Ch 6Chemical Coordination and Integration — Class 12 Zoology, concept-first.

Coordination in the body is not achieved by the nervous system alone. Nerve-based coordination is quick and point-to-point — a signal travels from one specific place to another almost instantly — but…

Endocrine glands are unusual among glands because they have no ducts — no tubes to carry their product to a particular spot. For this reason they are also called ductless glands.

Taken together, the body's hormone-producing structures make up the endocrine system. This system is not a single organ but a collection of parts scattered through the body — both the discrete endocri…

The hypothalamus sits at the base of the diencephalon in the forebrain. Although it is a region of the brain, it also behaves as an endocrine control centre, and it governs a very wide range of body f…

The pituitary gland lies within a small bony pocket of the skull called the sella tursica and is joined to the hypothalamus above it by a stalk.

The pineal gland is found on the dorsal (upper) side of the forebrain. It secretes a single hormone called melatonin.

The thyroid gland has two lobes, one lying on each side of the windpipe (trachea). The two lobes are joined across the middle by a narrow bridge of connective tissue known as the isthmus, giving the g…

The parathyroid glands are small endocrine glands attached to the thyroid. In humans there are four parathyroid glands, located on the back (dorsal) side of the thyroid gland — one pair embedded in ea…

The thymus is a lobular endocrine gland positioned in the chest. It lies between the two lungs, behind the sternum (breastbone), on the ventral (front) side of the aorta.

The body has one pair of adrenal glands, with one gland sitting above each kidney. Each gland is made of two different kinds of tissue: the adrenal medulla at the centre and the adrenal cortex forming…

The pancreas is a composite gland, meaning it works as both an exocrine and an endocrine gland. Its endocrine part is made up of clusters of cells called the Islets of Langerhans.

The testis is the male gonad, and a pair of them lies in the scrotal sac, which hangs outside the abdominal cavity.

Females carry a pair of ovaries within the abdomen. The ovary is the primary female sex organ, and during each menstrual cycle it releases one ovum.

The organised endocrine glands are not the only sources of hormones in the body. Several tissues that are not endocrine glands in the usual sense also release hormones, and these play important regula…

Hormones act only on their target tissues, and they do so by binding to specific proteins known as hormone receptors, which are present in those target tissues alone.

The body is coordinated not only by the nervous system but also by a set of special chemicals called hormones, which provide chemical coordination, integration and regulation.

Higher-order thinking / exemplar-style practice problems.