LEC 9

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

I. Olfactory nerve: transmits the sense of smell

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

II. Optic nerve: transmits visual information from the retina

What are the 12 cranial nerves in order?

I Olfactory, II Optic, III Oculomotor, IV Trochlear, V Trigeminal, VI Abducens, VII Facial, VIII Vestibulocochlear, IX Glossopharyngeal, X Vagus, XI Accessory, XII Hypoglossal

What are olfactory receptors and why are they important?

They are the only mitotic neurons in the body and are studied for nerve regeneration research

What is Cranial Nerve III called and what does it do?

III. Oculomotor nerve

controls

• most EXTRINSIC eye muscles

• PUPIL / CILLARY muscle (parasympathetic)

What is Cranial Nerve IV called and what does it do?

IV. Trochlear nerve:

• supplies one extrinsic eye muscle (superior oblique)

What is Cranial Nerve V called and what does it do?

V. Trigeminal nerve: main sensory nerve of the face

What foramen does Cranial Nerve V pass through?

Foramen ovale

What is trigeminal neuralgia?

Severe facial pain caused by irritation of CN V

What is Cranial Nerve VI called and what does it do?

VI. Abducens nerve: controls lateral rectus muscle of the eye (lat rec activates when left eye looks left)

What is Cranial Nerve VII called and what does it do?

VII. Facial nerve:

facial expression

salivary glands

What nerve is responsible for blinking and smiling?

Facial nerve (CN VII)

What nerve is responsible for taste (sweet, sour, salty)?

Facial nerve (CN VII)

Where is the primary gustatory cortex located?

Insula of the temporal lobe

What is Bell’s palsy?

Facial nerve paralysis that can mimic stroke symptoms

What is Cranial Nerve VIII called and what does it do?

VIII. Vestibulocochlear nerve:

hearing and balance

What is Cranial Nerve IX called and what does it do?

IX. Glossopharyngeal nerve:

swallowing

taste from posterior tongue

baroreceptor input

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

X. Vagus nerve:

swallowing

speech

PARAsympathetic organ control

baroreceptor input

Which cranial nerve goes into the abdomen?

Vagus nerve (CN X)

Which cranial nerve carries most parasympathetic output?

Vagus nerve (CN X)

What is Cranial Nerve XI called and what does it do?

XI. Accessory nerve:

controls shoulder muscles

What is Cranial Nerve XII called and what does it do?

XII. Hypoglossal nerve:

controls tongue movement

What happens if CN XII is damaged?

Speech impairment

Where does the spinal cord begin and end?

From foramen magnum to L1–L2

What is the cauda equina?

Bundle of spinal nerves below L1–L2

What is the sacral plexus?

Nerves from spinal levels L4–S5

What is the C8 spinal nerve?

A spinal nerve w no matching vertebra :(

What is a ganglion?

Group of neuron cell bodies in the PNS

Are ganglia motor or sensory?

Both motor and sensory

Where are sensory neuron cell bodies located?

Dorsal root (posterior root) ganglion

Where do sensory neurons enter the spinal cord?

Through the dorsal root into the dorsal horn

Where do sensory neurons synapse?

In the gray matter of the spinal cord

Where do sensory signals travel to the brain?

Through the dorsal column pathway to the thalamus

Where are lower motor neuron cell bodies located?

Anterior horn of spinal cord gray matter

Where do lower motor neuron axons exit?

Through the anterior root

Where do lower motor neurons synapse?

On skeletal muscle

Where are interneuron cell bodies located?

Dorsal gray matter of spinal cord

What is the role of interneurons?

They connect sensory and motor neurons in reflexes

What is a reflex arc?

Sensory neuron, interneuron, motor neuron pathway

What is the correct reflex pathway?

Receptor → afferent neuron → integration center → efferent neuron → effector

What is a withdrawal reflex example?

Touching a hot stove and pulling hand away

Do reflexes involve the brain? Why?

No, they are spinal and automatic

What are reflexes?

RAPID, INVOULENTARY responses involving SESORY and MOTOR neurons

What is a knee-jerk reflex?

Example of a simple spinal reflex

What is the spinothalamic tract for?

Pain and temperature sensation

What is the difference between a nerve and a tract?

Nerves are in the PNS; tracts are in the CNS

What is an upper motor neuron?

Neuron in brain that synapses on lower motor neuron

What is a lower motor neuron?

Neuron in spinal cord that connects to muscle

Where are upper motor neurons located?

Primary motor cortex

What is a plexus?

Network of spinal nerves

What is the brachial plexus?

Nerve network serving the arm

What is the order of plexus structure?

Rami → trunks → divisions → cords

What is proprioception?

Sense of body POSITION and MOVEMENT

What tract carries proprioception signals?

SPINO CEREBELLAR tract

What is a test for proprioception?

Close eyes and touch finger to nose

What happens in upper motor neuron disease?

Paralysis with preserved reflexes

What happens in lower motor neuron disease?

Paralysis with absent reflexes

How many spinal nerves are there?

31 pairs

What regions do spinal nerves exit?

Cervical, thoracic, lumbar, sacral regions

Are spinal nerves motor, sensory, or both?

Both motor and sensory

What do lower motor neurons do?

Carry motor commands to skeletal muscles