Lecture #20 Date _______

Chapter 45 ~ Chemical Signals in Animals

Regulatory systems

Hormone~ chemical signal secreted into body fluids (blood) communicating regulatory messages

Target cells~ body cells that respond to hormones

Endocrine system/glands~ hormone secreting system/glands (ductless); exocrine glands secrete chemicals (sweat, mucus, enzymes) through ducts

Neurosecretory cells~ actual cells that secrete hormones

Feedback mechanisms ~ negative and positive

Local regulators: cells adjacent to or near point of secretion

Growth factors ~ proteins for cell proliferation

Nitric oxide (NO) ~ neurotransmitter; cell destruction;

vessel dilation Prostaglandins ~

modified fatty acids secreted by placenta and immune system; also found in semen

Mode of Action: Chemical Signaling 1- Plasma membrane reception

• signal-transduction pathways (neurotransmitters, growth factors, most hormones)

2- Cell nucleus reception • steroid hormones, thyroid hormones, some local regulators

Vertebrate Endocrine System Tropic hormones ~

a hormone that has another endocrine gland as a target

Hypothalamus~pituitary Pituitary gland Pineal gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Gonads (ovary, testis)

The hypothalamus & pituitary, I Releasing and inhibiting hormones Anterior pituitary: Growth (GH)~bones

√gigantism/dwarfism √acromegaly

Prolactin (PRL)~mammary glands; milk production

Follicle-stimulating (FSH) & Luteinizing (LH)~ovaries/testes Thyroid-stimulating (TSH)~ thyroid Adrenocorticotropic (ACTH)~

adrenal cortex Melanocyte-stimulating (MSH)

Endorphins~natural ‘opiates’; brain

pain receptors

The pituitary, II

The posterior pituitary: Oxytocin~

uterine and mammary gland cell contraction

Antidiuretic (ADH)~ retention of water by

kidneys

The pineal, thyroid, & parathyroid Melatonin~ pineal gland;

biological rhythms

Thyroid hormones: Calcitonin~

lowers blood calcium Thyroxine~ metabolic processes

Parathyroid (PTH)~ raises blood calcium

The pancreas

Islets of Langerhans Alpha cells:

•glucagon~ raises blood glucose levels

Beta cells: •insulin~ lowers blood glucose levels

Type I diabetes mellitus (insulin-dependent; autoimmune disorder)

Type II diabetes mellitus (non-insulin-dependent; reduced responsiveness in insulin targets)

The adrenal glands Adrenal medulla (catecholamines): •epinephrine & norepinephrine~

increase basal metabolic rate (blood glucose and pressure)

Adrenal cortex (corticosteroids): •glucocorticoids (cortisol)~ raise

blood glucose •mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+

The gonads Steroid hormones:

precursor is cholesterol

androgens (testosterone)~ sperm formation; male secondary

sex characteristics; gonadotropin estrogens

(estradiol)~uterine lining growth; female secondary sex characteristics; gonadotropin

progestins (progesterone)~uterine lining growth

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Steroid Hormone Action

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