2 Peripheral Nervous System

BRACHIAL PLEXUS a. formation b. areas supplied c. significant derivatives

a. ventral rami of spinal nerves C5-T1 b. skin and muscles of upper extremities c. ulnar, radial, and medial nerve

LUMBAR PLEXUS a. formation b. areas supplied c. significant derivatives

a. ventral rami of spinal nerves L1-L5 b. skin and muscles of proximal lower extremities (inc. area of thigh) c. femoral nerve, obturator nerve, genitofemoral nerve

COCCYGEAL PLEXUS a. formation b. areas supplied c. significant derivatives

a. ventral rami of spinal nerves S5-Coc1 b. skin over coccyx c. coccygeal nerve

INTERCOSTAL NERVES a. formation b. areas supplied c. significant derivatives

a. ventral rami of thoracic spinal nerves T1-T12 b. skin and muscles of the trunk or anterolateral wall; intercostal muscles

GANGLIA: associated to visceral (efferent) peripheral nerve fibers

autonomic ganglia

GANGLIA: made up of cell bodies of multipolar neurons

autonomic ganglia

PERIPHERAL NERVES: refers to peripheral nerves that run through the spinal or cranial nerve and root to the visceral organs they supply

autonomic nerves

smallest functional unit of the peripheral nerve

axon or peripheral nerve fiber

serves as the basis for whether or not a nerve fiber will be myelinated

axonal diameter

connect the spinal nerve with sympathetic ganglion

rami communicantes

SPINAL NERVE BRANCHES: branches that connect the spinal nerve with the sympathetic ganglion

rami communicantes / gray and white rami

PERIPHERAL NERVES: functional classification that is afferent in direction and flows from receptors towards the CNS

sensory

GANGLIA: associated to somatic and visceral afferent peripheral nerve fibers

sensory ganglia

GANGLIA: made up of cell bodies of pseudounipolar neurons

sensory ganglia

PERIPHERAL NERVES: convey sensory impulses from somatic receptors

somatosensory/somatic afferent

PERIPHERAL NERVES: convey motor commands to the skeletal muscles

somatosensory/somatic efferent

SPINAL NERVE BRANCHES: curves ventrolaterally to supply the skin and muscles of the trunk and limbs

ventral ramus

SPINAL NERVE BRANCHES: gives rise to the somatic plexuses and intercostal nerves

ventral ramus

refers to the vertebral column opening that houses the spinal cord

vertebral canal

refers to the structure that houses the spinal cord and the numerous openings on both sides

vertebral column

PERIPHERAL NERVES: convey motor commands to heart muscles, smooth muscles, and glands

visceromotor/visceral efferent

PERIPHERAL NERVES: convey sensory impulses from visceral receptors

viscerosensory/visceral afferent

this law that considers the function of spinal nerve root fibers

Law of Bell and Magendie

TRUE OR FALSE: Spinal nerves commence as nerve roots in the spinal cord, with dorsal roots associated with sensory dorsal root ganglion, and ventral roots.

TRUE

TRUE OR FALSE: The inner white matter divisions of the spinal cord have dorsal horn which are sensory in function, intermediate zone which are autonomic or visceral, and ventral horn which are motor in function.

TRUE

TRUE OR FALSE: The white ramus conveys preganglionic sympathetic efferent B nerve fibers, whereas the gray ramus convey postganglionic unmyelinated C fibers.

TRUE

TRUE OR FALSE: Vertebral canal is formed by multiple vertebral foramen present in a stack, while intervertebral foramen is formed by the superior and inferior notches of adjacent vertebrae.

TRUE

IDENTIFY: Structures that Surround the Following: a. nerve trunk b. fascicle c. axon

a. epineurium b. perineurium c. endoneurium

UNMYELINATED NERVE FIBERS a. axon size b. axon: schwann cell ratio c. conduction mode d. conduction velocity e. histogram

a. greater than or equal to 1 micrometer in diameter b. > 1:1 c. continuous d. 0.5 - 2.5 m/sec (slow) e. unimodal distribution

A GAMMA FIBERS a. fiber type b. motor function c. sensory function d. receptors involved e. autonomic function

a. not sensory b. intrafusal skeletal muscle (GSE) c. none d. none e. none

B FIBERS a. fiber type b. motor function c. sensory function d. receptors involved e. autonomic function

a. not sensory b. none c. none d. none e. preganglionic autonomic efferent (GVE)

