Limbic System and Hypothalamus Flashcards

Flashcards based on the NS102 lecture on the limbic system, hippocampal anatomy, amygdala functions, and hypothalamic nuclei.

Limbic System

A distributed functional network that acts as the interface between the external sensory world and internal homeostatic needs to integrate internal states with external context.

Limbus

A Latin term meaning "border," from which the term limbic system is derived.

Paul Broca

In 1877, he identified the "limbic lobe," a horseshoe-shaped rim of cortex surrounding the junction between the diencephalon and cerebral hemispheres.

James Papez

In 1937, he proposed an emotional system linking the cortex to the hypothalamus, where the cingulate cortex determines the type of emotion and the hypothalamus governs its expression.

Papez Circuit

A group of four structures connected in series: the cingulate cortex, hippocampus, hypothalamus, and thalamus.

Hippocampus

A temporal lobe structure shaped like a seahorse that is critical for encoding and consolidating short-term memory to long-term memory, as well as spatial navigation.

Hippocampal formation

A structure consisting mainly of the hippocampus, the entorhinal cortex, and the parahippocampal gyrus.

Alveus

The axons of the neurons of the hippocampus at the point where they leave the hippocampus.

Fimbria

A white matter tract formed as more axons from the alveus come together.

Fornix

A C-shaped bundle of white matter fibers that serves as the major output tract of the hippocampus, arising from the fusion of the left and right fimbria.

Entorhinal cortex

Located in the parahippocampal gyrus, it provides the majority of the external input to the hippocampus.

Perforant path

The primary external input pathway to the hippocampus, originating in the entorhinal cortex and projecting to the dentate gyrus.

Dorsal/Posterior hippocampus

The division of the hippocampus primarily associated with spatial learning, memory, and context encoding.

Ventral/Anterior hippocampus

The division of the hippocampus involved in emotional behaviors, stress response, and negative feedback for the HPA axis.

Place cells

Specialized neurons in the dorsal hippocampus (CA1 and CA3) that increase their firing rate when an animal is in a specific location, encoding a cognitive map.

Declarative/Explicit memory

Long-term memory used to recall everyday facts (semantic) and events (episodic/biographical).

Procedural/Implicit memory

Long-term memory where previous experiences help perform tasks or habits without conscious awareness.

Retrograde amnesia

The inability to remember events that occurred prior to brain damage.

Anterograde amnesia

The inability to remember events that occur after brain damage.

Patient H.M. (Henry Gustav Molaison)

A famous patient who developed severe anterograde amnesia after the removal of his medial temporal lobes, demonstrating the hippocampus is vital for forming new long-term declarative memories.

Amygdala

A collection of nuclei that responds to emotionally salient stimuli and is associated with fear, anxiety, aggression, and social interactions.

Basolateral nuclei (BLA)

The largest group of amygdala nuclei, responsible for valence coding and communicating bidirectionally with the prefrontal cortex and hippocampus.

Central nuclei (CEA)

Amygdala nuclei connected with the hypothalamus and periaqueductal gray that control the body's physiological emotional response.

Medial nuclei (MEA)

Amygdala nuclei interconnected with the olfactory system, associated with social behavior and aggression.

Valence

The emotional value associated with a stimulus, categorizing it as positive (rewarding/appetitive) or negative (threatening/aversive).

Predatory Imminence Continuum

A theory describing the organization of defensive behaviors (anxiety, fear, panic) based on the distance or potential of a predatory threat.

Prefrontal cortex (PFC)

A brain region involved in complex functions including decision making, impulse control, and emotion regulation by acting as a "brake" on the amygdala.

Uncinate fasciculus

The white matter pathway connecting the prefrontal cortex and the amygdala.

Phineas Gage

A 19th-century patient whose frontal cortex injury provided early evidence that this region is involved in personality and social inhibition.

Hypothalamus

A forebrain structure below the thalamus that is the main visceral control center for homeostasis, regulating the autonomic nervous system and endocrine system.

Infundibular stalk

A tube of blood vessels and nerves that connects the hypothalamus to the pituitary gland.

Pituitary gland

Known as the "master gland," it secretes hormones that control other endocrine glands under the regulation of the hypothalamus.

Ventromedial nucleus (VMH)

A hypothalamic nucleus that regulates satiety and hunger; lesions to this area are associated with obesity and aggression.

Lateral hypothalamic area (LH)

Considered the "feeding center" of the hypothalamus; damage to this area leads to being underweight.

Suprachiasmatic nucleus (SCN)

The brain's biological clock that regulates circadian rhythms and the sleep-wake cycle in response to light cues.

Paraventricular nucleus (PVN)

A hypothalamic nucleus that initiates the HPA stress axis by releasing corticotropin-releasing hormone (CRH).

Mammillary bodies

Paired nuclei in the hypothalamus that serve as a relay for olfactory and hippocampal pathways; damage caused by thiamine deficiency leads to Wernicke-Korsakoff Syndrome.

GnRH (gonadotropin releasing hormone)

A hormone produced in the preoptic nucleus that promotes the release of other gonadotropins by the anterior pituitary.

Arcuate nucleus

A hypothalamic nucleus containing receptors for leptin and insulin; it is a primary target for GLP-1 agonists like Ozempic.

HPA axis

The Hypothalamic-Pituitary-Adrenal axis, a complex system involving the release of CRH, ACTH, and Cortisol in response to stress.

Autonomic Nervous System (ANS)

A motor system that innervates cardiac muscle, smooth muscle, and glands to maintain homeostatic ranges unconsciously.

Sympathetic branch

The part of the ANS responsible for the "fight-or-flight" response and consuming energy.

Parasympathetic branch

The part of the ANS responsible for "rest-and-digest" functions and saving energy.