Nerves And Spinal Cord

August 7, 2012 by Dr. Tangen Leave a Comment

nerves and spinal cord

“You’ve got some nerve dressing me like this. If I had a spine…”

Standing up for yourself is more than a motivational slogan. Spines like to stand up. What’s really impressive is that they can bend enough to let us sit.

The spine is composed of 31 segments, each of which can be damaged. Damage toward the top of the spine can cause death. But damage at lower segments can also reduce mobility and make life miserable. Disorders of the nerves and spinal cord also can be quite painful.

Here’s what is included in this lesson:

parts of the spinal cord
disorders of the spinal cord
injury and how it impacts you
where nerves go and what they do
separate systems for sensations & motor activation

Read chapter 6 of Kalat’s Biological Psychology

Here are the resources you need:

cluster
slides
terms
notes
quiz
video

SLIDES

TERMS

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31 segments
abducens
acoustic
active transport system
anterior cord syndrome
anterior root
arachnoid membrane (web)
atrophy
autonomic dysreflexia
autonomic nervous system
autonomic responses
Bell, Charles Bell
Bell-Magendie Law
bone
bone degeneration
Brown-Séquard Syndrome
central cord syndrome
central pontine myelinosis
cerebellum
cervical
closed
coccygeal
contralateral
conus medullaris
cranial nerves
demyelination
dermatomes
dorsal root
dura matter
enteric nervous system
glossopharyngel
hemisectioned
hypoglossal
intrinsic nervous system
inverse paraplegia
ipsilatera
lumbar
Magendie, Francois
medulla oblongata
motor nerves
Myasthenia Gravis
myotome
ocularmotor
Oh, oh, oh, to touch and feel very good velvet…ah, heaven
olfactory
On old Olympic towering tops, a Finn and German viewed some hops
open
optic
paralysis
paraplegia
parasympathetic nervous system
periosteum
peripheral nervous system
phrenic nerve pacing
pia matter
pons
posterior cord syndrome
quadriplegia
reflex arcs
sacrum
sensation neurons (afferent)
shoulder (accessory)
smooth muscles
somatic nervous system
steroids
striated (stripes)
striated muscles
sympathetic nervous system
Tabes Dorsalis
thoracic
trigeminal
trochlear
vagas
ventricle
visceral sensations
visera
white matter

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NOTES

[dropdown_box expand_text=” Terms To Know” show_more=”More” show_less=”Less” start=”hide”]

