Nervous System PP Flashcards
motor neurons
-1 axon
-several dendrites- shorter and unsheathed
-axon are myelinated - myelin sheath
-muscle contraction
-control secretion
-efferent
-away from CNS to muscles and glands
sensory neurons
-do not have true dendrites
-attached to sensory
-transmit impulses to CNS
-stimulate interneurons -> motor neurons
-afferent
interneurons
-entirely in CNS
-transmit signals from sensory to motor neurons
white matter
-CNS
-composed of bundles of myelinated axons which connect the various grey matter regions together
-common origin and destination called tracts
-inner
-myelin acts as an insulator and hence nerve signals are transmitted at greater speed
gray matter
-CNS
-composed of neuronal cell bodies and dendrites
-2 different arrangements -> laminae and a nucleus
-unmyelinated nerve fibers
-functions in regions of the brain where information is processed
-outer
-laminae- neuron cell bodies in layered arrangement -> cerebral cortex, cerebellar cortex, and spinal cord
-nucleus- tight cluster of neuron cell bodies located deep in cerebral hemispheres, brainstem, and spinal cord
-make up ventral and dorsal horns
spinal cord
-gray matter on inside
-white matter outside
-opposite!
-spans from foramen magnum to L1-L2
-conus medullaris- tapered region at the end of the cord
-filum terminale- filament extending inferiorly from the end of spinal cord in the dural sac and attaches to dorsum of coccyx -> anchors the inferior end of the spinal cord
CNS
-brain- cerebrum, brainstem, cerebellum
-spinal cord- cervical, thoracic, lumbar, sacral, coccygeal
-meninges- dura mater, arachnoid mater, pia mater
PNS
-sensory receptors
-ganglia (collection of neuron cell bodies) and nerves
-cranial (12) and spinal nerves (31)
-brings sensory information to CNS
-carries motor output from CNS to initiate rxn
-able to regenerate
-endoneurium- surrounds neurolemma cells and axons
-perineurium- surrounds bundle of nerve fibers
-epineurium- surrounds a bundle of nerve fibers
cranial nerves
-afferent and efferent
-sensory, motor, autonomic
-associated with distinct brain stem nuclei and cortical structures
-most posterior and laternal nuclei -> sensory
-anterior tend to motor
-CN 1,2,8 - afferent
-CN 3,4,6,11,12- efferent
-CN 5,7,9,10- mixed
-CN 1,2 - arise from cerebrum
-remaining 10 arise from brain stem
peripheral nerves
-peripheral nerves for a particular region of the body feed into the spinal cord at a particular site -> anatomical dermatome
-injury to a specific part of the spine may affect all body parts by innervated nerves ventral to that area
cervical spinal injury
-more severe
-more of the body is affected
-C1-C4 injuries- may impair breathing
somatic nervous system
-somatic parts of CNS and PNS
-sensory and motor
-innervates all of body except viscera, smooth muscle and glands
-transmit touch, pain, temp, and position from sensory receptors
-somatic motor fibers stimulate voluntary muscle
dermatome
area of the dermis that is mainly supplied by afferent nerve fibers from the dorsal root of any spinal nerve
-C1 has no dermatome
dorsal and ventral roots
-multiple rootlets attach to anterior and posterior surfaces of the spinal cord and combine to form anterior and posterior roots
-posterior roots- afferent (sensory) from skin
-cell bodies of axons in posterior roots are in the spinal ganglia (outside the spinal cord) -> posterior root ganglia
-anterior roots- efferent- motor -> presynaptic autonomic fibers
-cell bodies of somatic axons in anterior roots are in the anterior horns in the gray matter of the spinal cords
posterior and anterior ramus supply
-Each spinal nerve divides immediately into aposterior (dorsal) ramusandanterior (ventral) ramus
-The posterior rami- supply the zygapophysial joints, deep muscles of the back (intrinsic), and overlying skin, trunk, head, neck
-anterior rami- supply the muscles, joints, and skin of the LIMBS and the remainder of the trunk.(anterolateral trunk)
arterial supply to spinal cord
-branches of vertebral, ascending cervical, deep cervical, intercostal, lumbar, and lateral sacral arteries
-3 longitudinal arteries supply the spinal cord
-anterior spinal artery formed by the union of branches of vertebral arteries and paired posterior spinal arteries
