Anatomy and Physiology Chapter 10 Notes Secretion = the controlled release of chemicals from a cell. Classes of Chemical Messengers

1. Autocrine chemical messengers – chemical messengers stimulate the cells that originally secreted it or the same kind of cell – (auto = same)

2. Paracrine chemical messengers – chemical messengers are secreted into extracellular

fluid but only has a localized effect on nearby other tissues

3. Neurotransmitter – chemical messengers are produced by neurons and secreted into the synaptic cleft and influences postsynaptic cells.

4. Endocrine – chemical messengers are secreted into the blood by special cells and travel through the blood to distant target tissue.

Functions of the Endocrine system

1. Metabolism - Regulates the rate of metabolism 2. Digestion - regulates the level of satiety (feeling of fullness) and breakdown of food. 3. Tissue - regulation of tissue development 4. Ions - regulation of the ion solute concentration of the blood 5. Water – regulates water balance by controlling the solutes in the blood 6. Heart Rate and blood pressure – regulates heart rate and blood pressure for all different

levels of physical activity 7. Blood glucose/nutrients – regulates the levels of blood glucose and other nutrients in

the blood 8. Reproduction – controls the development and functions of the reproductive system 9. Uterine Contractions/Breast milk – regulates the uterine contractions during delivery of

a baby, stimulates milk release from the breast of lactating (milk producing) females 10. Immune System – endocrine system helps control the production and function of

immune cells Endocrine system – endocrine glands and specialized endocrine cells located in other organs. Hormones – chemical messengers secreted by endocrine glands and cells, these chemicals are always secreted into blood and never into a duct. (duct would be EXOcrine) Target tissues – “effectors” – tissue in which a hormone produces a response

Two major types of hormones based on chemical nature 1. Lipid-soluble hormones

small hormones that do not dissolve in fat bilayer must be carried through the blood by a protein can last as few as a few days and as long as a few weeks. Steroids Thyroid hormones

2. Water-Soluble Hormones

Can dissolve in blood Large water-soluble hormones do not require proteins Small water-soluble hormones use proteins to prevent them from filtering out of blood Short lived Leave system rapidly because they are filtered out by kidneys into urine

How are hormones removed from the body? All are either destroyed by the target cell or destroyed by enzymes. Three types of stimuli cause hormones to be released: Humoral – hormones that are released in response to blood levels of a substance or

chemical changes. Neural -- action potentials in neurons cause neurotransmitter to be released into

synapse along with the hormone. In some cases, the neurotransmitter causes the target cell to secrete a hormone. Some neurons secrete chemical messengers directly into the blood.

Hormonal - a hormone is secreted and, in turn, causes another hormone to be secreted.

Humoral, Neural, and Hormonal stimuli can also inhibit the release of a hormone. Humoral Stimulation of hormone release Calcium levels of the blood are too low à endocrine cell releases PTH hormone à osteoclast activated à calcium levels start to rise Humoral Inhibition of hormone release Calcium levels of blood are too high à endocrine cells are inhibited and no not release hormone à osteoclasts are NOT activated à calcium levels start to drop Neural stimulation of hormone release Neurons in the hypothalamus release “releasing hormones” à travel through blood à Anterior pituitary gland à target endocrine cell in pituitary secretes hormone Neural inhibition of hormone release Neurons in the hypothalamus release “inhibiting hormones” à travel through blood à Anterior pituitary glandà prevents target endocrine cell in pituitary from secreting hormone

Hormonal Stimulation of hormonal release Hormone from the pituitary gland is released into the blood à target endocrine organ or cell is stimulated à hormone is released Hormonal Inhibition of hormonal release Hormone from the pituitary gland is released into the blood à target endocrine organ or cell is inhibited à hormone is prevented from being released Negative feedback Most commonly used in the body Self-limiting system – it stops itself Endocrine organ secretes a Hormone à hormone reaches target à effect à results of the effect are sensed by the endocrine organ à endocrine organ stops secreting hormone Positive feedback Rarely used in the body Self-propagating system – keeps itself going, can only be stopped by an outside factor Endocrine organ secretes a hormone à hormone reaches target à effect à results of the effect are sensed by the endocrine organ à endocrine organ secretes even more hormone Receptor – a molecule where a hormone binds to its receptor site”, VERY specific for hormones Types of receptors:

1. Nuclear receptors – these are for lipid-soluble hormones Small lipid-soluble hormones pass through the cell membrane, cytoplasm, and attach to receptors on the nuclear envelope. They then react with DNA or enzymes in the nucleus, resulting in a specific segment of DNA being transcribed. Response takes several minutes to hours Steroids, thyroid hormones bind to nuclear receptors

