Anatomy: Cranial Nerves/Spinal Cord

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Cranial Nerves: 1-6

I. Olfactory
II. Optic
III. Occulomotor
V. Trigeminal
VI. Abducens

Cranial Nerves: 7-12

VII. Facial
VIII. Vestibulocochlear
IX. Glossopharyngeal
X. Vagus
XI. Accessory Nerve
XII. Hypoglossal

What is Cranial Nerve I called, and what does it do?

I. OLFACTORY nerves

Transmits the sense of smell.

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 it pass through in the skull?

It has a large branch that passes through the foramen ovale of the skull.

Irritation of this nerve are called what?

Problems with CN-5 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?

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

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
a) signals the pharynx to constrict (along with X) during swallowing.
b) Innervates top of tongue
c) Has baroreceptors

What is Cranial Nerve X called, and what three things does it do?

X Vagus Nerve

a) Parasympathetic supply to organs
b) Moves the larynx during speech
c) Signals pharynx to constrict during swallowing (with CN IX)

Which cranial nerve travels into the abdomen?

This is the only cranial nerve that travels into the abdomen.

The majority of all parasympathetic fibers are from what cranial nerve?

The majority of the parasympathetic outflow from the head is by the 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 this nerve 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.

Define a GANGLION (plural is ganglia)

Ganglion = a group of neuron cell bodies.
Some are motor, some are sensory.

Are they motor or sensory?

The ganglia in the dorsal root are always 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

Define SENSORY NEURONS:
Where do they come in to the spinal cord?
Where is their cell body
Where do they synapse
What pathway do they take to the brain
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

Define LOWER MOTOR NEURONS:
Where is their cell body
Where does their axon exit the spinal cord
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.

Define INTERNEURONS:
Where are their cell bodies
Where do they synapse
What is another name for them?

Their cell bodies are in the dorsal half of the gray matter in the spinal cord.

They receive signals from the sensory neuron and then synapse on the cell body of the motor neuron. In this way, the interneurons (sometimes called association neurons) transmit signals from the sensory pathways to the motor pathways.

The complexity of the CNS can be attributed to what?

The complexity of the CNS can be attributed to Interneurons

What types of sensory information are conveyed toward the brain in the spinothalamic tracts?

Pain and temperature

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.

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 how many nerves?
Any brain involvement?
Are the automatic or voluntary events

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

Define reflexes:
Are they motor, sensory, or both
Are they fast or slow
Are they voluntary or involuntary
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 called nerves (ie optic nerve and optic tract, olfactory nerve and olfactory tract)

WHAT IS AN UPPER MOTOR NEURON?

Upper motor neuron: cell body is in the brain, synapses on a lower motor neuron (in the spinal cord)

What is a LOWER (SOMATIC) MOTOR NEURON?

Lower motor neuron: cell body is in the spinal cord, and synapses on skeletal muscle.

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?
What tract do they travel in?

PROPRIOCEPTION neurons measure the amount of force and movement in muscles and joints

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 hand on own (paralysis) but reflexes work

How many spinal nerves are there?
What region of the spinal cord do they exit?
Are they motor or sensory or both?

31 Pairs, OUTSIDE of vertebral canal
Cervical, thoracic, lumbar, and sacral
They are motor and sensory

What do lower motor neurons do?

Carry motor commands to the skeletal muscles

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