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Rhinencephalon is part of which vesicle?
telencephalon
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What system is the rhinencephalon involved with?
olfactory system (smell)
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Is the rhinencephalon an original structure of the brain?
yes
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What is the main structure of the rhinencephalon?
olfactory bulbs
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What CN are the olfactory bulbs a part of?
CN 1 pairs
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What are the olfactory bulbs?
outgrowth of the brain that lie on cribriform plate
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The the cribriform plate is part of which bone in the skull?
ethmoid
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The cribriform plate has what to allow nerves to pass through?
holes
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The olfactory bulbs receive neurons from what?
nasal mucosa
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What type of neurons are from the nasal mucosa?
1st order sensory
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The 1st order sensory neurons from the nasal mucosa synapse with what?
2nd order sensory neurons
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Where do 2nd order sensory neurons originate from?
olfactory bulbs
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2nd order sensory neurons (cell bodies in bulbs) travel through what?
olfactory nerve
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The olfactory nerve enters the rhinencephalon and:
bifurcates
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The olfactory nerve bifurcates into:
lateral olfactoray stria and medial olfactory stria
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Where does the lateral olfactory stria terminate?
uncus of the parahippocampus
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What lobe is the uncus in?
temporal lobe
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What is the parahippocampus?
primary functional area--smell
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Where do the 2nd order neurons of the lateral olfactory stria go to?
to uncus
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What do the medial olfactory stria head towards?
anterior perforated substance (cortex)
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Some of the 2nd order neurons in the rhinencephalon may cross over to:
contralateral side through anterior commissure to go to uncus or anterior perforated substance
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Smell info coming into the right nostril goes to:
both lobes to be perceived
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Any general sensation or special senses has to reach what?
cortex and goes through the thalamus first
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Does smell go through the thalamus before reaching the cortex?
no, it is a survival evolution
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Why is smell unique?
- it is the only sensation that is not first processed by the thalamus to before going to the cortex to be perceived
- Goes DIRECTLY to cortex. Responds to danger quickly
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What system is the rhinencephalon involved with?
- limbic system
- smell ahs a lot to do with emotions, can make you happy, sad, sick
- subtle smells can influence behavior
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Which vesicle of the brain is the diencephalon a part of?
forebrain
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What does the diencephalon contain?
thalami
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Where are the thalami?
in an area rostrol to brainstem
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What percentage of the brain is the diencephalon?
- 2%
- very small, but does a lot for you in terms of function
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Where is the diencephalon?
between posterior commisure caudally to interventricular foramen rostrally
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What bounds the diencephalon laterally?
- posterior limb of internal capsule
- tail of caudate nucleus
- stria terminalis
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What does the 3rd ventricle separate the diencephalon into?
right and left halves, making it a bilateral structure
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What are the 4 parts of the diencephalon?
- epithalamus
- thalamus
- hypothalamus
- subthalamic region
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What is the most posterior aspect of the diencephalon?
epithalamus
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What are the parts of the epithalaums?
- habenular trigone
- pineal body
- roof of 3rd ventricle
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What is the habenular trigone?
triangle shaped nuclei that belong to epithalamus of the diencephalon
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What type of fibers does the habenular trigone have?
afferent and efferent connections to other parts of the brain
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What other parts of the brain is the habenular trigone connected to?
hypothalamus, thalamus, and basal ganglia
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The afferent and efferent connections in the habenular trigone are classified as:
reciprocating
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Where are connections w/in the habenular trigone found?
in stria medullaris
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Stria medullaris:
fibers connecting to hypothalamic, thalamic, afferent and efferent to basal ganglia; rostral to habenula
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What is the function of the habenular trigone?
- not clear
- plays minor role in limbic system
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The habenular trigone is a connecting structure that allows:
4 parts of the brain to communicate
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Where is the pineal body?
- attached to roof of 3rd ventricle
- in region of posterior commissure
- b/w two habenular trigones
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The pineal body plays a major role in:
onset of puberty
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How does the pineal body play a major role in the onset of puberty?
by producing melatonin
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What happens when the pineal body ceases to produce melatonin?
triggers onset of specific relay nuclei
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what are the nuclei found in the pineal body?
