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Neurobiology > Limbic System > Flashcards

Limbic System Flashcards

1
Q

what is the limbic system?

A

A collection of cortical and subcortical structures located in the medial and ventral regions of the cerebral hemispheres

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2
Q

What is defined as the limbic cortex/lobe?

A

The cingulate gyrus and parahippocampal gyrus

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3
Q

What are the four main functions of the limbic system?

A

Homeostasis, olfactory, memory, emotion (HOME)

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4
Q

List the many components of the limbic system

A
  • Limbic cortex
  • Hippocampal formation
  • Amygdala
  • Olfactory cortex
  • Diencephalon
  • Septal nuclei
  • Brain stem
  • Basal ganglia
  • Basal forebrain
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5
Q

What are the functions of the limbic cortex?

A

Cingulate gyrus: memory, emotional processing, afferent nervous system
Parahippocampal gyrus: Memory processing

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6
Q

What are the three parts of the hippocampal formation and do they receive input or send output?

A

Located on the medial temporal lobe
1. Dentate gyrus: afferent input
2. Subiculum: efferent output
3. Hippocampus: efferent output

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7
Q

What is the amygdala responsible for and what nuclei are involved?

A

Functions: emotion, behavior, emotional response to smell
Nuclei: corticomedial nucleus (olfaction), central nuclei (autonomic control), basilar nuclei group (all other emotions)

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8
Q

What are the nuclei involved in the limbic system within the hypothalamus?

A

Mamillary bodies: main nuclei involved in limbic pathways
ANS nuclei: give rise to parasympathetic and sympathetic pathways

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9
Q

What are the nuclei involved in the limbic system within the thalamus?

A

Anterior nucleus of the thalamus: involved in the Papez Circuit and memory
Mediodorsal nucleus of the thalamus: emotions and behaviors

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10
Q

How is the septal area involved in the limbic system?

A
  • It is connected to the Habenula which is part of of the epithalamus
  • Part of the reward pathways and involved in dopamine and serotonin
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11
Q

What is the association cortex?

A
  • Part of the cerebral cortex that is not directly involved with sensation or movements
  • Found in prefrontal cortex and temporal cortex
  • Helps associate motor and sensation to emotions
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12
Q

Match the limbic system function acronym HOME with the key structure responsible for the function

A

Homeostasis: hypothalamus
Olfaction: olfactory cortex
Memory: hippocampal formation
Emotion: amygdala

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13
Q

What vasculature supplies blood to the limbic system?

A

Anterior cerebral artery: medial surface of frontal and parietal lobe
Posterior cerebral artery: medial and inferior surface of the temporal lobe
Anterior choroidal artery: cingulate gyrus, parahippocampal formation, and amygdala
Branches of circle of willis: hypothalamus, anterior commissure

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14
Q

List the tracts involved in the limbic system

A
  • Medial and lateral olfactory stria
  • Fornix
  • Stria terminalis
  • Ventral amygdala fugal pathway
  • Mammillothalamic tract
  • Medial forebrain bundle
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15
Q

Describe the medial and lateral olfactory stria

A
  • Involved in olfaction
  • Receives input from olfactory tracts
  • Sends output to the primary olfactory cortex, orbital frontal olfactory cortex, corticomedial nucleus of the amygdala (smell evoked emotion), parahippocampal gyrus (smell evokes memory)
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16
Q

Describe the fornix

A
  • Involved in memory pathways
  • Signals sent between septal areas in deep center of brain, hippocampal formation, and mamillary bodies of the hypothalamus
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17
Q

Describe the mammillothalamic tract

A
  • Involved in memory pathways
  • Sends input to the anterior nucleus of the hypothalamus
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18
Q

Describe the stria terminalis

A
  • Involved in the amygdala pathway (long way to reach septal area because it travels along the wall of the lateral ventricle)
  • Signals between the septal area, amygdala (fornix), and hypothalamus
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19
Q

Describe the ventral amygdalofugal pathway

A
  • Involved in the amygdala pathway (short way to reach septal area)
  • Signals between septal area, amygdala, hypothalamus, and mediodorsal nucleus of the thalamus
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20
Q

Describe the medial forebrain

A
  • Involved in sending information about behaviors, emotions, and personality to the brainstem and back (two way connection)
  • Signals sent from amygdala to hypothalamus, to brainstem and back
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21
Q

What is olfaction?

