Hormones - An Overview Flashcards
1
Q
What is the main function of endocrine systems?
A
Responsible for regulating other organ systems using chemical messengers called HORMONES
- directs long-term changes in other organ systems with hormones (chemical messengers)
- multiple, independent systems interacting using different signals to tell other organs what to do
2
Q
What are hormones?
A
Hormones are chemical messengers that are used to regulate other organ systems through endocrine systems
- chemical messenger molecules that travel through the blood to reach its target organ(s)
3
Q
What are primary endocrine organs?
A
Organs that secrete hormones as their MAIN or ONLY function
4
Q
What are the 8 primary endocrine organs?
A
- hypothalamus
- pineal gland
- parathyroid glands
- pituitary gland
- thyroid gland
- adrenal glands
- pancreas (pancreatic islets)
- gonads (testes and ovaries)
5
Q
What are secondary endocrine organs?
A
Organs that secrete hormone(s) in ADDITION to carrying out their own primary functions
6
Q
What are some examples of organs with secondary endocrine functions?
A
- hypothalamus*
- pancreas*
- heart
- thymus
- digestive tract
- kidneys
- gonads*
7
Q
What are the three MUST criterion for a molecule to be a hormone?
A
A hormone is a chemical messenger molecule that travels through the blood to reach its target organ(s)
The definition of a hormone is:
1. Be produced/synthesized by one cell
2. Bind to and trigger activation of protein receptors located on or in another cell
3. Travel in the circulatory system/through the blood to reach its target cell
8
Q
Is it a hormone?
Cholecalciferol (Vitamin D) is synthesized by the epidermis, released into the circulation and taken up by
liver cells for chemical processing into calcidiol, before being sent to the kidney.
A
NOT A HORMONE!
- Produced by epidermis
MISSING 2. Does not bind to activation protein receptors
- Travels through blood/circulation to reach liver cells
9
Q
Is it a hormone?
Calcidiol is converted into calcitriol by cells within the kidney. Calcitriol is released into the bloodstream
where it acts on intestinal cells, leading to increased absorption of dietary calcium.
A
HORMONE!
- Produced by kidney cells
- Acts on intestinal cells and leads to increased absorption of dietary calcium (activates receptors)
- Released into the bloodstream / travels through circulatory system
10
Q
Is it a hormone?
In response to APs, norepinephrine (and a small amount of epinephrine) are released from postganglionic sympathetic neuron axon terminals into synaptic clefts and act via adrenergic receptors.
A
NOT A HORMONE!
- Released from post-ganglionic sympathetic neuron axon terminals
- Acts on adrenergic receptors
MISSING 3. Does not travel through bloodstream / travels through synaptic cleft
11
Q
Is it a hormone?
In response to graded potentials, epinephrine (and a small amount of epinephrine) are released into the
bloodstream via the adrenal medulla, and act via adrenergic receptors.
A
HORMONE!
- Epinephrine is a chemical messenger released from adrenal medulla
- Acts on adrenergic receptors
- Released into the bloodstream
12
Q
Is it a hormone?
In response to sympathetic postganglionic stimulation of adrenergic receptors, adipose cells release fatty acids into the bloodstream, which are taken up by other cells and used for metabolic processes.
A
NOT A HORMONE!
MISSING 1. Fatty acids are not produced by adipose cells
MISSING 2. Do not bind to other receptor proteins
- Travels through the bloodstream
13
Q
Is it a hormone?
In response to detection of low circulating blood glucose levels, liver cells synthesize and release glucose into the bloodstream, which is taken up by other cells and used for metabolic processes.
A
NOT A HORMONE!
MISSING 1. Synthesized by cells (glucose is not synthesized in the body(?))
MISSING 2. Does not bind to receptor proteins
- Travels through the bloodstream
14
Q
Is it a hormone?
In response to detection of low-circulating blood glucose levels, pancreatic cells secrete glucagon, which stimulates liver cells to synthesize and release glucose.
A
HORMONE!
- Pancreatic cells secrete/synthesize glucagon
- Acts on liver cell receptors to cause synthesis and release of glucose
- Travels through the bloodstream to get from the pancreas to liver
15
Q
What are the two similarities between the endocrine systems and nervous system?
A
- Both use chemical messengers
- can be in the form of neurotransmitters or hormones - Coordinating roles
- tells other systems what to do
- participate in negative feedback loops to maintain homeostasis
- participate in allostatic adaptations
16
Q
What are the four main differences between endocrine systems and the nervous system?
