Nervous System 3 Flashcards by Jhaunte Braithwaite

Summarize the meninges of the spinal cord

Continuous with cranial meninges

Dura mater
- tough mother
- thick outer layer
- Continuous with cranial dura & epineureum
- Dural sac extends to 2nd sacral vertebrae
Arachnoid mater
- middle layer
- continuous with arachnoid of brain
Pia mater
- thin inner layer
- adheres to surface of brain & spinal cord
- denticulate ligament
  - triangular extensions
  - suspend spinal cord in the dural sheath

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What are the CNS spaces?

Epidural space-

between wall of vertebral canal & dura
contains fat & connective tissue

Subdue also space

between dura & arachnoid
contains interstitial fluid

Subarachnoid space

Between arachnoid & pia
contains cerebral spinal fluid(CSF)

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Describe the dimensions of the spinal cord?

Extends from medulla oblangata to 2nd lumbar vertebra in adults
-3rd to 4th lumbar vertebra in infants

42-45cm (16- 18 in.)

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What are the regions of the spinal cord ?

Cervical
Thoracic
Lumbar
Sacral
Coccygeal

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What is the cauda equina?

Roots of lumbar, sacral & coccygeal nerves

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What is the filum terminale?

extension of pia mater

- anchors spinal cord to coccyx

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What is the conus medullaris?

termination of spinal cord

- level of intervertebral disc of L1-L2 in adults

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Where is the lumbar enlargement?

T9 to T12

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Where. Is the cervical enlargem3nt?

C4 to T1

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How many pairs of spinal nerves are there?

31 pairs-mixed nerves

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How is a lumbar puncture done?

Hollow needle inserted into the subarachnoid space

- withdrawal of CSF
    - diagnostic
- Delivery of anesthetics

L3-L4 or L4-L5

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Describe the gray matter of the spinal cord

Anterior horn
-somatic motor neurons

Posterior horn
-interneuron & axons of incoming sensory neurons

Lateral horn
-Autonomic motor neurons

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Describe the white matter of the spinal cord

Anterior white column
Posterior white column
Lateral white column

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Describe the tracts of the spinal cord

Each column contains distinct bundles of axons

Sensory tracts
- Acsending
Motor tracts
- Descending

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What are the distinguishing characteristics of the cervical segment of the spinal cord?

Relatively large diameter, relatively large amounts of white matter, oval in shape; in upper cervical segments (C1-C4), posterior gray horn is large, but anterior gray horn is relatively small; in lower cervical segments(C5 and below), posterior gray horns are enlarged and anterior gray horns are well-developed

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What are the distinguishing characteristics of thoracic segments of the spinal cords?

Small diameter is due to relatively small amounts of gray matter; except for first thoracic segment, anterior and posterior gray horns are relatively small; a small lateral gray horn is present

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What are the distinguishing characteristics of the

Lumbar segments?

Nearly circular; very large anterior and posterior gray horns; relatively less white matter than cervical segments

What are the distinguishing characteristics of the sacral segment?

Relatively small, but with relatively large amounts of gray matter; relatively small amounts of white matter; anterior and posterior gray horns are large and thick

What are the distinguishing characteristics of the coccygeal segments?

Resemble lower sacral spinal segments, but much smaller

What is the arterial blood supply of the spinal cord?

Longitudinal vessels
- One anterior spinal artery
- Two posterior spinal arteries

2. Segmental spinal arteries
    Arise from:
       -Vertebral arteries
       - Posterior intercostal arteries
       - Lumbar arteries

  - supply:
     - Anterior & posterior radicalar arteries
     - Segmental medullary artery

What are the veinous blood supply of the spinal cord?

Longitudinal

2 pairs on each side by anterior and posterior roots
Anterior spinal vein
Posterior spinal vein
Drain into internal plexus

Internal vertebral plexus

epidural space
drain into segmental veins

What are dermatome?

Area of skin that provides sensory input to CNS via one pair of spinal nerves

What is the reflex arc?

