Biology Chapter 50

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Various things you may need for your high school biology midterm.

Hormones

Substances that are released by cells that act to regulate the activity of other cells in the body.

Endocrine Glands

Ductless organs that secrete hormones either into the bloodstream or into the extra-cellular fluid or liquid around the cell.

Endocrine System

The endocrine glands and specialized cells as a whole.

Exocrine Glands

Secrete substances through ducts (basically tubes). These substances can be water, enzymes, and mucus.

Amino Acid-Based Hormones

Hormones made of amino acids. They can be a single modified amino acido or a protein made up of 3-200 amino acids. They are usually water soluble.

Steroid Hormones

Lipid hormones that are made from cholesterol by the body. They are also fat soluble.

Target Cells

Specific cells that hormones travel to, to produce a specific effect.

Receptors

Proteins that bind to specific signal molecules that cause the cell to respond.

Second Messenger

A molecule that causes changes inside a cell in response to the binding of a specific substance to a receptor on the outside of a cell. Cyclic AMP is a common second messenger. ATP is converted to make cAMP.

Neuropeptides

Hormones secreted by the nervous system. Unlike neurotransmitters, they tend to affect many cells near the nerve cells that release them.

Prostaglandins

Modified fatty acids that are secreted by most cells. They accumulate in areas where tissues are disturbed or injured. Some reduce blood pressure, and others raise blood pressure. Some cause smooth muscles to contract while still others cause smooth muscles to relax. Some even cause fever. Aspirin and acetaminophen reduce fever and decrease pain by inhibiting prostaglandin synthesis.

Endorphins

A group of neuropeptides that regulate emotions, influence pain, and affect reproduction.

Enkephalins

A group of neuropeptides that inhibits pain messages traveling towards the brain.

Hypothalamus

The area of the brain that coordinates many activities of the nervous and endocrine systems. It receives information from other brain regions and then responds to these signals as well as to blood concentrations of circulating hormones.

Pituitary Gland

It is suspended from the hypothalamus by a short stalk. The hypothalamus produces hormones that are stored in this gland or that regulate this gland's activity.

Neurosecretory Cells

Nerve cells that secrete hormones. The axons of these cells in the hypothalamus extend into the posterior lobe of the pituitary. Oxytocin and ADH are transported through these axons into the posterior pituitary where they are stored for eventual release into the bloodstream.

Releasing Hormone

Stimulate the anterior pituitary to make and secrete hormones.

Release-Inhibiting Hormone

These inhibit production and secretion of anterior-pituitary hormones.

Thyroid Gland

Located near the lower part of the larynx, this endocrine gland secretes the hormones thyroxine and triiodothyronine. Both of these hormones are derived from the same amino acid and are synthesized with iodine atoms. Thyroid-stimulating hormones (TSH) regulates the release of the thyroid hormones. Release of TSH from the anterior pituitary gland is regulated by the hypothalamus. The thyroid gland is important because it promotes human development because it produces calcitonin which stimulates the transfer of calcium ions from the blood to the bone. The thyroid hormones help maintain normal heart rate, blood pressure and body temperature. They also stimulate enzymes that are associated with glucose oxidation, oxygen consumption, generating heat, and increasing cellular metabolic rates. Lastly, they promote carbohydrate usage over fat usage for energy.

Hypothyroidism

When there is a deficiency in thyroid hormones. Symptoms of this include: growth retardation, lethargy, weight gain, and low heart rate and body temperature. It can also cause cretinism, a form of mental retardation.

Hyperthyroidism

Abnormal thyroid overactivity can be detrimental to the body's metabolism. Overproduction of the thyroid hormones has some symptoms, such as: overactivity, weight loss, and high blood pressure, and heart rate, and body temperature. It can be treated with medication or by surgically removing part of the thyroid gland.

Adrenal Gland

One of these is located over each kidney and each has an inner core, the medulla and the outer layer, the cortex. The medulla and cortex function as separate endocrine glands. Secretion of hormones in the medulla is controlled by the nervous system while hormones in the anterior pituitary regulate secretion of hormones in the cortex. The cortex responds specifically to adrenocorticotropic hormone (ACTH), which is secreted by the anterior pituitary gland.

Epinephirine & Norepinephrine

These amino acid-based hormones produced in the adrenal medulla are also known as adrenaline and noradrenaline. These hormones work together to orchestrate the nervous system's reaction to stress and its "fight-or-flight" reaction response to danger. When a person is stressed the medulla secretes both hormones into the bloodstream. They increase heart rate, blood pressure, blood glucose level, and blood flow to the heart and lungs. They also stimulate enlargement of the bronchial tubes and dilation of the pupils.

