Diencephalon and Brainstem Flashcards
What is the only visible surface of the diencephalon
The Inferior surface
The thalamus is a sensory relay system except for
Olfaction
The right and left thalamus communicate via the
Interthalamic adhesion
Boundaries of the thalamus
- Medial
- Lateral
- Inferior
- Superior
- Anterior
- Posterior
- Wall of the 3rd ventricle
- Against wall of internal capsule
- Continuous with the tegmentum
- Small layer of white matter
- Posterior boundary of the inter ventricular foramen, which is where CSF flows from the lateral ventricle to the 3rd ventricle.
- Pulvinar (overhangs the superior colliculus)
What divides the thalamus into three divisions?
The internal medullary lamina. White matter.
3 divisions of important nuclei in the thalamus
- Anterior superior
- Medial posterior
- Lateral posterior
- Ventral tier
- Dorsal tear
What is the role of the anterior superior portion of the thalamus
Projects to the cingulate gyrus apart of the limbic system. Plays a role in short term memory and emotion.
What is the role of the medial posterior portion of the thalamus
Contains numerous nuclei that are involved with integration of somatic, olfactory and visceral information and their relations to emotions. This portion is the closest to the third ventricle.
What are the two branches of the lateral posterior division of the thalamus?
- Ventral tier
- Ventral anterior projects to the secondary motor cortex and the ventral lateral nuclei projects to the primary motor cortex.
- Ventral posterior projects to the somatosensory cortex. - Dorsal tier
- LGN to optic radiations then primary visual cortex
- MGN gathers auditory info from contralateral ear and sends to auditory cortex.
- Pulvinar is related to visual attention. Unclear on specifics.
The sub thalamus is known for?
What does it contain?
Fine motor controls. it contains many nuclei and cranial ends of the substantia nigra and red nucleus.
The sub thalamus is located between which two structures
The thalamus and the midbrain.
Epithalamus is located near the
posterior thalamus (by the pulvinar end)
Epithalamus contains which two structures
The pineal gland (secretes melatonin in response to detection of light by the retina)
The habenular nucleus. Connects the R and L nuclei with commissural fibers. Integration center for olfaction, visceral and somatic afferent integration.
Hypothalamus role
Afferent- Any afferent signal, anywhere in the body, can go to the hypothalamus.
Efferent- Major output to parasympathetic, sympathetic, thalamus, limbic system, reticular formation (consciousness)
Other- Hormones and blood via the pituitary.
You could compare which structure in the diencephalon to the vagus nerve
The hypothalamus. wants to be involved with everything
The pineal gland is connected to the retina via the
Midbrain.
Pinealocytes
Endocrine cells that secrete inhibitory substances (melatonin when retina senses darkness). Melatonin goes to pituitary gland and slows production of hormones.
Efferent connections from the hypothalamus to the pituitary gland. Why is this a special connection?
Because the hypothalamus communicates with both, the posterior and anterior portions of the pituitary gland.
Hypothalamus to posterior lobe by the infundibulum
Hypothalamus to anterior lobe by bloodstream through the hypothalamic-hypophyseal portal system.
What is the role of the hypothalamus
Essential for life. Controls homeostasis via the autonomic NS and endocrine system and influences emotional behavior.
Almost all bodily functions are influenced by the hypothalamus.
- Eating
- Emotion
- Circadian rhythms
- Temperature
The brainstem is divided into which 2 divisions
- The hindbrain/rhombencephalon- Metencephalon (pons) and myelencephalon (medulla)
- Mesencephalon/midbrain
The medulla is bound inferiorly by the __ and superiorly by the ___
Spinal cord
Pons
Anterior surface of the medulla contains which 3 main structures
Contains 2 pyramids (contain corticospinal tract fibers) which are divided by the anterior median fissure.
At the inferior end of the pyramids, there is a crossing over of the fibers, called the decussation of the pyramid.
On either side of the pyramids, there is an olive, which contain olivary nuclei.
The superior part of the posterior medulla makes up the floor of
the 4th ventricle
What structure connects the brainstem to the cerebellum?
The brainstem is connected to the cerebellum by the middle cerebellar peduncles. On the lateral surface of the pons.
The transverse fibers on the anterior surface of the pons make up the
Pontocerebellar pathway. Involved in motor coordination and learning. Very motor.
Fibers on the right side of the pons project to the left side of the cerebellum
What structure within the pons contains the nuclei of CN 7 and fibers of CN 6?
Found in the dorsal pons, in the medial eminences/medial coliculous (mound)
Pathway to get from cortex to the cerebellum through the pons.
