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Physiology Exam 6 > 78 - Limbic System > Flashcards

78 - Limbic System Flashcards

1
Q

Introduction to emotion

A

Emotion is a combination of powerful subjective feelings and associated physiological states. Subjective feelings are explicit conscious awareness, such as fear, anxiety,
happiness. Physiological states are implicit, unconscious, autonomic, endocrine and somatic motor reactions and responses.

Because of these properties of emotion, the neurobiological system that mediates emotions
needs to be able to interact with both cortex and systems that regulate these physiological states.

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2
Q

Limbic system

A

The limbic system is a convenient way of describing several functionally and anatomically interconnected nuclei and cortical structures that are located in the telencephalon and diencephalon.

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3
Q

Functional properties of the limbic system

A 
• Highly interconnected
• Highly modulated
• Emotional (Affective) responses
      - fear
      - rage
      - pleasure
      - motivation
• Critical for certain types of memory
• Homeostasis
     - reproductive drive
     - eating/drinking behaviors
     - endocrine control
     - autonomic regulation
• Dysfunction results in psychiatric disorders and dementia
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4
Q

Main components of the limbic system

A 
• Limbic cortex (a ring of cerebral cortex that surrounds subcortical limbic structures)
      − Anterior cingulate cortex (Acc)
     − Orbitofrontal, medial prefrontal cortex (mPFC)
     − Insula
• Hippocampus
• Amygdala
• Septal nuclei
• Thalamus
     − Anterior nucleus
     − Mediodorsal nucleus
• Nucleus Accumbens (NAcc)
• Basal forebrain
• Olfactory system
• Hypothalamus
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5
Q

Connectivity and Functional Hierarchy

A

• Reciprocal connections
• Primary output (Hypothalamus)
• Functional Hierarchy
− Hypothalamus: governs and monitors internal homeostasis and basic needs such as hunger and thirst.
− Higher order limbic nuclei (Amygdala, hippocampus, etc): achieve some awareness of external reality and begin to form memories.
− Limbic Cortex: more efficiently, effectively, and safely satisfy limbic needs and impulses; associated with the conscious, rational mind.

Under certain circumstances, emotions can hijack the logical mind, and the limbic system can overturn the neocortex

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6
Q

Modulation via neurotransmitters

A
  • Norepinephrine
  • Serotonin
  • Dopamine
  • Acetylcholine
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7
Q

Where does norepinephrine act?

A

Locus ceruleus (LC)

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8
Q

Where does serotonin act?

A

Raphe nuclei

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9
Q

Where does dopamine act?

A

Mesolimbic system
− Ventral tegmental area (VTA) –> NAcc, mPFC, septal nuc.
− Nigrostriatal projection: Substantia nigra –> striatum

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10
Q

Where does acetylcholine act?

A

− Nucleus basalis –> hippocampus, neocortex

− Septal nucleus –> hippocampus

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11
Q

Describe the overall role of the hypothalamus

A

Governs and monitors internal homeostasis and basic needs such as hunger and thirst. Mediates raw and reflexive emotionality: pleasure, displeasure, rage, and
aversion.

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12
Q

Four zones of hypothalamus

A
  • Lateral zone
  • Periventricular zone
  • Medial zone
  • Posterior zone
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13
Q

Lateral zone nuclei

A
  • lateral preoptic area

- lateral hypothalamic nuclei

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14
Q

Lateral zone behavioral function

A
  • motivation (self-stimulation)
  • emotion (rage)
  • Food & Water intake
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15
Q

Periventricular zone nuclei

A
  • periventricular nuc.& arcuate nuc.
  • suprachiasmatic nuc.
  • premamillary nuc.
  • ventromedial nuc.
  • paraventricular nuc.
  • supraoptic nuc.
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16
Q

Periventricular zone behavioral function

A
  • pituitary regulation (Ant.&Post)
  • CRH, TRH, GH-RH, LH-RH, DA
  • diurnal rhythm
  • GH-RH, glucose metabolism
  • oxytocin, vasopressin
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17
Q

Medial zone nuclei

A
  • medial preoptic nuc.
  • dorsomedial nuc.
  • anterior nuc.
  • ventromedial nuc.
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18
Q

Mecial zone behavioral function

A
  • temperature regulation
  • sexual differentiation & behavior
  • food intake
  • nutrient balance
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19
Q

Posterior zone nuclei

A
  • posterior nuc.
  • supramammillary nuc.
  • mammillary bodies
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20
Q

Posterior zone behavioral function

A
  • cardiovascular regulation
  • respiratory regulation
  • temperature regulation
21
Q

What are the characteristics of the hypothalamus?

A 
• Primary output of limbic system
• Primitive, similar through evolution
• Fully functional at birth
• Highly involved in all aspects of
     − emotional responses
     − reproductive drive
     − endocrine
     − hormonal regulation
     − autonomic function
     − eating, drinking, sleeping
• Exerts influence through synaptic connections and circulation
• Sexual dimorphism
22
Q

Describe the relationship between the hypothalamus and the autonomic nervous system (ANS)

A

• Hypothalamus controls emotion expression through ANS.
• Intense activity of the sympathetic division prepares animal to fully utilize metabolic and other resources in challenging or threatening situations.
• Conversely, activity of the parasympathetic and enteric divisions promotes
a build up of metabolic reserves.

