Diencephalon Flashcards
diencephalon
-one division of the _____
developmental vesicle, the prosencephalon
what is the other part of the prosencephalon
telencephalon, or the cerebral hemisphere
diencephalon divisions
thalamus
hypothalamus
epithalamus
subthalamus
metathalamus
-what does this refer to?
refers specifically to the medial and lateral geniculate nuclei that are relaying auditory and visual signals to the respective cortical regions
what is the largest portion of the diencephalon
thalamus
thalamus
-describe
complex group of nuclei interposed between the cortex and lower centers of the brain stem
thalamus
-function in regard to sensory information
receives ascending sensory information from sensory pathways, processes that information, and relays it to the cortex
thalamus
-relation to motor systems
intimately associated with the motor systems - in particular with the basal ganglia, cerebellum, and motor cortex
other functions of the thalamus (outside of ascending sensory and motor information)
some nuclei receive and return cortical information
nuclei specific to the reticular activating system
function of cortical information going through the thalamus
very integrative information, rather than specific sensory or motor information
function of reticular activating system
helps regulate our attention and awareness to specific experiences, while reducing other things that could interfere with our attention
how many thalami does the brain have?
2
thalamus
- shape
- location
- function with respect to…
egg-shaped nuclear masses
one on each side of the third ventricle
function with respect to reciprocal connections with the ipsilateral cortex
how can the thalamus be divided?
fibers layers
nuclear subdivisions
fiber layer subdivisions of the thalamus
internal medullary lamina
external medullary lamina
nuclear subdivisions of the thalamus
anterior group medial group lateral group metathalamic group intralaminar group reticular coat
thalamus: anterior group
- related to…
related to limbic system
thalamus: medial group
- related to…
a number of systems, but the primary access to prefrontal cortex
thalamus: lateral group
- function
- divided into…
relay nuclei for somatoselsory and motor cortical areas
divided into a dorsal and ventral tier
thalamus: metathalamic group
- which nuclei
lateral and medial geniculate nuclei
thalamus: intralaminar group
- which nuclei?
centromedian nucleus that is related to the RF
thalamus: reticular coat
- what is it?
outer-most shell of the thalamus (not a part of the RF)
how many nuclei in thalamus
51
thalamus: medial group
- what is the major nucleus
dorsomedial nucleus
thalamus: lateral group
- major areas within dorsal tier
- major areas within ventral tier
- -function of these nuclei
dorsal -pulvinar ventral -VPM -VPL -VL -VA -these nuclei relay sensory and motor information
thalamic reticular coat function
acts in gating efferent thalamic information
functions of thalamus
gated relay for transmission of all sensations (except olfaction) for conscious perception
chief integrating center for all sensory information
plays dominant role in maintenance and regulate of the state of consciousness, alertness and attention
integrative center for motor activity - basal ganglia and cerebellum
describe awareness
area of affect - deals with emotion, pain, agreeableness
highly subjective
functional groupings of thalamic nuclei
cortical relay nuclei
association nuclei
nonspecific nuclei
reticular thalamic nucleus or reticular coat
cortical relay nuclei
-function
receive highly ordered sensory and motor information
relay this information in an accurate manner (maintaining topographic, tonotopic, visuotopic organization) to specific sensory motor cortices (i.e. VPM, VPL, VA, VL, LGN, MGN)
association nuclei
- receive little…
- have extensive…..
- receive…
little or no direct afferents from sensory/motor pathways
have extensive intrathalamic connections and receive afferents from association cortical regions (non-primary sensory or motor) and other subcortical nuclei (limbic, reticular formation)
association nuclei
- send projections to…
- what do we call this?
send projections back to the same association cortices they have received information from (mostly frontal, parietal, and temporal lobes)
-pulvinar
-dorsomedial
-dorsal tier of the lateral group
referred to as reciprocal corticothalamic and thalamocortical connections
nonspecific nuclei
-location
intralaminar nuclei which are located within the internal medullary lamina
nonspecific nuclei
-function
associated with behavioral arousal and sensory/motor integration, sleep
nonspecific nuclei: CM thalamic nucleus
- receives
- function
receives efferents from the medial division of the reticular formation via the central tegmental tract
helps direct what part of cortex needs to be more active by participating in gating of specific information to the cortical region for that particular function
-I believe he said dysfunction of this is thought to be related to disorders like ADHD
reticular thalamic nucleus or reticular coat
- named for…
- function
named for its thin spotty look as it lies over the lateral aspect of the thalamus
functions as an inhibitory feedback regulator of thalamic neuronal activity-gating of sensory information
-[figure: model for gating mechanism; role of CM and reticular thalamic nucleus]
thalamic pain syndrome
-origin type…
usually vascular in origin
thalamic pain syndrome
-if thalamogeniculate artery is injured, how can it happen and what happens?
