Anatomy Of Diencephalon Flashcards
Thalamus
Collection of approximately 120 nuclei that all function to process all sensory information (except olfaction) that goes to the cerebral cortex
What is the landmark in the thalamus that divides the thalami nuclei into Groups
Internal medullary lamina
Divides into medial/lateral and anterior groups based on function
Ventral anterior (VA) nuclei group
A grouping that is part of the lateral nuclear group of thalamic nuclei
Receives information from Globus pallidus/ basal nuclei and relays it to the motor cortex (BA-6)
- helps with relaying motor information
Ventral lateral (VL) nuclei group
A grouping that is part of the lateral nuclear group of thalamic nuclei
Receives information from Globus pallidus/ basal nuclei and relays it to the precentral gyrus (BA-4)
- helps with relaying primary motor information
Ventral posterolateral (VPL) nuclei group
A grouping that is part of the lateral nuclear group of thalamic nuclei
Receives information from spinal cord and relays it to the post central gyrus (BA-1)
- helps with relaying somatosensory information
Ventral posteromedial (VPM) nuclei group
A grouping that is part of the lateral nuclear group of thalamic nuclei
Receives information from spinal cord and relays it to the post central gyrus (BA-1)
- helps with relaying somatosensory information
- specifically cranial nerve inputs and taste*
Mediodorsal (MD) nuclei grouping
A grouping that is part of the medial nuclear group of thalamic nuclei
Connects limbic pathway information to the frontal cortex, relaying information to be processed
Pulvinar nuclei grouping
A grouping that is part of the dorsal nuclear group of thalamic nuclei
Relays behavioral orientation information to relevant visual/auditory stimuli
Lateral geniculate (LGN) nuclei grouping
A grouping that is part of the dorsal nuclear group of thalamic nuclei
Relays visual inputs to the cortex to be processed
Medial geniculate nuclei (MGN) grouping
A grouping that is part of the dorsal nuclear group of thalamic nuclei
Relays auditory inputs to the cortex to be processed
Anterior nucleus group of the thalamus
Functions to relay limbic information to respective pathways to process.
Very crucial to behavioral patterns and mental health
Intralaminar thalamic nuclei
Lie within the internal medullary lamina
Receive inputs from numerous pathways including other basal nuclei And sends them to respective regions of the cortex
Has reciprocal connections with cortex so can relay from cortex -> other basal nuclei when needed
Reticular thalamic nuclei
Receives input from cortex and other thalamic nuclei
DOES NOT project to cortex, instead makes synoptic connections with other thalamic basal nuclei groupings
Regulates thalamic activity from its inputs via GABAergic neurons
Habenula
A nucleus in the epithalmaus
Functions to serves as a relay between the limbic system and hypothalamus -> midbrain functions
Pineal gland
no direct connections to the CNS
Part of the epithalamus
Receives neural input from sympathetic nervous system via the superior cervical ganglia
Functions to release hormones based on a circadian rhythm (light based)
- melatonin
- serotonin
- NE
Subthalamus functions
Sub thalamic nuclei
- maintains reciprocal connections within the globus pallidus
- plays a role in regulating motor functions
also possesses zona incerta, but its function is not well understood
Medial hypothalamic area divisions and its respective nuclei
1) preotic area
- medial preotic nuclei
2) anterior (supraoptic) region
- anterior hypothalamic nuclei
- supraoptic nuclei
- paraventricular nuclei
- suprachiasmatic nuclei
3) middle (tuberal) region
- arcuate nuclei
- ventromedial nuclei
- dorsomedial nuclei
4) posterior (mammillary region)
- medial mammillary nuclei
- intermediate mammillary nuclei
- lateral mammillary nuclei
- posterior hypothalamic nuclei
Pituitary gland (hypophysis)
Controls the activity of almost all other hormone secreting glands
connected to hypothalamus via infundibulum
2 divisions:
1) anterior (adenohypophysis)
- produces and releases = ACTH, GH, TSH, LH, FSH, prolactin
2) posterior (neurohypophysis)
- produces and releases = oxytocin, ADH
How does the pituitary receive blood?
From the inferior and superior hypophysial arteries from the ICA
Hypophysial portal system
The capillary network in which the anterior pituitary horomones are released via inputs from the hypothalamus
- hypothalamus sends regulatory signals through here
Median eminence
Location of the first capillary system from the hypophysial portal system
Send factors from the following nuclei into the anterior pituitary via the hypophysial portal veins
- arcuate nucleus
- periventricular nucleus
- medial preoptic nucleus
- paraventricular nucleus
Pituitary Capillary plexus
2nd capillary plexus located within the anterior pituitary
Hormones releases from the anterior pituitary are sent into the 2nd capillary plexus (pituitary capillary plexus) and are drained into body via cavernous sinuses
Does the posterior pituitary hormones get produced there?
