12.11.2 The Endocrine System

Question 1

The Endocrine System

Answer 1

• The endocrine system consists of all of an animal’s hormone-secreting cells.
• Endocrine glands are ductless glands that secrete chemicals directly into the bloodstream; exocrine glands secrete chemicals through ducts. The pancreas acts as both an endocrine and an exocrine gland.
• Some major glands of the endocrine system include: the hypothalamus, the thyroid gland, the parathyroid gland, the pancreas, the adrenal glands, the gonads, the pineal gland, the thymus, and the pituitary gland.
• Thyroid hormones are regulated by a negative feedback loop.

Question 2

endocrine system

Answer 2

• The endocrine system consists of many glands that secrete hormones. Endocrine glands are ductless glands that secrete hormones directly into the blood stream.
• The hypothalamus is a region of the brain that releases
  hormones that trigger other endocrine signals.
• The thyroid gland is located in the neck just in front of the trachea. The thyroid gland secretes hormones, such as thyroxine, that are involved in the maintenance of metabolic processes.
• The parathyroid glands are four small glands embedded in the thyroid gland. They function in the homeostasis of calcium in the blood.
• The pancreasis an organ that functions as an exocrine gland by producing digestive enzymes that are delivered to the small intestine. Scattered throughout the pancreas are clusters of endocrine cells called islets of Langerhans. The islets of Langerhans secrete glucagon from alpha cells, and insulin from beta cells. Glucagon and insulin are involved in the regulation of blood sugar levels.

Question 3

adrenal and endocrine glands

Answer 3

• Adrenal glands, located on top of the kidneys, consist of two types of cells found within the adrenal medulla and adrenal cortex. Cells of the adrenal medulla produce epinephrine and norepinephrine, hormones involved in the fight-or-flight response. Cells of the adrenal cortex produce corticosteroids, a group of hormones involved in a variety of functions, including raising blood glucose levels and ion reabsorption in the kidneys.
• Endocrine glands in the male and female gonads include the testes and ovaries, respectively. The testes produce androgens, such as testosterone, that are involved in sperm formation and the maintenance of male sex characteristics. The ovaries produce estrogens and progesterone, which are involved in regulating uterine lining, among other things.
• The pineal glandis a small gland near the center of the brain that secretes melatonin, a hormone involved in circadian rhythms.
• The thymus is an endocrine gland that secretes thymosin, a hormone that is involved in the development of T lymphocytes.

Question 4

pituitary gland

Answer 4

• The pituitary gland is an endocrine gland that consists of two lobes, the anterior and posterior pituitary glands. The hypothalamus is closely associated with both the anterior and posterior pituitary glands.
• Secretory cells of the hypothalamus release hormones,
  including antidiuretic hormone and oxytocin. These
  hormones are released by the posterior pituitary into the
  blood stream.
• The hypothalamus also controls the anterior pituitary with hormones. In response to specific hormonal signals received from the hypothalamus, the anterior pituitary will release any of a variety of hormones including FSH, LH, TSH, and ACTH.

Question 5

THS-releasing hormone

Answer 5

• Thyroid hormones are controlled in a negative feedback loop, depicted in the diagram to the left.
• The hypothalamus secretes TSH-releasing hormone (TRH). TRH stimulates the anterior pituitary gland to produce thyroid-stimulating hormone (TSH). TSH stimulates the thyroid to produce T3 and T4, which are involved in the maintenance of metabolism.
• High levels of T3 and T4 and TSH inhibit TRH production by the hypothalamus, eventually resulting in the reduction of T3 and T4

Question 6

Which of the following is produced by the thymus?

Answer 6

• thymosin

Question 7

The butterfly-shaped gland located in the neck is the _____________ gland.

Answer 7

• thyroid

Question 8

The adrenal medulla produces which of the following hormones?

Answer 8

• Epinephrine

Question 9

Where is the pituitary gland located?

Answer 9

• the brain

Question 10

Which of the following is not a characteristic of endocrine glands?

Answer 10

• located exclusively in the digestive system

Question 11

A tropic hormone

Answer 11

• stimulates other glands in the body.

Question 12

Which of the following endocrine glands produces the hormone melatonin?

Answer 12

• pineal

Question 13

Islets of Langerhans in the pancreas release the two hormones, __________ and __________, which are antagonistic hormones that regulate blood sugar levels.

Answer 13

• glucagon; insulin

Question 14

Oxytocin is produced in the anterior lobe of the pituitary gland.

Answer 14

• false

Question 15

Type I diabetes is a disease in which the body can no longer produce the hormone insulin to lower blood glucose levels. Which endocrine gland is dysfunctional in this disease?

Answer 15

• pancreas

Question 16

Which of the following is not produced by the anterior pituitary?

Answer 16

• ADH

Question 17

The function of the hypothalmus is

Answer 17

• to integrate the endocrine and nervous systems

Question 18

ADH and oxytocin are hormones secreted from which lobe of the pituitary gland?

Answer 18

• posterior

Question 19

Which of the following is not an example of an exocrine gland?

Answer 19

• Thyroid

Question 20

Which of the following is not a response to stress?

Answer 20

• Decreased metabolic rate