Hormonal Control of Behavior

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Hormonal Control of Behavior

• Lecture 22

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Chemical Control of Brain

• Point-to-point control
• closed-circuit
• synapse
• fast, short-lived, local

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Chemical Control of Brain

• Diffuse control
• widespread control
• slower, longer lasting
• Diffuse modulatory systems
• Neuroendocrine system

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Hormones Behavior?

• Responses to a changing environment
• detect stimulus ? make response
• Effectors
• muscles
• glands
• Autonomic N.S.
• Homeostasis

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2 Types of Glands

• Exocrine
• ducts
• sweat, tears, etc.
• Endocrine
• ductless
• hormones
• released into blood

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Neurohormones

• Interact with nervous system
• Chemical message
• Neurotransmitters (NTs)
• Hormones
• Pheromones
• Whats the difference?

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Neurohormones

• Similarities
• chemical messengers
• act at receptors
• influence behavior
• Differences
• medium
• distance traveled
• time course

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Neurohormone Properties

• Neurons release molecules into blood
• Long distances
• Slower
• Longer lasting effects
• Widespread

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Function

• Developmental
• sex differentiation
• testosterone, estradiol
• Regulatory
• Insulin, CCK, etc.
• Vasopressin, Oxytocin

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Types of Neurohormones

• Amino acid-derived hormones
• e.g. epinephrine
• released from adrenal medulla
• Protein Peptide Hormones
• Bind to membrane receptors
• Activate the 2nd messenger system

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Types of Neurohormones

• Steroid Hormones
• Derived from cholesterol
• Soluble in lipids
• Bind to cytoplasmic receptors
• regulates gene expression
• e.g. sex hormones

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Neuroendocrine System

• Brain
• Hypothalamus
• Releasing Hormones
• Pituitary gland
• Anterior tropic hormones
• Posterior neurohormones
• Glands - Hormones

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Pituitary Gland

• 2 parts
• different developmental origins
• Anterior pituitary (adenohypophysis)
• no axons from hypothalamus
• parvocellular neurosecretory cells
• portal system
• Posterior pituitary (neurohypophysis)
• axons from hypothalamus
• magnocellular secretory cells

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Hypothalamus
Pituitary Stalk
Pituitary hypophysis
Posterior Pituitary- Neurohypophysis
Anterior Pituitary- Adenohypophysis
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Supraoptic nucleus
PVN
Posterior Pituitary
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Posterior Pituitary Neurohormones

• Magnocellular neurosecretory cells
• Supraoptic Paraventricular Nuclei
• Neurons fire ? Neurohormones released
• Transported down axons
• to posterior pituitary
• Peptide Neurohormones
• Oxytocin
• Vasopressin

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Oxytocin

• Induces uterine contractions
• child birth
• orgasm during sex
• Triggers lactation
• letdown reflex
• triggered by touch, sight, sound

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Antidiuretic Hormone (ADH)

• AKA Vasopressin
• Responds to blood pressure
• Induces vasoconstriction
• Promotes water retention
• Kidney Renin release
• Angiotensin I ? Angiotensin II
• to kidneys subfornical organ

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Subfornical Organ

• Subfornical organ - SFO
• Dorsal 3d ventricle
• lacks blood-brain barrier
• A II receptors
• Output to
• Supraoptic paraventricular nuclei
• ADH release
• lateral hypothalamus (LH)
• thirst ? drinking behavior

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Kidneys
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ADH (Vasopressin)

• Alcohol suppresses ADH release
• Damage ? diabetes insipidus
• Symptoms
• copius urination
• intense thirst

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Anterior Hypothalamus

• Primordial tissue from roof of mouth
• No axons from hypothalamus
• Parvocellular neurosecretory cells
• Releasing hormones
• triggers release of tropic hormones
• Tropic hormones ? various glands
• gonads adrenal
• mammary thyroid

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Hypothalamopituitary Portal System

• Portal Systems
• Capillary beds
• Connected by a vein
• e.g. hepatic portal vein
• Hypothalamus ? Anterior Pituitary

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PVN
RH
G
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PVN
RH
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Cortisol Regulation

• Adrenal glands
• medulla NE E
• cortex cortisol
• Regulation of cortisol
• steroid
• fight/flight immunosuppression
• stress response
• Receptors widely distributed

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Cortisol Regulation

• Hypothalamus
• Corticotropin-releasing hormone (CRH)
• Anterior pituitary
• Adrenocorticotropin (ACTH)
• Adrenal cortex
• Cortisol
• Negative feedback to hypothalamus
• cortisol inhibits own release

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Sex Hormones

• Hypothalamus
• Gonadotropin-releasing hormone - GRH
• isolated from pig hypothalami
• Anterior Pituitary -
• Gonadotropins
• Follicle stimulating hormone - FSH
• Lutenizing hormone - LH

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Gonadotropins Target Cells

• Gonads
• Testes -
• Androgens -Testosterone
• Ovaries -
• Estrogens
• Estradiol and Progesterone

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Gonadotropin Release Patterns

• Sex differences
• FSH LH both sexes
• Males ? steady
• Females
• cyclical
• Transplant male pituitary into female?