Week 12 - hippocampus and limbic system - finished Flashcards
What % of brain mass does the hypothalamus contribute?
Less than 1%
What % of brain mass does the hypothalamus contribute?
Where is the hypothalamus located?
What else is it connected to and how?
Beneath the thalamus, in the walls of the 3rd ventricle and is connected to the pituitary by a stalk
What is the function of the hypothalamus?
Maintains homeostasis.
Also serves the limbic system for emotional expression
- fear
- depression
- pleasure
- rage
What is homeostasis and what are some examples
Maintaining consistent internal conditions within a very narrow range: Temperature pH Blood volume Blood pressure Blood oxygen Blood glucose Electrolyte balance & salinity
What is the structure of the hypothalamus?
Each side of the hypothalamus is divided into 3 zones:
- lateral
- medial
- periventricular
What are the functions of the medial and lateral zones of the hypothalamus?
They connect the hypothalamus to the brainstem, spinal cord and the cortex for the expression and experience of certain emotions.
What does the periventricular zone of the hypothalamus do?
1) Regulated the output of the ANS
2) Influences the pituitary and endocrine regulation
3) Controls circadian rhythms via the suprachiasmatic nucleus
In order to perform these functions it has 3 functionally distinct groups of cells.
Where is the periventricular zone of the hypothalamus located?
Its the area directly surrounding the 3rd ventricle
How many groups of cells are found in the periventriular zone? What are their functions?
3
1) Suprachiasmatic nucleus
- direct retinal input
- monitors daily light/dark cycles
- synchronises circadian rhythms.
2) Cells for the control of the ANS
Connections between the periventricular zone and the autonomic preganglionic nuclei in the brainstem (PS) and spinal cord (S) are essential to autonomic control
Integrates information about body status, anticipates the body’s needs and coordinates a set of both neural and hormonal outputs
3) Neurosecretory neurons:
Axons of neurosecretory neurons project down into the pituitary stalk
Neurohormones are secreted directly into the blood stream
Posterior Pituitary = Neurohypophysis -> CNS
Anterior Pituitary = Adenohypophysis -> gland
What is the solitary nucleus and tract? Where are they located?
Located in the medulla and receives extensive input from the hypothalamus
It is important for the autonomic control and possibly responsible for almost normal control of some autonomic functions even in the absence of the hypothalamus
It coordinates sensory information form the internal organs and outputs to the autonomic brainstem nuclei
What are the functions and divisions of the ANS?
Functions:
Automatic
Involuntary
Complex and highly coordinated functions
Divisions:
Sympathetic
Parasympathetic
Enteric
SNS information:
Fight, Flight, Fright & Sex
Preganglionics from intermediolateral cell column in the thoracolumbar cord
Exit via the ventral root to synapse at the postganglionics
Postganglionics from sympathetic chain ganglia, out with spinal nerves via gray rami communicans
Sympathetic influence:
Increase heart rate
Peripheral vasodilation/ GIT vasoconstriction
Orgasm and ejaculation
Pupillary dilation
Increase glucose production and mobilisation
Dilation of airways
Stimulation of adrenal adrenalin & noradrenalin release
PSNS information:
Rest & digest
Growth, immune responses & energy storage
Preganglionics from autonomic nuclei of brainstem and sacral spinal cord, travel with various cranial & sacral spinal nerves
Parasympathetic ganglia tend to sit within/ local to their target tissues, it is from here that the postganglionic axons extend
Parasympathetic influence
Decrease heart rate
Pupillary constriction
Stimulates salivation and lacrimation
Constricts airways
Stimulates GITl vasodilation/ Peripheral vasoconstriction
Stimulates digestion & insulin release
Stimulates sexual arousal - erection not ejaculation
Enteric division of ANS information:
Embedded in the wall of the oesophagus, stomach, intestines, pancreas and gall bladder are two interconnected plexuses for regulation of GIT function
Auerbach’s Plexus -> Myenteric Plexus
Meissner’s Plexus -> Submucosal Plexus
Both contain autonomic motor & sensory neurons
Contains approx # neurons as entire spinal cord
Can acts to regulate homeostasis with a great deal of autonomy but not entirely
Overall autonomic function:
Innervates secretory glands
Innervates heart to control heart rate, BP & flow
Innervates bronchi to meet O2 demands
Regulates digestive & metabolic functions of the liver, GIT & pancreas
Regulates function of the kidney, urinary bladder, intestines & rectum
Essential to sexual responses of the genitals and reproductive organs
Interacts with the immune system
Functions of the sympathetics & parasympathetics generally oppose each other, so substantial of stimulation of both is incompatible
The two systems function in parallel to balance excitation and inhibition for coordinated and graded control of body systems
What are magnocellular neurons and where are they found? Where do they extend and what do they release?
