1. Ch 13- Spinal Cord

2. Meninges- surround brain & sc -protection & nutrients
1. Dura mater – hard mother, outer  
SUBdural/Epidural space - space between dura mater and arachnoid mater
-used to deliver anesthetic
2. Arachnoid mater – spider mother, thin, spiderwebby
Subarachnoid space - this is the largest of the spaces between maters and this one is full of CerebroSpinalFluid (CSF) which bathes the spinal cord.
-used for spinal taps (meningitis, MS, cancers)
3. Pia mater – delicate mother, attached directly to brain & s.c., extensions that anchor the cord come off the pia matter and are known as "denticulate ligaments"
Spinal Anesthesia- pg 422

3. Meningitis Infection of meningeal membranes by bacteria/virus
Infection causes inflammation = disruption to circulation of CSF = damage/death of neurons
Vaccinations can be given to prevent some forms of meningitis
Can be diagnosed by spinal tap
Highest risk group are children under 5, followed by individuals
Newest outbreak cause by steroid injections contaminated by a fungus

4. Spinal Cord regions 1. It is the link between the brain and the PNS.
2. pathway for sensory and motor impulses
(31 pairs) cervical spinal nerves have an extra set, C8. All the others correspond to the number of vertebra in that particular spine. 1. Cervical- 8 pairs 2. Thoracic- 12 pairs 3. Lumbar- 5 pairs 4. Sacral- 5 pairs
5. Coccygeal- 1 pair

5. Anatomical landmarks to know
1. 2 longitudinal depressions a. Posterior Median Sulcus - PMS b. Anterior Median Fissure - AMF
2. 2 enlargements of the spinal cord a. Cervical enlargement (biggest) - pectoral girdle – C4-C8
b. Lumbar enlargement - supplies and innervates lower limbs
3. Conus Medullaris - L1 - tapering end of the spinal cord proper
4. Cauda Equina - L1 to sacrum - "Horse Tail" this is made up of bundles of nerves/axons
5. Filum Terminale - one terminal fiber which anchors the spinal cord to the end of the sacrum, comes off the cauda equina.

6. Internal Anatomy
Grey matter - made up of unmyelinated axons, cell bodies of neurons, & neuroglia
a. Dorsal Root - posterior - sensory nerves b. Dorsal Root Ganglion (contains sensory nerve cell bodies) c. Ventral Root - anterior - motor neurons
"AMPS" anterior/motor and posterior/sensory
*Spinal nerves start where the dorsal root ganglia and ventral root fuse or come together and join to become a mixed nerve/exit the spine at the intervertebral foramen.

7. 1. Anterior Gray Horn: cell bodies of somatic motor neurons (anterior motor) 2. Posterior Gray Horn: cell bodies of somatic sensory neurons and visceral sensory neurons (posterior sensory) 3. Lateral Gray Horns cell bodies of autonomic nervous neurons 4. "grey & white commisures" - this is where nerve impulses cross over
- remember that the right side of the brain deals with the left side of the body, etc. impulses cross over contralaterally at some point in the spine.
- Central Canal in middle- contains cerebrospinal fluid

8. White Matter- Columns/Funiculi -has myelinated & unmyelinated
1. Anterior (efferent)- ascending and descending motor 2. Lateral (efferent)- ascending and descending motor 3. Posterior (afferent)- ascending sensory to brain Fascicle/Tracts-axons in each column which share functional & structural characteristics AMPS

9. Anatomy of Spinal Nerves
3 layers of CT
Epineurium
Outermost layer
Consists of dense network of collagen fibers
Perineurium
Middle layer
Divide nerve into series of compartments which contain bundles of axons (fascicles)
Endoneurium
Innermost layer
Surround individual axons

10. Distribution of Spinal Nerves
Consist of dorsal root + ventral root
Branch to form pathways to destination
Includes motor and sensory nerves
Dermatomes:
each pair of spinal nerves controls a region of body surface sensation - the exception to this is C1, which does not.
b. from dorsal and ventral rami fibers
c. damage to the spinal nerve results in loss of sensation to a region of skin
d. this is a helpful diagnostic tool, sometimes pain is referred from one nerve to a corresponding region of skin.

11. Peripheral Neuropathies Regional loss of sensory or motor function
Due to trauma or compression
Example: if your foot “falls asleep”
Shingles
Caused by varicella-zoster virus (chickenpox)
After chickenpox, virus hides in neurons of spinal cord
Later in life, attacks neurons in dorsal roots of nerves = painful rash/blisters
Distribution of rash corresponds to dermatome nerves affected

12. Plexus- “braid” of nerves
-a group of spinal nerves that do a specific job -Nerves do not go directly to the body structure they supply -from anterior rami -cervical, brachial, lumbar and sacral *Note: the Thoracic nerves are NOT A PLEXUS.

