1-49 Organization of Nervous System Flashcards
Sensory and Somatomotor Neuron (overview)
Neuron vs. neuron process vs. nerve
somatic nerve vs. autonomic nerve
- somatic: are the spinal nerves in the body wall
- autonomic nerves: primarily innervate visceral structure related to the gut
- subdivides: sympathetic, parasympathetic
Neuron: nerve cell + processes
nerve: colection of cell processes
afferet neursons: sensory carry impules to CNS
Efferent neurons: motor, away from CNS to (usually) muscles
CNS vs PNS (overview)
- CNS: brain, spinal cord
- White matter or tracts: Cell processes
- Gray matter or nuclei: cell bodies
- PNS: all nerves coming off: spinal nerves, cranial, all autonomic nerve
- Nerves: collections of cell processes
- Ganglia: collection of cell bodies
Spinal cord cross-sections C5-T2-T8-L1-L2-S2
When does neurulation start?
- End of third week
What do neural crest cells form?
- all of ganglia outside the CNS
Secondary neurulation of caudal mesoderm
Nerve Primorida
Neural tube gives rise to:
- brain
- spinal cord
- somatomotor neurons (cell bodes in spinal cord)
- preganglionic autonomic neurons (cell bodies in spinal cord)
Neural crest gives rise to:
- ALL ganglia and peripheral sensory neurons
- melanocytes in the skin
**If the nerve cell body is in the CNS, it came from the neural tube, if in the PNS its from the neural crest cells**
Spina Bifida
Neurulation defect: Bi-fid vertebrae, whether the spinal cord is open to the surface or relatively normal, al defect share an incomplete vertebral arch
31 pairs of spinal nerves
Vertebra: nerve pairs numbers
- Cervical 7:8
- Thoracic 12:12
- Lumbar 5:5
- Sacrum 5 (fused):5
- Coccyx 4 (fused):1-3 pairs
- Spinal nerves come out and formed at intervertebral foramen
- Nerve C1-C7 all come out above their respective cervical vertebrae
- C8 is the nerve that comes out AFTER C7
- T1-T12 and L1-5 nerves all come out after their respective vertebrae
- Spinal nerves innervate BODY WALL of muscle, bone, fascia, skin
- NEVER innervate visceral organs in the body cavity
Formation of spinal nerves
A typical spinal nerve (TNS)
Deep body wall vs superficial body wall
Dermatome
Area of skin that is innervated by a pair of spinal nerves (eg. c1, T5, L3)
Lowest dermatomes are at the anus not the bottom of feet
where are cell bodies located?
Meninges of spinal cord
plexus
Length pattern of spinal cord
cauda equina
filum terminale
conus medularis
- denticulate ligaments: “tooth-lie” pia mater extensions which anchor the cord to the vertebral column
- Filum terminale: inferior pia mater, extension from the cord tot he coccyz which anchors the cord inferiorly
- Cauda equina: dorsal and ventral roots belwo the end of the cord coursing toward there appropriate level of exit from the vertebral column
Anaesthesia injection concepts: epidural vs subarachnoid, lumbar vs sacral
- lumbar puncture/tap:
- needle into subarachnoid space below the L1 has little risk of damaging spinal cord since cord stops at L2
- cauda equina bathed in CSF in the subarachnoid space can be anestetized or CSF can be sampled
- since all of the cauda equina nerve roots will be anestetized all of the body below the injection point will lose feeling
- Epidural block:
- in the epidural space superficial to the dura mater within the vertebral canal
- Nerve roote/spina lnerves are anestetized instead of the cauda equina
- ALL SACRAL NERVE BLOCKS ARE EPIDURAL BECAUSE SUBARACHNOID SPACE ENDS AT S1
- epidural in lumbar region used for longer, more controlled, continous anestesia of spinal nerves
