1. Peripheral Nervous System
Nerves outside the brain

2. Peripheral Nervous System
Structures
Sensory receptors
Mechanoreceptors (touch, pressure, vibration, and stretch)
Thermoreceptors (temperature changes)
Photoreceptors (light energy)
Chemoreceptors (chemicals in solution)
Nerves (cranial and spinal)
Cordlike organ that is part of the PNS
Consists of parallel bundles of peripheral axons enclosed by connective tissue wrappings
Ganglia
Collections of neuron cell bodies associated with nerves in the PNS
Efferent motor endings

3. Peripheral Nervous System
12 cranial nerves
Associated with the brain
We need to learn their:
Names
Locations
Functions
31 spinal nerves
Associated with the spinal cord
Plexus

4. Cranial Nerves 10 of 12 cranial nerves attach to the brain stem
Their name reflects their function or the major structures they control
Numbered (Roman numerals) in order from anterior to posterior
Described by name, Roman numeral, and function
Function can be purely sensory, motor, or both

5. Cranial Nerves I Olfactory nerve (sensory) smell
II Optic nerve (sensory)
vision
III Oculomotor nerve (motor)
eye muscles
IV Trochlear (motor)
V Trigeminal nerve (sensory/motor)
sensory for face
motor for chewing
VI Abducens nerve (motor)

6. Cranial Nerves VII Facial nerve (sensory/motor) sensory for taste
Motor for facial expression
VIII Vestibulococchlear nerve (sensory)
balance and hearing
IX Glossopharyngeal nerve (sensory/motor)
motor for pharynx
X Vagus nerves (sensory/motor)
pharynx, larynx, and viscera
XI Accessory nerve (motor)
neck and upper back
XII Hypoglossal nerve (motor)
tongue

7. Cranial Nerves Here are mnemonic devices for the 12 cranial nerves:
On occasion our trusty truck acts funny – very good vehicle anyhow
On old Olympus' towering tops, a fin and German viewed some hops.
Olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulococchlear, glossopharyngeal, vagus, hypoglossal

8. Cranial Nerves
Cranial nerves can have sensory only, motor only, or mixed functions
Sensory only
Olfactory and optic are sensory only
Motor only
Oculomotor
Trochlear
Abducens
Accessory
Hypoglossal
Mixed (sensory and motor)
Trigeminal
Facial
Vestibulococchlear
Glossopharyngeal
Vagus
Mnemonic device to help:
Some say marry money but my brother says big butts matter more.
Some Scientists Make Money But My Brother Says Beautiful Blonds Make More

10. Olfactory (I) Sensory Smell Imbalance: fracture of ethmoid bone or lesions may result in partial or total loss of smell
Optic (II) Sensory
Vision
Imbalance: damage to optic nerve results in blindness in eye served by nerve; damage beyond optic chiasm results in partial vision loss

12. Eye and peripheral vision
Oculomotor (III) Motor Eye and pupil movement Imbalance: eye cannot move up, down or inward; at rest eye rotates laterally and trouble focusing on close objects
Trochlear (IV) Motor
Eye and peripheral vision
Imbalance: Trauma or paralysis results in double vision and reduced ability to rotate eye inferolaterally

13. Trigeminal (V) Both (sensory and motor)
Ophthalmic division (s)
Maxillary division (s)
Mandibular division (s & m)
Largest of the cranial nerves
Imbalance: trigeminal neuralgia – caused by inflammation of the nerve, stabbing pain that lasts for a few seconds to a minute, provoked by a sensory stimulus
Abducens (VI) Motor
Abduction of eye
Imbalance: eye cannot be moved laterally; at rest, affected eyeball rotates medially

14. Facial Nerves (VII) Both (sensory and motor) Muscles of facial expression: temporal, zygomatic, buccal, mandibular, cervical (m) Taste buds (anterior) (s) Imbalance: Bell’s Palsy – paralysis of facial muscles on affected side and partial loss of taste sensation; Lower eyelid droops, corner of mouth sags, tears drip continuously from eye and eye cannot be completely closed

15. Vestibulocochlear (VIII) Sensory
Hearing (cochlear)
Equilibrium (vestibular)
Imbalance: lesions of cochlear nerve result in nerve deafness; damage to vestibular produces dizziness, rapid involuntary eye movement, loss of balance, nausea and vomiting
Glossopharyngeal (IX) Both (sensory and motor)
Pharynx (throat)(m)
Taste buds and throat (posterior) (s)
Imbalance: injury impairs swallowing and taste

16. Vagus (X) Only cranial nerve to extend beyond head and neck
Both (sensory and motor)
Pharynx, larynx, heart, lungs, and abdominal organs (m)
Thoracic and abdominal organs (s)
Imbalance: Injury can lead to hoarseness or loss of voice, difficulty swallowing and impaired digestive system motility
Total destruction of nerves is incompatible with life because they are needed to maintain normal activity

