Unit A – Endocrine systemUnit A – Endocrine system

+ whereas the nervous system makes short-term changes to restore homeostasis, the endocrine system works more slowly and tends to make more long-term changes

+ hypothalamus can be considered part of both the nervous and endocrine systems– hypothalamus regulates the pituitary gland, the

master gland, through nerve stimulation– pituitary gland stimulates other endocrine glands

secrete chemicals that affect the nerve activity of the hypothalamus

+ chemical regulators, from the Greek word hormon which means “to set into motion”

– hormones act to speed up or slow down body processes+ produced in one part of the body, but affect another part+ hormones do not affect all cells, only those with the correct

receptor for that particular hormone+ classified according to where they work (activation site)

– most hormones target a specific target tissue e.g. parathyroid hormone (regulates calcium levels) e.g. gastrin (stimulates stomach cells to produce digestive enzymes)

– non-target hormones affect cells throughout the body e.g. human growth hormone (cause long bones to grow) e.g. insulin (produced by the islets of Langerhans in the pancreas, secreted

when blood sugar levels are high & regulates blood sugar) e.g. epinephrine (adrenaline) (produced in times of stress)

+ negative feedback control system– prevents chemical imbalances in the body– when a hormone causes a body response, it triggers

receptors and the response is inhibited, restoring homeostasis

– e.g. pituitary gland produces male LH (luteinizing hormone) activates testosterone production in the testes testosterone levels increase high levels of testosterone inhibits the release of male LH

+ when negative feedback systems fail, medical disorders can result– e.g. gigantism results from a failure to turn off the

production of growth hormone

stimulus•high blood glucose

responding gland•pancreas•Islet βcells

hormone produced•insulin

target•fat cells•liver cells•other cells

effects•conversion of glucose into glycogen

•glucose uptake

result•blood glucose falls

negative feedback•pancreas β cells no longer getting high blood glucose message•stop producing insulin

Numbered:1. Thyroid2. Adrenal Cortex3. Adrenal Medulla4. Pancreas5. Ovaries6. Testes

Not numbered:+ hypothalamus+ pituitary+ parathyroid

+ anterior lobe (towards the front)– produces its own hormones– release of pituitary hormones regulated by the

hypothalamus via other hormones thyroid-stimulating hormone (TSH) protein hormone

÷ stimulates thyroid gland to release thyroxine, which stimulates cell metabolism

corticotrophin adrenal steroid (ACTH) steroid hormone÷ stimulates adrenal cortex to release hormones involved in stress

growth hormone (GH) a.k.a. somatotropin protein hormone÷ targets most cells but effects are most pronounced in bones and

cartilage, promotes growth÷ disorders related to GH

= dwarfism – underproduction of GH= gigantism – overproduction of GH= acromegaly – continued growth of jaw, forehead, fingers and toes

into adulthood÷ production inhibited when hypothalamus releases somatostatin

follicle-stimulating hormone (FSH)÷ in ovaries, stimulates follicle development ÷ in testes, promotes the development of sperm cells

luteinizing hormone (LH)÷ in ovaries, stimulates ovulation÷ in testes, stimulates the production of testosterone

prolactin (PRL)÷ targets mammary glands and stimulates and maintains milk

production÷ production inhibited when hypothalamus releases dopamine

+ located at the base of the neck in front of the windpipe

+ produce hormones involved in regulating metabolism and tissue growth and differentiation– thyroxine

promotes the oxidation of sugars and other nutrients÷ 50% released as heat÷ 50% converted to ATP

control of thyroxine÷ receptors in hypothalamus are informed of low metabolic rate

thyroid-releasing factor (TRF) stimulates pituitary to release TSH carried by blood to thyroid gland thyroid releases thyroxine stimulates cells to use more sugar

÷ high levels of thyroxine inhibits TRF from hypothalamus

+ thyroid disorders– goiter

caused by low levels of iodine, a main component of thyroxine thyroxine no longer completes negative feedback loop TRF keeps being produced, so thyroid keeps being stimulated, causing it to enlarge why table salt contains iodine (iodized salt)

– hyperthyroidism people with high thyroid activity are typically

÷ thin÷ warm, ÷ overactive

excess glucose is converted to heat and ATP– hypothyroidism

people with low thyroid activity are typically÷ less thin÷ intolerant of the cold÷ tend to have dry skin

because excess glucose is converted to fat once glycogen stores are full

+ The parathyroid glands are small glands in the neck that produce parathyroid hormone.