Cortiocopontine fibers from the cerebral cortex travel to the pontine nuclei, where they synapse and begin the pontocerebellar pathway. Pontine nuclei axons are transverse fibers where travel contra laterally to the middle cerebellar peduncles and then to the cerebellum.
This is the pontocerebellar pathway.
Pontine tissue anterior/ventral to the trapezoid body is called the ___ and are apart of the ____pathway
Basal part of the pons and is apart of the auditory pathway.
The corticospinal pathway is found where in a cross section of the pons
In the basal portion of the pons. This is the most anterior portion of the pons, anterior to the trapezoid body.
Tegmentum of pons is located where
Is the posterior/dorsal division of the pons behind the trapezoid body.
Pontine tissue posterior to the trapezoid body is the
Tegmentum
The tegmenum of the pons contains
- Nuclei for CN 5, 6, and 7.
- Contains sensory tracts for medial lemniscal and anterolateral pathway.
- 4th ventricle and the floor of the 4th ventricle, the facial colliculi are formed when the axons from CN 7 wrap around the nuclei of CN 6.
- Spinal nucleus of CN 5, which is all throughout the pons. and then motor nucleus of CN, which is only seen at the mid-pons level.
Facial colliculi
Formed because the axons of CN 7 wrap around the nuclei of CN 6, causing a mound that is inferior to the medial eminences. Can see on the posterior pons when cerebellum is removed.
Forms the floor of the 4th ventricles.
Midbrain connects the __ and __ to the __ and __
Connects the pons and cerebellum to the diencephalon and the cerebrum.
In other words, connects the rhombencephalon to the proencephalon.
Another name for the cerebral peduncles
Crus cerebri
The anterior side of the midbrain is framed by ___
It is mostly covered by the ____, which is the main connection between the cerebrum and the midbrain.
Framed by the optic chiasm.
Mostly covered by the cerebral peduncles. Contains projection fibers that pass from the coronal radiata and internal capsule. Major afferent or efferent paths travel through here- the anterolateral, media lemniscal, and corticospinal.
Ventral surface of the midbrain contains
It is bounded laterally by the cerebral peduncles, which makes a pit in the center called the interpeduncular fossa.
CN 3 and 4 emerge ventrally at the posterior end. Nuclei are located in the tegmentum (middle).
Lateral surface of the midbrain contains which two structures (2 on each side) that connect to the thalamus?
- Superior brachium connects the superior colliculus with the LGN of the thalamus and the optic tract.
Superior colliculous–> superior branchium–> LGN
The inferior brachium connects the inferior colliculous with the MGN of the thalamus.
Inferior colliculous –> inferior branchium –> MGN
What is the corpora quadrigemina
On the dorsal surface of the midbrain. Contains 4 mounds- 2 on top and 2 on the bottom.
The two on the top are the superior colliculi. Super brachium fibers extend to reach the LGN.
The two on the bottom are the inferior colliculi. Inferior brachium fibers extend to reach the MGN.
The cerebral aqueduct runs through the internal midbrain, between what?
What is it surrounded by?
between the 3rd and 4th ventricles. It separates the posterior/dorsal tectum layer from the middle tegmentum layer.
Surrounded by a ring of grey matter called the periaquaductal gray.
The tectum is located where in the midbrain and contains what
- It is located dorsally to the cerebral aqueduct which drains CSF from the 3rd to the 4th ventricle.
- Contains the corpora quadrigemina- which is the 2 superior and 2 inferior colliculi which travel to the LGN and MGN.
** Contains the pretectal nuclei that are anterior to the superior colliculi and are involved in the pupillary light reflex.
Compare the two divisions of the pons to the 3 divisions of the midbrain.
The pons:
Dorsal/posterior: Tegmentum. Contains CN nuclei of 3 and 4
Ventral/anterior: Basal portion.
Midbrain:
Dorsal/posterior: Tectum
Middle: Tegmentum. Contains CN nuclei for 3 and 4 and the red nuclei at the superior coliculous level.
Ventral/anterior: Crus cerebri which is the cerebral peduncles, which major pathways travel through.
Edinger-westphal nuclei is in which part of the brain
In the midbrain in the tegmentum.
The red nuclei is found in the tegmentum at the level of the
Superior colliculi of the midbrain. Red due to high vascularity and iron.
How does the oculomotor nucleus and edinger westphal nucleus work together
Edinger westphal allows for parasympathetic pupillary constriction. Can also cause an accommodative response by the ciliary body.
GSE innervation through CN III stimulates medial rectus muscles so eyes converge.
Tegmentum of the midbrain contains
Substantia nigra and the red nucleus. Also contains nuclei for CN 3, 4.
