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39 Cards in this Set

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What is the LIMBIC SYSTEM?
It is functionally connected areas of the telencephalon and diencephaloninvolved in control of emotions and regulating appetites and behaviors
What is the LIMBIC CORTEX?
These are the cortical regions associated with these functions
What is Kluver-Bucy syndrome?
Behavioral changes due to bilateral lesions of the temporal lobe inlcuding neocortex, olfactory cortex, amygdala and hippocampus. Animal
explores all objects, often orally (even normally fear-producing ones). Loss of emotions of fear or anger, docile. Hypersexual.
What does LONG- TERM POTENTIATION refer to?
Deals with prolonged changes in the responsiveness of a neuron due to activation of NMDA glutamate receptors.
What is the function of the LIMBIC SYSTEM?

What do most functions have to do with?
It describes functionally and anatomically interconnected nuclei and cortical structures located in the TELENCEPHALON and DIENCEPHALON.

Most functions have to do with control of functions necessary for SELF PRESERVATION and SPECIES PRESERVATION- - regulating autonomic and endocrine functions

This system is involved in AROUSAL, MOTIVATION, REINFORCING BEHAVIORS, MEMORY, and OLFACTION
What are the 2 categories that areas in the limbic
CORTICAL

SUBCORTICAL
What are the regions involved in the CORTICAL REGION?

Why has it been called the LIMBIC LOBE?
1) HIPPOCAMPUS (including areas of the NEOCORTEX including the INSULAR CORTEX
2) ORBITAL FRONTAL CORTEX
3) SUBCALLOSAL GYRUS
4) CINGULATE GYRUS
5) PARAHIPPOCAMPAL GYRUS

The cortical region has been called the LIMBIC LOBE because it makes a rim surrounding the corpus callosum, following the lateral ventricle
What are the regions involved in the SUBCORTICAL REGION?
1) OL FACTORY BULB
2) HYPOTHALAMUS
3) AMYGDALA
4) SEPTAL NUCLEI
5) THALAMIC NUCLEI
6) ANTERIOR AND DORSOMEDIAL NUCLEUS
What's another way to think of the brain?
It has been conceptualized as the "feeling and reacting brain" that is interposed between the "thinking brain" and the output mechanisms of the nervous system.

So the LIMBI SYSTEM is usually under the control of the "thinking brain' but can react on its own
A) What structures are in the INPUT PROCESSING SYSTEM to the limbic system?

B) OUTPUT?
A)
1) LIMBIC CORTEX (ORBITOMEDIAL FRONTAL ORTEX)
2) AMYGDALA
3) HIPPOCAMPUS

B)
1) SEPTAL NUCLEI
2) HYPOTHALAMUS
* HYPOTHALAMUS *

A) What is the HYPOTHALAMUS and what is it the PRIMARY OUTPUT for?

B) What is it connected to?

C) What other functions is it involved in?
The hypothalamus, the primary output node for the limbic system, has many important connections.
A) It is connected with the frontal lobes, septal nuclei and the brain stem reticular formation via the medial forebrain bundle.

B) It also receives inputs from the hippocampus via the fornix and the amygdala via two pathways (ventral amygdalofugal pathway and stria terminalis)

C) The hypothalamus has centers involved in sexual function, endocrine function, behavioral function and autonomic control.
What are the specific INPUTS to the HYPOTHALAMUS?
1) It has inputs from most of the body including
- olfaction
- viscera
- retina

2) It has internal sensors for
- temperature
- osmolarity
- glucose
- sodium concentrations

3) It has receptors for
- internal signals
- hormones/ steroids
- hormones involved in appetite control
How are AUTONOMIC FUNCTIONS controlled?

