Spinal Cord and PNS

reflexive

The spinal cord carries out ________________ actions

sensory

Are ascending axons motor or sensory?

motor

Are descending axons motor or sensory?

conduction, integration, automation

What are the three principal functions of the spinal cord?

both

Do spinal neurons receive ascending or descending inputs?

motor neurons, interneurons (central pattern generators)

During automation, input are converted to reflexive outputs by what two things?

Medullary cone

tapered tip of spinal cord

L1 adult, L3 birth

What level of the spine does the spinal cord terminate?

cauda equina

collection of spinal nerves below the end of the spinal cord in the lumbar cistern

cervical thoracic lumbar sacral coccygeal

Name the levels of the spinal cord in order

8, 12, 5, 5, 1

List the # of pairs of spinal nerves in each of the spinal cord segments from cervical to coccygeal

cervical, lumbosacral

List the enlargements found in the spine

upper limbs

The cervical enlargement correspond to the nerve plexus innervating the __________________

lower limbs

The lumbosacral enlargement correspond to the nerve plexus innervating the __________________

epidural space, thick pia mater anchor, no periosteal layer

Menigeal characteristics unique to the spinal cord

dentate ligaments

extensions of the pia that extend out from the spinal cord surface to attach and anchor the spinal cord to the dura

filum terminale

fibrous extension of the pia mater and dura mater that anchors the spinal cord to the coccyx

inside

Gray matter is on the ____________ of the spinal cord

sensory interneurons

Neurons located in the posterior horns of the spinal cord

motor neurons

Neurons located in the anterior horns of the spinal cord

autonomic neurons

Neurons located in the lateral horns of the spinal cord

gray commissure

A strip of gray matter interneurons with unmyelinated axons to connect both sides of the spinal cord

central canal

A tiny channel found within the spinal cord's gray matter, existing as an extension of the fourth ventricle

funiculi

Another name for long-range tracts, found in white matter

posterior funiciuli

white matter containing the posterior column's fibers, which transmit information concerning tactile sense from the body to the brain through 1º afferents

anterior funiculus

the white matter of the spinal cord transmitting motor control information

lateral funiculus

white matter region on each lateral side of the spinal cord composed of sensory AND motor tracts

white commissure

connects the white matter of the right and left sides of the spinal cord

white commissure

Where do myelinated tracts in the spinal cord decussate?

spinothalamic tract

Tract containing sensory fibers to transmit pain and temperature information to both sides of the both

anterior corticospinal tract

division of the corticospinal pathway that travels through the ventral (anterior) column of the spinal cord and controls axial musculature through the medial motor neurons in the ventral (anterior) horn

decreases

White matter in the spinal cord __________________ from top to bottom

dorsal root ganglia

Ascending tract first order neuron resides here

decussate

Ascending tract second order neurons always ___________

thalamus

Ascending tract third order neurons are always here

2

Descending spinal tracts are composed of what number of neurons?

upper motor, lower motor

The types of neurons in the descending spinal tract

upper motor

Which neurons in the descending tracts decussate?

muscle

Lower motor neurons have map to _________________

contralateral tactile sensation

The PCML spinal tract conveys:

Fasciculi

PCML first order comes from:

medulla, medial lemniscus

PCML second order neurons are found in the _____________, decussate, and form the ___________________

ventral posterior thalamus

PCML third order neuron are found here

anterolateral spinal tracts

conveys contralateral pain and temperature sensation

dorsal horn

anterolateral spinal tract first order neurons synapse here

anterolateral tracts (anterior and lateral funiculi)

anterolateral spinal tract second order neurons decussate and form ________________________

ventral posterior thalamus

anterolateral spinal tract third order neurons are found here when coming from spinothalamic tracts

brainstem

anterolateral spinal tract third order neurons are found here when coming from spinoreticular tracts

conveys ipsilateral nonconscious proprioception

What do we need to remember about the spinocerebellar tract?

