A&P II- Chap 1

Hormone

A chemical messenger secreted by an endocrine gland that enters the bloodstream and travels to target cells to produce an effect.

Endocrine system

A system responsible for long-term regulation through hormones, in contrast to the nervous system which regulates short-term.

Paracrines

Hormones that act on neighboring cells.

Autocrines

Hormones that act on the same cells that secrete them.

Lipid soluble hormones

Hormones that pass through target cell membranes and bind to receptors inside the cell, regulating gene expression.

Water soluble hormones

Hormones that cannot cross the target cell’s plasma membrane and bind to surface receptors on target cells.

1st messenger

The hormone that binds to a surface receptor on a target cell in the mechanism of water soluble hormones.

2nd messenger

A molecule like cAMP that transmits the signal inside the target cell after the hormone binds to the receptor.

Permissive effect

When one hormone enhances the effect of another hormone.

Synergistic effect

When two hormones together have a greater effect at the target cell than the sum of their individual effects.

Antagonistic effect

When one hormone opposes the effect of another hormone.

Human Growth Hormone (hGH)

Hormone that stimulates the liver, skeletal muscle, and bones to secrete insulin-like growth factors (IGFs).

Thyroid stimulating hormone (TSH)

Hormone that stimulates the thyroid to secrete T3 and T4.

Oxytocin (OT)

Hormone that stimulates milk ejection during lactation and uterine contractions during labor.

Antidiuretic hormone (ADH)

Hormone that increases water reabsorption in the kidneys and helps regulate blood pressure.

Calcitonin

Hormone produced by the thyroid that lowers blood calcium levels by inhibiting osteoclast activity.

Parathyroid hormone (PTH)

Hormone that increases blood calcium levels by acting on bones, kidneys, and small intestine.

Glucagon

Hormone secreted by alpha cells of the pancreas that raises blood glucose levels by stimulating glycogen breakdown.

Insulin

Hormone secreted by beta cells of the pancreas that lowers blood glucose levels by facilitating glucose transport into cells.

Estrogens and progesterone

Hormones secreted by ovaries that regulate follicular development and prepare the uterus for implantation.

Androgens (testosterone)

Hormones secreted by testes that regulate sperm production and male sex characteristics.

Melatonin

Hormone secreted by the pineal gland that regulates diurnal cycles.

Thymosin

Hormone secreted by the thymus that provides immunocompetence to T-lymphocytes.

Exocrine glands

Glands that secrete hormones and other substances through ducts onto surfaces or into cavities, rather than directly into the bloodstream.

Negative feedback loop

A regulatory mechanism in which a change in a physiological variable triggers a response that counteracts the initial change, maintaining homeostasis.

Positive feedback loop

A process in which a change in a physiological variable leads to an enhancement of that change, often leading to a larger response.

Hormonal signaling

A communication process in which hormones are released into the bloodstream and travel to target organs or tissues, inducing specific biological responses.

Pheromones

Chemical signals released by an individual to communicate with and influence the behavior of