Chapter 16--Endocrine System

The hypothalamus communiates with the ________________________ via the hypothalamic-hypophyseal portal system.

1) anterior pituitary

What are the 3 zones of the adrenal cortex that secrete steroid hormones?

1) zona glomeris 2) zona fascinata 3) zona reticularis

Hormone

Chemical messengers secreted into the bloodstream by endocrine glands that initiate a change in a target cell.

Adrenal medulla secretes _______________ and ____________.

Epinephrine and norepinephrine

Ovaries

Female reproductive organs that produce estrogens and progesterone.

Thymus gland

Gland located in the superior mediastinum; largest and most active during infancy and childhood when it is actively secreting thymosin and thypopoietin.

Pineal Gland secretes ____________.

melatonin

Testes

Male reproductive organs that produce testosterone.

Pineal gland

Small gland located in the posterior/superior diencephalon; secretes melatonin in response to decreased light levels

Adrenal cortex

Superficial region of the adrenal gland; consists of glandular tissue that secretes steroid hormones.

A hormone is best describes as a ______________.

chemical released into the bloodstream that typically acts on distant targets.

In a negative feedback loop, you would expect secretion from an endocrine gland to ______________ after homeostasis has been restored.

decrease

Negative feedback

A mechanism in which a deviation in a physiological variable triggers a response that restores the variable to its set point; when the set point is restored, the response decreases.

A pheochromocytoma (fee-uh-kroh-muh-sy-TOH-muh) is a tumor of the adrenal medulla that secretes epinephrine and norepinephrine. Predict the symptoms that you might see from this condition.

A pheochromocytoma leads to excessive sympathetic nervous system stimulation, which causes symptoms such as an elevated heart rate and blood pressure.

Anterior Pituitary

Anterior portion of the pituitary gland; secretes hormones that largely affect other glands.

Hypothalamus produces __________________ and ___________________.

Anti-diuretic hormone and oxytocin

Endocrine gland

Any of several diverse ductless glands that play a major role in maintaining the body's homeostasis through the secretion of hormones into the bloodstream.

Pancreas

Endocrine and exocrine gland that secretes insulin and glucagon from pancreatic islets

Tumors of the parathyroid gland often result in secretion of excess parathyroid hormone. Considering the function of this hormone, predict the effects of such a tumor. How would the effects change if the tumor secreted calcitonin instead?

Excess parathyroid hormone results in hypercalcemia and weakened bones, which leads to bone fractures. The hypercalcemia affects skeletal muscles, the heart, and neurons. If the tumor secreted calcitonin, it would increase bone deposition and could result in hypocalcemia, which primarily affects the nervous system.

Thyroid gland

Gland located in the anteroinferior neck; composed of thyroid follicles that produce thyroid hormone and calcitonin.

A type of tumor in the pancreas called a glucagonoma produces and releases excess glucagon into the blood. How would this affect the level of glucose in the blood? Would the overall effect on blood glucose differ from that of type I diabetes mellitus? Why or why not?

Glucagon increases blood glucose through gluconeogenesis and glycogenolysis. When excess glucagon is secreted, it causes hyperglycemia, just as we see with diabetes mellitus, because the cells are only able to take in so much of the extra glucose that has been released. The remaining glucose stays in the blood, causing hyperglycemia.

In the condition hyperthyroidism, patients have elevated levels of both T3 and T4 due to a malfunction of the immune system that causes the thyroid gland to overproduce thyroid hormones. Do you think the negative feedback loops would lead to high levels of TSH or low levels of TSH? Explain.

Hyperthyroidism leads to a low level of TSH. The elevated levels of T3 and T4 cause feedback inhibition to the hypothalamus and anterior pituitary, which decreases TSH production. This is the body's attempt to lower thyroid stimulation and so lower T3 and T4 levels. The reason it doesn't work is because it is the malfunctioning immune system, not TSH, that is causing the thyroid gland to overproduce thyroid hormones.

Which set of hormones are antagonists?

Insulin and glucagon

Posterior Pituitary

Posterior portion of the pituitary gland; stores ADH and oxytocin produced by the hypothalamus.

In case 3 of Exercise 16-4 (p. 437), we saw that Professor Purple had insufficient antidiuretic hormone (ADH). However, the opposite condition can also occur in which excess ADH is present, called syndrome of inappropriate ADH secretion. Predict the symptoms of this condition.

Producing excess ADH leads to abnormal water retention from the kidneys. This causes the plasma to become too dilute, leading to symptoms associated with overhydration.

Adrenal medulla

The deep region of the adrenal gland that consists of modified sympathetic neurons that secrete epinephrine and norepinephrine in response to sympathetic stimulation.

How does the way in which the hypothalamus communicates with the anterior and posterior pituitary glands differ? How does this reflect the functional differences of the anterior and posterior pituitary glands?

The hypothalamus secretes releasing and inhibiting hormones into capillaries, which travel to the anterior pituitary through the hypothalamic-hypophyseal portal system. These hormones stimulate or inhibit hormone secretion from the anterior pituitary. This reflects the fact that the anterior pituitary is an actual gland that manufactures its own hormones. Hypothalamic axons travel through the infundibulum to the posterior pituitary where axon terminals reside. This reflects the fact that the posterior pituitary is neural tissue that doesn't make its own hormones, and instead stores hypothalamic hormones in the axon terminals.

Hypothalamus

The inferior portion of the diencephalon; releases hormones that stimulate or inhibit the anterior pituitary and two hormones (ADH and oxytocin) stored in the posterior pituitary.

The disease diabetes mellitus is due to either destruction of the cells that produce insulin or a decrease in sensitivity of target cells to circulating insulin. How would this affect the level of glucose in the blood? Why?

This increases the level of glucose in the blood, because normally insulin would cause glucose uptake into cells. Without insulin to trigger glucose uptake, the glucose remains in the blood, causing hyperglycemia.

Parathyroid glands

Three to five small glands located on the posterior thyroid gland; secrete parathyroid hormones that maintain calcium ion homeostasis.

Thyroid gland secretes ________________, __________________, __________________.

Thyroxine, triidothyronine, and calcitonin

Target tissue

Tissue that contains the cells with receptors for a particular hormone.

Cortisol is the adrenal hormone responsible for the stress response.

True

Insulin triggers action that lower the concentraion of glucose in the blood.

True

Interstitial cells within the testes produce testosterone.

True

Parathyroid hormone triggers actions that raise the concentration of calcium ions in the blood.

True

The posterior pituitary produces no hormones of its own.

True

Antieror pituitary secretes ____________________ and _______________.

human growth hormone and thyroid-stimulating hormone

Hypothalamus secretes ________________ and _________________ hormones.

inhibiting and releasing

Adrenal cortex secretes _________________ and ________________.

Aldosterone and cortisol

Thymus secretes _____________ and _________________.

Thymosin and thymopoietin

Pancreas secretes _______________ and ____________________.

Insulin and glucagon