Found in the hypothalamus
Extend their axons all the way down the pituitary stalk and into the neurohypophysis
They release neurohormones directly into the capillary bed
- Oxytocin: uterine contraction in final stages of child birth and milk ejection from mammary glands
- Vasopressin/ADH: regulates blood volume & salt [C], is released in response to input from cardiovascular pressure receptors & salt [C] sensitive cells in the hypothalamus. Acts directly on the kidney to increase H20 retention & decrease urine production
What are parvocellular neurons and where do they extend? What do they secrete and what do these secretions influence?
They extend into the base of the pituitary stalk & secrete their neurohormones into the capillary bed of the hypothalamopituitary portal system which sits in the base of the stalk and the floor of the 3rd venticle
Neurohormones travel downstream and bind at hormone specific receptors on anterior pituitary cells to exert their effects and either stop or start pituitary hormone release
What hormones are released from the anterior pituitary?
GH: growth hormone TSH: thyroid stimulating hormone ACTH: adrenocorticotropic hormone PROLACTIN FSH: follicle stimulating hormone LH: leutinising hormone
What hormones are released from the anterior pituitary?
GH: growth hormone TSH: thyroid stimulating hormone ACTH: adrenocorticotropic hormone PROLACTIN FSH: follicle stimulating hormone LH: leutinising hormone
Where is the hypothalamus located?
What else is it connected to and how?
Beneath the thalamus, in the walls of the 3rd ventricle and is connected to the pituitary by a stalk
What is the function of the hypothalamus?
Maintains homeostasis.
Also serves the limbic system for emotional expression
- fear
- depression
- pleasure
- rage
What is homeostasis and what are some examples
Maintaining consistent internal conditions within a very narrow range: Temperature pH Blood volume Blood pressure Blood oxygen Blood glucose Electrolyte balance & salinity
Midbrain and aggression:
Hypothalamic projections to brainstem for ANS function via the medial forebrain bundle & the dorsal longitudinal fasciculus.
Lateral hypothalamus -> MFB -> ventral tegmental area -> stimulation -> predatory aggression -> lesion -> decrease predatory aggression
Interestingly: cut MFB -> can still elicit aggression -> aggression not completely reliant on hypothalamus
Medial hypothalamus -> DLF -> PAG -> stimulation -> increases affective aggression -> lesion -> decreases affective aggression
What are the functions of the medial and lateral zones of the hypothalamus?
They connect the hypothalamus to the brainstem, spinal cord and the cortex for the expression and experience of certain emotions.
What happens when the amygdala is removed?
attention / concentration
Where is the periventricular zone of the hypothalamus located?
Its the area directly surrounding the 3rd ventricle
Selective stimulation in humans: Severe narcolepsy:
Stim. -> hippocampus -> mild pleasure
Stim. -> midbrain tegmentum -> alert but unpleasant
Stim. -> septal area -> alert & pleasant
-> described as build up to orgasm
-> repeated stim. -> no orgasm
-> frustration
Selective stimulation in humans: Severe epilepsy
Stim. -> septal area -> pleasure/sexual feeling
Stim. -> midbrain tegmentum -> pleasure/happy drunk
Stim. -> amygdala -> mild pleasure
Stim. -> caudate nucleus -> mild pleasure
Stim. -> medial thalamus -> irritable feeling
-> about to recall a memory
-> repeated stim. -> didn’t recall
-> frustration
What are the functions and divisions of the ANS?
