Lecture 3: Peripheral nervous system Flashcards by Misha Gandhi

what is a nervous system

A biological systems that can =
Receive and process info = stimul from environment = ext anf internal
Coordinate and carry out an apprioate action to respond to those stimuli

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What is vertebrate nervous system divided into

Cns and pns

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What is apart of structural division of nervous system

Cns =brain and spinal cord
And pns = cranial, spinal and peripheral nerves

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What is apart of functional division of nervous system

Brain and spinal cord functions
Motor eff and sensory aff

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What does cns divide into

Brain = recipes and processes sensory info, initiates motor responses
Spinal cord = carries signals to anf from brain, controls reflexive responses

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What does pns divide into

Motor eff= carries and executes signals from cns to muscles and glands
sensory aff = Carries signals (somatic and visceral) from tissues and organs to cns

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What is motor efferent divided into

Somatic = innervates skeletal muscles, voluntary
Autonomic = innervates smooth and cardiac muscle, glands, involuntary

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What is focus of ANAT 314 nervous system

Pns
Spinal cord
Sensory aff
Somatic

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Describe pathway of functional division fo vertebrate nervous system

Pns inbound stimuli —> cns processing corridnation —> pns outbound action

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Describe sensory/aff

Visceral sensory (hr, nauseam hungry) gva = usually internal, tells us about internal homeostasis of body,also joint position in space
Somatic sensory (poke, pressure,hot/cold, pain, skin, bursae, light stimuli)

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Describe motor/eff

Visceral motor = Gland secretion, vasodilation
Somatic motor = muscle contraction, possibly motion

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Describe neurons

Cell of nervous system
Basic cellular units, messengers
Communicate through chain like connections
Info travels unidrectionally as electrical impulses along neurons

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Describe generic multipolar neuron = all parts of it

Dendrite = receives info generally short
Cell = processes info
Axon = relays info in form of electricity can be v long, myelin sheath = insulation, increases speed of electrical impulses
Synapses = pass info onto other nerves or effector organ chemically, axons branch, connects with other neuron dendrites

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What is multipolar neuron

Motor/eff
Target organ = effector like muscle

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What is unipolar neuron

Pseudo uni polar = sensory aff
Sensory receptors in skin/snyovium or muscle = receives info like dendrites
Cell body between axon - branched axon, no dendrites
And then relays info to cns via axon

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Describe which type of neuron where and why

In bound stimuli = pseudounipolary sensory neuron
Synapse on neurons in spinal cord = inter neurons, brain, etc
Then outbound action = motor neuron multipolar
Many of these make up spinal nerves

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What is spinal nerve

Bundle of sensory and motor neurons
Their axons ONLY = emerge from spinal cord at regular intervals to modulate sensory and motor info from/to body’s periphery

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Describe hierarchy neurons

Mixed neuron. Bundles = aff and eff
—> nerve fibers (bundled together, like myofibrils) —> wrap anf bundle = by ct sheaths = make typical named nerve

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What else is in neuron

Blood vessels = vascular supply
And fat = insulation

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What is spinal nerve - info it carries

Mixed = sensory and motor neurons
But flow of info = unidirectional= from sensory to cns to Motor or cns to motor (if not response to sensory info)
Carried by same nerve fiber, both ways

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What is spinal nerve - direction/pathway

Skin receptor —> aff Neuron —> snyapse on interneuron in cns —> synapse on eff neuron —> muscle
Multipolar
Always going in both directions along nerve fiber but carried by individual nerves = in a particular direction

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What are spinal and named nerves

Bundles of axons motor and sensory axons
Cell bodies = in specific places

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Describe posterior dorsal root ganglion

Outside spinal cord
Group of cell bodies for the sensory neurons = aff cell bodies, right by vertebral column
Contains sensory neuron cell bodies for that spinal nerve
Pseudounipolar

Describe anterior ventral horn

Inside spinal cord
Group fo cell bodies for motor neurons
Eff = generic multipolar
Motor neuron cell bodies for that spinal nerve

