Endocrine System Glands Hormones Regulation Communication Animals rely

Endocrine System Glands & Hormones

Regulation & Communication § Animals rely on 2 systems for regulation u endocrine system § system of ductless glands w secrete chemical signals directly into blood w chemical travels to target tissue w target cells have receptor proteins w slow, long-lasting response u nervous system § system of neurons w transmits “electrical” signal & release neurotransmitters to target tissue w fast, short-lasting response

§ Why are hormones needed? Send chemical messages from one body part to another u Long term communication u Daily homeostasis & regulation u § solute levels in blood w Glucose, Ca++, Na+ § Osmoregulation § Metabolism § Growth § Reproduction § Stress

Regulation by chemical messengers § Neurotransmitters released by neurons § Hormones release by endocrine glands neurotransmitter endocrine gland axon hormone carried by blood receptor proteins target cell

Classes of Hormones

Action of lipid (steroid) hormones steroid hormone target cell S S cytoplasm 1 blood S protein carrier cross cell membrane 2 binds to receptor protein becomes transcription factor 5 S 3 m. RNA read by ribosome plasma membrane DNA nucleus 4 m. RNA 6 protein 7 protein secreted ex: secreted protein = growth factor (hair, bone, muscle, gametes)

signal-transduction pathway Action of protein hormones 1 protein hormone P signal binds to receptor protein plasma membrane activates G-protein activates enzyme c. AMP receptor protein activates cytoplasmic signal cytoplasm target cell GTP ATP acts as 2° messenger transduction activates enzyme 2 secondary messenger system activates enzyme produces an action 3 response

Action of epinephrine (adrenaline) signal adrenal gland 1 epinephrine activates G protein receptor protein in cell membrane activates GTP 3 adenylyl cyclase c. AMP GDP GTP 2 activates ATP 4 activates protein kinase-A transduction 5 activates phosphorylase kinase cytoplasm liver cell released to blood activates glycogen phosphorylase glycogen 6 glucose 7 response

Benefits of a 2° messenger system signal 1 Activated adenylyl cyclase receptor protein 2 Not yet activated amplification 4 3 GTP 6 Amplification! FAST response! c. AMP 5 amplification G protein amplification protein kinase amplification enzyme 7 amplification product

Maintaining homeostasis hormone 1 lowers body condition gland high specific body condition low raises body condition gland hormone 2 Negative Feedback Model

Nervous System Control Negative Feedback Controlling Body Temperature nerve signals hypothalamus sweat dilates surface blood vessels high body temperature (37°C) low hypothalamus constricts surface shiver blood vessels nerve signals

Endocrine System Control Negative Feedback Regulation of Blood Sugar islets of Langerhans beta cells insulin pancreas high liver blood sugar level (90 mg/100 ml) triggers hunger liver releases glucose liver stores reduces glycogen appetite body cells take up sugar from blood low pancreas glucagon islets of Langerhans alpha cells

Endocrine System Control Blood Osmolarity ADH osmoreceptors in hypothalamus increased water reabsorption pituitary high nephron adrenal gland Negative Feedback increase thirst nephron blood osmolarity blood pressure increased water & salt reabsorption low Juxta. Glomerular Apparatus nephron (JGA) renin aldosterone angiotensinogen

Nervous & Endocrine systems linked § Hypothalamus = “master nerve control center” u u u nervous system receives information from nerves around body about internal conditions releasing hormones: regulates release of hormones from pituitary § Pituitary gland = “master gland” u u endocrine system secretes broad range of “tropic” hormones regulating other glands in body hypothalamus posterior pituitary anterior

Tropic hormones = target endocrine glands hypothalamus Kidney tubules e on ho in ct ola rm Muscles of uterus pr (G H) thyroid-stimulating hormone posterior antidiuretic (TSH) pituitary hormone (ADH) Thyroid gland c i anterior p o icotr. H) t r pituitary o oc (ACT n oxy e r ad mone m toc el hor in an oc yt est gonadotropic im ula hormones: tin Adrenal follicleg cortex stimulating hormone (FSH) & luteinizing hormone (LH) gr ow ) RL th (P ho r (M mon SH e ) Melanocyte Bone and muscle Testes Ovaries Mammary glands

Pituitary Dwarfism

Gigantism

Acromegaly

Regulating metabolism § Hypothalamus u TRH = TSH-releasing hormone § Anterior Pituitary u TSH = thyroid stimulating hormone § Thyroid u u produces thyroxine hormones metabolism & development § § § § bone growth mental development metabolic use of energy blood pressure & heart rate muscle tone digestion reproduction tyrosine + iodine thyroxine

Goiter Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine + tyrosine + iodine ✗ ✗ thyroxine

Endocrine System Control Negative Feedback Regulation of Blood Calcium calcitonin thyroid high Ca++ uptake in intestines kidney reabsorption of Ca++ deposited in bones blood calcium level (10 mg/100 m. L) low activated Vitamin D bones release Ca++ kidney reabsorption of Ca++ parathyroid hormone (PTH)

Negative Feedback Female reproductive cycle egg matures & is released (ovulation) estrogen builds up uterus lining corpus luteum ovary progesterone FSH & LH maintains uterus lining pituitary gland fertilized egg (zygote) yes Gn. RH hypothalamus no pregnancy corpus luteum breaks down progesterone drops menstruation h. CG corpus luteum progesterone maintains uterus lining

Oxytocin Positive Feedback

Positive Feedback

Effects of stress on a body Stress Nerve Spinal cord signals (cross section) Hypothalamus Nerve cell adrenal medulla secretes epinephrine & norepinephrine ME DU A LL Releasing hormone Anterior pituitary Blood vessel Nerve cell ACTH Adrenal gland Adrenal cortex secretes mineralocorticoids & glucocorticoids CO Kidney (A) SHORT-TERM STRESS RESPONSE (B) LONG-TERM STRESS RESPONSE RT Effects of glucocorticoids: Effects of epinephrine and norepinephrine: Effects of mineralocorticoids: 1. Glycogen broken down to glucose; increased blood glucose 2. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate 5. Change in blood flow patterns, leading to increased alertness & decreased digestive & kidney activity 1. Proteins & fats broken 1. Retention of down & converted to sodium ions & glucose, leading to water by kidneys increased blood 2. Increased blood glucose volume & blood 2. Immune system pressure suppressed EX