Chapter 12 : Spinal Cord and Spinal nerves

CHAPTER 12: Spinal Cord & Spinal Nerves • Spinal Cord (Structure, Function) • Spinal nerves • Meninges (Layers, Roles) • Meningitis (Causes, How ID, Treat, Complications (NOT treat Quickly) • Injections (Spinal & Epidural Anesthesia): Advantages of each • White vs Gray Matter • Reflex (Definition, 5 parts) • Reflex Classifications, Stretch, Polysynaptic • Spinal Nerve Structure / Layers • Spinal nerves #, where exit, MIXED nerves • Plexus (Definition, Advantage, 4 Plexus area, Why overlap?) • For Each Plexus: What nerve(s) did we discuss, what role do they perform, what happens with injury CHAPTER 12 pt 2 : Spinal Cord & Spinal Nerves {CONTINUED} • Thoracic Outlet Syndrome (ALL) • Dermatomes (Definition, Function?) • Spinal Stenosis

Describe the structure of the Spinal cord. (location,

• Location: Extends from the foramen magnum to the 2nd lumbar vertebrae level

• Forms the Conus medullaris (wider @ top w two areas of enlargement, Separates into Cauda equine (horse tail)

Describe the functions of the spinal cord

• major communication with between the Brain and perineal nervous system

• integration of info and produces a response through REFLEX MECHANISMS

What nervous system does the spinal cord belong to ?

The Central Nervous system (CNS)

How many layers do the Meninges have?

What are they called?

three.

1. Dura Mater

2. Arachnoid mater

3. Pia Mater

Meninges (1): Dura Mater

• epidural space ( btwn bone & dura mater)

• Extremely strong

• Separates to enclose the Dural Venous Sinuses

• 2 layers

  • Superficial Periosteal Layer (not in spinal cord)

  • Deeper meningeal layer

Meninges (2): Archnoid Mater (location?

Location: under subdural space (btwn dura and arachnid mater)

• Archnoid granulations protrude into superior sagittal sinus

• Absorbs cerebral spinal fluid into Venous Blood of Sinus

Meninges (3): Pia Mater

Location: Subarachnoid space (btwn Arachnoid and Pia mater)

• spider- web like

• Blood vessels and cerebral spinal fluid here

• “gentle mother” delicate with tiny BV’s

• Clings to brain

What are the Meninges?

Def: 3 thin connective tissue membranes that cover and provide protection for the Central nervous system

they also enclose the venous sinuses

they also have Ceriveal spinal fluid (csf)

Meninges (1) : Dura Mater: What are the 3 types of separations that forms the Dural Septa (abbrev.- FFT)

1. Falx Cerebri

2. Falx Cerebelli

3. Tentorium Cerebelli

What is Meningitis?

what is it caused by?

Meningeal inflammation

Caused by bacteria or Virus

Injections: Spinal Anesthesia (block)

• prevents pain in lower body regions

• Advantage : stronger anesthesia into CSF with a faster effect

Injections: Epidural Anesthesia

• needle not thru dura mater, drugs diffuse into CSF

• Advantage: longer lasting

what is Gray matter?

consists of neuron cell bodies, dendrites and axons

What is white matter?

Consists of myelinated axons → nerve tracts

Define reflex

Automatic response to Stimulus, No conscious thought drives it

• Protective (Somatic Reflexes)

• Maintains homeostasis (Autonomic Reflexes) = Stable BP.
  

5 parts of reflex

stimulus→ sensory (afferent) neuron → Integration center (interneuron) → motor neuron (efferent) → effector

What are the 2 Reflex classifications?

