Chapter 2: Chemical Messengers

Question 1

What is an exocrine gland?

Answer 1

Glands that secrete into a duct that carries the secretion to the surface of the body or to one of the body cavities.

Question 2

What are some examples of exocrine glands?

Answer 2

• sweat glands
• salivary glands
• mucous glands

Question 3

What are endocrine glands?

Answer 3

Glands that secrete hormones into the extracellular fluid that surrounds the cells that make up the gland. The secretion usually then passes into the capillaries to be transported by the blood.

Question 4

What are some examples of endocrine glands?

Answer 4

• pituitary
• thymus
• thyroid

Question 5

What is a hormone?

Answer 5

The secretion of an endocrine gland

Question 6

What is a target cell?

Answer 6

A cell whose activity in affected by a particular hormone.

Question 7

What is a target organ?

Answer 7

An organ whose activity is affected by a particular hormone.

Question 8

What is a paracrine?

Answer 8

Any chemical secreted by a cell that diffuses to and affects adjacent cells, also called a local hormone

Question 9

What are the characteristics of protein and amine hormones?

Answer 9

• water soluble

- receptor outside and secondary messenger

Question 10

How do protein and amine hormones work?

Answer 10

1. Hormone attaches to the corresponding receptor protein in the membrane of the target cell.
2. This combination causes a secondary messenger substance to diffuse through the cell and activate particular enzymes.

Question 11

What are the characteristics of steroid hormones?

Answer 11

• lipid soluble

- crosses membrane, attaches to receptor inside

Question 12

What is enzyme amplification?

Answer 12

The process in which one hormone molecule causes the manufacture or activation of thousands of enzymes

Question 13

What occurs once the hormone has produced the required effect?

Answer 13

It must be turned off. The hormone molecules are broken down in the target cells, or mostly liver and kidneys and are then excreted in bile or urine.

Question 14

What is a negative feedback system?

Answer 14

Where the response produced by the hormone is opposite of the stimulus that caused the secretion.

Question 15

What are releasing factors?

Answer 15

Hormones secreted by the hypothalamus that stimulate the release of a hormone

Question 16

What are inhibiting factors?

Answer 16

Hormones released by the hypothalamus that slow down the release of a hormone.

Question 17

Why is the pituitary gland known as the master gland?

Answer 17

Because many pituitary hormones regulate the activity of other endocrine glands

Question 18

The Pineal Gland

Answer 18

Location: deep inside the brain
Hormone: melatonin
Target: all cells
Function: regulates sleep patterns

Question 19

The Thyroid Gland

Answer 19

Location: in the neck below the larynx
Hormone: thyroxin
Target: most cells
Function: increases metabolic rate and therefore oxygen consumption and heat production

Question 20

The Parathyroid Gland

Answer 20

Location: usually 4, embedded in the rear surface of the thyroid
Hormone: parathyroid hormone (PTH)
Target: kidneys, bones, intestines
Function: controls calcium and phosphate levels in the blood

Question 21

The Thymus

Answer 21

Location: in the chest just above the heart and behind the sternum
Hormone: thymosins
Target: T lymphocytes
Function: stimulates development and maturation of T lymphocytes

Question 22

The Adrenal Glands

Answer 22

Location: one above each kidney. Each gland consist of an inner adrenal medulla and outer adrenal cortex

Question 23

The Adrenal Medulla

Answer 23

Hormone: adrenaline, noradrenaline
Target: most tissues
Function: - adrenaline: helps prepare the body doe reaction to a threatening situation, that is, it is concerned with fight-or-flight responses
- noradrenaline: increase the rate and force of the heartbeat

Question 24

The Adrenal Cortex

Answer 24

Hormone: corticosteroids (20), main ones aldosterone and cortisol
Target: kidney, most cells
Function: - aldosterone: increases reabsorption of sodium ions and excretion of potassium ions
- cortisol: promotes normal metabolism, helps the body deal with stress, promotes repair of damaged tissues

Question 25

The Pancreas

Answer 25

Location: just below the stomach and alongside the duodenum Hormone: insulin, glucagon Target: most cells, liver and fat storage tissues Function: - insulin: stimulates uptake of glucose, lowers blood glucose level - glucagon: stimulates break down of glycogen and fat, increases blood glucose level

Question 26

The Testes

Answer 26

Location: male reproductive system Hormone: androgens Target: testes, muscles, bones Function: stimulates sperm production, growth of muscles and skeleton, secondary sexual characteristics

Question 27

The Ovaries

Answer 27

Location: internal female reproductive system Hormone: oestrogen, progesterone Target: uterus, ovaries, breast tissue Function: - oestrogen: stimulate development of secondary sexual characteristics, regulate the menstrual cycle - progesterone: regulates menstrual cycle and pregnancy, prepares mammary glands for milk secretion

Question 28

What are some tissues that are not considered endocrine glands but secrete hormones?

Answer 28

- the stomach and intestines secrete hormones that coordinate the exocrine glands of the digestive system - the heart secrete a hormone that helps reduce blood pressure - the Placenta secretes a number of hormones that help to maintain the pregnancy.

Question 29

What are the hormones secreted by the anterior pituitary?

Answer 29

- FSH - luteinising hormone (LH) - GH - thyroid stimulating hormone (TSH) - andrenocorticotropic hormone (ATCH) - prolactin

Question 30

What hormones are secreted by the posterior pituitary?

Answer 30

- oxytocin | - antidiuretic hormone (ADH)

Question 31

What are some ways in which hormones change the type, activities or quantities of proteins produced?

Answer 31

- activate certain genes in the nucleus so that a particular enzyme of structural protein is produced - change the shape or structure of a protein so it is turned on or off - change the rate of production of an enzyme or structural protein by changing the rate of transcription or translation during protein synthesis

Question 32

What does the pituitary gland consist of?

Answer 32

- anterior lobe | - posterior lobe

Question 33

Why is the posterior lobe not a true gland?

Answer 33

It does not manufacture hormones

Question 34

What hormones does the posterior lobe secrete?

Answer 34

Oxytocin and ADH

Question 35

What hormones does the anterior lobe secrete?

Answer 35

- FSH, LH, GH, TSH, adrenocorticotropic hormone, prolactin

Question 36

How does the posterior lobe secrete hormones?

Answer 36

1. Both hormones are produced in special nerve cells in the hypothalamus. These cells have long extensions that pass through the infundibulum to the posterior lobe. 2. Hormones manufactured in these cells move down the extensions and are stored in the posterior lobe ready for release into the bloodstream. 3. The release of the hormones is triggered by nerve impulses initiated in the hypothalamus and conducted along the extensions.

Question 37

How does the anterior lobe secrete hormones?

Answer 37

1. Hormones are produced and stored in the anterior lobe. 2. The hypothalamus releases releasing or inhibiting factors into the bloodstream which passes through the infundibulum to the anterior lobe.

Question 38

Describe the process that stimulates the release of hormones from the anterior lobe of the pituitary.

Answer 38

1. Low levels of the hormone 2. stimulate receptors in the hypothalamus. 3. This triggers the release of releasing factors 4. Factors travel through blood capillaries 5. Acts on anterior lobe to release hormone

Question 39

How do steroid hormones work?

Answer 39

1. The hormone diffuses through the cell membrane and combines with the protein receptor inside the cell. The receptor may be on the mitochondria, other organelles or in the nucleus. 2. The hormone-receptor complex activates genes controlling the formation of particular proteins.