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 ~

Anterior Pituitary-Adenohypophysis

Posterior Pituitary-Neurohypophysis

Hypothalamus

Pituitary StalkPituitary

hypophysis

G

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

Thirst

PVN & SON LH

Hypothalamus

Kidneys

ADH

A II

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 adrenal mammary thyroid ~

Hypothalamopituitary Portal System

Portal Systems Capillary beds Connected by a vein e.g. hepatic portal vein

Hypothalamus Anterior Pituitary ~

RH

PVN

G

GTH

TH

TH

TH

TH

PVN

RH

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? ~