The Endocrine System Chapter 45 All animals exhibit

The Endocrine System Chapter 45

All animals exhibit internal communication and control via 2 major systems Nervous System: high speed electrical messages Endocrine System: slower acting chemical messages

Chemical Signals include: Pheromones send info. between: individuals Local Regulators send info. between: cells in the immediate vicinity Hormones send info. between body organs to regulate: reproduction, energy metabolism, growth & development

Pheromone Information: Communication signals between animals of the same species. Classified by function, for example: mate attractants, territorial markers, alarm substances… Small molecules that are: active in tiny amounts

Local Regulator Information: Neurotransmitters: signals sent out from , called signaling. neurons synaptic Histamine & interleukins: signals sent out from paracrine , called system signaling. immune Growth Factors: proteins which must be present in extracellular fluid for cell types to grow & develop Prostaglandins: modified fatty acids, often from plasma membrane (>16 types), functions include inducing labor, fever, inflammation… Nitrous Oxide (gas): highly reactive, causes rapid change in target cells

Hormone Information: There are 2 kinds of glands in animals: exocrine and endocrine. Some organs contain BOTH types of glands. Exocrine Glands: use ducts for secretion. Ex. Sweat, mucus (NOT part of the endocrine system!) Endocrine Glands: make hormones but are -ductless, use bloodstream for transport Endocrinology: study of hormones (>50)

Hormones are grouped by similarity in chemical structure into 3 classes: Steroid hormones = fat-soluble, made from cholesterol, includes sex hormones Amines = small, water-soluble, often made from tyrosine, includes epinephrine (adrenaline). Polypeptide hormones = most diverse group, chains of amino acids, includes insulin

Hormones are secreted into the ________ Interstitial fluid travel through the bloodstream and are only able to affect their target cells

How Hormones affect cells: Act in very low concentration (tiny amounts) Have different effects on different target cells due to: different receptors or response pathways Cellular Response Pathways = the complex series of steps that occur between hormone-receptor binding and the actual target cell response. Two types: Steroid Hormones: enter target cell and affect gene expression Peptide & A. A. derived Hormones: attach to receptors on target cell surface. Influence the activity of enzymes within cell via second messengers.

Pathway for Water-soluble Hormones • Reception: Hormone binds to receptor on target cell surface. • Transduction: Message travels within cell via second messengers. • Response: activation of an _ enzyme __, change in the _ uptake or secretion ___ of certain molecules, or rearrangement of the cytoskeleton

Second Messengers: Cyclic AMP: (Earl W. Sutherland) Steps in the pathway (enzyme cascade): Hormone binds to the target cell: membrane G protein in membrane binds GTP and converts it to GDP: releasing energy Energy is used by an enzyme adenylate cyclase to convert ATP to c. AMP relays the message to the cytoplasm, activating other enzymes and causing metabolic changes in the cell c. AMP is converted to: an inactive product.

Inositol Triphosphate: (IP 3) • Hormone binds to the target cell membrane • G protein in membrane activates the enzyme phospholipase • Enzyme cleaves a membrane phospholipid into IP 3 and DAG (2 nd messengers).

• IP 3 Second messenger causes the release of Ca+ from the endoplasmic reticulum • Many chemical messengers (neurotransmitters, growth factors, some hormones) stimulate responses in their target cells by: increasing the Ca+ ion concentration in the cytoplasm

Pathway for Lipid-soluble Hormones Reception: Hormone binds to the target cell receptor within the cytosol Transduction: the hormone-receptor complex moves into the nucleus and interacts with DNA or a DNA-binding protein Response: usually is a change in gene expression

Invertebrate Hormones: Functions include: homeostasis, reproduction, development, behavior The same hormone may: function differently in different species

Arthropods are well-researched. Example: Insects Brain Hormones (such as PTTH): Stimulate endocrine glands to produce ecdysteroid Ecdysteroid: triggers molting & metamorphosis

Vertebrate Endocrine System: See Table 45. 1 on p. 949 (green Table 45. 1 on p. 961)! Usually, multiple hormones interact to: coordinate activities Endocrine and nervous systems interact to control each other: many feedback mechanisms Hormones vary in their range of targets: Sex hormones = general Other hormones = more specific Tropic hormones = target other endocrine glands

Regulation of Hormone Secretion: Feedback Regulation: can be positive or negative Negative-feedback pathways may occur in ___ antagonistic pairs ___ Glucose homeostasis example: • Glucagon (from alpha cells of pancreas) targets mainly liver cells to – increase glucose levels in blood • Insulin (from beta cells of pancreas) targets nearly all body cells to – decrease glucose levels in blood via cellular uptake.

