The Mind's Machine: Chapter 8

Allomone

A chemical signal that is released outside the body by one species and affects the behavior of other species. See Figure 8.3. Compare pheromone.

amine hormone

Also called monoamine hormone. A hormone composed of a single amino acid that has been modified into a related molecule, such as melatonin or epinephrine. Compare peptide hormone and steroid hormone.

Androgen

Any of a class of hormones that includes testosterone and other male hormones. See Figure 8.13.

anterior pituitary

The front division of the pituitary gland. It secretes tropic hormones. See Figures 8.1, 8.12. Compare posterior pituitary.

Autoradiography

A staining technique that shows the distribution of radioactive chemicals in tissues. See Boxes 2.1, 8.1.

Castration

Removal of the gonads, usually the testes.

cloacal exstrophy

A rare medical condition in which XY individuals are born completely lacking a penis.

corpus luteum (pl. corpora lutea)

The structure that forms from the collapsed ovarian follicle after ovulation. The corpora lutea are a major source of progesterone.

endocrine gland

A gland that secretes hormones into the bloodstream to act on distant targets. See Figure 8.1.

Endocrine

Referring to glands that release chemicals to the interior of the body. These glands secrete the principal hormones used by the body. See Figure 8.3.

Estradiol

The primary type of estrogen that is secreted by the ovary. Its formal name is 17-beta-estradiol.

Estrogen

Any of a class of steroid hormones, including estradiol, produced by female gonads. See Figure 8.13.

follicle-stimulating hormone (FSH)

A gonadotropin, named for its actions on ovarian follicles. See Figure 8.13.

Follicle

The structure of the ovary that contains an immature ovum (egg).

Gonad

Any of the sexual organs (ovaries in females, testes in males) that produce gametes for reproduction. See Figure 8.1.

gonadotropin-releasing hormone (GnRH)

A hypothalamic hormone that controls the release of luteinizing hormone and follicle-stimulating hormone from the pituitary. See Figure 8.13.

Gonadotropin

An anterior pituitary hormone that selectively stimulates the cells of the gonads to produce sex steroids and gametes. See luteinizing hormone and follicle-stimulating hormone.

growth hormone (GH)

Also called somatotropin or somatotropic hormone. A tropic hormone, secreted by the anterior pituitary, that promotes the growth of cells and tissues.

Hormone

A chemical, usually secreted by an endocrine gland, that is conveyed by the bloodstream and regulates target organs or tissues. See Table 8.1.

hypothalamic-pituitary portal system

An elaborate bed of blood vessels leading from the hypothalamus to the anterior pituitary.

immunocytochemistry (ICC)

A method for detecting a particular protein in tissues in which an antibody recognizes and binds to the protein and then chemical methods are used to leave a visible reaction product around each antibody. See Boxes 2.1, 8.1.

in situ hybridization

A method for detecting particular RNA transcripts in tissue sections by providing a nucleotide probe that is complementary to, and will therefore hybridize with, the transcript of interest. See Boxes 2.1, 8.1; Appendix Figure A.4.

knockout organism

An individual in which a particular gene has been disabled by an experimenter. See Box 8.1.

luteinizing hormone (LH)

A gonadotropin, named for its stimulatory effects on the ovarian corpora lutea. See Figure 8.13.

median eminence

A midline feature on the base of the brain that marks the point at which the pituitary stalk exits the hypothalamus to connect to the pituitary. The median eminence contains elements of the hypothalamic-pituitary portal system. See Figure 8.12.

milk letdown reflex

The reflexive release of milk by the mammary glands of a nursing female in response to suckling or to stimuli associated with suckling. See Figure 8.9.

negative feedback

The property by which some of the output of a system feeds back to reduce the effect of input signals.

neuroendocrine cell

A neuron that releases hormones into local or systemic circulation.

oral contraceptive

A birth control pill, typically consisting of steroid hormones to prevent ovulation.

Ovaries

The female gonads, which produce eggs (ova) for reproduction. See Figure 8.1. Compare testes.

ovulatory cycle

The periodic occurrence of ovulation in females. See Figure 8.19.

Oxytocin

A hormone, released from the posterior pituitary, that triggers milk letdown in the nursing female but is also associated with a variety of complex behaviors. See Figures 8.8, 8.9.

pair-bond

A durable and exclusive relationship between two individuals.

peptide hormone

Also called protein hormone. A hormone that consists of a string of amino acids.

Pheromone

A chemical signal that is released outside the body of an animal and affects other members of the same species. See Figure 8.3. Compare allomone.

pituitary gland

A small, complex endocrine gland located in a socket at the base of the skull. See Figures 2.16, 8.8, 8.12.

pituitary stalk

Also called infundibulum. A thin piece of tissue that connects the pituitary gland to the hypothalamus.

posterior pituitary

The rear division of the pituitary gland. See Figures 8.1, 8.8. Compare anterior pituitary.

Progesterone

The primary type of progestin secreted by the ovary. See Figure 8.13.

Progestin

Any of a major class of steroid hormones that are produced by the ovary, including progesterone. See Figure 8.13.

releasing hormone

Any of a class of hormones, produced in the hypothalamus, that traverse the hypothalamic-pituitary portal system to control the pituitary's release of tropic hormones. See Figure 8.12.

second messenger

A slow-acting substance in a target cell that amplifies the effects of synaptic or hormonal activity and regulates activity within the target cell.

steroid hormone

Any of a class of hormones, each of which is composed of four interconnected rings of carbon atoms. Compare amine hormone and peptide hormone.

Synapse

The cellular location at which information is transmitted from a neuron to another cell. See Figure 2.4.

testes (sing. testis)

The male gonads, which produce sperm and androgenic steroid hormones. See Figure 8.1. Compare ovaries.

Testosterone

A hormone, produced by male gonads, that controls a variety of bodily changes that become visible at puberty. It is one of a class of hormones called androgens. See Figure 8.13.

tropic hormone

Any of a class of anterior pituitary hormones that affect the secretion of hormones by other endocrine glands. See Figure 8.12.

Vasopressin

Also called arginine vasopressin or antidiuretic hormone. A peptide hormone from the posterior pituitary that promotes water conservation and increases blood pressure.