SACRAL PLEXUS a. formation b. areas supplied c. significant derivatives

a. ventral rami of spinal nerve S1-S4 + L4-L5 lumbosacral trunk b. limbs and muscles of distal lower limbs; perineum c. sciatic nerve, pudendal nerve, pelvic-splanchnic nerve

CERVICAL PLEXUS a. formation b. areas supplied c. significant derivatives

a. ventral rami of spinal nerves C1-C4 b. skin, muscles of neck, diaphragm c. phrenic nerve

ENUMERATE: Vertebrae

- 7 cervical - 12 thoracic - 5 lumbar - 5 sacral - 4 coccygeal

ENUMERATE: 31 pairs of Spinal Nerves (with #)

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

ENUMERATE: Fiber type Classifications of Large Myelinated fibers

- A alpha - A beta

ENUMERATE: Fiber type Classifications of Small Myelinated fibers

- A gamma - A delta - B

ENUMERATE: Fiber type Classifications of Unmyelinated fibers

- C

ENUMERATE: Functional Components Peripheral Nerves of Spinal Nerves

- GSA - GVA - GSE - GVE

ENUMERATE: Functional Component Peripheral Nerves of Cranial Nerves

- GSA - GVA - GSE - GVE - SSA - SVA - SVE

ENUMERATE: Autonomic Peripheral Nerves

- GVA - GSA

GIVE THE PATHWAY: General Visceral Efferent (GVE)

- autonomic nucleus in IZ (B peripheral nerve fibers) - ventral root - spinal nerve - visceral organs or autonomic ganglion then visceral organs (C fibers)

ENUMERATE: Anatomical classification of Peripheral Nerves

- cranial - spinal

ENUMERATE: three divisions of inner gray matter

- dorsal horn (DH) - intermediate zone (IZ) - ventral horn (VH)

ENUMERATE: Possible origins of a General Somatic Afferent (GSA) fiber

- free nerve endings (FNEs) - muscle spindles - Golgi Tendon Organs - cutaneous mechanoreceptors

GIVE THE PATHWAY: General Somatic Efferent (GSE)

- motor nucleus in ventral horn (A alpha and A gamma motor) - ventral root - spinal nerve - skeletal muscles (extrafusal A alpha or intrafusal A gamma)

GIVE THE PATHWAY: General Somatic Afferent

- origin (FNE, muscle spindle, GTO, cutaneous mechanoreceptors) - spinal nerve - dorsal root ganglion - dorsal root - dorsal horn

GIVE THE PATHWAY: General Visceral Afferent (GVA)

- visceral organs (B and C fibers) - spinal nerve - dorsal root ganglion - dorsal root - dorsal horn

WHAT IS THE CORRECT ORDER: Process of Myelination 1. Cytoplasm inside plasma membrane disappears, leaving only the spiral. 2. Schwann cell rotates around the axon repeatedly in a spiral that is formed surrounding the axon. 3. Axon indents the side of a Schwann cell tries to stimulate the cell. 4. Only the cytoplasm of the outermost layer of the plasma membrane remains. 5. If the Schwann cell detects that the axon is over 1 micron, it will be attracted to the axon. 6. Schwann cell envelops the axon, thus embedding the axon into it.

3-5-6-2-1-4

TRUE OR FALSE: A myelinated peripheral nerve fiber consists of the axon with its endoneurium surrounded by its myelin sheath, while an unmyelinated fiber is surrounded only by its perineurium.

FALSE - A myelinated peripheral nerve fiber consists of the axon with its MYELIN SHEATH surrounded by its ENDONEURIUM, while an unmyelinated fiber is surrounded only by its ENDONEURIUM.

TRUE OR FALSE: All pairs of spinal nerves are mixed nerves, meaning they contain both dorsal and ventral roots, having both sensory and motor functions, except C2 which is purely dorsal and sensory.

FALSE - All pairs of spinal nerves are mixed nerves, meaning they contain both dorsal and ventral roots, having both sensory and motor functions, except C1 which is purely VENTRAL and MOTOR.

TRUE OR FALSE: Autonomic outflow refers to the outflowing impulses from CNS to visceral organs, which generally have their lowest efferent nerve cell station at the first stop in the pathway.