See Human Endocrine Glands: Figure 45. 6, p. 950

HYPOTHALAMUS: Region of lower brain • Coordinates endocrine and nervous systems. • Receives signals from nerves throughout the body (including the brain) and initiates endocrine signaling in response.

Neurosecretory cells: receive nerve cell signals and release hormones in response Signals from the hypothalamus travel to the: pituitary gland

PITUITARY GLAND: At the base of the hypothalamus, has 2 lobes Posterior lobe: Extension of the hypothalamus, stores / secretes hormones produced by hypothalamus: Oxytocin: stimulates uterine contractions, lactation, and maternal behaviors ADH (antidiuretic hormone): promotes water re-absorption by: kidneys

Anterior lobe: Controlled by hormones of the hypothalamus Controlling hormones are either releasing or inhibiting (some anterior hormones are controlled by both)

Makes 4 tropic hormones – stimulate other endocrine glands TSH (thyroid stimulating hormone) ACTH (adrenocorticotropin): controls adrenal cortex (kidney) FSH (follicle stimulating hormone): control gonads LH (luteinizing hormone): control gonads

One hormone with some tropic behavior: GH (growth hormone): promotes growth directly liver and stimulates ______to produce somatomedins which stimulate cartilage and bone growth Two Nontropic hormones: • PRL (prolactin): diverse effects in different vertebrates – stimulates milk production & secretion • MSH (melanocyte-stimulating hormone): diverse effects in different vertebrates – mammals = inhibits hunger, others = coloration

THYROID: 2 lobes, ventral tracheal surface, activity is controlled by the hypothalamus and pituitary in a negative feedback loop. Important for vertebrate developmentand metabolism Triiodothyronine (T 3) & Thyroxine (T 4): control development & metabolism Both made with iodine. Deficiency = goiter Calcitonin: lowers Calcium levels in blood (homeostasis)

Hyperthyroidism = Grave’s_____ disease Hypothyroidism (treat with T 4) = lethargy, weight gain, cold intolerance

PARATHYROID: 4 GLANDS, embedded in thyroid Important for calcium ion homeostasis. PTH (parathyroid hormone): raises blood levels of Ca 2+ (opposite of calcitonin) • Needs vitamin D to work.

PANCREAS: Mostly exocrine (digestive secretions) Islets of Langerhans = clusters of endocrine cells (α and β cells)

ADRENAL GLANDS: Apex of kidneys. In mammals, Each one really = two gland types: Adrenal cortex (outer region): Responds to ACTH from pituitary. Secretes corticosteroids, 2 main types: Glucocorticoids: promote glucose synthesis from non-carbohydrate sources Mineralocorticoids regulate water & salt balance Also secretes small amounts of sex hormones (steroids)

Adrenal medulla (inner region): Stimulated by Nervous System, Makes catecholamines from tyrosine – Epinephrine (adrenaline) and Norepinephrine: Allow for “flight or fight” response BOTH Increase the amount of: chemical energy available for immediate use • Promote glucose release from liver, glycogen breakdown, and fatty acid release from fat cells

Affect cardiovascular and respiratory systems: Increase heart rate, stroke volume, oxygen delivery Epinephrine mainly controls heart and metabolic rates Norepinephrine mainly controls blood pressure

GONADS: testes & ovaries Affect growth & development, regulate reproductive cycles and behaviors. All types are found in BOTH males and females, but in different proportions. Androgens: Responsible for male reproductive system (development & maintenance) Ex. = testosterone Estrogens: Responsible for female reproductive system (development & maintenance) Ex. = estradiol Progestins: Responsible for uterus maintenance Ex. = progesterone

Pineal Gland: small mass of tissue near the Center of the brain – Primary source of melatonin – nighttime release is regulated by day length, involves biological clocks

Human Female Reproductive Cycle: STUDY Figure 46. 13, p. 976 (green Figure 46. 15, p. 988) Be sure you understand length of cycle & hormonal control of events!