Diencephalon Flashcards
Lecture 8
diencephalon
- most caudal portion of cerebrum
- develops from prosencephalon
- consists of: epithalamus, thalamus, hypothalamus, subthalamus
diencephalon boundaries
anterior - anterior commissure + lamina terminalis
posterior - posterior commissure
lateral - internal capsule
medial - third ventricle
superior - transverse cerebral fissure
inferior - subarachoid space, optic chiasm, mammillary body
epithalamus
located on/near thalamus
- habenular nuclei
- pineal gland
habenular nuclei
2 of them, path for basal ganglia and limbic system communication with reticular formation, connected by habenular commissure
pineal gland
circadian and circannual rhthyms
thalamus
2-egg-shaped nuclear mass with a posterior appendage, connected by interthalamic adhesion (massa intermedia)
hypothalamus
part of limbic system, controls and integrates the functions of the ANS and endocrine system
hypothalamus functions (HEAL)
Homeostasis
Endocrine
Autonomic
Limbic
subthalamus
located beneath the thalamus, basal ganglia functions
- subthalamic nucleus
- zona incerta
subthalamic nucleus
lens-shaped, biconvex structure, interconnected with basal ganglia
thalamus boundaries
anterior - interventricular foramen
posterior end overlaps midbrain
superior - transverse cerebral fissure
inferior - hypothalamic sulcus
neighbouring structures of thalamus
lateral aspect forms bulk of medial aspect of posterior limb of internal capsule
medial aspect forms bulk of lateral walls of third ventricle
ventral aspect - “rests” on hypothalamus
dorsal aspect - forms floor of third ventricle
hypothalamus boundaries
anterior - lamina terminalis, anterior commisure to optic chiasm
posterior - posterior commissure, mammillary body
superior - hypothalamic sulcus
medial - third ventricle
lateral - internal capsule
hypothalamus medial-lateral zones (from third ventricle to internal capsule)
1) periventricular zone -in wall of third ventricle
2) medial zone - contains series of nuclei
3) lateral zone - lateral to fornix
hypothalamus longitudinal divisions (from lamina terminalis to posterior commissure)
1) anterior region - optic chiasm, preoptic area
2) tuberal region - tuber cinereum (inferior edge), continuous with infundibulum stalk
3) posterior region - mammillary bodies
pituitary gland
consists of posterior pituitary (neurohypohysis) and anterior pituitary (adenohypophysis)
posterior pituitary
sections:
- posterior lobe
- infundibulum
function: secretes hormones into the bloodstream
infundibulum
connects hypothalamus and posterior pituitary
anterior pituitary
sections:
- distal, tuberal, intermediate
function: releasing and inhibiting hormones secreted in capillaries in median eminence, carried via hypophyseal portal vessle to ant. lobe where they release or inhibit other hormones
hypothalamic nuclei
1) preoptic
2) supraoptic
3) paraventricular
4) arcuate
5) anterior
6) posterior
7) ventromedial
8) lateral complex
9) suprachiasmatic
10) dorsomedial
11) mammillary body
preoptic nucleus (Pr)
region: preoptic (anterior)
zone: medial and lateral
function: thermoregulation, fluid balance
- water retention: projects to SO and PV nuclei
- thermoregulation: receives skin and organs temperature, autonomic and behavioursal change
supraoptic nucleus (SO)
region: anterior
zone: medial
function: fluid balance (posterior pituitary)
- releases either ADH (increased ADH leads to water retention) or oxytocin
paraventricular nucleus (PV)
region: anterior
zone: medial
function: fluid balance (posterior pituitary)
- releases either ADH (increased ADH leads to water retention) or oxytocin
arcuate nucleus (Ar)
region: tuberal
zone: medial
function: main control of ant. pituitary, feeding
- receptors for ghrelin (+ feeding behaviour)
- receptors for leptin (- feeding behaviour)
anterior nucleus (An)
region: anterior
zone: medial
function: thermoregulation (cools you down)
- activates heat dissipation
posterior nucleus (Po)
region: posterior
zone: medial
function: thermoregulation (keeps you warm)
- heat conservation
ventromedial nucleus (VM)
region: tuberal
zone: medial
function: appetite
- satiety
lateral complex nucleus (L)
region: anterior, tuberal, posterior
zone: lateral
function: appetite
- hunger
suprachiasmatic nucleus (Sc)
region: anterior
zone: medial
function: mediates circadian rhythyms
- retina and melatonin (pineal gland)
dorsomedial nucleus (DM)
region: tuberal
zone: medial
function: emotion (rage)
mammillary body/nucleus (MB)
region: posterior
zone: medial
function: memory (limbic) and recognition
hypothalamus connections
- limbic system
- pituitary gland
- visceral and somatic nuclei and areas
corticohypothalamic fibres