FALSE - Autonomic outflow refers to the outflowing impulses from CNS to visceral organs, which generally have their lowest efferent nerve cell station at the LAST stop in the pathway.

TRUE OR FALSE: Axons with diameters greater than or equal to 1 micrometer will stimulate the Schwann cell to form the myelin sheath, and thus becomes a myelinated nerve fiber, while axons with diameters less than 1 micrometer will remain unmyelinated.

FALSE - Axons with diameters GREATER THAN 1 micrometer will stimulate the Schwann cell to form the myelin sheath, and thus becomes a myelinated nerve fiber, while axons with diameters less than OR EQUAL TO 1 micrometer will remain unmyelinated.

TRUE OR FALSE: General Visceral Afferent fibers are peripheral nerve fibers going to the visceral organs from the CNS, and are composed of A beta and A gamma fibers.

FALSE - General Visceral Afferent fibers are peripheral nerve fibers going to CNS FROM THE VISCERAL ORGANS and are composed of B and C gamma fibers.

TRUE OR FALSE: Incisures of Schmidt-Lanterman are important routes for the entry of substances from the ECF into the Schwann cell for nourishment.

FALSE - Incisures of Schmidt-Lanterman are important routes for the entry of substances from the SCHWANN CELL into the NERVE FIBER OR AXON for nourishment.

TRUE OR FALSE: Jumping of electrical impulse conductions from node to node allows fast conduction velocity through continuous conduction.

FALSE - Jumping of electrical impulse conductions from node to node allows fast conduction velocity through SALTATORY conduction.

TRUE OR FALSE: Large myelinated nerve fibers are greater than or equal to 8 micrometers in diameter, while small myelinated nerve fibers are less than 8 micrometers and are greater than 1 micrometer.

FALSE - Large myelinated nerve fibers are GREATER THAN 8 micrometers in diameter, while small myelinated nerve fibers are less than OR EQUAL TO 8 micrometers and are greater than 1 micrometer.

TRUE OR FALSE: Peripheral nerves are protected by epithelial tissue sheaths or coverings.

FALSE - Peripheral nerves are protected by CONNECTIVE tissue sheaths or coverings.

TRUE OR FALSE: The dorsal nerve root of a spinal cord contain all fiber types.

FALSE - The dorsal nerve root of a spinal cord contain all fiber types EXCEPT A GAMMA FIBERS.

TRUE OR FALSE: The occurrence of the blood-nerve barrier is a function of the epineurium.

FALSE - The occurrence of the blood-nerve barrier is a function of the PERINEURIUM.

refers to the myelin forming unit of the peripheral nervous system

Schwann cell or neurolemmocyte

TRUE OR FALSE: As the perineurium lacks resistance to compressions, compression neuropathies may develop, such as Carpal Tunnel Syndrome.

TRUE

TRUE OR FALSE: Dorsal root fibers are sensory and afferent, while ventral root fibers are motor and efferent.

TRUE

MYELINATED NERVE FIBERS a. axon size b. axon: schwann cell ratio c. conduction mode d. conduction velocity e. histogram

a. >1-20 micrometer b. 1 internode : 1; 1 axon : >1 c. saltatory d. 12-120 m/sec (fast) e. bimodal distribution

A ALPHA FIBERS a. fiber type b. motor function c. sensory function d. receptors involved e. autonomic function

a. IA afferents; IB afferents b. extrafusal skeletal muscle (GSE) c. proprioception d. muscle spindle annulospiral endings; golgi tendon organs e. none

A BETA FIBERS a. fiber type b. motor function c. sensory function d. receptors involved e. autonomic function

a. II afferents b. none c. proprioception (GSA); fine touch and vibration (GSA) d. muscle spindle flower spray endings; cutaneous mechanoreceptors e. none

A DELTA FIBERS a. fiber type b. motor function c. sensory function d receptors involved e. autonomic function

a. III afferents b. none c. fast pain (GSA) d. free nerve endings (FNEs) e. none

C FIBERS a. fiber type b. motor function c. sensory function d. receptors involved e. autonomic function

a. IV afferents b. none c. slow pain (GSA) d. free nerve endings e. postganglionic autonomic efferent (GVE)