Functions:
Automatic
Involuntary
Complex and highly coordinated functions
Divisions:
Sympathetic
Parasympathetic
Enteric
Serotonin and aggression:
Serotonergic neurons from raphe nuclei to hypothalamus & other limbic structures via MFB
Study of rats & mice in isolation:
No Δ in absolute serotonin levels
Decreased turnover rate
Only noted in those that became hyperactive & aggressive, no Δ in those that didn’t develop aggression
♀ typically didn’t become aggressive & showed no Δ in serotonin turnover
Drugs that decrease serotonin release or synthesis tend to increased aggressive behaviour
PSNS information:
Rest & digest
Growth, immune responses & energy storage
Preganglionics from autonomic nuclei of brainstem and sacral spinal cord, travel with various cranial & sacral spinal nerves
Parasympathetic ganglia tend to sit within/ local to their target tissues, it is from here that the postganglionic axons extend
Parasympathetic influence
Decrease heart rate
Pupillary constriction
Stimulates salivation and lacrimation
Constricts airways
Stimulates GITl vasodilation/ Peripheral vasoconstriction
Stimulates digestion & insulin release
Stimulates sexual arousal - erection not ejaculation
Enteric division of ANS information:
Embedded in the wall of the oesophagus, stomach, intestines, pancreas and gall bladder are two interconnected plexuses for regulation of GIT function
Auerbach’s Plexus -> Myenteric Plexus
Meissner’s Plexus -> Submucosal Plexus
Both contain autonomic motor & sensory neurons
Contains approx # neurons as entire spinal cord
Can acts to regulate homeostasis with a great deal of autonomy but not entirely
Overall autonomic function:
Innervates secretory glands
Innervates heart to control heart rate, BP & flow
Innervates bronchi to meet O2 demands
Regulates digestive & metabolic functions of the liver, GIT & pancreas
Regulates function of the kidney, urinary bladder, intestines & rectum
Essential to sexual responses of the genitals and reproductive organs
Interacts with the immune system
Functions of the sympathetics & parasympathetics generally oppose each other, so substantial of stimulation of both is incompatible
The two systems function in parallel to balance excitation and inhibition for coordinated and graded control of body systems
What are magnocellular neurons and where are they found? Where do they extend and what do they release?
Found in the hypothalamus
Extend their axons all the way down the pituitary stalk and into the neurohypophysis
They release neurohormones directly into the capillary bed
- Oxytocin: uterine contraction in final stages of child birth and milk ejection from mammary glands
- Vasopressin/ADH: regulates blood volume & salt [C], is released in response to input from cardiovascular pressure receptors & salt [C] sensitive cells in the hypothalamus. Acts directly on the kidney to increase H20 retention & decrease urine production
What are parvocellular neurons and where do they extend? What do they secrete and what do these secretions influence?
They extend into the base of the pituitary stalk & secrete their neurohormones into the capillary bed of the hypothalamopituitary portal system which sits in the base of the stalk and the floor of the 3rd venticle
Neurohormones travel downstream and bind at hormone specific receptors on anterior pituitary cells to exert their effects and either stop or start pituitary hormone release
What hormones are released from the hypothalamus?
TRH: thyrotropin releasing hormone CRH: corticotropin releasing hormone GHRH: growth hormone releasing hormone GHIH: growth hormone inhibiting hormone GnRH: gonadotropin releasing hormone PIF: prolactin inhibiting factor
What hormones are released from the anterior pituitary?
GH: growth hormone TSH: thyroid stimulating hormone ACTH: adrenocorticotropic hormone PROLACTIN FSH: follicle stimulating hormone LH: leutinising hormone
What is involved in the limbic system?
Cingulate gyrus, cortex around the corpus callosum and the hippocampal formation.
What does lateral hypothalamic nucleus stimulation induce
Eating
What is Kluver- Bucy syndrome?
Bilateral temporal lobectomy:
Psychic blindness Oral tendencies Hypermetamorphosis Altered sexual behaviour Emotional changes/flattening -> most obvious is the loss of fear
Where is the amygdala found? What is its function?