13. 1. Cervical plexus
C1-C4 – head, neck, upper shoulders & chest Phrenic nerve- C3- C5 -diaphragm

14. 2. Brachial Plexus
C5-T1 -upper limbs and pectoral girdle. 5 major terminal branches: Axillary- armpit, shoulder Median- down the middle of the arm & hand Musculocutaneous – flexors of the arm Radial - along the radial bone, thumb, fingers 2-3
Ulnar - along ulna, little finger

15. 3. Thoracic nerves (Intercostals)
T2-T12 remember, these are not a plexus, because they directly innervate each rib space Intercostal nerves - along each rib

16. 4. Lumbar Plexus
L1-L4- abs, external genitals, lower limbs Femoral Nerve -anterior thigh/leg, medial leg & foot
Obturator nerve – adductors of leg
Genitofemoral- middle thigh and genitals
Ilioinguinal- genitals
Iliohypogastric- abs & butt

17. 5. Sacral Plexus
L4-S4- butt, perineum, lower limbs Sciatic nerve-posterior to femur, largest & longest nerve in the body, most of legs & even feet divisions fibular/peroneal divison & tibial division Gluteal- butt

18. Neuronal pools Interneurons (CNS) organized into function groups
May stimulate or depress parts of the brain/spinal cord
Five different ways organization takes place
Divergence
Spread of info from one neuron/pool to several neurons/pools
Occurs when sensory neurons bring info to CNS
Allows for message to reach multiple places at the same time
Convergence
Several neurons synapse on single post-synaptic neuron
Allow for control of same motor neurons both consciously and subconsciously
Serial processing
Information relayed from one neuron to another in stepwise fashion
Occurs when sensory info is relayed from one part of the brain to another
Parallel processing
Several neurons/pools process same info simultaneously
Divergence must take place first
Allows for responses to occur simultaneously
Reverberation
Branches of axons extend back toward source of impulse to trigger further stimulation
Positive feedback loop
Help maintain consciousness, muscular coordination and normal breathing

19. 1. Arrival of stimulus activates receptor
2. Sensory Neurons are activated and produce AP
3. Information processing in CNS
AP = release of neurotransmitters which allow post-synaptic cell (interneuron or motor neuron) to process information
4. Activation of motor neuron releases neurotransmitters
5. Release of neurotransmitters leads to response by effector

20. Classification of Reflexes
1. Development
Innate reflexes
Genetically determined
Include chewing, suckling, tracking object with eyes, blinking when eyelash touched
Acquired reflexes
Learned motor patterns enhanced by repetition
Driving, walking, skiing
2. Response
Somatic reflexes
Involuntary control of skeletal muscle contractions
Include superficial and stretch reflexes
Provide rapid response that can be modified later by voluntary commands
Visceral (automatic) reflexes: Controls actions of smooth/cardiac muscles, glands, adipose tissue

21. Classification of Reflexes
3. Complexity
Monosynaptic: one synapse, little delay between stimulus and response
Polysynaptic: multiple synapses, longer delay between stimulus and response
4. Processing site
Spinal reflexes: Processing occurs in the spinal cord
Cranial reflexes: Processing occurs in the brain

22. Spinal Reflexes The Stretch Reflex Most common monosynaptic reflex
Example: patellar reflex
Physician taps on patellar tendon
Receptors in quadriceps are stretched
Distortion of receptors stimulates sensory neurons
This leads to reflex contraction of stretched muscle = kick
Slow response can indicate defect with nerve conduction
Patellar reflex helps with balance and walking, contracts muscle automatically when weight is put on feet during standing/walking

23. Spinal Reflexes Withdrawal Reflex Type of polysynaptic reflex
Example: flexor reflex
Affects muscles of a limb
Occurs when you grab a hot pan
Grabbing hot pan stimulates pain receptors
Sensory neurons activate interneurons in spinal cord
Stimulate motor neurons in anterior gray horns
Result=contraction of flexor muscles that yanks hand away from stove
Inhibitory signals used to relax extensor muscles

24. Babinski Reflex Babinski sign (positive Babinski reflex)
Occurs in absence of descending inhibition
Normal in infants/pathological in adults
If seen in adults = sign of damage to nerve paths connecting the spinal cord and brain
Plantar reflex (negative Babinski reflex): Stroking lateral sole of foot produces curling of the toes