Connective tissue sheath: 1. __________ - consists of fibrocytes and collagen fibrils which run longitudinal to the nerve fibers 2. ___________ – divides the nerve into fascicles 3. ___________ – outermost sheath of peripheral

1. Endoneurium 2. Perineurium 3. Epineurium

Lec 1 and 2 PNS Flashcards by Nicole Xyza Junsay

The peripheral nervous system is composed of ____ and ____ systems

Somatic and visceral nervous system

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Part of PNS system that innervates the internal organs.

Visceral (autonomic) nervous system

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Spinal nerves arises from the spinal cord by 2 roots namely: ____ and _____

Dorsal and ventral root

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Dorsal root contains fibers that convey somatic and visceral _____ (motor or sensory) information to the CNS

sensory

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Ventral root of spinal nerve contains three fiber components which are the:

1.
2.
3.

These fibres have motor functions.

Large diameter axons to the extrafusal muscle
fibers
Gamma efferents that innervate the intrafusal
muscle fibers
Preganglionic visceral efferent fibers

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The spinal nerve formed by the union of the dorsal and ventral horn is a ______.

mixed nerve

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The spinal nerve formed by the union of the dorsal and ventral horn is a mixed nerve. This common nerve trunk divides into four branches namely:

1.
2.
3.
4.

Dorsal rami to the skin and deep muscles of the back
Ventral rami to the ventrolateral portion of the body wall and extremities
Meningeal ramus to the meninges, blood vessels, and vertebra
Ramus communicans which connects the common spinal trunk with the sympathetic ganglia. Consist of gray and white ramus.

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Cross section of a peripheral nerve discloses round fascicles of nerve fibers separated by connective tissue sheaths. Blood vessels penetrate the connective tissue sheath to nourish the nerve fibers.
• The fascicles contain:
1.
2.
3.
4.
5.

Schwann cells and fibrocytes
Axons
Myelin sheaths
Collagen fibrils of the endoneurium 
Blood vessels

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Connective tissue sheath:

__________ - consists of fibrocytes and collagen fibrils which run longitudinal to the nerve fibers
___________ – divides the nerve into fascicles
___________ – outermost sheath of peripheral

Endoneurium
Perineurium
Epineurium

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The Myelin Sheath is a segmented, multilamellar, lipid-rich wrapping of axons formed by the ________.

plasma membranes of oligodendrocytes (CNS) or Schwann cells (PNS)

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Function of Myelin sheath is to increase speed of conduction by ______.

saltatory conduction

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Formation (by oligodendrocytes):

Formed by a cell-to-cell interaction in which the axon destined for myelination is recognized by
proteins on the oligodendrocyte surface
The oligodendrocyte responds by producing a
flattened, sheet-like process that wraps
repeatedly around the axon.
As layers of membrane accumulate, all _______ is
excluded.
The mature sheath consists of layers of ______ (organelle) oligodendrocyte plasma membrane firmly pressed together.

cytoplasm

Oligodendrocytes plasma membrane

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The spinal and autonomic ganglia are part of the _______ nervous system.

peripheral

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The ______ contains the cell bodies of the afferent fibers that innervate both somatic and visceral structures. It is purely sensory.

spinal ganglion

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The _______ ganglion contains efferent visceral fibers. It is purely motor.

autonomic

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The autonomic ganglion contains______ fibers. It is purely motor.

efferent visceral

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A purely motor ganglion

Autonomic ganglion

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A purely sensory ganglion

Spinal ganglion

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A ______ contains bundles of fibers, either axons or dendrites, surrounded by connective tissue.

nerve

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Sensory nerves contain only _____ fibers, long dendrites of sensory neurons.

Motor nerves have only ______ fibers, long axons of motor neurons.

afferent

efferent

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_____ nerves contain both types of fibers.

Mixed

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There are ___ pairs of segmentally arranged spinal nerves.

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Classification of Nerve Fibers
Anatomically:
1.
2. 
3.

─ Diameter
─ Length
─ Presence or absence of myelin sheath

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Classification of Nerve Fibers

Functionally:
1.
2.
3.
4.
5.

─ Conduction Velocity
─ Conduction direction; afferent or efferent
─ Type of sensory modality served
─ Type of structure innervated; visceral or
somatic
─ Type of neurotransmitter

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True or false Each pair of spinal nerves innervates asymmetrically paired somites.

False -symmetrically

Each somite differentiates into a ___, ____, and _____.

myotome, sclerotome, and a dermatome.

EFFERENT FIBERS OF THE VENTRAL ROOTS innervate________ and some ventral roots contain preganglionic autonomic fibers which pass to autonomic ganglia which in turn give rise to POSTGANGLIONIC FIBERS that innervate ____, ____, and ____.

Somatic musculature blood vessels, smooth muscles, and glandular epithelium.

