the spinal cord & peripheral nervous system lesson 7
TRANSCRIPT
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The Spinal Cord & Peripheral
Nervous System
Lesson 7
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Dorsal
Ventral
Horns
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Spinal Cord
Dorsal root ganglion (DRG) Sensory input
Ventral root Motor output
Caudal spinal cord Cauda equina ~
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Spinal Cord Tracts
Major descending & ascending tracts Motor 1. corticospinal tract
distal muscles only descending tract with overt
effects 1a. Rubrospinal tract
Red nucleus to spinal cord ~
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Spinal Cord Tracts Sensory 2. Dorsal column-medial lemniscal tract
touch, vibration, & proprioception axons ascend ipsilaterally synapse then decussate at medulla
3. Spinothalamic tract (anterolateral) pain & temperature decussate at SC entry level ascends contralaterally ~
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Medulla
Dorsal column-medial lemniscal path
Spinothalamic path
Corticospinal tract
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Dorsal
Ventral
Spinal Cord
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Peripheral N. S.
Cranial Nerves - 12 pair Spinal Nerves - 31 pair Somatic Division
Sensory info Body Movement
Autonomic division - Homeostasis regulation ~
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Cranial Nerves
From ventral surface numbered anterior posterior
Sensory, motor, or mixed Mnemonic ~
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Oh
Oh
Oh
To
Touch
And
Feel
Very
Green
Vegetables
A
H
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulococlear
Glossopharangeal
Vagus
Accessory (Spinal)
Hypoglossal
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
On
Old
Olympus’s
Towering
Top
A
Famous
Vocal
German
Viewed
Some
Hops
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Spinal Nerves
1 pair for each vertebral segment 8 pr. cervical (C1-C8) 12 pr. thoracic (T1-T12) 5 pr. lumbar (L1-L5) 5 pr. sacral (S1-S5) 1 pr coccygeal ~
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Spinal Nerves
Thoracic nerves relatively smallback & ribs
Cervical, lumbar, & sacral: large nervesrest of the body
All Interconnect after leaving vertebral canal form 4 major plexuses
cervical, brachial, lumbar, sacral~
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Somatic Nervous System Sensory input
receptors DRG dorsal SC Dorsal column-medial lemniscal pathway Spinolthalamic tract
Motor output Lateral SC ventral horns muscles Corticospinal tract Rubrospinal tract ~
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Dermatomes
Sensory innervation each spinal nerve has receptive
field Overlap at distal branches
redundancy retain some sensation even if a
complete spinal nerve destroyed ~
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The Lateral Pathway
Voluntary movement distal limbs 2 tracts
Corticospinal tractabout 1 million axons
Rubrospinal tractsmall part of pathway ~
Somatic N.S.: Motor Output
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Motor N.S. Striate muscle
uninterrupted neurona motor neuron
nerve-dependent Excitatory only at neuroeffector synapse
NT is acetylcholine (ACh)cholinergic
Nicotine = direct agonist (AG) Curare = direct antagonist (ANT) ~
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Somatic Motor N. S.
Spinal Cord
Motor Neuron
Effector
ACh
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Autonomic N. S.
Homeostasis Effectors
Smooth Muscle Cardiac Muscle Glands ~
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Autonomic Subdivisions
Not nerve-dependent Sympathetic
Emergency, flight/fight Parasympathetic
Conservation / vegetative ~
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Effector
Ganglion
Preganglionic neuron
Postganglionic neuron
Autonomic N. S.: General Features
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Effector
Autonomic N. S.: General Features
ACh
Ganglionic synapse: Nicotinic (nACh) different than neuromuscular
Neuroeffector junction Sympathetic: Norepinephrine Parasympathetic: nACh & mACh ~
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Sympathetic vs. Parasympathetic
Sympathetic ganglia near spinal cord interconnected active together long-lasting effects
Parasympathetic ganglia near effector discrete active independently transient effects
Antagonistic regulation ~
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Effector Responses
Effector Sympathetic Parasympathetic
Heart Respiration GI Immune system Iris (radial) (sphincter)
Sweat glands no input
Adrenal glands no input ~
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Parasympathetic
Post-Pre-
Sympathetic
Adrenal Glands
ACh
Glands
Smooth muscle
NE
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Sympathetic Arousal Syndrome
Fight or flight situations Diffuse sympathetic activation
Adrenal glands releases NE into blood maintains sympathetic arousal
Parasympathetic rebound antagonistic regulation ~