animal hormones

• Sensor monitors the variable
• control center compares magnitude of variable to the setpoint value, integrates the information, and controls the response of the effector system(s), which control the magnitude of the variable, bringing it back to set point

• nerve cells that produce electrical impulses (that usually transmit information via neurotransmitters)
• hormones that provide chemical signals

they produce and coordinate anatomical, physiological, developmental and behavioral changes

they are secreted by endocrine cells (often in endocrine glands)

• Hormones work much more slowly than nerve impulse transmission and are not useful for controlling rapid actions
• hormones coordinate longer-term developmental processes such as reproductive cycles

cells or glands that do not have ducts leading to the outside of the body; they secrete their products directly into the extracellular fluid

have ducts that release their secretions into the gut, etc.

• No, some endocrine cells are single cells within a tissue
• digestive hormones, for example are secreted by isolated endocrine cells in the wall of the stomach and small intestine

Some endocrine cells aggregate into secretory organs called endocrine glands

In vertebrates, nine major endocrine glands make up the endocrine system

hormone secreting cells

• cells receiving the hormonal messages, they must have appropriate receptors
• the binding of the receptor activates a response

• The distance over which teh signal operates distinguishes hormone groups
• some act close to the release site, others at distant body locations

• most hormones diffuse into the blood, which distributes them throughout the body
• when the hormone message encounters a cell with the proper receptor, it binds and triggers a response

It can tell you if it is water or lipid soluble and if it can diffuse across the cell membrane

• act locally
• two types: autocrine, paracrine

act on the secreting cell itself

• stimulate growth and differentiation of cells, are a major class fo paracrine hormones
• also act as autocrine hormones: some of the hormone influences the cell that secreted it, preventing the cell from secreting too much hormone

• growth factors
• neurons may also be considered to be paracrine cells because they use chemicals called neurotransmitters to send messages to another cell

• act on cells near the site of release
• released in tiny amounts or inactivated rapidly by enzymes, or are taken up efficiently by local cells
• they never get into the circulatory system

• peptides or protiens
• steroid hormones
• amine hormones

• water soluble
• transported by vesicles out of the cell that made them
• their receptors are on the outside of the cell membrane of the target cell (they can't get into the cells)

• lipid-soluble
• can diffuse out of the cells that made them
• in the blood they must be bound to carrier proteins
• bc they can diffuse through the cell membrane their receptors are usually in the cytoplasm of the target cells

• derivatives of the amino acid tyrosine
• most are water-soluble, but some are lipid-soluble

• the receptors for lipid-soluble hormones are inside cells, either in the cytoplasm or in the nucleus
• the action of lipid-soluble hormones is mediated by intracellular hormone receptors that usually alter gene expression

large glycoproteins on the cell surface with three domains

• binding domain: projecting outside the plasma membrane
• transmembrane domain: anchors the receptor in the membrane
• cytoplasmic domain: extends into the cytoplasm of the cell

It activates protein kinases or protein phosphotases (signal transduction cascades)

• responses to hormones depend on their receptors and target cells
• the same hormone can cause different responses in different types of cells

• in the heart, it stimulates faster (increases HR) and stronger (increases stroke volume) heartbeat (increase cardiac output)
• blood vessels in some areas (gut, skin, etc.) constrict to send more blood to skeletal muscles
• in the liver, glycogen is broken down to glucose to provide quick energy
• in fat tissues, fats are mobilized as another energy source, fatty acids

• hormonal comunication arose early in evolution
• all multicellular animals have chemical communication between cells, even sponges
• plants also have hormones, mainly to control growty and development

because insects have rigid exoskeletons, they have episodic growth patterns and must molt periodically

the growth stage between each molt

two hormones, brain hormone and ecdysone (molting hormone) work together to regulate molting

pair of structures attached to the insect brain that store brain hormone

endocrine gland in the thorax of insects which receives brain hormone and releases ecdysone which stimulates molting

• the rear part of the insect head
• produces juvenile hormone

• prevents molting to the adult stage
• if it is present the insect molts into another juvenile instar

larva-->pupa-->adult

• a link between the nervous system and many endocrine glands and plays a crucial role in the endocrine system
• the pituitary gland sits in a depression at the bottom of the skull and is attached to the hypothalamus
• made of two parts: anterior and posterior

• an extension of the hypothalamus and therefor neural tissue
• releases 2 hormones: ADH, oxytocin

• they are made by neurons in the hypothalamus (and therefore are neurohormones) an are packaged in vesicles
• the vesicles are transported down the axons of the neurons that made them and are stored in the posterior pituitary
• this movement of vesicles is achieved by kinesin proteins, powered by ATP, that "walk" down the microtubules of the axon