- specific relay nuclei
- association nuclei
- subcortical nuclei
- diffuse cortical connection nuclei
- pulvinar nuclei
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Specific relay nuclei:
- r nuclei
- project to and receive fibers (ascending tracts such as the spinothalamic tract and dorsal column) from well-defined cortical areas related to specific functions
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Association nuclei:
- a nuclei
- don't receive fibers from ascending systems, but project to association areas of the brain
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Subscortical nuclei
- sc nuclei
- project to subcortical area (i.e., basal ganglia, red nucleus)
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diffuse cortical connection nuclei:
- dc nuclei
- relay to various areas of the cortex but their destinations are not as specific as r nuclei
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Which nuclei in the pineal body are the largest?
pulvinar nuclei
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When does the pineal body quit functioning?
once puberty has been triggered and begins to calcify around age 40
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What is the pineal body involved with?
- puberty
- circadian rhythm--cyclic rhythm of body responses
- clinical depression (melatonin in pineal body)
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What does melatonin deal with in some animals?
- pigmentation of epidermis
- NOT in humans though
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What lines the roof of the 3rd ventricle of the epithalamus?
epithelial lining the roof is choroid plexus producing CSF
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What is the largest portion of the diencephalon?
thalamus
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What is the ventral boundary of the thalamus?
hypothalamic sulcus
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What is the caudal boundary of the thalamus?
level of posterior commissure and cerebral aqueduct
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What is the rostral boundary of the thalamus?
interventricular foramen
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What is the dorsal boundary of the thalamus?
stria medullaris of epithalamus
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What is the lateral boundary of the thalamus?
posterior limb of internal capsule
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What is the medial boundary of the thalamus?
helps form lateral wall of 3rd ventricle
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What is the thalamus divided into?
right and left halves
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What connects the right and left halves of the thalamus?
massa intermedia
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What is another name for massa intermedia?
interthalamic connection
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What does the massa intermedia cross?
3rd ventricle
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The thalami appear as 2:
obliquely placed oval masses
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The talami are internally composed of:
numerous nuclei
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Describe the nomenclature of the nuclei of the thalamus?
complex and inconsistent
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What are the two types of classification of the thalamus?
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What is the anatomical classification of the thalami based on?
- location
- (ventral nuclei, medial nuclei, ventral posterior lateral oralis, etc)
- approximately 40 classifications
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What do functional classifications of thalamus describe?
what specific nuclei do
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What are the types of functional classifications of the thalamus?
- specific relay nuclei
- association nuclei
- subcortical nuclei
- diffuse cortical connection nuclei
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specific relay nuclei:
- r nuclie
- project and receive fibers from well0defined cortical areas related to specific functions
- receive from ascending tracts such as spinothalamic and dorsal column
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association nuclei
- a nuclei
- do not receive fibers from ascending systems but project to association areas of brain
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subcortical nuclei
- sc nuclei
- project to subcortical areas (basal ganglia, red nucleus, etc.)
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diffuse cortical connection nuclei
- dc nuclei
- relays to various areas of the cortex
- destinations not as specific as R nuclei
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What are the most common nuclei?
R and A nuclei
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What is the pulvinar nucleus?
- anatomically, it belongs to the lateral nuclear group
- functionally it is an R (relay) nucleus
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What is the largest nuclei?
pulvinar nuclei
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What are the two smaller nuclei of the pulvinar nucleus?
- medial geniculate body
- lateral geniculate body
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Medial geniculate body:
- R-type nucleus
- involved w/ perception of hearing and auditory reflexes
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Lateral geniculate body:
- R-type nucleus
- involved w/ perception of vision and visual reflexes
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What are the functions of the thalamus?
- great relay station of the brain
- plays dominant role in maintenance and regulation of consciousness, alertness, and attention
- involved w/ subcortical perception of pain and temperature
- serve as integrative areas for motor function
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Is the thalamus purely a sensory structure?
no, it used to be thought of that way
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Where is all sensory info (except olfaction) processed?
nuclei of the thalamus
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What is included in the thalamus?
internal and external stimuli
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Does the thalamus have secondary input back to the the olfactory cortex?
yes
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What does the thalamus process?
sensory info
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What does the thalamus send sensory info to?
appropriate areas via projection fibers
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Thalamocortical fibers:
corona radiata and internal capsule
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What is the primary sensory integrating structure of the brain?
thalamus
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What allows you to discriminate where pain is coming from and what kind of pain it is?
post-central gyrus
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Where is the actual appreciation of pain?
thalamus
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