TEAS Endocrine System

What is the endocrine system?

A set of organs that secrete hormones directly into the circulatory system.

• Complex network of glands and organs

Hormones

The chemicals released into the blood and act as signals to target organs to perform various functions.

What are hormones involved in?

The regulation of many functions in the human body

What is a gland?

A specific type of organ that secretes hormones into the blood to target and affect other organs.

What are the major glands in the endocrine system?

Pineal, pituitary, thyroid, parathyroid, thymus, and adrenal.

What are the major glands in the endocrine system?

Pineal, pituitary, thyroid, parathyroid, thymus, and adrenal.

Pineal gland

A small gland near the center of the brain that secretes melatonin.

Thyroid gland

The gland in the neck that secretes hormones that regulate growth, development, and metabolic rate.

Parathyroid

An endocrine gland in the neck that produces parathyroid hormone.

• Secreted when blood calcium levels are low — raises them.

Thymus

The lymphoid organ that produces T-cells — belongs to the endocrine and lymphatic systems.

• T-cells fight off infections

Adrenal (there are two)

A gland above the kidney that produces hormones to regulate heart rate, blood pressure, and other functions.

Pancreas

The gland of the digestive and endocrine systems that produces insulin and secretes pancreatic juices.

Negative feedback

A mechanism that includes the monitoring for specific homeostatic levels and a signal to a gland. The signal stimulates or inhibits the gland’s secretion in order to maintain homeostasis or cause compensations that returns the level to homeostasis.

What are the organs that contain endocrine tissue and produce hormones?

The pancreas and the ovaries or testes.

What does hypothalamus (part of the brain) do in the endocrine system?

It controls the pituitary gland that is found just below it.

How does the endocrine system regulate many body functions?

By controlling the amount of hormones released.

What body systems are in some way regulated by the endocrine system?

All

• Examples include the regulation of blood production, appetite, reproduction, brain function, sleep cycle, electrolyte balance, growth, sexual development, and response to stress and injury.

What secretes hormones into the blood and for what?

Glands and organs secrete hormones into the blood to be transported to target organs and tissues to control their function.

What hormone does the pancreas release and what does it do?

It releases insulin, which signals cells to uptake sugar.

Sugar

The monomers used to build polysaccharides; also molecules made of two or a few monosaccharide units that are used for fuel in the body.

What hormone does the pineal gland release and what does it do?

It releases melatonin, which is involved in regulating sleep cycles.

Endocrine gland

A gland that secretes hormones. A duct-less gland.

What do endocrine glands produce?

Hormones that have different chemical structures.

What can lipid-based hormones do?

Enter a cell and regulate DNA

How are some nonpolar, fat-soluble hormones such as estrogen and progesterone released?

In a pattern set by age and development, and their effects are long lasting.

What are reproductive hormones responsible for?

Gamete production

When does estrogen production increase and what does it lead to?

It increases at puberty and leads to the development of secondary sex characteristics.

Epinephrine

A polar, water-soluble hormone released by the adrenals in response to stress. Also known as adrenaline.

How are polar, water-soluble hormones such as epinephrine released?

They’re released in response to stress, and their actions are short lived.

What do hormone receptors on the cellular membrane cause?

they cause cellular changes to regulate and control body functions.

What happens when the adrenal glands secrete epinephrine into the bloodstream?

Heart rate, blood pressure, muscle strength and metabolism increase.

• this response is called the “fight-or-flight response.”

What can hormone imbalance cause?

Metabolic diseases such as diabetes, hyperthyroidism, and gigantism.

Diabetes

Pathologically high blood sugar levels that result from a pancreatic hormone regulation malfunction.

Hyperthyroidism

A malfunction of regulatory feedback loops leading to the overproduction of thyroid hormone.

What happens in hyperthyroidism and what can it lead to?

The thyroid gland releases too much thyroxine.

• this can lead to an increase in both weight loss and heartbeat.

What do doctors look for to diagnose hyperthyroidism?

Elevated levels of thyroxine in the blood.

