LIMBIC SYSTEM Flashcards
RHINENCEPHALON (SMELL BRAIN) structures
Olfactory nerve rootlets Olfactory bulb Olfactory tract Olfactory striae Primary olfactory cortex
limbic lobe components
Subcallosal gyrus, inferior to the genu and rostrum of the corpus callosum, just anterior to the lamina terminalis
Cingulate gyrus
Isthmus of the cingulate gyrus, posterior and inferior to the splenium of the corpus callosum
Parahippocampal gyrus (and the underlying hippocampal formation and dentate gyrus)
Uncus
The limbic lobe is formed of ______(hippocampal formation and dentate gyrus),_____ (rostral parahippocampal gyrus and uncus), and ______ (cingulate gyrus).
archicortex
paleocortex
juxtallocortex or mesocortex
The circuit consisted of outflow of impulses from the hippocampus via the fornix
to the mamillary bodies of the hypothalamus;
from there, via the mamillotha-la-mic tract, to the anterior thalamic nucleus;
and, via the thalamocortical fiber system, to the cingulate gyrus, from which impulses returned to the hippocampus via the entorhinal area
Papez circuit
Parts of the hippocampus
hippocampus dentate gyrus (fascia dentata), and subiculum
The ______ is the part of the parahippocampal gyrus that is in direct continuity with the hippocampus.
subiculum
Laminations of the hippocampus
the molecular layer,
the pyramidal cell layer,
and the stratum oriens (polymorphic layer).
hippocampus has been subdivided further into fields:
CA1: the largest hippocampal field in humans
CA2
CA3
CA4: CA4 constitutes the transition zone between the hippocampus and the dentate gyrus.
pyramidal neurons are highly sensitive to anoxia and ischemia in this area and because it is the trigger zone for some forms of temporal lobe epilepsy
Field CA1 (also known as Sommer’s sector and the vulnerable sector)
_______have been referred to as resistant sectors because they are less sensitive to anoxia. ________ (the Bratz sector) is also called the medium vulnerability sector because of its medium sensitivity to hypoxia.
CA2 and CA3
CA4
There are basically two types of neurons in the hippocampus:
the principal neurons (pyramidal cell) and the intrinsic neurons (polymorphic cell, basket cell)
They are the only neurons with axons which contribute to the outflow tract from the hippocampus.
Principal Neurons.
They are inhibitory (GABAergic) to pyramidal cell activity
intrinsic neurons
Layers of the dentate gyrus/ subiculum
molecular layer: continuous with that of the hippocampus
a granular cell layer: small, densely packed granular cells whose axons form the mossy fiber system which links the dentate gyrus and the hippocampus
and a polymorphic layer: include pyramidal and basket cells
The bulk of extrinsic input to the hippocampal formation comes from the:
entorhinal area (Brodmann’s area 28) of the parahippocampal gyrus and, to a lesser extent, the septal area
Fibers from the septal nuclei reach the hippocampus via the __________
fornix.
Axons of small pyramidal neurons (granule cells) in the dentate gyrus reach the hippocampus via the_______
mossy fiber pathway.
Fibers from the________originate from cell groups in the vicinity of the mamillary body and exert a strong inhibitory influence on the hippocampus.
hypothalamus
Thalamic input to the hippocampus has been shown to originate in the ________
anterior thalamic nucleus.
Noradrenergic fibers from the locus ceruleus have been traced to the _________
hippocampus and the dentate gyrus.
The ____________ inputs exert a modulatory effect on memory function in the hippocampus.
noradrenergic, serotoninergic, and dopaminergic
The output from the hippocampal formation consists of axons of pyramidal neurons in the _________
hippocampus and subiculum
The _______is a fiber bundle that reciprocally connects the hippocampal formation with a number of subcortical areas, including the thalamus, the hypothalamus, and the septal region.
fornix
Stimulation and ablation of the hippocampus give rise to changes in _______
behavioral, endocrine, and visceral functions.
hippocampal ablation results in
results in a loss of recent (60 s) memory and the inability to store newly learned facts (anterograde amnesia).
