Limbic System Flashcards
Generally describe the limbic system:
The limbic system is a term used for a number of interconnected cortical regions and subcortical structures that function to serve a number of survival mechanisms.
List 5 cortical structures that are included in the Limbic lobe:
- septal area
- cingulate area
- parahippocampal gyrus
- hippocampus
- other related cortical areas (orbitofrontal cortex and prefrontal cortex)
Describe the septal area:
area surrounding end of rostrum of corpus callosum
What are the associated subcortical nuclei of the limbic system?
- amygdala
- hypothalamus
- septal nuclei
- anterior thalamic group
where is the amygdala located?
located deep to the uncus
Where is the septal nuclei located?
deep to septal cortical region; near the fornix and anterior commisure
List the 4 nerve fiber pathways of the limbic system:
- mamilothalamic tract
- fornix
- stria terminalis
- medial forebrain bundle
The limbic lobe connections are organized as a complex loop. The mamillary bodies connect to the ______________________ via the mamillothalamic tract.
anterior thalamic group
The anterior thalamic group connects to the __________________.
cingulate gyrus
the cingulate gyrus connects to the __________________________.
parahippocampal gyrus
the parahippocampal gyrus connects to the ________________________.
hippocamus
the hippocamus connects to the _______________________ and _______________________ via the ____________.
mamillary bodies
and septal region
via the fornix
Describe the route of the limbic lobe:
mamillary bodies –> anterior thalamic group (via mamilothalamic tract) –> cingulate gyrus –> cingulate gyrus –> parahippocampal gyrus –> hippocampus –> mamillary bodies AND sepatal region (via fornix)
How is the amygdala connected to the limbic circuit?
by way of the connections to the septal region and the hypothalamus via stria terminalis
What are the two afferents of the limbic system?
- cortex
2. reticular formation
In the limbic system, the afferent cortex projects:
to all parts of limbic lobe, amygdala and hypothalamus
In the limbic system, the afferent reticular formation projects:
to all parts of limbic lobe, amygdala and hypothalamus
In the limbic system list two of the efferent locations:
- limbic lobe
2. amygdala
In the limbic system the limbic lobe is efferent and projects to:
all parts of the cortex by way of thalamic gating
and to the hypothalamus and reticular formation
In the limbic system the amygdala is efferent and projects to:
dorsomedial thalamic nucleus, which in turn projects to prefrontal cortex (medial forebrain bundle)
in the limbic system the amygdala is efferent and projects to the brainstem reticular formation nuclei both directly and indirectly via the:
hypothalamus (medial forebrain bundle)
The limbic system generates behaviors necessary for:
preservation of the individual and the species (e.g., motivation, emotion, learning and memory).
In the limbic system, the relationship of anatomy to function is only partially known, but suffice it to say that the influence this system has on the hypothalamus and the autonomic nervous system is very powerful. Lesions of the hippocampus and amygdala must be ____________ to result in major deficits of normal behavior.
bilateral
In the limbic system, unilateral stimulation, however, may result in ____________ behavior.
abnormal
The limbic system has been labeled the 3-F, 1-R system:
(fighting, fleeing, feeding and sexual behavior).
or 4 F’s
(Hippocampus) Attention: What does unilateral or bilateral stimulation produce?
alertness and searching behavior.
What my the proposed circuitry be?
Hippocampus_Attention: unilateral or bilateral stimulation produces alertness and searching behavior
???
remember that alertness and awareness are cycled through the reticular formation as the reticular activating system
(Hippocampus) Memory: loss of recent memory and the inability to form new memories is the result of a ___________ lesion.
bilateral
What type of memories is the hippocampus responsible for, declarative or procedural?
declarative (explicit, facts)
NOT procedural (implicit, motor memory)
The process of consolidation is the transfer of short-term memories into:
long lasting memories
Patient H.M. had ______________ and D.B. had ______________.
epilepsy
limbic encephalitis
(hippocampus) Spatial orientation; there is a “cognitive mapping system” which makes what possible?
possible to compare present spatial situations with those already experienced
(hippocampus) stress projections go to the ________________ hippocampus.
anterior
Stress causes the pathway to the anterior hippocampus to release _____________________________ that then acts at the ______________.
corticotropin releasing factor (CRF)
pituitary.
What does the pituitary release?
adrenocorticotropic hormone (ACTH)
What does ACTH act on? What does this structure then secrete?
What else is released at this time?
the adrenal gland
cortisol
vasopressin
** this is the stress the body senses when there is an injury, not stress related to fear
(septal nuclei) pleasure: What does stimulation of septal nuclei and surrounding hypothalamus (part of anterior division) result in?
sexual arousal; pleasure/ euphoria from drug activation
(septal nuclei) rage: what do bilateral lesions to the septal region result in?
hyperexcitability (exaggerate jumping when startled), rage (unprovoked attacks)
** these symptoms are identified in the experimental situation
(Amygdala) sensory- affective interactions: What is the amygdala important for?
instinctive reactions to sensory stimuli
The amygdala is important for instinctive reactions to sensory stimuli including the:
motivational and emotional significance of sensations
What do lesions to the amygdala result in?
inappropriate emotional responses to sensory stimuli
(amygdala) emotion: the emotional component to:
learning
The amygdala (emotional part) is important for what?
developing emotional reactions to new experiences, which if repeated become instinctive emotional reactions.
What set of nuclei are implicated in the learned memory of fear?
amygdala
(amygdala) modulator or controller of hypothalamic activities: what does stimulation or lesion of the amygdala produce?
autonomic effects, arousal, sexual activity, motor activity related to eating, aggressive behavior.
What does stimulation of the lateral amygdala produce?
a gradual build up of aggressive behavior (anger), hyperphagia (overeating - lateral hyopthalamus), pleasure reactions, and tameness.
This may sound contradictory, but it is based on the normal social behaviors of an individual
What does stimulation of the medial amygdala produce?
decreases aggressive behavior, aphagia (trouble swallowing/ eating -medial hypothalamus), sadness, and fear associated defensive behavior
There is a connectional relationship of the limbic system with the hypothalamus. This is generally thought to be displayed as the:
autonomic component of aggressive or defensive behaviors.
The medial parts of the amygdala have a preferential connection with medial hypothalamus and are more attuned to behaviors generated out of:
defense of self.
The lateral parts of the amygdala receive powerful sensory association cortical input and are connected more with the lateral divisions of the hypothalamus. This region is more associated with:
predatory or feeding behaviors.
What is the anterior septal region more attuned to?
acting in satisfaction or pleasure
What is the anterior septal region thought to function in?
the euphoria associated with the onset of addictions: cocaine, methamphetamines
