L14-CH13 Spinal cord

CNS consists of

spinal cord and brain

spinal cord

integrates and processes info, functions with the brain but can also functions independently of the brain

the brain

integrates and processes info, can function with spinal cord and also independently

what are features of the spinal cord

cervical enlargement, lumbosacral enlargement, conus medullaris, filum terminale(becomes part of coccygeal ligament), cauda equina, posterior median sulcus, anterior median fissure

what are the main features of the spinal cord

31 spinal segments, each segment consists of - dorsal roots, dorsal root ganglia, ventral root and spinal nerve (mixed nerves of afferent and efferent)

spinal meninges

specialized membranes that provide protection, physical stability, and shock absorption

continuous with the cranial meninges

made of three layers: dura mater, arachnoid mater and pia mater

dura mater

tough, fibrous outermost layer

stabilizes the spinal cord within the vertebral canal

cranial and sacral attachments stabilize longitudinal axis of spinal cord

epidural space

space between the dura mater and lining of vertebral bones

coccygeal ligament

dura mater blends with the filum terminale, thus forming the coccygeal ligament

arachnoid mater

middle layer

separated from pia mater by subarachnoid space

cerebrospinal fluid flows within this space

arachnoid trabeculae extend from arachnoid to outer layer of pia mater

subdural space

space between dura mater and arachnois found in cadavers but not living people

pia mater

innermost layer- adj to spinal tissue or brain tissue

blood vessels are found here

firmly bound to the brain tissue and spinal tissue

denticulate ligaments

extensions of pia mater attach the pia and arachnoid to dura mater

gray matter

surrounds central canal and is called horns based on its shape

consists of somas and glial cells

white matter

consists of axons (myelinated and unmyelinated) organized into tracts or columns

located outside the gray matter area

soma organization

organized into groups called nuclei

includes sensory nuclei and motor nuclei

posterior (dorsal) horns

somatic sensory and visceral nuclei

lateral horns (intermediate horns)

visceral motor nuclei

anterior (ventral) horns

somatic motor nuclei

organization of gray matter in spinal cord

posterior horn, lateral horn, anterior horn, and gray commissure

organization of white matter

posterior white column, anterior white column, lateral white column, and anterior white commisure

what are columns in white matter

funiculi are columns of axons, columns contain tracts of axons

they convey sensory tracts - ascending tracts —-OR——- motor tracts- descending

how many spinal nerves are there

31 pairs of spinal nerves

what is the breakdown of each region of spinal nerves

8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal nerve

what does each peripheral nerve consist of

epineurium, perineurium and endoneurium

epineurium

outer layer- becomes continuous with the dura mater

perineurium

layer surrounding a fascicle (fasciculus)- bundle of axons

endoneurium

layer surrounding a single axon

spinal nerve branches

dorsal ramus and ventral ramus

what does T1 to L2 have

additional branches white ramus and gray ramus

rami communicantes

white and gray rami collectively called this

both of these are associated with the autonomic ganglion of symp ANS

dermatomes

spinal nerves supply specific regions of the skin called this

what are the four nerve plexus

cervical plexus, brachial plexus, lumbar plexus and sacral plexus

nerve plexus

each one is associated with an interwoven network of nerves

lumbosacral plexus

sometimes the lumbar plexus and sacral plexus are combined

cervical plexus

composed of ventral rami of C1-C4

consists of cutaneous and muscular branches

cutaneous branch innervates head, neck and chest

cutaneous and muscular branches of cervical plexus

lesser occipital nerve, supraclavicular nerve, great auricular nerve, transverse cervical nerve, ansa cervicalis nerve, and phrenic nerve

what do the cervical plexus nerves innervate

rhomboids and serratus anterior

organization of brachial plexus

ventral rami (roots)

trunks (superior, middle and inferior)

anterior and posterior divisions

posterior, lateral and medial cords

nerves

what does the brachial plexus form

radial, ulnar, median and musculocutaneous nerve

lumbar plexus nerves

iliohypograstic nerve, ilio-inguinal nerve, lateral femoral cutaneous nerve, genitofemoral nerve, femoral nerve, and obturator nerve

sacral plexus nerves

superior gluteal nerve, inferior gluteal nerve, sciatic nerve, posterior femoral cutaneous nerve, and pudendal nerve

reflex

immediate involuntary motor response

reflex arc

neural wiring of a single reflex

begins at sensory receptor and ends at a peripheral effector

pathway of a reflex arc

activation of a sensory receptor

relay of info to CNS

info processing

activation of motor neuron

response by effector

how are reflexes classified

innate or acquired development

somatic or visceral motor response (autonomic)

monosynaptic or polysynaptic neural circuit

spinal or cranial processing

monosynaptic reflex

involves a single segment of the spinal cord

polysynaptic

integrates motor output from several spinal segments

stretch reflex

stimulus stretches muscle

activates a sensory nerve

info is processes in spinal cord

motor neurons are activated

muscle (effector) contracts