Chapter 16

Question 1

Overview of the endocrine system

Answer 1

• the endocrine system and the nervous system often do not function independently but in conjunction with each other
• both function to achieve and maintain stability of the internal environment
• both perform their regulatory functions by means of chemical messengers sent to specific cells
• the endocrine system secretes hormones into the bloodstream to signal specific target cells (target tissues/organs) throughout the body

Question 2

Endocrine system

Answer 2

Collection of specialized cells, and tissues that secrete hormones

Question 3

Endocrine glands

Answer 3

Ductless organs that secrete hormones into the blood, interstitial fluid, and lymph

Question 4

Hormones

Answer 4

• chemical messengers secreted by endocrine glands
• circulate in the bloodstream
• act on specific cells in the body (target cells) that have the appropriate hormone receptor

Question 5

Characteristics of the endocrine system

Answer 5

1) hormones have access to every cell
2) each hormone acts only on specific cells (target cells)
3) only specific cells have receptors for specific hormones
4) endocrine control is slower than the nervous system
5) endocrine and nervous systems interact

Question 6

classification of steroid hormones

Answer 6

• molecules manufactures form cholesterol by the endocrine cells
  Lipid - soluble, which allows them to easily pass through the phospholipid bilayer

Question 7

Classification of non-steroidal hormones

Answer 7

• molecules synthesize primarily from amino acids
  - protein hormones
  - glycoprotein hormones
  - peptide hormones
  - amino acid derivative hormones

Question 8

How steroid hormones work

Answer 8

• lipid - soluble, chemically derived from cholesterol
• enter target cells by diffusion across the cell membrane
• bind to intracellular receptor, forming a complex
• once in the nucleus, hormone-receptor complex attaches to DNA, activating specific genes
• mRNA is produced and then translated
• protein product carries out cellular response to hormone
• slower acting than no steroid hormones; takes minutes to hours

Question 9

How non-steroid hormones work

Answer 9

• water soluble
• bind to receptors on target cell membranes
• work through intermediate mechanisms to active existing enzymes
• may involve “second messenger” within the cell, such as cyclic AMP (cAMP)
• faster actin than steroid hormones; takes seconds to minutes

Question 10

How hormones participate in feedback loops

Answer 10

• many hormones participate in internal homeostasis control mechanisms
  
  • Negative feedback loops involving hormones include the following:
    - endocrine gland serves as the control center
    - hormone is the pathway between the control center and the effectors
    - target tissues or organs are the effectors

Question 11

Hypothalamus

Answer 11

• homeostatic control center of the brain
• links nervous system and endocrine system
• produces two hormones of its own
• monitors and controls hormone secretions of the pituitary gland

Question 12

Pituitary gland

Answer 12

• “master” gland
• secreted eight different hormones that regulate other endocrine organs
• two lobes: posterior and anterior

Question 13

Posterior pituitary gland

Answer 13

• the posterior pituitary is connected to the hypothalamus by neuroendocrine cells
  - hormones (ADH and oxytocin) made in cell bodies in hypothalamus are transported down axons to axon ensigns in posterior pituitary for storage and release
• Posterior pituitary hormones: non-steroidal
  
  • Antidiuretic hormone (ADH)
    Conserves water in kidneys
    Regulates water balance in the body
  • oxytocin
    Causes urine contraction during labor, and milk ejection through neuroendocrine reflex

Question 14

Anterior pituitary

Answer 14

• controlled by the hypothalamus
  - releasing and inhibits hormones form hypothalamus travel to pituitary through pituitary portal system
  - the release of each anterior pituitary hormone is controlled, at least partially, by the hypothalamus

