Lab 8 Cranial Nerves and Spinal Cord

Question 1

List the 12 Caranial nerves

Answer 1

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

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S=sensory
M=motor

Question 2

I. Olfactory nerve.

Answer 2

FUNCTION:
Sensory – Carries impulses associated with sense of smell

SUPERFICIAL ORIGIN:
From nasal mucosa to olfactory bulb

Question 3

II. Optic nerve.

Answer 3

FUNCTION:
Sensory - Carries impulses associated with vision

SUPERFICIAL ORIGIN:
From retina to optic chiasma

Question 4

III. Oculomotor nerve.

Answer 4

FUNCTION:
Motor - (l) Controls four of the six extrinsic
eye muscles which move the eye (superior,
medial and inferior rectus, and inferior oblique)
(2) Controls the ciliary muscle which varies the shape of lens with changes in distance
(3) Controls circular smooth muscle of iris to constrict pupil of the eye

SUPERFICIAL ORIGIN:
Midbrain

Question 5

IV. Trochlear nerve.

Answer 5

FUNCTION:
Motor - Controls one of the six extrinsic eye muscles which move the eye (superior oblique)

SUPERFICIAL ORIGIN:
Midbrain to

Question 6

V. Trigeminal nerve.

3 parts

Answer 6

FUNCTION:
a) Ophthalmic
Sensory - Pain, touch and temperature from nasal mucous membrane, facial skin and cornea

b) Maxillary
Sensory - Pain, touch and temperature from facial skin, mouth, upper teeth

c) Mandibular
Sensory – Pain, touch and temperature from skin of chin, lower teeth and anterior two-thirds of tongue
Motor - Muscles of mastication (chewing)

SUPERFICIAL ORIGIN:
Pons

Question 7

VI. Abducens nerve.

Answer 7

FUNCTION:
Motor - Controls one of the six extrinsic eye muscle which move the eye (lateral rectus)

SUPERFICIAL ORIGIN:
Pons

Question 8

VII. Facial nerve.

Answer 8

FUNCTION:
Sensory - Taste from anterior two-thirds of tongue
Motor - To muscles of face, ears and scalp responsible for facial expression. Secretion of saliva and tears

SUPERFICIAL ORIGIN:
Pons

Question 9

VIII. Vestibulocochlear nerve.

Answer 9

FUNCTION:
a) Cochlear
Sensory – Carries impulses associated with sense of hearing

B) Vestibular
Sensory - Registers the movement of the body through space and the position of the head. Communication with cerebellum to maintain body equilibrium and coordination of muscle function

SUPERFICIAL ORIGIN:
Groove between pons and medulla oblongata

Question 10

IX. Glossopharyngeal

Answer 10

FUNCTION:
Motor - To muscles of pharynx and base of tongue; also stimulates secretion of the parotid salivary gland
Sensory - Touch, temperature and pain from pharynx; taste from posterior one-third of tongue

SUPERFICIAL ORIGIN:
Medulla oblongata

Question 11

X. Vagus

Answer 11

FUNCTION:
Motor - To muscles of larynx for swallowing. To smooth muscle of digestive tract (from esophagus to large intestine) to increase motility and in airways to bronchio- constrict. To glands of the digestive tract. To cardiac muscle to slow heart rate.
Sensory - From baroreceptors and chemoreceptors and mucous membranes of larynx, trachea, lungs, esophagus, stomach, gall bladder and intestines; taste from epiglottis

SUPERFICIAL ORIGIN:
Medulla oblongata

Question 12

XI. Spinal Accessory

Answer 12

FUNCTION:
Motor - To muscles of pharynx, larynx, and soft
palate and trapezius and sternocleidomastoid muscles. Swallowing and movement of the head and shoulders.