-each of which are a branch of a vertebral artery or the posterior inferior cerebellar artery
-spinal arteries run longitudinally from the medulla of the brain stem to the conis medularis of the spinal cord
-anterior and posterior spinal arteries supply only the short superior part of spinal cord
-circulation to spinal cord depends on spinal branches of ascending cervical, deep cervical, vertebral, posterior intercostal, and lumbar arteries that enter the vertebral canal through IV foramina
ANS
-sympathetic, parasympathetic, enteric
-have efferent and afferent sensory and motor signals that are sent to CNS
-preganglionic with cell body in CNS
-postganglionic with cell body in periphery that innervates target tissues
enteric
-can function independently of nervous system
-digestion
-2 ganglionated plexuses: myenteric and submucosal
-myenteric- between longitudinal and circular smooth muscle of GI tract
-submucosal- present within submucosa
-self contained
-functions off local reflex activity
-receives activity from and provides feedback to sympathetic and para
-may receive from postganglionic sympathetic neurons or preganglionic parasympathetic neurons
sympathetic
-cell bodies in enteromediolateral columns or lateral horns on spinal cord
-presynaptic fibers exit through anterior roots and enter anterior rami T1-L2 spinal nerve -> sympathetic trunks by white rami communicates
-fibers can ascend or descend to a superior or inferior paravertebral ganglion
-past to the adjacent anterior spinal nerve rami by grey rami communicates
OR
-cross through the trunk without synapsing and continue through abdominal pelvic splenic nerve to reach prevertebral ganglia
-presynaptic are short than post
ganglia
-3 cervical- superior, middle, and inferior
-12 thoracic
-4 lumbar
-5 sacral
-inferior cervical ganglion may fuse with the first thoracic -> form stellate ganglion
-all nerves distal to paravertebral ganglion are splenic
-afferent and efferent between CNS and viscera
-cardiopulmonary splenic nerves carry postsynaptic fibers for the thoracic cavity
-abdominopelvic splenic nerves pass through paravertebral without synapse -> greater, lesser, least, and lumbar splenic nerves
-synapse in prevertebral ganglia that are closer to target organ
-prevertebral ganglia are part of nervous plexuses that surround the branches of aorta -> celiac aortic or renal, superior and inferior mesenteric ganglion
-celiac receive input from superior greater splenic nerve -> innervate foregut, distal esophagus, stomach, proximal duodenum, pancreas, liver, biliary system, spleen, adrenal glands
-aortic or renal from the lesser splenic nerve
-superior and inferior mesenteric from the least and lumbar splenic nerves
superior mesenteric ganglion
-innervates midgut
-distal duodenum, jejunum, ilium, cecum, appendix, ascending colon, and proximal transverse colon
inferior mesenteric ganglion innervation
-hindgut
-distal transverse, descending, and sigmoid colon, rectum, and upper anal canal
-bladder
-externa genitalia and gonadals
parasympathetic fibers
-exit by cranial nerve CN 3,7,9,10 and S2-S4 nerve roots
-4 pairs ganglion
-all in head
-CN 3- ciliary ganglion - innervates iris and ciliary muscles of the eye
-CN 7- lacrimal, nasal, palatine, and pharyngeal glands via pterygopalatine ganglion AND submandibular and sublingual glands via submandibular ganglion
-CN 9- parotid glands via otic ganglion
-CN 10- thoracic and abdominal viscera
-sacral- descending sigmoid colon and rectum
-every other parasympathetic preganglionic synapses near or on the wall of target
-pre long than post
vagus nerve
-parasympathetic
-innervate abdominal and thoracic viscera
-4 cell bodies in medulla oblongata:
-dorsal nucleus
-nucleus ambiguous- motor fibers and preganglionic neurons that innervate heart,
-nucleus solitaris- receives afference of taste sensation and viscera
-spinal trigeminal nucleus- touch, pain, temperature of outer ear, mucosa of larynx, and part of dura
-conducts sensory information from baroreceptors of the carotid sinus and aortic arch to the medulla
sympathetic vs parasympathetic
-contrasting and coordinating affects
-innervate a lot of the same tissue
-preganglionic neuron is in the gray matter of CNS
-cell bodies of postganglionic are outside CNS in the autonomic ganglia
-postsynaptic terminate on the effector organs -> smooth muscle, modified cardiac muscle, glands
