4.15. Diencephalon and Midbrain; Brainstem

Question 1

Diencephalon divisions

Answer 1

Epithalamus – around the thalamus

Dorsal thalamus/thalamus (literally just that)

Hypothalamus – below the thalamus

Subthalamus – further below the thalamus

Question 2

Fossa through which the oculomotor nerve leaves

Answer 2

Interpeduncular fossa (behind the cerebral peduncles/kind of within that area)

Question 3

Epithalamus components (hint: all things habenular, commissurating in the back, the melatonin secreting gland)

Answer 3

Habenula

Habenular commissure (connects the tecta from the left side to the right side)

Stria medullaris

Habenulointerperduncular tract

Pineal gland

Posterior commissure

Question 4

Function of the following:

Posterior commissure

Pineal gland

Habenula

Answer 4

Posterior commissure looks like a white matter curved C in midsagittal section; and connects the two sides of the tectum; involved in coordination of the pupillary light reflex and vertical eye movements

Pineal gland: secretes melatonin and involved in reproductive cycle in animals

Habenula: involved in relay of limbic info from septal nuclei/preoptic area to the paramedian midbrain reticular nuclei

Question 5

Function of stria medullaris and habenulointerpeduncular tract

Answer 5

Stria medullaris carries fibers fromt he septal nuclei and preoptic area

Habenulointerpeduncular tract carries fibers to the paramedian midbrain reticular nuclei

Question 6

What’s the internal capsule?

Parts of the internal capsule

Answer 6

Internal capsule is the pathway to and from the neocortex and runs through the diencephalon

Anterior limb

Genu

Posterior limb

Question 7

Function of the anterior limb, genu, and posterior limb of the internal capsule

Significance of the topographic arrangement of the internal capsule fibers

The fibers coming down the internal capsule form part of the ___

Answer 7

Anterior limb carries fibers going to/coming from the frontal cortex

The genu carries motor fibers going from the motor cortex going all the way down to the spinal cord and brain stem regions

The fibers come down the internal capsule in a topographic fashion; if there’s a lesion in the internal capsule, you’ll have paralysis contralaterally (i.e. because of the way the fibers are arranged, if you have a lesion in one part of the body, paralysis will manifest on the opposite side)

Cerebral peduncles

Question 8

All of the thalamic nuclei

A

DM

LD

VA

VL

VPL

VPM

LP

CM

PF

P-vnar

MGB

LGB

Answer 8

A: Anterior nucleus

DM: Dorsomedial nucleus

LD: Laterodorsal nucleus

VA: Ventral anterior nucleus

VL: Ventral lateral nucleus

VPL: Ventral posterolateral nucleus

VPM: Ventral posteromedial nucleus

LP: Lateroposterior nucleus

CM: Centromedian nucleus

PF: Parafascicular nucleus

P: Pulvinar

MGB: Medial geniculate nucleus

LGB: Lateral geniculate nucleus

Question 9

Function of:

Anterior nucleus

Pulvinar

VA and VL nuclei

VPL, VPM, LGN, MGN

Answer 9

Anterior nucleus is part of the limbic system; it received limbic information through the mamillothalamic tract and projects it into the cortex

Pulvinar - visual association

MGN: primary auditory thalamic nucleus; projects to the primary auditory cortex in the upper temporal lobe (recall those transverse temporal gyri; BA 41 and 21)

LGN: primary visual thalamic nucleus; projects to the primary visual cortex (BA 17 and calcarine fissure)

VPL and VPM are also sensory

VA and VL: motor nuclei

Question 10

What happens if you lose the VPL, VPM, LGB and MGB?

Answer 10

VPL, VPM, LGB and MGB are all sensory nuclei and if you get rid of them, you’ll have zero sensation in that area that’s lost the nuclei (you’d have visual and auditory defects)

Question 11

Thalamic nuclei in the frontal lobe (if you get an MD, you can buy a VolVa and park it in the front of the neighborhood)

Answer 11

Mediodorsal nucleus + part of anterior nucleus

Ventral anterior

Ventral lateral (in the precentral gyrus)

Question 12

Thalamic nuclei in the parietal lobe

Answer 12

VPL

VPM
Lateral posterior

Pulvinar

Lateral dorsal

part of anterior nucleus

Question 13

Thalamic nuclei in the temporal lobe

Answer 13

Medial geniculate nucleus

Question 14

Brainstem subdivisions

Answer 14

Midbrain – tectum and tegmentum

Pons

Medulla

Rhomboid fossa

(cerebellum and 4th ventricle as well?)

Question 15

which pedunles are present when you chop the cerebellum off?

