Ghhh
A limbic limmerick?
-
There once was a system called limbic
-
it’s where fears and emoting are quick
-
buried deep in the head
-
and hardly well bred
-
it forced me to write this dumb limerick
HhhThe limbic system is a combination of the thalamus, hypothalamus, pituitary and basal ganglia or nuclei. Not well understood but highly interconnected, these structures indirectly regulate a lot of
NOTES
- Thalamus
- Sits on top of brainstem
- Near center of brain
- Nerve fibers project in all directions
- Difficult to map connections
- Organized in 3D
- Cortex is organized in 2D
- Surrounds 3rd ventricle
- Each half is shape & size of walnut
- Relays sensory & motor signals
- Regulation of consciousness
- Sleep, and alertness
- Lots of information from cortex
- Lots of info to other brain parts
- Multi-function switchboard
- Every sense but smell
- Vision
- Lateral geniculate nucleus (LGN)
- Pre-process and relay
- Lateral geniculate nucleus (LGN)
- Audition
- Medial geniculate nucleus (MGN)
- Auditory connection
- From inferior colliculus to primary auditory cortex
- Medial geniculate nucleus (MGN)
- Impacts sleep & wake
- Reciprocal connections w/ cortex
- Thalamo-corticl-talamic circuits
- Provides channels
- From basal ganglia & cerebellum
- To cortical motor areas
- Impacts antisaccade eye-movement
- Damage
- Korsakoff’s Syndrome
- Can be caused by damage to thalamus
- Fatal Familial Insomnia
- Hereditary disease
- degeneration of thalamus
- gradual loss of ability to sleep
- Leads to total insomnia & death
- Hereditary disease
- Thalamic Syndrome
- Caused by stoke
- One-sided burning sensation
- Mood swings
- Korsakoff’s Syndrome
- Four parts
- Ventral thalamus
- Dorsal thalamus
- Epithalamus
- Hypothalamus
- 1. Ventral thalamus
- reticular nucleus
- GABAergic cells
- inhibit relay cells
- flush against lateral surface of dorsal thalamus
- 2. Dorsal thalamus
- Bundle of 15 relay nuclei
- Send signals to cortex
- 3. Epithalamus
- Interconnecting fibers to pineal gland and limbic system
- Secretion of melatonin (pineal)
- Emotion (basil ganglia)
- 4. Hypothalamus
- In action
- Large dog barks at you, body reacts
- Neural response
- Hormonal response
- Impacts
- Triggers adrenal glands to release adrenaline and cortisol
- Adrenaline (epinephrine)
- Increase heart rate
- Elevates blood pressure
- Cortisol
- Primary stress hormone
- Increases blood glucose
- Improves brain’s use of glucose
- Increases availability of tissue repair substances
- Shut down nonessential functions
- Anything not needed in fight-flight
- Alters immune system
- Suppresses digestive system
- Once Perceived Threat Is Gone
- Resets
- Unless it’s consistent threat
- Depressed immune system, more likely:
- Digestive problems
- Sleep problems
- Heart disease
- Obesity
- Located below thalamus
- About the size of an almond
- Contains small nuclei
- Each with different functions
- Links nervous & endocrine sys
- Secretes hormones
- stimulate or inhibit secretion by pituitary
- Controls
- body temp, hunger, thirst, sleep, circadian rhythm and fatigue
- Three parts
- Anterior
- Tuberal
- Posterior
- 1. Anterior
- Medial
- Medial preoptic nucleus
- Regulates release of gonadotropic hormones
- Sexually dimorphic nucleus
- releases GnRH
- differential development of sexes
- in-utero testosterone levels
- Anterior Hypothalamic Nucleus
- panting, sweating
- Suprachiasmatic Nucleus
- Circadian rhythms
- Medial preoptic nucleus
- Lateral
- Thirst & hunger
- Medial
- 2. Tuberal
- Medial
- Dorsomedial Hypothalamic Nucleus
- Blood pressure & heart rate
- Growth hormone-releasing hormone (GHRH)
- Lateral
- Thirst & hunger
- Medial
- 3. Posterior
- Medial
- Memory
- Blood pressure, pupil dilation, shivering
- Lateral
- Hunger
- Damage to this area
- reduced food intake
- Stimulating
- Causes a desire to eat
- Damage to this area
- Blood sugar level drops
- Receptors in blood signal lateral hypothalamus
- Brain areas fire in unison
- creating the sensation of hunger
- Blood sugar level increases
- Signals ventro-medial hypothalamus
- Two structures
- lateral hypothalamic area
- Hunger
- Lateral preoptic nucleus
- Non-REM sleep
- lateral hypothalamic area
- Damage
- Frolich’s Syndrome
- decreased levels in GnRH
- defects of feeding centers of hypothalamus
- increase food and calorie intake
- It is characterized by:
- Affects males mostly
- No endocrine problems
- Mature normally after puberty
- Growth retardation
- Atrophy of gonads
- Altered secondary sexual characteristics
- Other names
- Babinski-Fröhlich syndrome
- Hypothalamic Infantilism-Obesity
- Launois-Cleret Syndrome
- Sexual Infantilism
- Frolich’s Syndrome
- Hunger
- Medial
- Hypothalamus & Sex
- Differences to brain structure
- No cause-effect summary
- Differences in gender
- Difference in sexual orientation
- In action
- Suprachiasmatic Nucleus (SCN)
- Internal clock
- Largest in heterosexual men
- Smaller in homosexual men
- Smallest in women
- Sexually Dimorphic Nucleus (SDN)
- In anterior hypothalamus
- Twice as large in heterosexual men and homosexual women, in terms of volume but not number of neurons.
