Peripheral Nervous System

Question 1

How is the peripheral nervous system structurally organized?

Answer 1

Nerves and Ganglia

Question 2

Which ways is the PNS categorized?

Answer 2

Motor or Sensory
General (widespread) or specialized (local)
Somatic or Visceral

Question 3

Structures of the PNS

Answer 3

Sensory receptors
Nerves and Ganglia
Motor endings (axon terminals that innervate effectors)

Question 4

What are Peripheral Sensory receptors?

Answer 4

Structures that pick up sensory stimuli (outside & inside) and covert them to electrical impulses.

Question 5

Exteroceptors

Answer 5

Sensitive to stimuli arising from outside body

Question 6

Interoceptors

Answer 6

OR Visceroreceptors, from internal viscera

Question 7

Proprioceptors

Answer 7

Monitor degree of stretch in skeletal muscles, tendons, joints and ligaments

Question 8

Mechanoreceptors

Answer 8

Respond to touch, pressure, vibrations.

Question 9

Baroreceptors

Answer 9

Respond to changes in blood pressure

Question 10

Thermoreceptors

Answer 10

Respond to temperature changes

Question 11

Chemoreceptors

Answer 11

Respond to molecules tasted or smelled, and changes in blood chemistry.

Question 12

Photoreceptors

Answer 12

Respond to light

Question 13

Nociceptors

Answer 13

Respond to harmful stimuli (extreme heat & cold) that result in pain.

Question 14

What are free nerve endings?

Answer 14

Monitor most type of sensory information (touch, pain, pressure, temperature, proprioception)

Not surrounded by a capsule of connective tissue. Mostly nociceptors & thermoreceptors

Surrounded by a capsule of connective tissue (encapsulated). All mechanoreceptors.

Question 15

What are complete receptor cells?

Answer 15

Specialized epithelial cells or small neurons (taste, vision, hearing, and equilibrium)

Question 16

Cranial Nerves

Answer 16

12 pairs of nerves attach to the brain, first two to forebrain, others to brain stem.

Question 17

What can Cranial nerves carry?

Answer 17

Primarily sensory information.
Primarily motor information.
Both, Sensory & motor (mixed nerves)

They can also carry visceral sensory and visceral motor fibers.

Question 18

I- Olfactory Nerve

Answer 18

Visceral sensory: provides sense of smell.

Damage causes impaired sense of smell

Question 19

II- Optic Nerve

Answer 19

Provides vision
Not a true nerve.

Damages causes blindness in visual field, unlike PNS, it does not regenerate

Question 20

III- Oculomotor Nerve

Answer 20

Mixed nerves: Visceral and Somatic motor
Provides eye movement, opening of eyelid; pupil sphincter.

Damages causes ptosis (drooping eyelid, double vision.

Question 21

IV- Trochlear Nerve

Answer 21

Moves eye down and out

Damages causes double vision and inability to look down and out

Question 22

V- Trigeminal Nerve

Answer 22

This is the largest cranial nerve

Main sensory nerve to face (touch, pain and temperature) and muscles of mastication.

Damage produces loss of sensation & impaired chewing or can cause increased pain = trigeminal neuralgia.

Question 23

VI- Abducens Nerve

Answer 23

Moves eyes laterally (ABduction)

Damages results in inability to move eye.

Question 24

VII- Facial Nerve

Answer 24

Provides facial expressions, sense of taste on anterior 2/3’s of tongue, salivary glands and tear, nasal & palatine glands

Damages produces sagging facial muscles & disturbed sense of taste (missing sweet and salty) called Bell’s Palsy

Question 25

VII- Vestibulocochlear Nerve

Answer 25

Provides hearing & sense of balance

Damage produces deafness, dizziness, nausea, loss of balance.

Question 26

IX- Glossopharyngeal Nerve

Answer 26

Provides control over swallowing, salivation, gagging, sensations from posterior 1/3 of tongue, control of BP and respiration.

Damage results in loss of bitter & sour taste & impaired swallowing.

Question 27

X- Vagus Nerve

Answer 27

Only cranial nerve that extends beyond the neck

Provides swallowing, speech, regulation of 2/3 of GI tract

Damages causes impaired voice, swallowing and digestion.

Question 28

XI- Accessory Nerve

Answer 28

Arises from both brain and spinal cord.
Contracts upper trap muscles.

Damages causes impaired shoulder movement

Question 29

XII- Hypoglossal Nerve

Answer 29

Provides tongue movements of speech, food manipulation & swallowing.

Question 30

Spinal Nerves

Answer 30

31 pairs of spinal nerves

Question 31

Dermatome

Answer 31

Area of skin innervated by a single spinal nerve

Question 32

Dermatome map

Answer 32

Skin area supplied with sensory innervation by spinal nerves

Question 33

Posterior (dorsal( Ramus

Answer 33

Innervate deeps muscles of the trunk responsible for movements of the vertebral column and the Connective Tissue and skin near the midline of the back.

Question 34

Anterior (Ventral) Ramus

Answer 34

What they innervate depends upon which part of the spinal cord is considered.

Question 35

Nerve plexuses

Answer 35

Networks of successive anterior rami that exchange fibers ( crisscross & redistribute)

Mainly innervate the limbs. Thoracic anterior rami do not form nerve plexuses

Question 36

Brachial Plexus: Axillary Nerve

Answer 36

Motor: Innervates deltoid and teres minor

• Deltoid: Abducts arm
• Teres: Laterally rotate arm

Sensory: from skin of the lateral shoulder

Question 37

Brachial Plexus: Radial Nerve

Answer 37

Motor: Stimulates extensor muscles of arm, forearm, and hand – Triceps, supinator, brachioradialis, ECR, ECU, and some extensors of the fingers (extensor digitorum)
– Cause extension movements at elbow and wrist, thumb movements
• Sensory: From skin on posterior surface of arm and forearm, lateral 2/3 of dorsum of hand
• Damage due to compression results in crutch paralysis
• Major symptom is ‘wrist drop’
– Failure of extensors of wrist and fingers to function
– Elbow, wrist, and fingers constantly flexed

Question 38

Brachial Plexus: Musculocutaneous Nerve

Answer 38

• Motor: Stimulates flexors in anterior arm: (biceps brachii, brachialis)
– Causes flexion movements at shoulder and elbow
• Sensory: From skin along lateral surface of forearm