Lecture 4: PNS Flashcards by Randi Adams

Nervous structures outside the brain and spinal cord with the exception of the dorsal root ganglia

Peripheral Nervous System

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PNS allows the ____ to receive information and take action

CNS

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All nervous system structures enclosed by bone are considered part of the ______

CNS

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Spinal nerve lesions are expressed in what way?

Myotomal/dermatomal pattern

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Peripheral nerve lesions are expressed in what way?

peripheral nerve pattern

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What parts of the neuron are in the spinal region?

nerve root
dorsal ganglia
spinal nerve

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What parts of the neuron are in the peripheral region?

rami, plexus
axons and nerve endings
Postganglionic ANS

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Where are afferent neuron cell bodies located?

Dorsal Root Ganglia

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What type of neurons carry sensory information from the outer body toward the CNS?

Afferent (sensory) Neurons

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Where are efferent neuron cell bodies located?

Ventral horn of the spinal cord

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What type of neurons relay commands from CNS to smooth and striated muscles and glands (effectors)?

Efferent (motor) Neurons

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Where are interneurons located?

within the CNS in the brain and spinal cord

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What do interneurons do?

Process information locally and convey information short distances

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Another name for a bundle of peripheral axons

Nerves

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Clusters of peripheral neuronal cell bodies

Ganglia

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Pick up stimuli from inside of outside of the body

Sensory Endings

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Axon terminals of motor neurons innervate effectors (muscle fibers and glands)

Motor Endings

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Cable-like tissues in PNS

nerves

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Nerve Trunk

a large cable like tissue grouped by numerous fascicles

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Nerve fascicles

groups of axons bound into bundles

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Small-diameter axons that share Schwann cells are referred to as:

unmyelinated

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Large-diameter axons that are fully wrapped by individual Schwann cells are referred to as:

myelinated

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___________ is a layer of delicate connective tissue surrounding the axon

endoneurium

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___________ is a layer of connective tissue surrounding a nerve fascicle

perineurium

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__________ is a tough fibrous sheath surrounding a whole nerve

epineurium

Nerve fibers with different diameters have different __________ ___________.

Conduction velocities

________ results in fascicle gliding within the nerve and the nerve gliding relative to other structures

Movement

somatic peripheral nerves are usually mixed, consisting of _______, __________, and ______ axons

sensory autonomic motor

Sensory input and motor output is divided into 4 main subdivisions:

somatic sensory visceral sensory somatic motor visceral motor (autonomic nervous system)

Somatic Sensory General Somatic Senses (Skin)

touch, pain, vibration, pressure, temperature

Somatic Sensory Proprioceptive Senses (Skeletal muscle)

detect stretch in tendons and muscle provide information on body position orientation and movement of body in space

Somatic Sensory Special Senses

hearing, balance, vision

Viceral Sensory General Visceral Senses

sensory neurons monitor stretch, temperature, chemical changes, and irritation

Viscera pain perceived to be somatic in origin is called

referred pain

Visceral Sensory Special Senses

olfaction (smell) | gustation (taste)

General somatic Motor Senses

signals contraction of skeletal muscles | under voluntary control

Visceral Motor makes up:

ANS Parasympathetic/sympathetic Regulates the contraction of smooth and cardiac muscle; controls the function of visceral organs

