peripheral nervous system

peripheral

along the outside

what makes up the peripheral nervous system

all the nervous tissue structures except the brain and spinal cord

difference between central nervous system and peripheral nervous system

peripheral nervous system is not protected by bone

nerves of the peripheral nervous system

12 cranial nerves and 31 spinal nerves pairs

how long are spinal nerves

extremely short in length and course laterally for 1-5 millimeters

where do spinal nerves exit

intervertebral foramina located between each vertebral segment level

Number of cervical nerves

8 pairs (C1-C8)

how do cervical spinal nerves course?

above the numbered cranial vertebrae (except C8)

throacic nerves

12 pairs (T1-T12) and correspond to the thoracic vertebrae above it

lumbar nerves

5 pairs (L1-L5) and corresponds to the lumbar vertebrae above it

End of the spinal cord (the conus medullaris)

where sacral and coccygeal nerves emerge

sacral spinal nerves

5 pairs that emerge through the pelvic and dorsal sacral foramina and sacral hiatus of the sacrum

coccygeal spinal nerves

1 pair emerge through the sacral hiatus above the coccyx

dorsal rami

supply structures on the back
small branches that course posteriorly and innervate the deep back muscles and give cutaneous innervation to the skin of the back

ventral rami

supply structures on the front of the torso and the extremities
also give rise to the nerve plexuses that innervate the upper and lower extremities

Which rami are larger?

ventral

nerve plexus

braiding or twining together of nervous tissue

4 major plexus systems

cervical plexus, brachial plexus, lumbar plexus and sacral plexus

cervical plexus (ventral rami C1-C4)

supplies motor innervation to some muscles of the neck region
responsible for the cutaneous innervation to the skin of the neck and sides of the head

major nerves in the cervical plexus

phrenic nerve

Phrenic Nerve

innervates the diaphragm C3-C5

Brachial Plexus (ventral rami C5- T1)

supplies the musculature of the entire upper limb with the exception of the trapezius muscle (CN XI) and levator scapula (C3 and C4 spinal nerves)
also gives cutaneous innervation to the majority of the upper limb except for the skin over the upper medial portion of the arm and part of the upper shoulder
In total, gives off a total of 16 nerves (32 for right and left)

brachial plexus breakdown

roots, trunks, divisions (3 posterior, 3 anterior), cords (lateral, posterior and medial) , branches

terminal branches of brachial plexus

Musculocutaneous Nerve
Radial Nerve
Median Nerve
Ulnar Nerve

musculocutaneous nerve

formed from the ventral rami C5-C7 and is a derived from the lateral cord of the brachial plexus

innervation of the musculocutaneous nerve

anterior upper arm (coracobrachialis, biceps brachii and brachialis)

lateral antebrachial cutaneous nerve

musculocutaneous nerve as it courses lateral to the tendon of insertion of the biceps brachii muscle
supplies cutaneous innervation to the skin on the lateral forearm

median nerve

made from the ventral rami of spinal nerves C5-T1 is derived from the medial and lateral roots of the brachial plexus
courses through the medial surface of the arm within the neurovascular compartment

innervations of the median nerve

supply the majority of muscles in the anterior forearm and give cutaneous innervation to portions of the hand

what is special about the median nerve

only nerve to pass deep to the flexor retinaculum and thus lies within the carpal tunnel

potion of the hand the median nerve innervates

the lateral surface of the palm and the distal ends of digits 1, 2, 3 and the lateral half of digit 4

ulnar nerve

derived from the ventral rami of spinal nerves C8 and T1 and is a continuation of the medial cord of the brachial plexus
courses through the medial surface of the arm within the neurovascular compartment