23
Q

Describe the basic function of the amygdala

A

Amygdala is the integrative center for emotions, emotional behavior, and
motivation

24
Q

Components of the amygdala

A

~ 10 distinct nuclei; can group into 3 functional sets

  1. Corticomedial nucleus
  2. Basolateral nucleus
  3. Central nucleus
25
Q

Connections of the amygdala

A

Connections define its function. The amygdala receives sensory information
directly from the various sensory systems that process the external world. The
output of amygdala are the systems involved in the emotional reactivity.

26
Q

Major inputs of the amygdala

A

Sensory cortex
Sensory thalamus
Associative cortex
Prefrontal cortex

27
Q

Major outputs of the amygdala

A

Hypothalamus
Thalamus
Basal ganglia

28
Q

Functional properties of the amygdala

A

Functional Properties
• Fear, anxiety; aggression
• Interpretation of facial expression, particularly fear
• Mediating conditioned fear response (learning)
• Stimulation of the amygdala produces a perception of familiarity
• Motivation & reinforcement to fear behaviors (via nucleus accumbens)
• Homeostasis (neuroendocrine control)

29
Q

Describe the amygdala role in fear, anxiety and aggression

A

Fear, anxiety; aggression
− Profound lesion to the amygdala → flat affect, docile behavior
− Other brain regions involved in regulation of emotion processing

30
Q

Describe the amydala role in mediating conditioned fear responses (learned fear)

A

Mediating conditioned fear response (learning)
− Best understood through animal studies of Pavlovian fear conditioning
− When a conditional stimulus (neutral, CS) is repeatedly paired with a unconditional stimulus (aversive, US. For example, foot shock), over time the animal begin to respond to the neutral stimulus with fear behaviors.
− Underlying neural circuit: Synaptic connections of sensory inputs to amygdala neurons are strengthened; Amygdala outputs to hypothalamus activate the visceral motor effector system to prepare body for an action.

31
Q

What three processes is the hippocampus involved in?

A
  • Sensory processing
  • Homeostasis
  • Learning and memory
32
Q

Sensory processing by the hippocampus

A

Sensory processing
– Novelty detection
– Spatial organization

33
Q

Homeostasis by the hippocampus

A

Homeostasis
– Regulation of HPA axis
• ↑ [glucocorticoid receptors] in CNS
• toxic effects of stress (cortisol)

34
Q

Learning and memory in the hippocampus

A 
Learning & Memory
– Long-term synaptic plasticity
     • explicit memory
– Spatial context and surroundings
     • place cells
– Contextual regulation to amygdala-mediated fear processing
35
Q

What processes target the hippocampus?

A

Aging and stress

36
Q

Function of the frontal cerebral cortex

A

The role of the cerebral cortex in emotional behaviors is complex where many exceptions and contradictions appear to exist, illustrating our poor understanding.

37
Q

How does the frontal lobe play a role in restraint?

A
  • Judgement
  • Foresight
  • Perseverance
  • Delayed gratification
  • Inhibition of socially unacceptable behavior
  • Self-governance
  • Concentration
38
Q

How does the frontal lobe play a role in initiative?

A
  • Curiosity
  • Spontaneity
  • Motivation
  • Drive
  • Creativity
  • Personality
  • Mental flexibility
39
Q

How does the frontal lobe play a role in order?

A
  • Abstract thinking
  • Working memory
  • Perspective
  • Planning
  • Insight
  • Organization
  • Sequencing
40
Q

How does the frontal lobe play a role in cortical regulation of the fear response?

A

Medial prefrontal cortex projecting to amygdala

41
Q

What is empathy?

A

Understanding emotion in others

42
Q

Limbic system “mirror neurons”

A

The concept of the mirror neuron originates from a phenomenon that a subset of neurons in the premotor region are activated when a monkey performs an action itself and when it observes another living creature perform that same action. Thus we understand the actions (emotion) of others possibly by activating our own neural representation of these actions (emotion).

43
Q

Empathy for pain

A

The neural substrate for empathic experience does not involve the entire “pain matrix.” Only that part of the pain network associated with its affective qualities, but not its sensory qualities, mediates empathy.

44
Q

Manifestations of prefrontal cortex lesion

A
  • Apathetic
  • Impulsive
  • Poor judgment
  • Depressive behaviors
  • Mania
45
Q

What are the four components of the brain reward system?

A 
• Nucleus accumbens
• Frontal cortex
• Ventral tegmental
area (VTA)
• Dopamine
46
Q

Describe the process of the brain reward system

A
  1. Underlying circuits: the reinforcement limbic loop
  2. Elements of this loop are modulated by the dopaminergic system.
  3. Dopamine from ventral tegmental area (VTA) to nucleus accumbens serves as the reward signal
  4. Under normal physiological conditions, emotional processing in the limbic system can signal the presence of rewards and can promote the activation of
    motor programs to acquire the beneficial rewards. Natural rewards include food, water, sex, love, nurturing etc.
47
Q

Drug addiction in relation to emotional reinforcement

A

Addiction highlights the vulnerability of emotional neural circuits to dysregulation when they are exposed to drugs.

48
Q

Effect of drug addiction on the limbic system

A
  • Drugs of abuse, including cocaine, heroin, alcohol, opiates, marijuana, nicotine, and their synthetic analogs act on elements of the limbic circuitry by altering the neuromodulatory influence of dopamine.
  • Addiction dampens the response of reward circuitry to natural rewards, and intensifies the response to addictive drugs, resulting in “hypofrontality” – reduced cortical control of emotional behaviors.

Physiology Exam 6 (16 decks)

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