Kaplan Ch. 5 - The Endocrine System

Question 1

What are the 3 classifications of hormones?

Answer 1

Peptide hormones
Steroids
Amino acid derivatives

Question 2

1) What are peptide hormones made up of?
2) How do they range in size?
3) How do peptide hormones transduce their signals?

Answer 2

1) Amino acids
2) can be small to fairly large
3) Peptide hormones are first messengers that bind to receptors extracellularly and trigger transmission of a second messenger signal

Question 3

What are 3 examples of common second messengers?

Answer 3

cAMP, inositol triphosphate (IP3), calcium

Question 4

How active are peptide hormones?

How long do their effects last?

How do peptide hormones reach their target cells?

Answer 4

Peptide hormones are fast acting

Their effects are short lived and constant stimulation is required for longer duration effects to be observed

They are polar so they travel freely in the blood stream to reach their target cells

Question 5

Steroid hormones:

1) These are derived from? What benefit does this impart?
2) Where are these produced?
3) Where are receptors for these?
4) How do steroid hormones reach target tissue?
5) What change is brought about when steroid binds to receptor?

Answer 5

1) Cholesterol, they are nonpolar so they can cross cell membranes
2) produced in the gonads and adrenal cortex
3) intracellular or intranuclear
4) Via transport proteins, though hormone is inactive when attached to protein
5) Steroid-receptor complex undergoes conformational change, which allows direct binding to DNA by receptor and increased or decreased transcription of genes

Question 6

Amino Acid Derivative Hormones

1) there are 4 important hormones to know in this category. What are they?
2) what is a direct hormone? What is a tropic hormone?

Answer 6

1) epinephrine, norepinephrine, thyroxine, triiodothyronine
2) direct hormones are secreted and then act directly on a target tissue

Tropic hormones are released and act on intermediary tissues to ultimately lead to the end effect. These usually originate in the brain.

Question 7

What are some helpful endings of names of hormones that can be used to identify amino acid / peptide hormones from steroid hormones?

Answer 7

Peptide / AA end in -in -ine

Steroid hormones end in -ol, -oid, or -one

Question 8

If hypothalamus secretes GnRH into the hypophyseal portal system, then _____ is secreted by the anterior pituitary.

Answer 8

FSH (follicle stimulating hormone) and LH (luteinizing hormone)

These act on gonads

Question 9

If hypothalamus secretes GHRH (growth hormone releasing factor) into the hypophyseal portal system, then _____ is secreted by the anterior pituitary.

Answer 9

GH (growth hormone)

Question 10

If hypothalamus secretes TRH (thyroid releasing factor) into the hypophyseal portal system, then _____ is secreted by the anterior pituitary.

Answer 10

TSH (thyroid stimulating hormone)

These act in thyroid

Question 11

If hypothalamus secretes CRF (corticotropin releasing factor) into the hypophyseal portal system, then _____ is secreted by the anterior pituitary.

Answer 11

ACTH (adrenocorticotropic hormone)

Acts on adrenal cortex

Question 12

The mnemonic FLAT PEG is used to remember the hormones secreted by the anterior pituitary. What do each of these letters represent and what is the difference between the FLAT and PEG?

Answer 12

F = FSH
L = LH
A = ACTH
T = TSH

P = prolactin
E = endorphins
G = GH

FLAT hormones are tropic
PEG hormones are direct

Question 13

What is the role of endorphins?

Answer 13

Reduce perception of pain

Question 14

What does growth hormone do?

Answer 14

Promote growth of bone and muscle

Question 15

How is GH related to gigantism and dwarfism?

Answer 15

In childhood, before the epiphyseal plates of the bones have finished developing, a heightened [GH] = gigantism and decreased = dwarfism

Question 16

What is acromegaly? How is it related to GH?

Answer 16

Occurs in adults, affects bones in extremities, bones continue to grow in size in adulthood when it shouldn’t

Caused by increased levels of GH in adult

Question 17

ADH

1) what is this?
2) Where is it secreted?
3) what does it do?

Answer 17

1) antidiuretic hormone
2) secreted by posterior pituitary in response to decreased blood volume or increased blood osmolality
3) ADH makes the collecting duct in the renal system more permeable to water so there is greater readsorption of water from filtrate in nephrons resulting in increased water in the blood

Question 18

Oxytocin

1) 3 effects of this hormone as relates to childbirth
2) type of feedback this is under?

Answer 18

1) contraction of uterine smooth muscle during childbirth, contraction of smooth breast muscle during breast feeding to eject milk, involved in binding behavior
2) positive

Question 19

ADH are produced by the _____ and secreted by the _____.

Answer 19

Hypothalamus, posterior pituitary

Question 20

What are the 2 major functions of the thyroid?

Answer 20

1) set nasal metabolic rate

2) regulate calcium homeostasis

Question 21

What are the 2 thyroid hormones responsible for setting basal metabolic rate?

