Nervous System II: Spinal Cord Flashcards
spinal cord nervous system general location
-in vertebral column enclosed by vertebrae in vertebral canal
spinal cord nervous system location extent
-foramen magnum of the medulla to intervertebral disc between L1 and L2
spinal cord nervous system components
- conus medullaris
- cauda equina
- filum terminale
- cervical and lumbar enlargements
- spinal nerves
conus medullaris
- aka “horse tail”
- composed of nerve roots
- extends from the distal end of the spinal cord
filum terminale
- a long filament of CT
- extends inferiorly from the conus medullaris (extension of pia mater)
- functions to anchor the spinal cord to coccyx (so it doesn’t shift
cervical and lumbar enlargements
- thickened regions
- contains neurons that control the skeletal muscle of the upper and lower limbs
spinal nerves
-arranged in plexi originate from these enlargements
31 pairs of spinal nerves
-exit the spinal cord thrugh the intervertebral foramina in the cervical, thoracic, lumbar, and sacral regions
meninges composition
-three layers of CT which cover and protect the Brain and spinal cord
meninges components
- dura mater
- arachnoid
- pia mater
dura mater
- outermost layer
- tough as parchment
arachnoid mater
- very thin middle layer
- like cellophane
pia mater
- CT covering
- touches spinal cord and brain
spaces within the meninges
- subarachnoid space
- epidural space
- subdural space
subarachnoid space location
- deep to arachnoid
- between arachnoid and pia mater
- brain and spinal cord
subarachnoid space composition
-cerebrospinal fluid (CSF)
cerebrospinal fluid
-ultra filtrate of plasma produced in ventricles of the brain
characteristics of cerebrospinal fluid
- clear/colorless/odorless
- serves to cushion and nourish the brain and spinal cord
cerebrospinal fluid production location
- choroid plexus in the ventricles of the brain
- circulates in the subarachnoid space
choroid plexus in the brain
-specialized capillaries that produces CSF
epidural space
- located in external to dura mater
- contains fat and blood vessels which supply the spinal cord
subdural space
- deep to the dura mater
- normally nothing is found in this space
- arachnoid is pressed against dura)
when would something be in the subdural space?
-during injury, it may fill will blood (aka subdural hemorrhage)
what happens during meningitis?
-inflammation of the meninges
what could inflammation also mean?
-infection
how can you diagnose meningitis?
- spinal tap
- lumbar puincture
at what vertebral level can you put a needle to test for meningitis safely without damaging the spinal cord? and why?
- between L4 and L5
- it’s safe because the spinal cord ends at L1-L2
what anatomical landmark could you use to help locate the vertebral level when testing for meningitis?
- palpate the iliac crests
- a line drawn from one crest to the other passes through the junction of vertebrae L4 and L5
list in order the structures the needle to test for meningitis would have to pierce to reach the subarachnoid space
- skin
- subcutaneous tissue
- interspinous ligaments (CT)
- epidural space
- dura mater
- arachnoid space
- subarachnoid space
when inserting the needle to test for meningitis, what areas do you not want to pierce?
- pia mater
- spinal cord
how many segments is the spinal cord divided into?
-31 segments
what are the names of the spinal segment regions?
- cervical
- thoracic
- lumbar
- sacral
- coccygeal
how many segments are within each spinal segment region?
- C: 8
- T: 12
- L: 5
- S: 5
- C: 1
white matter
- fiber bundles(tracts) of myelinated axons
- often arranged in columns of fasciculi
what causes the white color in myelin?
-due to myelin (made of lipid)
gray matter
-contains cell bodies of neurons located in horns
where are gray matter horns?
- regions that are H-shaped
- central portion of the spinal cord
ventral grey horn
-contain cell bodies of motor neurons
dorsal root
- extends laterally from spinal cord
- contains sensory nerve fibers
- collection of cell bodies outside of nervous system
dorsal root ganglion
- attached to dorsal root
- contains cell bodies of sensory neurons
ventral root
- extends laterally from spinal cord
- contains motor nerve fibers
what is located at each spinal cord segment?
-a pair of spinal nerves
what are the components of a spinal nerve?
-motor and sensory fibers
what do spinal nerves pass through?
-intervertebral foramen
what are spinal reflexes?
- rapid, unconscious automatic response to a stimulus
- protect areas of the body from injury (i.e. overstretching s muscle/tendon)
what part of the body does a spinal reflex not involve?
-the brain
reflex arc
- a conduction pathway
- includes multiple components
components and location of a stretch reflex
- receptor in muscle spindle (aka tendon)
- sensory neuron in dorsal root ganglion
- motor neuron in ventral gray horn of spinal cord
- effector in the skeletal muscle
spinal reflex receptor function
- responds to stimulus
- initiates impulse
spinal reflex sensory neuron function
-transmits impulse to CNS (spinal cord)
spinal reflex motor neuron function
-transmits impulse from CNS to PNS (spinal nerve)
spinal reflex effector function
-muscle that impulses responds to motor neuron impulse
how many synapses are necessary in a stretch reflex arc?
-one
how does a withdrawal reflex differ from a stretch reflex?
-withdrawal reflex includes a interneuron
where is the receptor for a withdrawal reflex located?
-in the skin
where does an interneuron transmit information to?
-the sensory neuron to the motor neuron
what is an interneuron also called?
-associative
how many synapses are necessary in a withdrawal reflex arc?
-two
