Olfactory and Limbic System

Question 1

Describe the pathways for olfactory sensation

Answer 1

olfactory n (which is a colection of axons of bipolar nn) goes through cribriform plate to synapse on olfactory bulb, carried through mitral cells (nerves in olfactory bulb) to both ipsi and contralateral anterior olfactory nucleus, also sends nerves straight throught lateral olfactory stria to amygdala and primary olfactory cortex (made of pyriform lobe and entorhinal cortex)

doesn’t synapse in thalamus before entering cortex

Question 2

Describe the clinical features associated with diminished olfactory function

Answer 2

anosmia is a sign of a lesion on ventral brain, like parkinson’s or alzheimer’s

Kallmann syndrome is caused by developmental defect of olfactory and pituitary function, has lack of smell and delayed puberty and sterility

Question 3

Describe the functional significance of the limbic system and its major functional components.

Answer 3

emotions and memory

limbic lobe (anterior cingulate gyrus, subcolossal and parahippocampal gryi)

subcortical centers (amygdala, basal forebrain, septal nuclei–anterior to lamina terminalis)

diencephalic nuclei (anterior thalamus and mamillary bodies)

Question 4

Describe the major anatomical features and functions associated with the cingulate cortex, hippocampus, septum, amygdala, nucleus accumbens and basal forebrain.

Answer 4

cingulate cortex: mediates interactions between cognition and emotion, conflict resolution

hippocampus: made of dentate gyrus (does input of hippo), subiculum (output zone, forms fimbraie), and hippocampus proper (transfers info from dentate to subiculum) overall converts short-term to long term memory
septum: anterior to lamina terminalis, labels sensory stimuli as pleasurable or painful
amygdala: anterior to hippocampus deep to uncus, focuses attention, labels stimuli as positive or neg, causes fear and fight or flight

nucleus accumbens: ventral striatum at junctin of caudate head and putamen, drug addiction

basal forebrain: ventral to anterior commissure, includes substantia innominata, which includes nucleus basalis of Merynert which are cholinergic and lesion causes dementia and alzheimer’s

Question 5

Describe the anatomical correlates and clinical features of Alzheimer disease, Korsakoff’s syndrome, Klüver-Bucy syndrome and the associated limbic structures.

Answer 5

alzheimer’s has damage to substantia innominata and nucleus basalis of Meynert

Korsakoff’s syndrome has damage to limbic system resulting in anterograde amnesia, is caused by chronic alcoholism and thiamine deficiency

Kluver-Bucy syndrome is an amygdala lesion resulting in psychic bindness (seeing but not processing), tameness, hypersexual behavior

Question 6

what’s the term for loss of sense of smell?

Answer 6

anosmia