Chapter 13 Hormones & sex - 1 Chapter 13 Hormones...

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The neuroendocrine system Pituitary gland Roles of hormones in creating sex differences Cases of exceptional human sexual development 13.1 The Neuroendocrine system Glands Exocrine glands – release their chemicals into ducts, which carry them to their targets, mostly surface of the body o Sweat glands, for example Endocrine glands – ductless; release hormones directly into circulatory system o Only organs whose primary function is hormone release are referred to as endocrine glands Classes of Hormones Classes of hormones: a) Amino acid derivative hormones – synthesized in simple steps from amino acid molecule (eg. epinephrine released from adrenal medulla & synthesized from tyrosine) b) Peptide (short chain) & protein hormones (long chain) – chains of amino acids; activate second messengers (eg. insulin moves glucose into cells) c) Steroid hormones – synthesized from cholesterol (fat) o o Directly influence gene expression o Sex hormones – released by gonads, activate sex-limited genes to create differential effects Tropic hormones – influence the release of hormones from other glands Major Endocrine Glands Gland Hormones produced Effect of hormone Pineal gland Melatonin Affects reproductive development & daily physiologic cycles Pituitary gland Growth hormone Anti-diuretic hormone Gonadotrophins Controls growth of bones & muscles Increases reabsorption of water in kidney Controls development of Thyroid gland Thyroxine Controls rate of metabolism & rate that glucose is used up in 1
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Adrenal gland Adrenaline Prepares the body for emergencies; increases heart rate & depth of breathing; raises blood sugar level so more glucose if available for respiration, diverts blood from gut to limbs Pancreas Insulin Glucagon Converts excess glucose into glycogen in liver Converts glucagon back into glucose in liver Ovaries Estrogen Progesterone Controls ovulation & secondary sexual characteristics Prepares the uterus lining for receiving am embryo Testes Testesterone Controls sperm production & secondary sexual characteristic Thymus Thymosin Promotes production & maturation of white blood cells Gonads o Male testes produce sperm o Female ovaries produce ova Fertilization o Sperm cell + ovum = zygote o 23 pairs of chromosomes Sex chromosomes (X & Y) – XX=female; XY=male Sex Steroids Two main classes: o Androgens – testosterone most common o Estrogens – estradiol most common
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Chapter 13 Hormones & sex - 1 Chapter 13 Hormones...

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