cranial nerves and spinal cord

lecture 9

Name the cranial nerves and their Roman

numeral.

There are 12 pairs of cranial nerves, numbered with

Roman numerals. Make sure you know the NAME

AND the Roman numerals!

I Olfactory

II Optic

III Occulomotor

IV Trochlear

V Trigeminal

VI Abducens

VII Facial

VIII Vestibulocochlear

IX Glossopharyngeal

X Vagus

XI Accessory Nerve

XII Hypoglossal

What is Cranial Nerve I called, and what does it

do?

OLFACTORY nerves

Transmits the sense of smell

Scientists who are trying to find a way to make

neurons divide to heal nerve injuries often study

the body’s only mitotic neurons. These neurons

are the

olfactory receptors

What is Cranial Nerve II called, and what does it

do?

II. OPTIC NERVE: Transmits visual information

from the eye’s retina.

What is Cranial Nerve III called, and what does

it do?

III Occulomotor Nerve: this controls most of the

extrinsic muscles of the eye (that move the eyeball).

They also have parasympathetic innervation in the

iris (pupil) and cilliary (controls the lens)

What is Cranial Nerve IV called, and what does

it do?

IV. Trochlear Nerve: supplies one of the extrinsic

eye muscles

What is Cranial Nerve V called, and what does it

do?

V. Trigeminal Nerve: This is the main sensory nerve

of the face.

What hole does Cranial Nerve V pass through in

the skull?

It has a large branch that passes through the foramen

ovale of the skull.

Irritation of CN V is called what?

Problems with CN-V are called TRIGEMINAL

NEURALGIA, which is excruciating pain in the face

from nerve inflammation

What is Cranial Nerve VI called, and what does

it do?

VI: Abducens controls one of the eye muscles

(lateral rectus).

What is Cranial Nerve VII called, and what does

it do?

VII Facial Nerve: This innervates the muscles of

facial expression and salivary glands.

A person who cannot blink or smile may have

damage to what nerve?

VII Facial Nerve

A person who cannot easily taste sweet, sour, or

salty substances has damage to what nerve?

A person who cannot easily taste sweet, sour, or

salty substances has damage to what nerve? VII

Facial Nerve

The primary gustatory (taste) cortex is located in

which lobe of the brain?

Temporal lobe (in the insula)

Bell’s Palsy is damage to what nerve? What

other disorder does it look like?

BELL’S PALSY is damage of the facial nerve Needs

to be distinguished from a stroke.

What is Cranial Nerve VIII called, and what does

it do?

VIII. VESTIBULOCOCHLEAR nerve transmits

hearing and balance.

What is Cranial Nerve IX called, and what three

things does it do?

IX: GLOSSOPHARYNGEAL

 signals the pharynx to constrict (along with X)

during swallowing.

 Innervates top of tongue

 Carries information from baroreceptors

What is Cranial Nerve X called, and what four

things does it do?

X Vagus Nerve

 Parasympathetic supply to organs

 Moves the larynx during speech

 Signals pharynx to constrict during swallowing

(with CN IX)

 Carries information from baroreceptors

Which cranial nerve travels into the abdomen?

X Vagus Nerve

The majority of all parasympathetic fibers are

from what cranial nerve?

X Vagus Nerve

What is Cranial Nerve XI called, and what does

it do?

XI: ACCESSORY NERVE enters the skull through

foramen magnum and leaves through the jugular

foramen. It just supplies the shoulder muscles.

What is Cranial Nerve XII called, and what does

it do?

XII. HYPOGLOSSAL NERVE (hypo=under;

glossal=tongue) - supplies the under surface of the

tongue.

What does damage to Cranial Nerve XII cause?

Damage causes impairment of speech.

Where does spinal cord begin and end?

FORAMEN MAGNUM. It goes to L1-2.

In infants, it ends at L4-5, because it doesn’t grow as

fast as the rest of the body.

What is the spinal cord called beyond L1-2?

CAUDA EQUINA (“Horse’s tail”), which exit

through the intervertebral foramina.

Where does the SACRAL PLEXUS exit the

spinal cord?

The SACRAL PLEXUS is made up of the spinal

nerves exiting the spinal cord from the level of L4 to

S5.

What spinal nerve has a number that does not

correspond to a vertebra?

There is a spinal nerve C8, although there is no C8

vertebrae.

CROSS SECTION OF THE SPINAL CORD

Define a GANGLION (plural is ganglia)

Ganglion = a group of neuron cell bodies.

Are they motor or sensory?

Some are motor, some are sensory

Are they in the CNS, PNS, or both?

