olfaction and the limbic system Flashcards
olfactory epithelium DIAGRAM
in top of hose-has bipolar olfactory neurones (receptor), then projects up through cribiform plate to olfactory bulb also within epithelium are SUSTENTACULAR cells (support cells) and basal cells (stem cells for regeneration)
what occurs in olfactory bulb DIAGRAM
they synapse with SECOND ORDER olfactory neurons in the GLOMERULUS- then go to brain via OLFACTORY TRACT- this tract splits into two STRIA, which go to PIRIFORM and ORBITOFRONTAL cortex- can then connect to brainstem, which causes salivation as a response
deficit of olfaction
anosmia
what is limbic system DIAGRAM
rim of cortex next to corpus callosum- structurally and functionally interrelated areas considered a single functional complex
what is function of limbic system
involved in SURVIVAL- maintenance of homeostasis, fight or flight behaviour, sexual behaviour, and memory
Papez circuit DIAGRAM
hippocampus projects to mamillary bodies of hypothalamus via fornix- hypothalamus projects to anterior nucleus of thalamus via mamillothalamary tract projections to cingulate cortex, then back to hippocampus via cingulum bundle thus emotional experience ie memories due to hippocampus, emotional expression (how you respond) due to hypothalamus, and emotional colouring (ie how you respond based on previous experiences) due to neocortex- all connected
DIAGRAMS hippocampus- main pathways+ location + shape
main afferent pathway the PERFORANT pathway from ENTORHINAL cortex, main efferent pathway the FORNIX- clinically affected in alzheimers and epilepsy- it’s in medial temporal lobe in inferior horn of lateral ventricle- has seahorse shape
what happens to hippocampus in alzheimers+ progression
shrinkage of hippocampus, as well as enlargement of ventricles in early stages hippocampus affected, in middle stages parietal lobe affected= dressing apraxia (cannot dress), and in late stages frontal lobe damaged= loss of decision making+ personality
amygdala- function, connections, location
fight or flight centre- has connections to olfactory (smell can cause fear), hippocampus, neocrotex- located near hippocampus
issue with amygdala IMPORTANT
issues hear lead to Kluver-Bucy syndrome- loss of fear, hyperorality (putting things in mouth like a baby), hypersexuality, and visual agnosia (can’t recongise objects): also occurs with damage to temporal lobes
structures associated with aggression
hypothalamus, brainstem and amygdala
septal nuclei DIAGRAM
needed for reward, lying between the lateral ventricles
mesolimbic pathway
another dopaminergic pathway (like from substantia nigra to striatum) from midbrain (VTA) to nucleus accumbens, cortex and amygdala
cause of anosmia
early sign of parkisons/alzheimers
hallmarks of alzheimers- macro and microscopic
cortical atrophy, ventricles larger- senile plaques present
