Ch. 15

nervous and endocrine

• Have ducts carry secretion to an epithelial surface or the mucosa of the digestive tract: “external secretions” • Extracellular effects (food digestion)

• No ducts • Contain dense, fenestrated capillary networks which allow easy uptake of hormones into bloodstream • “Internal secretions” • Intracellular effects such as altering target cell metabolism

releases hormones, releases bile into ducts, releases albumin and blood-clotting factors into blood (not hormones)

• Gap junctions • Neurotransmitters • Palacrine (local) hormones • Hormones

• Pores in cell membrane allow signaling molecules, nutrients, and electrolytes to move from cell to cell

• Released from neurons to travel across synaptic cleft to second cell

• Secreted into tissue fluids to affect nearby cells

• Chemical messengers that travel in the bloodstream to other tissues and organs

those organs or cells that have receptors for a hormone and can respond to it

glands, tissues, and cells that secrete hormones

the study of this system and the diagnosis and treatment of its disorders

organs that are traditional sources of hormones

chemical messengers that are transported by the bloodstream and stimulate physiological responses in cells of another tissue or organ, often a considerable distance away

• causes constrictions or dilation in vascular smooth muscle cells • causes aggregation or disaggregation of platelets • sensitize spinal neurons to pain • induce labor • decrease intraocular pressure • regulate inflammation

• McClintock effect • Androstenol masks

• Both serve for internal communication • Speed and persistence of response • Adaptation to long-term stimuli (think homestasis) • Area of effect

Nervous: both electrical and chemical Endocrine: only chemical

Nervous: reacts quickly (1 to 10ms), stops quickly Endocrine: reacts slowly (hormones release in seconds or days), effect may continue for weeks

Nervous: response declines (adapts quickly) Endocrine: response persists (adapts slowly)

Nervous: targeted and specific (one organ) Endocrine: general, widespread effects (many organs)

• Neurons trigger hormone secretion • Hormones stimulate or inhibit neurons

• Reproduction • Growth and development • Maintenance of water/nutrient balance of blood • Regulation of cellular metabolism • Energy balance • Mobilization of bodily defense mechanisms

• Alters plasma membrane permeability or potential by opening or closing ion channels (insulin) • Stimulates synthesis of an enzyme or proteins (prolactin) • Induces secretory activity (FSH or LH) • Stimulates mitosis (GH) • Activates or deactivates an enzyme

potent

enzyme amplification

stimulus

high

1. Low receptor density; weak response 2. Increased receptor density; increased sensitivity 3. Stronger response

1. High receptor density; strong response 2. Reduced receptor density; reduced sensitivity 3. Diminished response

receptors

• Sensitivity is increased • Late pregnancy, uterus produces receptors for oxytocin

• Cell less sensitive to hormone • Happens with long-term exposure to high hormone concentrations - Adipocytes down-regulate when exposed to high concentrations of insulin

pancreatic islets

• Released between meals when blood glucose concentration is falling • In liver, stimulates gluconeogenesis, glycogenolysis, and the release of glucose into circulation raising blood glucose level • In adipose tissue, stimulates fat catabolism and release of free fatty acids • Glucagon also released to rising amino acid levels in blood, promotes amino acid absorption, and provides cells with raw material for gluconeogenesis

• Secreted during and after meal when glucose and amino acid blood levels are rising • Stimulates cells to absorb these nutrients and store or metabolize them lowering blood glucose levels - Promotes synthesis glycogen, fat, and protein - Suppresses use of already-stored fuels - Brain, liver, kidneys, and RBCs absorb glucose without insulin, but other tissues require insulin • Insufficiency or inaction is cause of diabetes mellitus

• Disruption of metabolism due to hyposecretion or inaction of insulin • Symptoms - Polyuria (excess urine output), polydipsia (intense thirst), polyphagia (hunger) - Revealed by elevated blood glucose, glucose in urine, and ketones in the urine

• Excess glucose enters urine and water follows it - Causes polyuria, dehydration, and thirst

It is the inability to control blood glucose levels

Type 1 and type 2

34.2 million

• Frequent urination • Unsusual hunger and/or thirst • Unexplained change in weight • Blurred vision • Sores that heal slowly or not at all • Excessive fatigue

Blindness, loss of limbs, nerve deterioration, kidney and cardiovascular disease

• Insulin is always used to treat type 1 - Insulin injections, insulin pump, or dry insulin inhaler - Monitoring blood glucose levels and controlled diet • Hereditary, susceptibility if infected with certain viruses (rubella, cytomegalovirus) • Autoantibodies attack and destroy pancreatic beta cells

• Problem is insulin resistance - Failure of target cells to respond to insulin • Risk factors are hereditary, age (40+), obesity, and ethnicity (Native American, Hispanic, Asian) • Progressive replacement of muscle with fat • Treated with weight-loss program and exercise since: - Loss of muscle mass causes difficulty with regulation of glycemia - Adipose signals interfere with glucose uptake into most cells • Oral medications improve insulin secretion or target cell sensitivity

too little GH is produced during childhood; results in small stature

too much GH is produced during childhood; results in poor health

overproduction of GH as an adult; results in larger than normal feet, hands, and face

• Stimulates growth of the penis and testes • Responsible for male sex characteristics such as facial, underarm, and public hair • Prompts the larynx and vocal cords to enlarge, resulting in a lower voice • Promotes muscular strength