CH. 13 study guide

functions of the spinal cord

conduction, locomotion, reflexes

functions of the spinal cord - Conduction

Movement of the nerve signal (action potentials) via bundles of nerve fibers (axons)

• Afferent (sensory) pathways: Up the cord to the brain

• Efferent (motor) pathways: Down the cord from the brain

Conduction - Afferent ( ______ ) pathways

(sensory) up the cord to the brain

Conduction - Efferent ( _______ ) pathways

(motor) Down the cord from the brain

Which function of the spinal cord involves movement of the nerve signal (action potentials) via bundles of nerve fibers (axons)?

Conduction

the spinal cord is Part of the ______ nervous system

“_______” between the ______ and ______ neurons of the PNS and the brain

central, “Highway", sensory, motor

the spinal cord is a cylinder ______ tissue within the spinal _______

Neurons and ______ cells - very fragile

nervous tissue, column, glial

functions of the spinal cord - Locomotion

repetitive motions of walking that don’t require conscious thought (ex. walking)

• Conscious awareness resides in the brain

• done without conscious stimulus from the brain

• spinal cord is capable

what function of the spinal cord involves the repetitive motions that don’t require conscious thought (ex. walking)?

locomotion

functions of the spinal cord - Reflexes

involuntary, stereotyped responses to stimuli

→ automatic

what type of responses are spinal cord reflexes?

involuntary → automatic

involuntary = without ______ ______

conscious decision

ex. mallat hitting knee → lifts knee

What is a nerve?

A bundle of axons of PNS neurons

• Spinal nerves and cranial nerves

• Looks like a beige cord

• Wrapped in CT

• somas are clustered together → areas of the brain, areas within spinal cord, bulges associated with nerves

nerves are bundles of what? location?

bundle of axons of PNS neurons

where are somas clustered together in nerves? - 3 areas (2 CNS, 1 PNS)

CNS: areas of the brain 🧠 , areas within spinal cord,

PNS: bulges associated with nerves (ganglions/cluster of somas in the PNS)

spinal nerves originate at the ______ _____

spinal cord

cranial nerves originate at the _____

brain (inside cranium) 🧠

Layers of Connective Tissues of a Nerve

E_____

P_____

Ep____

Endoneurium = loose CT around 1 axon

Perineurium = overlapping, squamous cells around the fascicle

Epineurium = dense irregular CT around the entire nerve

What do Connective tissues enclose?

axons and blood vessels

Spina bifida occulta: “____”

“hidden”

• 1/few vertebrae incompletely formed

• No functional problems → because opening isn’t big enough for spinal cord material to exude

Spina bifida Cystica: external ____

external sac / cyst

• Membranes, cord

• Lose cord function below sac

• Digestive, urinary, muscle problems

• Surgery to close w/in 72 hours of birth

in what condition is the spinal cord is vulnerable, damage often occurs?

Spina bifida Cystica

Spina bifida

Vertebral arch (especially lumbrosacral) doesn’t form completely

Prevetion for Spina bifida starts before _______

ex.

conception

Folic acid supplements or green veggies, beans, enriched bread

Spinal nerves include axons of ______ and _____ neurons

sensory, motor

how do spinal nerves impact muscles below the neck (trunk and limbs)?

they innervate(supply with nerves) muscles below the neck (trunk and limbs)

how many pairs of spinal nerves are there? and where do they exit?

31 pairs

exit through the intervertebral foramen

*1st exits between skull & atlas

Spinal cord - Cervical Region

• nerves for . . .

Cervical Enlargement

• Nerves for upper limbs

Spinal cord - Thoracic Region

No Enlargement

Spinal cord - Lumbar Region

Lumbar Enlargement

• T11 to L1

• Nerves for pelvic region & lower limb

Spinal cord - Sacral Region

No Enlargement (J’ron’s 🍑)

which regions of the spinal cord include enlargement?

cervical region - cervical enlargement

lumbar region - lumbar enlargement

Meninges = ___ Layers of _____ ______ around _____ & _____

• separates the ____ ______ (soft tissue) from the ____ _____ of the vertebral column

• also separate the _____ from the _____ of the cranium

3 layers of fibrous membranes around brain & cord

• Separates the spinal cord (soft tissue) from the hard bones of the vertebral column

