Nervous System Flashcards
The nervous system allows___?
our body to respond to the external and internal enviornment
The nervous system is ___ and __ divided
structurally divided into a CNS and PNS and functionally divided into a somatic and visceral (autonomic) nervous system
what are sensory functions
Afferent- that detect internal and external stimuli and send it to the nervous system
what are motor functions?
Efferent- responding to decisions
what is a neuron
a nerve cell, contains a cell body, process like axon and dendrites
what are the processes?
processes serve as connectors to other nerurons or to receptors on target structures
what are nerves
bundles of nerve processes
What is CNS consist of?
the brain and spinal cord
what does the spinal cord travel within?
the vertebral canal
where does the spinal cord begin and end anatomically?
from the brain stem through the foramen magnum to L2 vertebral level
how many segments does the spinal cord have?
31 for all spinal nerves but compressed to the length of the vertebral column
what is the conus medullaris
located at L1-L2 where the spinal cord ends
cuada equina
is the horse tail like structure that are lower spinal nerves following the conus medullaris
Dural sac
contains meninges and CSF and surround the spinal cord and the cauda equina continues to the S2
Meninges
dura mater, arachnoid subarachnoid and pia
CSF
cereborspinal fluid located in teb sub acarachnoid space
what is a lumbar puncture?
where CSF can be withdrawn from the subarachnoid space or anesthetics injected into it. the syringe is commonly placed between L3 and L4 to avoid the spinal cord
gray matter
neuron and cell bodies
white matter
bundles of nerve fibers, often form tracts
nucleus
collections of neuron cell bodies inside the cns
ganglion
collection of neuro cell bodies outside the cns ex. dorsal root ganglion
spinal cord gray matter
Central H shaped portion of the cord, contains neuron cell bodies arrangend in horns
Spinal cord horns
Dorsal horn- sensory
ventral horn- motor
lateral horn- visceral motor (autonomic)
Motor
Efferent when the impulse is carried away from CNS to muscle glands
Sensory
afferent- when the impulse is towards the CNS from sensory organs and sensory receptors
(pain, touch, temp and proprioception)
Somatic nervous system
“voluntary”
carries general sensations and motor impulses to skeletal muscle
Autonomic nervous system
involuntary”
carries motor impulses to smooth and cardiac muscles and glands, associated with visceral sensory nerves
what is a functional neural component
each individual neuron and the nerve fibers (axon/dendrite) associated w/it will carry motor or sensory information
and
somatic or visceral information
any single nerve (bundle of nerve fibers) may carry __ functional components
one or more
types of functional neural components
somatic (general) motor somatic sensory visceral motor = autonomic visceral sensory special senses (cranial nerves only)
what is the peripheral nervous system
-all nervous tissues outside the cns
cranial, spinal and ganglia
-carries information to and from the central nervous system
Cranial nerves
12 pairs (CN1- CNXII) arise from the brain stem and diencephalon, supplies the head and neck. may carry any or all teh functional neural components
spinal nerves
31 pairs, exit below the skull and b/w the vertebrae, supply the body wall and limbs, carry all functional components except special sensations
How are spinal nerves named?
for the vertebral region they exit
8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal nerve
rootlets
attach to the spinal cord and converge to form roots
Dorsal root
posterior and carries sensory fibers
sensory neurons cell bodies are located in the dorsal root ganglion
ventral root
anterior and carries motor fibers, somatic motor neuron cell bodies are located in the ventral horn, visceral motor cell bodies are in the lateral horn
roots merge to form mixed____
spinal nerve carries both sensory and motor fibers
rami
what the spinal nerve splits into and have various mixed components and go out the the body
dorsal ramus
mix of motor and sensory fibers, supplies the vertebral column, associated muscles and skin (midline of the back)
ventral ramus
a mix of motor and sensory fibers, supplies the majority of the body wall and the limbs
dermatomes
discrete area of skin supplied by sensory fibers from a single spinal nerve includes areas supplied by both ventral and dorsal rami
shingles
the chicken pox virus lies dormant in the dorsal root ganglion (or cranial nerve eq.) then later remerges as shingles which follow along the dermatome associated with the specific ganglion involved
what does ANS supply?
visceral motor nerves, supply smooth muscle, cardiac muscle and glands.
