Chapter 45: Hormones & The Endocrine System

Anterior pituitary

- Follicle stimulating hormone (FSH) and luteinizing hormones (LH): stiulates ovaries and testes -Thyroid-stimulating hormones (THS): stimulates thyroid gland -Adrenocrtoicotropic hormone (ACTH): stimulates adrenal cortex - prolactin: stimulates mammary gland cells - Growth hormone (GH): Stimulates growth and metabolic functions A tropic hormone regulates the function of endocrine cells and glands

Posterior pituitary

- Oxytocin: stimulate contraction of smooth muscle cells in uterus and mammary glands - Vasoprressin: (also called anti-diuretic hormone, ADH): promotes retention of water by kidneys; influences social behavior and bonding

Coordinate of endocrine and nervous systems: Vertebrates

- The hypothalamus receives info from the NS and initiates responses through the endocrine system Attached to the hypothalamus is the pituitary gland The posterior pituitary stores and secretes hormones that are made in the hypothalamus The anterior pituitary makes and releases hormones under regulation of the hypothalamus

Adrenal medulla

- secretes epinephrine and norepinephrine: rise blood glucose levels: increase metabolic activities; constrict certain blood vessels.

Multiple Effects of Hormones

-The same hormone may have different effects on target cells that have: 1. Different receptors for the hormone 2. Different signal transduction pathways or effector proteins A hormone can also have different effects effects in different species

Chemical classes of hormones

1. Polypeptides 2. Steroid hormones 3. Amines (amino acids) The solubility of a hormone correlates with the location of receptors inside or on the surface if target cells Lipid-soluble hormones (except thyroid hormones) pass easily through cell membranes, while water-soluble hormones do not

Hypothalamus

A neural structure lying below the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and reward. brain region controlling the pituitary gland

Pancreas

An organs in the abdominal cavity with two roles. The first is an exocrine role: to produce digestive enzymes and bicarbonate, which are delivered to the small intestine via the pancreatic duct. The second is an endocrine role: to secrete insulin and glucagon into the bloodstream to help regulate blood glucose levels. -Insulin: lowers blood glucose levels -Glucagon: raises blood glucose levels

The body's long-distance regulators

Animal hormones are chemical signals that are secreted into extracellular fluids, gain entry into the circulatory system and communicate regulatory messages within the body Hormones reach all parts of the body, but target cells are equipped to respond Insect metamorphosis and molting are regulated by hormones

Pathway for Water-Soluble Hormones

Binding of a hormone to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm, enzyme activation, or a change in gene expression ex: Epinephrine, also called adrenaline,hormone that is secreted mainly by the medulla of the adrenal glands and that functions primarily to increase cardiac output and to raise glucose levels in the blood. Epinephrine typically is released during acute stress, and its stimulatory effects fortify and prepare an individual for either "fight or flight"

Ovaries

Glands that produce the egg cells and hormones -Estrogen: stimulates uterine lining growth; promote development and maintenance of female secondary sex characteristics -Progestins: promotes uterine lining growth

Coordination of Endocrine and Nervous Systems: Anterior Pituitary Gland

Hormone production in the anterior pituitary is controlled by releasing and inhibiting hormones from the hypothalamus. Ex: Prolactin-releasing hormone from the hypothalamus stimulates the release of prolactin from the anterior pituitary gland. Prolactin stimulates milk production.

Hormones and other signaling molecules

Hormones and other signaling molecules bind to target receptors, triggering specific response pathways Hormones are one of several types of secreted chemicals that transmit information. *Type of secreted molecules:* Hormones Local regulators Neurotransmitters Neurohormones Pheromones

Cellular response pathway

In addition to receptors location, water-soluble and lipid-soluble hormones also exhibit additional differences in their response pathways *Watere-soluble hormones* are secreted by exocytosis, travel freely in the bloodstream and bind to extracellular (cell-surface) receptor *Lipid-soluble hormones* diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and bind to intracellulr receptors

