Part C: The Peripheral Nervous System & Reflex Activity

71問 • 1年前

Bear4

通報

問題一覧

Spinal Nerves: _____ mixed pairs named for level from Spinal Cord

Supply all body parts except head & part of neck

Spinal Nerves

8 pairs (C1–C8)

Cervical Nerves

7 cervical vertebrae give rise to 8 pairs of cervical spinal nerves because: –Each of the first 7 pairs (C1 to C7) exits the vertebral canal Superior to vertebra for which it is named –Last spinal nerve (C8) exits canal inferior to C7 •So vertebra C7 has a nerve that leaves above it & one that leaves below it

Cervical Nerves

12 pairs (T1–T12)

Thoracic Nerves

5 pairs (L1–L5)

Lumbar Nerves

5 pairs (S1–S5)

Sacral Nerves

1 pair, tiny (C0)

Coccygeal Nerves

Cauda equina

Each of the other Spinal Nerves exits _____ to vertebra for which it is named

Inferior

Each spinal nerve is connected to spinal cord via two roots

Ventral Roots & Dorsal Roots

Both ventral & dorsal roots are branched medially as _____ that then join laterally to form spinal nerve

rootlets

Contain Motor (Efferent) fibers from ventral horn; innervate skeletal muscles

Ventral Roots

Contain Sensory (Afferent) fibers from sensory neurons in Dorsal Root Ganglia that conduct impulses from peripheral receptors

Dorsal Roots

_____ emerge from Vertebral Column via their respective Intervertebral Foramina

Spinal nerves

______ are mostly quite short (~1-2 cm) become progressively longer as you progress down cord

Spinal roots

Anterior view showing spinal cord, associated nerves, and vertebrae. The dorsal and ventral roots arise medially as _____ and join laterally to form the spinal nerve.

rootlets

Lumbar & Sacral Roots are very long & extend through lower vertebral column

Cauda Equina

Almost immediately after exiting foramen, _____ divide into three branches –Dorsal Ramus –Ventral Ramus –Meningeal Branch

Spinal Nerves

smaller branch ~ yellow line

Dorsal Ramus

larger branch ~ red line

Ventral Ramus

tiny branch that reenters vertebral canal to innervate meninges & blood vessels

Meningeal Branch

contain autonomic nerve fibers that join ventral rami in thoracic region

Rami Communicantes

Spinal Nerve Rami & their main branches supply entire Somatic region of body from

neck down

supply posterior body trunk

Dorsal Rami

supply rest of trunk & limbs

Ventral Rami

______ lie medial to & form Spinal Nerves ●Each is purely Sensory or Motor

Roots

______ lie distal to & are lateral branches of Spinal Nerves ●Can carry both Sensory & Motor

Rami

All Ventral Rami (except T2–T12) form interlacing nerve networks –Found in Cervical, Brachial, Lumbar, & Sacral areas –Only Ventral Rami form plexuses

Nerve Plexuses

1.Each branch contains fibers from several different spinal nerves 2.Fibers from ventral ramus go to body periphery via several routes -Means each limb muscle is innervated by more than one spinal nerve, so damage to one does not cause paralysis

Within plexus, fibers crisscross so that

First four Ventral Rami (looping C1–C4)

Cervical Plexus

Innervate skin of neck, ear, back of head, & shoulders –Other branches innervate neck muscles

Cutaneous Nerves

_______ receives fibers from C3 to C5 –Major Motor & Sensory Nerve of Diaphragm, major muscles for breathing

Phrenic Nerve

Irritation of the _____ causes spasms of the Diaphragm: hiccups

Phrenic Nerve

•If both Phrenic Nerves are severed, or if C3–C5 region of Spinal Cord is destroyed, ______ becomes paralyzed –Respiratory arrest occurs; requires mechanical respirators to stay alive ●Air is mechanically forced into the lungs—literally breathing for them

Diaphragm

–Formed by Ventral Rami of C5–C8 & T1 (& often C4 and/or T2) –Gives rise to nerves that innervate upper limb

