unit 8 - the endocrine system

Define hormone, and describe how they are chemically classified.

A regulatory substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action.

Describe the effects of two groups of hormones produced by the thyroid gland.

Amino Acid Based: How most hormones are classified, water soluble, amines peptides and proteins. Steroids: Synthesized from cholesterol, lipid soluble, gonadals and adrenocorticals.

Indicate the general functions of parathyroid hormone.

Controls calcium balance in the blood.

Describe the three types of interactions of hormones acting on their target cell.

Differentiate among the interactions (permissiveness, antagonism, and synergy) of hormones at target cell

Compare and contrast two of the pancreatic hormones.

Exocrine glands - contain ducts that secrete products of the gland onto an epithelial surface. Secretions have extracellular effects, such as digestion - Endocrine glands - ductless glands that release secretions into bloodstream. Secretions have intracellular effect, alter metabolism of target cell

Describe the relationship between the hypothalamus and the pituitary gland.

The hypothalamus is a region of the brain that controls an immense number of bodily functions. It is located in the middle of the base of the brain. The pituitary gland is a roundish organ that lies immediately beneath the hypothalamus, resting in a depression of the base of the skull called the sella turcica.

What are some of the major differences in how the nervous system controls the body, and how the endocrine system controls the body?

The main difference between these two systems is that the nervous system co-ordinates the body through electrical impulses whereas the endocrine system also co-ordinates bodily functions but is composed of glands that excrete hormones. The nervous system controls muscle movement, senses, heartbeat, breathing, digestion, memory and speech whilst the endocrine system controls levels of glucose in the blood, hydration levels, heat productivity, sexual maturity, sperm and egg production and growth of cells and tissues.

List the major organs of the endocrine system, and give their location and function.

The major glands of the endocrine system are the hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal body, and the reproductive organs (ovaries and testes). The pancreas is also a part of this system; it has a role in hormone production as well as in digestion.

Describe the functions of the hormones of the testes and ovaries.

The ovaries contain and nurture the female's lifetime complement of ova. Feminizing features of puberty result from estrogen produced by the granulosa cells, and androgen hormones from the medulla. The thecal cells produce androstenedione used as a precusor for estrogen production.

Explain how hormone release is regulated.

The synthesis and release of most hormones are regulated by some type of negative feedback mechanism. Some internal or external stimulus triggers hormone secretion. As levels of hormones rise, it causes target organ effects, which then feedback to inhibit further hormone release. As a result, blood levels of many hormones vary only within a narrow range

Cite the physiological effects of hormones produced by the adrenal gland.

Thyroid hormones enter cells through membrane transporter proteins. A number of plasma membrane transporters have been identified, some of which require ATP hydrolysis; the relative importance of different carrier systems is not yet clear and may differ among tissues.

target cell

a cell that bears receptors for a hormone, drug, or other signaling molecule, or is the focus of contact by a virus, phagocyte, nerve fiber, etc.

ovary

a female reproductive organ in which ova or eggs are produced, present in humans and other vertebrates as a pair

thyroid gland

a large cartilage of the larynx, a projection of which forms the Adam's apple in humans

pancreas

a large gland behind the stomach that secretes digestive enzymes into the duodenum. Embedded in the pancreas are the islets of Langerhans, which secrete into the blood the hormones insulin and glucagon

thymus

a lymphoid organ situated in the neck of vertebrates that produces T cells for the immune system. The human thymus becomes much smaller at the approach of puberty

pineal gland

a pea-sized conical mass of tissue behind the third ventricle of the brain, secreting a hormonelike substance in some mammals

hypothalamus

a region of the forebrain below the thalamus that coordinates both the autonomic nervous system and the activity of the pituitary, controlling body temperature, thirst, hunger, and other homeostatic systems, and involved in sleep and emotional activity

endocrine system

collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things

adrenal gland

endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol

endocrine glands

glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct

parathyroid gland

mall endocrine glands in the neck of humans and other tetrapods that produce parathyroid hormone

eicosanoid

prostaglandins and related compounds

up-regulation

the complementary process that involves increases of such components

humoral stimuli

the control of hormone release in response to changes in extracellular fluids

pituitary gland

the major endocrine gland. A pea-sized body attached to the base of the brain, the pituitary is important in controlling growth and development and the functioning of the other endocrine glands

neural stimuli

the nervous system directly stimulates endocrine glands to release hormones

down-regulation

the process by which a cell decreases the quantity of a cellular component, such as RNA or protein, in response to an external variable

hormonal stimuli

the release of a hormone in response to another hormone

testis

an organ that produces spermatozoa (male reproductive cells)

steroid

an organic compound with four rings arranged in a specific configuration

hormones

any member of a class of signaling molecules produced by glands in multicellular organisms that are transported by the circulatory system to target distant organs to regulate physiology and behaviour