Nervous System III Flashcards
dura mater
outermost layer that is though and fibrous and continuous with dura of brain (through the foramen magnum) and ends at 2nd sacral vertebrae
What is the epidural space? What does it contain?
in between dura and spinal canal and contains C.T., fat, & veins
arachnoid
adherent to dura; continuous with arachnoid of brain
What is the space between the pia and the arachnoid called?
subarachnoid space
Where does the dura mater end?
2nd sacral vertebrae
Where does the arachnoid end?
S2
What is the space called which is used for access to cerebrospinal fluid (without damming the cord) during anesthesias? Where is it located?
lumbar cistern; it is located between L1-L2 and S2
Where does the pia end?
S2
What is the pia mater?
innermost meningeal layer that is adherent to the cord and is continuous with the pia of the brain
what are denticulate ligaments?
Small ligaments of the spinal cord that attach the spinal cord to the dural sac
what is contained in the epidural space of the spinal cord?
fat, connective tissue and blood vessels
how far does the dura/arachnoid sac extend?
from the foramen magnum to the 2nd sacral vertebrae
conus medullaris
where the spinal cord ends at L1 and L2
lumbar cistern (pool)
refers to the collection of CSF letween L2 and S2
cauda equina
(bundle of nerves) lumbar, sacral and coccygeal nerve roots that extend to exit the dural sac at a lower level
what are 2 main clinical uses of the lumbar cistern?
- sampling CSF for diagnostic purposes
2. administering anaesthetic
filum terminale
extension of pia from the conus medullaris that tethers the cord to the end of the dural sac
What are the 2 enlargements of the spinal cord?
- cervical (C4-T1)
2. lumbosacral (L2-S3) enlargement
cervical enlargement
C4-T1; site of innervation of arm; roots are short and horizontal
lumbosacral enlargement
L2-S3; site of innervation of leg; roots are long and vertical (forming the cauda equina)
dorsal horn
sensory: it processes and relays sensory information to the brain. Sensory info enters the cord via the dorsal root
dorsal root ganglion
cell bodies of sensory neurons
What root contains afferent fibres? What do these fibbers carry?
Dorsal root; carry sensory info (touch, temp, pain and proprioception)
what is contained in the ventral horn?
Large motor neurons that project to muscle (via ventral root)
motor efferents
motor neurone that project to muscle from the ventral root
What is found in the white matter of the spinal cord?
- nerve fibres
- neuroglia
3 blood vessels
why is white matter white?
high fat content (myelin)
the nerve fibres in the white matter arise from cell bodies located in what 3 places?
- brain: descending axons from cerebrum and brainstem
- spinal cord: Ascending axons from fray matter of spinal cord (dorsal horn)
- Periphery: ascending axons from dorsal root ganglion
Where on the spinal cord is there a maximum of sensory nerves?
the top of the spinal cord because sensory information travels up the cord to the brain. There are more sensory fibres added to sensory pathways as they ascend the cord.
What happens to the number of fibres in the white matter as you move down the cord? Why?
decreases;
what are the 2 ascending pathways ?
- sensory - touch, vibration, proprioception
2. sensory - pain & temp
descending pathway
motor - corticospinal innervation of motor neurone in ventral horn
what makes up the fray matter of the cord?
- neuronal cell bodies
2. neuroglia
dorsal horn of gray matter
receives sensory input via dorsal root. Site of numerous interneurons and projection neurons
ventral horn of gray matter
motor function; sends projections to skeletal muscle via ventral root
how many spinal nerves are there?
31
how many cervical spinal nerves are there?
8 pairs
how many thoracic spinal nerves are there?
12
how many lumbar spinal nerves are there?
5
how many sacral spinal nerves are there?
5
how many coccygeal spinal nerves are there?
1
Where do cervical nerves exit the vertebrae?
above; e.g. 5th cervical nerve is above the 5th cervical vertebrae; 8th cervical nerve is below 7th vertebrae
do spinal nerves always exit above the vertebrae?
no, below C7 vertebrae, the nerves exit below. Eg. T1 nerve is below the T1 vertebrae
name 2 tyoes of mechanoreceptors
- neuromuscular spindles
2. golgi tendon organs
neuromuscular spindles
receptors for stretch, respond to change in length ( basis for stretch reflex)
golgi tendon organ
stimulated by tension in tendons (protection against damage from excessive stretch)
3 times of sensory stimuli
- mechanical (mechanoreceptors)
- Pain (thermoreceptors)
- Temperature (thermoreceptors)
myotomes
motor innervation; refers to muscles innervated by the motor fibres of a spinal nerve
dermatomes
sensory information ; area of skin innervated by the sensory fibres of a spinal nerve
Where do the dorsal rami travel and innervate?
travel posteriorly around vertebral column to innervate muscles and skin of the back
ventral rami
travels anteriorly to innervate the muscles and skin of the anterolateral body wall
nerve plexus
formed by ventral rami of spinal nerves. A mixture of nerve fibres (from more than 1 spinal nerve) in the peripheral nerves
brachial plexus
C5-T1: motor and sensory innervation for shoulder and upper limb
cervical plexus
C1-C4: motor innervation of muscles of neck and diaphragm; sensory innervation of neck, diaphragm and adjacent peritoenum
lumbar plexus
T12-L4: motor for hip muscles, quads and sartorius muscles. Sensory innervation of lower ant abdomen, ventral thigh and knee
sacral plexus
L4/5 - S3: motor for pelvis, perineum, and most muscles of lower limb (not quads and sartorius). Sensory for perineum and most of lower limb