A
  • Function: smell contributes to the sensation of odors and taste
  • Single odor molecule activates olfactory receptors, this results in a infinite number of different odors
  • The only sensation that bypasses the thalamus
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22
Q

How is smell detected?

A

Smell stimulus > activation of olfactory receptors > olfactory nerves > through cribiform plate of ethmoid bone > olfactory bulb > olfactory tract > medial and lateral olfactory stria

23
Q

Which part of the brain is responsible for declarative memory specifically?

A
  • Hippocampal formation
  • Medial temporal lobes (parahippocampal gyrus, entorhinal cortex)
24
Q

How can memory influence decision making?

A

There is an important connection between the hippocampal formation and the prefrontal association cortex that allows you to consult your memory during decision-making to ensure you are making the correct decision

25
Q

Describe the pathway of the Papez circuit

A
  • Responsible for memory processing and learning
  • Signals from the subiculum of the hippocampus sent to the mammillary bodies of the hypothalamus via the fornix
  • Mamillary bodies send signals to the anterior nucleus of the thalamus via the mammillothalamic tract
  • Anterior nucleus of the thalamus sends signals to the cingulate gyrus and pre-frontal association cortex
  • The cingulate gyrus sends signals to the parahippocampal gyrus
  • The parahippocampal gyrus sends signals to the dentate gyrus of the hippocampus, signals then make their way back to the subiculum
26
Q

What are the three types of memory processes?

A
  • Encoding: acquiring information
  • Storage: maintaining information (medial temporal lobe)
  • Retrieval: recalling information (communication with prefrontal cortex and other association cortices)
27
Q

What is retrograde amnesia?

A

Type of declarative memory failure in which there is a loss of memories that occurred before the trauma or disease

28
Q

What is anterograde amnesia?

A

Type of declarative memory failure in which there is a loss of memory that occur after the trauma or disease

29
Q

How may someone with amnesia learn new things?

A

Through implicit memory they may have a change in performance without conscious awareness, there may be an improvement in perceptual skills (face and pattern recognition) and cognitive skills (reasoning and logic)

30
Q

What is Wernicke Encephalopathy/Wernicke Korsakoff Syndrome?

A
  • Disorder of hippocampal function
  • Destruction of mammillary bodies of the hypothalamus due to thiamine (B1) deficiency
  • Symptoms: profound memory loss, confabulation, impulsive, eye movement abnormalities, ataxia
31
Q

What is Alzheimer’s disease?

A
  • Disorder of hippocampal function
  • Bilateral hippocampal, temporal, and basal forebrain structures have disruptions of cholinergic neurons resulting is progressive dementia/memory loss
32
Q

What is psychogenic amnesia?

A
  • Disorder of hippocampal formation
  • Memory loss for events of particular emotional significance
33
Q

What is a seizure?

A

High frequency electrical discharge and firing of neurons in the brain resulting in abnormal experience of behavior

34
Q

What are the phases of a generalized seizure?

A

Tonic: all muscles stiffen and person falls over
Clonic: rhythmic bilateral jerking
Ictal (during the seizure): autonomic response of tachycardia, HTN, hypersalivation, and pupillary dilation
Post-ictal (after the seizure): fatigue, amnesia, headache, deep breathing to compensate for acidosis

35
Q

What are the two types of partial seizure?

A

Simple: person is aware during the seizure and symptoms depend on the area of the brain that is affected (ex. right motor cortex hand area = hand twitching, visual association cortex = hallucinations)
Complex: impaired consciousness and increased symptoms

36
Q

Describe the common symptoms for a seizure that occurs in the medial temporal lobe

A
  • Aura is common
  • Memory loss (anterograde amnesia) if repeated, resulting in hippocampal sclerosis
  • Contralateral dystonia (basal ganglia typically involved)
  • Ipsilateral automatisms: repetitive behaviors such as limb patting or stroking, or lip smacking
37
Q

What is the cause of a medial temporal lobe seizure? What is the treatment?

A

Cause: genetics, fever, head trauma, CVA, infection, electrolyte abnormality
Treatment: medications, surgery, ketogenic diet, neurostimulation, hemispherectomy if pt is under 2-3 years old

38
Q

What is the function of the amygdala?

A
  • Emotional responses: occurs in a situation where you feel fear, anger, rage, sadness and the amygdala must communicate with other structures
  • Involved in motivation, behavior, personality, etc.
39
Q

Why are there connections between the amygdala and the association cortex and temporal lobe?