A
- Mode of transport
ES: must travel through the bloodstream/circulatory system to reach its target cells
NS: travel across the synaptic cleft/released into extracellular space - Response speed
ES: much slower because hormones must travel through the bloodstream in order to reach their target cells
NS: much faster than the endocrine system because neurons are all interconnected (can be myelinated as well) - Response duration
ES: response speed is much slower than nervous system but the response durations last longer than NS
NS: response speed is fast but the duration of the responses are short-lived - Response localization
ES: responses are widespread / can go anywhere you want it to go
NS: responses are localized
17
Q
How are hormones grouped into three different classes?
A
Hormones can be grouped into three different classes based on their CHEMICAL STRUCTURE
18
Q
Chemical structure of a hormone affects:
A
Chemical structure affects how the hormone is synthesized, released, and received by its target cell
How the hormones are produced, stored and released, and received by its target cell depends on its chemical structure
19
Q
What are the three classes of hormones?
A
Class 1 - Amino acid derivatives
Class 2 - Peptide hormones
Class 3 - Lipid derivatives
20
Q
What are amino acid derivative hormones?
A
Derived hormones (ending in ‘-ine’) are derived from tyrosine and tryptophan and include epinephrine and norepinephrine
21
Q
What are peptide hormones?
A
Hormones which are made of peptide molecules
The largest class is hormones out of the three
22
Q
What are lipid derivative hormones?
A
Structurally similar to cholesterol and include steroid hormones such as estradiol and testosterone
23
Q
Out of the three classes of hormones, which class is the largest? Which is the smallest?
A
Class 2 - Peptide Hormones are the largest group with the greatest number of different hormones
Class 1 - Amino Acid Derivates are the smallest group of hormones of the three
24
Q
What are class 1 hormones?
There are two examples: epinephrine/adrenaline, thyroid hormones
A
(E) amine hormones synthesized by modifying amino acids
ex: epinephrine/adrenaline, thyroid hormones
25
Where are class 1 hormones synthesized? (Specifically E)
Class 1 hormones are synthesized at the adrenal gland (adrenal medulla) by chromaffin cells
Epinephrine/adrenaline (E) is synthesized from phenylalanine and tyrosine by enzymes within the CYTOSOL
26
How are class 1 hormones synthesized? (Specifically E)
Start as an animo acid
Different enzymes add or take away functional groups to the starting amino acids
Eventually you get epinephrine or adrenaline from modifying amino acids
27
What are chromaffin cells? (Specifically E)
Cells in the adrenal medulla of the adrenal gland that are responsible for synthesizing, storing, and releasing E (amino hormone) for the body's fight or flight response
28
Epinephrine is also known as
ADRENALINE
29
Adrenaline is also known as
EPINEPHRINE
30
Where is epinephrine stored and under what conditions is it released?
1. Stored in vesicles that are released when intracellular calcium levels rise
2. E is released when the vesicles go through regulated (by acetylcholine) exocytosis
31
Describe the process in which class 1 hormones are synthesized and released
1. Epinephrine (class 1) hormones are going to be processed and modified from amino acids using enzymes (from adrenal gland and in cytosol)
2. Stored in vesicles
3. When calcium levels rise, epinephrine is released from the vesicle stores and into the bloodstream
32
What are peptide hormones and how are they synthesized differently from amino acid derivatives?
- hormones that are made of peptide molecules
- synthesized as larger inactive proteins by ribosomes and then are activated through enzymatic cleavage
- produced with extra amino acid sequences preprohormone that they eventually lose to become a hormone
33
What produces peptide hormones
Synthesized by ribosomes on the RER
- peptide hormones are gene products synthesized with extra amino acid sequences:
PRE PRO HORMONE
34
Trace the path of synthesis of a peptide hormone
1. RER produces preprohormone
- mRNA codes for preprohormone
2. Preprohormone gets transported in a transport vesicle to the golgi complex as an inactive prohormone now
3. Prohormone is processed through the golgi body and then gets packed into (secretory) vesicles where it is now an active hormone with a detached peptide fragment
4. Release is signalled at the cell membrane and the hormone can travel in the bloodstream to the target cell(s)
35
How are peptide hormones stored?
