Endocrinology: overview Flashcards
differentiate nervous vs endocrine communication
- nervous system is rapid (ms), electrical signals, and discrete (NTs stay in specific areas)
- endocrine system - slow, diffuse, chemical signals.
What was the first endocrine experiment?
the Berthold experiment (1849), removed testes from chickens, observed behavior and comb and wattle.
what is the definition of a hormone?
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.
Mechanisms of Hormone action: do NOT initiate _________. ___ - _____ reaction time.
reactions in target cells de novo. (modulates up or down regulation)
minutes - hours - days (epinephrine probably fastest)
stimuli for hormone secretion: ___, ___, ___, ____
nutrient, ion, neuron, hormone.
hormones are carried in the bloodstream in ____ concentrations
low (10 ^-12 – 10^-6)
blood levels of hormone = ________
secretion - clearance
clearance = metabolism and/or excretion
what are the three chemical types of hormones?
- amino acid derivatives (catecholamines and indolamines)
- peptides(angiotensin, vasopressin)/proteins
- steroids (cholesterol derivatives)
membrane fixed receptor model:
- used by ____ hormones
- utilizes ______
- _____ is hallmark feature
- hydrophilic
- 2nd messenger system
- amplification process
enzyme that breaks down cAMP?
phosphodiesterase
mobile receptor model:
- used by ____ hormones
- receptors can be ____ or _____
- _____ is hallmark cellular response feature for these hormones
- lipophilic
- cytosolic or nuclear
- synthesis of new protein
receptor modulation:
- receptor ______
- receptor ______
- _____ regulation
- affinity (sensitivity)
- number (maximal response = saturable binding)
- down/up (homologous, heterologous)
What is an example of heterologous regulation?
thyroid hormone can cause increased HR by up regulating B1 receptors in heart
what is an example of homologous regulation?
cell modulating its own receptors
list the three general types of endocrine disorders.
- (apparent) hormone hyposecretion
- (apparent) hormone hypersecretion
- abnormal hormone responsiveness
list some ways too little hormone activity can occur.
- 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)
list some ways that lead to too much hormone activity.
- 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)
hormone hyposecretion can be ____, ____, or result from a defect in the gland such as ____, _____, ____, etc
primary, secondary (trophic hormone defect)
chemical/toxin, dietary (iodine), disease, genetic, immunologic, iatrogenic, idiopathic
hormone hypersecretion can be ___, ____, or from gland defects such as _______
primary, secondary
functional tumor, ECTOPIC TUMOR, immunologic
list some types of abnormal hormone responsiveness.
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)
How are the nervous system and endocrine system similar?
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.