A
  • Decision making influenced by memory and emotions
  • The ability to regulate emotion
40
Q

Describe the signal between the amygdala and hypothalamus regarding appetite

A
  • Sadness pertaining to appetite depending on where in the hypothalamus the synapse occurs
  • Ventromedial nucleus of the hypothalamus: satiety, too sad to eat
  • Lateral hypothalamic nucleus: hunger, i need to eat my sorrows away
41
Q

Describe the signal between the amygdala and hypothalamus regarding sexual behavior

A
  • Good feelings
  • Periventricular nucleus of hypothalamus: releases oxytocin which increases sexual drive and blood flow to organ
  • Medial preoptic nucleus of the hypothalamus: releases gonadotropin releasing hormone to increase sex drive
42
Q

What are the two areas involved in the amygdala’s reward seeking pathway and what are the clinical implications?

A
  • Medial prefrontal cortex
  • Ventral striatum
  • Implications: sense of euphoria with drug use leading to abuse and addiction
43
Q

Describe the mesolimbic pathway as it pertains to reward-seeking

A

Ventral tegmental area > dopaminergic neurons > nucleus accumbens (ventral striatum on basal ganglia)

44
Q

Describe the cortico-basal ganglia-thalamus circuit as it pertains to reward-seeking

A

Ventral tegmental area > dopaminergic neurons > medial dorsal thalamic nuclei > medial prefrontal cortex

45
Q

What is addiction?

A
  • Loss of behavioral control in response to a stimulus combined with continued use of a substance regardless of negative consequences
  • Those effected have lower levels of dopamine
46
Q

What specific functions is the hypothalamus responsible for in the limbic system?

A
  • Emotional influences on autonomic pathways
  • Homeostasis including immune function
  • Homeostasis as it pertains to motivation and reproduction
47
Q

What are some examples of homeostatic changes can be seen based on emotions?

A
  • Really scared: shaking, pilo erection
  • Embarrassed: cheeks get red (vasodilation)
  • Nervous: blotchy, sweaty
48
Q

Describe how the homeostasis pathway can create an autonomic response

A
  • Central nuclei of the amygdala senses an emotion of fear and anxiety and sends it to the hypothalamus via the stria terminalis or the ventral amygdalofugal pathway
  • Descending autonomic fibers send signals from the hypothalamus to the brainstem via the medial forebrain bundle
  • Fibers synapse on the parasympathetic nuclei in the brainstem and sacral region, and on sympathetic nuclei in the thoracolumbar region
  • Increase HR, glucose secretion, vasoconstriction to LEs for running, increase respiratory rate
49
Q

What makes up the diencephalon?

A
  • Thalamus
  • Hypothalamus
  • Epithalamus
  • Subthalamus
50
Q

Why is the hypothalamus essential to survival?

A
  • Homeostasis: circadian rhythm, appetite, thirst, drive
  • Endocrine control: release hormones and stimulatory/inhibitory factors to pituitary gland
  • Autonomic: descending projections influence sympathetic and parasympathetic divisions of the ANS via medial forebrain bundle
  • Limbic system: involved in the stria terminalis, ventral amygdalofugal pathway, fornix, and mammillothalamic tract (limbic = emotions and memory)
51
Q

What hormones are released from the anterior pituitary gland and what are their functions?

A
  • Adrenocorticotropic hormone: stimulates adrenal cortex to produce corticosteroid hormones, important for BP and electrolyte regulation
  • Growth hormone: stimulates organs to secrete hormones to promote growth in long bones and other tissues
  • Prolactin: mammillary glands to produce milk
  • Luteinizing hormone and follicle stimulating hormone: regulates ovarian hormone for menstruation and ovulation in females, regulates testicular hormones and spermatogenesis in males
52
Q

What hormones are released from the posterior pituitary gland and what are their functions?

A
  • Antidiuretic hormone: increases reabsorption of water in the kidney, allows for concentration of urine
  • Oxytocin: stimulates smooth muscle in the uterus for labor and delivery, elicits milk expulsion in lactating females
53
Q

What symptoms can arise with pituitary tumors?

A
  • Headaches
  • Nausea/vomiting
  • Irregular menstruation and lactation
  • Sexual dysfunction
  • High BP
  • Increased glucose
  • Acromegaly: growth hormone disorder causing enlargement of the head, hands, and feet
  • Cushing’s disease: excessive adrenocorticotropic hormone causing abnormal deposits of face and trunk fat
  • Bitemporal hemianopia: compression of optic chiasm

Neurobiology (15 decks)

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