What structures make up the brainstem?
Midbrain + pons + medulla oblongata
What are the embryonic origings of the three parts of the brainstem?
1. Mesencephalon - Midbrain
2. Metencephalon - Pons
3. Myelencephalon - Medulla oblongata
Label these structures of the brainstem.
4. Medulla oblongata
What makes up the gray matter of the brainstem?
neuroglia cells (NOT Schwann cells!)
Neuronal cell bodies
(ex: astrocytes, oligodendrocytes, microglia cells)
To what do the sensory and motor nuclei of the brainstem contribute?
The cranial motor and sensory nuclei are segmented, either sensory or motor, and have very specific functions - don't need to remember exact nuclei!
What is the difference between tract and nerve?
Tract - aggregate of axons within the central nervous system
Nerve - peripheral nervous system
What makes up the white matter of the brainstem?
Where do the ascending and descending tracts of the brainstem originate? What do they give rise to?
They orginate in the cerebral cortex, brainstem or spinal cord.
They give rise to cranial nerves.
We don't need to memorize this figure but it's a good idea to check it out on Pg 173 of the lecture notes - it's way better than this one.
Are there neuronal cell bodies in white matter?
NO WAY! This is the primary difference between white matter and gray matter.
You guys rock! You're going to ace this exam!
When a section of the brainstem is prepared with Nissle stain...
1. What structures stain blue?
2. What structures stain pink?
3. What does it mean when there is a mixture of blue and pink in a large area?
1. White matter - blue
2. Gray matter - pink
3. Mixed white and gray matter
1. What is the reticular formation?
2. What kind of matter makes up the reticular formation?
1. The large area in the middle of a cross-section of the brainstem that is blue with lots of pink dots - according to Uemera, looks like a kid "mixed two colors of paint."
2. Both white and gray matter - axons and neuronal cell bodies intermixed.
1. What type of cells make up the nuclei in this cross-section?
2. What types of cells make up the tracts in this cross-section?
1. Nuclei (pink) - aggregates of neuronal cell bodies (we don't need to know the names of the nuclei... at least not yet!)
2. Tracts (blue) - myelinated axons
How many of the cranial nerves arise from the brainstem?
10 cranial nerves arise from the brainstem
What part of the brain does the Olfactory nerve (CN I) arise from?
Hint - not in the brainstem
Telencephalon gives rise to olfactory n. (CN I)
From what part of the brain does the Optic nerve (CN II) arise?
Hint: Not the brainstem
The diencephalon gives rise to the optic n. (CN II)
Which cranial nerves arise from the midbrain?
1. Oculomotor (III)
2. Trochlear (IV)
Which cranial nerves arise from the pons?
Which cranial nerves arise from the medulla oblongata?
1. abducent (VI)
2. Facial (VII)
3. Vestibulocochlear (VIII)
4. Glossopharyngeal (IX)
5. Vagus (X)
6. Accessory (XI)
7. Hypoglossal (XII)
Name the cranial sensory nuclei
1. caudate nucleus
3. lateral geniculate nucleus
Name the cranial sensory nuclei
(the 3 with the red arrows are on another card)
1. Cochlear nuclei
2. vestibular nuclei
What does the lateral geniculate nucleus continue as?
The optic tract.
1. What kind of information does the cochlear nuclei receive?
2. Where is it receiving information from?
1. It receives sensory afferent auditory signals
2. From the cochlea in the inner ear
1. What kind of information does the vestibular nuclei receive?
2. Where is this information coming from?
1. It receives sensory information
2. From the vestibular organi within the inner ear
Where do the two different motor fibers in the oculomotor nerve go?
1. To skeletal muscle - motor nucleus of the oculomotor nerve
How do you name the somatic motor nucleus?
Somatic motor nucleus is named after the CN that carries somatic motor fibers to SKELETAL MUSCLE
(ex: Motor nucleus of the oculomotor n.)
How do you name the parasympathetic motor nucleus?
Parasympatheic motor nucleus is named after the CN that carries parasympathetic fibers to SMOOTH MUSCLE and GLANDS
(ex: Parasympathetic nucleus of the oculomo
What is the exception to the cranial motor nucleus naming rules?
Nucleus ambiguus - we will learn more about what it is and its function later.
What is the function of the motor nucleus of the oculomotor nerve?
Innervates the extraocular mm.
(Medial rectus, ventral oblique, dorsal rectus, ventral rectus, levator palpebrae superioris
What is the function of the parasympathetic nucleus of the oculomotor nerve?
To innervate the pupillary spincter and ciliary mm.
What is the functin of the ciliary muscle of the eyeball?
Accomodation of the lens to focus on objects moving nearer/farther.
What is the emerging site of the hypoglossal nerve (XII)?
Emerges from the ventral side of the medulla - the pyramid structure
What is the central nucleus of the hypoglossal nerve (XII)?
The motor nucleus of the hypoglossal nerve. (It is not on the surface of the brainstem)
What is the function of the motor nucleus of the hypoglossal nerve (XII)?
Innervates the skeletal muscle of the tongue.
I'm not sure that you have to ID this, but just know the the tracts come from the central nucleus to form the hypoglossal n.
See pages 2 and 3 of the lecture notes if you want more info... I was kind of confused about what he wanted us to get from this
What is the target tisue of the hypoglossal n (XII)?
Skeletal muscle of the tongue
What is the function of the genioglossus m?
To pull out and depress tongue
Label these structures of the tongue.
1. Styloglossus M.
2. Hypoglossal Nerve (XII)
3. Hyoglossus m.
4. Genioglossus m.
In which direction does the tongue deviate with RIGHT unilateral lesions of the hypoglossal nerve?
Resting or panting - deviates to the LEFT
Licking - deviates to the RIGHT
If the hypoglossal nerve is unilaterally lesioned and the lesion is detected EARLY, to which side does the tongue deviate when the dog is resting/panting?
EARLY LESION: to the NORMAL side when resting/panting
If the hypoglossal nerve is unilaterally lesioned and the lesion is detected EARLY, to which side does the tongue deviate when the dog is licking?
EARLY lesion, tongue deviates to the LESIONED side when licking
If the hypoglossal nerve is unilaterally lesioned and the lesion is CHRONIC, to which side does the tongue deviate when the dog is resting/panting? When it is licking?
CHRONIC unilateral lesion, tongue deviates to the LESIONED side whether the dog is resting/panting OR licking!
What the videos of the people and horses sticking their tongues out at you! Try to figre out which side is lesioned.