Name parts of spinal nerve

Rootlets Roots Rami

Define rootlets

Axon bundles from sensory neurons - post and Motor neurons-ant Emergence of fibers Converge into roots

Define roots

Convergence of rootlets Posterior root ganglion = cell bodies of sensory nerurons

Define spinal nerve

Convergence of roots Emerges from vertebral Collumn = now mixed nerve

Define rami

First split of spinal nerve into 2 rami

Name and describe the 2 rami

Posterior ramus= angles straight back,sensory and motor to intrinsic back muscles and associated skin Anterior ramus= sensory and motor to everything else, BIGGER

What is spinal cord

PART OF cns from which spinal nerves emerg at regular intervals from superior (closest to brain) to inferior (closest to coccyx)

How are spinal nerve pairs named - all

Relation to vertebrae, bilateral symmetric Thoracic = 12, lumbar = 5, sacral =5, coccygeal = 1 = ALL NAMED AFTER SUPERIOR VERTEBRA Cervical nerves = 8, named after inferior vertebra, exception = c8, spinal nerve but no vertebra

Describe spinal cord enlargements

Cervical and lumbar = correspond with plexuses involved in providing innervation to the limbs = more neurons required

Where is cervical enlargement

Brachial plexus = c5-t1

Where is lumbar enlargement

Lumbosacral plexus = l1-s4

What is conus medullaris

Spinal cord ends at l2 = tapers to point End of cord

What is Cauda equina

Horse tail, axons of inferior spinal nerves Continuation of spinal nerves = axons

Why does cauda equina develop

Unequal growth of spinal cord (shorter) and vertebral column (longer) = axons dragged ifneriorly during their growth to exit below their respective vertebrae

Why does cauda equina develop = follow through years

3 months = vert column and spinal cord grow at same rate As newborn = drags axons down, difference, vert column outpaces spinal cord growth Biggest length cauda equina = as adult

What are meninges of spinal cord

3 membranes envelop and support anf protect brain and spinal cord

Name 3 meninges

Dura mater Arachnoid mater Pia mater

Describe dura mater

Tough mother Outer fibrous layer Most protective

Describe arachnoid mater

Spidery mother Middle layer Cushioning Underside dura mater, adhered

Describe pia mater

Tender mother Adhered to cord/brain, suspend them to dura/arachnoid via denicualte ligaments

What are denticulate ligaments

Suspends pia to other layers

What else can we see on spinal cord

More rootlets = cervical enlargement of brachial plexus, thicker, more fibers travel to periphery

Name the 3 spaces between meninges

Extradural/epidural space Subdural space Subarachnoid space

Describe extradural space

With fat Injections can be made here for pain control Upon dura mater Between bones of vert column and dura mater Venous plexus

Describe subarachnoid space

Under arachnoid mater Cerebrospinal fluid circulates in space

Describe sampling csf

Filum terminals = continuation of pia mater conus medullaris = anywhere past here = more subarachnoid space = lumbar puncture = spinal tap possible here

Describe epidural injections

Injections into epidural spavce = block sensation and/or reduce inflammation of nerves during labour, surgeries or to treat chronic pain Steroids/anesthetics injected Between vert column and lig and dura mater= numbs dorsal root ganglions nearby

How many pairs of spinal nerves

31 pairs

Describe how spinal nerves become named nerves

Spinal nerves emerge from cord, coalesce, cross over and branch again to form named peripheral nerves = Innervates multiple structures, especially in limbs Multiple spinal levels = multiple structures Ex= sciatic = comes from l4-s3, spinal nerve roots in spinal cord, 5 spinal nerves all contribute

What does each spinal nerve have

Each will have discrete area of sensory innervation, also contribute to innervation of specific set of muscles Bc of segmental organization fo spinal nerves

What are dermatomes

Discrete area of skin innervates by a single spinal nerve

What are myotomes

Group fo muscles innervates by a single spinal nerve Ex = lower limb myotomes = l3 primarily knee extensors and hip flexors, l5 = primarily hip extensors and knee flexors Clinically useful= test for dysfunction in specific areas, lose sensation and weakness of certain motions