Where are these areas localized?
Autonomic functions are
controlled via projections to the brain stem and spinal cord. There are localized
areas in the hypothalamus that will activate the sympathetic nervous system and some that will increase parasympathetic activity.
What are ENDOCRINE FUNCTIONS controlled by?
Endocrine functions are
controlled either by direct axonal connections to the posterior pituitary gland
(vasopressin and oxytocin control) or via release of releasing factors into the
hypothalamic-hypophyseal portal system (to influence anterior pituitary
function).
What is the hypothalamus also involved with?
There are also projections to the reticular formation that are involved in certain behaviors, particularly emotional reactions.
What are different nuclei of the hypothalamus and what functions are they associated with?
1) PREOPTIC AREA: one of the areas of greatest sexual dimorphism (i.e., difference in structure between the sexes) as well as..

2) the SEPTAL NUCLEI: which is an area of gonadotropin releasing hormone projections to the median eminence region of the hypothalamus.

3) the SUPRACHIASMATIC NUCLEI: receives direct retinal input. This nucleus is responsible for entraining circadian rhythms to the day-night cycle.
A) What is the AMYGDALA?

B) What structures make reciprocal connections with the brain?

C) What is the only area that makes INPUT into the AMYGDALA?
A) The amygdala is an important
structure located in the anterior temporal lobe within the uncus.

B) The amygdala makes reciprocal connections with many brain regions (see the figure) including the

- thalamus
- hypothalamus
- septal nucleI
- orbital frontal cortex
- cingulate gyrus
- hippocampus
- parahippocampal gyrus
- brain stem

C) The olfactory bulb is the only area that makes input to the amygdala and does not receive reciprocal projections from the amygdala.
What is the AMYGDALA critical for?
The AMYGDALA is critical for coordinating behavioral, autonomic, and endocrine responses to environmental stimuli, especially those with emotional content.

It is important to the coordinated responses to stress and integrates many behavioral reactions involved in the survival of the individual or of the species, particularly to stress and anxiety
What do lesions in the AMYGDALA cause?
Lesions of the amygdala reduce responses to stress, particularly conditioned emotional responses.
What does stimulation of the AMYGDALA cause?
Stimulation of the amygdala produces behavioral arousal and can produce directed rage reactions.
Why is the convergence of inputs to the AMYGDALA important?

What types of stimuli does the AMYGDALA mostly respond to?
The convergence of inputs is important since it allows the generation of learned
emotional responses to a variety of situations.

The amygdala responds to a variety of emotional stimuli, but mostly those related to fear and anxiety.
* HIPPOCAMPUS *
*
What is the hippocampus?

Where is it located?
The hippocampus is an ancient
area of cerebral cortex that has
three layers.

This is located in the medial aspect of the temporal lobe, forming the medial wall of the lateral ventricle in this area.
What are teh different parts of the HIPPOCAMPUS?
A) DENTATE NUCLEUS:
The dentate gyrus contains densely packed granule cells.

B) CORNU AMMONIS (CA):
There is a curved area of cortex
called the Cornu Ammonis (CA)
that is divided into four regions
called the CA fields. These are designated as CA1 to CA4. These contain
prominent pyramidal cells. The CA fields blend into the adjacent subiculum,
which, in turn, is connected to the ENTORHINAL CORTEX on the PARAHIPPOCAMPAL
GYRUS of the temporal lobe.
What are several sources of HIPPOCAMPAL AFFERENTS and where do they primarily come from?

Where do the CORTICAL REGIONS receive input from?

Where does the ENTORHINAL CORTEX project to?

Where do the granule cells connect to?
The HIPPOCAMPAL AFFERENTS are primarily from the septum and hypothalamus via the fornix and from the adjacent ENTORHINAL CORTEX

This cortical region receives input from diffuse areas of the neocortex, especially the limbic cortex, and from the amygdala.

The entorhinal cortex projects to the dentate gyrus of the hippocampus via the perforant pathway, synapsing on granule cells.

