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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
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 ~
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 ~
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 ~