endocrine 1 Flashcards
regulation of physiological systems is constant by 2 regulators:
nervous regulation: highly specific & very rapid- almost instantaneous, adjusted second-by-second
chemical regulation: 2 types:
- non-specific chemical regulators (O2, CO2, H+, Ca), these have secondary functions as regulators somewhere else as well as their primary functions
- specific chemical regulators: hormones, they arouse
5 criteria to be a hormone
1- manufactured in specific endocrine glands & secreted directly into blood stream in trace picomolar amts
2- carried by bloodstream to target tissue/cell (every hormone is potentially exposed to every cell in body)
3- they react with specific receptors on/in target cell
4- they act catalytically, by activating specific enzymes
5- a single hormone can have multiple effects on one or several target tissues
name the 4 classes of hormones by structure
amines
prostaglandins
steroid hormones
peptide hormones
amine hormones are the ___ and ___
they are characterized by having ___
they are all derived from ___
examples of amine hormones
smallest & simplest
NH2 (amino group) off end of structure
from AA tyrosine
include catecholamines: dopamine & nor/epinephrine and the thyroid hormones (T3 &T4)
prostaglandin hormones are ___ that are derived from ___…
they have ___ biological life span and typically act ___, they get broken down ___
they are involved in ___ responses
cyclical fatty acids derived from membrane phospholipids (enzyme phospholipase A2 converts them to arachidonic acid, AA, –> then get diff types of prostaglandins)
short, locally close to where they are secreted, broken down very quickly
inflammatory responses (only detected by their breakdown products b/c such short life span)
steroid hormones are all derived from ___
they include ___ hormones
cholesterol (precursor for all steroid hormones)
major metabolic & sex hormones, major hormones that control mineral balance in body
peptide hormones are the ___ and ___
they start out as small proteins synthesized in ___… b/c it has a ___, which is ___…
example of peptide hormone
largest & most complex
rough ER, synthesized into pre prohormone b/c it has a leader/signal sequence on leading edge
leader sequence is hydrophobic AA’s (are lipid soluble, as peptide is made, leader sequence allows it to be pushed thru membrane of rough ER)
signal sequence then cleaved off –> now a prohormone –> gets processed into hormone and packed into secretory vesicles and secreted by exocytosis into blood stream
ex: insulin
4 functional classifications of hormones:
1- kinetic effect hormones: hormones that cause muscle contraction or secretion from other glands (oxytocin & smooth muscle)
2- metabolic effect hormones: change in metabolic rate due to activation of enzymes, speeds up biochemical reactions in metabolic pathways (epinephrine causes glycogen to be mobilized to glucose)
3- morphogenic effect hormones: results in change in growth & development (testosterone effects skeletal muscle during male puberty)
4- behavioral effects: change in behavior due to hormonal action (steroid effects behavior, ‘roid rage)
hormones are synthesized and secreted by ____, this is regulated by ____
endocrine glands
negative feedback, organized in short and long feedback loops
describe short feedback loop
start with endocrine gland A –> synthesizes and secretes hormone A –> hormone A has a target tissue (also an endocrine gland) –> causes 2nd endocrine gland to secrete hormone B –> hormone B circulates thru entire blood stream and back to endocrine gland A to cut off production of hormone A
describe long feedback loop
hormone B can have target tissue of another endocrine gland, target tissue/endocrine gland C –> secretes hormone C –> hormone C circulates thru and feeds back negatively to endocrine gland A, shuts down production of hormone A
2 general mechanisms of action for hormones: name them and what do they depend on?
depends on structure & solubility properties of hormones
1- lipid soluble hormones: steroids
2: lipid insoluble hormones amines & peptides
lipid soluble hormones’ mechanism of action:
made in endocrine glands, secreted into blood, circulates and hits target cell –> …
lipid soluble can dissolve right thru lipid bilayer of target cell membrane –> target cells contain a specific receptor (usually protein), receptor usually floating around cytoplasm –> hormone binds receptor forming hormone-receptor complex –> complex migrates to nucleus –> inside nucleus is genetic material controlling cell, the genes along the chromosomes are regulated by groups of proteins- histones & non-histone chromosomal proteins (NCPs) –> NCPs usually bind parts of the chromosome and cover up/mask certain genes, which keeps them turned off –> hormone-receptor complex has a structure that is complementary to those NCPs and can bind and pull it off –> activates the gene –> mRNA synthesis and downstream protein synthesis –> newly synthesized proteins that go on to have regulatory effect in target cell
lipid soluble hormones mechanism of action if to work by ___…
gene activation (relatively slow process)…but once proteins are made, effects are long-lasting
give an example of a lipid soluble hormones mechanism of action
testosterone hits target cell, skeletal muscle –> in nucleus of skeletal muscle, activates gene synthesis of actin & myosin –> each muscle cell begins to undergo hypertrophy (increase in mass) b/c packing more actin & myosin in that cell, takes time, but once its done, those cells are now bigger forever
also increased hematocrit - synthesis of EPO
