Endocrine System

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Homeostasis

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Body adjusts to fluctuating environment to maintain a balance of the internal environment. Typically done with a feedback system. Nervous system and endocrine system work together

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Endocrine system

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Hormone system adjusts for long-term change. Effects occur more slowly over a longer duration with only chemical (hormonal) stimulation

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Hormones

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Chemical messengers produced by endocrine glands that have special regulatory effects on certain cells of the body. Must have a specific receptor

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Types of hormones

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Protein hormones and steroid hormone

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Protein hormones

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Water soluble. Combines with receptor found on the target cell membrane. Hormone-receptor complex stimulates reactions that result in action of the hormone.

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Steroid hormones

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Fat soluble. Combines with receptor found inside the cytoplasm of target cell. Hormone-receptor complex directly targets DNA to stimulate/inhibit production of specific proteins.

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Examples of protein hormones

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Insulin, growth hormone, TSH, oxytocin

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Examples of steroid hormones

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Sex hormones, cortisol, aldosterone

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Negative feedback

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Body responds to change by reversing the direction of the change, maintaining homeostasis

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Positive feedback

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Process where a small effect is amplified

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Hypothalamus

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Area of brain that regulates pituitary gland through nerve and hormonal stimulation.

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Releasing hormones

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Controlled by hypothalamus to stimulate the release of stored hormones from the anterior pituitary gland

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Pituitary gland

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Stores and releases hormones that affect other glands. Connected to and controlled by the hypothalamus. Has 2 lobes

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Pituitary gland lobes

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Anterior and posterior lobes

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Posterior pituitary lobe

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Stores and releases hormones ADH and oxytocin

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Antidiuretic hormone (ADH)

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Hormone that targets the kidneys to increase water resorption when blood solute concentration is high; dilutes blood conc, increases blood pressure and decreases urine volume . Negative feedback

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Oxytocin

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Responsible for uterine contractions and contraction of milk ducts to release milk. Stimulated by birth and suckling. Positive feedback

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Anterior pituitary lobe

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Responsible for secretion of GH, TSH, ACTH, prolactin, FSH, LH. Hormones only released when hypothalamus secretes releasing hormones.

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Growth Hormone (GH)

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Acts directly on most body tissues and bones to promote protein manufacture, fat metabolism, and growth.

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Dwarfism

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Low GH during childhood

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Gigantism

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High GH during childhood

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Acromegaly

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GH production continues after growth plates are fused- bones can't lengthen, only widen

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Thyroid stimulating hormone (TSH)

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Stimulates thyroid to release thyroxine

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Adrenocorticotropic hormone (ACTH)

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Stimulates adrenal cortex to release cortisol and aldosterone

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Prolactin

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Stimulates mammary glands to produce milk

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FSH and LH

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Gonadotropins. Stimulates gonads to produce sex cells and sex hormones

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Adrenal glands

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Above each kidney. Each composed to 2 glands in one shell. Adrenal medulla and adrenal cortex

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Adrenal medulla

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Produces epinephrine and norepinephrine to help body adjust to short-term stress. Fight-or-flight response. Regulated by nervous system

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Epinephrine/norepinephrine

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Stimulated by stress and the sympathetic nervous system to increase glucose conversion from carbs and glycogen (energy), increase blood pressure, increasing breathing rate, decrease blood to skin and digestive system

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Adrenal cortex

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Stimulated by ACTH to produce glucocorticoids (cortisol), mineralcorticoids (aldosterone),and sex hormones

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Cortisol

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Glucocorticoid. Produced in response to long-term stress to increase glucose concentrations available for energy by converting to amino acids (muscle protein breakdown). Acts as anti-inflammatory. Negative feedback

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Aldosterone

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Mineralcorticoid. Produced in response to low blood pressure, to increase absorption of sodium into blood and increase blood pressure

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Pancreas

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Large gland found behind the stomach. Hormones insulin and glucagon are produced by the islets of Langerhans cells

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Insulin

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Produced by beta cells of islets of Langerhans when blood sugar levels (glucose conc) are too high. Increased permeability to glucose, glucose is converted to glycogen for storage in muscle and liver cells and converted to fat by adipose tissue. Blood sugar levels decrease. Negative feedback

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Glucagon

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Produced in alpha cells of islets of Langerhans. Released when blood sugar levels too low. Promotes conversion of glycogen to glucose in muscle and liver, and fat into glucose by adipose tissue. Blood sugar levels increase. Negative feedback

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Diabetes mellitus

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Results from inability to produce insulin or reduced sensitivity. High blood sugar. Symptoms: glucose in urine, large volumes of urine, increased thirst, fatigue, weight loss, fruity smelling breath (ketones)

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Type 1 (juvenile) diabetes

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Immune system destroys beta cells in islets of Langerhans. Treated by insulin injections

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Type 2 (maturity-onset) diabetes

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Cause by faulty insulin receptors on cell membranes. Occurs later in life and associated with obesity. Can be controlled by diet (low carbs and fats) and exercise. Some people treated with antibiotic drugs

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Thyroid gland

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Located at the base of the neck, in front of trachea. Produces thyroxine and calcitonin to regulate metabolic processes

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Thyroxine

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Targets body cells to increase metabolic rate by increasing oxidation of sugar and regulates growth and development. Negative feedback

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Hypothyroidism

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Low levels of thyroxine. Sugars and nutrients aren't oxidized at quickly, causing: weight gain, loss of energy, sluggishness, intolerance of cold and dry skin

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Hyperthyroidism

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High levels of thyroxine, causing: irritability, weight loss, increased blood pressure and heart rate, nervousness, hyperactivity, insomnia, bulging eyes.

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Goiter

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Enlargement of thyroid gland due to lack of iodine, underactive thyroid gland (decrease in production of thyroxine) or over production of TSH. Continually stimulated thyroid causes enlargement

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Calcitonin

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Stimulated by high blood calcium concentration. Causes increased calcium deposits on bones and increased secretion of calcium by kidneys. Decreases calcium concentration in blood. Negative feedback

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Parathyroid glands

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4 small glands embedded in thyroid secrete PTH to regulate blood calcium and lower phosphates

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Parathyroid hormone (PTH)

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Stimulated by low blood calcium concentrations to promote release of calcium from bones and increase resorption of calcium by kidneys. Increases calcium concentration in blood. Negative feedback

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Thymus gland

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Near centre of the chest. Produces thymosin.

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Thymosin

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Assists in maturation of T-cells

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Pineal gland

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In the brain. Secretes melatonin

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Melatonin

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Produced during dark periods of each day. Influences sleep-wake cycles

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Prostglandins

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Hormones that have an effect in the area where they are produced. Constrict/dilate blood vessels, bronchioles, intestines. Aspirin works by blocking prostglandins.

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Gonadotropin

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Hormones produced by pituitary gland that regulate functions of testes and ovaries

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GnRH

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Gonadotropin releasing hormone. Messenger from hypothalamus to stimulate FSH and LH secretions from pituitary