17. Thalamus

June 14, 2015 by Dr. Tangen Leave a Comment

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

The 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 behavior.

Here’s what is included in this lesson:

how the thalamus aids perception
how the hypothalamus impacts hunger & thirst
how the basal ganglia regulate processes
diseases of the limbic system

Read chapter 7 of Kalat’s Biological Psychology

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Here are the resources you need:

cluster
slides
terms
notes
quiz
video

SLIDES

TERMS

acromegaly
adenohypophysis
adrenaline (epinephrine)
adrenocorticotropic hormone
anterior
anterior hypothalamic nucleus
audition
Babinski-Fröhlich syndrome
basal ganglia
cerebral palsy
cortisol
Cushing’s disease
diabetes insipidus
disinhibition principle
dorsal thalamus
dorsomedial hypothalamic nucleus
epithalamus
eye movements
fatal familial insomnia
fight-flight
foreign accent syndrome
Frolich’s syndrome
ganglia
GHRH
GnRH
growth hormone-releasing hormone (GHRH)
hemiballismus
Huntington’s disease
hyperpituitarism (adenoma)
hyperthyroidism
hypopituitarism
hypothalamic infantilism-obesity
hypothalamus
inferior colliculus
kinesia paradoxica
Korsakoff’s dyndrome
lateral geniculate nucleus (LGN)
lateral hypothalamus
lateral preoptic nucleus
Launois-Cleret syndrome
limbic system
magnocellular neurons (large)
master endocrine gland
medial geniculate nucleus (MGN)
medial preoptic nucleus
medium spiny
motivation
neurohypophysis
nuclei
pallidum
paralysis of will
Parkinson’s disease
parvocellular neurons
perceived threat
Pickardt-Fahlbusch syndrome
pituitary gland
pituitary stalk (infundibular stem)
posterior
reticular nucleus
secretes ACTH
secretes ADH (antidiuretic hormone)
secretes Beta-endorphin
secretes FSH (follicle-$ hormone)
secretes growth hormone (GH or HGH)
secretes hormones
secretes LH (lutropin)
secretes LTH (luteotropic)
secretes Oxytocin
secretes Prolactin (PRL)
secretes TSH
secretion of melatonin (pineal)
sexual infantilism
sexually dimorphic nucleus
Sheehan syndrome
somatostatin
somatotropin
stress hormone
striatum
substantia nigra
subthalamic nucleus
superior colliculus
suprachiasmatic nucleus
thalamic syndrome
thalamo-corticl-talamic circuits
thalamus
thyroid gland
thyroid-stimulating hormone
tuberal
vasopressin
ventral thalamus
ventro-medial hypothalamus
VTA→NA reward system

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
- Audition
  - Medial geniculate nucleus (MGN)
    - Auditory connection
    - From inferior colliculus to primary auditory cortex
- 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
  - Thalamic Syndrome
    - Caused by stoke
    - One-sided burning sensation
    - Mood swings
- 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
  - Lateral
    - Thirst & hunger
- 2. Tuberal
  - Medial
    - Dorsomedial Hypothalamic Nucleus
    - Blood pressure & heart rate
    - Growth hormone-releasing hormone (GHRH)
  - Lateral
    - Thirst & hunger
- 3. Posterior
  - Medial
    - Memory
    - Blood pressure, pupil dilation, shivering
  - Lateral
    - Hunger
      - Damage to this area
        
        reduced food intake
      - Stimulating
        
        Causes a desire to eat
    - 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
    - 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
- Hypothalamus & Sex
  - Differences to brain structure
  - No cause-effect summary
  - Differences in gender
  - Difference in sexual orientation
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
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
- 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
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
  - 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
  - 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

QUIZ

1. Which are components of the basal ganglia?
- a. substantia nigra
- b. pallidum
- c. striatum
- d. all of the above
2. Damage to the basal ganglia during 2^nd and 3^rd trimester causes:
- a. cerebral palsy
- b. Alzheimer’s
- c. Cushing’s
- d. diabetes
3. Fatal Familial Insomnia is a hereditary disease that causes the degeneration of the:
- a. reticular formation
- b. occipital lobe
- c. thalamus
- d. pons
4. When a large dog barks at you, which part of the brain triggers the fight-flight response:
- a. corpus collosum
- b. hypothalamus
- c. hippocampus
- d. cerebellum
5. Another name for adrenaline is:
- a. epinephrine
- b. glutamate
- c. dopamine
- d. GABA

For the answers: Click Here

17. Thalamus

A limbic limmerick?

SLIDES

TERMS

NOTES

QUIZ

VIDEO

DISCUSSION ITEM

A limbic limmerick?

SLIDES

TERMS

NOTES

QUIZ

VIDEO

DISCUSSION ITEM

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