Spinal Nerve and Back Anatomy Flashcards
Sensory/afferent
carries information from body INTO the CNS
General somatic afferent (GSA)
sensations from the body such as touch, pain, temperature, proprioception and kinesthesia (perception of position and movement of muscles and joints).
general visceral afferent (GVA) / autonomic
sensations that are not usually perceived but monitor basic body functions. may perceive sensations from organs in pain
special afferent (SA)
senses of light, smell, hearing, and equilibrium
Efferent / motor modality
neurons that carry information FROM the CNS to the body
General somatic efferent (GSE)
motor control of skeletal muscle
general visceral efferent (GVE) / Autonomic nervous system
motor control of smooth muscle and glands of the viscera, heart and blood vessels, etc
Nucleus
A collection of nerve cell bodies within the central nervous system
ganglion
collection of nerve bodies outside the central nervous system
Components of a spinal cord
The spinal cord have projections of dorsal (sensory) and ventral (motor) rootlets that go on to form their perspective roots.
- Cell bodies for dorsal nerves are located in the dorsal root ganglia (DRG).
- Cell bodies for ventral root motor fibers lie within the spinal cord
Ventral roots and dorsal roots eventually merge forming a spinal nerve.
Spinal nerves (mixed nerve) have dorsal ramus (mixed nerve) and central ramus (mixed nerve) projections.
somatic afferent neuronal pathway
Exteroceptive sensation and proprioceptive sensation
Ventral ramus serves the ventrolateral trunk and limbs
Dorsal ramus serves the posterior trunk
the pathway for both ventral and dorsal ramus input goes down the dorsal root, into the Dorsal root ganglion (DRG) then onwards to the dorsal horn of the spinal cord
somatic efferent neuronal pathway
pathway starts in cell body located in the ventral horn of the spinal cord.
pathway goes though ventral root into the spinal nerve where it can go through the ventral ramus (ventrolateral thunk and limbs) or dorsal ramus (posterior trunk)
Association neurons
reside in the spinal cord and interact with the afferent and efferent spinal nerve neuron.
neurons in ascending pathways transmit sensory information to higher CNS levels
neurons in descending pathways transmit somatic and visceral motor signals from higher levels to motor neurons forming spinal nerve
short interneurons mediate reflexes within the spinal cord
intervertebral disc
disc that allows the body of the vertebrae to bend against each other but prevents them from touching
zygapophysial joints
bind together the superior articular process and inferior articular process that allows the lumbar vertebrae to from a chain
vertebral ligaments
anterior and posterior longitudinal ligaments run the length of the column and are attached to the vertebral bodies and intervertebral discs
ligamentum flava connect adjacent laminae and fill the posterior side of the spinal canal
deep back muscle
- involved in powerful extension, lateral bending, and rotation of the back, neck and head
- innervated by the dorsal ramie spinal nerves
- erector spinal: more superficial large muscles
Meninges
surround the spinal cord in three layers, these layers also surround the brain
- dura: tough outer layer, reflected out along the spinal nerves and blends into the epineurium
- arachnoid: middle layer with weblike strands extending to the Pia
pia: thin transparent cover adherent to the cord
space between arachnoid and Pia is filled with cerebrospinal fluid that is made within the brain
intervertebral foramen
spinal nerves can exit spinal canal through these and and blood vessels can enter/leave spinal canal
Spinal vasculature
Anterior(single) and posterior (paired) spinal arteries run the length of the spinal cord.
In the trunk, these arteries are supplied by the anterior and posterior radicular arteries, which are both branched from the spinal branch. The spinal branch is connected to the intercostal and lumbar branches of the thoracic and abdominal aorta.
Artery of Adamkiewicz originates in the lower thoracic or upper lumbar region. it is much larger than the rest and is a critical supply for the lower spinal cord.
In the neck, branches of the vertebral arteries feed the anterior and posterior spinal arteries
cauda equina
Spinal cord ends at L1 vertebrae. Spinal nerves coming off the cord must continue to travel a distance down the spinal canal to reach their foramina and exit. the group of these nerves outside of the cord are called Cauda equina
spinal nerves and the caudal equina
a dural sac surround the caudal equina down to the S2 level of the sacrum
film terminale:
pial part: extends from the end of the conus medullar is to the end of the dural sac
dural part: extends from the dural sac to the coccyx. has a Pia sore and dural covering
Disc herniation
caused by the weakening of the annulus fibrosus, which leads to the bulging and herniation of part of the vertebral canal. This affects the spinal roots below the bulge. ex: occurs at L4/L5, L5 root will be most affected.
