Olfaction and the Limbic System

Question 1

Olfactory system receptors

Answer 1

Bipolar cells located in olfactory epithelium of nasal cavity

Question 2

Olfactory first order neurons

Answer 2

receptor cells, nonmyelinated axons that form the olfactory nerve

Question 3

Olfactory second order neurons

Answer 3

mitral cells, form the olfactory tracts

Question 4

Olfactory tract bifurcates to where?

Answer 4

septal area (olfactovisceral reflexes) and piriform cortex (conscious awareness of olfaction)

Question 5

Summary of olfactory pathways

Answer 5

olfactory receptor neurons - olfactory bulb - piriform lobe (conscious perception of smell), hypothalamus and amygdala (motivational and emotional aspects of smell), hippocampus (odor memory)

Question 6

Limbic system functions

Answer 6

1. emotions of importance to survival (self preservation and species preservation)
2. learning and memory

Question 7

Criteria for being included in the limbic system

Answer 7

1. rich innervation by axons containing indoleamine and/or catecholamine neurotransmitters
2. low threshold for seizure activity
3. direct or indirect connections to the hypothalamus

Question 8

Components of the limbic system

Answer 8

hippocampus
cingulate gyrus
amygdala
septal area
portions of the thalamus
piriform lobe
mammillary bodies

Question 9

Function of hippocampus

Answer 9

associative learning and memory (particularly memory acquisition or short term memory)

Question 10

Function of septum

Answer 10

emotions, relief of fear, docile behavior, stress, and autonomic regulation (ex: water/food intake, hibernation, etc.)

• stimulation induces docile behavior
• lesions result in rage and aggressive behavior

Question 11

Functions of amygdala

Answer 11

emotion and memory, social behaviors such as reproduction, fear and aggression, and modulation of the autonomic and neuroendocrine systems

• stimulation induces rage and aggressive behavior
• lesions result in docile behavior

Question 12

Functions of hypothalamus

Answer 12

both docile and rage/aggressive behavior when stimulated

Question 13

Clinical signs of damage to limbic structures

Answer 13

dullness
lethargy
sleepiness
stupor or semicoma
dementia
failure to recognize owners/environment
inability to learn
destructive behavior
irritability or aggressiveness
propulsive pacing or circling