Peripheral Nervous System: Spinal & Cranial Nerves

Flashcards covering spinal-nerve counts, nerve connective-tissue layers, ipsilateral concept, and detailed Q&A for all 12 cranial nerves including names, numbers, functions, and key pathologies.

How many pairs of cervical spinal nerves are there?

8 pairs

How many pairs of thoracic spinal nerves are there?

12 pairs

How many pairs of lumbar spinal nerves are there?

5 pairs

How many pairs of sacral spinal nerves are there?

5 pairs

How many pairs of coccygeal spinal nerves are there?

1 pair

Which connective-tissue layer surrounds an entire nerve?

Epineurium

Which connective-tissue layer surrounds a fascicle within a nerve?

Perineurium

Which connective-tissue layer surrounds an individual axon in a nerve?

Endoneurium

Do cranial nerves generally supply structures on the same side (ipsilateral) or opposite side (contralateral) of the body?

Ipsilateral

Cranial Nerve I is called what, and is it sensory, motor, or both?

Olfactory nerve – Sensory (smell)

Loss of smell due to damage of CN I is termed what?

Anosmia

Cranial Nerve II is called what, and is it sensory, motor, or both?

Optic nerve – Sensory (vision)

Partial or complete loss of vision from CN II damage is called?

Anopsia

Cranial Nerve III is called what, and is it sensory, motor, or both?

Oculomotor nerve – Motor

Which eye movements are primarily controlled by CN III?

Superior (up), inferior (down), and medial (toward nose)

Name the pathology where the eye drifts laterally due to CN III damage.

External strabismus ("lazy eye")

Cranial Nerve IV is called what, and is it sensory, motor, or both?

Trochlear nerve – Motor

Which single extra-ocular muscle is innervated by CN IV?

Superior oblique muscle

Damage to CN IV causes the eye to drift superomedially; what is this condition called?

Trochlear nerve palsy

Cranial Nerve V is called what, and is it sensory, motor, or both?

Trigeminal nerve – Both (mostly sensory)

List the three major sensory branches of CN V.

Ophthalmic, maxillary, mandibular

Which branch of CN V supplies motor fibers to muscles of mastication?

Mandibular branch

In dentistry, which cranial nerve is intentionally numbed for local anesthesia?

Branches of the Trigeminal nerve (CN V)

Cranial Nerve VI is called what, and is it sensory, motor, or both?

Abducens nerve – Motor

Which eye muscle is innervated by CN VI, and what movement does it produce?

Lateral rectus; moves eye laterally

Medial drifting of the eye due to CN VI damage is termed what?

Internal strabismus

Cranial Nerve VII is called what, and is it sensory, motor, or both?

Facial nerve – Both (mostly motor)

What motor function is controlled by CN VII?

Muscles of facial expression

Which portion of the tongue receives taste via CN VII?

Anterior two-thirds

Unilateral facial paralysis from CN VII damage is known as?

Bell’s palsy

Cranial Nerve VIII is called what, and is it sensory, motor, or both?

Vestibulocochlear nerve – Sensory (hearing & balance)

Damage to the cochlear branch of CN VIII produces what deficit?

Nerve deafness

Rapid, involuntary eye movements from vestibular branch damage are called?

Nystagmus

Cranial Nerve IX is called what, and is it sensory, motor, or both?

Glossopharyngeal nerve – Both

What sensory role does CN IX serve on the tongue?

Taste to posterior one-third of tongue

Impaired swallowing due to CN IX damage can lead to aspiration; what is the medical term for loss of taste?

Ageusia

Cranial Nerve X is called what, and is it sensory, motor, or both?

Vagus nerve – Both

What branch of the autonomic nervous system is carried largely by CN X to thoracic and abdominal organs?

Parasympathetic ("rest and digest")

Complete bilateral damage to CN X results in what outcome?

Fatal disruption of visceral organ function

Cranial Nerve XI is called what, and is it sensory, motor, or both?

Accessory nerve – Motor

Which two muscles are innervated by CN XI?

Sternocleidomastoid and trapezius

A drooping shoulder indicates damage to which cranial nerve?

Accessory nerve (CN XI) on the same side

Cranial Nerve XII is called what, and is it sensory, motor, or both?

Hypoglossal nerve – Motor

Deviation of the protruded tongue toward one side signals damage to which nerve, and on which side?

Hypoglossal nerve (CN XII) on the side to which the tongue deviates