Answer 15

the superior, inferior, and middle cerebellar peduncles (middle one is more lateral)

Question 16

midbrain components

(red and black PAG)

(T and T + VTA)

(raphe’s midbrain has a weird locus and reticular formation)

Answer 16

red and black PAG: red nucleus, substantia nigra and periaqueductal gray

tectum and tegmentum and ventral tegmental area

raphe nuclei

locus coeruleus

midbrain reticular formation

Question 17

superior and inferior colliculus functions

(hint: going to the top of the hill you need good orientation reflexes so you don’t fall off; if your ears are too small you can’t hear anything

Answer 17

Superior colliculus: responsible for orientation reflexes; more of a steep hill, has a large nucleus inside

Inferior colliculus: responsible for auditory info; brings in auditory information to the medial geniculate body

Question 18

function of red nucleus

Answer 18

involved in gross motor coordination (also the origin of the rubrospinal tract)

Question 19

function of locus coerulus (also, where is it?)

Answer 19

main site of norepinephrine synthesis (sens to hippocampus, basal ganglia and cortex);

its in the midbrain (somewhere close to the pons)

Question 20

functions of reticular formation

Answer 20

forms part of the Ascending Reticular Activating System that regulates behavioral awareness and consciousness (i.e. keeps you awake and attentive)

also is the origin of the reticulospinal tract

Question 21

where are the raphe nuclei in the brain?

what do they do? (hint: the’yre affected by serotinin inhibitors)

Answer 21

along the rostrocaudal axis of the brainstem and medulla, right along the midline

they produce serotonin and send it to the entire brain, cerebellum + spinal cord

Question 22

Where to pontine neuclei send their fibers to and through which cerebellar peduncle?

Middle cerebellar peduncle: afferent pathway that carries these fibers to the cerebellar cortex and deep cerebellar nuclei

What happens to fibers moving through the internal capsule?

Answer 22

synaptic pathway between cortex and cerebellum via the corticopontocerebellar pathway

the fibers moving through the internal capsule will terminate in the pontine nuclei; the neurons in the pontine nuclei will carry the info to the contralateral cerebellum (the X in the diagram means the axons will cross over the other side of the brain)

Question 23

why would a lesion in the facial colliculus of the rhomboid fossa result in eye movement issues and facial paralysis?

what are the 2 trigones that make up the rhomboid fossa?

Answer 23

Facial colliculus: facial nerve makes a loop around the abducens nucleus in this region; a lesion here would cause problems with eye movements and facial paralysis

vagal and hhypoglossal trigone;

vagal trigone and hypoglossal trigone contain the motor nuclei of the vagus and hypoglossal nerves; the hypoglossal trigone is more medial, the vagal trigone is lateral to the hypoglossal trigone

Question 24

Which cranial nerve nuclei are in the midbrain (they help you move your eyes?)

Answer 24

Edinger-Westphal (VM III) - level of superior colliculus

Oculomotor ( SM III) - around superior colliculus as well

Trochlear (SM IV) - level of inferior colliculus

Question 25

At the level of the pons, which nucleus has somatosensory functions (hint: the main mesencephalon from the spine)

Answer 25

Mesencephalic (SS V)

Main sensory (SS V)

Spinal sensory (SS V)

Question 26

At the pontine level, which nuclei have brachial motor control of five faces?

Answer 26

Motor for V

Facial n (VII)

Question 27

At the pontine level, which one cranial nerve controls eye movement - somatic motor

Which one provides balance? - special sensory

Answer 27

Abducens (SM VI)

Vestibular (SpS VIII)

Question 28

At the level of the medulla, which cranial nerves control facial expression, is ambiguous and can sing in Vegas, and wears nice accessories?

Answer 28

Nucleus Ambiguus (BM IX, BM X)

Facial nucleus

Accessory nucleus

Question 29

At the level of the medulla, which nuclei does

somatosensory

visceral sensory

Answer 29

Spinal sensory for trigeminal (V)

Nucleus of the solitary tract (X)

Question 30

At the medulla level, which nuclei have special sensory function? (a dude in solitude has balanced hearing)

Answer 30

vestibular and cochlear (VIII)

solitary nucleus (IX)

Question 31

At the level of the medulla, which cranial nerve does visceral motor function? (you can party in Vegas)

Answer 31

Dorsal motor of the Vagus (X)

Question 32

At the level of the medulla, cranial nerve does nuclei somatic motor? (hint: moves your tongue)

Answer 32

Hypoglossal (XII)

Question 33

At the level of the spinal cord:

which cranial nerve’s nucleus provides somatosensory input?

Which one does somatic motor?

Answer 33

Spinal sensory of Trigemina (V)

Accessory XI

Question 34

what modalities do the alar and basal plate have during development into adulthood?

Answer 34

alar plate (becomes dorsal horn of spinal cord): somatic motor; visceral motor

basal plate (becomes ventral horn of spinal cord): visceral sensory; somatic sensory

Question 35

branchial arches give rise to___ (hint: 4 groups of muscles; about chewing and your face; the singing ones)

Answer 35

1st Muscles of mastication (CN V)

2nd Muscles of facial expression

3rd Stylopharyngeus (CN IX)

4th Palatal, pharyngeal and laryngeal muscles (CNX)

Question 36

optic placode gives rise to the __ and ___, which are responsible for hearing and balance

the ___ is responsible for hearing, while the __ are responsible for balance

Answer 36

Optic placode gives rise to the ear and cochlea, are responsible for hearing and balance

cochlear apparatus

semicircular canals