1. HUMAN ANATOMY LECTURE TWELVE PERIPHERAL NERVOUS SYSTEM

2. PNS consists of all the neuron cell bodies and process located outside the brain and spinal cord Collects info from sources inside and on the surface of the body Relays info by way of afferent fibers to the CNS Efferent fibers relay info from CNS to muscles and glands Divided into two parts: - 12 pairs of cranial nerves - 31 pairs of spinal nerves

3. PERIPHERAL NERVE STRUCTURE Consists of: - dendrites - cell bodies - axon bundles - Schwann cells - connective tissue ENDONEURIUM - surrounds individual neurons PERINEURIUM - surrounds axon groups to form fascicles EPINEURIUM - surrounds the entire nerve fibre

4. CRANIAL NERVES Indicated by: - Roman numerals I – XII from anterior to posterior - names May have one or more of three functions: - sensory (special or general) - somatic motor (control of skeletal muscle) - parasympathetic (regulation of glands, smooth muscles, cardiac muscle)

5. Olfactory Nerves (I) - sensory Specialized receptors for smell found in roof of nasal cavity Axons pass through cribform plate of ethmoid bone to the olfactory bulbs Attach directly to cerebrum (others attach to brain stem)

6. Optic Nerves (II) - sensory Carry visual info from special ganglia in eyes Pass through optic canals of sphenoid bone, at optic chiasm they cross and move toward opposite sides of the brain (occipital lobe)

7. Oculomotor Nerves (III) - motor and parasympathetic Each nerve innervates four of six extra-ocular muscles that move the eye and raise the upper eyelid Also controls intrinsic eye muscles that change the diameter of the pupil (adjust amount of light entering) and change shape of lens

8. Trochlear Nerves (IV) - motor Innervates superior oblique eye muscles - eye movement up/down

9. Trigeminal Nerves (V) – sensory and motor Sensation to face Innervates muscles of mastication

10. Abducens Nerves (VI) - motor Innervates 6 th pair of eye muscles - make eye move to side

11. Facial Nerves (VII) – sensory, motor, parasympathetic Deep pressure sensations of face and taste information from receptors in the tongue Innervate muscles of scalp, face and near ear Parasympathetic to salivary glands, lacrimal glands, and glands of nasal cavity

12. Vestibulocochlear Nerves (VIII) - sensory Receives sensory receptors from inner ear Concerned with balance sensations, equilibrium, hearing

13. Glossopharyngeal Nerves (IX) – sensory, motor, parasympathetic Sensory responses to tongue, pharynx, and palate Motor responses control swallowing

14. Vagus Nerves (X) – sensory, motor, parasympathetic Sensory information from acoustic canal, diaphragm, pharyngeal taste receptors, also along esophagus, respiratory tract and abdominal viscera (as far away as large intestine) Motor functions affect the heart, stomach, intestines, gall bladder

15. Accessory Nerves (XI) - motor Voluntary swallowing muscles of soft palate and pharynx Control vocal cords Also innervates muscles of neck and back

16. Hypoglossal Nerves (XII) - motor Innervates skeletal muscles of tongue - controls voluntary movements

18. SPINAL NERVES 31 pairs of mixed (sensory and motor) nerves First pair exit vertebral column between skull and atlas Last four exit via sacral foramina Others exit through intervertebral foramina 8 pair-cervical, 12 pair-thoracic, 5 pair-lumbar, 5 pair-sacral, 1 pair-coccygeal Most organized into 3 PLEXUS - where nerves come together and then separate (cervical plexus, brachial plexus, lumbosacral plexus)

19. DERMATOMAL MAP Spinal nerves indicated by capital letter and number DERMATOMAL MAP - skin area supplied with sensory innervation by spinal nervers

20. DISTRIBUTION OF SPINAL NERVES Each nerve has a dorsal and ventral RAMUS (branch) DORSAL RAMUS – around the back sensory and motor neurons that innervate deep muscles of the trunk VENTRAL RAMUS – around the front Innervation depends upon which part of the spinal cord they leave from Cervical plexus – C1-C4 Brachial plexus – C5-T1 Lumbar plexus – T1-L4 Sacral plexus – L4-L5 Cooccygeal plexus – S4-S5

