Lec 5 Flashcards
(32 cards)
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).
