Transcript BN22 hormonal control

Hormonal Control
of Behavior
Lecture 22
Chemical Control of Brain

Point-to-point control
 closed-circuit
 synapse
 fast, short-lived, local ~
Chemical Control of Brain
Diffuse control
 widespread control
 slower, longer lasting
 Diffuse modulatory systems
 Neuroendocrine system ~

Hormones & Behavior?

Responses to a changing environment
detect stimulus  make response
Effectors
 muscles
 glands
 Autonomic N.S.


Homeostasis ~
2 Types of Glands

Exocrine
 ducts


sweat, tears, etc.
Endocrine
 ductless
 hormones
 released into blood ~
Neurohormones
Interact with nervous system
 Chemical message
 Neurotransmitters (NTs)
 Hormones
 Pheromones
 What’s the difference? ~

Neurohormones
Similarities
 chemical messengers
 act at receptors
 influence behavior
 Differences
 medium
 distance traveled
 time course ~

Neurohormone Properties

Neurons release molecules into blood
 Long distances
 Slower
 Longer lasting effects
 Widespread ~
Function
Developmental
 sex differentiation
 testosterone, estradiol
 Regulatory
 Insulin, CCK, etc.
 Vasopressin, Oxytocin ~

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 ~

Types of Neurohormones

Steroid Hormones
 Derived from cholesterol
 Soluble in lipids
 Bind to cytoplasmic receptors
regulates gene expression

e.g. sex hormones ~
Neuroendocrine System
Brain
 Hypothalamus
 Releasing Hormones
 Pituitary gland
 Anterior: tropic hormones
 Posterior: neurohormones
 Glands - Hormones ~

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 ~

Hypothalamus
Pituitary Stalk
Pituitary
hypophysis
G
Anterior PituitaryAdenohypophysis
Posterior PituitaryNeurohypophysis
Supraoptic
nucleus
PVN
Posterior Pituitary
Posterior Pituitary: Neurohormones
Magnocellular neurosecretory cells
 Supraoptic & Paraventricular Nuclei
 Neurons fire  Neurohormones released
 Transported down axons
 to posterior pituitary
 Peptide Neurohormones
 Oxytocin


Vasopressin ~
Oxytocin
Induces uterine contractions
 child birth
 orgasm during sex
 Triggers lactation
 “letdown reflex”
 triggered by touch, sight, sound ~

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 ~

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 ~

SFO
Hypothalamus
PVN & SON
A II
LH
ADH
Thirst
Kidneys
ADH (Vasopressin)
Alcohol suppresses ADH release
 Damage  diabetes insipidus
 Symptoms
• copius urination
• intense thirst ~

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
mammary
adrenal
thyroid ~
Hypothalamopituitary Portal System
Portal Systems
 Capillary beds
 Connected by a vein
 e.g. hepatic portal vein
 Hypothalamus  Anterior Pituitary ~

PVN
RH
G
PVN
TH
RH
TH
G
TH
TH
TH
Cortisol Regulation
Adrenal glands
 medulla: NE & E
 cortex: cortisol
 Regulation of cortisol
 steroid
 fight/flight & immunosuppression
 stress response
 Receptors widely distributed ~

Cortisol Regulation
Hypothalamus
 Corticotropin-releasing hormone (CRH)
 Anterior pituitary
 Adrenocorticotropin (ACTH)
 Adrenal cortex
 Cortisol
 Negative feedback to hypothalamus
 cortisol inhibits own release ~

Sex Hormones
Hypothalamus
 Gonadotropin-releasing hormone - GRH
 isolated from pig hypothalami
 Anterior Pituitary 
Gonadotropins

• Follicle stimulating hormone - FSH
• Lutenizing hormone - LH ~
Gonadotropins: Target Cells
Gonads
 Testes  Androgens -Testosterone
 Ovaries  Estrogens
 Estradiol and Progesterone ~

Gonadotropin Release Patterns
Sex differences
 FSH & LH both sexes
 Males  steady
 Females
 cyclical
 Transplant male pituitary into female? ~