Brachial Plexus & Upper Limb

Innervation of Specific Body Regions Four major branches of this plexus: —Roots —Trunks —Divisions —Cords

Brachial Plexus & Upper Limb

_____ five ventral rami (C5–T1) unite to form…Trunks

Roots

______ upper, middle, & lower, which unite to form…Divisions

Trunks

_____ anterior & posterior, which unite to form ……Cords

Divisions

lateral, medial, & posterior

Cords

______ give rise to nerves of upper limb, five of most important being: -Axillary -Musculocutaneous -Median -Ulnar -Radial

Brachial Plexus

innervates Deltoid, Teres Minor, & skin & joint capsule of shoulder

Axillary

innervates Biceps Brachii & Brachialis, Coracobrachialis, & skin of lateral forearm

Musculocutaneous

innervates skin, most flexors, forearm pronators, wrist & finger flexors, thumb opposition muscles

Median

supplies Flexor Carpi Ulnaris, part of Flexor Digitorum Profundus, most intrinsic hand muscles, skin of medial aspect of hand, wrist/finger flexion

Ulnar

innervates essentially all extensor muscles, supinators, & posterior skin of limb

Radial

Injuries to ________ are common - Severe injuries can weaken or paralyze entire upper limb - Injuries may occur if upper limb is pulled too hard, stretching plexus • Ex: when football tackler yanks arm of running back • Blows to top of shoulder can force humerus inferiorly

Brachial Plexus

Injury to ________ makes it difficult to use pincer grasp (opposed thumb & index finger) to pick up small objects - Seen in Carpal Tunnel Syndrome, when _________ is compressed • Also, frequent casualty of wrist-slashing suicide attempts

Median Nerve

_______ is very vulnerable to injury –Severe or chronic damage to Ulnar Nerve can lead to sensory loss, paralysis, & muscle atrophy ●Affected individuals have trouble making a fist & gripping objects ●Little & ring fingers become hyperextended at the knuckles & flexed at distal interphalangeal joints ●Causes hand to contort into a clawhand –Striking the “funny bone,” the spot where this nerve rests against medial epicondyle, can make the little finger tingle.

Ulnar Nerve

______ trauma results in wrist drop, inability to extend the hand at the wrist –Improper use of a crutch can compress radial nerve & impair its blood supply ●“Saturday Night Paralysis”: intoxicated person falls asleep with an arm draped over the back of a chair or sofa edge, cutting off blood supply to _______

Radial Nerve

have significant overlap

Lumbar & Sacral Plexuses

Fibers of Lumbar Plexus contribute to Sacral Plexus via

Lumbosacral Trunk

_____ serves mostly lower limb, but also sends some branches to abdomen, pelvis, & buttocks

Lumbosacral Plexus

Arises from L1 to L4 ●Innervates thigh, abdominal wall, & psoas muscle

Lumbar Plexus

innervates Quadriceps & skin of anterior thigh & medial surface of leg

Femoral Nerve

passes through Obturator Foramen to innervate Adductor muscles

Obturator Nerve

L4 to S4 –Serves the buttock, lower limb, pelvic structures, & perineum

Sacral Plexus

●Longest & thickest nerve of body ●Innervates Hamstring muscles, Adductor Magnus, & most muscles in leg and foot ●Composed of two nerves: Tibial & Common Fibular

Sciatic nerve

Cervical (major nerves)

Phrenic

Brachial (major nerves)

Axillary, musculocutaneous, median, radial, ulnar

Lumbar (major nerves)

Femoral, obturator

Sacral (major nerves)

Sciatic (composed of tibial and common fibular)

When ______ are compressed, gait problems occur • Other symptoms are pain or numbness of the anterior thigh - Femoral Nerve serves prime movers that flex hip & extend knee • Damage can be caused by a herniated disc - If Obturator Nerve is impaired, person experiences pain in the medial thigh