due to loss of connections at the thalamic level or cortical level
pain sensations cannot be interpreted accurately
-ability to discriminate bewteen an irritating stimulus vs. a painful one becomes blurred
thalamic pain syndrome
-which regions are involved
very broad scope of regions involved in the “increased” perception of pain
thalamic pain syndrome
-what can cause the “increased” perception of pain
irritative stimuli such as an intervertebral disc or radiculopathy
more centrally mediated changes to circuitry as a result of stroke, TBI, SCI
thalamic pain syndrome
-central sensitization of pain has been shown to result in…
heightened cortical responses from the thalamus, in the cingulate gyrus (limbic or emotion), parietal lobe, and prefrontal cortex
thalamic pain syndrome: heightened response
- begins at…
- can involve
begins at synapse in the dorsal horn
can involve more than just the transfer of noxious sensations to ultimately affect non-noxious stimuli such as touch
thalamic pain syndrome: how is the heightened response seen clinically?
seen as hyperalgesia or allodynia
related to pain: anterolateral system consists of ____
at least five different parallel pathways all carrying the sensation encoded from free nerve endings
anterolateral system targest
lateral spinothalamic tract
-carries the sensation through the VPL (ventrolateral thalamic nucleus) to reach the primary somatosensory cortex
other pathways go to RF, other thalamic nuclei projecting to other cortical regions
-limbic system and prefrontal or emotional centers of the brain
function of the differences in the targets of the anterolateral system information
yield both the location and quality of the pain along with an emotional construct
-this combination is what a person perceives as pain
what is important to remember about pain?
perception is reality, even if you don’t think the person should be feeling any pain
without the specifics of the stimulus being perceived within primary somatosensory cortex, the emotional brain can…
make the stimulus seem extremely noxious
thalamic pain syndrome: changes in stimulus thresholds
- elevated for…
- lowered for…
elevated for tactile and position sense
lowered for nociceptive stimuli
thalamic pain syndrome: at threshold, what happens
sensations are exaggerated, exceptionally unpleasant
pin prick leads to severe burning pain
music leads to unpleasant responses
thalamic pain syndrome
-also characterized by (outside of stimulus threshold changes and sensation exaggeration)
spontaneous pain
emotional instability
thalamic pain syndrome: emotional instability examples
inappropriate laughing or crying
altered gating of emotion to cortex
pseudobulbar affect
-stroke patients with brainstem and thalamic lesions
hypothalamus
-function
responsible for homeostatic influences necessary for life
- cardiorespiratory
- thermoregulation
- metabolic
- water resorption
- digestive activity
we think of the hypothalamus primarily from a _____ point of view with respect to _____
-this activity is manifested by…
from a hormonal view with respect to growth, sexual maturity, and cycles
-now even thinking about stomach proteins affecting feeding behaviors
this activity is manifested by control or influence over the pituitary gland through hormonal feedback mechanisms
what else influences the ANS apart from the hypothalamus
-how
rich nervous system connectional scheme that influences the ANS at the level of the brainstem (parasympathetic) and spinal cord (sympathetic - T1-L2; parasympathetic: S2-S4)
hypothalamus is also influenced by…
higher cortical centers
-primarily limbic system and prefrontal cortex
lower centers such as RF
limbic system effect of effect on hypothalamus
influences the hypo and thus the ANS effecting cardiovascular, respiratory and emotional reactions to ongoing situations
-embarrassment, fear, anxiety
most notable effect of hypothalamic influences on behavior are noted following _____
TBI or even some stroke patients
hypothalamus: with lost of connections from the emotional brain (limbic system, orbital part of prefrontal cortex), what happens?
- why?
normal stressors can and are responded to in an angry or aggressive manner
-these cortical areas play a large role in how we interpret stressors in our daily lives
what is the typical output to a stressor
a strategy of how to adjust to the stressor
when the connectional interface that typically responds to a stressor is disrupted, what happens?
the drive through the hypothalamus yields the image of rage, aggression, or defensive postures
in animals, stimulation of the medial hypothalamus can result in…
rage behaviors such as growling, attacking, piloerection, dilated pupils
autonomic control areas
- looked at as…
- what are their names?
looked at as "UMNs" of the ANS names -anterior hypothalamus -lateral hypothalamus -ventromedial hypothalamus
anterior hypothalamus
-related to…
septal region of limbic system
medial hypothalamus
- drives…
- -these are responsible for…
deives the specific parts of the ANS responsible for the motor output of a majority of the motor behaviors -piloerection -dilated pupils -increased salivation