cortext to hypothalamus, from septal nuclei and other limbic cortical areas
hypothalamocortical fibres
hypothalamus to cortext, to septal nuclei and widespread
hippocampohypothalamic fibres
hippodampus to hypothalamus, through fornix
hypothalamohippocampal fibres
hypothalamus to hippocampus, through fornix
mammillotegmental tracts
mammilary body to midbrain reticular formation
mammillothalamic tracts
mammillary body to anterior (A) thalamus
amygdalohypothalamic and reciprocal fibers
stria terminalis, ventral amygdalofugal pathway (VAP)
brainstem - hypothalamic and reciprocal fibres
from/to brainstem and spinal cord
retinohypothalamic fibres
retina to hypothalamus - circadial rhythms
hypothalamus connection to pituitary gland
adenohypohysis (ant.) - vascular control, neurons from arcuate nucleus
neurohypophysis (post). - neural control, neurons from supraoptic and paraventricular
thalamic divisions
1) anterior
2) medial
- midline nuclei are located on medial surface
3) lateral
internal and external medullary lamina
internal separates thalamic divisions
- intralaminar nuclei
external is outside thalamic divisions
- reticular nuclei
major nucleus of anterior thalamus
anterior (A)
major nucleus of medial thalamus
dorsomedial (DM)
nuclei of lateral thalamus - dorsal tier
1) lateral dorsal (LD)
2) lateral posterior (LP)
3) pulvinar (PUL)
nuclei of lateral thalamus - ventral tier
1) ventroanterior (VA)
2) ventrolateral (VL)
3) ventroposterior lateral (VPL)
4) ventroposterior medial (VPM)
5) lateral geniculate nucleus (LGN)
6) medial geniculate nucleus (MGN)
role of thalamic nuclei
regulate/process and relay info to cerebal cortex for all senses (except olfaction)
specific vs regulatory nuclei
specific: one principle source
ex. optic nerve to LGN
regulatory: large array of neurons
ex. visual cortex to LGN
categories of thalamic nuclei
1) relay nuclei
2) association nuclei
3) other - intralaminar and midline nuclei
4) reticular nuclei
relay nuclei categories
a) motor relay nuclei - VA and VL
b) sensory relay nuclei - VPL and VPM
c) auditory relay nucleus - MGN
d) visual realy nucleus - LGN
e) limbic relay nuclei A and LD
VA and VL
output: motor areas - motor cortex, premotor cortex, supplementary motor cortex
input: superior cerebellar peduncles, basal ganglia
VPL and VPM
output: somatosensory cortex, sensations to consciousness
input: medial lemniscus, spinothalamic tract, central tegmental tract (taste - only VPM)
- body: VPL (think L for legs)
- face: VPM
MGN
output: auditory cortex, hearing
input: inferior colliculus, lateral lemniscus
LGN
output: visual cortex, visual info
input: optic tract
anterior nucleus (A)
output: cingulate gyrus, emotional tone, certain memory mechanisms
input: mammillothalamic tract
lateral dorsal (LD)
output: cingulate gyrus
input: hippocampal inputs - no specific tract
association nuclei
dorsalmedial nucleus (DM), pulvinar (PUL), and lateral posterior (LP)
dorsalmedial nucleus (DM) (thalamus)
thalamus
output: prefrontal cortex, prefrontal functions such as forethought, decision-making based on predictions and incentives
input: prefrontal cortex, olfactory, limbic system
pulvinar (PUL) and lateral posterior (LP)
integration of info from diff. areas, formation of complex behavioural responses in response to visual info (dorsal and ventral streams)
pulvinar input/output: parietial, occipital, temporal lobes
LP input/output: parietal lobe
midline and intralaminar nuclei
mediate global changes to the cerebral cortex, including waking/consciousness, pain perception, and selective attention
output: multiple areas of cortex, basal ganglia, limbic structures
input: multiple areas of brain
internal capsule boundaries
boundaries
boundaries:
- lateral: lentiform nucleus
- medial: head of caudate nucleus, thalamus, hypothalamus
almost all traffic to and from the cerebral cortex passes through the internal capsule
limbs of internal capsule
1) anterior limb
2) genu
3) posterior limb
4) retrolenticular
5) sublenticular
anterior limb of IC
between lenticular nucleus and head of caudate nucleus
info carried:
- ant. nucleus (A) to cingulate gyrus
- DM to prefrontal cortex
genu of IC
junction between ant. and post. limbs
post. limb of IC
between lenticular nucleus and thalamus
info carried:
- VA/VL to motor areas
- motor areas to brainstem and spinal cord
- VPL/VPM to somatosensory cortex
retrolenticular and sublenticular limbs of IC
retro: posterior to lentiform nucleus, contains superior fibres of optic radiations
sub: inferior to lentiform nucleus, continuous with retrolenticular, contains auditory radiation and inferior fibres of optic radiations
info carried:
- MGN to auditory cortex
- LGN to visual cortex
- PUL/LP to parietal-occipital-temporal cortex
