Olfaction and the Limbic System Flashcards
What the three types of cell that makes up the olfactory epithelium?
Bipolar Olfactory Neurones
Sustentacular Cells – support cells mainly providing metabolic support
Basal Cells – there is some regeneration in olfactory neurones
Where is the olfactory bulb found?
Sitting on top of the cribriform plate
Which cells synapse within the olfactory bulb?
The bipolar cells pass their axons through the cribriform plate to synapse with the second order neurones (olfactory bulb mitral cells) in the glomerulus within the olfactory bulb
What structure do the second order neurones form and what does this structure split into?
Olfactory tract
It splits to form the medial and lateral olfactory stria
Where does higher processing of smell take place?
Piriform Cortex
Orbitofrontal Cortex
What is a clinical deficit in the olfactory system called?
Anosmia
What is a common cause of anosmia?
Mid-face trauma
Impact with enough force could cause a fracture of the cribriform plate, shearing the neurones going from the olfactory epithelium to the olfactory bulb
The piriform cortex is found within the temporal lobe. Explain thesignificance of this with regards to epileptic patients.
Epilepsy is often focused in the temporal lobe
This means that some people with epilepsy will experience PRODROMAL AURA (they are made aware of an imminent seizure because they’ll smell something that’s not there)
Neurodegenerative disease is a relatively common cause of anosmia. State two neurodegenerative diseases that could cause anosmia.
Alzheimer’s disease
Parkinson’s disease
What is the limbic system?
A rim of cortex adjacent to the corpus callosum and diencephalon
What are the roles of the limbic system?
Homeostasis (mainly hypothalamic functions such as regulation of food intake and pituitary hormone release)
Agonistic behaviour (fight or flight)
Sexual and reproductive behaviour
Memory
State two important parts of the limbic system that are found within the temporal lobes.
Hippocampus and Amygdala
What circuit are these structures a part of?
Papez Circuit
What is the cortical representation of the limbic system?
Cingulate Cortex
What is the function of the Papez circuit?
It is a neural circuit for the control of emotional expression
Describe/draw the papez circuit.
Hippocampus –> Fornix –> Mammillary Bodies –> Mammillo-Thalamic Tract (MTT) –> Anterior Nucleus of the Thalamus –> Cingulate Cortex –> Cingulum Bundle –> Hippocampus