Question 15

The six key hormones of the pituitary gland

Answer 15

ACTH (Adrenocorticotropic hormone): stimulates adrenal cortex to release glucocorticoids (cortisol); promotes and maintains normal growth and development of the cortex of the adrenal gland
TSH (Thyroid-stimulating hormone): acts on thyroid gland, promotes release of thyroid hormones
FSH & LH (Gonadotrophs): stimulate growth, development, and function of ovaries and testes; not produced until about age 10-13 (puberty); increase in production initiates sexual maturation and development at puberty
Prolactin: stimulates development of mammary glands an milk production
Growth hormone: has widespread effects on the body; major effects on bone, muscle; most of its growth-promoting effects occur during childhood and adolescence

Question 16

Pituitary disorders

Answer 16

Diabetes insipidus: hypo secretion of ADH results in inability to conserve water appropriately; causes excessive urinate, dehydration, thirst
Gigantism: hypersecretion of growth hormone in body
Acromegaly: excessive growth hormone over a long period in adults
Pituitary dwarfism: hyposecretion of growth hormone, treated by administration of GH throughout childhood

Question 17

Pineal gland

Answer 17

• tiny structure resembling a pine nut, located on the dorsal aspect of the brains diencephalon
• it is a member of two body systems because it acts as a part of the nervous system and as a part of the endocrine system
• produced a number of different hormones, but the principle hormone is melatonin
  - important aspect of the “biological clock”

Question 18

Thyroid gland

Answer 18

• Secretion: mediated through hypothalamus-pituitary secretions
• steroidal hormones: thyroxine (T4) and triiodothyronine (T3); both regulate production of ATP from glucose and modify the metabolic rate
  Calcitonin: Lowers blood calcium levels; decreases rate of bone reabsorption by inhibiting osteoclasts; stimulates uptake of calcium by bones

Question 19

Parathyroid hormone (PTH):

Answer 19

• parathormone
• PTH is the main hormone for blood calcium homeostasis
• increasing the amount of osteoclasts activity and inhibiting osteoblast to release calcium into the bloodstream

Question 20

Iodine deficiency can cause goiter

Answer 20

• iodine is quirked for production for active thyroid hormones
• inadequate dietary iodine leads to underproduction of thyroid hormones
• the feedback response to inadequate thyroid hormone is for the hypothalamus and pituitary t further stimulate the thyroid gland in a vicious cycle that causes hypertrophic of the thyroid (goiter)

Question 21

Adrenal cortex

Answer 21

• Zona Glomoerulosa:
  
  • mineralcorticoids
• Zona fasciculata:
  
  • glucocorticoids
• Zona reticularis:
  
  • glucocorticoids
  • gonadcorticoids
    - corticosteroids

Question 22

Adrenal medulla

Answer 22

• epinephrine -> 80%
• norepinephrine -> 20%

Question 23

Adrenal cortex is where

Answer 23

The adrenal cortex is in the outer layer of the adrenal gland
- glucocorticoids, such as cortisol
- mineralcorticoids, such as aldosterone

Question 24

Adrenal medulla is where

Answer 24

The adrenal medulla is the inner layer of the adrenal gland
- epinephrine (adrenaline)
- norepinephrine (noradrenaline)

Question 25

Glucocorticoids (cortisol)
Mineralcorticoids (aldosterone)

Answer 25

Glucocorticoids (cortisol)
- secretion mediated through hypothalamus-pituitary secretions
- maintain blood glucose levels during prolonged fasting
- suppress inflammatory responses
Mineralcorticoids (aldosterone)
- regulate sodium, potassium, water balance
- act on kidneys, promoting sodium reabsorption and potassium excretion

Question 26

Adrenal medulla: epinephrine and norepinephrine

Answer 26

• neuroendocrine organ
• secretion stimulated by
  - sympathetic nervous system
• Hormones: nonsteroidal
  - epinephrine and norepinephrine
  - enhance function of sympathetic nervous system (fight-or-flight response)

