AP Bio Chapter 45

Hormones and the Endocrine System

epinephrine

catecholamine that, when secreted as a hormone by the adrenal medulla, mediates “fight-orflight” responses to short-term stresses; also released by some neurons as a neurotransmitter; also called adrenaline.

oxytocin

A hormone produced by the hypothalamus and released from the posterior pituitary. It induces contractions of the uterine muscles during labor and causes the mammary glands to eject milk during nursing.

mineralocorticoid

A steroid hormone secreted by the adrenal cortex that regulates salt and water homeostasis.

antidiuretic hormone (ADH)

vasopressin; regulates water balance in the body by increasing water reabsorption in the kidneys.

positive feedback

A form of regulation in which an end product of a process speeds up that process; in physiology, a control mechanism in which a change in a variable triggers a response that reinforces or amplifies the change.

estrogen

Any steroid hormone, such as estradiol, that stimulates the development and maintenance of the female reproductive system and secondary sex characteristics.

hormone

In multicellular organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the organism, changing the target cells' functioning.

thyroxine (T4)

One of two iodine-containing hormones that are secreted by the thyroid gland and that help regulate metabolism, development, and maturation in vertebrates.

adrenal gland

One of two endocrine glands located adjacent to the kidneys in mammals. Endocrine cells in the outer portion (cortex) respond to adrenocorticotropic hormone (ACTH) by secreting steroid hormones that help maintain homeostasis during long-term stress. Neurosecretory cells in the central portion (medulla) secrete epinephrine and norepinephrine in response to nerve signals triggered by short-term stress.

estradiol

A steroid hormone that stimulates the development and maintenance of the female reproductive system and secondary sex characteristics; the major estrogen in mammals.

pheromone

In animals and fungi, a small molecule released into the environment that functions in communication between members of the same species. In animals, it acts much like a hormone in influencing physiology and behavior.

melatonin

A hormone that is secreted by the pineal gland and that is involved in the regulation of biological rhythms and sleep.

prolactin

A hormone produced and secreted by the anterior pituitary with a great diversity of effects in different vertebrate species. In mammals, it stimulates growth of and milk production by the mammary glands.

pituitary gland

An endocrine gland at the base of the hypothalamus; consists of a posterior lobe, which stores and releases two hormones produced by the hypothalamus, and an anterior lobe, which produces and secretes many hormones that regulate diverse body functions.

paracrine

Referring to a secreted molecule that acts on a neighboring cell.

local regulator

A secreted molecule that influences cells near where it is secreted.

thyroid gland

An endocrine gland, located on the ventral surface of the trachea, that secretes two iodine-containing hormones, triiodothyronine (T3) and thyroxine (T4), as well as calcitonin.

prostaglandin

One of a group of modified fatty acids that are secreted by virtually all tissues and that perform a wide variety of functions as local regulators.

parathyroid hormone (PTH)

A hormone secreted by the parathyroid glands that raises blood calcium level by promoting calcium release from bone and calcium retention by the kidneys.

nitric oxide (NO)

gas produced by many types of cells that functions as a local regulator and as a neurotransmitter.

posterior pituitary gland

An extension of the hypothalamus composed of nervous tissue that secretes oxytocin and antidiuretic hormone made in the hypothalamus; a temporary storage site for these hormones.

hypothalamus

The ventral part of the vertebrate forebrain; functions in maintaining homeostasis, especially in coordinating the endocrine and nervous systems; secretes hormones of the posterior pituitary and releasing factors that regulate the anterior pituitary.

androgen

Any steroid hormone, such as testosterone, that stimulates the development and maintenance of the male reproductive system and secondary sex characteristics.

neurotransmitter

A molecule that is released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft, and binds to the postsynaptic cell, triggering a response.

parathyroid gland

One of four small endocrine glands, embedded in the surface of the thyroid gland, that secrete parathyroid hormone.

testosterone

A steroid hormone required for development of the male reproductive system, spermatogenesis, and male secondary sex characteristics; the major androgen in mammals.

neurohormone

A molecule that is secreted by a neuron, travels in body fluids, and acts on specific target cells, changing their functioning.

norepinephrine

A catecholamine that is chemically and functionally similar to epinephrine and acts as a hormone or neurotransmitter; also called noradrenaline.

progesterone

A steroid hormone that contributes to the menstrual cycle and prepares the uterus for pregnancy; the major progestin in mammals.

negative feedback

A form of regulation in which accumulation of an end product of a process slows the process; in physiology, a primary mechanism of homeostasis, whereby a change in a variable triggers a response that counteracts the initial change.

glucocorticoid

A steroid hormone that is secreted by the adrenal cortex and that influences glucose metabolism and immune function.

melanocyte-stimulating hormone (MSH)

A hormone produced and secreted by the anterior pituitary with multiple activities, including regulating the behavior of pigment-containing cells in the skin of some vertebrates.

gonad

A male or female gamete-producing organ.

signal transduction

The linkage of a mechanical, chemical, or electromagnetic stimulus to a specific cellular response.

autocrine

Referring to a secreted molecule that acts on the cell that secreted it.

pineal gland

A small gland on the dorsal surface of the vertebrate forebrain that secretes the hormone melatonin.

calcitonin

A hormone secreted by the thyroid gland that lowers blood calcium levels by promoting calcium deposition in bone and calcium excretion from the kidneys; nonessential in adult humans.

thyroid hormone

Either of two iodine-containing hormones (triiodothyronine and thyroxine) that are secreted by the thyroid gland and that help regulate metabolism, development, and maturation in vertebrates.

growth hormone (GH)

A hormone that is produced and secreted by the anterior pituitary and that has both direct (nontropic) and tropic effects on a wide variety of tissues.

anterior pituitary

A portion of the pituitary gland that develops from nonneural tissue; consists of endocrine cells that synthesize and secrete several tropic and nontropic hormones

progestin

Any steroid hormone with progesterone-like activity.

endocrine system

In animals, the internal system of communication involving hormones, the ductless glands that secrete hormones, and the molecular receptors on or in target cells that respond to hormones; functions in concert with the nervous system to effect internal regulation and maintain homeostasis.

endocrine gland

A ductless gland that secretes hormones directly into the interstitial fluid, from which they diffuse into the bloodstream.