These granule cells connect to pyramidal neurons in the CA3 region, which, in turn,project by Sheaffer collaterals to CA1
pyramidal cells. It is these latter cells that give rise primarily to the fornix.
What are the two outputs for the HIPPOCAMPUS?
The first of these outputs is through the fornix. These fibers project to the mamillary bodies via the post-commissural fornix, to the septal nuclei, to the preoptic nucleus of the hypothalamus, to the ventral striatum and to portions of the frontal lobe through the precommisural fornix. There are large numbers of projections from the hippocampus back to the entorhinal cortex.
LOOK AT THE PICTURE AND DRAW OUT THE PATHWAY...
*
What are the functions of the hippocampus?
1) It helps control corticosteroid production. It also has significant contribution to understanding spatial relations within the environment.

2) Additionally the hippocampus is critically involved in many declarative memory functions.
What are the different types of memory?
1) EXPLICIT or DECLARATIVE: refers to the memory of facts and events. Any memory that can be explained in words is this type of memory.

2) NON- DECLARATIVE MEMORY: is also very important. The learning of skills as well as associative learning, such as
conditioned and emotional responses are common examples of non-declarative or implicit memory.
What more about EXPLICIT MEMORY?
1) Explicit memory depends on the medial temporal lobe and
the relationship between the hippocampus and entorhinal region of the parahippocampal gyrus.

2)There are several areas involved in explicit memory. The hippocampus plays a critical role in short-term memory, which is absolutely necessary if long-term
memory patterns are to be established.
1) What happens if you have a lesion in the HIPPOCAMPUS?

2) What happens to your memory?
1) Lesions of the hippocampus do not affect old, established memories. These lesions affect new declarative learning.

2) Ultimately, memory storage is transferred to other areas of the cerebral cortex,
and the location of encoding of these memories may be a function of the type of
memory. Established memories involve association areas in the frontal lobe and
parieto-temporo-occipital association cortex.
* LIMBIC CORTEX *
*
Where is the LIMBIC CORTEX?
The prefrontal cortex is anterior to the premotor cortex. The orbital frontal cortex
is the portion over the orbits.
What is the function of the PREFRONTAL CORTEX?

What does the prefrontal cortex receive input from?
This part of the cortex is extremely well-developed
in humans and is critical to
- judgment
- insight
- motivation
- mood

It is also important for conditioned emotional reactions.

The prefrontal cortex receives input from the other areas of limbic cortex, from the amygdala and from septal nuclei and has reciprocal connections with each of these areas and with the dorsomedial nucleus of the thalamus.
What does damage to the prefrontal area cause?

What does the effect of frontal lobe damage depend on?
Damage to the prefrontal area produces difficulties with abstract reasoning,
judgment moods and puzzle solving.

The effect of frontal lobe damage on mood depends on the specific part of the prefrontal cortex damaged. The patient's behavior is often described as tactless.

* NOTE: Also, this part of the cortex can also be strongly affected by alcohol.
What does an abnormal prefrontal cortex function produce?

Depresseion is most often associated with what? (increased activity in what parts of the lobe?)
Prefrontal cortex function is abnormal in mood disorders. Depression is
most often associated with increased activity in portions of the frontal lobe,
especially the medial regions including the subgenual portion of the anterior
cingulate cortex, and decreased activity in the posterior cingulate gyrus.
What is the role of OLFACTION in the LIMBIC CORTEX?

What parts of the brain is it most connected with?
Olfaction makes strong connections with the anterior portions of the
temporal lobe and the amygdala.

The olfactory cortex is structurally simpler than
other portions of the cerebral cortex and is termed allocortex.
What structures does the OLFACTORY CORTEX include?
It includes the
prepiriform and periamygdaloid cortex that comprises the anterior part of the
parahippocampal gyrus covering the uncus. In some species, of course, olfaction is more important than in others.
Describe the pathway of OLFACTORY FILAMENTS?
Olfactory filaments cross the cribiform plate and synapse with mitral cells in the olfactory bulbs. Axons from these cells make up the olfactory tract which extends to anterior temporal structures bilaterally as
well as the basal forebrain.