NO, they are produced in the paraventicular and supraoptic nuclei
The hormones are then transported via axons to the posterior pituitary capillary plexus to be distributed throughout the body
Hypothalamic-pituitary-adrenal axis (HPA)
Demonstrates the negative feedback loop that hormone organs have on each other
Example: release of CRH from the hypothalamus -> anterior pituitary to secrete ACTH -> goes to adrenal glands to secrete cortisol.
Once threshold concentrations are reached in the body for cortisol, cortisol then initiates negative feedback on the hypothalamus and anterior pituitary to stop secreting CRH and ACTH respectively
Hypothermic integrative functions
Regulation of cardiovascular processes
Temperature regulation
Feeding,drinking and sexual behavior
Aggression and rage
Biological rhythms
Sleep
What are the 4 hypothermic nuclei that work to regulate cardiovascular processes?
Paraventricular nucleus
Lateral hypothalamic nucleus/area
Dorsomedial nucleus
Arcuate nucleus
Anterior and preoptic nucleus functions with respect to temperature regulation
Contain groups of neurons within the hypothalamus that respond to changes in blood temperatures and pyrogen levels
If either gets too high, sends information to brainstem and spinal cord intimating vasodilation and perspiration
Posterior nucleus functions with respect to temperature regulation
Contains groups of neurons within the hypothalamus that respond to decreases below normal body temperature
Act the same way as anterior and preoptic except instead the results are vasoconstriction, increased heart rates, shivering, and elevation of metabolic rates (conserve heat)
What are major arterial branches supplying the diencephalon?
Posterior communicating
Anterior choroidal
both are branches from the ICA
Posterior communicating artery
Arises at the level of the optic chiasm And travels posteriorly to join posterior cerebral arteries
Supplies the following:
- hypophysis (pituitary)
- infundibulum
- parts of hypothalamus/thalamus/hippocampus
Anterior Choroidal Artery
Arises near the optic chiasm
Supplies the following
- choroid plexus in the inferior horn of the lateral ventricle
- optic tract
- parts of internal capsule/hippocampus/globus pallidus/lateral portions of thalamus
Thalamogeniculate artery branches
Arise from the posterior cerebral artery bilaterally
Supplies the medial surface of the thalamus and the walls of the 3rd ventricle
Medial and lateral posterior choroidal arteries
Supply
- choroid plexus in 3rd ventricle (tela choroidea)
- choroid plexus
- cerebral peduncle
- fornix
- thalamus
- caudate nucleus
Ventricles of the brain review
Lateral ventricles (1st and 2nd) - connected with and drains into 3rd ventricle via the interventricular foramina (monro)
Third ventricle
- connected with and drains into the 4th ventricle via the cerebral aqueduct (sylvius aqueduct)
Fourth ventricle
- goes into subarachnoid recesses via the median aperture or lateral recesses
- goes into the spinal cord via the central Canal
Boundaries of the lateral ventricles
Frontal (anterior) horn
1) roof = corpus callousum
2) lateral wall = caudate nucleus
3) medial wall = septum pellucidum and the fornix
Body
1) floor = thalamus
2) lateral wall = caudate nucleus
Occipital (posterior) horn
1) lateral wall and roof = tapetum of corpus callousum
2) medial wall = forceps major of corpus callousum and the calcar avis
3) floor = collateral trigone
Temporal (inferior) horn
1) lateral wall = tail of the caudate nucleus
2) medial wall = hippocampal formation
3) rostral end = amygdala
Third ventricle boundaries
Rostral = anterior commissure and lamina terminalis
Floor = optic chiasm and infundibulum
Caudal = Posterior commissure and pineal recesses
Roof = tela choroidea
Boundaries of the 4th ventricle
Floor = flat and is called rhomboid fossa
Roof = tent shaped called fatigium and projects into the cerebellum
not actually surround by many structures
Choroid plexus
Structures that are present in each ventricle and produces roughly 70% of total CSF
- the other 30% is secreted by parenchyma of brain
Lateral ventricles = on medial wall
3rd/4th ventricles = on roof
What makes up the BBB?
Endothelial cells with very tight junctions
Capillary basement membranes
Astrocytes abutting processes (perivascular endfeet)
only allows carrier mediated transport (except CO2)
What are the 7 circumventricular organs?
all are areas of the brain that lack a BBB
Area posterma
Pineal body
Sub commissural organ
Subfornical organ
Organum Vasculosum lamina terminalis (OVLT)
Neurohypophysis (posterior pituitary)
Median eminence