Cortisol

Promotes the production of glucose from proteins making usable energy available to cells.

Gonads

The ovaries in females, and the testes in males. These are gamete-producing organs that also produce a group of steroid sex hormones. Sex hormones regulate body changes that begin at puberty.

Puberty

The adolescent stage during which the sex organs mature and secondary sex characteristics, such as facial hair appear. In males, during this stage, sperm production begins, the voice deepens, the chest broadens, and hair begins to grow on the body and face. In females, the menstrual cycle begins, the breasts grow, and the hips wide.

Luteinizing Hormone (LH)

A hormone secreted by the anterior pituitary stimulates secretion of sex hormones from the gonads. It stimulates the secretion of estrogen and progesterone in females. In males it stimulates the testes to secrete a group of sex hormones called androgens. An example of an androgen is testosterone.

Follicle-Stimulating Hormone (FSH)

A hormone secreted by the anterior pituitary stimulates secretion of sex hormones from the gonads. It stimulates the secretion of estrogen and progesterone in females.

Estrogen & Progesterone

These sex hormones are stimulated to be produced by LH and FSH in females. In preparation for a possible pregnancy, these sex hormones cause the monthly release of an egg by an ovary and buildup of the uterine lining. Estrogen also regulates female secondary sex characteristics.

Androgens

A group of sex hormones secreted by the testes.

Testosterone

An androgen secreted by the testes that regulates male secondary sex characteristics. It also, along with FSH, stimulates sperm production.

Pancreas

It mostly contains exocrine cells, but specialized cells in the pancreas call the islets of Langerhans, function as an endocrine gland.

Islets of Langerhans

Specialized cells in the pancreas that act as an endocrine gland. They secrete two amino acid-based hormones that regulate the level of sugar in the blood. The hormones are insulin and glucagon.

Insulin

An amino acid-based hormone that regulates the level of sugar in the blood. It does this by stimulating body cells, especially muscles, to store glucose or use it for energy. It is secreted by the pancreas.

Glucagon

An amino acid-based hormone that stimulates the release of glucose into the bloodstream by liver cells.

Diabetes Mellitus

It is caused by insulin deficiency in the body. This condition means that cell are unable to obtain glucose, resulting in abnormally high blood glucose readings.

Hypoglycemia

Excessive insulin causes this, a disorder that causes glucose to be stored rather than used and properly delivered to body cells. This leads to lowered blood glucose concentrations and subsequent release of glucagon and epinephrine. Symptoms include lethargy, dizziness, nervousness, overactivity, and in extreme cases, unconsciousness and death.

Thymus Gland

It is located beneath the sternum and between the lungs. It plays a role in the development of the immune system. This gland secretes thymosin.

Thymosin

This is an amino acid-based hormone that is secreted by the thymus gland. The hormone stimulates the maturation of T cells, which help defend the body from pathogens.

Pineal Gland

This gland is located near the base of the brain and it secretes melatonin.

Melatonin

This hormone is secreted by the pineal gland and probably helps regulate sleep patterns.

Parathyroid Glands

There are four of these glands on the back of the thyroid gland and they secrete parathyroid hormone. This stimulates the transfer of calcium ions from the bones to the blood. It has the opposite effect of calcitonin. A proper balance of calcium ions is necessary for cell division, muscle contraction, blood clotting, and neural signaling.

Digestive Cells

Endocrine cells within the walls of some digestive organs also secrete a variety of hormones that control digestive processes. Some examples of these hormones include gastrin and secretin.

Gastrin

A hormone secreted by digestive cells that stimulates other stomach cells to release digestive enzymes such as hydrochloric acid.

Secretin

Released by endocrine cells in the small intestine, a hormone that stimulates the release of various digestive fluids from the pancreas.

Negative Feedback

One way to maintain homeostasis inside an organism or cell, is a negative feedback loop. In this process the final step in a series of events inhibits the initial signal in the series.

Positive Feedback

Another way to maintain homeostasis is a positive feedback loop. In this process, release of an initial hormone stimulates release or production of other hormones or substances which stimulate further release of the initial hormone.

Antagonistic Hormones

Many hormones work together in pairs to regulate the level of critical substances. These hormones have opposite effects.

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