Flashcards in Chapter 14- Spinal Cord and Spinal Nerves Deck (44)
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spinal cord: gross anatomy
-part of the CNS
size and location:
-slender nerve column
-about 45cm long
-starts at foramen magnum and ends between L1 and L2 (does not go into the sacrum)
-31 pairs of spinal nerves
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overall structure
-bilateral symmetry
-consists of both gray and white matter
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central canal
hole down the center of cord; continuous with brain ventricles; both contain CSF
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2 grooves of spinal cord
anterior median fissure
posterior median sulcus
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enlargements
swollen regions of spinal chord
named based on region
-cervical enlargement
-lumbar enlargement
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conus medullaris
inferior most tip of spinal cord; cone shaped
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cauda equina
means horse's tail; bundle of nerves inferior to spinal cord
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filum terminale
inferior most spinal nerve
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gray matter
-cell bodies, dendrites and synapses
-projections called horns
-cell bodies organized into nuclei
--sensory
--motor
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interior horns
posterior horn
anterior gray horn
lateral gray horn
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gray commissure
anterior commissure
posterior commissure
(separated by central canal)
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white matter
tracts and columns
-posterior white column
-ant. white column
-lateral white column
-ascending tract=sensory
-descending tract=motor
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meninges
membranes covering CNS
-are similar in both brain and spinal cord
-are split into layers called 'mater' (mother)
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superificial to meninges
vertebrae consists of vertebral arches
-epidural space
-space between meninges and vertebra
-contains BV and adipose
meninges connect to CT of spinal nerves
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spinal meninges: dura mater
tough mother
-durable
-deep to epidural space
-superficial to subdural space
-stabilized by coccygeal ligament
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spinal meninges: arachnoid mater
spidery mother
-superficial to suarachnoid space
-contains CSF
-CT looks like a spider web
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spinal meninges: pia mater
delicate mother
-light layer adhering to cord
-forms part of filum terminale
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spinal meninges order
vertebrae
epidural space
dura mater
subdral space (with CSF)
arachnoid layer
subarachnoid space
pia mater
neural tissue
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spinal nerves
31 pairs
-8 cervical (with 7 cervical vertebrae)
-12 thoracic
-5 lumbar
-5 sacral
-1 coccygeal
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nerve components
dorsal root
-dorsal root ganglion
-usually sensory
ventral root
-no ganglion
usually motor
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nerve components (cont)
roots merge to form nerves
-hence spinal nerves usually are mixed (sensory and motor)
-all roots go through intervertebral foramen
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epineurium
surrounds the entire nerve
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perineurium
surrounds bundles of 10-100 axons (known as fascicles)
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endoneurium
surrounds each individual axon of each neuron
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Rami
offshoots of a nerve once it exits the vertebrae
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3 types of rami
dorsal ramus
ventral ramus
ramus communicantes
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ramus communicantes
a splitting in the ramus separating sensory and motor fibers
white ramus communicantes
grey ramus communicantes
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dermatomes
sensory innervation by specific spinal nerves
-spinal cord damage will result in loss of sensation in dermatome
-detection method
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nerve plexus
braid off ventral rami
interconnected web of nerves for greater innervation
-found in several regions
-cervical
-lumbar
-sacral
(most thoracic nerves are all isolated
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cervical plexus
C1-C4 and part of C5
-innervate certain muscles of neck and torso
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phrenic nerve
C3, 4 and 5
goes to diaphragm
results in breath
-part of cervical plexus
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brachial plexus
C4-C8 and T1
innervate the chest, upper back and arm
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brachial plexus nerves
musculocutaneous
-to ant. muscles of arms and skin of forearm
ulnar nerve
-to muscles of forearm, hands and skin of hands
median nerve
-same as ulnar
-between radius and ulna
radial nerve
-to post. muscles of arms and skin of forearms and hands
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lumbosacral plexus
last thoracic, lumbar, sacral and coccygeal nerves
may be split into lumbar and sacral plexuses
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lumbosacral plexus nerves
innervate the lower limb regions
obturator nerve
-to adductors of leg
-femoral nerve
-motor impulses to leg and thigh and receive sensory from skin of leg and thigh
sciatic nerve
-to muscles and skin in thighs, legs and feet
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reflexes
-rapid automatic involuntary motor response to stimuli
-help preserve homeostasis
-occur at spinal cord or brain stem
-do not require cerebral processing
-can be modified by cerebral control
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classification of reflexes
-by development
-site of processing
-nature of motor response
-complexity of neural circuit
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classification by development
genetically: built in (innate)
learned: acquired through repetition and/or experience
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classification by site of processing
spinal reflex: impulse only goes to spinal cord
cranial reflex: makes it to the brain
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classification by nature of motor response
somatic: influences the skeletal muscles system
-purely effector based skeletal muscle in this case
visceral (autonomic): influences the involuntary systems such as smooth muscle and glands
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classification by complexity of neural circuit
how many synapses are involved
-monosynaptic=1
-polysnaptic=2 or more
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steps of a reflex arc
1. receptor is stimulated by a detectible environmental stimulus
2. receptor stimulates a sensory neuron that sends a signal to the CNS for processing
3. information is processed by being transmitted to the appropriate neurons
-this could be a n interneuron or motor neuron
4-5. motor neuron is stimulated, sending a signal to an effector. this results in a behavior
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stretch reflex
a reflex stimulated by the stretching of a muscle
-muscle spindle fibers are receptors that detect stretching
-effector is the contraction of the muscle
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