• forms from an inpocketing of the roof of the mouth (Rathke's pouch)
• releases four tropic hormones which control (stimulate) activities of other endocrine glands
• they are peptide and protein hormones
• each is produced by a different type of pituitary cell
• other peptide and protein anterior pituitary hormones influence tissues that are not endocrine glands

• the major function is to increase water conservation by the kidney
• If there is a high level of ADH secretion, the kidneys reabsorb water, decreasing urine output
• ADH stimulates increased aquaporins in the collecting ducts
• if there is a low level of ADH secretion, the kidneys release water in dilute, high volume urine
• ADH release by the posterior pituitary increases if blood pressure falls or blood becomes too salty
• ADH also causes peripheral blood vessel constriction

• a major function of oxytocin is to stimulate uterine smooth muscle contraction for the birth process (Pitocin)
• it also stimulates milk flow (stimulates smooth muscle for ejection of milk) in the mother's breasts

• thyrotropin
• adrenocorticotropin
• gonadotropins
• lutenizing hormone and follicle stimulating hormone

• growth hormone
• prolactin
• melanocyte-stimulating hormone
• endogenous opiodes endorphines and enkephalins

• acts on many tissues to promote growth
• stimulates cells to take up amino acids
• stimulates the liver to produce chemical messages (insulin-like growth factors) that stimulate bone and cartilage growth

the result of overproduction of GH in children

• caused by the underproduction of GH
• GH can now be produced by genetically engineered bacteria

• stimulates the production and, to a lesser extent, secretion of milk in female mammals
• it is also important in pregnancy and, in males, has a role in controlling the endocrine functions of the testes

• the body's natural opiates
• in the brain, these molecules act as neurotransmitters to reduce pain in pain pathways

• the anterior pituitary is controlled by neurohormones from the hypothalamus
• the hypothalamus obtains data about body conditions and the external environment through both neuronal and hormonal signals
• the hypothalamus and the anterior pituitary are connected by portal blood vessels
• secretions from the hypothalamic nerves are transported by these blood vessels to the anterior pituitary

• from the hypothalamus
• cuases anterior pituitary cells to release thyrotropin, which in turn stimulates the thyroid gland

causes the anterior pituitary to release tropic hormones that control gonad activity (follicle stimulating hormone and luteinizing hormone)

They are under negative feedback control by the hormones of the glands they stimulate

• cortisol is produced by the adrenal gland in response to adrenocorticotropin. It returns to the pituitary in the blood, and inhibits further release of adrenocorticotropin
• Cortisol also exerts negative feedback control on the hypothalamu, inhibiting release of adrenocorticotropin-releasing hormone
• however, higher brain input to the hypothalamus also controls circulating anterior pituitary hormone levels

• located near the trachea
• another example of an endochrine
• produces the hormone thyroxine in specialized structures called follicles

• two active forms T3 and T4 are made from tyrosine
• T3: 3 I
• T4: 4 I
• more T4 is produced, but its can be converted to T3 by an enzyme in the blood
• T3 is the more active form of the hormone

• it stimulates the transcription of many genes in nearly all cells in the body. Theses include genes for enzymes of energy pathways, transport proteins, and structural proteins
• it elevates metabolic rates in most cells and tissues (important in thermoregualtion)
• it raises blood glucose and promotes the use of carbohydrates over fats for fuel

Irreversible neural damage and retardation caused by insufficient thyroxine after the 4th month of human fetal life which results in inadequate formation of the myelin sheath around the axons of neurons

• Thyrotropin (or TSH) from the anterior pituitary activates thyroid gland cells to produce thyroxine
• Thyrotropin-releasing hormone (TRH) from the hypothalamus activates TSH-producing cells in the anterior pituitary
• In a negative feedback loop, thyroxine inhibits the response of pituitary cells to TRH. Therefore, less TSH is released when levels are high, and more is released when levels are low
• Thyroxin also feeds back to reduce TRH from the hypothalamus

an enlarged thyroid gland associated with eigher very low (hypothyroidism) or very high (hyperthyroidism) levels of thyroxine

a thyroid follicle is a layer of epithelial cells surrounding a mass of glycoprotein called thyroglobulin

contains iodinated tyrosines and is digested by the epithelial cells of the follicle to make thyroxine

• the released molecules will be neither T3 nor T4 and will not bind to appropriate receptors (including those in the hypothalamus and anterior pituitary)
• Goiter occurs when thyroglobulin production is above normal and the follicles are enlarged

• results when there is insufficient thyroxine to turn off TSH production
• the most common cause is a deficiency of dietary iodine
• with high TSH levels, the thyroid gland continues to produce nonfunctional thyroxine and becomes very large
• the body symptoms of this condition are low metabolic rate, cold intolerance, and physical and mental sluggishness