WHICH IS NOT TRUE: Autonomic Ganglia a. Synapse between preganglionic and postganglionic autonomic efferent fibers. b. Lowest nerve cell station of an autonomic outflow is the autonomic nucleus in the CNS. c. Axon becomes post-ganglionic autonomic which ends up on the visceral effector, with cell body lying on the autonomic ganglion. d. Preganglionic autonomic efferent fiber brings message from CNS to ganglion, with its cell body lying on the autonomic nucleus in the CNS.

b. - Lowest nerve cell station of an autonomic outflow is the autonomic GANGLION in the PNS

WHICH IS NOT TRUE: Spinal Nerves a. Spinal nerves commence as dorsal and ventral roots. b. Spinal nerve roots unite at the intervertebral foramen to form motor spinal nerves. c. Mixed spinal nerves only travel a short course as it emerges from the intervertebral foramen. d. Mixed spinal nerves further divide to form its major branches.

b. - Spinal nerve roots unite RIGHT AFTER PASSING THROUGH THE intervertebral foramen to form MIXED spinal nerves.

WHICH IS NOT TRUE: Connective Tissue Coverings of the Fiber a. a fascicle is a group of axons, and a nerve trunk is a group of fascicles b. a perineural structure would wrap around a nerve fascicle, while a perineurial structure would wrap around the nerve trunk c. nerve fascicles are not straight tubes, but are inter-weavings of nerve fascicles d. fibers may be myelinated or unmyelinated

b. - a perineural structure would wrap around a nerve TRUNK, while a perineurial structure would wrap around the nerve FASCICLE

WHICH IS NOT TRUE: Somatic Efferent Peripheral Nerve Fibers a. originate from a motor nucleus in the CNS b. axons give rise to Special Somatic Afferent Nerve fibers that go to the skeletal muscles c. has no synapses, no ganglia, and no interruptions d. its lowest efferent nerve cell station lies on the motor nucleus in the CNS

b. - axons give rise to GENERAL Somatic EFFERENT Nerve fibers that go to the skeletal muscles

WHICH IS NOT TRUE: General Somatic Efferent (GSE) Component a. peripheral nerve fibers going to skeletal muscles b. the motor nucleus in the dorsal horn is the lowest efferent nerve cell station of somatomotor outflow c. the motor nucleus consists of A alpha and A gamma motor neurons d. GSE can terminate as extrafusal A alpha fibers or intrafusal A gamma fibers

b. - the motor nucleus in the VENTRAL horn is the lowest efferent nerve cell station of somatomotor outflow

refers ti what becomes the outermost layer of the Schwann cell with the remaining cytoplasm

neurilemmal sheath of Schwann

WHICH IS NOT TRUE: Fiber Types and Effectors a. Fine touch and vibration receptors are GSAs that make use of cutaneous mechanoreceptors involved with A beta fibers. b. A gamma fibers are only GSE motor for intrafusal skeletal muscles. c. Fast pain makes use of III afferent fibers in B fibers, while slow pain makes use of IV afferent fibers using the C classifications. d. B fibers are the slowest myelinated fibers and are used by preganglionic autonomic efferent.

c. - Fast pain makes use of III afferent fibers in A DELTA, while slow pain makes use of IV afferent fibers using the C classifications.

WHICH IS NOT TRUE: Sensory Ganglia a. No synapses in the PNS, with the first synapse occurring in the CNS. b. First nerve cell station lies in the sensory ganglion. c. Synapse occurs between peripheral process of fiber and a sensory ganglion. d. Second nerve cell station lies on the sensory nucleus.

c. - Synapse occurs between CENTRAL process of fiber and a sensory NUCLEUS.

WHICH IS NOT TRUE: Sites of Exit a. The 8th cervical spinal nerve exits above the 1st thoracic vertebra. b. The 5th thoracic spinal nerve exits below the 5th thoracic vertebra. c. The 3rd lumbar spinal nerve exits between the 2nd and 3rd lumbar vertebra. d. The 4th thoracic spinal nerve exits above the 5th thoracic vertebra.

c. - The 3rd lumbar spinal nerve exits between the 3RD and 4TH lumbar vertebra.