Stored in large vesicles and released via exocytosis when calcium levels rise
- dense core vesicles containing peptide hormones
36
Describe the differences and similarities between peptide hormones and amino acid derivatives
Differences
- amino acid derivatives are synthesized by chromaffin cells in the cytosol/adrenal gland
- peptide hormones are synthesized in the RER and processed in the golgi body
Similarities
- both are stored in large vesicles and released via exocytosis when calcium levels rise
37
Simplify the path of a peptide hormone
1. Synthesis at RER
- prehormone -> prohormone
2. Packing at Golgi
- prohormone -> hormone
3. Storage in secretory vesicles
- hormones
**Signal comes in = mitochondria releases Ca2+ and exocytosis occurs when Ca2+ levels rise !
4. Secretion from cell to bloodstream
- hormones
38
Why are peptide hormones stored in vesicles?
These molecules lean towards HYDROPHILIC, therefore they CANNOT pass through the membrane on its own and requires the help of vesicles to pass through
39
Describe the differences between class 1, 2, and 3 hormones
Differences
1. Class 1 hormones are derived from larger proteins or modified amino acids
- stored in vesicles until increased Ca2+ levels occur
- hydrophilic
2. Class 2 hormones are derived peptide molecules (RER)
- stored in vesicles until increased Ca2+ levels occur
- hydrophilic
3. Class 3 hormones are derived from lipids (steroid hormones/cholesterol)
- freely diffuse across membrane but require carrier proteins to travel in bloodstream
- lipid soluble / hydrophobic
40
What are class 3 hormones?
lipid derivatives
- steroid hormones that are synthesized by modifications of cholesterol
41
Where are lipid derivatives synthesized?
- steroid hormones are synthesized by enzymes in the SER and in the mitochondria (NO RIBOSOMES - NO PROTEIN INVOLVED!)
42
Are steroid hormones lipid soluble or lipid insoluble?
LIPID SOLUBLE
43
How do steroid hormones differ from peptide hormones?
Peptide hormones tend to be hydrophilic, so they are lipid insoluble
But since steroid hormones are lipid soluble, they are synthesized on demand and must be transported in blood by carrier proteins
44
Steroid hormones are:
Hydrophilic or hydrophobic
Lipid soluble or lipid insoluble
Produced at SER or RER
Stored or synthesized on demand
1. Hydrophobic
2. Lipid soluble
3. Produced at SER
4. Synthesized on demand
45
What do lipid droplets (L) store?
Lipid-droplets (L) in steroid-secreting cells store PRECURSORS for steroid hormones, not the final hormones
46
How do steroid hormones travel through the blood to their target cells?
- synthesized on demand (not stored)
- freely move across the membrane in the ECF because they are lipid soluble/hydrophobic
- BUT must be bound to a carrier protein in order to get through in the bloodstream
- taken from high to low concentration of the messenger
- MOVES DOWN ITS CONCENTRATION GRADIENT FROM HIGH TO LOW CONCENTRATION WITH THE HELP OF CARRIER PROTEINS
47
What are two examples of class 1 hormones?
1. Epinephrine/adrenaline
2. Thyroid hormones
48
How are thyroid hormones synthesized?
Synthesized by modifying individual amino acids on a large protein
49
How do thyroid hormones differ from epinephrine/adrenaline?
Thyroid hormones form by adding iodine to a large protein called THYROGLOBULIN not from free amino acids
50
Trace the path of thyroid hormone synthesis
1. Iodide ions are actively transported into the cytoplasm
2. Iodide is converted to iodine and attached to tyrosine portion of thyroglobulin
3. Tyrosine molecules with attached iodine atoms become linked, forming molecules of thyroid hormones that remain in thyroglobulin (follicle cavity)
4. Thyroglobulin becomes the thyroid hormone
5. Thyroid hormone leaves the follicle cavity and goes back into the cell
- when follicle cells remove thyroglobulin from follicle cavity by endocytosis (back into follicle cell)
6. T3 and T4 (thyroid hormones) diffuse from the follicle cell to the bloodstream
7. Thyroid-binding globulins (TBGs) transport T3 and T4 molecules in bloodstream
51
When does the thyroglobulin protein become distinct thyroid hormones
Thyroid hormones are stored as PART of the THYROGLOBULIN PROTEIN then they DIFFUSE through the cell membrane once they are cleaved
52
T3 and T4 (thyroid hormones) are similar to which other type of hormone?
T3/T4 thyroid hormones are similar to class 3 hormones (lipi derivatives) in that they both move by FREE DIFFUSION and transport in blood via CARRIER PROTEINS
- require some help in the fluid blood tissue via carrier proteins
53
What is PTH?