2. Membrane-bound receptors – these are for water-soluble hormones Water-soluble hormones cannot pass through the cell membrane, stay on surface Hormone binds to a membrane-bound receptor in the cell membrane on the surface. The protein is activated and responds by making changes that end up with a response inside the cells. VERY RAPID – almost instant because this activates enzymes that are already created Proteins, peptides, epinephrine, norepinephrine

Process of G-protein activation – diagram on page 273. (just know the steps below)

1. Water soluble hormone binds to receptor 2. Receptor activates the G protein 3. The activated G protein, separates from the receptor 4. The part of the G protein that separated turns ATP into cAMP (cyclic AMP) 5. The cAMP activates enzymes in the cytoplasm of the cell 6. Enzymes in the cytoplasm inactivate the cAMP by converting it into AMP.

(they change the form so that it is no longer cyclic)

Amplification – process by which one water-soluble hormone activates a single receptor and that receptor activates thousands of second messengers, increasing the hormone signal. (see the cascade effect on p-age 274) Know the major endocrine organs and the things they regulate. Hypothalamus – Part of the brain that controls the

anterior part of the pituitary by secreting neurohormones

Pituitary gland – has two parts: Anterior Pituitary and Posterior Pituitary Anterior Pituitary is responsible for Growth, thyroid, Sex characteristics, and Skin melanocyte activity Stress Hormones Posterior Pituitary is responsible for Regulating water Contractions during labor Mammary glands secreting milk Thyroid –

Metabolism – increase rate Calcitonin – decreases osteoclast activity

& increase osteoblast activity When blood calcium is high Parathyroid PTH (parathyroid hormone) Decreases osteoblast activity & Increases osteoclast activity when Blood calcium is low Adrenal Medulla (middle) Epinephrine – sympathetic activation Adrenal Cortex (outer edge) Cortisol and others – Stress response

Pancreas – Insulin– increases uptake of glucose into muscle, fat, liver Glucagon – increases breakdown of glucagon and release of glucose into the blood. Testes, Ovaries – testosterone (male), female (estrogen, progesterone) Reproductive organs, secondary sexual characteristics Thymus – Thymosin – promotes immune system development Pineal gland Melatonin –controls sleep

Problems with Endocrine System “hypo” means not enough, “hyper” means too much. Pituitary Gigantism – overactive pituitary in childhood, acromegaly if starts in adulthood Pituitary dwarfism – underactive pituitary Thyroid Hypothyroidism – decreased metabolic rate, fatigue, hair loss, fluid in tissues Hyperthyroidism – agitation, extreme nervousness, chronic fatigue (Grave’s disease) Parathyroid Hyperparathyroidism – abnormally high PTH (parathyroid hormone) secretion often caused by a

tumor. Osteoclasts are overly active, high levels of calcium are in the blood, kidney stones are produced, bone becomes soft, deformed, and easily broken.

Hypoparathyroidism – abnormally low PTH secretion, low levels of calcium are in the blood, Excess calcium causes tingling, muscle twitches, spasms, tetanus Thymus – tumors or anything suppressing thymus secretions cause a compromised immune system. This means the person will be more likely to get all kinds of infection and might experience weakness in the muscles all over the body Adrenal Glands Underactive adrenal glands – most common is Addison’s disease – weakness, fatigue, weight loss, increased pigmentation of the skin (like a sunburn), salt craving, some joint pain, some depression – most of the symptoms can be traced to insufficient cortisol secretion. overactive adrenal glands – Cushings – over secretion of Cortisol – upper body obesity, round face, sometime a fatty

hump between shoulders, thin arms and legs, weakness, fatigue Steroid overproduction – exaggerated male characteristics in both males and females Pancreas Diabetes – type 1 – found in children – pancreas does not secrete enough insulin

- Type 2 – found in older adults – not enough insulin receptors Pineal Gland Underactive - Depression, peptic ulcers, and sexual dysfunction caused by a

deficiency of melatonin, insomnia

Overactive – difficulty concentrating, sensitivity to light, headaches, irritibility Testes and Ovary – both secrete testosterone High levels of testosterone Can make too much testosterone – women become more aggressive, more body hair,

larger muscles, look more masculine Hirsuitism – excess hair, especially hair on women where there is usually none

Low levels of testosterone Less energy, strength, stamina, lower aggressiveness, weight gain, osteoporosis (weak bones)