- Responds to smelling common odors
- scent of testosterone found in male sweat
- homosexual men and heterosexual women
- scent of estrogen found in female urine
- heterosexual men and homosexual women
- scent of testosterone found in male sweat
- Pituitary gland
- Protrusion at bottom of hypothalamus
- Size of a pea
- Connects to hypothalamus
- Thin tube called pituitary stalk or infundibular stem
- “Master” endocrine gland
- Impacts other glands
- But controlled by hypothalamus
- Two parts
- 1. Anterior
- adenohypophysis
- parvocellular neurons (small)
- Secretes growth hormone (GH or HGH)
- Also called somatotropin
- $ by GHRH (from hypothal.)
- Growth hormone releasing hormone
- Iinhibited by somatostatin
- From hypthal.
- Secretes TSH
- Thyroid-stimulating hormone
- Secretes ACTH
- Adrenocorticotropic hormone
- Secretes FSH (follicle-$ hormone)
- Secretes LH (lutropin)
- Secretes Prolactin (PRL)
- Secretes Beta-endorphin
- Secretes LTH (luteotropic)
- 2. Posterior
- neurohypophysis
- magnocellular neurons (large)
- Secretes Oxytocin
- Birthing, bonding, wound healing, empathy, anxiety
- Secretes ADH (antidiuretic hormone)
- Also called vasopressin
- Function
- Secretes hormones to control:
- Growth & metabolism
- Pregnancy & sex organs
- Thyroid gland
- Water regulation
- Temperature
- Endorphin
- Secretes hormones to control:
- Diseases
- Acromegaly
- too much growth hormone
- Cushing’s
- Too much adrenocorticotropic hormone
- Growth hormone deficiency
- Too little growth hormone
- Syndrome of inappropriate antidiuretic hormone
- Too much vasopressin
- Diabetes insipidus (cell diabetes)
- too little vasopressin
- Sheehan syndrome
- Too little of any of the pituitary hormones
- Pickardt-Fahlbusch syndrome
- Too little of any of the pituitary hormones
- Too much prolactin
- Hyperpituitarism (adenoma)
- Too much of any of the pituitary hormones
- Hypopituitarism
- Too little TSH (thyroid $ hormone)
- Vasopressin
- Hyperthyroidism
- Too much TSH
- Almost always a pituitary adenoma
- Acromegaly
- Basal ganglia
- In PNS = ganglia
- In CNS = nuclei
- How they work
- Disinhibition principle
- If no input = steady fire at high rates
- Distinct masses of gray matter
- deep in brain
- not far from thalamus
- Left-right sides mirror each other
- Group of nuclei
- Work together as functional unit
- Interact with cortex, thalamus, etc
- Neurotransmitters
- Inputs use Glutamate
- Outputs use GABA
- Internal connections use Dopamine or ACh
- 4 structures
- Striatum
- Pallidum (w 2 nuclei)
- Substantia nigra (2 parts)
- Subthalamic nucleus
- Two large parts
- Striatum & Pallidum
- Two smaller parts (& farther back)
- Substantia Nigra & Subthalamic
- 1. Striatum
- Largest
- Looks striped
- Large & small bundles of fibers
- White matter
- Looks like two blobs of gray separated by large white stripe
- Complex internal organization
- Vast majority of neurons (96%?)
- lots of dendritic spines
- small cell bodies
- Medium spiny
- GABAergic
- Inhibitors
- Two types of medium spiny
- Substance P & dopamine D1
- Direct pathway
- Enkephalin & dopamine D2
- Indirect pathway
- Substance P & dopamine D1
- Organized in 3D
- Cortex is layered; organized 2D
- Basal ganglia impacts
- Voluntary motor control
- Inhibits motor systems
- Procedural learning
- Eye movements
- Habits
- Rewards?
- Internal connections use dopamine
- VTA→NA dopamine connection
- Ventral Tegmentum Area
- Dopaminergic neurons
- Start of reward system
- Nucleus Accumbens
- Part of striatum
- Ventral Tegmentum Area
- Increase effectiveness of signal
- Cocaine
- Nicotine
- Amphetamines
- Overactive in schizophrenia?
- Eye movements
- Lots of brain regions at work
- Superior Colliculus
- layered structure
- 2D retinal maps
- Gets inhibitory effect from basal ganglia (SNr)
- Pause their inhibition when eyes
- Action selection?
- Which behavior to do when
- Parkinson’s disease
- Major loss of dopaminergic cells in the substantia nigra
- Gradual loss of the ability to initiate movement
- Motivation
- Can do components of movement
- Hunger fails to initiate movements
- Not switched on: “paralysis of will”
- kinesia paradoxica
- Moves easily in emergency
- Immobile after issue passed
- Motivation
- VTA to NA reward system
- Animals with $ electrodes
- Bar-pressing
- Humans show increased action
- addictive drugs
- good-tasting food
- sex
- Animal with severe basal ganglia damage won’t move toward food
- Even if placed within inches
- Chew & swallow if put in mouth
- Huntington’s disease
- Major loss of medium spiny neurons in striatum
- inability to prevent parts of the body from moving unintentionally
- Hemiballismus
- Damage to the subthalamic nucleus
- uncontrollable flinging movements of arms and legs
- Cerebral palsy
- Damage to basal ganglia during 2nd and 3rd trimester
- Foreign accent syndrome
- Some combination of problems in cerebellum, Broca’s area & basal ganglion
- Caused by stroke or injury
- Mispronunciation of words
- Listener’s hear it as accent
- speaking native with accent
- Not new vocabulary
- Sufferer’s may imitate other aspects of accent to normalize the syndrome