Gigantism (only applies to childen)

excessive growth resulting from overproduction of growth hormone.

• Too much GH in children

When does gigantism occur?

When the pituitary gland makes too much growth hormone, causing excessive growth.

Acromegaly

Too much GH in adults (the equivalent of gigantism in children)

Growth hormone

A secretion of the anterior pituitary that stimulates tissue growth. AKA somatotropin.

Homeostasis

The maintenance of a constant internal environment.

What does homeostasis help cells with?

It helps cells to work as efficiently as possible.

How do most homeostatic mechanism work and what controls them?

Though feedback systems and they’re mainly controlled by endocrine glands.

What do feedback systems bring about and for what?

Physiological and behavioral changes, which help to maintain the internal constancy.

Examples of homeostasis

• Maintaining the constant concentration of glucose in the blood, which is controlled by the hormones insulin and glucagon.

• Maintaining the right amount of water in the blood, which is under the control of antidiuretic hormone (ADH) secreted by the pituitary gland.

Antidiuretic hormone

A secretion from the pituitary gland that increases the amount of water able to be reabsorbed from a collecting duct.

Positive feedback

A mechanism that stimulates glandular secretions to continue to increase, temporarily pushing levels further out of homeostasis, until a particular biological effect is reached (e.g., expulsion of the fetus during childbirth).

What does positive feedback cause?

An increase in the secretion of a hormone.

Example of positive feedback

• the secretion of the hormone oxytocin is an example.

• During childbirth, the cervical stretching from fetal pressure triggers a release of oxytocin from the posterior pituitary

• Oxytocin stimulates uterine contractions that, in turn, cause the fetus to push against and stretch the cervix even more.

• This positive feedback continues until the fetus is expelled through the cervix

How are most levels in the body regulated?

Through negative feedback and influenced by the production of a releasing hormone or an inhibiting hormone.

What does negative feedback do?

Help to maintain homeostasis

What are the cells of the pancreas able to do?

They’re able to adjust the amount of hormone they secrete in proportion to the amount of blood glucose they detect.

What happens when the blood sugar levels are too high?

The beta cells of the pancreas release the hormone insulin.

• this signals the cells to uptake sugar which lowers the blood sugar levels

What happens when blood glucose levels are too low?

Alpha cells secrete a different hormone, glucagon.

What does glucagon promote when glucose levels are too low?

The breakdown of glycogen, which is stored in the liver and in muscle cells, into glucose, which raises blood sugar levels.

• the hormones secretion is stopped hen a homeostatic level of blood glucose is detected.

What is the nervous system involved in?

Rapid communication within the body as it detects stimuli and coordinates responses quickly.

Compare to the nervous system, what is the endocrine system involved in?

Generally, it is involved with comparatively slower and more long-lasting responses to stimuli than the nervous system.

What is the integration between the nervous and endocrine systems called?

“Activation of the neuroendocrine system.”

• Ex: the hypothalamus of the brain directs the activities of the pituitary gland.

• Certain biochemical levels send messages to the hypothalamus, which either stimulates or turns off messages to the pituitary gland (located just below the brain).

What hormones do the specialized cells in the hypothalamus secrete?

“Releasing hormones” or “inhibiting hormones” to the pituitary.

• the pituitary gland then makes and sends specific hormones to target organs. For example, it secretes follicle-stimulating hormone (FSH), which functions in egg development in the ovaries.

What is another example of the activation of the neuroendocrine system?

Childbirth.

• During labor, the pressure of the fetus on the cervix sends signals through the nervous system to the hypothalamus, which results in oxytocin being secreted by the posterior pituitary gland.

Oxytocin

A hormone made by the hypothalamus and stored in the posterior pituitary. One of its functions is to stimulate uterine contractions during childbirth.

Cervix

The passage that forms the lower part of the uterus.

Releasing hormones

Chemical messengers that stimulate the production of certain hormones.

Inhibiting hormones

Chemical messengers that restrict the production of certain hormones.