Chapter 14- Spinal Cord and Spinal Nerves Flashcards
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
overall structure
- bilateral symmetry
- consists of both gray and white matter
central canal
hole down the center of cord; continuous with brain ventricles; both contain CSF
2 grooves of spinal cord
anterior median fissure
posterior median sulcus
enlargements
swollen regions of spinal chord
named based on region
-cervical enlargement
-lumbar enlargement
conus medullaris
inferior most tip of spinal cord; cone shaped
cauda equina
means horse’s tail; bundle of nerves inferior to spinal cord
filum terminale
inferior most spinal nerve
gray matter
- cell bodies, dendrites and synapses
- projections called horns
- cell bodies organized into nuclei
- -sensory
- -motor
interior horns
posterior horn
anterior gray horn
lateral gray horn
gray commissure
anterior commissure
posterior commissure
(separated by central canal)
white matter
tracts and columns
- posterior white column
- ant. white column
- lateral white column
- ascending tract=sensory
- descending tract=motor
meninges
membranes covering CNS
- are similar in both brain and spinal cord
- are split into layers called ‘mater’ (mother)
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
spinal meninges: dura mater
tough mother
- durable
- deep to epidural space
- superficial to subdural space
- stabilized by coccygeal ligament
spinal meninges: arachnoid mater
spidery mother
- superficial to suarachnoid space
- contains CSF
- CT looks like a spider web
spinal meninges: pia mater
delicate mother
- light layer adhering to cord
- forms part of filum terminale
spinal meninges order
vertebrae epidural space dura mater subdral space (with CSF) arachnoid layer subarachnoid space pia mater neural tissue
spinal nerves
31 pairs
- 8 cervical (with 7 cervical vertebrae)
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
nerve components
dorsal root -dorsal root ganglion -usually sensory ventral root -no ganglion usually motor
nerve components (cont)
roots merge to form nerves
- hence spinal nerves usually are mixed (sensory and motor)
- all roots go through intervertebral foramen
epineurium
surrounds the entire nerve
perineurium
surrounds bundles of 10-100 axons (known as fascicles)
endoneurium
surrounds each individual axon of each neuron
Rami
offshoots of a nerve once it exits the vertebrae
3 types of rami
dorsal ramus
ventral ramus
ramus communicantes
ramus communicantes
a splitting in the ramus separating sensory and motor fibers
white ramus communicantes
grey ramus communicantes
dermatomes
sensory innervation by specific spinal nerves
- spinal cord damage will result in loss of sensation in dermatome
- detection method
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
cervical plexus
C1-C4 and part of C5
-innervate certain muscles of neck and torso
phrenic nerve
C3, 4 and 5
goes to diaphragm
results in breath
-part of cervical plexus
brachial plexus
C4-C8 and T1
innervate the chest, upper back and arm
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
lumbosacral plexus
last thoracic, lumbar, sacral and coccygeal nerves
may be split into lumbar and sacral plexuses
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
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
classification of reflexes
- by development
- site of processing
- nature of motor response
- complexity of neural circuit
classification by development
genetically: built in (innate)
learned: acquired through repetition and/or experience
classification by site of processing
spinal reflex: impulse only goes to spinal cord
cranial reflex: makes it to the brain
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
classification by complexity of neural circuit
how many synapses are involved
- monosynaptic=1
- polysnaptic=2 or more
steps of a reflex arc
- receptor is stimulated by a detectible environmental stimulus
- receptor stimulates a sensory neuron that sends a signal to the CNS for processing
- 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
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
patellar reflex
patellar reflex is a stretch reflex
- functions to:
- prevent muscles form being overstretched
- prevent one from falling forward
