Homeostasis & Endocrine System

Nervous system communication

Takes place through neurons, messages are transmitted rapidly. Affects specific cell types

Hypothalamus

Integrates neural and endocrine functions. Located beside the base of the brainstem

Endocrine Glands

Ductless. Secretes chemical messengers directly into the bloodstream

Hormones

Chemical Messengers

Endocrine System

Composed of endocrine glands and hormones

Endocrine system actions

Slower and longer lasting effects. Affects a broad range of cell types

Homeostasis

State of steady internal physical and chemical conditions maintained by living systems

Distinctions between Nervous and Endocrine systems are:

Arbitrary.En

Endocrine and Nervous systems both have responses regulated by:

Negative feedback loops

Regulation of physiological processes:

Involves nervous and endocrine systems acting in conjunction

Establishing a link between hormones and target organs:

Removing a rooster’s testes and gauging behavioral differences

Capons without testes:

Did not crow, fight, try to mate, grow, or develop male plummage

When testes were replaced

Capons began to look and act like roosters

Visualizing hormones

Nuclear scanning devices (PET), high powered microscopes, stains, ingestible capsules

Hypothalamus secretes:

Releasing and inhibiting hormones

Hypothalamus function

Regulates anterior pituitary hormones

Anterior pituitary secretes:

Human Growth Hormone, Thyroid Stimulating Hormone, Adrenocorticotropic Hormone, Follicle Stimulating Hormone, Luteinizing Hormone, ProlactineP

Posterior pituitary secretes:

Antidiuretic Hormone, Oxytocin

Thyroid secretes:

Thyroxine, Calcitonin

Parathyroid secretes

Parathyroid hormone

Adrenal cortex secretes

Glucocorticoids, mineralocorticoids, gonadocorticoids

Adrenal Medulla secretes

Epinephrine and Norepinephrine

Pancreas secretes

Insulin, Glucagon

Ovaries secrete

Estrogen, Progesterone

Testes Secrete

Testosterone

Lipid Soluble Hormones

Composed of either lipids or amino acids. Can diffuse through the lipid bilayer of cell membranes. Can bind to receptor proteins

Water Based Hormones

Composed of Amino Acids. Bind to the surface of a target cell causing reactions inside the cell. Hormone impact is greatly amplified. Enzymes deactivate the hormone

Antidiuretic Hormone (ADH) function

Makes kidney tubules more permeable to water. Less but more concentrated urine. Blood pressure increases

ADH Negative feedback loop.

ADH is released.
Water is reabsorbed, raising blood pressure
ADH secretion is stopped

Antidiuretic Hormone

Produced by the posterior pituitary, directed by the hypothalamus

Inability to produce ADH

Causes Diabetes Insipidus

Tropic hormones

Targets endocrine glands to release other hormones

Step 1/3 for a negative feedback loop

Hypothalamus sends releasing hormone into the anterior pituitary

Step 2/3 for a negative feedback loop

Anterior pituitary releases tropic hormone into the bloodstream

Step 3/3 for a negative feedback loop

Tropic hormone reaches target cells releasing a hormone that inhibits the release of the first two hormones

Pituitary gland

Endocrine gland with 2 lobes. Located in the center of the head. Master gland (releases tropic hormones)

Parts of the pituitary gland

Anterior and posterior

Posterior pituitary

Part of the nervous system. DOES NOT produce hormones.

Posterior pituitary releases:

Antidiuretic Hormone and Oxytocin

Anterior pituitary

Hormone synthesizing

Anterior pituitary hormones:

Human Growth Hormone, Prolactin, Thyroid Stimulating Hormone, Adrenocorticotropic Hormone, Follicle Stimulating Hormone, Luteinizing Homone

Portal System

Series of blood vessels

Human Growth Hormone

Regulates growth, development, and metabolism. Affects almost every body tissue.

What does Human Growth Hormone do?

Synthesizes proteins, Grows tissue and divides cells (muscle and connective tissue, growth plates, bones), breaks down and releases fats in adipose tissue through metabolic processes

Gigantism

Results from excessive amounts of hGH being released during childhood.

Dwarfism

Results from deficient amounts of hGH during childhood

Acromegaly

Results in an overproduction of hGH during adulthood

Acromegaly causes

Widening of bones, soft tissue, and the face. Thickening ribs. Enlargement of hands and feet. Can cause cardiovascular disease, sugar intolerance, breathing problems, muscle weakness, colon cancer

Producing synthetic hormones

Gene code for hormone production is inserted into bacteria. Bacteria begins producing the hormone

Thyroid Gland

Directly below the larynx, connected to the trachea by tissue

Thyroxine

Increases metabolism rate. Does not have one specific target organ

Thyroxine target cells

Heart, skeletal muscles, liver, kidneys to increase cellular respiration

Thyroxine influence

Organizes various cells into tissues and organs for growth and development

Hypothyroidism

Low quantities of thyroxine. May cause Cretinism

Cretinism

Causes mental delays unless treated. In adulthood, patients are tired, have a slow pulse, puffy skin, experience hair loss and weight gain

Hyperthyroidism

Overproduction of thyroxine. Causes anxiety, insomnia, heat intolerance, irregular heartbeat, weight loss.