WHICH IS NOT TRUE: Nervous System a. The CNS is connected to the organ system through the PNS. b. The CNS is comprised of the brain and spinal cord. c. The PNS is composed of the peripheral nerves, nuclei, receptors, and effectors. d. Peripheral nerves can be classified anatomically and functionally.

c. - The PNS is composed of the peripheral nerves, GANLGIA, receptors, and effectors.

WHICH IS NOT TRUE: Intervertebral Foramen a. only one intervertebral foramen will allow the exit of a particular spinal nerve b. site at which the two roots unite to form the mixed spinal nerve c. spinal nerves can be found crowding at varying intervertebral foramina d. foramina serve as the site where the spinal nerves exit the vertebral column

c. - spinal nerves CANNOT be found crowding at varying intervertebral foramina

GANGLIA: associated to somatic efferent peripheral nerve fibers

no associated ganglia

areas in between the internodes that are not surrounded by a myelin sheath

node of Ranvier

refers to the electrical impulse conduction of an unmyelinated fiber as a result of the absence of an insulative myelin sheath

continuous conduction

WHICH IS NOT TRUE: Fiber Types and Receptors a. Thicker fiber types have faster conduction velocities. b. A alpha fibers are the thickest and fastest conductors. c. Proprioception, the sense of position, is a general sensory affector related to A alpha and A beta fibers. d. Flower spray endings are the primary receptors for muscle tension, while annulospiral endings are the secondary receptors for muscle tension.

d. - ANNULOSPIRAL endings are the primary receptors for muscle LENGTH, while FLOWER-SPRAY endings are the secondary receptors for muscle LENGTH.

WHICH IS NOT TRUE: Myelination and Internodes a. One internode corresponds to only one Schwann cell. b. A Schwann cell will not myelinate any other part of the axon and not myelinate any other axon. c. Unmyelinated peripheral nerve fibers still indent side of a Schwann cell. d. An axon cannot be myelinated by more than one Schwann cell.

d. - An axon MAY be myelinated by more than one Schwann cell.

WHICH IS NOT TRUE: General Visceral Efferent (GVE) a. Autonomic nucleus is in the intermediate zone b. Axons give rise to preganglionic autonomic efferent B peripheral nerve fibers c. Can directly go into the visceral organs as preganglionic autonomic efferent fibers d. Can pass an autonomic ganglion and then to a skeletal muscle, with a B peripheral nerve fiber as its postganglionic autonomic afferent fiber

d. - Can pass an autonomic ganglion and then to a visceral organ, with a C peripheral nerve fiber as its postganglionic autonomic afferent fiber

WHICH IS NOT TRUE: Important Nerves of the Body a. The phrenic nerve supplies the diaphragm. b. The ulnar, radial, and medial nerve supply the upper limbs. c. The sciatic nerve is the largest peripheral nerve of the body. d. The pudendal nerve supplies the bladder and rectum.

d. - The PELVIC-SPLANCHNIC nerve supplies the bladder and rectum.

refers to the myelin forming unit of the Central Nervous System

oligodendrocyte

NERVE SHEATHS: forms tight junctions that act as selective barriers

perineurium

NERVE SHEATHS: provide tensile strength and flexibility to the nerve and allow stretching when extremities move

perineurium

SPINAL NERVE BRANCHES: curves dorsolaterally to supply the skin and the paraspinal muscle mass

dorsal ramus

NERVE SHEATHS: convey blood vessels that will supply nutrients to the nerve and the waste products extruded by veins

epineurium

refers to a collection of nerve cell bodies in the peripheral nerve systems

ganglia

refers to remnants of cytoplasm persisting within myelin sheath

incisures of Schmidt-Lanterman

MULTIVARIATION RELATIONSHIP: 1. axon diameter 2. myelin sheath thickness 3. internodal length 4. conduction velocity

increase in 1 leads to an increase 2, which leads to an increase in 3, which leads to an increase in 4

refers to a singular segment that is surrounded by a myelin sheath

internode

the autonomic nucleus of sympathetic outflow

interomedial cell column

location where nerve roots unite

intervertebral foramen

refers to the vertebral column opening that acts as a site of exit of the spinal nerves

intervertebral foramen

SPINAL NERVE BRANCHES: re-enters the intervertebral foramen to supply the meninges, vertebrae, and blood vessels

meningeal ramus

PERIPHERAL NERVES: functional classifications that are efferent in direction; sending signals from CNS to the effectors

motor