Endocrine signaling

In endocrine signaling, hormones are secreted into extracellular fluids and travel over long distances via the bloodstream. Some endocrine system cells are part of other organ systems Other endocrine cells are *grouped into glands (endocrine glands)* that are ductless and secrete hormones directly into surrounding fluid Hormones maintain homeostasis, mediate responses to environmental stimuli and regulate growth, development, and reproduction *Exocrine glands* have ducts and secrete substances onto surfaces or into body cavities (ex: tear ducts, salivary glands)

Neurosecretory cells

Neurons of the hypothalamus that secrete neurohormone rather than neurotransmitter

Endocrine tissues and organs

Pineal gland, hypothalamus, pituitary gland (anterior and posterior), thyroid gland, parathyroid glands, adrenal glands )medulla and cortex), pancreas, ovaries, testes

Feedback regulation and coordination with the nervous system are common in endocrine signaling

Simple hormone pathways

Feedback regulation and coordination with the nervous system are common in endocrine signaling

Simple neuroendocrine pathway

Thyroid hormone and disorders

TH functions primarily to increase metabolic rate, is important for normal development, and performs many other functions. TH exists as two hormones (T3 and T4) and require iodine. Hypothyroidism: weight gain, lethargy, cold intolerance Hyperthyroidism: high body temperature, profuse sweating, weight loss, high blood pressure Grave's disease is an autoimmune disease in which antibody bind to and activate the TH receptor, resulting in sustained TH production. Low iodine levels can also result in overproduction of TH, because the usual negative feedback by TH does not occur. This may also lead to an enlarged thyroid gland (goiter).

Anti-mullerian hormone (AMH)

a hormone secreted by the testes that prevents the development of the female reproductive tract AMH is activated by SOX9 in the Sertoli cells of the male fetus.[8]Its expression inhibits the development of the female reproductive tract, or Müllerian ducts (paramesonephric ducts), in the male embryo, thereby arresting the development of fallopian tubes, uterus, and upper vagina

Synaptic signaling

a nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell Through synaptic signaling, neurons secrete molecules called neurotransmitters that diffuse short distance to bind receptors on target cells

Adrenal glands

a pair of endocrine glands that sit just above the kidneys and secrete hormones (epinephrine and norepinephrine) that help arouse the body in times of stress.

Local regulators

chemical signals that travel over short distances by diffusion to reach their target cells Local regulators function in many processes including blood pressure regulation, NS function and reproduction

Thyroid gland

endocrine gland that surrounds the trachea in the neck produces hormones that regulate metabolism, body heat, and bone growth - Thyroid hormone (T3 and T4): stimulates and maintains metabolic processes -Calcitonin: lowers blood calcium level

Estradiol

estrogen secreted by the ovaries

Mineralcorticoids (aldosterone)

hormone produced in adrenal cortex that stimulates the kidneys to stimulate reabsorbtion of sodium and excretion of potassium Also involved in mineral metabolism LONG TERM STRESS RESPONSE

Adrenal Hormones: Response to Stress

The adrenal glands rest on top of the kidneys, and are divided into a cortex and a medulla. The adrenal medulla contains secretory cells developed from neural tissue, and release catecholamines. Catecholamines participate in short-term stress. Catecholamines Epinephrine and norepinephrine are derived from the amino acid tyrosine. Both are involved in the "fight-or-flight" response. The adrenal cortex consists of endocrine cells that release corticosteroids in response to stimuli from the hypothalamus (via corticotropin-releasing hormone) and the anterior pituitary gland (via ACTH). Corticosteroids participate in long-term stress. Corticosteroids Glucocorticoids (eg, cortisol) function to increase glucose synthesis and metabolism, and also have anti-inflammatory effects. Mineralocorticoids (eg, aldosterone) are involved in mineral metabolism.

Pituitary gland

The endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands.