• also separate the brain from the bones of the cranium

What do meninges separate? *2 areas

the spinal cord (soft tissue) from the hard bones of the vertebral column

the brain from the bones of the cranium

Meninges - from outermost

Dura mater, Arachnoid mater, Pia mater(mater = mother)

Meninges - Dura Mater 🤰🏼

Tough outermost layer

Epidural space: Between dura mater & vertebrae

Good place for anesthesia administration → Adipose with blood vessels & loose CT

• Epidural administration

  • Usually done below conus medullaris

  • Still have nerves of cauda equina → can still have nerve damage (lower limbs) but more likely to regenrate

Meninges - Arachnoid mater = middle ______

middle meninge

• Arachnoid

  • Fused to dura mater

  • Between arachnoid & pia

• Subarachnoid space (SAS) - btw. arachnoid + pia

  • Mesh of fibers

  • Contains cerebrospinal fluid

Meninge - Lumbar Puncture ( _____ tap)

remove ____ from the _______ space of the lumbar cistern?

(spinal tap)

• Remove CSF from the Subarachnoid space of the lumbar cistern

• the CSF is checked for abnormal contents

• Similar placement as epidur

Meninge - Pia Mater: ______ meninge

innermost meninge

• Delicate & transparent

• Follows folds of the spinal cord

• neural material of spinal cord is vulnerable to damage from excessive movement

Anchors for the cord

• Terminal filum = thread of pia mater beyond cone

  • Pia and dura

  • Anchors inferiorly

• Denticulate Ligaments:

  • Pia

  • Anchors laterally

What reduces excessive movement in the Pia Mater?

Terminal filum and Denticulate Ligament

Spinal Meningitis

*itis = inflammation

Inflammation of brain and/or spinal cord meninges

What usually causes spinal meningitic(inflammation of brain and/or spinal cord meninges)?

viral infection (but also injury, bacteria, fungus)

Viral: More common; less severe 🦠 (enterovirus, herpes simplex)

Bacterial: Less common; brain damage & death 💀 (meningococcal, streptococcus pneumonia)

Symtoms of Spinal Meningitis

Stiff neck, head ache, vomiting, seizures

Brudzinski's neck sign: hip & knee movement when neck is flexed

inflamed meninges puts pressure on the spinal cord → inappropriate neural firing → damage to cord

Brudzinski's neck sign

hip & knee movement when neck is flexed

hip & knee movement when neck is flexed (Brudzinski’s neck sign) is a symptom of what?

Spinal Meningitis

Gray matter = ______

• Mostly made of:

• Gray because it is ________

butterfly 🦋

• somas & dendrites

• unmyelinated

Functions of Gray Matter

Lots of synapses: Processing & integration of information for decision

White matter (______)

• Bundles of ______ = tracts

• White because of _______

• Superficial to ____ _____

(outside)

• Bundles of axons = tracts

• White because of myelination

• Superficial to gray matter

Function of white matter

Conduct information through the cord: Action Potentials

Conduction = movement of info

→ nerve signal

Spinal process = (anterior or posterior?)

• Ganglion tells you ^

posterior

Ganglion tells you posterior

Butterfly wing is more narrow at ______ end

posterior

Ascending Tracts

→ start @ receptor

→ carry sensory info(afferent)

→ move up to the brain

Where do ascending tracts start and move to?

start @ receptor, move up to the brain

what info do ascending tracts carry?

sensory info(afferent)

Descending Tracts

→ start @ brain

→ carry motor info (efferent)

→ moving down to effectors

what info do descending tracts carry?

carry motor info (efferent)

where do descending tracts start and move to?

start at the brain, move down to effectors

Spinal Tracts: Decussation

Crossing that forms an “X”

Ex: If a tract begins on the left side of the brain, but crosses to (and ends) on the right side of the body

• either ipsilateral or contralateral

Decussation: Contralateral

after decussate

Starts on one side but ends on the opposite side

Decussation: Ipsilateral

IpSalateral → same

Doesn’t decussate

Starts and ends on same side

Ascending tracts usually have ___ neurons

3 (2 - 4 neurons)

→ 1st order

→ 2nd order

Lateral Spinothalamic Tract 😓 🥵

Temperature & Pain

Descending tracts only have ___ neurons

2

→ upper

→ lower

Poliomyelitis: polio virus

Destroys motor neurons

what does polio virus destroy?

