Chapter 12 - Endocrine System

Question 1

Endocrine system, endocrine glands, endocrine hormones, exocrine glands

Answer 1

Theendocrine systemis a system of glands calledendocrine glandsthat release chemical messenger molecules into the bloodstream. The messenger molecules of the endocrine system are called endocrine hormones. Other glands of the body, including sweat glands and salivary glands, also secrete substances but not into the bloodstream. Instead, they secrete them through ducts that carry them to nearby body surfaces. These other glands are not part of the endocrine system. Instead, they are calledexocrine glands.

Question 2

Pituitary gland

Answer 2

• controlled by hypothalamus

*The master gland

*Anterior lobe makes its own hormones

*Posterior lobe stores and secretes hormones made by the hypothalamus

Question 3

Thyroid gland

Answer 3

The thyroid gland is a large gland in the neck. Thyroid hormones such as thyroxine increase the rate of metabolism in cells throughout the body. They control how quickly cells use energy and make proteins.

Question 4

Parathyroid hormones

Answer 4

The four parathyroid glands are located in the neck behind the thyroid gland. Parathyroid hormone helps keep the level of calcium in the blood within a narrow range. It stimulates bone cells to dissolve calcium and release it into the blood.

Question 5

Pineal gland

Answer 5

The pineal gland is a tiny gland located near the center of the brain. It secretes the hormone melatonin, which controls the sleep-wake cycle and several other processes. The production of melatonin is stimulated by darkness and inhibited by light. Cells in the retina of the eye detect light and send signals to a structure in the brain named the suprachiasmatic nucleus (SCN). Nerve fibers carry the signals from the SCN to the pineal gland via the autonomic nervous system.

Question 6

Panreas

Answer 6

The pancreas is located near the stomach. Its endocrine hormones include insulin and glucagon, which work together to control the level of glucose in the blood. The pancreas also secretes digestive enzymes into the small intestine.

Question 7

Adrenal glands

Answer 7

The two adrenal glands are located above the kidneys. Adrenal glands secrete several different endocrine hormones, including the hormone adrenaline, which is involved in the fight-or-flight response. Other endocrine hormones secreted by the adrenal glands have a variety of functions. For example, the hormone aldosterone helps to regulate the balance of minerals in the body. The hormone cortisol, which causes Cushing’s syndrome when it is produced in excess, is also an adrenal gland hormone.

Question 8

Gonads

Answer 8

The gonads include the ovaries in females and testes in males. They secrete sex hormones, such as testosterone (in males) and estrogen (in females). These hormones control sexual maturation during puberty and the production of gametes (sperm or egg cells) by the gonads after sexual maturation.

Question 9

Thymus

Answer 9

The thymus gland is located in front of the heart. It is the site where immune system cells called T cells mature. T cells are critical to the adaptive immune system, in which the body adapts to specific pathogens.

Question 10

hypersecretion

Answer 10

When too much hormone is secreted, the condition is calledhypersecretion.

Question 11

Hyposecretion

Answer 11

When not enough hormone is secreted, the condition is calledhyposecretion.

Question 12

Hormones

Answer 12

Endocrine hormoneslike estrogen are messenger molecules that are secreted by endocrine glands into the bloodstream. They travel throughout the body in the circulation.

Question 13

Target cell

Answer 13

Atarget cellis the type of cell on which a hormone has an effect. A target cell is affected by a particular hormone because it has receptor proteins—either on the cell surface or within the cell— that are specific to that hormone. An endocrine hormone travels through the bloodstream until it finds a target cell with a matching receptor to which it can bind. When the hormone binds to the receptor, it causes changes within the cell.

Question 14

WHat regulates the secretion of hormones?

Answer 14

Most endocrine hormones are regulated by negative feedback loops. Negative feedback keeps the concentration of a hormone within a relatively narrow range and maintains homeostasis.

Very few endocrine hormones are regulated by positive feedback loops. Positive feedback causes the concentration of a hormone to become increasingly higher.

Question 15

Negative feedback: Hypothalamus and endocrine system

Answer 15

*Thyroid levels get low
*Hypothalamus notices and relseases TRH to Pituitary gland
*Pituitary gland is stimulated and releases TSH to Thyroid gland
*Thyroid gland is stimulated and sends Thyroid hormones to stop hypothalamus.

Question 16

Example of an endocrine positive feedback loop:

Answer 16

Only a few endocrine hormones are controlled by positive feedback loops in which rising levels of a hormone feed back to stimulate continued production of the hormone. Prolactin, the pituitary hormone that stimulates milk production by mammary glands, is controlled by a positive feedback loop. The loop includes the nipples, hypothalamus, pituitary gland, and mammary glands.

Question 17

Vasopressin

Answer 17

Vasopressin (also called antidiuretic hormone, or ADH) helps to maintain homeostasis in body water. It stimulates the kidneys to conserve water by producing more concentrated urine. Specifically, vasopressin targets ducts in the kidneys and makes them more permeable to water. This allows more water to be resorbed by the body rather than excreted in urine.

Question 18

Oxytocin

Answer 18

Oxytocin (OXY) targets cells in the uterus to stimulate uterine contractions, for example, during childbirth. It also targets cells in the breasts of a nursing mother to stimulate the letdown of milk.