Olfactory and Limbic system Flashcards
What is the function of the limbic system?
The limbic system acts as an interface between the internal environment of the individual and the external environment. The olfactory system is intimately related to it.
Two major functional roles:
- Learning
- Regulation and translation of our emotional state into appropriate behaviour
What structures are included in the limbic system?
Limbic system includes: cingulate gyrus, hippocampus, parahippocampal gyrus, anterior perforated substance, septal nuclei, uncus and amygdala.
What is the cingulate gyrus?
The curved fold covering the corpus callosum, involved in processing emotions, behaviour regulation and regulation of autonomic motor function.
What is the Parahippocampal (aka hippocampal) gyrus?
A grey matter cortical region of the brain that surrounds the hippocampus, in continuity with the cingulate gyrus, involved in memory encoding and retrieval.
What is the uncus?
An anterior extremity of the parahippocampal gyrus, it is part of the olfactory system, receiving fibres from the olfactory tract via the lateral olfactory stria.
What is the olfactory tract?
Runs on the orbito-frontal surface of the brain, a bilateral bundle of afferent nerve fibers from the mitral and tufted cells of the olfactory bulb that connects to several target regions in the brain, including the piriform cortex, amygdala, and entorhinal cortex.
What is the hippocampus?
Lies in the floor of the temporal horn of the lateral ventricle. Involved in short-term memory and emotional memory e.g. remembers what you were feeling and links it to a sense of smell e.g. petrol, oil, cut grass, flowers.
What is the fimbriae/fornix?
The efferent fibers begin in the hippocampus on each side of the brain as fimbriae; the separate left and right sides are each called the crus of the fornix (plural crura). The bundles of fibers come together in the midline of the brain, forming the body of the fornix.
What are the mamillary bodies?
A pair of small round bodies that are mainly involved in recollective memory. Information about memory begins in the hippocampus, transmits through the fornix to the mammillary bodies.
What is the amygdala?
One of two almond-shaped clusters of nuclei. Involved in the processing of fear, anxiety, reward, and generating emotional responses to stimuli.
What are the association fibres?
Association fibres are axons interconnecting different areas of the cerebral cortex of one hemisphere. Association fibres can be short, connecting for instance the cortex of neighbouring gyri, or long, passing between areas in different lobes of the hemisphere.
All areas of the cortex send and receive both short and long association fibres. These fibres make up part of the white matter.
What is the basal ganglia?
The basal ganglia consists of a number of subcortical nuclei. The grouping of these nuclei is related to function rather than anatomical, these nuclei are spread throughout the brain.
The basal ganglia feeds information it receives from several sources back to the cortex, via the thalamus. In doing so, it acts to modulate and refine cortical activity – such as that controlling descending motor pathways.
What is the role of the basal ganglia?
Its main function is related to motor refinement, acting as a tonically active break, preventing unwanted movements to start. Much of this involves reducing the excitatory input to the cerebral cortex. This prevents excessive and exaggerated movements.
The basal ganglia also plays an important role in modulating cognitive and emotional responses.
What is the caudate nucleus?
Forms the lateral wall of the lateral ventricle, has a head, body and tail. Involved in storing and processing of memories. It works as a feedback processor, which means it uses information from past experiences to influence future actions and decisions. During development, the caudate nucleus is separated from the putamen by descending white matter fibres, which at this level are known as the internal capsule.
What is the lentiform nucleus?
Made up of the grey matter structures globus pallidus (medial) and the putamen (lateral). The putamen is involved in regulation of movements at various stages (e.g. preparation and execution) and influences various types of learning. The globus pallidus is made up of an internal and external portion and is involved in the regulation of voluntary movement. Laterally to the putamen, there is another collection of white matter fibres known as the external capsule.
