The Spinal Cord & Peripheral Nervous System Lesson 7.
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Transcript of The Spinal Cord & Peripheral Nervous System Lesson 7.
The Spinal Cord & Peripheral
Nervous System
Lesson 7
Dorsal
Ventral
Horns
Spinal Cord
Dorsal root ganglion (DRG) Sensory input
Ventral root Motor output
Caudal spinal cord Cauda equina ~
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 ~
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 ~
Medulla
Dorsal column-medial lemniscal path
Spinothalamic path
Corticospinal tract
Dorsal
Ventral
Spinal Cord
Peripheral N. S.
Cranial Nerves - 12 pair Spinal Nerves - 31 pair Somatic Division
Sensory info Body Movement
Autonomic division - Homeostasis regulation ~
Cranial Nerves
From ventral surface numbered anterior posterior
Sensory, motor, or mixed Mnemonic ~
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
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 ~
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~
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 ~
Dermatomes
Sensory innervation each spinal nerve has receptive
field Overlap at distal branches
redundancy retain some sensation even if a
complete spinal nerve destroyed ~
The Lateral Pathway
Voluntary movement distal limbs 2 tracts
Corticospinal tractabout 1 million axons
Rubrospinal tractsmall part of pathway ~
Somatic N.S.: Motor Output
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) ~
Somatic Motor N. S.
Spinal Cord
Motor Neuron
Effector
ACh
Autonomic N. S.
Homeostasis Effectors
Smooth Muscle Cardiac Muscle Glands ~
Autonomic Subdivisions
Not nerve-dependent Sympathetic
Emergency, flight/fight Parasympathetic
Conservation / vegetative ~
Effector
Ganglion
Preganglionic neuron
Postganglionic neuron
Autonomic N. S.: General Features
Effector
Autonomic N. S.: General Features
ACh
Ganglionic synapse: Nicotinic (nACh) different than neuromuscular
Neuroeffector junction Sympathetic: Norepinephrine Parasympathetic: nACh & mACh ~
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 ~
Effector Responses
Effector Sympathetic Parasympathetic
Heart Respiration GI Immune system Iris (radial) (sphincter)
Sweat glands no input
Adrenal glands no input ~
Parasympathetic
Post-Pre-
Sympathetic
Adrenal Glands
ACh
Glands
Smooth muscle
NE
Sympathetic Arousal Syndrome
Fight or flight situations Diffuse sympathetic activation
Adrenal glands releases NE into blood maintains sympathetic arousal
Parasympathetic rebound antagonistic regulation ~