Graves’ disease

Severe state of hyperthyroidism. Immune system attacks the thyroid. Causes eye swelling.

Thyroxine negative feedback loop

Anterior pituitary releases TSH, thyroid gland releases thyroxine, thyroxine blood concentration raises, hypothalamus and anterior pituitary stop releasing hormones

Thyroxine levels

Should be relatively constant

Signal to stop TSH secretion

Thyroxine needs 4 iodine molecules. If there is insufficient iodine thyroxine cannot be made and TSH secretion will not stop

Goitre

Constant TSH secretion. Causes an enlargement of the thyroid gland

Calcitonin

Secreted from the thyroid gland. Stops calcium from being released into the blood. Reduces breakdown of bones.

Parathyroid glands

4 Glands attached to the thyroid. Produces Parathyroid hormone.

PTH secretion

Synthesized in response to low calcium in the blood

PTH function

Stimulates bone cells to break down bone material, releasing calcium into the blood. Also stimulates kidneys to absorb calcium from urine.

PTH negative feedback loop

Releases when calcium levels are low

Inhibits when calcium levels are normal

Adrenal Gland

Looks like fedoras on the kidneys. Has an inner (medulla) and outer layer (cortex)

Adrenal Medulla

Short term stress response; Fight or Flight. Releases Epinephrine and norepinephrine.

Adrenal Medulla response

Sympathetic neurons carry a signal to the Hypothalamus. Neurons stimulate the release of stress hormones

Effects of Epinephrine and norepinephrine

Increases breath rate, heart rate, blood pressure, blood flow to core organs, conversion of glycogen to glucose

Epinephrine

Can stimulate the heart during cardiac arrest and open airways during anaphylactic shock

Norepinephrine

Produces an excitatory effect on target muscles

Epinephrine and norepinephrine effects

Similar to effects of the sympathetic nervous system but their influence lasts 10x longer

Adrenal Cortex

Long term stress response. Releases stress hormones that trigger sustained physiological response. Glucocorticoids, Mineralocorticoids, and gonadocorticoids

Glucocorticoids

Steroid hormones, treats inflammation.

Mineralocorticoids

Steroid hormones, regulates the bodies minerals

Gonadocorticoids

Sex hormones, supplement hormones produced by the gonads (testes and ovaries)

Cortisol secretion

Glucocorticoid. Released when the brain detects danger. The hypothalamus secretes Adrenocorticotropic Hormone which triggers the release of Cortisol

Cortisol function

Raises glucose levels, promotes the breakdown of muscle protein into amino acids.

Cortisol Negative Feedback loop

Increased blood concentration sends a message to the hypothalamus to tell the anterior pituitary to stop producing Adrenocorticotropic Hormone

Long term stress

Sustained cortisol and chronic stress leads to impaired thinking, heart damage, high blood pressure, diabetes, infection, and early death

Cortisol and the immune system

Anti-inflammatory, stopping the immune system and making the body vulnerable to infections

Aldosterone

Mineralocorticoid. Stimulates distal tubules and nephrons to increase sodium absorption (taking water by osmosis). Urine output is lowered but more concentrated

Low aldosterone

Needs to be treated quick as electrolyte imbalance is fatal

Addison’s disease

Results when the Adrenal Cortex is damaged. Inadequate mineralocorticoids and glucocorticoids are secreted

Addison’s disease symptoms

Hypoglycemia, electrolyte imbalances, rapid weight loss, general weakness

Pancreas

Located behind the stomach, connected to the small intestine by the pancreatic duct.

Pancreas is considered a ____ gland

Exocrine.

Exocrine Glands

Secretes hormones from ducts

Islets of Langerhans

Endocrine cells within the pancreas that secrete hormones directly into the bloodstream

Hormones from Islets of Langerhans

Insulin and Glucagon

Alpha cells

Secrete Glucagon

Beta Cells

Secrete Insulin

Insulin

Makes target cells more permeable to glucose (lowers blood sugar)

Glucagon

Stimulates liver to convert glycogen into glucose (raises blood sugar)

Diabetes Mellitus

Results when the body does not produce or react properly to insulin

Hyperglycemia

High blood glucose. Cells are impermeable to glucose. Body metabolizes proteins and fats

Glucose lost in urine

Affects the osmotic gradient in the kidneys causing a loss of water in urine

Long term hyperglycemia

Kidney failure, blindness, nerve damage, gangrene, degenerated alpha cells

Type one diabetes

Juvenile diabetes and insulin dependent. Immune system destroys beta cells; No insulin. Happens during childhood. Need daily insulin injections