CRANIAL NERVES (14.8)

Facial (VII) Nerve

-Mixed cranial nerve 1)Motor to the face - FACIAL expressions 2)Motor to salivary glands (autonomic) - (secretion is a motor action) 3) Sensory from the anterior 2/3 of tongue for taste

What are three cranial nerves that are directly associated with the the 'movement of the eyeball'?

1) Oculomotor (III) Nerve 2) Trochlear (IV) Nerve 3) Abducens (VI) Nerve (3.4.6) (POTENTIAL TO BE IN THE MC / MIX THEM UP WITH REST OF THE OTHER 12 CRANIAL NERVES)

How is Olfactory (I) Nerve different

1) Sensory nerve that does not relay through thalamus or the brainstem BYPASS THALAMUS/BRAINSTEM

Olfactory Nerve project on

1)Primary olfactory area 2) Hypothalamus 3) Limbic System

Motor axons that innervate skeletal muscles are of two types

1. Branchial motor axons: innervate skeletal muscles that develop from the pharyngeal (branchial) arches. These neurons leave the brain through the mixed cranial nerves and the accessory nerve.

Rods

Black and white /dim light --> cells that are STRICTLY receptors

Bundles of axons of olfactory receptors= Olfactory nerves

Bundles of axons of olfactory receptors extend through about 20 olfactory foramina(opening) in the cribriform plate of the ethmoid bone on each side of the nose. These 40 or so bundles of axons collectively form the right and left olfactory nerves.

Cons

Colour (red, blue and green)/ bright light --> cells that are STRICTLY receptors

How are cranial nerves classified?

Cranial nerves are classified as motor, special sensory, and mixed

What are 'Motor Nerves'?

Five cranial nerves (III, IV, VI, XI, and XII) are classified as motor nerves because they contain only axons of motor neurons as they leave the brain stem.

vestibulocochlear (VIII) nerve

It is a sensory cranial nerve and has two branches, the vestibular branch and the cochlear branch

Autonomic Motor Axon

Motor axons that innervate smooth muscle, cardiac muscle, and glands are called autonomic motor axons and are part of the parasympathetic division.

Oculomotor (III) Nerve

Motor nerve to 4 out of six muscles that move the eyeball somatic: movement of eyeball autonomic: accommodation

Abducens (VI) Nerve

Motor to a muscle called lateral rectus, abductor to the eyeball

How many Cranial Nerves are they?

The 12 pairs of cranial nerves

1-Olfactory receptors (bipolar neurons)

The olfactory receptors within the olfactory epithelium are bipolar neurons.The olfactory epithelium occupies the superior part of the nasal cavity.

Optic (II) Nerve

The optic (II) nerve (vision) is entirely sensory; it contains axons that conduct nerve impulses for vision

5-Hypothalamus

To initiate autonomic responses such as salvation

Optic Chiasm

Two optic nerves merge to form the optic chiasm. Within the chiasm, axons from the medial half of each eye cross to the opposite side; axons from the lateral half remain on the same side.

3-Olfactory bulb cont

Within the olfactory bulbs, the axon terminals of olfactory receptors form synapses with the dendrites and cell bodies of the next neurons in the olfactory pathway.

Trigeminal (V) Nerve

-Mixed cranial nerve and the largest of the cranial nerve 1)Sensory from face (three zones) 2)Motor to muscles of mastication (chewing)

Motor axons that innervate skeletal muscles are of two types

2. Somatic motor axons innervate skeletal muscles that develop from head somites (eye muscles and tongue muscles). These neurons exit the brain through five motor cranial nerves (III, IV, VI, XI, and XII).

5-Primary olfactory area

Axons in the olfactory tracts end in the primary olfactory area in the temporal lobe of the cerebral cortex.

Optic nerve

Axons of all the ganglion cells in the retina of each eye join to form an optic nerve, which passes through the optic foramen.

Vestibular Branch

Carries impulses for equilibrium

Cochlear branch

Carries impulses for hearing.

Bipolar neurons structure

Each has a single odor-sensitive, knob-shaped dendrite projecting from one side of the cell body and an unmyelinated axon extending from the other side. Bundles of axons of olfactory receptors extend through about 20 olfactory foramina in the cribriform plate of the ethmoid bone on each side of the nose. These 40 or so bundles of axons collectively form the right and left olfactory nerves.

Ganglion Cells

FIRST neurons in the pathway found in the eyeball. Dendrites of the ganglion synapse with the rods and cons and its axons travel in bundels and exit the eye to FORM THE OPTIC NERVE

Optic Receptors (Rods/Cons)

In the retina(back of the eyeball), rods and cones initiate visual signals and relay them to bipolar cells, which transmit the signals to ganglion cells.

3-Olfactory bulb

Olfactory nerves end in the brain in paired masses of gray matter called the Olfactory Bulbs, two extensions of the brain that rest on the cribriform plate.

Cranial Nerves are part of the

Peripheral Nervous System (PNS) (just LIKE the 31 pairs of Spinal Nerve)

Pathway Optic (II) Nerve

Rods and cones receptors →ganglion cells→optic nerve→optic chiasm→thalamus→|midbrain (to follow sight)| and optic track→primary visual centre

5-Limbic system

Smells are associated with memory and feeling/emotions ... it's sometimes called the "emotional brain," Smell can call up memories and powerful emotional responses almost instantaneously.

Trochlear (IV) Nerve

Somatic motor cranial nerve: movement of eyeballs—motor to super oblique muscle of the eye.

4-Olfactory tracts

The axons of (the neurones that got synapsed by the olfactory receptor in the olfactory pathway) neurons make up the olfactory tracts, which extend posteriorly from the olfactory bulbs

Where are 'Special Sensory Nerves' LOCATED?

The cell bodies of most sensory neurons are located in ganglia outside the brain. Special Sensory Nerves carry axons of sensory neurons.

Where are 'Motor Nerves' LOCATED?

The cell bodies of motor neurons lie in nuclei within the brain.

Each cranial nerve has a NAME indicate

The names designate a nerve's distribution or function.

Each cranial nerve has a NUMBER, designated by a roman numeral indicate

The numbers indicate the order, from anterior to posterior, in which the nerves arise from the brain.

Olfactory (I) Nerve

The olfactory (I) nerve (to smell) is entirely sensory; it contains axons that conduct nerve impulses for olfaction, the sense of smell.

Optic tracts

The regrouped axons, some from each eye, form the optic tracts. Most axons in the optic tract end in the thalamus 1) A few axons pass through thalamus and then extend to the midbrain. 2) There they synapse with neurons whose axons extend to the primary visual area in the occipital lobe of the cerebral cortex. 3) They synapse with motor neurons that control the extrinsic and intrinsic eye muscles.

What are 'Mixed Nerves'?

The remaining four cranial nerves (V, VII, IX, and X) are mixed nerves—they contain axons of both sensory neurons en- tering the brain stem and motor neurons leaving the brain stem.

Why are they named as Cranial Nerves?

They are named because they pass through various foramina in the bones of the cranium and arise from the brain inside the cranial cavity.

What are the FUNCTION of 'Special Sensory Nerves'?

They carry axons of sensory neurons and thus are called Special sensory nerves These nerves are unique to the head and are associated with the special senses of smelling, seeing, and hearing.

What are 'Special Sensory Nerves'?

Three cranial nerves (I, II, and VIII)