Answer 21

1) triiodothyronine (T3 Where 3 represents # iodine ions)

2) thyroxine (T4)

Question 22

How to triiodothyronine and thyroxine make alter the basal metabolic rate?

Answer 22

By making energy production more or less efficient and altering utilization of glucose / fatty acids

Question 23

Hypothyroidism

Answer 23

Deficiency in iodine or inflammation of thyroid causes this, results in insufficient secretion of thyroid hormones. Symptoms are lethargy, decreased body temp, weight gain, slowed heart / respiratory rate, cold intolerance.

Question 24

Hyperthyroidism

Answer 24

May result from tumor or over stimulation of thyroid, heightened activity level, increase body temp, increased respiratory and heart rates, heat intolerance, weight loss

Question 25

Calcitonin:

1) Where is it produced?
2) what does it do?
3) how? (3)
4) how is this hormone triggered?

Answer 25

1) in C-cells of thyroid
2) reduce levels of calcium in blood
3) a) increase calcium excretion from kidneys
b) decrease calcium adsorption from gut
c) increased storage of calcium in bones
4) by high levels of calcium in blood

Question 26

Parathyroid hormone (PTH):

1) what is it’s function?
2) how does it accomplish its function (3)?

Answer 26

1) increase blood calcium levels
2) a) decrease excretion of calcium by kidneys
b) increase adsorption if calcium in gut
c) increase bone resportion

Question 27

What is the relationship between PTH and vitamin D?

Answer 27

PTH activates vitamin D, required for adsorption of calcium and phosphate in the gut

Question 28

What are the 3 classes of hormones secreted by the adrenal cortex?

Answer 28

1) glucocorticoids
2) mineralocorticoids
3) cortical sex hormones

Question 29

Glucocorticoids:

1) In general, what is their function?
2) What are the names of 2 hormones in this group that are most likely to be seen on MCAT?
3) what is the mechanism by which these hormones accomplish their function?
4) In addition to their primary function, what other functions do these hormones perform?

Answer 29

1) Regulate glucose level
2) cortisol and cortisone
3) Raise blood glucose by increasing gluconeogenesis and decreasing protein synthesis
4) reduce inflammation and immunologic responses

Question 31

Mineralocorticoids:

1) what are the function of these hormones?
2) Where are these secreted?
3) what is the most important hormone in this group to know?

Answer 31

1) responsible for maintaining salt and water homeostasis
2) secreted from the adrenal cortex
3) aldosterone

Question 32

Explain the renin-angiotensin-aldosterone system.

Answer 32

Decreased BP causes juxtaglomerular cells in kidneys to secrete renin, which cleaves the inactive plasma protein angiotensin to its active form angiotensin I, which is then converted to angiotensin II by angiotensin converting enzyme (ACE) in the lungs, angiotensin II stimulates adrenal cortex to secrete aldosterone, which increases the sodium and water resorbed by the blood. This increases blood volume (no change on osmolarity) and this increases BP. Increased BP exerts negative feedback renin to prevent further aldosterone being secreted.

Question 33

Mnemonic to remember functions of 3 corticosteroids? SSS

Answer 33

Salt
Sex
Sugar

Question 34

What 2 hormones are secreted by the adrenal medulla?

Answer 34

Epinephrine and norepinephrine

Question 35

What are the main endocrine cells of the pancreas?

How are these cells sub-divided?

Answer 35

Islets of Langerhans

Alpha cells (secrete glucagon)
Beta cells (secrete insulin)
Delta cells (secrete somatostatin)

Question 36

Glucagon:

1) when is glucagon secreted?
2) what does this hormone do?

Answer 36

1) during times of fasting when blood plasma levels of glucose are low
2) stimulates degradation of protein and fat, converts glycogen stores to glucose and promotes gluconeogenesis

Question 37

Insulin:

1) when is this hormone secreted?
2) what does this hormone do?

Answer 37

1) when blood glucose is high

2) induced muscle and liver cells go uptake glucose and store as glycogen, stimulates fat and protein synthesis

Question 38

Hypoglycemia

Answer 38

When excess insulin is produced, cells take up more glucose than would otherwise resulting in low blood glucose levels

Question 39

Hyperglycemia

Answer 39

Excess glucose in the blood

Question 40

Diabetes mellitus:

1) what is type I?
2) what is type II?
3) what are 2 common symptoms of diabetics?
4) what effect does excess blood glucose have on the kidneys?

Answer 40

1) type I diabetes is caused by autoimmune destruction of beta islet cells, type I diabetics are insulin dependent to combat hyperglycemia
2) type II diabetes is caused by receptor level resistance to insulin
3) increases thirst (polydipsia) and increased frequency of urination (polyuria)
4) excessive glucose in the filtrate overwhelms kidney’s ability to reabsorb glucose resulting in glucose being present in the urine

Question 41

What is somatostatin?

What stimulates its secretion?

Answer 41

Inhibitor of both insulin and glucagon

Stimulates by high blood glucose and amino acid concentrations