Growth Hormone

hormone secreted by anterior pituitary gland that stimulates growth of bones Promotes growth by stimulating the release of insulin like growth factors (IgF) from the liver. These, in turn, stimulate bone and cartilage growth Hyposecretion of growth hormone: -Retards long-bone growth -May lead to pituitary dwarfism -Routinely treated with recombinant HGH Hypersecretetion of growth hormone: -Stimulates bone growth -May lead to gigantism -Overgrowth of extremities causes acromegaly (overgrowth of hands, feet, face etc)

Intercellular communication

interactions between cells using chemical signals -Endocrine signaling - Paracrine and autocrine signalling - Local regulators

Hormone cascade pathways

involve the hypothalamus, anterior pituitary and a target endocrine gland. Signals to the brain stimulate the hypothalamus to secrete a hormone that stimulates or inhibits release of an anterior pituitary hormone. This hormone, in turn, acts on another endocrine organ, stimulating the secretion of yet another hormone.

Chemical signals

molecules secreted by cells into the extracellular fluid

Synaptic and neuroendocrine signaling

network of neurons transmit chemical signals (neurotransmitters) to other cells across synapses

Adrenal cortex

outer section of each adrenal gland, secretes; - Glucocorticoids: raises blood glucose levl - Mineralocorticoids: promote re-absorption of Na+ and excretion of K+ in kidneys

Biological rhythms

periodic physiological fluctuations in the body, such as the rise and fall of hormones and accelerated and decelerated cycles of brain activity, that can influence behavior Metatonin is released by the pineal gland, which is located near the center of the brain Neurons from the suprachiasmatic nucleus of the hypothalamus control the release of metatonin. SCN acts as a biological clock by receiving input from light-sensitive neurons of the retina Melatonins effects: -skin pigmentation -sleep

Neurohormones

produced and released by neurons in the brain, rather than by the endocrine glands, and delivered to organs and tissues through the bloodstream A class of hormones that originate from neurosensory cells in the brain that secrete molecules that diffuse into the blood stream (long distance). This is called neuroendocrine signaling Ex: ADH (Vasopressin)

Estrogens (estradiol)

promote the development of female reproductive structures ad secondary sexual characteristics

Androgens (testosterone)

promote the development of male productive structures and secondary sexual characteristics

Progestins (progesterone)

promotes endometrial growth to prepare the uterus for pregnancy prepare and maintain tissues of the uterus to support an embryo

Three Key Events of Signaling

reception, signal transduction, response

paracrine and autocrine signaling

secrete molecules, "local regulators," that act over short distances, reach target cells by diffusion

Autocrine signaling

secreted molecules diffuse locally and trigger a response in the cells that secrete them Secreted molecule act on the secreting cell itself

Pineal gland

secretes melatonin, which participates in regulation of biological rhythms

Parathyroid glands

small pea-like organs that regulate calcium and phosphate balance in blood, bones, and other tissues. Located on the posterior of the thyroid gland - Parathyroid hormone (PHT): raises blood calcium level

Neuroendocrine signaling

specialized neurosecretory cells secrete molecules called neurohormones that travel to target cells via the bloodstream

Gonadrotropin-releasing hormone (GnRH)

stimulates release of FSH and LH (gonadotropins) GnRH from the hypothalamus stimulates the release of gonadotropins (FSH and LH) from the anterior pituitary gland. FHS and LH, in turn, controls the synthesis of the sex hormones

Sex hormones

The gonads produce androgens, estrogens and progestins in both males and females, but in different proportions. hormones that regulate the development and functioning of reproductive organs and that stimulate the development of male and female sexual characteristics Sex hormones determine gonadal fate

Testes

The male gonads, which produce sperm and secrete male sex hormones. -Androgens: support sperm formation; promote development and maintenance of male secondary sex characteristics

Endocrine system

the body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream Secretes hormones that coordinate slower but longer acting responses including reproduction development, energy metabolism, growth and behavior

Nervous system

the body's speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous systems Conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells

Pheromones

Chemical signals released by an animal that communicate information and affect the behavior of other animals of the same species. Chemical signals that are released into the external environment with he purpose of communicating with other animals of the same species Serve many functions including marking trails leading to food sources, warning of predators, and attracting potential mates Ex: Asian army ants use their antennae to follow a pheromone marked trail

What two systems coordinate communication throughout the body?

