Endocrinology: overview

Question 1

differentiate nervous vs endocrine communication

Answer 1

• nervous system is rapid (ms), electrical signals, and discrete (NTs stay in specific areas)
• endocrine system - slow, diffuse, chemical signals.

Question 2

What was the first endocrine experiment?

Answer 2

the Berthold experiment (1849), removed testes from chickens, observed behavior and comb and wattle.

Question 3

what is the definition of a hormone?

Answer 3

a chemical substance synthesized by specialized tissues, which is secreted into and carried by the bloodstream to target organs and cells, where it produces SPECIFIC EFFECTS, generally for the purpose of maintaining homeostasis or regulating metabolic processes.

Question 4

Mechanisms of Hormone action: do NOT initiate _________. ___ - _____ reaction time.

Answer 4

reactions in target cells de novo. (modulates up or down regulation)
minutes - hours - days (epinephrine probably fastest)

Question 5

stimuli for hormone secretion: ___, ___, ___, ____

Answer 5

nutrient, ion, neuron, hormone.

Question 6

hormones are carried in the bloodstream in ____ concentrations

Answer 6

low (10 ^-12 – 10^-6)

Question 7

blood levels of hormone = ________

Answer 7

secretion - clearance

clearance = metabolism and/or excretion

Question 8

what are the three chemical types of hormones?

Answer 8

• amino acid derivatives (catecholamines and indolamines)
• peptides(angiotensin, vasopressin)/proteins
• steroids (cholesterol derivatives)

Question 9

membrane fixed receptor model:

• used by ____ hormones
• utilizes ______
• _____ is hallmark feature

Answer 9

• hydrophilic
• 2nd messenger system
• amplification process

Question 10

enzyme that breaks down cAMP?

Answer 10

phosphodiesterase

Question 11

mobile receptor model:

• used by ____ hormones
• receptors can be ____ or _____
• _____ is hallmark cellular response feature for these hormones

Answer 11

• lipophilic
• cytosolic or nuclear
• synthesis of new protein

Question 12

receptor modulation:

• receptor ______
• receptor ______
• _____ regulation

Answer 12

• affinity (sensitivity)
• number (maximal response = saturable binding)
• down/up (homologous, heterologous)

Question 13

What is an example of heterologous regulation?

Answer 13

thyroid hormone can cause increased HR by up regulating B1 receptors in heart

Question 14

what is an example of homologous regulation?

Answer 14

cell modulating its own receptors

Question 15

list the three general types of endocrine disorders.

Answer 15

• (apparent) hormone hyposecretion
• (apparent) hormone hypersecretion
• abnormal hormone responsiveness

Question 16

list some ways too little hormone activity can occur.

Answer 16

• too little hormone secreted by endocrine gland
• increased removal of the hormone from the blood
• abnormal tissue responsiveness to the hormone (lack of target-cell receptors or lack of an enzyme essential to the target-cell response - adenylate cyclase, phosphodiesterase)

Question 17

list some ways that lead to too much hormone activity.

Answer 17

• too much hormone secreted by endocrine gland
• reduced plasma protein binding of the hormone (too much free biologically active hormone)
• decreased removal of the hormone from the blood (decreased excretion or inactivation)

Question 18

hormone hyposecretion can be ____, ____, or result from a defect in the gland such as ____, _____, ____, etc

Answer 18

primary, secondary (trophic hormone defect)

chemical/toxin, dietary (iodine), disease, genetic, immunologic, iatrogenic, idiopathic

Question 19

hormone hypersecretion can be ___, ____, or from gland defects such as _______

Answer 19

primary, secondary

functional tumor, ECTOPIC TUMOR, immunologic

Question 20

list some types of abnormal hormone responsiveness.

Answer 20

homologous down-regulation
heterologous up-regulation (thyroid on heart)
genetic defects in receptor expression (androgen receptor defect)
defective hormone activation
receptor auto-immune dysfunction (graves disease)
post-receptor signal transduction defects (AC, phosphodiesterase)

Question 21

How are the nervous system and endocrine system similar?

Answer 21

they both alter their target cells by releasing chemical messengers (NTs and hormones) that bind with specific receptors on the target cells, binding triggers a cellular response.