Intro To Nerves, Plexuses DLA Flashcards
What is the central nervous system?
Brain and spinal cord
-Receives information from and sends information to the body serves as the central control unit
What is the PNS?
Everything out of the CNS
The pathways (nerves) that communicate from the body structures to the CNS and vice versa
What are the components of the nervous system?
Autonomic nervous system
The ‘autonomic’ control of the body
Contains both central and peripheral components
Somatic- relating to the body (muscles, skin, bones)
Visceral-relating to the organs (heart,vessels, digestive etc.)
What are the components of the CNS
Brain
Spinal cord
What are the components of the peripheral nervous system?
Spinal nerves (31 pairs)- from spinal cord
Cranial nerves(12 pairs)- from brain and brain stem
Somatic nerve plexuses
Visceral nerve plexuses
Enteric nerve plexuses
Sensory nerve plexuses
Autonomic nervous system sympathetic-fight or flight
Parasympathetic- rest and digest
What are the two types of tissue that makes up the internal arrangement of the spinal cord?
Made up of two types of tissue:
- Inner gray matter (nuclei)- cell bodies of neurons and glial cells
-Outer white matter(tracts)- myelinated axons, neural ‘highways”
What are the segments of the spinal cord?
Cervical, thoracic, lumbar, sacral and coccygeal
Neural cell bodies of the same function…
Are collected in the same area
What are tracts?
Composed of axons that serve the same function and travel in the same direction
Explain the general concept of afferent fibers arrangement
The general arrangement is a three neuron chain
First order arises at the organ and has two processes, one on either side of the cell body
The cell body is located in a ganglion located outside of the CNS (spinal cord/ brainstem) synapses on the next neuron in the chain
The second order arises from thee grey horn of the spinal cord or brainstem nucleus and synapses in the thalamus.
The third order arises from the thalamus and ends in the cortex
Olfactory is an exception as the thalamus is one of its elements
Describe the general arrangement of motor fibers
The general arrangement is a two neuron chain
The first (upper motor neuron-UMN) arises in the cortex and synapses in the ventral horn of the spinal cord or in the brainstem on the nucleus of the corresponding cranial nerve.
The second (lower motor neuron-LMN)- arises from the brainstem nucleus and ends in the muscle it supplies
How are sympathetic efferent fibers different from motor system?
Similar. To motor system but synapses at the sympathetic chain
How are parasympathetic fibers different from the motor system?
Similar to the motor system but synapses in the parasympathetic ganglion
Where does the spinal cord start and end? Where does it start and end?
Spinal cord begins at medulla oblangata (foramen magnum) ends at vertebral level L1-L2 (conus Medilarus)
Two enlargements: cervical & lumbar regions
What are the 31 spinal nerve pairs?
8 cervical (C1-C8)
12 thoracic (T1-T12)
5 lumbar(L1-L5)
5 sacral (S1-S5)
1 coccygeal (Co1)
What is the cauda equina?
Horses tail
Spinal nerve roots that exit from the lumbar and sacral region travels in the lumbar cistern towards their respective exit points from the vertebral canal
Where are sensiry neurablast found?
In DRG forming primary sensory nerves
Where are motor neurobkast?
Motor neuroblast (from basal plate of intermediate layer) forming somatic motor neuron
Motor neuroblast (from basal placate of intermediate layer) forming visceral motor neuron (pre-ganglionic sympathetic)
Motor neuroblast (from neuracrest) forming visceral motor neuron (post-ganglionic sympathetic) in sympathetic chain ganglion
A spinal nerve and it’s branches contain ….
Mixed fibers (sensory/motor/autonomic)
Explain the typical spinal nerve course
Dorsal (posterior) ramus- supplies intrinsic back muscles (motor) and skin over that area(sensory)
Ventral (anterior) Ramus- supplies all other muscle (motor) and skin over that area (sensory)
Sympathetic chain ganglia run down the length of the vertebral bodies (bilateral)
Sympathetic chain ganglia communicate with spinal nerve via grey (unmyelinated) and white (myelinated) rami communicants
What is a plexus?
A network of intersecting nerves from different levels or sources that combine to form new nerves with specific targets
What are the somatic plexuses?
Form from the ventral rami of spinal nerves
C1-C5= cervical plexus
C5-T1= brachial plexus
L1-L4= lumbar plexus
L5-S4= sacral plexus
Combination of somatic sensory, somatic motor and sympathetic nerve fibers
What are types of the visceral plexuses?
Combination of sympathetic, parasympathetic and visceral afferent fibers
E.g., hypogastric, celiac
What is the significance of a somatic plexus?
Muscles are formed from several myotomes
- Since myotomes are supplied by nerves that develop from the same segments
- The plexuses form to supply the muscles
- The plexuses are subject to much variation
- As a result, injury doesn’t necessarily lead to the expected clinical picture
Where are the receptors of the somatic nervous system?
Conscious sensation: pain, pressure, touch, temperature, proprioception
Where are the visceral receptors for the visceral PNS?
Organs and tissues
Distention, inflammation, ischemia, physiological changes (eg decreased oxygen and increased CO2), Abnormal muscle spasm