Endocrine system Nervous system

Chemical classes of local regulators

Examples include: - prostaglandins (modified fatty acids) - cytokines (eg, interlukins, interferins) - growth factor (eg, EGF, VEGF) -nitric oxide

Parathyroid hormone and vitamin D: Control of blood calcium

The parathyroid glands are a set of 4 small structures hidden in the posterior surface of the thyroid gland A decrease in Ca2+ levls stimulates release of PTH, which acts on bone and kidneys and activates vitamin D An increase in Ca2+ levels promotes release of calcitonin from the thyroid gland. Calcitonin inhibits bone braekdown and enhances Ca2+ excretion by the kidneys POSTERIOR

Pathway of lipid soluble hormones

The response to a lipid-soluble hormone is usually a change in gene expression. Steroids, thyroid hormones, and hormonal form of vitamin D target cells and bind to protein receptors in the cytoplasm or nucleus Protein-receptor complexes then act as regulatory transcription factors in the nucleus, regulating transcription of specific genes Ex: Estradiol

Synapses

tiny gaps between dendrites and axons of different neurons Neurons contact target cells (other neuron or muscles at specialized junctions called synapses

Exocytosis and endocytosis

transport large molecules across membranes

Hormones

chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues

Neurotransmitters

chemical messengers that cross the synaptic gaps between neurons Play a role in sensation, memory, cognition, and movement

Coordinate of endocrine and nervous systems: Invertebrates

Invertebrates -Development of endocrine nervous system PTTH: prothoracicotropic H JH: juvenile H ECDYSIS: SHEDDING OF EXOSKELETON Corpora cardiaca are a pair of neuroglandular bodies that are found behind the brain and on either sides of the aorta. These not only produce their own neurohormones but they store and release other neurohormones including PTTH prothoracicotropic hormone (brain hormone), which stimulates the secretory activity of the prothoracic glands, playing an integral role in moulting. In insect physiology, the corpus allatum (plural: corpora allata) is an endocrine gland which generates juvenile hormone The prothoracic glands are either of a pair of endocrine glands located in the prothorax of certain insects that regulate molting. They have an ectodermal origin and secrete ecdysteroids, such as ecdysone and 20-hydroxyecdysone.

Catecholamines (epinephrine and norepinephrine)

Secreted by the Adrenal Medulla Regulated by: CNS ↑BG, ↓metabolic activity, ↑HR, vasoconstriction flight or fight response Targets: muscles, heart, lungs, eyes Epinephrine and norepinephrine are derived from the amino acid tyrosine. Both are involved in the "fight-or-flight" response. SHORT STRESS RESPONSE

Epinephrine (adrenaline)

Secreted by the adrenal medulla; increases heart rate and blood pressure and dilates airways. t is part of the body's "fight or flight" reaction.

Paracrine signaling

Signal released from a cell has an effect on neighboring cells. Secreted molecules act on neighboring cells

Gonadotropins

anterior pituitary tropic hormones, follicles stimulating hormone (FSH) and luteinizing hormone (LH) which stimulate the gonads (ovaries and testes) to produce gametes and to secrete sex steroids Gonadotropins are hormones synthesized and released by the anterior pituitary, which act on the gonads (testes and ovaries) to increase the production of sex hormones and stimulate production of either sperm or ova

Corticosteroids

anti-inflammatory agents that treat skin inflammation A group of hormones, including cortisol, released by the adrenal cortex at times of stress Glucocorticoids (eg, cortisol) function to increase glucose synthesis and metabolism, and also have anti-inflammatory effects LONG TERM STRESS RESPONSE

Pathway or water-soluble hormones

binding a hormone to its receptor initiates a signal transduction pathway leading to: responses in the cytoplasm, enzyme activate, or change in gene expression A signal transduction pathway is a serious of steps by which signal on a cell's surface is converted into a specific cellular response Signaling by hormones involves 3 key events: 1. reception 2. signal transduction 3. response