use the diagram to label: 1.sensory (afferent) neuron 2. motor (efferent) neuron 3.cns 4.pns...
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Use the diagram to label:
1. Sensory (afferent) neuron2. Motor (efferent) neuron3. CNS4. PNS5. Interneuron
Spinal cord and spinal nerves
• spinal cord anatomy• spinal meninges
• where to put that needle• spinal cord terminology• spinal nerves• ascending and descending tracts• where do spinal nerves go?• dermatomes• nerves plexuses
• cervical plexus• brachial plexus
• simple reflexes• anatomy of spinal cord injuries
Medullary cone
Cauda equina
31 PAIR of spinal nerves
• 8 cervical• 12 thoracic• 5 lumbar• 5 sacral• 1 coccygeal
Spinal cord levelsSpinal nervesVertebral levels
T1
T1
T1
T1
T2
Dura mater andarachnoid
Pia mater
Subarachnoid space
1. From which space is a spinal tap taken from?2. Into which space is spinal anesthetic injected?3. Into which space is an epidural anesthetic injected?
Anatomy of the spinal cord
Posterior (dorsal) sulcusPosterior (dorsal) horn
Central canal(CSF)
Anterior (ventral) horn Anterior (ventral) fissureFissure >> sulcus
Spinal nerve
Nerve roots
Gray and White Matter
• White matter = myelinated nerve fibers • Gray matter = nerve cell bodies, dendrites, neuroglia &
unmyelinated axons
Nerve Fiber = nerve process (axon or dendrite)
Nerve = bundle of nerve fibers in PNS (mixed)Tract = bundle of nerve fibers in the CNS (mixed)
Ganglion = cluster of neuronal cell bodies in PNSNucleus = cluster of neuronal cell bodies in the CNS
1. Label anterior and posterior.2. Label a nerve root and a spinal nerve.3. What is in the central canal?4. Label the posterior (dorsal) horn.5. What is it composed of?
A simple reflex arc
Sensory neuron
Motor neuron
Info processingin CNS
Information relayed to brain - slower
** Don’t need the brain to havea reflex **
Sensory or ascending tracts Motor or descending tracts
The spinal cord is very organized – anatomically & functionally
Midbrain
Medulla
Thalamus
3rd order neuron
2nd order neuron
1st order neuron
Ascending tract(Sensory info)
Decussation in medulla
L R
Fig. 14.4(TE Art)Somatosensory cortex
Gracile fasciculusBelow T6 (legs)
Cuneate fasciculusAbove T6 (arms)
Midbrain
Thalamus
Fine touch, proprioception, pressure
Spinothalamictract
Midbrain
Medulla
pain, heat, and cold
Motor cortex
Midbrain
Medulla
Lateral corticospinal tractVentral corticospinal tract
Lower motor neurons
To skeletal muscles
Upper motor neurons
Descending tractsMotor info
Corticospinal tract
Upper motor neuronsSpastic paralysis
Lower motor neuronsFlaccid paralysis
Damage to motor neurons…..
Paralysis• loss of muscle function• causes?• para, quad, hemi – plegia
• flaccid = no reflexes• spastic = exaggerated reflexes no inhibitory control from UMN hyperreflexia
Amyotrophic Lateral Sclerosis• degeneration of upper and lower motor neurons• paralysis of voluntary muscles• Lou Gehrig 1903-1941 & Stephen Hawking 1942-
Poliomyelitis• degeneration of lower motor neurons • occurs in ventral horn• caused by polio virus
Upper motor neurons
Lower motor neurons
Diseases that damage motor neurons…..
Spinal nerves
31 PAIR of spinal nerves
8 cervical (C1 is different) 12 thoracic 5 lumbar 5 sacral 1 coccygeal
Vertebral level vs
spinal level
Thoracic cavity
Dorsal ramus
Ventral ramus
Spinal nerve
Thoracic cavitySpinal nerve = mixedRamus = mixed
Dermatome
– area of skin supplied by the sensory nerve fibers of one spinal nerve
– Characteristic pattern
– No dermatome for C1 (motor only)
– Use dermatomes to assess spinal nerve damage
You are an EMT
- Frank dove into shallow end
- you evaluate him and find:- his neck hurts
- he can breath well on his own- he can’t feel or move his legs- he can’t feel his pinky- he can feel his thumb
Where is his injury??Will he be paraplegic or quadriplegic?
Thoracic nerves (12 pairs)
Cervical plexus (C1 –C5)
Brachial plexus (C5–T1)
Lumbar plexus (L1–L4)
Sacral plexus (L4 –S4)
Sciaticnerve
sciatica
Nerve Plexuses:Ventral rami traveling together
No plexus in thoracic region
Fig. 14.13(TE Art)
C1
C2
C3
C4
C5
Phrenic nerve C3-C5
Cervical plexus• C1-C5• ventral rami• neck & shoulder• phrenic nerve
• Brachial plexus passes deep to the clavicle• Damage to brachial plexus (upper or lower motor neuron lesion?)
Thoracic nerves (12 pairs)
Cervical plexus (C1 –C5)
Brachial plexus (C5–T1)
Lumbar plexus (L1–L4)
Sacral plexus (L4 –S4)
Sciaticnerve
sciatica
Nerve Plexuses:Ventral rami traveling together
No plexus in thoracic region
Spinal cord injuries (SCI)• SCI’s are damage to the spinal cord (vs vertebral column)
• damage occurs from severing, stretching or compression
• result in loss of motor & sensory function below injury site – why?
• can be complete or incomplete
• flaccid paralysis immediately after injury (due to spinal shock)
• spastic paralysis after spinal shock subsides
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