• results when the negative feedback mechanism fails even though blood levels of thyroxine are hight.
• A common cause is an autoimmune disease in which an antibody to the TSH receptor is produced.
• Common symptom is high metabolic rate.

calcitonin, parathyroid hormone and vitamine D

• Deposition and absorption of bone
• exceretion of calcium by hte kidneys
• Absorption of calcium from the digestive tract

• released by the thryroid gland acts to lower calcium levels in the blood
• Calcitonin decreases osteoclast activity and stimulates the osteoblasts to take up calcium from the blood for bone growth

• Osteoclasts break down bone and release calcium to the blood
• Osteoblasts secrete the protein matrix and use circulating calcium to build new bone. As bone is laid down the osteoblasts are surrounded and develop into osteocytes.

• embedded in the posterior surface of the thyroid glad
• releases parathyroid hormone when blood Ca is low

• causes the osteoclases to dissolve bone and release calcium
• promotes calcium resorption by the kidney to prevent loss in the urine
• promoting vitamin D activation which stimulates the gut to absorb calcium from food
• Acts on the kidneys to increase the elimination of phosphate to reduce the possibility of calcium phosphate salt precipitation (kidney stones)

• not actually a vitamin, produced by the body
• activates to form (1,25) dihydroxyvitamin D, stimulated by PTH
• The active form binds to cyctoplasmic receptors and forms transcription factors. in the digestive tract the transcription factors act to increase synthesis fo calcium pumps, calcium channels and calcium binding proteins, promoting uptake of calcium
• In the kidneys and bone acts like PTH
• Negative feedback to inhibit PTH

bone stored in egg laying female birds to store calcium , under the control of PTH

insulin and glucagon are produced in the pancrease in cell clusters called islets of Langerhans

• required for glucose uptake by most cells but not nerve cells
• inhibits lipase (lipid breakdown) in adipose tissue, and stimualtes amino acid uptake by cells

• type 1 - lack of the protein hormone insulin
• type 2 - lack of insulin receptors on target cells
• causes excessive urine production

hyposecreation of ADH (makes you pee more)

stimulates liver to convert glycogen to glucose when glucose levels are low

• paracrine functions that inhibit both insulin and glucagon
• slows the gut activites
• inhibits release of GH and thyrotropin

made up of adrenal medulla and the adrenal cortex two seperate endocrine organs

• produces epinephrine and norepinephrine
• developes from the nervous system and is under the control of the nervous system

under hormonal control mainly by adrenocorticotropin (ACTH) from the anterior pituitary

• prevent epi from binding to the beta-adrenergic recptors on target cells
• used to reduce fight-or-flight response for heart patients
• leaves alpha sites open for regulatory function

• prodcues by the adrenal cortex using cholesterol
• acts by stimulating transcription of certain genes
• glucocorticoids
• mineralocorticoids
• SEX steroids

raise blood glucose concentrations and other aspects of fuel molecule metabolism

infulence extracellular ionic (mainly Na and K) balance

stimualte SEXUAL developement and reproductive activity. Under normal conditions theses are secreated in only minimal amounts by the adrenal cortex

• the main mineralocoritcoid stimulates the kidney to conserve sodium and excrete potassium
• release is stimulated by angiotensin-II

release is stimulated by lo blood Na and or lo blood pressure

• the main glucocorticoid helps control blood levels of glucose and other energery sources and to mediate the body's response to stress
• raises blood glucose by stimulating gluconeogenesis by the liver and inhibiting peripheral use of glucose (saving for neural tissue) mobilizes fatty acids from adipose tissue and increases blood (amino acid) from muscle for uptake and use in gluconeogenesis
• stress response ensures that muscles have enough glucose for immediate response and brain has enough glucose to function
• also blocks the immune system reactions which temporarily are less critical, can be used to reduce inflammation and allergy

from the hypothalamus to stimulate the release of ACTH which controls cortisol levels

stimulates secretion of HCl and pepsin, increases motility of stomach

slows the movement of the stomach

releases bicarbonate solution from pancrease to neutralize HCl before it enters the intestines

controls the SEX steroids released by the anterior pituitary

released by the hypothamalus to stimulate the release of gonadotropins (LH and FSH)

Starts when the hypothalamus becomes less sensitive to negative feedback by the SEX steroids

remaining follices left over in the ovary during ovulation that function as an endocrine gland and produces estrogen and progesterone for about two weeks

the state of sexual receptivity around the time of ovulation

• similar to funcion in LH but only produced by cells covering the blastocyst
• detected by pregnancy tests

produced by the pineal gland, released in dark