1. Monosynaptic : only 1 synapse

   Sensory receptor: muscle spindle

   SIMPLEST REFLEX

2. Polysynaptic : more than 1 synapse, interneuron

   prevents falling by shifting weight

   withdrawal reflex: flexor response to pain stimuli

   crossed extensor reflex: @ same time as withdrawal reflex, stimulates extensor muscles to support body

Spinal nerve structure

Axon

• Surrounded by Endoneurium = delicate loose CT (areolar)

Fascicles

• packaged

• surrounded by Perineurium = dense irregular CT

Perineurium in concentric cell layers

• up to 15 layers thick

Epineurium

• binds fascicles together to form NERVE

• dense irregular CT

CT coverings make periphearal nerves TOUGH

Spinal nerves are part of what NS?

Where do they emanate from?

• Peripheral nervous system (31 pairs)

• Emanate from the spinal cord

Spinal nerve

Short (1-2 cm)

Quickly branches into Dorsal, ventral ramus and meningeal branch

Where do the 5 spinal nerve areas exit?

Cervical = C1-C8 and C1 exits btwn skull and C1 vertebrae

Thoracic = T1-T12

Lumbar = L1-L5

Sacral = S1- S5 and Exits from sacrum thru sacral foramina

Coccygeal = Co (1)

What are mixed nerves?

made up of Sensory and motor

Define Plexus. What are the plexuses formed by?

Intermingling of nerves. Formed from Ventral Rami of different spinal nerves = Roots join together.

What are the advantages of the Plexus’s

Damage to 1 spinal segment/ root = NOT fully paralyzed limb muscle

name the 4 plexus areas. + associated nerves

1. Cervical Plexus

   Spinal nerves: C1-C4

2. Brachial Plexus

   Spinal nerves: C5- T1

3. Lumboscaral Plexus

   spinal nerves: L1-L4

4. Coccygeal Plexus

   spinal nerves: S5-Co

For Each Plexus: what role do they perform, what happens with injury.

CP:

• Deep in the neck

• intervals superficial neck skin (cutaneous nerves) & hyoid bone muscle

• phrenic nerve: innervates the diaphragm

• Irritation of Phrenic nerves = hiccups (diaphragm spasms)

• Injury= paralyzed diaphragm and respiratory arrest

BP (brachial plexus)

• 5 roots that are deep to the sternocleidomastoid

  • Axillary

  • Radial

  • Musculocutaneus

  • Ulnar nerves

  • Median nerves

• Injury: xs Arm Pull or Blow to Superior Shoulder

  • Severe = Weaken or Paralyze Upper Limb

LSP

• Lies within Psoas Major Muscle

• Femoral Nerve (under Inguinal ligament: Motor branches to Quads, Cutaneous to anterior thigh & Medial lower leg)

• Obturator Nerve (Through Obturator foramen) Innervates Adductors

• Sciatic Nerve = Tibial & Common Peroneal Nerves = L4-S3: LARGEST NERVE IN THE BODY

Coccygeal Plexus

• Motor innervation to Pelvic Floor Muscles & Sensory Cutaneous over Coccyx skin area.

Thoracic Outlet Syndrome (Cause, S&S, Diagnosis, treatment, complications, preventions)

• compression of Brachial plexus OR subclavian artery or vein.

• Cause: car accident, Repetitive injury (Job, Sport), Pregnancy, Anatomical differences (Cervical rib)

• Risk Factors: Women (3x) > Men, Ages 20-50.

• Signs & symptoms : Numbness in arm/fingers, Shoulder & Neck Pain, Arm fatigue with activity, Weak grip.

• Diagnosis: Ultrasound (1st = Vascular), Xray or MRI (Cervical rib),

• Treatment: Physical Therapy, Antinflammatory meds, Injections (Steroid, Botox), Surgery

• Complications: Repetition injury: Long term injury= Chronic pain /

• Prevention: Avoid carrying heavy Backpack, Daily stretches, Exercises keep shoulder muscles strong

What are Dermatomes?

• Area of Skin innervated by Cutaneous branches of single spinal nerve

• All except C1 contribute

• ID nerves damaged with Spinal cord injury

Spinal Stenosis

problem: spinal canal / nerve roots narrowing causing compression of nerves