21. PLEXUS (braid) Spinal nerves are organized into one of three plexuses - where nerves come together and then separate (all except T2 - T11 which extend around the thorax between the ribs to innervate intercostal muscles) Cervical Plexus (C1-C5) Innervates superficial neck structures, skin of neck, posterior portion of head PHRENIC NERVE C3-C5 innervates diaphragm

22. Brachial Plexus (C5-T1) Innervates pectoral girdle and upper arm Five rami divide into 3 trunks that further separate into 6 cords that branch off into 5 specific nerves: - axillary nerve - radial nerve - musculocutaneous nerve - median nerve - ulnar nerve

23. AXILLARY NERVE C5, C6 Muscle innervation: Laterally rotates arm - teres minor Adducts arm - deltoid Skin Innervation: Inferior lateral shoulder

24. RADIAL NERVE C5-T1 Muscle Innervation: Muscles located in posterior of arm Movements at elbow, wrist and thumb Skin Innervation: Posterior surface of arm and forearm, lateral 2/3 on back of hand

25. MUSCULOCUTANEOUS NERVE C5-T1 Muscle Innervation: Muscles located at anterior of arm Movements at shoulder, elbow and wrist Skin Innervation: Lateral surface of forearm

26. ULNAR NERVE C8-T1 Muscle Innervation: Two anterior forearm muscles and most of hand muscles Movements at wrist, fingers, and hand Skin Innervation: Medial 1/3 of hand, little finger, medial1/2 of ring finger

27. MEDIAN NERVE C6-T1 Muscle Innervation: Anterior forearm muscle and some hand muscles Movements of wrist, hand, fingers, thumb Skin Innervation: Lateral 2/3 palm, thumb index and middle fingers, lateral ½ of ring finger and dorsal tips of same fingers

28. Thoracic Region T1-T12 THORACIC NERVES - not organized into a plexus Muscle Innervation: Intercostal muscles Skin Innervation: Thoracic dermatomes

29. Lumbosacral Plexus Originates from nerves of the lumbar plexus (L1-L4) - obturator nerve - femoral nerve - saphenous branch Also nerves from the sacral plexus (L4-S4) - tibial nerve - peroneal nerve

30. OBTURATOR NERVE L2-L4 Muscle Innervation: Muscles of medial thigh Adduction of the thigh and knee Skin Innervation: Superior middle side of thigh

31. FEMORAL NERVE L2-L4 Muscle Innervation: Anterior thigh muscles Movements of hip, knee, sartorius, quadriceps femoris Skin Innervation: Anterior and lateral thigh, medial leg and foot

32. SAPHENOUS BRANCH Branches off fermoral nerve Muscle Innervation: Anterior and medial thigh Skin Innervation: Anterior and medial thigh, medial leg

33. TIBIAL NERVE Together with peroneal nerve make up SCIATIC NERVE L4-S3 Muscle Innervation: Posterior thigh muscles, anterior and posterior leg muscles Movement of hip, knee, foot, toes Skin Innervation: Sole of foot

34. PERONEAL NERVE (COMMON FIBULAR) L4-S3 Muscle Innervation: Muscles of lateral thigh and leg, some foot muscles Skin Innervation: Lateral, anterior leg and sole of foot

35. Coccygeal Plexus S4-S5 Muscles of pelvic floor Sensory info from skin over coccyx

36. PNS DISORDERS General Disorders: Anesthesia - loss of sensation Hyperesthesia - increased sensitivity to pain, pressure, light Paesthesia - tingling, prickling, burning Neuralgia - nerve inflammation causing stabbing pain Sciatica - pain radiating down back of thigh and leg Infections: Herpes - skin lesions Shingles (herpes zoster) - adult chickenpox Poliomyelitis - infantile paralysis Anesthetic leprosy - bacterial infection of peripheral nerves Genetic and Autoimmune Disorders: Myasthenia gravis - results in fatigue and muscular weakness due to inadequate ACh receptors