Spinal Roots of Lumbar Plexus

stabbing pain radiating over course of the Sciatic Nerve - Injury could be caused by a fall, disc herniation, or badly placed injection - If the nerve is transected, leg is nearly useless & cannot be flexed because hamstrings are paralyzed

Sciatica

Foot & ankle cannot move at all, so foot drops into plantar flexion • Recovery is usually slow & sometimes incomplete - For lesions below knee, thigh muscles are spared - If Tibial Nerve is injured, paralyzed calf muscles cannot plantar flex foot, & a shuffling gait develops

Footdrop

–Ventral Rami of T1–T12 are Intercostal Nerves that supply muscles of ribs, anterolateral thorax, & abdominal wall –Give off cutaneous branches to skin along course –Two special Thoracic Nerves: ●Tiny T1 ●T12, which is a Subcostal Nerve

Anterolateral Thorax & Abdominal Wall

Back is innervated by _____ via several branches ●Each branch innervates a strip of muscle & skin in line with where it emerges from spinal cord

Dorsal Rami

–To remember which nerves serve which synovial joint, use: ●Hilton’s Law: Any nerve serving a muscle that produces movement at a joint also innervates that joint & skin over that joint

Innervation of Joints

Any nerve serving a muscle that produces movement at a joint also innervates that joint & skin over that joint

Hilton’s Law

area of skin innervated by cutaneous branches of single Spinal Nerve –All Spinal Nerves except C1 participate in dermatomes –Extent of Spinal Cord injuries ascertained by affected dermatomes

Dermatome

Muscles

Muscles

Muscles Lab 3

Muscles Lab 3

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問題一覧

Spinal Nerves: _____ mixed pairs named for level from Spinal Cord

Supply all body parts except head & part of neck

Spinal Nerves

8 pairs (C1–C8)

Cervical Nerves

12 pairs (T1–T12)

Thoracic Nerves

5 pairs (L1–L5)

Lumbar Nerves

5 pairs (S1–S5)

Sacral Nerves

1 pair, tiny (C0)

Coccygeal Nerves

Cauda equina

Each of the other Spinal Nerves exits _____ to vertebra for which it is named

Inferior

Each spinal nerve is connected to spinal cord via two roots

Ventral Roots & Dorsal Roots

Both ventral & dorsal roots are branched medially as _____ that then join laterally to form spinal nerve

rootlets

Contain Motor (Efferent) fibers from ventral horn; innervate skeletal muscles

Ventral Roots

Contain Sensory (Afferent) fibers from sensory neurons in Dorsal Root Ganglia that conduct impulses from peripheral receptors

Dorsal Roots

_____ emerge from Vertebral Column via their respective Intervertebral Foramina

Spinal nerves

______ are mostly quite short (~1-2 cm) become progressively longer as you progress down cord

Spinal roots

Anterior view showing spinal cord, associated nerves, and vertebrae. The dorsal and ventral roots arise medially as _____ and join laterally to form the spinal nerve.

rootlets

Lumbar & Sacral Roots are very long & extend through lower vertebral column

Cauda Equina

Almost immediately after exiting foramen, _____ divide into three branches –Dorsal Ramus –Ventral Ramus –Meningeal Branch

Spinal Nerves

smaller branch ~ yellow line

Dorsal Ramus

larger branch ~ red line

Ventral Ramus

tiny branch that reenters vertebral canal to innervate meninges & blood vessels

Meningeal Branch

contain autonomic nerve fibers that join ventral rami in thoracic region

Rami Communicantes

Spinal Nerve Rami & their main branches supply entire Somatic region of body from

neck down

supply posterior body trunk

Dorsal Rami

supply rest of trunk & limbs

Ventral Rami

______ lie medial to & form Spinal Nerves ●Each is purely Sensory or Motor

Roots

______ lie distal to & are lateral branches of Spinal Nerves ●Can carry both Sensory & Motor

Rami

All Ventral Rami (except T2–T12) form interlacing nerve networks –Found in Cervical, Brachial, Lumbar, & Sacral areas –Only Ventral Rami form plexuses