sympathetic vs parasympathetic
-postsynaptic neurons release different neurotransmitters
-norepinephrine for sympathetic (except sweat glands)
-ACh for parasympathetic
-location of the presynaptic cell bodies differentiate and which nerves conduct presynaptic fibers from CNS
ventral horn
-gray matter
-shorter
-wider
-neuron cell bodies are somatic motor neuron cell bodies
-axons exit via ventral rootlets
-innervate skeletal muscle cells
dorsal horn
-gray matter
-longer
-narrower
-interneuron cell bodies within
-interneurons receive sensory information from sensory neuron axons that enter the dorsal horn and relay information to motor neurons and/or other interneurons
lateral horn
-gray matter
-only in T1-L2 (sympathetic)
-neuron cell bodies of autonomic nervous system
-autonomic cell bodies are in other areas of the cord like S2-S4 (parasympathetic) -> but no lateral horn
dorsal root ganglion (DRG)
-only present in dorsal root
dorsal ramus
-smaller
-supplies dorsal trunk, neck, head
-visceral motor, somatic motor, and sensory innervation to and from the intrinsic back muscles, joints and vertebral column and skin
ventral ramus
-larger
-innervate ventrolateral trunk, upper limbs, lower limbs with visceral motor, somatic motor, and sensory information to and from the muscles, joints, and skin
rami communicantes
-from a ventral ramus to paravertebral (sympathetic) ganglia
-pathway for sympathetic visceral efferent and afferent neurons and visceral
white matter spinal cord
-anterior column (funiculus)
-lateral column (funiculus)
-posterior column (funiculus)
-tracts- groups of axons within CNS with common origin and destination
-ascending tracts- sensory information from PNS to neurons in brain
-descending tracts- motor information from neurons in CNS to neurons of PNS
L2-Co1
-must transverse the vertebral canal until they can exit (bc spinal cord ends)
-cauda equina-bundle of ventral and dorsal roots in the canal inferior the end of spinal cord
dura mater
-dense fibrous connective tissue
-dural sac- long tubular sheath surrounding the spinal cord
-attaches to occipital bone to approx S2
-dural sleeves- lateral extensions that cover the ventral and dorsal roots to the location where they become spinal nerve
-dural sleeves continues to cover the spinal nerve -> becomes epineurium
subdural space
-potential space between dura mater and arachnoid mater
epidural (extradural) space
-real space between bone of vertebral column and the dura mater
-contains fat, loose, connective tissue, dorsal and ventral, arteries, roots, internal vertebral venous plexus
internal vertebral venous plexus
-epidural space is filled with fat and theinternal vertebral venous plexus(Batson’s plexus)
-this plexus drains the entire length of the vertebral column
-This plexusand the external vertebral venous plexus provides a route for metastasis to the vertebrae,spinal cord, or brain from an abdominal (kidney), thoracic (breast and lung), or pelvic (prostate) tumor
-occurs bc vertebral venous plexuses lack valves and are connected with venous channels of organs external to the vertebral column
epidural abscess
-collection of pus between dura mater of brain or spinal cord and the bones of the spine and skull
-more common in the spine bc epidural space in the vertebral column is a real space.
-cranial cavity- epidural space is a potential space
-medical emergency swelling can cause permanent neurological damage
arachnoid mater
-attached to dura maters surface that faces the brain/spinal cord
-trabeculae attach to superficial surface of pia mater
-subarachnoid space- real space between arachnoid mater and pia mater that contains CSF
lumbar puncture
-sample of CSF is obtained by inserting needle into lumbar cistern (inferior to the conus medullaris)
-prevents damage to spinal cord ends @ L1/L2
-small size and mobility of nerve roots in cauda equina -> little risk of puncturing a spinal nerve root
supracristal plane
-supracristal plane crosses the L4 spinous process and the L4/5 intervertebral disc -> important landmark to find the correct interspinous space when performing a lumbar puncture
-presence of thick, subcutaneous tissue
-palpable supracristal plane is often more superior than the radiological (“actual”) supracristal plane.
