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Block 1 lecture 2

Neuron cells

responsible for reception, integration, and transmission of nerve impulses

Neuroglial cells (glial cells)

responsible for supporting and protection neurons (myelination)

Parts of a neuron

cell body central part of cell where nucleus and most organelles are located
dendrites: usually multiple and short cell processes that carry impulses towards cell body
axon: single process (long) that carries impulses away from cell body

What is considered the central nervous cystem

brain and spinal cord

What is considered the peripheral nervous system

spinal nerves, cranial nerves, and associated ganglia

What are ganglia

collection of neuronal cell bodies in PNS

What does the somatic nervous system control

skeletal muscle

What does the autonomic nervous system control

smooth muscle, cardiac muscle, and glands

Cervical spinal nerve naming

named according to vertebra below nerve (besides C8, C8 exits between C7 and T1) (C8 acts more like cervical than thoracic)
i.e. c5 exits vertebral canal b/w c4 and c5

Thoracic nerve down naming

spinal nerves are named according to vertebra located above nerve
i.e. t6 s.n.n exits vertebral canal b/w t6 and t7

Spinal nerve formation

formed by ventral root and dorsal root
once roots meet the spine becomes a mixed nerve (having both motor and sensory fibers)

Dorsal root ganglion (posterior root ganglion)

swelling in the dorsal root that contains cell bodies of sensory neurons
pseudounipolar neurons - these are in the ganglion which give rise to one single process that divides into a dendrite and axon

Spinal nerves divide into 3 branches as they exit vertebral canal. What are they?

Dorsal ramus, ventral ramus, and meningeal branch
(all mixed nerves)

Dorsal ramus info

supplies sensory for skin of back and motor for deep back muscles
usually divides into medial and lateral branches

Ventral ramus info

usually the largest
supllies skin and muscles of limbs, skin and muscles of anterolateral trunk, skin and muscles of anterolateral neck, and superficial and intermediate back muscles

Meningeal branch info

these go back into vertebral canal and supplies meninges, blood vessels, ligaments, periosteum, and intervertebral discs

Do ventral rami of thoracic spinal nerves share fibers? If so, what do they form? What nerves do they constitute

no (except for T1) all others have a segmental distribution and do not share fibers above or below
constitute 2nd to 11th intercostal nerves and subcostal nerve

Cervical plexus nerves and what they supply

Formed by ventral rami of C1 to C4. supplies neck

Brachial plexus nerves and what they supply

Formed by ventral rami of C5-T1. Supplies upper limb

Lumbar plexus nerves and what they supply

Formed by ventral rami of L1-L4. Supplies anterior abdominal wall and lower limb

Sacral plexus nerves and what they supply

Formed by ventral rami of L4-S4. Supplies lower limb and perineum

Multisegmental peripheral nerves

most peripheral nerves that originate from plexuses contain fibers from ventral rami of more than one spinal nerve.
conversely, ventral rami of spinal nerves participating in plexuses contribute fibers to multiple peripheral nerves

What is a dermatome

area of skin innervated by sensory fibers of a spinal nerve

Peripheral cutaneous nerve info

Sensory fibers from a single spinal nerve usually reach skin in more than one peripheral cutaneous nerve
They usually contain sensory fibers from more than one spinal nerve

Spinal cord beginning and end

superiorly at foramen magnum, where it is continuous with medulla oblongata
ends inferiorly at L1/L2 intervertebral disc (adult)

Cervical enlargement location and what it gives rise to

extends approx. from C5 to T1 spinal cord segments (not vertebrae)
gives rise to brachial plexus (nerves that supply upper limb)

Lumbosacral enlargement location and what it gives rise to

extends approx. from L1 to S3 spinal cord segments (not vertebrae)
gives rise to lumbar and sacral plexuses (nerves that supply lower limb perineum)

Conus medullars

inferior to lumbosacral enlargement
tapering of spinal cord (where it ends)
looks like a cone

Filum terminale location and derivation

derived from pia matter and attaches from conus medullaris to coccyx

Spinal cord development embryo (up to 8th week)

spinal cord extends entire length of vertebral canal
Spinal cord segments correspond to the same vertebrae
short distance between origin of a spinal nerve and corresponding intervertebral foramen

Spinal cord development after 8th week embryo development

different growth rate of spinal cord and vertebral column causes spinal nerve roots to elongate
spinal cord levels do not correspond with vertebral levels

What is cauda equina

nerve roots that are inferior to conus medullaris

Where is the Anterior median fissure and what occupies it?

deep groove along anterior midline of spinal cord
occupied by anterior spinal artery

Where is the posterior median sulcus

shallow groove along posterior midline

Where are Anterolateral and posterolateral sulci

correspond with attachment of ventral and dorsal rootlets of spinal nerves

Where is the posterior intermediate sulcus and what regions is it present

located between posterior median and posterolateral sulci
present in cervical and above T6 thoracic regions (spinal cord segment not vertebrae)

What is the internal structure of the spinal cord

narrow cavity is the central canal which is continuous superiorly with 4th ventricle of brain
gray matter is internal
white matter is external

What is located in the gray matter and what are its regions

contain cell bodies of neurons and dendrites
regions are dorsal horn, ventral horn, intermediate zone, and lateral horn in thoracic and upper lumbar segments

White matter regions and what it contains

contains axons most with myelination
in all spinal cord it has anterior, lateral, and posterior funiculi
above T6 (posterior funiculi are separated ) it has gracile fasciculus and cuneate fasciculus

What three connective tissues membranes surround the spinal cord

dura mater, arachnoid, and pia mater

What does the dura mater form, where does it begin and end?

forms a loose sac around spinal cord and cauda equina
continuous with dura mater of brain
ends blindly at border of S2

Describe the difference between filum terminale in regards to the dura mater

Has 2 parts filum terminale internum is within the dural sac
filum terminale externum is outside of the dural sac and connects from end of dural sac/S2 to coccyx
also called coccygeal ligament

What is the region between vertebral canal and dura mater?

Epidural space that contains loose connective tissue with fat and internal vertebral venous plexus
this is where anesthetic is injected for epidural block

Describe dura maters relationship to each spinal nerve

Dura mater forms a sleeve around roots of each spinal nerve
at intervertebral foramen dura mater becomes continuous with epineurium of nerve (vonnective tissue that surrounds a nerve)

What is the arachnoid? Where does it begin and end

It is a delicate membrane applied to internal surface of dura mater
It is continuous with arachnoid around brain
extends to lower end of dural sac
also lines inside of dural sleeves around roots of spinal nerves which creates small lateral extensions of subarachnoid space

What is the subdural space

potential space between dura mater and arachnoid
(subdural hematoma)

What is the subarachnoid space? Beginning and end? What is inside space?

space between arachnoid and pia mater
continuous with subarachnoid space around brain
terminates at level of S2
filled with CSF

What is the lumbar cistern and what it contains

it is the subarachnoid space inferior to conus medullaris and contains CS, ventral dorsal roots of cauda equina, and filum terminale internum (no spinal cord)
this is where lumbar puncture is done at L3/L$ or L4/L5 interspaces

What is the pia mater

membrane that adheres to surface of spinal cord and roots of spinal nerves (as far as intervertebral foramen)
it continues beyond conus medullaris as thin thread - filum terminale

What is a denticulate ligament

it is an extension of pia mater in the coronal plane that helps stabilize spinal cord within dural sac
attaches medially to side of spinal cord, between ventral and dorsal roots
extends accross subarachnoid space and attaches laterally to dura mater

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