by that segment. (must confirm)
Do cervical nerve roots exit above or below the associated vertebrae?
How many are there?
Exit above
The 8th cervical nerve root exits below C7 and above T1
How many vertebrae are there/how many of each type?
There are 33 total
Cervical - 7
Thoracic - 12
Lumbar - 5
Sacrum - 5
Coccyx - 4 (fused)
Do thoracic nerve roots exit above or below the associated vertebrae?
Below
(because there are 8 cervical segments but only 7 vertebrae)
Do lumbar spinal roots exit above or below the associated vertebrae?
Below
Do sacral spinal roots exit above or below the associated vertebrae?
Below (I suppose, cause they’re all fused)
What does each spinal segment correspond to, the nerve or the vertebrae?
Corresponds to the nerve
For instance the Upper lumbar segments actually lie closer to the lower thoracic vertebrae, but extend down and exit at their associated vertebrae.
Where does the spinal cord end (at what level of vertebrae does the conus lie?)
At about L1-L2 vert
What are the two enlarged areas of the spinal cord called?
Why enlarged?
Cervical enlargement
Lumbosacral enlargement
This is because there are a lot more motor nuclei for the limbs at these levels.
Diff between Motor nuclei, Motor neurons , Motor nerves
Motor nuclei are the “headquarters.” (clusters of motor neurons)
Motor neurons are the individual “messengers.”
Motor nerves - bundle of axons
Where will you find more white matter in the spinal cord (top or bottom)? Why?
Near the top because white matter means more myelination which is better for sending signals.
Near the top of the spinal cord, signals will need to be sent lower, whereas near the bottom, nerves are exiting and not much else has to be sent further down.
Difference between spinal segment and nerve root
A spinal segments is the area of the spinal cord where one nerve root originates
What do the cervical nerves control (in descending order)
cervical - Hon don’t dabble with … H&N, D, D&B, W, T, H
Head and neck
Diaphragm
Deltoids and biceps
Wrist extensors
Triceps
Hands
What do the thoracic nerves control (in descending order)
Thoracic - Chest + abdominal muscles
What do the lumbar nerves control (in descending order)
Leg muscles
What do the sacral nerves control (in descending order)
B, B, S
Bowel, bladder, sexual function
Describe what the C5, C6, C7 nerves innervate
C5 = Deltoids
C5-C6 = Elbow flexors
C6 = Wrist extensors
C7 = Elbow extensors + tricep reflex
Describe what the L4, L5, S1 nerves innervate
L4 = Knee extensors + patellar tendon reflex
L5 = Ankle dorsi flexors (e.g. tibialis anterior)
S1 Ankle plantar flexors + achilles tendon reflex
Difference between lower and upper motor neurons
Lower - Last synapse to muscle. Can be high or low in spinal cord.
Upper - connect brain (cortex) to final reflex arc, can also be throughout the spinal cord but doesn’t directly touch muscle (synapse to lower motor neurons).
What are the symptoms of lower motor neuron injuries (5)
- Muscle weakness
- Fasciculations - continuous and involuntary muscle twitches as a result of lack of stimulus to nerve leading to hyper sensitivity.
- Atrophy
- decreased reflexes/hyporeflexia (monosynaptic reflex arc)
- Tone decrease -
what is muscle tone. What do?
Continuous/passive contraction of muscles even at rest.
Keeps muscles responsive. Involves a balance of IPSP’s and EPSP’s.
Describe the types of muscle weakness (the common terms) (4)
Distinguish between Hemi, para, mono, di, and quadra/tetra
Paresis - weakness/partial paralysis
Plegia - No movement
Paralysis - No movement
Palsy - weakness or no movement
Hemi = one side (e.g. one side of face)
Para = both legs usually
Mono = one limb
Di = both sides of body effected
Quadri/tetra = all four limbs
combine terms to get e.g. quadraplegia (no movement in all four limbs)
Describe the muscle strength scale
The muscle strength scale is from 0-5
0 = no movement
1 = slight contraction but no movement
2 = movement possible without gravity
3 = movement with gravity (against gravity)
4 = movement with some resistance possible
5 = movement with full resistance possible
Must test both sides
Define fasciculations
uncontrollable muscle twitches caused by hypersensitivity.
the synapses for nerve become hypersensitive waiting for stimulation (but can’t get from presynaptic neuron because of damage) they get stimulated by metabolites of nearby muscles/nerves.
Indicative of lower motor neuron injury
Name two reasons for muscle atrophy with nerve damage.
- inactivity
- Decreased trophic influences like growth factor (ask in office hours!!)
Describe the tendon reflex scale
scale from 0-5
0 = no reflex
1 = present but decreased
2 = normal
3 = brisk and excessive
4 = Hyper-reflexia - non-sustained clonus (a couple muscle twitches)
5 = Hyper-reflexia - sustained clonus (muscle twitches don’t stop immediately)
How do you test for tone
move patient through ranges of motion and feel for resistance.
Increased = hyper-reflexia (increased tone)
Decreased resistance = hypo-reflexia (decreased tone)