The cutaneous area supplied by the sensory fibers from a single dorsal root and its ganglion is called a _______.

dermatome

During dev’t, metameres migrate distally into the limb buds and arrange themselves to the ____ axis of future limb.

long

• During dev’t, metameres migrate distally into the limb buds and arrange themselves to the long axis of future limb. * As a consequence of limb dev’t, C4 dermatome comes to lie adjacent to the ___ dermatome * The dermatomes of ___ through___ lie in the upper extremity. * Dermatomes of ___ and ___ are adjacent posteriorly

T2 C5 through T1 L2 and S3

Innervation of: | C2 -

occipital protuberance

C3 -

supraclavicular fossa

Acromioclavicular joint

Lateral antecubital fossa

Thumb

Middle finger

Little finger

Median antecubital fossa

Apex of axilla

Nipple line

T10

Level of umbilicus

Upper anterior thigh

Middle anterior thigh

Medial femoral condyle

Medial malleolus

3rd MTP joint

Lateral heel

Popliteal fossa

Ischial tuberosity

S3 to S5

Anogenital region

occipital protuberance

supraclavicular fossa

acromioclavicular joint

lateral antecubital fossa

thumb

middle finger

little finger

median antecubital fossa

apex of axilla

nipple line

level of umbilicus

T10

upper anterior thigh

mid anterior thigh

medial femoral condyle

medial malleolus

3rd MTP joint

lateral heel

popliteal fossa

ischial tuberosity

anogenital region

S3 to S5

_________ plexus type – contribution from the fourth cervical is strong and that of the first thoracic is negligible

Prefixed

_________ plexus type – fourth cervical does not participate at all but the first thoracic makes a significant contribution

Postfixed

(Degeneration type) In the distal portion, the axon and myelin sheath completely disintegrate and degeneration occurs throughout the length of the fiber including terminal arborization.

Anterograde Degeneration

Initial Changes in anterograde degeneration

Accumulation of mitochondria in the axoplasm at the node of Ranvier, followed by breakdown of the axoplasm and mitochondria.

What happens after 12 hrs from injury in anterograde degeneration?

The axon becomes swollen and irregular in shape.

What happens after a few days in anterograde degeneration?

─ The axon begins to breakup into fragments myelin sheath. | ─ The myelin sheath also degenerates and fragment after a few days.

What happens in the Synaptic Terminal during anterograde degeneration?

─ Degenerating synaptic terminals begin to be filled up with electron dense products of degeneration including whorls of neurofilaments that surround swollen disrupted mitochondria.

The cell body swells and becomes distended, the nucleus is displaced toward the periphery and the Nissl bodies undergo dissolution.

Retrograde Degeneration

The extent and rapidity of changes in rretrograde degeneration depend on _____, ______, and ______.

the type of neurons involved, nature of the lesion location of the injury

4 characteristics of NEURONAL REGENERATION

1. Appearance of the Nissl bodies around the nuclear membrane 2. Swelling of the perikaryon subsides 3. The nucleus returns to its central position 4. Nissl bodies are restored to the normal amount and distribution

Failure of the nerves to regenerate is caused by the __________.

inability of the tendrils to find the proper path of re-connection

True or false Skeletal musculature innervated by motor axons in a given spinal root

True

Segmental innervation of skeletal musculature

Myotome

Segmental innervation of skeletal musculature (myotomes) worked out by: ________ ________ ________

1. Selective stimulation of ventral roots 2. Study of the pathologic changes which occur in the anterior horn cells when a ventral root or motor nerve is cut 3. Study of secondary degeneration of peripheral nerve fibers to muscle after central and peripheral lesions

Majority of muscles innervated with _______ (how many?) ventral roots

3 or 4 ventral roots

__________ of fibers from individual spinal | cord segments to a specific muscle provides clue to myotonic orgin of skeletal muscle

Peripheral projection

What spinal segment/s supply/s the motor activity below? movements of head (by muscles of the neck)

C1 to C4

movements of diaphragm (phrenic center)

C3 to C5

Movements of upper extremity

C5 to T1

Biceps tendon reflex (flexion of forearm on percussion of biceps tendon)

C5 and C6

Triceps tendon reflex (extension of forearm on percussion of triceps tendon)

C6 to C8

Radial periosteal reflex (flexion of forearm on percussion of distal radius)

C7 and C8

Wrist tendon reflex (flexion of fingers on percussion of wrist tendons)

C8 to T1

Movements of trunk

T1 to T12

Abdominal superficial reflexes (ipsilateral contraction of subjacent abdominal muscles on stroking the skin of upper, middle, & lower abdomen) ─ upper (epigastric): ____ ─ middle: _____ ─ lower: _____

T6 and aT7 T8 and T9 T10 and T12

Movements of lower extremity

L1 to S2

Cremasteric superficial reflex (elevation of scrotum on stroking skin on inner aspect of thigh)

T12 to L2

Genital center for ejaculation: ─ smooth muscle: ____ ─ skeletal muscle: _____

L1 and L2 | S3 and S4

Vesical center for retention of urine

T12 to L2

Patellar tendon reflex or knee jerk (extension of leg on percussion of patellar ligament)

L2 to L4

Gluteal superficial reflex (contraction of glutei on stroking skin over glutei)

L4 to S1

Plantar superficial reflex (flexion of toes on stroking the sole of foot)

L5 to S2

Achilles tendon reflex or ankle jerk (plantar flexion of foot on percussion of Achilles tendon)

L5 to S2

Genital center of erection

S2 to S4

Vesical center for evacuation of bladder

S3 to S4

Bulbocavernosus reflex (contraction of bulbocavernosus muscle on pinching penis)

S3 to S4

Anal reflex (contraction of external rectal sphincter on stroking perianal region)

S4, S5 and coccygeal

BRACHIAL PLEXUS Roots are mostly derived from _____ primary rami of ___ to ____ spinal nerves

ventral | C5 to T1

A ________ is the cutaneous area supplied by a single spinal nerve root; the cell bodies are located in dorsal root ganglia.

dermatome

True or false The dorsal roots contain most afferent fibers, both somatic and visceral.

True

Lec 1 and 2 PNS Flashcards

(110 cards)