____ pairs of spinal nerves attach through dorsal and ventral nerve roots

Spinal nerves are named according to the spinal cord segment from which they originate. How many spinal nerves are in each segment?

``` 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal ```

Dorsal roots contain ________ fibers

sensory

Ventral roots contain _____ fibers arising from ______ ______ _______

motor | anterior gray column

Dorsal Root ganglion are home to:

afferent cell bodies

Outside the intervertebral foramen, spinal nerves re-branch as _______ and _______ ______

dorsal | ventral rami

Dorsal Rami Supply What?

The somatic motor and sensory fibers to smaller nerves that innervate the muscles and skin of the posterior head, neck, and trunk

Ventral Rami Supply What?

the muscles and skin of the limb and the lateral and anterior trunk

Where a ventral ramus communicates with a chain of sympathetic nerves

Sympathetic Rami

Another name for distal structures of ventral rami (all except for T2-T11)

nerve plexus

Four Nerve plexuses and their innervations

Cervical (C1-C4) Brachial (C5-T1) Lumbar (L1-L4) Sacral (part L4-S4)

Phrenic nerve (C3-C5) is the sole nerve of the __________

diaphragm

The Cervical plexus carries efferent neurons to:

many muscles of the neck

The Cervical plexus carries afferent neurons from:

skin of the neck, shoulder, and scalp near ear

The brachial plexus carries efferent neurons to:

muscles of the shoulder, arm, forearm, and hand

The brachial plexus carries afferent neurons from:

skin of shoulder, arm, forearm, and hand

What are the main nerves of the brachial plexus?

``` Median Ulnar Radial Muculocutaneous Axillary ```

The lumbar plexus carries efferent neurons to:

muscles of the anterior pelvis, anterior and medial thigh

The lumbar plexus carries afferent neurons from:

skin of the anterior pelvis, anterior and medial thigh, and medial leg

The sacral plexus carries efferent neurons to:

muscles of the posterior pelvis, posterior thigh, anterior and posterior leg, and foot

The sacral plexus carries afferent neurons from:

skin of the posterior pelvis, posterior thigh, anterior and posterior leg, and foot

What muscles are innervated by the musculocutaneous nerve? (Elbow flexors, 3)

Coracobrachialis Biceps brachii Brachialis

What muscles are innervated by the median nerve?

Finger Flexors and Pronators

What muscles are innervated by the Ulnar nerve?

Finger Flexors

What muscles are innervated by the radial/axillary nerve?

Elbow/Finger extensors

What muscles are innervated by the femoral nerve?

Quads

What muscles are innervated by the Common Peroneal Nerve (Fibular)?

Ankle Dorsiflexors | Extensor of the Leg

What muscles are innervated by the Obturator nerve?

Hip abductors

What muscles are innervated by the Tibial nerve?

Plantar Flexors

Neuropathy with a single nerve involvement | Traumatic Myelinopathy

Mononeuropathy

neuropathy that is multifocal random, asymmetric involvement of individual nerves

Multiple mononeuropathy

Neuropathy that involves multiple peripheral nerves with symmetric distribution Symptoms progress from distal to proximal S/S of LMN disease

Polyneuropathy

What are some causes of injury to peripheral nerves

``` Trauma Compression (entrapment) Irritation Metabolic disorders Inflammatory (neuritis) Virus Age related changes ```

What type of pathology causes temporary damage to the myelin sheath that leads to a blockage of nerve conduction with no motor and sensory function distal to the injured nerve and can recover spontaneously over days or weeks?

Neurapraxia (Seddon's Class 11)

What type of pathology causes axons and myelin sheaths to be damaged while Schwann cells, enoneurium, perineurium, and epineuirum remain in tact? The axons degenerate distally and regeneration is about 1-2mm per day.

Axonotmesis (Seddon's Class II)

What type of pathology causes a total severance/disruption of the entire nerve fiber as well as partial or total disruptions of connective tissues? It does not regenerate spontaneously and grafting is necessary to restore function.

Neurotmesis (Seddon's Class III)

In what pathology is nerve conduction still in tact in the proximal and distal segment of the nerve, but not at the area of injury?

Neurapraxia (Class I)

In what pathology is there no nerve conduction distal to the site of injury?

Axontmesis (Class II) and Neurotmesis (Class III)

Where is the most common site of compression for the radial nerve?

Radial Groove

"Saturday Night Palsy" (wrist drop) is another name for:

neurapraxia

What type of traumatic myelinopathy is caused by compression of the median nerve?

Carpal Tunnel Syndrome

List 4 common causes of polyneuropathy

diabetes mellitus virus infection nutritional deficiencies Autoimmune Disfunction

What are symptoms of small fiber involvement in polyneuropathy?

pain and temperature disturbances (numbness, painful paresthesias)

What are symptoms of large fiber involvement in polyneuropathy?

weakness, areflexia, sensory ataxia or loss of position and vibration sense