Lecture 11 Limbic System Flashcards
What are the 4 major functions of the limbic system?
Homeostasis
Olfaction
Memory
Emotions and Drive
What is the primary limbic structure involved with homeostasis?
hypothalamus
What are the major anatomical landmarks of the hypothalamus and where can they be found?
- tuber cinereum - bulge of gray matter on ventral surface of hypothalamus behind the optic chiasm
- mamillary bodies - under optic chiasm
- infundibulum - stock that gives rise to pituitary stock
What are the 2 major functions of the hypothalamus?
2 H’s - Homeostasis and Hormons
- regulation of homeostatic mechanisms
- regulates release of hormones via pituitary gland
What are the major afferent inputs to the hypothalamus for homeostasis?
- solitary nucleus
- reticular formation and spinal cord
- retinal pathways
- limbic system
- circumventricular organs
What information does the solitary nucleus bring to the hypothalamus?
visceral info from Vagus nerve on BP and gut distention
What information does the reticular formation and spinal cord bring to the hypothalamus?
general info re: skin temperature (thermoregulation)
What information does the retinal pathways bring to the hypothalamus?
input on day/night input - circadian rhythm
What information does the limbic system bring to the hypothalamus?
eating, reproduction
What information does the circumventricular organs bring to the hypothalamus?
changes in osmolarity and toxins
What are circadian rhythms?
- physical, mental, and behavioral changes that follows a 24-hour cycle of our day
How does our hypothalamus get involved with circadian rhythms during the day?
During the day, posterior hypothalamic nuclei contain glutamatergic, histaminergic and orexin neurons that contribute to arousal
How does our hypothalamus get involved with circadian rhythms at night?
Retinal ganglion cells convey photosensitivity info re: day/night directly to suprachiasmatic nucleus of hypothalamus
- SCN projects to other hypothalamic nuclei and pineal gland to modulate body temp and produce sleep hormones
- inhibitory projects from neurons in ventral lateral preoptic area of anterior hypothalamus inhibit ascending activity of reticular formation
Where is the “shut off” switch for wakefulness?
suprachiasmatic nucleus (SCN)
What are the major outputs of the hypothalamus to help regulate homeostatic control?
- autonomic system (para and sympathetic systems to control HR, vasoconstriction, digesting, sweating, etc)
- endocrine gland - pituitary gland
- limbic system - when we need to attach memory or emotion to these changes in homeostasis
What is the major memory center?
hippocampal formation
What is the major emotional center?
amygdala
Why is the pituitary gland referred to as the master gland?
it controls itself and controls others through its own secretion of hormones
What does the anterior pituitary contain?
glandular cells that synthesize and release hormones into circulation
What does the posterior pituitary contain?
axons and terminals of neurons whose cell bodies are located in the hypothalamus
- then hypothalamus releases hormones into circulation
What are the 6 hormones secreted by the anterior pituitary gland?
- Adrenocorticotropic hormone (ACTH)
- Growth Hormone
- Prolactin
- Thyroid-Stimulating Hormone (TSH)
- Luteinizing Hormone (LH)
- Follicle-Stimulating Hormone (FSH)
What does ACTCH do?
stimulates adrenal cortex to create corticosteroid hormones that maintain BP, control electrolyte balance, promote glucose mobilization into bloodstream
What does GH do?
causes liver, kidneys, and other organs to produce somatomedins or insulin-like growth factors to promote increased growth of long bones and other tissues
What does Prolactin do?
stimulates mammillary glands on breasts to produce milk
What does TSH do?
stimulates thyroid gland to produce T3 and T4 to promote cellular metabolism
What does LH do?
regulate ovarian hormones responsible for menstruation and oogenesis in females
What does FSH do?
Regulate testicular hormones and spermatogenesis in males
What are the 2 hormones released by the posterior pituitary?
Oxytocin and Vasopressin
How does the hypothalamus modulate pituitary function?
hypothalamus controls the release of the hormones that the pituitary gland synthesizes
Where can the primary olfactory cortex be found?
medial and rostral tip of temporal lobe
What secondary areas of the brain does the primary olfactory cortex project to?
