Sapolsky Chapter 2

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Sapolsky Chapter 2

• Glands, Gooseflesh, and Hormones

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Rejuvenation therapy

• Extracts of glands (i.e., testes), didnt work
  very well
• Testosterone not soluble in water, though it is
  bound to proteins that keep it dissolved in blood
  (not clear if testicular extracts had enough of
  those carrier proteins to do much good).

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So, what controls the glands?

• The pituitary! (Latin mucus) Pituitary is
  located over the nasal cavities, it was thought
  that it produced the mucus that flowed from the
  nose!

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Contest Roger Guillemin vs. Andrew Schally

• Isolate identify releasing and inhibiting
  hormones.
• Stupendously difficult, because of the size of
  the tissue
• They first collaborated, then separated and came
  to loathe each other. (Like Coke vs. Pepsi!)
  Great Slaughterhouse war was on.

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Contest Roger Guillemin vs. Andrew Schally

• Truckloads of brains ?thimblefuls of liquid ?
  purified and re-purified.
• 14 years later 1st releasing hormone was
  discoveredthyroid releasing hormone.
• Shared Nobel prize in 1976.
• Independent confirmation It might go faster if
  everyone worked together, but then they might
  share the same mistaken assumption

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Pituitary

• Sometimes referred to as the Master Gland
• But the brain is the REAL Master Gland. (How
  would you test this?)

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Pituitary

• Remove and place in a dish with nutrients. Does
  it secrete hormones?
• Yes and no!!!
• Too much of some and none of others!
• It needs the brain to tell it what to secrete.

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The brain controls the endocrine system

• LIMBIC SYSTEM
• A group of structures that form a border (Latin
  limbus) around the brain stem
• Important for motivated behaviors and emotions.

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MAJOR COMPONENTS OF LIMBIC SYSTEM

• AMYGDALA
• Latin almond
• Different nuclei ? aggression, sex, learning
  about rewards, stress
• Central nucleus ? major input to sympathetic
  nervous system (SNS)

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MAJOR COMPONENTS OF LIMBIC SYSTEM (CONT.)

• HIPPOCAMPUS (Latin sea horse)
• Stretches from middle of brain (below corpus
  callosum) down into the temporal lobes, ending
  adjacent to the amygdala.

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HIPPOCAMPUS
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Hippocampus functions

• Verbally-mediated memories in humans
• Spatial memories in rodents probably humans
• Processes some emotions
• Lowest seizure threshold of the brain
• temporal lobe seizures may ? episodes of
  uncontrollable violence, if they spread to the
  amygdala.

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MAJOR COMPONENTS OF LIMBIC SYSTEM (CONT.)
Cingulate gyrus
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Anterior cingulate gyrus
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Cingulate gyrus

• Latin girdle
• Lies just above corpus callosumthe bundle of
  fibers joining the two hemispheres
• With severe, long-lasting anxiety, surgical
  lesions are sometimes made in anterior cingulate
  gyrus
• Involved in working memory

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Hypothalamus

• Final common path for emotions.
• 4Fs feeding, fighting, fleeing, and reproductive
  behavior.
• Located on the floor of the brain, just behind
  the optic chiasm and above the pituitary, which
  it controls in two ways.

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Nuclei of the hypothalamus
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Hypothalamus

• Receives indirect sensory inputs from all sensory
  systems
• Sends neural outputs to various motor control
  nuclei
• Sends neural outputs to sympathetic and
  parasympathetic nervous systems
• Sends both neural and hormonal outputs to
  pituitary

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Hormonal communication

• Slower than neural communication
• But, more far-ranging
• Specificity depends on type of receptor located
  on target organs

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Hormonal communication
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Control of anterior pituitary
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Control of anterior pituitary

• Hormonal factors carried by blood from
  hypothalamus to ANTERIOR pituitary.
• Lots of scientists thought Harriss idea was
  bonkers. Your brain oozing hormones?
  Preposterous! (Sapolsky)

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Hormones of anterior pituitary

• Adrenocorticotropic hormone (ACTH) B-endorphin
• Follicle stimulating hormone (FSH)
• Luteinizing hormone (LH)
• Prolactin (PRL)
• Thyroid stimulating hormone (TSH)
• Growth hormone (GH)

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Hypothalamic control of anterior pituitary

• Hypothalamus corticotropin releasing hormone
  (CRH) ? ACTH endorphin
• Hypothalamus gonadotropin releasing hormone
  (GnRH) ? FSH LH
• Hypothalamus thyrotropin releasing hormone (TRH)
  ? TSH
• Hypothalamus GHRH ? GH (inhibited by
  somatostatin)
• Estrogen suckling stimuli ? PRL, and hypothal.
  dopamine inhibits its release.