Spinal Block vs Epidural Block
-spinal block- anesthesia injected into CSF of subarachnoid space (below L1/L2)
-takes effect in 1 minute
-headache after due to CSF leakage from the lumbar puncture
-epidural block- catheter placed to deliver continuous anesthetic into epidural space (below L1/L2)
-if done into the sacral canal via the sacral hiatus (caudal epidural block) ->only the S2-S4 nerve roots are anesthetized -> birth canal, pelvic floor, and external genitalia -> spares the lower extremity
-child birth
-must be administered in advance of the actual delivery
denticulate ligaments
-thickened extensions of pia mater
-traverse the subarachnoid space
-attach to dura mater
-21 pairs
-stabilize spinal cord to prevent side to side motion
disc herniation
-central herniation -> vertebral canal
-posterolateral herniation -> intervertebral foramen
-posterior/posterolateral herniation-> vertebral column -> cervical spinal cord and nerve roots, thoracic spinal cord and nerve roots, and lumbar (L2 and below) nerve roots
posterolateral herniation
-most common due to strength of centrally located posterior longitudinal ligament
-cervical posterolateral herniation- nerve impinged = lower vertebra (C5 is impinged at C4-C5) -> bc cervical nerves exit superiorly
-thoracic posterolateral herniation- nerve impinged = upper vertebrae (T3 is impinged at T3-T4)
-lumbar posterolateral herniation- nerve impinged = lower vertebrae
extrinsic back muscles
-contraction results in movement of upper limb (superficial layer) or elevation/depression of ribs
-do not move the back
-innervated by branches of ventral primary rami except trapezius is innervated by CN 11 (accessory)
intrinsic back muscles
-maintain posture and move head and vertebral column
-innervated by dorsal rami
-superficial- splenius capitis and splenius cervicis
-intermediate- erector spinae: iliocostalis, longissimus, spinalis
-deep- transversospinalis group (semispinalis)
splenius capitis and splenius cervicis
-only muscles in the superficial layer of intrinsic back muscles
-fibers are oblique and directed superolaterally
-insertions (distal attachments) are distinct
-originates at nuchal ligament and spinous processes of C7-T6
-capitis inserts on mastoid process and superior nuchal line
-cervicis inserts on transverse processes of upper cervical vertebrae (C1-C3/C4)
-innervated by dorsal rami of spinal nerves
-action- bilateral contraction that extends head and neck, unilateral contraction that laterally flexes and rotates head
erector spinae: iliocostalis, longissimus, spinalis
-intermediate layer
-from lateral to medial -> iliocostalis, longissimus, spinalis (I Love Spines)
-originates on posterior aspects of iliac crests and sacrum, sacroiliac ligaments and spinous processes of sacral and inferior lumbar vertebrae
-inserts on spinous and transvere processes of vertebrae, ribs, skull
-innervated by dorsal rami
-supplied by dorsal branches of posterior intercostal and lumbar arteries
-action- erect posture, bilateral contraction to extend vertebral column, unilateral contraction for rotation
transversospinalis group
-form transverse processes (inferiorly) to spinous processes (superiorly)
-between spinous process and transverse process
-rotation and lateral bending movement
-stabilize vertebral column
-semispinalis is the only visible
semispinalis
-most superficial of transversospinalis
-semispinalis capitis- attaches to occipital bone
-fibers are longitudinal and parallel to vertebral column
-thoracic, cervicis, capitis
-originate on transverse processes of C4-T12
-insert on occipital bone and spinous processes of thoracic and cervical region
-innervated by dorsal rami of spinal nerves
-action- maintain lordosis and balance head on the neck, bilateral contraction- extension of head and neck, unilateral contraction to rotate head and neck
greater occipital nerve
-dorsal ramus of the C2 spinal nerve
-nerve passes through semispinalis muscle and trapezius
-entirely sensory supplying skin on the back of the head
damage to CNS
-injured axons dont recover
-stumps begin to regeneration but are stopped by astrocytes
-destruction of tract
peripheral nerve degeneration
-axons degenerate distal to lesions bc they depend on cell bodies
-crushing- damages axons distal to injury -> no surgery needed bc sheaths guide regenerating axon to destination
-cut- surgery required for apposition of cut ends by suture through epineurium -> regeneration
-ischemia- crushing vasa nervorum cuts off blood supply and cause same effects as crushing or even cut damage
ascending tracts
-sensory
-dorsal columns- vibration/proprioception
-spinothalamic tract- pain/temperature
-PNS -> CNS
descending tract
-motor
-corticospinal tract- motor
-CNS -> PNS
hemi-cord/brown sequard syndrome
-damage to half of spinal cord
-affects dorsal columns, spinothalamic, and corticospinal tract
-dorsal column (proprioception/vibration) and corticospinal tract (motor) lost ipsilaterally
-spinothalamic tract (pain/temperature) lost contralaterally
anterior cord syndrome
-affects spinothalamic (pain/temperature) and corticospinal (motor) tracts
-loss of pain, temperature, and motor from injury and below
-dorsal column (vibration and proprioception not affected)
central cord syndrome
-spinothalamic tract affected
-loss of pain and temperature
-higher level of spinal cord -> innervates upper body only
-dorsal column (proprioception/vibration) and corticospinal tract (motor) unaffected
posterolateral cord syndrome
-dorsal column and corticospinal tract affected
-loss of vibration/proprioception and motor at injury and below
-spinothalamic tract not affected (pain and temperature)