All ganglia are in the PNS only

Where are the cell bodies of the sensory neurons

of the spinal nerves located?

Posterior root ganglion

Most synapses are in what part of the nervous

system?

Most synapses are in the CNS

34. Define SENSORY NEURONS:

35. Where do they come in to the spinal cord?

36. Where is their cell body

37. Where do they synapse

38. What pathway do they take to the brain

39. In what part of the brain do they terminate?

SENSORY NEURONS come in through the

posterior root, their cell body is in the posterior root

ganglion, and its axon goes into the posterior horn

and synapses in the grey matter.

It also sends a branch to an area of the white matter

called the DORSAL COLUMN PATHWAY, which

goes into the brain (thalamus).

Axons in the DORSAL COLUMN PATHWAY

go to what part of the brain?

Thalamus

Regarding LOWER MOTOR NEURONS:

41. Where is their cell body

42. Where does their axon exit the spinal cord

43. Where do they synapse

LMN’s have their cell body in the anterior horn (of

the gray matter), and their axon goes out the anterior

root, and synapses in a muscle

Where are the cell bodies of interneurons?

Their cell bodies are in the dorsal half of the gray

matter in the spinal cord.

Where do interneurons synapse?

on the cell body of the motor neuron

What is another name for interneurons?

association neurons

The complexity of the CNS can be attributed to

what?

The complexity of the CNS can be attributed to

Interneurons

Where is the site of neuronal integration?

Grey matter

What is the correct path of a simple spinal

reflex?

Receptor, afferent neuron, integration center, efferent

neuron, effector

What types of sensory information are conveyed

toward the brain in the spinothalamic tracts?

Pain and temperature

What region of the brain interprets signals for

touch and temperature?

Somatosensory association area

What are the 3 nerves that form a simple reflex

arc?

Sensory, lower motor, and interneuron forms the

SIMPLE REFLEX ARC.

Example of a withdrawal reflex

Simple reflex behavior involves how many nerves?

Any brain involvement?

Are the automatic or voluntary events?

If you touch a hot stove, the sensory input comes

into the spinal cord, the association neurons send the

information to the lower motor neurons, the muscle

contracts, and you take your hand off the stove

before your brain even knows it.

Simple reflex behavior involves three nerves, and no brain involvement. Reflexes are automatic events.

57. Define reflexes:

58. Are they motor, sensory, or both

59. Are they fast or slow

60. Are they voluntary or involuntary

61. Do they involve one or multiple synapses

They involve both motor and sensory neurons, they

are rapid, involuntary, and they involve multiple

synapses.

What is an example of a three-neuron reflex?

KNEE-JERK REFLEX

How does a sensory signal get from a finger to

the brain?

SENSORY TOUCH  SPINAL NERVE 

POSTERIOR ROOT GANGLION  POSTERIOR

ROOT  POSTERIOR HORN  TRACT 

THALAMUS

What is the difference between a nerve and a

tract?

Inside the brain nerves are called tracts; outside the

brain, they are called nerves (for example, optic and

olfactory nerves are outside the CNS, while optic

and olfactory tracts are inside the CNS)

WHAT IS AN UPPER MOTOR NEURON?

What is a LOWER (SOMATIC) MOTOR

NEURON?

Upper motor neuron: cell body is in the brain,

synapses on a lower motor neuron (in the spinal

cord)

Lower motor neuron: cell body is in the spinal cord,

and synapses on skeletal muscle.

What region of the brain contains the upper

motor neurons?

Primary motor cortex

When the nerves leave the spinal cord, they

travel together in what?

Give one example

a plexus.

One of these is known as the brachial plexus (in the

armpit; innervates the muscles of the arm).

Starting at the spinal cord and preceding

laterally, the subdivisions of a plexus are in what

order?

rami, trunks, divisions, cords

What do PROPRIOCEPTION neurons sense?

the amount of force and movement in muscles and

joints

What tract do they travel in?

Proprioception nerves travel up the spinocerebellar

tract

An example of a test for proprioception is…?

Close eyes and touch finger to nose

Symptoms of an upper motor neuron disease

Cannot move extremity on their own (paralysis) but

reflexes are present

Symptoms of a lower motor neuron disease

Cannot move extremity on their own (paralysis) and

reflexes are also not present

How many spinal nerves are there?

31 Pairs

What region of the spinal cord do spinal nerves

exit?

OUTSIDE of vertebral canal

Cervical, thoracic, lumbar, and sacral

Are spinal nerves motor or sensory or both?

They are motor and sensory

What do lower motor neurons do?

Carry motor commands to the skeletal muscles