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Intermediate lobe of pituitary

• Derivation is similar to anterior pituitary Both
  are derived from tissue from roof of the mouth.
• Main product melanocyte stimulating hormone
  (MSH)
• Promotes tanning
• Promotes sexual interest and ability
• Inhibits appetite

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Frog on right injected with MSH a few minutes
before picture
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Control of posterior pituitary (oxytocin
vasopressin)
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Control of posterior pituitary

• Neural lobe
• Neurons in hypothalamus send axons to post. pit,
  where they release oxytocin or vasopressin into
  systemic circulation.
• Development Post. Pit. descends from brain and
  joins Ant. Pit.

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Oxytocin Vasopressin

• 9-amino acid peptides that differ by 1 amino acid
  
• Oxytocin ? smooth muscle contractions for orgasm,
  childbirth, and milk let-down during nursing
• Vasopressin increases blood pressure and
  decreases the formation of urinethereby
  conserving water (a.k.a. ADH, antidiuretic
  hormone)

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Oxytocin Vasopressin

• Both are also transmitters in brain
• Oxytocin
• Decreases anxiety
• ? female male sexual behavior
• ? maternal behavior
• ? pair-bonding in prairie voles (esp. females)

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Oxytocin Vasopressin

• Vasopressin
• ? social recognition
• ? aggression
• ?pair-bonding in prairie voles (esp. males)

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Hormones of the stress response

• Epinephrine (adrenal medulla) and norepinephrine
  (SNS neurons)
• Glucocorticoidssteroids from the adrenal cortex
  Regulate blood glucose
• Controlled by CRH (corticotropin releasing
  hormone) from hypothalamus to Ant. Pit.
• Ant. Pit. then secretes ACTH (adrenocorticotropic
  hormone), which triggers glucocorticoid release.
  (In humans, the primary glucocorticoid is
  cortisol.)
• CRH ? ACTH ? glucocorticoid (GC)

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Hormones of the stress response

• Pancreas releases glucagon ? raises blood sugar
• Prolactin suppresses reproduction
• Endorphins, enkephalins ? analgesia
• Secretion of some hormones is inhibited
  testosterone, estrogen, progesterone, growth
  hormone (after brief increase), and insulin

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A few complications

• Variability among species (transient increase in
  growth hormone in humans)
• Time course Maybe glucocorticoids mediate
  RECOVERY from the stress

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A few more complications

• Variation from stressor to stressor
• SNS when subordinate animal is vigilant
  glucocorticoid system when animal gives up
• dichotomy between anxiety and depression
• Psychological context
• Getting better vs. getting worse
• Control/coping mechanisms

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Why growth hormone???

• Brief response
• Increases mobilization of stored energy
• Can be used for growth
• or for exercising muscle
• Somatomedin (needed for growth) is suppressed
• Therefore, increased energy for muscles

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Stress and the autonomic nervous system (ANS)

• Sympathetic nervous system (SNS)
• Name refers to chain of sympathetic ganglia along
  the sides of the thoracic and lumbar parts of
  spinal cord all inter-connected
• Therefore, all organs controlled by the SNS act
  in sympathy.

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Adrenal medulla and cortex
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Sympathetic Nervous System (cont.)

• Epinephrine (Greek on top of kidneys)
  Adrenaline (Latin on top of kidneys)
• Released when adrenal medulla is stimulated by
  SNS.
• Norepinephrine (epinephrine lacking its methyl
  group) noradrenaline. It is released by
  sympathetic nerves throughout the body.

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Synthesis of NE and Epi
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SNS

• SNS speeds heart rate and breathing, increases
  blood pressure, directs blood away from the
  intestines and other digestive organs and towards
  the heart, brain, and working muscles.

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Parasympathetic nervous system

• Located above and below the SNS, in the brain
  stem and sacral part of the spine.
• The PNS promotes digestion, growth, relaxation.
  Its neurotransmitter is acetylcholine.

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Comparison of SNS and PNS

• SNS PNS tend to be dominant at different times
• But, there is definitely overlap.
• During sexual excitement, PNS increases genital
  blood flow and lubrication.
• At the same time, the SNS is increasing heart
  rate, breathing, blood pressure, and finally
  triggers orgasm/ejaculation.

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Summary

• The pituitary controls the endocrine sys., but
  the brain controls the pituitary.
• The limbic system (amygdala, hippocampus,
  cingulate gyrus, plus some others) interpret the
  environment.
• Limbic system tells the hypothalamus about the
  significance of events.

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Summary

• The hypothalamus sends neural output to other
  brain areas and the post. pit.
• It also sends releasing or inhibiting hormones to
  ant. pit. via blood vessels.
• Anterior pituitary sends hormones to stimulate
  endocrine glands to release their own hormones.

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Summary

• SNS ? norepinephrine from neurons and epinephrine
  from adrenal medulla? fight or flight
• PNS ? digestion, relaxation slows HR, BP,
  breathing.