Limbic System Flashcards
What are the functions of the hypothalamus?
CoordinatesDrive- related behaviours.
The hypothalamus is concerned with AUTONOMIC, ENDOCRINE, EMOTIONAL and SOMATIC functions that are generally designed to maintain our INTERNAL ENVIRONMENT.
-emotional behaviours, rage, sleep , sex
Describe the autonomic anatomical locations of the hypothalamus: What is SUPERIOR? INFERIOR? ANTERIOR? POSTERIOR? MEDIAL? LATERAL?
Superior: Hypothalamic sulcus
Inferior: Optic chiasm, pituitary gland, mammillary bodies
Anterior: lamina terminalis (membranous structure)
Posterior: tegmentum of the midbrain
Medial: 3rd ventricle
Lateral: Internal Capsule, basal forebrain
Fornix runs through the hypothalamus
The hypothalamus is subdivided into 3 zones, what are these and what are their functions?
Subdivisions of the hypothalamus 1. Periventricular zone 2. Medial Zone • Anterior region (chiasmatic) • Middle region (tuberal) • Posterior region (mammillary) 3. Lateral zone
What is the function of they hypothalamus?
esp.
Suprachiasmatic nucleus &
Ventromedial nucleus
- Ventromedial Nucleus (VMN): satiety centre, lateral hypothalamic regions: feeding centre
- Suprachiasmatic nucleus
• Expresses melatonin receptors, has direct retinal input
• Circadian rhythms in sleeping and waking, body temperature, hormone secretion - Other hypothalamic nuclei regulate sleep-wake cycle, body heat conservation, sympathetic and parasympathetic output.
Hypothalamus can be split into anterior and posterior areas
what does the anterio area do?
Anterior areas of hypothalamus active parasympathetic nervous system: rest and digest
Posterior areas of the hypothalamus activate sympathetic nervous system: fight/flight
What are the FOUR SITES where the BBB is lacking?
- Subfornial organ, and the vascular organ of the lamina terminalis – are for fluid balance
- Median eminence: neuroendocrine function
- Pineal gland- melatonin secretion
- Fenestrations and pinocytotic vesicles in endothelial cells.
What is the function of the lamina terminalis?
The vascular organ of the lamina terminalis detects changes in blood osmolality. The subfornical organ detects changes in angiotensin II (hence increase in bp, increase in blood volume)
What are some AFFERENTS that go into the hypothalamus?
limbic system (hippocampus, amygdala, orbital cortex)
Sensory input: Retina, olfactory cortex, taste, pain and temperature.
Physical inputs: blood temp, hormone levels
Outputs of hypothalamus
Widespread cortical structures
hippocampus
Pituitary gland
Brain stem and spinal cord (pattern generators and autonomic motor neurons)
Describe the LIMBIC SYSTEM
Is a portion of the brain concerned with feelings, emotional responses and behavior. It is composed of interconnecting components;
- Given function may be carried out by several components acting in cooperation,
- One component may participate in several functions.
The limbic system serves as an interconnection between thinking in the NEOCORTEX and HYPOTHALAMUS
What are the components of the LIMBIC SYSTEM?
- Amygdala
- Hippocampus
- Fornix
- Cingulate cortex
Describe the PAPEZ circuit
what does it control?
Thought to be the route through which neocortex influences the hypothalamic and limbic activity. Cortical control of emotional activity. It is a simple circuit, from
hippocampus -(fornix) ->mamillary body -(mamillothalamic tract) ->anterior nucleus of thalamus - (internal capsule) -> cingulate gyrus -> entorhinal cortex -> Hippocampus
What is the function of the amygdala?
Located deep to the uncus, is a collection of several nuclei, which relate environmental stimuli to coordinate behavioural, autonomic and endocrine responses for self preservation. Eg. Responses to physical and emotional stressors. Conventially associated with the emotion of fear.
How does visceral sensory input get to the amygdala?
from the lateral geniculate nucleus, medial geniculate nucleus, solitary nucleus etc -> hypothalamus -> amygdala
What are some efferent pathways from the amygdala?
• Hypothalamus- stress hormone secretion
• Various autonomic centres
1. PAG- antinociception
2. Parabrachial nucleus- hyperventilation
3. Parasympathetic dorsal motor n. X –bradycardia/fainting
4. Sympathetic preganglionic neurons in the spinal cord
Ventral amygdalofugal pathway to the hypothalamus and ventral striatum (includes the nucleus accumbens – implicated in reward/addictive behaviours)
Hippocampus: what does it form the floor of? What is it made up of (3 layers) What is it under What is it lateral to?
- Forms the floor of the inferior horn of the lateral ventricle.
- Made up of the: subiculum + hippocampus proper + dentate gyrus
- 3 layered allocortex
- Folded under medial aspect of temporal lobe
- Forms medial wall of inferior horn of the lateral ventricle
Fornix
what is it?
What are the parts of it?
is a C-shape bundle of axon that carries signals from the hippocampus to the mammillary bodies OR septal nuclei.
Parts: Crus, body
What are some efferents of the hippocampus?
- Fornix to:
- mammillary bodies,
- septal nuclei,
- ventral striatum,
- hypothalamus - Entorhinal cortex, to:
- amygdala,
- or backward along the cingulum to the cingulate gyrus.
…. Mamillary bodies –mammillotegmental tract (terminate in PAG), mammillothalamic tract. Mamillary and some hippocampal degeneration in chronic alcoholics -> memory loss. (called Korskoff’s Syndrome)
Describe some afferents trveling to the hippocampus
Afferents to the hippocampus
- Entorhinal cortex in the parahippocampal gyrus which collects inputs from :
- cingulate, temporal, orbital cortices, amygdala and olfactory cortex. - Fornix from:
- .Septal nuclei
- and hypothalamus
- and from the contralateral hippocampus
What are some macroscopic features of Alzheimers?
- Most common type of dementia
- Memory and cognition impairment
- Shrinkage in brain zie, wide suli
- Enlarged ventricles
- Shrinkage of hippocampus, language areas
What are the types of memory?
Explicit (declarative) memory – recalling facts and events.
Implicit (procedural) memory – eg. Improving your tennis game.
Working memory
What is used in Explicit memory?
Bilateral hippocampal damage -> permanent anterograde amnesia
Absence of conscious recall of newly acquired information for more than a few minutes
What is used in implicit memory?
• Cerebellum (or component of motor system) appears to be the primary store
What is used in working memory?
• Prefrontal cortex –
Storage of old memories?