Location of the median nerve

lies posterior to the medial epicondyle of the humerus (along the groove for the ulnar nerve) and continues distally along the medial surface of the forearm

innervation of the median nerve

supplies 1 ½ muscles in the anterior forearm and the majority of hand muscles

hand innervations of the ulnar nerve

Superficial Branch of the Ulnar Nerve innervates the skin on the medial surface of the palm and dorsum of the hand
It also innervates the distal end of digit 5 and the medial half of digit 4

carpal tunnel syndrome

results from significant compression of the ulnar nerve against the medial epicondyle

radial nerve

derived from the ventral rami of spinal nerves C5-T1 and is a continuation of the posterior cord of the brachial plexus

innervation of the radial nerve

innervate all the posterior forearm muscles

innervation to the hand radial nerve

superficial branch of the radial nerve innervates the skin on the lateral dorsal surface of the hand and lateral palmar surface of the thenar area

lumbosacral plexus (ventral rami L1-S4)

supplies muscular and cutaneous innervation to the entire lower limb

how can the lumbosacral plexus be divided?

lumbar plexus and sacral plexus

lumbar plexus (ventral rami L1- upper L4)

supplies the tissue and musculature of the anterior, medial and lateral thigh

location of lumbar plexus

the posterior wall of the abdomen within the substance of the psoas major muscle

major nerves of lumbar plexus

femoral and obturator

femoral nerve

L2, L3 and the upper division of ventral ramus L4
Macular distribution: Iliopsoas, Sartorius, Pectineus, Quadriceps Femoris

obturator nerve

Derived from the Ventral Rami of spinal nerves L2, L3 and the upper division of ventral ramus of L4
Transverses through the obturator foramen
Muscular Distribution: Gracilis , Adductor Longus, Adductor Brevis, Adductor part of Adductor Magnus

sacral plexus (Lower L4, L5- S4)

supplies tissues and musculature of the pelvis, gluteal region, posterior thigh, the entire leg and all the foot

location of sacral plexus

along the lateral walls of the pelvis, medial to the piriformis muscle

major nerves of sacral plexus

superior gluteal nerve
inferior gluteal nerve
nerve to piriformis
nerve to superior gemellus and obturator internus
nerve to inferior gemellus and quadratus femoris
pudendal nerve
posterior femoral cutaneous nerve
sciatic nerve (common fibular nerve, tibial nerve, medial and lateral plantar nerves, superficial and deep fibular nerves)

superior gluteal nerve

Originates from the lower division of the ventral ramus of L4 and the ventral rami of L5 and S1
Muscular distribution: Gluteus Medius , Gluteus Minimus, Tensor Fasciae Latae

inferior gluteal nerve

L5, S1 and S2
muscular innervation: Gluteus Maximus

Nerve to piriformis

ventral ramus of spinal nerve S2

Nerve to superior gemellus and obturator internus

ventral rami of spinal nerves L5, S1 and S2

Nerve to Inferior Gemellus and Quadratus Femoris

lower division of the ventral ramus of L4 and the ventral rami L5 and S1

pudendal nerve

ventral rami of spinal nerves S2, S3 and S4
responsible for innervating the male and female genitalia and plays a role in the sexual stimulatory response

posterior femoral cutaneous nerve

Ventral rami of spinal nerves S1, S2 and S3
Largest cutaneous nerve in the body
Provides cutaneous innervation to the skin on the posterior surface of the thigh

sciatic nerve

Largest nerve in the body
Lower division of the ventral ramus of L4 and the ventral rami of L5, S1, S2 and S3
Courses through the greater sciatic notch and enters the gluteal region inferior to the piriformis muscle

common epineurium

a connective tissue surrounding the individual nerves

nerves within the common epineurium

Tibial Nerve and Common Fibular Nerve

course of the sciatic nerve

courses distally along the posterior surface of the thigh between the adductor magnus and the long head of biceps femoris

sciatic nerve muscle innervation

Extensor Part of Adductor Magnus
Semitendinosus
Semimembranosus
Long and Short Heads of Biceps Femoris

tibial nerve muscle innervation

Gastrocnemius
Soleus
Plantaris
Tibialis Posterior
Flexor Hallucis Longus
Flexor Digitorum Longus
(posterior leg muscles)

