Nervous system (3)

What connective tissue wraps around a single nerve fiber (axon)?

Endoneurium

Which layer groups multiple axons into fascicles?

Perineurium

What binds multiple fascicles into a full nerve?

Epineurium

What type of nerve carries both sensory and motor impulses?

Mixed nerve

Which nerves carry signals toward the CNS?

Afferent (sensory) nerves

Which nerves carry signals away from the CNS?

Efferent (motor) nerves

In a myelinated fiber, what forms the myelin sheath?

A single Schwann cell wraps around one axon

In unmyelinated fibers, what is the relationship between Schwann cells and axons?

One Schwann cell envelops several axons

What structure separates segments of myelin along an axon?

Node of Ranvier

Which three cranial nerves are purely sensory?

Olfactory (I), Optic (II), Vestibulocochlear (VIII)

Which nerve is responsible for the sense of smell?

Olfactory nerve (CN I)

Which nerve carries visual information?

Optic nerve (CN II)

Which cranial nerve controls most eye movements?

Oculomotor nerve (CN III)

Which nerve innervates the superior oblique muscle of the eye?

Trochlear nerve (CN IV)

Which nerve provides sensory input from the face and motor input for chewing?

Trigeminal nerve (CN V)

Which nerve controls the lateral rectus muscle of the eye?

Abducens nerve (CN VI)

Which nerve provides motor control to facial muscles and taste sensation?

Facial nerve (CN VII)

Which nerve handles hearing and balance?

Vestibulocochlear nerve (CN VIII)

Which nerve is involved in taste and pharynx motor function?

Glossopharyngeal nerve (CN IX)

Which cranial nerve innervates the pharynx, larynx, and viscera?

Vagus nerve (CN X)

Which nerve controls muscles of the neck and upper back?

Accessory nerve (CN XI)

Which nerve provides motor control to the tongue?

Hypoglossal nerve (CN XII)

What is a “segment of the spinal cord”?

A section from which a pair of spinal nerves exits (one left, one right)

How many spinal cord segments are there?

31

What supplies the body wall (torso)?

Individual spinal nerves

What are the skin and muscle regions supplied by spinal nerves called?

Dermatomes and myotomes

How are the limbs innervated?

Through nerve plexuses formed by spinal nerves

What is a nerve plexus?

A network of interwoven anterior rami of spinal nerves

Which type of plexus serves the limbs and body wall?

Principal (somatic) plexuses

What type of plexus supplies internal organs?

Autonomic plexuses

Which plexus innervates the upper limb?

Brachial plexus

What type of signal does the anterior (ventral) root carry?

Motor (efferent)

What type of signal does the posterior (dorsal) root carry?

Sensory (afferent)

What do the anterior and posterior roots combine to form?

A mixed spinal nerve

Where is the dorsal root ganglion located?

On the posterior root

What does the dorsal root ganglion contain?

Cell bodies of sensory neurons

Where does the spinal nerve exit the vertebral column?

Intervertebral foramen

Which ramus innervates the back muscles and skin?

Posterior (dorsal) ramus

Which ramus is larger and goes to limbs and the anterior/lateral trunk?

Anterior (ventral) ramus

What do anterior rami form?

Plexuses

What do rami communicantes connect to?

Sympathetic trunk

Where are rami communicantes found?

T1–L2 spinal segments only

What fibers do rami communicants carry?

Visceral motor and visceral sensory

What is a dermatome?

A segment of skin supplied by a single spinal nerve

Which spinal nerve does not innervate a dermatome?

C1

What does a dermatome map show?

Sensory segments of skin across the body

How many spinal nerves contribute to dermatomes?

All except C1

What is referred pain?

Visceral pain perceived in a superficial body region

Why does referred pain occur?

Somatic and visceral nerves converge on the same spinal neuron

Pain from a heart problem is often felt where?

Left arm

What type of nerve supplies the referred region?

Somatic nerve