+ Humans have four parathyroid glands, which are usually located behind the thyroid gland

+ control the amount of calcium in the blood and within the bones

+ located above each kidney+ each gland is composed of two smaller glands

– adrenal medulla inner gland, stimulated by sympathetic nerves in times of stress produces hormones that initiate fight-or-flight

response÷ epinephrine÷ norepinephrine

+ adrenal cortex– outer gland, surrounds adrenal medulla– produces two main types of hormones

glucocorticoids – e.g. cortisol÷ affect blood glucose levels

mineralocorticoids – e.g. aldosterone÷ help maintain body fluid levels

+ cortisol – help body recover from stress, increases

amino acid levels in blood – converted into glucose by liver, or used

in protein synthesis to repair damaged cells

– as cortisol levels rise, cells within the hypothalamus and pituitary gland decrease the production of regulatory hormones and cortisol levels drop

+ aldosterone– increase sodium retention and water

reabsorption by the kidney

+ contains two types of cells– digestive enzyme producing cells– hormone producing cells

located in Islets of Langerhans+ produce two hormones

– insulin produced in the beta cells released when blood sugar level is high makes liver and muscle cells permeable to glucose in the liver, excess glucose is stored as glycogen, which helps return blood

glucose levels to normal– glucagon

produced in the alpha cells causes an increase in blood sugar levels after a period of fasting causes blood

glucose to drop promotes the conversion of glycogen back to glucose

+ Several different types of diabetes exist, and there is often confusion on the part of the public about which type is which.

+ Unless “diabetes insipidus” is specified, it is assumed the type of diabetes being discussed is diabetes mellitus.

+ Type I and Type II diabetes are both subtypes of diabetes mellitus.

Diabetes Insipidus Diabetes Mellitus

Also known as:

Type I Juvenile diabetes Insulin-dependent

diabetes

Type II Adult-onset diabetes

Cause: Body does not

make/secrete enough ADH

Beta cells do not produce enough insulin

Tissues do not recognize the effect of insulin

Area of dysfunction: Hypothalamus, or

posterior lobe of pituitary gland

Islet cells in pancreas Body cells

Symptoms:

Large volumes of urine

Dehydration Thirst

Large volumes of urine Dehydration Thirst Weight loss Acetone-scented breath Sweet-smelling urine

Glucose in urine: No Yes Yes

Glucose levels in blood: Unaffected Hyperglycemia Hyperglycemia

Treatment: Anti-diuretic

medications

Insulin replacement via injections

Islet transplants

Medications that make the body more sensitive to insulin

Hormone Source Function Controlled by

Thyroid stimulating hormone (TSH)

Anterior pituitary Stimulates thyroid to produce thyroxine

Thyroxine levels in the blood

Thyroxine Thyroid Regulates metabolism in all cells

Thyroxine levels in the blood

Calcitonin Thyroid Reduces blood calcium Calcium levels in the blood

Parathyroid hormone (PTH)

Parathyroid Increases blood calcium (released from bones)

Calcium levels in the blood

Adrenocortico-tropic hormone (ACTH)

Anterior pituitary Stimulates adrenal cortex to release stress hormones

Cortisol levels in the blood

Cortisol Adrenal cortex Converts amino acids into glucose during stress, reduces inflammation

Glucose levels in the blood

Hormone Source Function Controlled by

Human growth hormone (hGH)

Anterior pituitary Stimulates growth Hypothalamic hormones

Antidiuretic hormone (ADH)

Hypothalamus Promotes water retention by the kidneys

Water/salt balance

Epinephrine (Adrenaline)

Adrenal medulla Prepares body for stress

Sympathetic nervous system

Aldosterone Adrenal cortex Increases salt uptake and water reabsorption

Levels of Na+ and K+ in blood

Insulin Pancreas (β cells) Converts glucose to glycogen and increases cells’ uptake of glucose

Glucose levels in the blood

Glucagon Pancreas (α cells) Converts glycogen into glucose to increase blood glucose levels

Glucose levels in the blood