___________memory includes episodic, semantic, and familiarity-based recognition
Declarative (associative)
___________resemble almonds in shape and are located in the tip of the temporal lobe beneath the cortex of the uncus and rostral to the hippocampus and the inferior horn of the lateral ventricle.
amygdala
two groups of nuclei of the amygdala
the corticomedial and central : OLDER, maintains connections with the phylogenetically older regions of the central nervous system, such as the olfactory bulb, hypothalamus, and brain stem.
and the basolateral: connections with the cerebral cortex
Neurotransmitters of the amygdala
acetylcholine, gamma-aminobutyric acid (GABA), noradrenaline, serotonin, dopamine,substance P, and enkephalin.
Afferent pathways of the amygdala
- cortical input from the prefrontal, temporal, occipital, and insular cortices,
(2) the thalamus (dorsomedial nucleus),
(3) the olfactory cortex, and
(4) cholinergic input from the nucleus basalis of Meynart
Output from the amygdala is conveyed via two main pathways:
(1) stria terminalis (dorsal amygdalofugal pathway) and (
2) ventral amygdalofugal pathway (ventrofugal bundle
Functions of the amygdala
- AUTONOMIC EFFECTS
- ORIENTING RESPONSE to novel agents.
- EMOTIONAL BEHAVIOR AND FOOD INTAKE
- FACIAL EXPRESSION
- AROUSAL RESPONSE
- SEXUAL ACTIVITY: Bilateral lesions of the amygdala produce hypersexuality and perverted sexual behavior.
- MOTOR ACTIVITY
Lesions in the ___________of the amygdala result in aphagia, decreased emotional tone, fear, sadness, and aggression.
Lesions of the _________, by contrast, produce hyperphagia, happiness, and pleasure reactions
corticomedial nuclear group
basolateral nuclear group
Stim-ulation of the ________of the amygdala is associated with fear and flight. Stimulation of the _________group produces a defensive and aggressive reaction.
basolateral nuclear group
corticomedial nuclear
amygdalar stimulation differs from that elicited by hypothalamic stimulation in its ____ buildup and subsidence upon the onset and cessation of stimulation
gradual
Whereas the ________participate primarily in constructing detailed perceptual representation of faces, the _______is required to link the perception of the face to the retrieval of knowledge about its emotional and social meaning.
extrastriate visual cortices
amygdala
Bilateral ________damage in humans is associated with impaired recognition of facial expressions.
amygdalar
Stimulation of the ________produces an arousal response that is similar to but independent of the arousal response that follows stimulation of the reticular activating system of the brain stem
basolateral nuclear group of the amygdala
Stimulation of the _________ produces complex rhythmic movements related to eating, such as chewing, smacking of the lips, licking, and swallowing.
corticomedial nuclear group of the amygdala
The amygdaloid projections to the hy-pothalamus via the ventral amygdalofugal pathway seem to be essential___________
for fear-related behavior.
2 divisions of the septum
the septum pellucidum: It is made up of glia and lined by ependyma.
and the septum verum: ventral to the septum pellucidum
________provides a site of interaction between limbic and diencephalic structures.
septum
functions of the septum
EMOTIONAL BEHAVIOR: produce rage reactions and hyper-emotionality
WATER CONSUMPTION: concerned with water balance in response to changes in total fluid volume (lesion inc in water consumption)
ACTIVITY: high initial state of activity in response to a novel situation.
LEARNING: Animals with septal lesions tend to learn tasks quickly and perform them effectively once they have been learned.
REWARD
AUTONOMIC EFFECTS: inhibitory effect on autonomic function
Destruction of the septal nuclei gives rise to behavioral overreaction to most environmental stimuli. Behavioral changes occur in sexual and reproductive behavior, feeding, drinking, and the rage reaction.
septal syndrome
Afferent limb of the limbic system
The afferent limb of the loop consists of collaterals to the limbic system from the pathway connecting neocortical association cortices with the prefontal cortex.
The efferent limb:
of the loop consists of projections from the limbic centers to the prefrontal association cortex
