thalamus and hypothalamus Flashcards
sagittal section of brain DIAGRAM
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coronal section of brain DIAGRAM
below lateral ventricles is thalamus, divided by the 3rd ventricle walls and floor of third ventricle is hypothalamus
real coronal section of brain DIAGRAM
diencephalon closely associated with midbrain below (black part directly underneath is substantia nigra) and corticospinal tracts
nuclei vs ganglia DIAGRAM
thalamus is organised into DISCRETE nuclei (grey matter- they are clusters of neurons with similar functions) clusters of neurons in PNS are ganglia, yet nuclei in CNS (APART from basal ganglia- they are clusters of neurons in CNS)
function of thalamus
relay site for all inputs/outputs- inputs/outputs meet at thalamus involved in all sensory sysems apart from smell (olfactory)- either enhances or surpresses signals
explain somatosensory pathway DIAGRAM
touch/proprioception sensed by skin and goes to dorsal root ganglion, then dorsal root of spinal cord primary sensory neurone of posterior/dorsal colum goes up to medulla to graciale nucleus, and crosses over (sensory decussation) and synapses with secondary neurone this goes up to thalamus to ventral posterior lateral nucleus (nucleus that processes all touch/propriception) sensory info then goes to primary somatosensory cortex
intralaminar nuclei DIAGRAM
lamina/line divides discrete nuclei, and within it lies intralaminar nuclei, which go to medial temporal lobe structures (amygdala in front part of temporal lobe, hippocampus behind)
intralaminar nuclei 2 (more about temporal lobe and features of the nuclei and what happens if lost) DIAGRAM
amygdala= emotions eg fear/anxiety, hippocampus memory nuclei mostly glutamatergic neurons ie excitatory - loss of them occurs in parkisons and PSP (progressive supranuclear palsy-rare)
reticular nuclei: features and function
outer part of thalamus, and are mainly GABA-ergic ie inhibitory unlike intralaminar nuclei unlike other nuclei, they don’t affect distant regions, they affect local regions ie other thalamic nuclei- receiving inputs from axons of these nuclei thus they modulate activity of thalamus ie negative feedback
reticular formation- what they are, function, and relation to intralaminar/reticular nuclei
interconnected pathways in the brainstem- areas where function is ambiguous they send projection to base of brain (forebrain nuclei), aka ascending reticular activating system (ARAS)- this system involved in consciousness and arousal (reaction to outside world)- so increased ARAS activity= more awake intralaminar/reticular nuclei receive inputs from ARAS
hypothalamus- what is it and functions, and connections
collection of nuclei with certain functions- also divided by 3rd ventricle connections mostly on same side (ipsilateral)- no decussation, and to ANS AND endocrine system involved in 4 F’s- fighting, fleeing, feeding, mating
paraventricular nucleus
has parvocellular neurons with go to spinal cord, thenvia ANS to kidney, heart and vessels magnocellular neurones go to posterior pituitary where oxytocin/vasopressin are stored
PVN and feeding
PVN involved in feeding- not just alone, receives input from other nuclei involved in feeding lesions cause weight gain
location of suprachiasmatic nucleus DIAGRAM
just above optic chiasm at base of hypothalamus is this nucleus
function of suprachiasmatic nucleus + connections
affects circadium rhythm- has connections to PVN , but also pineal gland via ANS, which secretes melatonin
suprachiasmatic relation to optic chiasm DIAGRAM
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