2 divisions of the tibial nerve

Medial and Lateral Plantar Nerves

medial and lateral plantar nerves

supply the majority of the musculature on the plantar surface of the foot

branches of the common fibular nerve

bifurcates at the neck of the fibula into Superficial and Deep Fibular (Peroneal) Nerves

deep fibular nerve

courses inferiorly with the anterior tibial artery on the anterior surface of the interosseous membrane

muscular distribution of deep fibular nerve

tibialis anterior
extensor hallucis longus
extensor digitorum longus
Peroneus tertius
extensor digitorum brevis
(anterior leg)

muscular distribution of superficial fibular nerve

peroneus longus
peroneus brevis
(lateral leg)

intercostal nerves

derived from the ventral rami of spinal nerves T1- T11

innervation of intercostal nerves

intercostal muscles located between the ribs
cutaneous innervation to the skin on the lateral and anterior thoracic walls

subcostal nerves

derived from the ventral rami of spinal nerves T12

innervation of subcostal nerves

the muscles of the abdominal wall (Rectus Abdominis, Internal and External Obliques and Transversus Abdominis)
Cutaneous branches of the subcostal nerves also innervate the skin on the lateral abdominal wall

Foramina of cranial base

where cranial nerves enter and exit the cranial cavity

what kinds of neurons can cranial nerves have

motor, sensory or both

foramina of the cribriform plate

optic canal

superior orbital fissure

foramen rotundum

foramen ovale

internal accoustic meatus

jugular foramen

hypoglossal canal

Olfactory Nerve

CN 1
afferent/ sensory in nature
enters cranial cavity foramina of the cribriform plate
conveys smell by nerve endings in superior nasal mucosa

path of olfactory sense

olfactory nerve fibers "synapse" in the olfactory bulb and extend posteriorly as the olfactory tracts
olfactory nerves lead to the temporal lobes of the brain which contain the primary olfactory cortex for interpretation of smell

optic nerve

CN 11
afferent in nature
conveying sensory information to the brain for the interpretation of visual stimuli
optic canal

optic nerve path to the brain

optic nerves course posteriorly, "synapsing" on the thalamus and then continue as the optic radiations which lead to the occipital lobe of the brain (the primary visual cortex) for interpretation of the sense of sight

Oculomotor (III) Nerve

efferent in nature
innervates intrinsic and extrinsic muscles of eye movement
exits through the superior orbital fissure

extrinsic eye muscles innervated by oculomotor nerve

Medial rectus
Superior rectus
Inferior rectus
Inferior oblique

intrinsic eye muscles

involved with dilation and contraction of the iris

Trochlear Nerve (IV)

efferent in nature
exits the cranial cavity through the superior orbital fissure
extrinsic eye movement: Superior oblique

Trigeminal Nerve (CN V)

both motor and sensory nerve fibers
3 branches: Ophthalmic nerve, Maxillary nerve, Mandibular nerve

Opthalmic Nerve (V1)

exits through the superior orbital fissure
supply the lacrimal glands and give cutaneous innervation to the skin of the forehead, nose and upper eyelids.

maxillary nerve (V2)

exits the cranial cavity through the foramen rotundum
supply the superior dental plexus, lateral scalp, cheek, lower eyelid, lateral nose and upper lip

mandibular nerve (V3)

exits the cranial cavity through the foramen ovale
gives off the inferior alveolar nerve which supplies the inferior dental plexus,
Other branches supply sensation to the skin and mucosa of the cheek, the anterior 2/3 of the tongue (for general sensation) and the muscles of mastication

abducent nerve (VI)

exits the cranial cavity through the superior orbital fissure
innervates a single extrinsic muscle of eye movement: Lateral rectus

Facial Nerve (VII)

exits the cranial cavity through the internal acoustic meatus
both motor and sensory in nature
anterior 2/3 of the tongue for taste supply sensory innervation to the side of the face and motor innervation to the muscles of facial expression

Vestibulocochlear nerve (VIII)

afferent in nature
conveys sensory information for hearing and balance to the brain
enters the cranial cavity through the internal acoustic meatus

2 parts of vestibulocochlear nerve

vestibular branch and cochlear branch

vestibular branch of vestibulocochlear nerve

courses from the semicircular canals and is responsible for balance

cochlear branch of vestibulocochlear nerve

courses from the cochlea and is responsible for the sense of hearing