Chapter 13 - Hormones Continued

Question 1

Endocrine system

Answer 1

• Along with nervous system, regulates functions of body
  to maintain homeostasis, and coordinates communication
• Unique system, since organs are not anatomically
  connected

Question 2

what are the Major endocrine glands?

Answer 2

• Pituitary gland
• Thyroid gland
• Parathyroid glands
• Adrenal glands
• Pancreas
• Pineal gland
• Thymus
• Ovaries and Testes (reproductive glands)

Question 3

Endocrine glands

Answer 3

• Cells, tissues, and organs that make up the endocrine system
• Ductless; secrete hormones directly into the body fluids
• “Endocrine” means “internal secretion”
• Hormones act only on target cells that contain receptors for them

Question 4

Exocrine glands

Answer 4

• Glands that secrete into ducts or tubes that lead to a body surface
• Secrete externally
• Deliver their products directly to a specific site

Question 5

Other cells secrete ________ __________ internally, called “_____ ________ (not actually hormones)

Answer 5

chemical messengers
&
local hormones

Question 6

Paracrine secretions…?

Answer 6

affect nearby cells

Question 7

Autocrine Secretions

Answer 7

affect only the cells that secrete them

Question 8

Comparison Between Nervous and Endocrine Systems

Answer 8

• Both the nervous and endocrine systems function in
  communication
• Both systems communicate via chemicals that bind to receptor
  molecules
• Nervous system responds faster than endocrine system
• Endocrine system’s effects can last longer than those of
  nervous system

Question 9

Nervous system releases…?

Answer 9

neurotransmitters into synapses

Question 10

Endocrine system secretes…?

Answer 10

hormones into bloodstream

Question 11

Hormones

Answer 11

• Are released into extracellular fluid
• Then diffuse into blood
• Method of transport through blood depends on whether
  hormone is lipid-soluble of water-soluble
• Very powerful substances in low concentrations

Question 12

Hormones are organic compounds; 2 general types which are…?

Answer 12

Steroid or steroid-like hormones
&
Nonsteroid hormones

Question 13

Steroid or steroid-like hormones

Answer 13

• Steroids: lipids containing complex rings of carbon and hydrogen
  atoms
• All steroid hormones are produced from cholesterol
• Examples: Sex hormones (testosterone, estrogens), and adrenal
  cortex hormones (cortisol, aldosterone)

Question 14

Nonsteroid hormones

Answer 14

• Amines: Derived from tyrosine (epinephrine, norepinephrine,
  thyroxine)
• Proteins: Composed of long chains of amino acids (growth
  hormone)
• Peptides: Short chains of amino acids (ADH, oxytocin)
• Glycoproteins: Carbohydrates joined to proteins (TSH)

Question 15

Hormone Actions

Answer 15

• Exert effects by altering metabolic processes:
  - May alter enzyme activity
  - May change rate of membrane transport of a substance
• Deliver messages by binding to their receptors on/in target
  cell
• Can cause changes in target cells even in extremely low
  concentrations

Question 16

Number of receptors determines strength of response, and
can be changed to alter the response

Answer 16

• Upregulation:
• Downregulation:

Question 17

Upregulation

Answer 17

Increase in number of receptors on target cell, in
response to a decrease in hormone level

Question 18

Downregulation

Answer 18

Decrease in number of receptors on target cell,
due to an increase in hormone level

Question 19

Steroid and Thyroid Hormones

Answer 19

• Have poor water-solubility
• Transported through blood bound to plasma proteins
• Steroid hormones can diffuse through lipid bilayer of cell
  membranes
• Thyroid hormones are thought to enter cell by specific
  transport methods
• Both types bind to receptors inside cell, usually in nucleus
• Cause transcription of particular genes in DNA
• Protein synthesis leads to the action of the hormone

Question 20

Nonsteroid Hormones

Answer 20

• Cannot penetrate the lipid bilayer of cell membranes
• Bind to receptors on the target cell membranes

Question 21

Hormone is considered a…?

Answer 21

first messenger

Question 22

Chemical that induces changes leading to hormone’s
effect is considered a…?

Answer 22

second messenger

Question 23

The entire process of chemical communication, from
outside cells to inside, is called…?

Answer 23

signal transduction

Question 24

Hormone secretion and effects:

Answer 24

• Secretion is precisely regulated
• Secretion is primarily controlled by negative feedback
  mechanisms
• Effects can be short-lived (a few minutes) or may last for
  days.
• Some are excreted in the urine after exerting their effects
• Can be broken down by enzymes, mainly from the liver, to
  stop their effects

Question 25

Negative feedback

Answer 25

* A control mechanism in which rising level of a hormone leads to a decrease in hormone secretion * As hormone is used up, inhibition stops, and secretion begins again * Main methods of control of hormone secretion

Question 26

3 methods of negative feedback control of hormone secretion

Answer 26

- hypothalamus - nervous system control - changes in composition of internal enviroment

Question 27

Hypothalamus

Answer 27

controls release of anterior pituitary hormones; then pituitary hormones secrete hormones that control activity of other glands. (Tropic hormones: Hormones that act on other glands)

Question 28

Nervous system control

Answer 28

Nervous system directly stimulates some glands to secrete their hormones (via nerve impulses)

Question 29

Changes in composition of internal environment

Answer 29

Changing levels of a specific substance in the blood (an ion, glucose, etc.) stimulates or inhibits secretion of certain hormones

Question 30

Positive feedback

Answer 30

Control mechanism in which rising level of a hormone leads to an increase in secretion; used in small number of cases of hormone control, mainly in reproductive system