Spine
- Combines
  - Strong bones
  - Flexible connectors (ligaments & tendons)
  - Large muscles
  - Sensitive nerves
- Multi-Layer
  - White Matter
  - Pia Matter = thin, waterproof
  - Arachnoid membrane (web)
  - Dura Matter = keeps spinal fluid in
  - Bone = vertebral column
  - Periosteum = bone cover
  - Skin
- Terminates in Medulla
  - Cord is shorter than structure
- Bell-Magendie Law
  - Charles Bell (1811)
    - first experimental research on spinal nerves
  - Francois Magendie (1822)
    - discovered
    - anterior root is motor
    - dorsal root is sensory
- One-way
  - Dorsal is up, ventral is down
  - 1. Conduit for sensory info up
    - collect somatosensory info for brain
  - 2. Conduit for motor info down
    - distribute motor fibers to glands and muscles
  - 3. Reflexes
    - Eye–spine–blink
- Description
  - 45 cm long in men
  - 43 cm long in women
  - 31 segments
    - pair of nerves exit each segment
    - 8 Cervical
    - 12 Thoracic
    - 5 Lumbar
    - 5 Sacrum
    - 1 coccygeal
- 8 Cervical
  - Motor nerves
    - C1-3 neck
    - C4 diaphragm
    - C5 shoulder
    - C6 wrist
    - C7 triceps
    - C8 fingers
  - Damage
    - Usually results in
    - Partial or full paralysis
    - Quadriplegia
  - C1-3
    - Breathing
    - Ventilators
    - Phrenic nerve pacing
    - Diaphragm
  - C4
    - Biceps & shoulders
  - C5
    - Wrists & hands
  - C6
    - Limited wrist usage
    - No hand control
  - C7 & T1
    - Can’t function independently
    - No dexterity in fingers
    - Limited use of arms
    - Nerves come out top of vertebrate
    - So, this is also called C8
  - Control
    - Heart rate, blood pressure
    - Body temperature, sweating
    - Autonomic Dysreflexia
    - Pain & sensory $ cause
    - Increase in blood pressure
    - Autonomic responses
- 12 Thoracic
  - Motor nerves
  - Come out bottom of vertebrates
  - T1 Hand
  - T2-12 Trunk
  - T7 & L1 Abdominals
  - T11 & L2 Ejaculations
  - Paraplegia
  - No trunk stability
  - Can’t control abdominals
- 5 Lumbar
  - Motor nerves
  - L1 Hips
  - L2 Quadriceps
  - L4 Hamstrings
  - L5 Knees
  - L4 & S1 Foot
- 5 Sacrum
  - Motor nerves
  - S1 Foot
  - S2 Penile erection
  - S3 Bowel & Bladder
  - Injury
    - Decreased control of hips
    - Urinary system
    - Legs
- Injury:
  - Lower is better
  - Less is better
- Injury Causes
  - Car crashes
  - Twist, bend, dislocation, extend
  - Falls, sports
  - Stabs and gunshot wounds
  - Cancer, infections, diseases
  - Men more likely than women
  - 80%
- Syndromes
  - Central Cord Syndrome
    - Incomplete injury
    - Called “inverse paraplegia”
    - Problems in arms, hands
    - Legs work okay
    - Injury to central core nerves, usually in cervical or upper thoracic
  - Anterior Cord Syndrome
    - Cervical spine flexed too much
      - damage to anterior of spinal cord
    - Damage blood supply from the anterior spinal artery
    - Loss of pain & temp sensations
    - Touch still works
  - Posterior Cord Syndrome
    - Rare
    - Damage to posterior area
    - Damage to posterior blood supply
    - Loss of touch but not pain
  - Brown-Séquard Syndrome
    - Injured on lateral side
    - Hemisectioned (divided in half)
    - Total hemisectioning is rare
    - Partial lesions from gunshots & penetrating knife wounds
    - Ipsilateral side of injury (same side)
    - Loss of motor function
    - Can’t feel vibration & light touch
    - Contralaterally (opposite side)
    - Loss of pain, temp. & crude touch
  - Tabes Dorsalis
    - Injury to posterior region
    - Usually from diseases (syphilis)
    - Loss of touch sensation
  - Conus Medullaris
    - Injury to tip of spinal cord at L1
    - Symptoms
      - Pain
      - Paralysis
      - Numbness
      - Incontinence
      - Loss of sensation
      - Bone degeneration
      - Muscles
        
        uncontrollably contractions
        
        unresponsive
        
        weak
        
        atrophy
- Injury
  - Assume spinal cord injury
  - Stabilize head and neck
  - Hands on both sides of head
  - Act as if spine is single unit
- Treatments
  - Steroids
  - Within 6 hours of injury
  - High doses of methylprednisolone
Terms
- Dermatome = skin area sensory info
- Myotome = muscle area motor info
Peripheral Nervous System
- Anything not in brain & cord
- Not protected by bone
- Not protected by BBB
  - I. Somatic Nervous System
    - Voluntary control of muscles
  - II. Autonomic Nervous System
    - Control of heart, stomach, etc.
- I. Somatic Nervous Sys
  - Muscles used to move the body
  - Long cylindrical shape
  - Striated (stripes)
  - Each muscle moves in one direction
  - With no acetylcholine, relaxes
- Striated Muscles
  - To move in two directions, need two antagonistic muscles
  - Flexor raise arm
  - Extensor to lower arm
  - Biceps contract; triceps relax
- Myasthenia Gravis
  - Immune system anti-bodies
  - Attack acetylcholine receptors
  - Motor neurons can’t produce enough acetylcholine
  - Symptoms
    - Weakness of eye muscles (open-close eyelid)
    - Difficulty swallowing
    - Slurred speech
    - Weakness in arms
    - Rapid fatigue
    - Unstable gait
    - Feel better after rest
- II. Autonomic Nervous System
  - Control of heart, stomach, etc.
  - Visera (Viscera); general term
    - Heart
    - Stomach
    - Intestines
  - Sensation (afferent) neurons
    - Mostly unconscious
    - Visceral sensations
    - Not divided into parasympathetic and sympathetic fibers
    - Conducted by general visceral afferent fibers
    - Automatic, reflexive
    - Always working
    - Notice it when
      - Fight or flight
      - Rest & digest
  - Regulates:
    - Smooth Muscles
      - stomach, intestines & bladder
      - around blood vessels (skin, iris)
    - Cardiac muscle (heart)
      - Unique system
      - Requires 2-neuron sequence
        