motor neurons

Symptoms of poliomyelitis: polio virus

Muscle pain, weakness, loss of reflexes, paralysis, muscle atrophy, respiratory arrest

Amyotrophic Lateral Sclerosis (ALS/Lou Gehrig’s disease)

Astrocytes don’t remove glutamate → overstimulation

• Overstimulated neurons die

• Lateral spinal cord scars (Sclerosis)

unlike polio which ends when the immune system _____ the virus, ALS _____ until _____

defeats, progresses, death

What does ALS affect? 👩🏼‍🦽‍➡️

upper and lower neurons of descending (motor) pathways

Anterior Root carries ______ or _____ neurons

axons, motor

Posterior Root carries _____ of ______ neurons

axons, sensory

Since spinal nerves form by merging of the 2 roots,

All spinal nerves are ________ (both sensory & motor function)

mixed

spinal nerve → carries both ______ and ______ axons → both functions

sensory, motor

Neuralgia

Nerve pain, often from pressure on spinal nerves (sensory neurons)

Herniated disc is an example of what?

Neuralgia

Peripheral Neuropathy

neuro = nerve, pathy = condition/suffering

Loss of sensory or motor function from nerve injury

What is often seen in Peripheral Neuropathy?

Diabetes

Parathesia

Abnormal sensations of numbness, prickling, burning

Parathesia: mild symptoms + severe symptoms

• Mild symptoms from pressure on nerves (sitting on foot)

• Severe symptoms from nerve trauma/peripheral nerve disorders

Posterior: ________ process

Posterior: bulge = _______

Anterior: ______

Vertebral , ganglion, Body

Rootlets and roots are _______ to the cord

Spinal nerve is very short

Rami ( _______ ) are _______ to the cord

proximal, ( branches ), distal

Sensory neurons of the posterior root

• Carrying nerve signals from ________ receptors

• Travel to the posterior _______ where they may synapse with _______

Carrying nerve signals from sensory receptors

Travel to the posterior horn where they may synapse with interneurons

Ganglion are clumps of what?

somas in the PNS

Posterior root includes the Posterior Root Ganglion

• The ______ of ______ neurons are clustered here

• Not in spinal cord, so _____

The somas of sesnroy neurons are clustered here

Not in spinal cord, so PNS

Motor (efferent) neurons of the anterior/ventral root

• Carry “_________” to the effectors (skeletal muscles)

• No anterior root ________

• Somas of motor neurons are in the ______/ _______ horn of the spinal cord

Carry “commands” to the effectors (skeletal muscles)

No anterior root ganglion

Somas of motor neurons are in the anterior/ventral horn of the spinal cord

Shingles

Virus stays in the posterior (dorsal) root ganglion

• It’s kept in check by the immune system, but can re-emerge if the immune system is weakened (stress; age)

• Pain and/or itch can last years after outbreak

What causes chicken pox? → which causes Shingles

Varicella zoster virus

Where does the shingles virus stay in?

in the posterior (dorsal) root ganglion

Posterior ramus

Innervates muscles, joints of spine & skin of back

Anterior ramus

Gives rise to plexuses and peripheral nerves (sciatic)

Spinal Plexuses 🪾 🕸

re-branching / spider-web looking structure

Anterior rami from adjacent spinal nerves merge and re-branch (anastomoses)

Cervical Plexus - Phrenic Nerve

innervates the diaphragm (prime mover of breathing)

what does the Phrenic Nerve innervate?

the diaphragm

Peripheral Nerves (Brachial Plexus)

Ulnar, Median, Radial, Musculocutaneous, Axillary

Brachial Plexus - the ulnar and median(antebrachial + hand) are _______(posterior, anterior, anteriolateral) ?

anterior

Brachial Plexus - the Musculocutaneous are _______(posterior, anterior, anteriolateral) ?

anteriolateral

Brachial Plexus - the Axillary innervates the ______ and _____ ______

deltoid, teres minor

Brachial Plexus Injuries - Carpal Tunnel

can damage Median nerve (finger muscles) → reduce function

• can’t pincer grasp

What injury can damage Median nerve (finger muscles) → reduce function ?

and can’t pincer grasp ?

Carpal Tunnel

Brachial Plexus Injuries - Ulnar nerve AKA _____ “bone”

funny “bone”

(hand muscles)

Sensory: Loss of sensation in little/ring finger

Motor: Claw-like deformities; Can’t curl fist