Lecture 2- Spinal And Autonomic Nerves Flashcards
Encephalopathy
Brain disease
Myelopathy
Disease of the spinal cord
Peripheral neuropathy
Disease of the peripheral nerves
What symptoms would indicate you are dealing with a peripheral neuropathy instead of diseases in the CNS?
Hyporeflexia, hypotonia, denervation atrophy, unilateral sensory/motor deficits, normal function cranial and caudal to lesion site
Anatomical parts of a spinal nerve
Roots, trunk, four primary branches, peripheral branches
Roots
Located in vertebral canal;
Belong to PNS, but are associated with spinal cord;
Dorsal roots= sensory;
Ventral roots= motor
Main trunk
Located in intervertebral foramen;
Very short
Spinal nerve formula
Number of vertebrae + 1 in cervical region
ex: horse vertebrae= C7 T18 L6 S5 Cd7
Horse spinal nerve= C8 T18 L6 S5 Cd7
Four primary branches of spinal nerves
Dorsal= supplies epaxial muscles and dorsal skin
Ventral= largest; supplies hypaxial muscles and skin, thoracic and pelvic lims; form brachial and lumbosacral plexus
Meningeal =supplies meninges and intervertebral discs; very small
Communicating= runs to sympathetic trunk; visceral function (ANS)
Peripheral branches of spinal nerves
Have different functional components
Can be cutaneous, muscle, or mixed
Cutaneous nerves
Somatic afferents
Visceral afferents
Visceral efferents
NO somatic efferents
Cutaneous area
Area of skin supplied by a given cutaneous nerve
Made up of autonomous zone and overlap zone
Different from a dermatome
Dermatome
Area supplied by a spinal nerve
Muscle nerves
A type of peripheral spinal nerve branch
Has all four functional components
Autonomic nervous system
General visceral efferent
Has both symp and parasymp innervation
Two neuron system- pre and post ganglionic
Postganglionic fiber
Usually unmyelinated; terminates in one of three regions:
- Paravertebral- sympathetic only (in the trunk)
- Prevertebral- between symp trunk and effector organ (symp and parasymp)
- Terminal ganglia- intrinsic plexuses of gastrointestinal, respiratory, and urogenital tracts; mostly parasymp
Location of parasymp preganglionics
Craniosacral region
Symp preganglionic location
Thoracolumbar division
Location of parasymp postganglionic
Mostly terminal ganglia
Location of sympathetic postganglionics
Mostly chain ganglia
Distribution of symp postganglionic fibers
To cardiac muscle, all glands, all smooth muscle of body
Distribution of parasymp postganglionic fibers
Cardiac muscle, glands and smooth muscle of the eye, digestive, respiratory, and urogenital systems.
NO sweat glands, skin,
Sympathetic route to head
Pregangs are located in T1-T5
Leave spinal via ventral roots of T1-T5 and join main trunk
Fibers leave main trunk and join sympathetic trunk by way of communicating branch
Fibers run cranially along symp trunk, pass through cervicothoracic ganglion, synapse in cranial cervical ganglion
Post gangs leave cranial cervical ganglion and 1. Head back to C1 and C2 through symp trunk OR 2. Go towards head via internal carotid plexus
Damage to vagosympathetic trunk
Results in Horner’s syndrome- lack of symp innervation in one side of head
symptoms:
Constriction of pupil
Protruding nictitating membrane
Partial ptosis (drooping of eyelid)
Enophthalmia- recession of eyeball within orbit
Lack of sweating EXCEPT in horses where there is an excess of sweating. This is because horses use norepinephrine rather than acetylcholine.
Symp route to abdominal/ pelvic viscera
Pregangs are in T8-L3
Enter symp trunk, and run caudally
Synapse on a number of prevertebral ganglia
Either leave the trunk via thoracic splanchnic nerves and perforate the diaphragm and enter the abdominal cavity OR leave symp trunk in lumbar region via lumbar splanchnic nerves
Those fibers destined for pelvic and urogenita synapse on the caudal mesenteric ganglion and leave via hypogastric nerve and pass through the pelvic plexus
Symp route to hindlimb
Pregangs are in L1-L3
Enter symp trunk at L4-S1 and synapse on chain ganglia
Post gangs run back to spinal nerve via communicating branch for distribution into body wall
Parasymp route to abdominal viscera
Pregangs travel out of brainstem via vagus nerve
Descend caudally via vagosympathetic trunk
Pass through thorax via dorsal and ventral vagal trunks
Reach abdominal plexuses and pass through
Synapse in terminal ganglion in effector organ
Parasymp route to pelvic viscera
Pregangs in S3-S4 travel through pelvic nerve
Descends into pelvic cavity and forms pelvic plexus
Most synapse here, but others pass through and synapse on a terminal ganglion
