Limbic system Flashcards
What makes up the olfatory epithelium?
- bipolar olfactory neurones (cranial nerves going through the cribiform plate)
- sustentacular cells
- basal cells
Progressive loss of with age = loss of smell (anosmia)
See diagram of olfactory bulb
See diagram
Describe the olfactory system
1) Olfactory bulb (mitral cells)
2) Olfactory tract
3) Olfactory stria (medial and lateral)
4) Piriform cortex (medial temporal lobe) and orbitofrontal cortex
5) Connections to brain stem promote autonomic responses
See diagram
Prodromal auras - in patients with epilepsy
What is the limbic system?
Rim or limbus of cortex adjacent to corpus callosum and diencephalon. Structurally and functionally interrelated areas as a single functional complex
System responsible for processes aimed at survival of the individual
What processes are aimed at survival?
1) Maintenance of homeostasis
2) Agonistic (defence and attack) behaviour
3) Sexual and reproductive behaviour
4) Memory
What are the structures that make up the limbic system?
Frontal lobe - personality Thalamus - anterior part Hippocampus - memory Amygdala Hypothalamus - homeostasis Olfactory bulb Singulate cortex
Draw the Papez circuit
See diagram. Involved in emotional experience and response
What are the main connections of the hippocampus?
Afferent: Perforant pathway
Efferent: Fimbria/fornix = projects to the mammillary bodies.
What are the functions of the hippocampus?
Memory and learning.
Problems with the hippocampus results to the Alzheimer’s disease, epilepsy.
Hippocampus lies on the floor of the ventricles.
Describe Alzheimer’s anatomical progression?
Early - Hippocampus and entorhinal cortex. Short term memory problems
Moderate - Parietal lobe. Dressing apraxia
Late - Frontal lobe. Loss of executive skills
What are the main connections of the amygdala?
Afferent: olfactory cortex, septum, temporal neocortex, hippocampus, braintstem
Efferent: Stria terminalis to the hippocampus
What are the functions of the amygdala?
Fear & anxiety
Fight or flight
Clinical Kluver-Bucy syndrome
The amygdala is found in the medial temporal lobe
Describe Kluver-Busy syndrome?
Bilateral temporal lobectomy
1) Hyperorality
2) Hypersexuality
3) Loss of fear
4) Visual agnosia
Which structures are shown to be associated with aggression?
Hypothalamus
Brainstem (periaquaductal grey)
Amygdala
5-HT(serotonin) in raphe nuclei just beneath the periaqueductal grey
What are the main connections of the septal nuclei?
Afferent: Amygdala, olfactory tract, hippocampus, brainstem
Efferent: Stria medularis thalami, hippocampus, hypothalamus