- entorhinal cortex
- orbitofrontal olfactory area
- amygdala
What is the entorhinal cortex’s role in olfaction?
smell and memory
What is the orbitofrontal olfactory area’s role in olfaction?
smell discrination
What is the amygdala’s role in olfaction?
smell + emotion and motivation
What are the two major regions in which we find limbic structures that are involved with memory?
- medial temporal lobe memory areas
- medial diencephalic memory areas
What structures are in the medial temporal lobe memory areas?
- hippocampal formation (primary memory structure)
- parahippocampal gyrus
- perirhinal cortex
What structures are in the medial diencephalic memory areas?
- mediodorsal and anterior nuclei of thalamus
- mammillary bodies of hypothalamus
What is the primary limbic structure associated with memory?
hippocampal formation
What is the major role of the medial diencephalic memory areas?
crucial relay stations of efferent memory signals coming from our medial temporal lobes and then going up to other areas of the cortex and some cortical regions
What are the major anatomical structures that make up the hippocampal formation?
- dentate gyrus
- hippocampus
- subiculum
What is the hippocampal formation most involved with when it comes to memory?
long-term memory
Where is the Parahippocampal gyrus in relation to the hippocampal formation?
medial and slightly inferior
What are the major anatomical structures that make up the Parahippocampal gyrus?
- entorhinal cortex
- parahippocampal cortex
What is the Parahippocampal gyrus most involved with when it comes to memory?
object identity and object configuration memory
Where is the perirhinal cortex in relationship to the Parahippocampal gyrus?
lateral and slightly inferior
What is the perirhinal cortex most involved with when it comes to memory?
recognition and ID of environmental stimuli
- visual or depth perception of our surrounding environment
Where does the hippocampal formation receive input from?
- most from heteromodal association cortex via entorhinal cortex
- contralateral hippocampus via hippocampal commissure
- basal forebrain and Septal nuclei send cholinergic (AcH) projections
Where does the hippocampal formation project to?
- heteromodal association cortex via entorhinal cortex
- subcortical structures (thalamus, hypothalamus, etc.) through fornix
What is the fornix? Where can it be found?
- connects hippocampal formation with variety of subcortical regions
- found in medial aspect of cerebral hemispheres surrounding the thalamus
What are the main targets of the fornix?
- mamillary bodies of hypothalamus
- Septal nuclei
- anterior nucleus of thalamus
The limbic system is not the only system involved in memory storage and consolidation. Where do limbic structures’ function fall in the continuum of memory?
minutes to years
What is the function of the temporal poles?
left - semantic memory (meanings, names, general impersonal facts)
right - personal and episodic memories (closely associated with emotion and socially relevant memories)
What is the major limbic structure associated with emotions and drive?
amygdala
What are the major connections seen with the amygdala?
- olfactory system and hypothalamus
- hypothalamus and brainstem
- mediodorsal nucleus of thalamus
- limbic cortex and hypothalamus
- hippocampal formation
- Septal nuclei, basal forebrain
- medial orbitofrontal cortex
What does the olfactory system and hypothalamus offer with regards to our emotions?
- appetitive states
- emotional and motivational aspects of smell
What does the hypothalamus and brainstem offer with regards to our emotions?
- autonomic and breathing control
What does the mediodorsal nucleus of thalamus offer with regards to our emotions?
- fear reflex
- emotional learning
What does the limbic cortex and hypothalamus offer with regards to our emotions?
- neuroendocrinological modulation - modulates release of certain hormones in response to emotion
- prominent pathway in motherhood
What does the hippocampal formation offer with regards to our emotions?
- emotional aspects of memory
- important with forming memories that are associated with fear-inducing events
What does the Spetal nuclei and basal forebrain offer with regards to our emotions?
- processing of rewarding events
- synthesize AcH
What does the medial orbitofrontal cortex offer with regards to our emotions?
decision-making and emotion
- modulation of bodily changes associated with emotion in fight or flight - as we are making decisions
What is the function of the anterior cingulate cortex?
Regulates autonomic and endocrine responses, pain perception, and selection and initiation of motor movements
What is the function of the posterior cingulate cortex?
- recall of autobiographical memories - more when they have an emotional quality to them