Nerve Plexuses
ventral rami merge and exchange fibers to form peripheral nerves consisting of neurons from multiple spinal levels.
cervical plexus: C1-C4
cutaneous and muscular nerves in the neck
brachial plexus: C5-T1
cutaneous and muscular nerves to the upper limb
Lumbar Plexus: L1-L4
Cutaneous and muscular nerves to the abdominal wall and lower limb
Sacral plexus: L4-S4
cutaneous and muscular nerves to the pelvis and lower limb
Cutaneous nerves:
Nerves going to the skin of the trunk, neck, and extremities will always contain:
- General Somatic Afferent (GSA) Fibers: conducting sensations of touch, pain, heat, and etc from the skin
- General Visceral Efferent (GVE) Fibers: controlling capillary beds, sweat glands, and arrector pili muscles
Musular Nerves
Nerves going to the skeletal muscles of the trunk, neck and extremities will always contain:
- general somatic efferent fibers: driving the contraction of the muscles
- general somatic afferent fibers: conducting proprioceptive information from the muscles and tendons, as well as pain sensation
- general visceral efferent fibers- controlling capillary beds in the muscles
Dermatomes
strip of skin innervated primarily by a single spinal nerve
key dermatomes:
- face: 3 divisions of cranial nerve V
- C1: NO dermatome segment
- C2: posterior skull
- C6,7 & 8: hand
- T4: region of nipple on thorax
- T10: region of umbilicus
- L1: inguinal region
- L4: Big toe
- S1: little toe
Clinical relevance of dermatomes
- useful in the diagnosis of nerve lesions with a cutaneous sensory deficit
- chicken pox can go dormant in DRGs after initial infection and then come back as shingles. it produces a painful rash on the dermatome of the spinal nerve that the chicken pox initially went dominate in.
Spinal reflexes
reflex arc is a simple neural pathway linking a receptor, the CNS and an effector
all reflex arcs have the following:
- a receptor that receives the stimulus
- a sensory (afferent) neuron that transmits the impulses away from the CNS to the effector
- an effector, a muscle, or gland that carries out the response
tendon stretch reflex
simplest type of reflex, requiring a chain of only two neurons.
reflex only involves one synapse (monosynaptic)
1) stretching stimulates sensory receptor (muscle spindle)
2) Sensory neuron excited
3) within integrating center (spinal cord), sensory neuron activates motor neuron
4) motor neuron is excited
5) effector (same muscle) contracts and relieves the stretching
withdrawal reflex
polysynaptic; requires the participation of the sensory, association, and motor neurons.
Think stepping on a nail. foot is flexed/withdrawn to prevent further stepping on it, muscle on leg on the opposite side of the body helps keep balance, signal goes to brain as well.
Electromyography
electrical activity in muscle is being tested in used muscle.
nerve conduction velocity testing
measures the speed of conduction of impulses through the nerve.
can be used to diagnose nerve damage or dysfunction. can differentiate injury to the nerve fiber (axon) from injury (amplitude) to the myelin sheath (velocity) surrounding the never
- Sensory nerve action potential (SNAP): nerve field is stimulated and signal is measured proximally to get amplitude and velocity
- Combines muscle action potential (CMAP): nerve is stimulated and action potential in the muscles is measured to get amplitude and latency in order to get nerve velocity
Somatosensory evoked potential (SEP or SSEP)
determine if sensory information is reaching the CNS
sensory nerves are stimulated and electrical activity in the spinal cord or sensory cortex of the brain is monitored by surface electrodes
H-reflex test:
helps distinguish between nerve and muscle disease and locales the site of nerve lesions
involves stimulating peripheral nerve afferents so that a reflex contraction of muscles results.
this is performing a stretch reflex, but bypasses the muscle spindles
diminished results show that there is a problem with efferent or afferent limb
F-wave analysis
helps distinguish between nerve and muscle disease and locales the site of nerve lesions
involves stimulating nerves at a higher intensity so that the signal travels proximally along the motor neurons and elicits a rebound efferent signal that stimulates the muscle
tests the motor neuron integrity- without involving the sensory neurons
in cases where the stretch reflex is abnormal, this can help determine if the problem is in the afferent or efferent limb of the reflex
Which parts of the vertebra would need tone removed to expose spinal cord and caudal equda?
Spinous process and lamina
List Meninge levels from superficial to deep
Epidural -> dura mater -> arachnoid -> subarachnoid -> pia -> spinal cord
relationship between the spinal cord and meninges
denticulate ligaments anchor the spinal cord to the dural sac
phenotypical differences in arteries and veins
- one artery w/ 2 or 3 veins surrounding it
- veins are larger, and have one-way valves
- arteries have thicker wall and are more tubular
muscle action categories
- agonist: muscle doing the action
- antagonist: not doing the action/ does opposite of action
- fixator: stabilizes action
- synergist: works along with agonist
Whiplash w/ hyperextension which ligament is most likely injured?
anterior longitudinal ligament