ANS divisions
sympathetic and parasympathetic
the ANS two neuron system synapses
from CNs to the target structure there are two neurons which transmit impulse.
preganglionic (in CNS)
postganglionic (in PNS)
Sympathetic system
most wide spread throughout the body, fight or flight responses
relaxes walls of viscera, innervates arrector pili muscles contricts superfical peripheral blood vessels etc.
Where are the preganglionic neurons for sympathetic system
arise from the thoracolumbar origin in the lateral horn at spinal cord levels T1-L2
what does the sympathetic target
inside body cavity (carried by splanchnic nerves), head and neck, limbs and body wall carried by spinal nerves (blood vessels, sweat gland and arrector pili muscles
where are postganglionic cell bodies located for sympathetic system?
sympathetic chain ganlia (para vertebral ganglia (in the thorax)
and para aortic ganglia (above the abdominal aorta)
paravertebral ganglia location
two chains parallel to the vertebral column, from base of skull to the coccyx. at each level except the neck , consolidated to 3 cervical ganglia
para-aortic ganglia
located along the abdominal aorta and in the pelvis
how does the sympathetic chain attach to the spinal nerve?
via white and gray communicating rami (the little triangle from the spinal nerve)
how does the sympathetic chain connect to the para- aortic ganglia?
via splanchnic nerves (not spinal)
sympathetic pathways all begin in this same way
preganglionic cell bodies in the lateral horn t1-l2 leave via ventral root, travel via white ramus communicans to the sympathetic chain then have 3 pathways: cranial, thoracic viscera or abdominal viscera
cranial sympathetics
move up to the superior cervical ganglion, synapse in the ganlion then the post sganglionic nerves travel along blood vessels to the head
sympathetics to thoracic viscera
synapse in the sympathetic chain ganglia, postganglionic fibers now leave as cardiac/ pu,monary nerves to supply thoracic viscera
sympathetics to abdominal viscera
dont synapse in the chain ganglia leave as splanchnic nerves (still pre) , synapse in para aortic ganglia then post gang fibers supply abdominal and pelvic viscera
the only sympathetic target that use spinal nerves
body wall, neck and limbs
parasympathetic system
rest and digest
Preganglionic neurons for para symp. arise from
brain stem and spinal cord levels S2-4 Craniosacral
pregang fibers for para symp follow__
cranial nerves or pelvic splanchnic nerves. they synapse in autonomic ganglia in the head or near walls of the viscera
visceral sensory nerve
accompany autonomic fibers except they return to the spinal cord via dorsal root.
visceral sensory cell bodies are located in
dorasal root ganglion (no synapse here)
visceral sensory carry__
pain or visceral reflex info and most pain fibers tend to accompany sympathetic nerves
Axilla contains major vessels and nerves that travel __-
to and from the upper limb and the neck
brachial plexus is a network that___
network of nerves that go to and from the upper limb execpt for the trapezius muscle.
brachial plexus is formed__
formed from the ventral rami of spinal nerves C5-T1 are often known as roots of the plexus
terminal branches in the brachial plexus
result from joining and mixing of several nerve roots. so individual (named) nerves are usually composed of more than one spinal nerve. ex ulnar nerve contains C8-T1
how are the cords named in the brachial plexus
in relation to the axillary artery
what are 5 major branches in the terminal nerves of brachial plexus
median, ulnar, musculocutaneous, radial and axillary
minor branches of the brachial plexus
medial pectoral nerve( from medial cord) and lateral pectoral nerve (from lateral cord)
what does the median nerve supply?
the muscles of the anterior forearm and the thumb
what does the ulnar nerve supply?
the intrinsic muscles of the hand
what does the musculotaneous nerve supply?
the muselces of the anterior compartment of the arm. ex biceps
the radial nerve supplies__
muscles of the posterior compartments of the arm and forearm
what does the axillary nerve supply?
muscles of the shoulder (not trapezius)
what is Wrist drop
the radial nerve runs along the posterior surface of the humerous. mid shaft fractures can damage the nerve, causing weakness or paralysis of the muscles of the posterior part of the forearm. inablility to to extend the wrist will lead to weakened grip
what is carpal tunnel syndrome
median nerve crosses the wrist within a tightly bound space known as carpal tunnel. inflimmation from repetitive motion compresses the nerve leading to thumb muscle weakness and sensory deficitis along the lateral portion of the hand
