Olfactory and Limbic Systems Flashcards
how many olfactory receptors are there
20 million per side
are there synpses in the olfactory epithelium
no - receptors have axons which project directly to the olfactory bulb
describe the olfactory receptor axons
thin, unmyelinated and slow
olfactory receptors life cycle
60 days
where are the first order neurons in the olfactory system
between receptors and the olfactory bulb
what do second order neurons do in the olfactory system
synapse with tufted and mitral cells in the olfactory glomerulus
what is the olfactory bulb formed from
unmyelinated axons of the tufted and mitral cells (bipolar neurons)
what are the principle neurons of the olfactory bulb
mitral and tufted cells
what do amoratic compounds do in the olfactory bulb
recognise particular receptors and travel to a particular golmerulus
what are aromatic compounds
those which contain benzene rings
what is the glomerulus
- basic processing component of olfactory bulb
- polysynaptic structure ensuring converion of specific olfactory synapses to the mitral and tuftal cells
which mediate local and lateral inhibition
- periglomerular cells in the glomerulus
- granular cells in the deeper layer
where is the olfactory tract found
in the olfactory sulcus
what does the olfactory tract contain
axons of mitral and tufted cells
where does the olfactory tract run to
olfactory trigone
where does the lateral olfactory stria project to
olfactory cortex and parahippocampal gyrus (including uncus)
what is the primary olfactory cortex also known as
the piriform cortex
lateral olfactory stria function
conscious awareness of odour
what are uncinate fits preceded by
hallucinations of disagreeable odours
where does the medial olfactory stria project to
septal area
medial olfactory stria function
olfacterovisceral reflexes
where does the intermediate olfactory stria project to
olfactory tubercle
intermediate olfactory stria function
reward behaviours
which olfactory stria is the largest
lateral
what does the anterior commissure do
connects two halves of olfactory system
where is the anterior fissure found
anterior to the columns of the fornix
where is the insula found
deep in sylvian fissure
insula function
receives taste input from the medial part of the ventral posteromedial nucleus of the thalamus
where is the orbitofrontal cortex found
base of the frontal lobe
orbitofrontal cortex function
furthers conscious smell olfactory perceotion
how does the libmic system operate
influences the endocrine system and the autonomic nervous system
functions of limbic system
- controls emotions
- mood
- motivation
- pain and pleasure sensations
three cortical areas contained in limbic system
- septal area
- cingulate gyrus
- parahippocampal gyrus
four deeper structures contained in limbis system
- hyppocampal formation and fornix
- amygdala
- mammillary bodies
- anterior nuclei of the thalamus
how are the limbic structures interconnected
by the papez circuit
papez circuit components
- fornix
- mammillothalamic tract
- stria terminalis
- cingulum
hippocampus function
associative learning and memory
what is caused by damage to hippocampus
amnesia
where does the hippocampal formation project to
mammillary bodies of hypothalamus and spetal nuclei by way of fornix
amygdala function
plays role in reproduction, fear and aggression and modulation of autonomic and neuroendocrine systems
what do lesions to the amygdala cause
docile behaviour
what does stimulation to the amygdala cause
rage
kulver-bucy syndrome
- ignore social conventions
- caused by bilateral lesions of anterior temporal lobe
what is the amygdala connected to
- directly to thalamus
- directly to neocortex
- hypothalamus by stria terminalis
septal area components
- septal nucleus
- septum pellicudum
- small portion of neocortex that forms part of limbic lobe
what is the septum pellucidum
membrane between the two lateral ventricals
what is the septal area connected to
hypothalamus and hippocamus (fornix)
septal area functions
- relief of fear
- docile behaviour
- stress
what do lesions to the septal area cause
rage and aggressive behaviour
where is the cingulate gyrus found
overlying corpus callosum
cingulate gyrus connections
- anterior nuclear group of thalamus by thalamic radations
- hypothalamus by mammillothalamic tract
cingulate gyrus function
control of emotional and visceral responses, agressive behaviour
thalamus
- connects brainstem to cerebrum
- relay centre - provides a means by which sensory information can gain access to limbic system
hypothalamus
- Because of its interconnections with other limbic structures, stimulation of the hypothalamus produces many of the behaviours seen with the stimulation of other limbic sites
- Stimulation reveals rage and aggression sites as well as docile behaviour
what can acquired disorders of the limbic system cause
- violence
- suicidal behaviour
- agitation
- mood swings
neuropsychiatric disorders caused by damage to the limbic system
- anxiety
- schizophrenia
- psychopathic disorders
