The Endocrine System 16

Endocrine System: Overview Endocrine system – the body’s second controlling system which influences metabolic activities of cells by means of hormones secreted from glands Major organs are the Endocrine glands – pituitary, thyroid, parathyroid, adrenal, pineal, thymus, pancreas and gonads Continued on the next slide

Endocrine System: Overview (cont) The hypothalamus has both nervous functions and releases hormones Other tissues and organs that produce hormones include adipose cells, cells in the walls of the small intestine, stomach, kidneys, and heart

Hormones – chemical substances secreted by cells of endocrine glands Regulate the metabolic function of other cells Carried by the bloodstream

Major Endocrine Organs: Pituitary (Hypophysis) Pituitary gland Releases 11 hormones made by either the hypothalamus or the pituitary itself Regulates major metabolic processes on the body Growth, stress, reproductive cycles, water balance to name a few.

Secretes thyroid hormone (TH) in two forms Deals with metabolism, temperature, nerve and muscle development Secretes calcitonin lowers calcium levels

Secretes parathyroid hormone (PTH) Increases blood calcium levels

Adrenal hormones Increases sodium and lowers potassium blood levels through the kidney Raises blood volume and pressure constricts blood vessels, and raises heart rate Help body deal with stress Epinephrine (adrenalin) and norepinephrine Cause fight or flight response (short term)

Controls blood sugar levels Insulin pancreas Controls blood sugar levels Insulin Lowers blood sugar Glucagon Raises blood sugar

ovary Female primary sex organ; produces female sex hormones Produces estrogen Produces progesterone Run the menstrual cycle Development of the female body sexually

Produces male sex hormones testis Produces male sex hormones Mainly secretes testosterone Produces secondary sex characteristics and sex drive

Pineal gland Produces melatonin Involved with sleep patterns

thymus secretes thymosin Help developed white blood cells

Hormones and functions TH- controls metabolism Calcitonin- lowers blood calcium levels PTH- raises blood calcium levels Epinephrine- causes fight or flight response Insulin- lowers blood sugar levels Glucagon- raises blood sugar levels Melatonin- regulates sleep cycles Thymosin- develops white blood cells

Part of the brain that controls the endocrine system hypothalamus Part of the brain that controls the endocrine system Secretes several hormones that act on the pituitary or are only stored in the pituitary

Target Cell Specificity Hormones circulate to all tissues but only activate with very specific target cells Target cells must have specific receptors to which the hormone binds These receptors may be intracellular or located on the plasma membrane

Amino acid based (proteins) Types of Hormones Amino acid based (proteins) – most hormones belong to this class Steroids – gonadal and adrenocortical hormones - lipid (cholesterol) based PLAY InterActive Physiology®: Endocrine System: Orientation

Steroid Action (simplified) Steroids cross the cell membrane They travel through the cytoplasm and enter the nucleus They then turn on genes (DNA) which then creates a cellular protein (protein synthesis)

Amino acid/Protein hormone action (simplified) Hormone binds to a cell membrane receptor This complex binds to another protein in the membrane This binding process activates a second messenger and in some cases a third messenger The second or third messengers then trigger a response in the cytoplasm of the cell

Control of Hormone Release Blood levels of hormones: Are controlled by negative feedback systems A negative feedback is a system that stops the production of a molecule PLAY InterActive Physiology®: Endocrine System: Biochemistry, Secretion, and Transport of Hormones

Gigantism- Acromegaly- Dwarfism Diabetes insipidus Endocrine disorders high GH, normal body proportion Acromegaly- high GH but with enlarged extremities Dwarfism Low GH Diabetes insipidus Low ADH, huge urine output

Hyperthyroidism (over secretion) Endocrine disorders Hyperthyroidism (over secretion) high metabolic rate, increased appetite Graves Disease Autoimmune disease? Sweating, increased metabolism, protruding eyes Hypothyroidism (under secretion) Low metabolic rate, weight gain, Intolerance to heat (called cretinism in babies when severe) May be due to lack of iodine, which forms a goiter

Diabetes mellitus Hypoglycemia Endocrine disorders Insulin is either absent or deficient Genetic and viral infections Hypoglycemia Anxiety, nervousness