17. Hypoglossal (XII) Motor
Accessory (XI) Motor
Trapezius and sternocleidomastoid
Hypoglossal (XII) Motor
Glossal = tongue
Muscles of the tongue
Imbalance: difficulty in speech and swallowing

21. Spinal Nerves
Spinal nerves are named for the region from which they arise
A pair of spinal nerves at each vertebrae for a total of 31 pairs
8 pairs of cervical (1 extra)
12 pairs of thoracic
5 pairs of lumbar
5 pairs of sacral
1 pair of coccyx

22. Spinal Nerves All are mixed nerves (sensory and motor)
Each nerve connects to the spinal cord by a dorsal and ventral root
Ventral root – motor
Dorsal root – sensory

23. Spinal Nerves The spinal nerve is actually short (1-2 cm)
Immediately it divides into its ramus (branch)
Dorsal rami – serve the skin and muscles of the posterior trunk
Ventral rami – forms a complex of networks for the anterior and limbs called plexuses

24. Plexuses
All ventral rami (except thoracic) branch and join one another lateral to the vertebral column that form a complex network called a plexus
Nerve plexuses occur in cervical, brachial, lumbar and sacral regions to serve the motor and sensory needs of the limbs
The fibers diverge again from the plexuses to form the peripheral nerves

25. Examples of Nerve Distribution
Figure 7.23

26. Spinal Nerve Plexuses PLEXUS SPINAL ROOTS (ORIGIN) BODY AREA SERVED
IMBALANCE
Cervical
C1-C5
Skin of neck, shoulder and clavicle region
Diaphragm (phrenic nerve) and muscles of shoulder and neck
Irritation of the phrenic nerve causes spasms of the diaphragm - hiccups
Brachial
C5– C8 and T1
All nerves that innervate upper limb
Arm muscles – deltoid, triceps, biceps, flexor, extensor, wrist and hands
Cutaneous sensation of the upper limb
Weakness or paralysis of entire upper limb
Carpal tunnel syndrome the median nerve is compressed
“The funny bone” results from an injury to the ulnar nerve

27. Spinal Nerve Plexuses PLEXUS SPINAL ROOTS (ORIGIN) BODY AREA SERVED
IMBALANCE
Lumbar
L1– L4
Innervation of lower limb and abdomen
Muscles of the thigh, leg and foot
Cutaneous sensation of thigh, leg, foot, external genitalia and lower abdomen
Compression of the spinal roots of the lumbar plexus results in walking problems
Sacral
L4 – S4
Innervation of the buttock, pelvic structures and lower limb
Sciatic nerve is the thickest and longest nerve in the body –entire lower limb
Muscles of the posterior surface of buttock, thigh, leg and foot,
Cutaneous sensation of posterior surface of buttock, thigh, leg and foot,
Sciatica – stabbing pain over the course of the nerve from injury to sciatic nerve such as disc herniation or improper injection in the buttock

28. Reflexes

29. The Reflex
Anyone who has had a routine physical examination is familiar with the reflex tests done to assess neural function.
A tap with a reflex hammer stretches your quadriceps tendon and your anterior thigh muscles contract, which results in the knee-jerk response
This response shows that the spinal cord and upper brain centers are functioning normally
Abnormal reflex test responses may indicate such serious disorders as intracranial hemorrhage, multiple sclerosis, or hydrocephalus

30. Reflex Arc Reflex Reflex arc
Rapid, predictable, involuntary motor response to stimuli
Inborn or acquired reflexes
Occur over neural pathways called reflex arcs
Reflex arc
Receptor  sensory neuron  integration center (monosynaptic or polysynaptic)  motor neuron  effector

31. Reflexes Receptor Sensory neuron Integration center Motor neuron
Site of the stimulus
Sensory neuron
Transmits afferent impulses to the CNS
Integration center
Single synapse (monosynaptic)
Multiple synapses (polysynaptic) btw the afferent
Motor neuron
Conducts efferent impulses from the integration center to an effector organ
Effector
Muscle fiber or gland cell that responds to the impulses

32. Reflex Arcs Monosynaptic reflex arc – knee-jerk reflex
Polysynaptic reflex arc – most reflexes

33. Types of Reflexes Somatic reflexes
Any reflex in which the skeletal muscles are the effectors
Stretch reflexes
Maintain posture, balance and locomotion
Produced by tapping a tendon, which stretches the attached muscle
Knee-jerk (patellar) reflex
Superficial reflexes
Gentle cutaneous stimulation
Plantar reflex tests the integrity of lower spinal cord
Corneal reflex
Gag reflex

34. Types of Reflexes Autonomic reflexes Smooth muscle regulation
Heart and blood pressure regulation
Digestive system regulation (saliva)
Elimination (excretion)
Change size of eye pupil
Sweating

35. Types of Reflexes