Found: Subcortical nucleus formed from infolding of the infromedial temporal lobe cortex
All sensory systems input into the amygdala
Centre for the identification of danger or learned fear
The amygdala appears to give emotion content to memories rather than control the storage of memory
Intensely connected to the hypothalamus
Midbrain and aggression:
Hypothalamic projections to brainstem for ANS function via the medial forebrain bundle & the dorsal longitudinal fasciculus.
Lateral hypothalamus -> MFB -> ventral tegmental area -> stimulation -> predatory aggression -> lesion -> decrease predatory aggression
Interestingly: cut MFB -> can still elicit aggression -> aggression not completely reliant on hypothalamus
Medial hypothalamus -> DLF -> PAG -> stimulation -> increases affective aggression -> lesion -> decreases affective aggression
Anger and aggression:
As noted earlier the hypothalamus appears to be involved in aggression but several other factors appear to also be involved including:
The amygdala
The midbrain
The raphe nuclei of the brainstem (possibly due to their serotonin content)
What happens when the amygdala is removed?
attention / concentration
Negative reinforcement and displeasure centres:
Animals will actively avoid situations that stimulate certain areas of the brain or repeatedly perform activities which cease or decrease stimulation of these areas.
Some of these areas include:
Medial parts of the hypothalamus
Lateral midbrain tegmental area
Selective stimulation in humans: Severe narcolepsy:
Stim. -> hippocampus -> mild pleasure
Stim. -> midbrain tegmentum -> alert but unpleasant
Stim. -> septal area -> alert & pleasant
-> described as build up to orgasm
-> repeated stim. -> no orgasm
-> frustration
Neurotransmitters and emotions:
Several neurotransmitters have been implicated in emotional dysfunctions
Neurotransmitters implicated in common diseases with emotional components:
- Dopamine abnormalities are thought to be responsible for both schizophrenia and parkinson’s disease
- Noradrenalin and serotonin have both been implicated in depression
Serotonin and aggression:
Serotonergic neurons from raphe nuclei to hypothalamus & other limbic structures via MFB
Study of rats & mice in isolation:
No Δ in absolute serotonin levels
Decreased turnover rate
Only noted in those that became hyperactive & aggressive, no Δ in those that didn’t develop aggression
♀ typically didn’t become aggressive & showed no Δ in serotonin turnover
Drugs that decrease serotonin release or synthesis tend to increased aggressive behaviour
Suggested limbic system structures and their roles:
Thalamus:
lesions and stimulation can alter emotional reactivity probably because of connections to other limbic structures……… actual emotional function or just relay point to cortex ???
Fornix & Parahippocampal gyrus:
Thought to be important in connecting the limbic pathway
-> fornix connects hippocampus, septal areas and hypothalamus
-> hippocampus for laying down of memory (amygdala is thought to give emotional content to memories) hippocampus..emotional learning ???
Hypothalamus:
- > Lateral parts appears to be most active in pleasure and rage
- > Medial parts appear to be most active in displeasure and aversion. Also noted to give rise to the expression of uncontrollable laughter, is simply expression not genesis of the underlying emotion
Cingulate gyrus:
- Appears to regulate aggressive behaviour
- Co-ordinate emotional responses to pain & lesions result in indifference to pain
- Co-ordinates smells & sights with previous pleasant emotions
Locus ceruleus: is very poorly understood but has ascending inputs into all limbic structures. - Via these diffuse connections it appears to play a role in : Attention Arousal Sleep/wake cycles Learning & memory Anxiety Pain Mood Brain metabolism
Ventral tegmentum:
As noted in human stimulation studies and notes on dopamine, appears to be involved in reinforcement & reward, some people have attached sexual qualities to the feelings experienced
Cranial nerve nuclei:
Function in the expression of emotions
Septum:
Centre for orgasm
Note: ♀ = 4 ♂ = 1
Also assoc. with other levels & forms of pleasure but most notably those related to sexual experiences
Prefrontal lobe:
Bidirectional connections to thalamus and amygdala and other limbic structures
Prefrontal damage:
Loss of social responsibility
Decrease [C]
Prefrontal lobotomy:
No signs of joy
No sadness, hope or despair
No affection