        preganglionic neuron fires first
        
        target organ neuron fires
  - Reflex arcs
    - Normally undetectable
    - Sometimes send pain signals
    - Referred pain
      - non-localized
      - Also called dermatomes
  - Three divisions
    - Sympathetic nervous system
    - Parasympathetic nervous system
    - Enteric nervous system
1. Sympathetic nervous system
- Speeds things up
- Increases blood pressure
- Increases heart rate
- Decreases digestion
- Originates in spinal cord
  - Thoracic and lumbar regions
  - Thoracolumbar outflow
- Uses acetylcholine as NT
  - Spinal cord to ganglion
- Uses norepinephrine
  - Ganglion to organ
  - Except sweat glands (ACh)
2. Parasympathetic Nervous System
- Slows things down
- Decreases blood pressure
- Decreases heart rate
- Increases digestion
- Doesn’t require quick action
  - Craniosacral outflow
  - Increase body’s supply of:
    - salivation, gastric and intestinal motility, etc
  - Axons of presynaptic neurons
    - Quite long
  - CNS to ganglion
    - Very short
    - Close to target organ
- Originates in medulla
  - Some from sacral region
- Uses ACh for NT
  - At both ganglion and organs
3. Enteric Nervous Sys
- Intrinsic Nervous System
- Meshwork of nerve fibers
- Directly controls gastro-intestinal system
  - pancreas, gall bladder, etc.
- 30 NT+
  - Includes ACh, dopamine, serotonin
  - 90% of serotonin in gut
  - 50% of dopamine in gut
Cranial Nerves
- Come directly from brain
  - 12 pair
  - 1 & 2 = cerebrum
  - 3-12 = brainstem
- On old Olympic towering tops, a Finn and German viewed some hops
- Oh, oh, oh, to touch and feel very good velvet…ah, heaven
  - Olfactory smell
  - Optic vision
  - Ocularmotor eye movement
  - Trochlear rotates eyeball
  - Trigeminal face & mouth
  - Abducens eye movements
  - Facial face & tongue
  - Acoustic sound
  - Glossopharyngel taste
  - Vagas voice & taste
  - Shoulder trapezius (accessory)
  - Hypoglossal tongue & shallow
Between Brain & Cord
- Medulla oblongata
  - Lower half of the brainstem
  - Centers that control
  - Breathing, heart rate, blood pressure, respiratory rate and vomiting
  - Helps transfer info
    - between brain and spinal cord
  - Integrates inputs
  - Last 7 cranial nerves exit here
    - Sense of touch, position, tongue
    - Opposite side of body
  - Aggression? Waterboy is wrong
  - Controls reflexes of:
    - coughing, sneezing, sucking, vomiting and salivating
  - Both white & gray matter–reversed
    - White on outside, gray on inside
    - Two parts: open and closed
    - Open: top of stem
      - Front of 4th ventricle
      - Open to the ventricle
    - Closed
      - Lower portion
      - Closed = covered by nerve fibers & central canal in middle
- Pons
  - Looks like bulge on medulla
  - Sensory signals to thalamus
  - Motor signals from cerebrum
    - to cerebellum & medulla
  - Nuclei that deal with
    - Hearing, taste & eye movements
    - Facial expressions & sensations
    - Sleep, respiration, swallowing
    - Equilibrium, posture
    - Bladder control
  - Central Pontine Myelinosis
    - Disease of demyelination
    - difficulty with balance & walking
    - difficulty swallowing & speaking

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Nerves And Spinal Cord

“You’ve got some nerve dressing me like this. If I had a spine…”

SLIDES

TERMS

NOTES

QUIZ

VIDEO

DISCUSSION ITEM

“You’ve got some nerve dressing me like this. If I had a spine…”

SLIDES

TERMS

NOTES

QUIZ

VIDEO

DISCUSSION ITEM

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