Anatomy Flashcards
Differences between sensory and somatomotor neurons
Sensory: Afferent, dendrites pick up signal from environment, long dendrite (sensory process), signal bypasses cell body (in dorsal root ganglia)
Somatomotor: Efferent, dendrites pick up signal from synapse, long axon, signal travels through cell body
Difference between neuron, nerve process, nerve
Neuron - one cell
Nerve process - collection of axons or sensory processes (AKA the long dendrites)
Nerve - collection of nerve processes
Difference between CNS and PNS (and where each cell body and processes reside)
CNS - brain and SC; cell bodies in gray matter/nuclei; processes in white matter/tracts
PNS - all nerves stemming from CNS (spinal nerves, cranial nerves, all autonomic nerves); cell bodies in ganglia, cell processes in nerves
Location of All Neuronal Cell Bodies
Why are vertebral horns larger in lower cervical and upper lumbar spine?
PNS: sensory (dorsal root ganglia), sympathetic (sympathetic chain ganglia, collateral ganglia), parasympathetic (within organ wall)
CNS: sensory relays (dorsal horn), motor (ventral horn), autonomic (lateral horn)
These are where nerve processes enter and leave for arm and leg sensation
When does neurulation occur?
What parts of the nervous system develop from different structures in neurulation?
Secondary Neurulation?
Neurulation: by end of 3rd week of pregnancy
Neural plate - gives rise to entire nervous system, ectoderm that contains folds/grooves (will become neural tube and crest)
Neural tube - CNS + all neurons w/ cell bodies in CNS (somatomotor + presynaptic autonomic neurons)
Neural crest - PNS + neuronal cell bodies outside CNS (sensory + postsynaptic autonomic)
Secondary neurulation: spinal cord below S2 comes from caudal eminence of MESODERM (weeks 3-6 of pregnancy)
Nomenclature of Spinal Nerves
31 total spinal nerves
C1-C7: above corresponding vertebrae
C8: below C7 vertebrae
T1-T12, L1-L5, S1-S5, Coccyx: below corresponding vertebrae (S+Coccyx are fused)
Function and pathway of spinal nerves
Fx: Innervate body wall (skin, connective tissue/fascia, muscle, bone)
- Dorsal (sensory) + Ventral (somatic) Rootlets
- converge to dorsal and ventral roots
- converge to spinal nerve proper (mixed) - nerve exits intervertebral foramen
- split to dorsal and ventral rami (mixed)
5a. dorsal ramus goes to posterior cutaneous branch
5b. ventral rami splits to lateral and anterior cutaneous branches
Components of Spinal Nerve Cutaneous branches
- Deep body wall (bone, muscle, deep/investing fascia) - ventral/dorsal rami with general sensory (pain), somatic (move), sympathetic neurons (arteries)
- Superficial body wall (skin, superficial fascia) - ventral/dorsal rami with general sensory (pain/touch), sympathetic neurons (arteries) - NO MOTOR - you can’t move skin! - except face and external anal sphincter
Dermatome
- area of skin/body wall innervated by a specific pair of spinal nerves
- lowest spinal nerve innervates anus, not feet
- to completely lose sensation in one dermatome, you must lose 3 consecutive spinal nerves - else you would have partial sensation
Nerve Plexus (give examples)
Plexus - when nerves/structures interconnect and communicate
Brachial plexus: ventral rami interconnect before going to arm (only ventral rami because dorsal rami do not go to limbs)
Lumbosacral plexus: ventral rami interconnect before going to each leg (only ventral rami for same reasons)
Autonomic rami: form plexus at every site of innervation
Types of Meninges
- Dura Mater - outermost, tough protective layer
- Arachnoid - middle, spiderweb-like, less connective tissue - flimsy, has connective fibers attaching to pia mater
Subarachnoid space full of CSF to cushion SC - Pia Mater - innermost layer, tightly adherent to surface of SC, denticulate ligaments laterally extend from pia to anchor to vertebral arches (separate rootlets in half - dorsal and ventral)
How does the spinal column develop?
What are the cauda equina, conus medularis, filum terminale, epidural spinal nerve roots?
- SC stops growing @2-3mo. pregnant (eq to vertebral column), birth (SC ends at L3), adult (SC ends @L1/L2) - damage only occurs above L1/L2 and nerve roots must descend until area of exit
- CE: horse’s tail - the dorsal/ventral roots descending from SC to vertebral exit (below L1/L2)
- CM: tapering end of SC
- FT: pia filament anchoring SC to bottom of coccyx
- ESNR: each root covered by layer of dura as they continue down to appropriate vertebrae
Differences between placing needle just below L2, Lumbar epidural, and epidural space in sacral region
- anesthetizes ALL cauda equina (everywhere below injection into subarachnoid space - all roots covered in CSF) - wears off quickly due to widespread diffusion
- anesthetizes nerves leaving lumbar spine, does not pierce dura, more prolonged effect, can add more w/o fear of CSF leakage
- doesn’t pierce dural sac (ends S2); harder landmarks and doesn’t anesthetize as many neurons
Differences between somatic and autonomic nervous system
- Somatic: innervates body wall via spinal nerves (1 neuron long - 2-3ft)
- Autonomic: innervates body wall and visceral organs (smooth muscle, cardiac muscle, glands) via autonomic nerves (2 neurons long)
Functions of Sympathetic and Parasympathetic Nervous System
Sympathetic: Increase HR/contractile force, Constrict blood vessels, Dilates Airways (more oxygenation), Dilates pupils, Raise BP
Parasympathetic - decrease HR/contractile force, constrict airways, constricts pupils, constricts smooth muscle in gut (peristalsis), glandular secretion (digestion)
Characteristics of Sympathetic Pathway
Thoracolumbar outflow (nerves only exit through ventral rootlets of T1-L2), pre-communicating WHITE myelinated distal ramus leaves spinal nerve proper and (1) synapses in sympathetic chain (paravertebral) ganglia (travel up or down to ganglia out of T1-L2), (1a) leaves post-communicating GREY proximal ramus to rejoin spinal nerve (1b) leaves to heart, lungs, esophagus (Splanchic nerves); (2) pre-synaptic neuron extends past symp chain ganglion (Splanchic) and synapses at 1/3 collateral ganglion on descending aorta, post-synaptic neurons follow main artery branches to target organs in abdomen (lower thoracic - abdomen, lumbar - pelvis) *Stellate Ganglion* T1 sympathetic trunk (big because has all nerves for C1-C7, splanchic for heart/lungs/esophagus)
Characteristics of Parasympathetic Pathway
Craniosacral Outflow (vagus nerve leaves brain - supplies gut, thoracic viscera, 2/3 colon; spinal ventral rami from S2-S4 - supplies pelvic viscera, 1/3 colon), presynaptics travel to target organ (no ganglia), synapse to post-synaptics within organ wall (very small)
Differences between visceral sensory and general sensory neurons
How does referred sensation occur?
General Sensory: innervate body wall, found in spinal nerve branches
Visceral sensory: innervate visceral organs, hitchhikers with splanchic nerves, provide dull sensation (except sharp pain due to distortion/lesion/stones)
Referred Pain: sensation originates from visceral organ, travels to correlating spinal segment in body wall, pain is sensed from dermatome of that spinal nerve! (heart > T1 > arm pain)
3 things found in every autonomic plexus
- Visceral sensory nerves
- Presynaptic parasympathetics
- Postsynaptic sympathetics