Nerve Plexuses

Within plexus, fibers crisscross so that

First four Ventral Rami (looping C1–C4)

Cervical Plexus

Innervate skin of neck, ear, back of head, & shoulders –Other branches innervate neck muscles

Cutaneous Nerves

_______ receives fibers from C3 to C5 –Major Motor & Sensory Nerve of Diaphragm, major muscles for breathing

Phrenic Nerve

Irritation of the _____ causes spasms of the Diaphragm: hiccups

Phrenic Nerve

Diaphragm

–Formed by Ventral Rami of C5–C8 & T1 (& often C4 and/or T2) –Gives rise to nerves that innervate upper limb

Brachial Plexus & Upper Limb

Innervation of Specific Body Regions Four major branches of this plexus: —Roots —Trunks —Divisions —Cords

Brachial Plexus & Upper Limb

_____ five ventral rami (C5–T1) unite to form…Trunks

Roots

______ upper, middle, & lower, which unite to form…Divisions

Trunks

_____ anterior & posterior, which unite to form ……Cords

Divisions

lateral, medial, & posterior

Cords

______ give rise to nerves of upper limb, five of most important being: -Axillary -Musculocutaneous -Median -Ulnar -Radial

Brachial Plexus

innervates Deltoid, Teres Minor, & skin & joint capsule of shoulder

Axillary

innervates Biceps Brachii & Brachialis, Coracobrachialis, & skin of lateral forearm

Musculocutaneous

innervates skin, most flexors, forearm pronators, wrist & finger flexors, thumb opposition muscles

Median

supplies Flexor Carpi Ulnaris, part of Flexor Digitorum Profundus, most intrinsic hand muscles, skin of medial aspect of hand, wrist/finger flexion

Ulnar

innervates essentially all extensor muscles, supinators, & posterior skin of limb

Radial

Brachial Plexus

Median Nerve

Ulnar Nerve

Radial Nerve

have significant overlap

Lumbar & Sacral Plexuses

Fibers of Lumbar Plexus contribute to Sacral Plexus via

Lumbosacral Trunk

_____ serves mostly lower limb, but also sends some branches to abdomen, pelvis, & buttocks

Lumbosacral Plexus

Arises from L1 to L4 ●Innervates thigh, abdominal wall, & psoas muscle

Lumbar Plexus

innervates Quadriceps & skin of anterior thigh & medial surface of leg

Femoral Nerve

passes through Obturator Foramen to innervate Adductor muscles

Obturator Nerve

L4 to S4 –Serves the buttock, lower limb, pelvic structures, & perineum

Sacral Plexus

●Longest & thickest nerve of body ●Innervates Hamstring muscles, Adductor Magnus, & most muscles in leg and foot ●Composed of two nerves: Tibial & Common Fibular

Sciatic nerve

Cervical (major nerves)

Phrenic

Brachial (major nerves)

Axillary, musculocutaneous, median, radial, ulnar

Lumbar (major nerves)

Femoral, obturator

Sacral (major nerves)

Sciatic (composed of tibial and common fibular)

Spinal Roots of Lumbar Plexus

Sciatica

Footdrop

Anterolateral Thorax & Abdominal Wall

Back is innervated by _____ via several branches ●Each branch innervates a strip of muscle & skin in line with where it emerges from spinal cord

Dorsal Rami

–To remember which nerves serve which synovial joint, use: ●Hilton’s Law: Any nerve serving a muscle that produces movement at a joint also innervates that joint & skin over that joint

Innervation of Joints

Any nerve serving a muscle that produces movement at a joint also innervates that joint & skin over that joint

Hilton’s Law

area of skin innervated by cutaneous branches of single Spinal Nerve –All Spinal Nerves except C1 participate in dermatomes –Extent of Spinal Cord injuries ascertained by affected dermatomes

Dermatome