SUPERFICIAL ORIGIN:
Medulla oblongata and spinal cord

Question 13

XII. Hypoglossal

Answer 13

FUNCTION:
Motor - To muscles of tongue. Movement of tongue during speech and swallowing

SUPERFICIAL ORIGIN:
Medulla oblong

Question 14

Two grooves mark the surface of the spinal cord

Answer 14

anterior median fissure

the shallower posterior median sulcus

Question 15

The projections of the grey matter are referred to as

Answer 15

horns of grey matter (dorsal, ventral and lateral).

Question 16

The white matter in the outside area of the cord is divided into

Answer 16

columns of white matter (dorsal, ventral and lateral).

Question 17

How many pairs of spinal nerves?

Answer 17

31

Question 18

pairs of spinal nerves attach to various regions of the cord via two bundles of axons called _____. Each __________ has a swelling called the ___________ which contains the cell bodies of sensory neurons

Answer 18

bundles of axons called ROOTS (dorsal and ventral).

Each dorsal root has a swelling called the dorsal root ganglion which contains the cell bodies of sensory neurons

Question 19

The spinal cord has two main functions:

Answer 19

1) acts in conduction and integration of sensory and motor impulses to and from the brain
2) serves as an integration center for some reflexes.

Question 20

Reflex

Answer 20

a rapid unconscious reaction to a certain stimulus

Question 21

A basic reflex arc consists of 5 components:

Answer 21

(1) a receptor which responds to a stimulus
(2) the sensory, or afferent neuron, which enters the dorsal root of the spinal cord (its cell body is found in the dorsal root ganglion)
(3) the integrating center within the grey matter of the spinal cord and transfers information from the sensory neuron to the motor neuron. The integration center of a monosynaptic reflex arc involves a single synapse between a sensory and motor neuron. In a polysynaptic reflex arc, the integrating center consists of multiple synapses involving one or more connecting neurons (interneurons). Still within the grey matter, the connecting neuron synapses with the
(4) motor, or efferent neuron which has its cell body in the grey matter. Impulses are carried along the motor neuron in the ventral root to the
(5) effector organ, usually a muscle or gland.

Question 22

What is the simpliest nerve pathwa

Answer 22

reflex arc

Fast and protective in function

Sensory nerves use dorsal roots to get to spinal cord.
Motor neurons always use the ventral root

Question 23

4 types of reflexes to know

Answer 23

The Patellar Reflex:
The Achilles Reflex
The Babinski Reflex (Planter Reflex)
The Swallowing Reflex

Question 24

The Achilles Reflex

Answer 24

How to:
Have a subject kneel on a stool. Tap the Achilles tendon (just above the heel) with the reflex hammer

Response:
the toes point down (planter reflexion)
The ankle jerk reflex.

Question 25

The Babinski Reflex (Planter Reflex)

Answer 25

How to:
Have a subject remove one shoe and sock. Scratch the sole of their foot by moving a blunt object

Response:
Adults: toes curl down, 0-18mon Toes go up and spread out

The ‘Babinski Sign’ is an abnormal reflex in adults but quite normal in children less than 18 months of age. In this case, the big toe extends upward and the other toes spread apart. The presence of the Babinski sign in adults is considered an indication of neurological damage to the pyramidal tract of the spinal cord

Question 26

The Swallowing

Answer 26

How to: Swallow all the saliva in your mouth and then immediately try to swallow again.

Response:
you can’t swallow again right away (a mech to keep you from choking), it makes sure whatever you swallow doesn’t go into trachea.

What would happen if you swallowed several times in rapid succession while drinking a glass of water?
-the water would go all over the place, we can gulp (opening the throat) but not repeating swallowing

Can you prevent yourself from swallowing?

• No. Once the actions started the reflex takes over and must to completed.
• From defencse point of view it stops you from choking.

Question 27

The Patellar Reflex:

Answer 27

How to:
Sit with your legs crossed, relax and close your eyes. Have someone tap the skin over the patellar tendon (just below the kneecap) with the reflex hammer.

Response:
Quad muscle contracts which causes extension of lower leg in a kicking motion