Fast, involuntary response

Reflex arc

Stretch stimulates sensory receptor (muscle spindle)
Sensory neuron excited
Within integrating center(spinal cord), sensory neuron activates motor neuron
Motor neuron excited
Effector (same muscle) contracts and relieves the stretching

Summarize the spinal cord structure

Nerve fiber
-Axon and glial cells

Endoneurium
-Surrounds a nerve fiber

Perineureum
-Surrounds a bundle of nerve fibers (fascicle)

Epineureum
-Surrounds all fascicles to form a a single nerve

Nerve
-All bundles of axons & associated Neuroglial cells wrapped in connective tissue

Summarize organization of spinal nerves

1. Ventral horn of spinal cord—> ventral rootlets—> ventral roots- -> spinal trunk —> ventral/dorsal ramus—> body organs 2. Body organs—> dorsal/ventral ramus—> spinal nerve trunk—> dorsal root ganglia —> dorsal root—> dorsal rootlets—> dorsal horn of spinal cord

Where is the dorsal rami?

Deep muscles and skin of posterior trunk

Where is the ventral rami?

Muscles and structures of upper & lower limbs -lateral and ventral regions of trunk

Where is the meningeal branch?

- reenters the vertebral canal | - vertebrae, ligaments, vessels & meninges

Where are rami communicantes found ?

Components of the autonomic nervous system

What does the posterior column of the somatic sensory pathways consist of ?

- Cuneate fasciculus - Nerve impulses for touch, pressure, vibration & proprioception from upper limbs, upper trunk, neck & posterior head - Gracile fasciculus - Nerve impulses for touch , pressure & vibration from lower limbs & lower trunk

What does the anterolateral pathway of the so,attic sensory pathway?

Lateral spinothalamic -nerve impulses for pain & temperature Anterior spinothalamic -nerve impulses for itch, tickle & crude touch

What are the somatic motor pathways?

Motor (descending) - direct pathways - lateral corticospinal - nerve impulses from motor cortex to skeletal muscles on opposite side of the body for voluntary movement of distal limbs - Anterior corticospinal - nerve impulses from motor cortex to skeletal muscles on opposite side of the body for voluntary movement of trunk and proximal limbs

What happens if there is damage to the lower motor neuron (LMN)?

- Severe damage to ventral root results in flaccid paralysis (limo and unresponsive) - skeletal muscles cannot move either voluntarily or involuntarily - Without stimulation, muscles atrophy

What happens when there is damage to upper motor neurons ?

Spastic paralysis occurs Muscles affected by persistent spasms and exaggerated tendon reflexes Muscles remain healthy longer but movements are no longer subject to voluntary control Muscles commonly become permanently shortened

How does transfection affect the spinal cord?

Results in total motor and sensory loss in body regions inferior to site of damage - If injury in cervical region, all four limbs affected (quadriplegia) - If injury between T1 and L1, only lower limb s affected (paraplegia)

Summarize the complete transaction 9f the spinal cord

All sensory and motor tracts are severed Results in loss of all sensations and voluntary movement below the level of transection - C1-C3= No function maintained from the neck down - C4-C5= Diaphragm & breathing - C6-C7= some arm & chest muscles - T1-T3= Intact arm function - T4-T9= Control of trunk above umbilicus - T10-L1= Most thigh muscles - L1-L2= most leg muscles

What is the effect of spinal shock ?

Transient period of functional loss that follows the injury - Results in immediate depression of all reflex activity caudal to lesion - Bowel and bladder reflexes stop, blood pressure falls, and all muscles (somatic and visceral)below the injury are paralyzed and insensitive - Neural function usually returns within a few hours following injury - If function doesn’t resume within 48 hours, paralysis is likely permanent

What are the effects of Amyotrophic lateral Sclerosis (Lou Gehrig’s disease)?

- Progressive destruction of motor neurons - Lose ability to speak, swallow, breathe - fatal disease with a median survival 3 years - cause unknown

What are the effects of poliomyelitis?

Virus destroys anterior horn motor neurons. Victims die from paralysis of respiratory muscles Virus enters body in feaces contaminated water(public swimming pools

What are shingles?

Herpes zoster - virus that causes chicken pox - Acute infection of the peripheral nervous system - after recovery from chicken pox, virus retreats and remains dominant in dorsal root ganglia - Reactivated virus travels down sensory neurons from affected dorsal root ganglia - dermatomal rash