Question 27

Pancreatic islet cells

Answer 27

Alpha cell (a cell):
- Glucagon
- increase blood glucose levels
- converts glycogen into glucose in the liver (hyperglycemia effect)
Beta cell (cell):
- Insulin
- decreases blood glucose levels
- promotes glucose absorption and utilization by tissues/cells (hypoglycemic effect)
Delta cells (D cell):
- somatostatin: primary role is regulating (inhibiting) other pancreatic islet cells
Polypeptide cell (PP or F cell):
- pancreatic polypeptide: influences the digestion and distribution of food mechanisms
Epsilon cell (E cell):
- ghrelin: stimulates the hypothalamus to boost appetite

Question 28

Gonads

Answer 28

Testes: testosterone -> growth and maintenance of male sexual characteristics and sperm production
Ovaries: estrogen -> promote the development and maintenance of female sexual characteristics progesterone -> “pregnancy-promoting” hormone

Question 29

Other glands of the endocrine system

Answer 29

Thymus: thyroxin and thymopoietin
- assist maturation of t lymphocytes
- most active during early development and childhood
Heart: atrial natriuretic hormone (ANH):
- helps regulate blood pressure by increasing the rate of sodium and water excretion in the urine
Adipose tissue: Leptin -> regulates energy balance by hunger
Placenta: human chronic gonadotropin (hCG)
Kidney: Erythropoietin (stimulates production of erythrocytes
Digestive system: Gastrin, secretin, cholecystokinin (have effects on stomach, pancreas, gallbladder

Question 30

Diabetes Mellitus

Answer 30

• disorder of blood sugar regulation
  
  • inability to get glucose into cells where it can be used, results in high blood sugar levels
  • glucose and excess water appear in the urine
• abnormal metabolism of carbohydrates, proteins, and lipids causes most of the complications
• symptoms: dehydration, thirst, fatigue, frequent infection, blurred vision, tingling of hands/feet
• two types: type 1 and type 2

Question 31

Type one diabetes

Answer 31

• pancreas does not produce enough insulin
• also known as insulin-dependent diabetes
• treated with insulin injections
• results from autoimmune destruction of beta cells of pancreatic islets
• there may be a genetic component and/or environmental trigger
• typical onset is during childhood or adolescence
• 5-10% of all cases of diabetes

Question 32

Type 2 diabetes

Answer 32

• non-insulin defendant
• characterized by insulin resistance: cells fail to respond appropriately to insulin
• most often seen in adults over 40
  — lifestyle factors (diet, exercise) play a role in onset
• treatment: lifestyle changes, variety of medications
• 90-95% of all cases of diabetes

Question 33

Hypothyroidism

Answer 33

• underactive thyroid gland
  Children:cretinism
  Slowed body growth, altered brain development, delayed puberty
  Adults: myxedema
  Edema, lethargy, weight fain, low BMR

Question 34

Hyperthyroidism

Answer 34

Overactive thyroid gland
- increased BMR, hyperactivity, nervousness, agitation, weight loss
- Graves’ disease: autoimmune form of hyperthyroidism

Question 35

Addison’s disease

Answer 35

Adrenal gland disorder: failure of the adrenal cortex occurs
- hyposecretion of cortisol and aldosterone
- lowers blood glucose and sodium
- slow to develop, chronic fatigue, weakness, abdominal pain, weight loss, bronzing of the skin

Question 36

Cushing’s syndrome

Answer 36

• Adrenal gland disorder: Excessive cortisol secretion
  Excessive prod ion of glucose from glycogen
  Retention fo too much salt and water
  Loss of muscle mass, change in fat distribution
  Similar symptom seen with the use of cortisol and cortisol-like drugs

Question 37

Hypogonadism

Answer 37

Abnormally low testosterone levels
- prior to birth: results in ambiguous, undeveloped, or female genitalia
- prior to adolescence: results in delayed or incomplete male sexual maturation
Adult males: may result in -> low sperm count, erecting dysfunction, unusual fatigue, decreased sex drive, depression
Treatment: testosterone replacement therapy