contricospinal tracts

tract conveying contralateral conscious movement

pyramidal decussation

location at which corticospinal tract fibers cross the midline and segregate into the anterior and lateral divisions of the pathway

contralateral limbs

in the corticospinal tract, lateral divisions of the pathway control:

bilateral axial

in the corticospinal tract, anterior divisions of the pathway control:

tectospinal tract

motor tract responsible for contralateral postural muscle tone associated with turning head to auditory/visual stimuli

reticulospinal tract

motor tract responsible for bilateral routine movements through extensors and flexors

vestibulospinal tract

motor tract for ipsilateral and bilateral gross postural adjustments subsequent to head movements to maintain balance

rubrospinal tract

motor tract responsible for motor input of gross postural tone, facilitating contralateral activity of flexor muscles, and inhibiting the activity of extensor muscles

decorticate posture

The body is rigid, the arms are stiff and bent, the fists are tight, and the legs are straight out; a result of no corticospinal tract control

decerebrate posture

The arms and legs are out straight and rigid, the toes point downward, and the head is arched backward; a result of no CST or rubrospinal tract control

reticulospinal

What tract was responsible for routine movements and spinal pattern generators?

spinal roots

a bundle of axons surrounded by connective tissue that occurs in pairs, which fuse and form a spinal nerve

motor

Ventral roots are motor or sensory?

sensory

Dorsal roots are motor or sensory?

spinal nerves

Dorsal and ventral roots form:

intervertebral foramen

Where do spinal nerves exit?

ganglia

Collection of somas outside the CNS

epineurium

Dense connective tissue that surrounds entire nerve including the ganglia

nowhere, nonexistent

Where are ventral root ganglia?

Mesoneurium

connective tissue that surrounds epineurium

perineurium

coarse connective tissue that surrounds the fascicles to form a nerve-tissue barrier

endoneurium

delicate connective tissue around individual nerve fibers in nerve: "jello for the axons to float in"

Fascicles

bundles of axons, usually being a mix os sensory and motor

fenestrated

Blood vessels are ____________ outside of the perineurium

blood-nerve barrier

Similar to blood brain barrier, but found in PNS. Contains tight junctions between vascular endothelial cells

meningeal branch

spinal nerve branch that innervates the anterior dura mater and contributes to back pain

communicating rami

carry visceral motor (sympathetic) and visceral sensory neurons to and from the sympathetic chain

white

Communicating rami which allows passage for preganglionic sympathetic neurons

gray

Communicating rami which allows passage for postganglionic sympathetic neurons

dorsal rami

branch of spinal nerve that supplies nerves to muscle of the back and the skin

ventral rami

branch of spinal nerve that supplies limbs and anterior trunk

intercostal nerves

Ventral rami in the thoracic region are termed:

plexuses

Ventral rami in any other region but the thoracic region are termed:

C1-C4

Cervical plexus, innervating the neck, shoulders, and diaphragm run from:

C5-T1

Brachial plexus, innervating the upper limbs, runs from:

L1-L4

Lumbar plexus, innervating the anterior pelvis and proximal legs, runs from:

L4 - S4

Sacral plexus, innervating the posterior pelvis and distal legs, runs from:

S4-Co1

Coccygeal plexus, innervating the post-anal region, runs from:

Dermatomes

an area of the skin supplied by nerves from a single spinal root

50%

Dermatomes overlap by what percentage?

level of injury

Dermatomes are useful for identifying what?

reflexes

Synaptic connections within the spinal cord create:

stimulated, quick, involuntary, stereotyped

4 properties of reflexes

visceral, somatic

Two types of reflexes

motor, skeletal

Somatic reflexes are mostly conscious, involving ___________ neurons and ___________ muscle

autonomic, smooth/cardiac

Visceral reflexes are mostly unconscious, involving _____________ neurons and ____________ muscle

reflex arcs

neural circuits that control reflexive behavior

sensory receptor, sensory afferents, integration center (optional interneurons), motor efferents, effector cells

the order of reflex arcs

extrafusal muscle fibers

bulk of muscle is:

alpha motor neurons

What innervates the extrafusal muscle fibers?

intrafusal muscle fibers

specialized muscle fibers with sensory fibers in the middle (without sarcomeres) and sarcomeres at the ends with gamma motor neurons