A class 2 peptide hormone that is 84 amino acids in length
54
True or False:
PTH-secreting cells will have higher amounts of SER compared to RER
FALSE
PTH is a class 2 hormone, so it is synthesized at RER. Thus the cells that secrete PTH will have more RER than SER because we need those ribosomes on the endoplasmic reticulum to produce the peptide molecules for the hormone
55
True or False:
PTH will be released as soon as it is synthesized
FALSE
PTH will be stored in vesicles until Ca2+ levels rise
56
True or False:
PTH will be released via facilitated diffusion
FALSE
PTH is a class 2 hormone, so it is released by exocytosis
57
True or False:
PTH will be stored in vesicles and released in response to Ca2+ levels increasing
TRUE!
Just as amino acid derivatives (class 1), class 2 (PTH) will also be released as a response to increased Ca2+ levels
58
True or False:
PTH will require a carrier protein for transport in blood
FALSE
Class 2 hormones are HYDROPHILIC - only hydrophobic hormones (class 3) need carrier proteins to travel through the blood
59
What kind of hormones act through INTRACELLULAR RECEPTORS and ALTER GENE EXPRESSION
Lipid-soluble hormones (hydrophobic hormones)
- class 3 lipid derivatives
60
What are intracellular receptors and where are they located?
Intracellular receptors are located within the cytosol and/or the nucleus
61
Trace the path of steroid hormones through intracellular receptors and to the nucleus for gene expression alteration
1. Diffusion of steroid hormone through lipids of membrane into cell
- Hormones enters the cell membrane
2. Binding of hormone to cytoplasmic or nuclear receptors
- Binds to receptor
3. binding of hormone-receptor complex to DNA
- Receptors act as translation/transcription factors
4. Gene activation or deactivation
- Can turn on/off genes in protein translation/transcription
5. Can go into the nucleus and change the protein that expresses a certain gene
- Transcription and mRNA production occurs
- Translation and protein synthesis
Leads to alternation of cellular structure or activity which can affect the target cell's response
62
What are G-Protein coupled receptors (GPCRs) and how do they interact with hydrophilic hormones?
Hydrophilic hormones act through membrane-bound extracellular receptors of various types
- G-protein coupled receptors are metabotropic receptors (indirectly)
- signal biochemical reactions through soluble, mobile, second messenger molecules
63
Of the three classes of hormones, which two are hydrophilic hormones?
1. Peptide hormones
2. Amino acid derivatives
= both require GPCRs or enzyme receptors
64
How do hydrophilic hormones trigger a biochemical reaction with the help of GPCRs?
- interact with a family of G-proteins that act like molecular switches that tell cells to do specific things when they are activated
- can lead to activation of further enzymes / cellular activity / secondary messengers / intracellular calcium release / etc
- trigger response by binding to G-protein coupled receptors and causing activation for a reaction
65
Hydrophilic hormones are able to act through two types of membrane-bound receptors: What are they?
1. G-protein coupled receptors (GPCRs)
2. Enzyme-linked receptors
66
Summarize how hydrophilic hormones interact with G-receptors vs enzyme-linked receptors
1. GPCRs
- basically hydrophilic hormones interact with a protein receptor that will activate a G-protein
- then that G-protein will undergo biochemistry and cause another biochemical reaction to occur
2. Enzyme-linked receptors
- hydrophilic hormones attach to an inactive enzyme and activate it
- then substrate and effector can occur
67
Match the correct type of chemical messenger to its receptor:
1. Hydrophilic hormone
2. Hydrophobic hormone
a) G-protein coupled receptor
b) Intracellular receptor
c) Receptor-enzyme
d) Ligand-gated ion channel
a) G-protein coupled receptor
- hydrophilic hormones such as PTH (peptide hormone) would work with GPCRs
b) Intracellular receptor
- hydrophobic hormone
c) Receptor-enzyme
- hydrophilic hormones such as PTH (peptide hormone) would work with receptor-enzymes
d) Ligand-gated ion channel
- typically you don't see hormones activating through ligand-binding receptors (they are not neurotransmitters)
- ligand gated ion channels are usually used for action potentials
68
What is the key difference between intracellular receptors and G-protein receptors/receptor-enzymes
Intracellular receptors are suspended within the cell and not on the membrane
- they work with HYDROPHOBIC hormones (class 3)
G-protein and receptor-enzymes are attached to the membrane
- they work with HYDROPHILIC hormones (classes 1 and 2)
69
How do hormones participate in negative feedback loops?
Hormone acts as an effector, moving an altered variable back towards its set point
70
What are the four types of feedback loops that endocrine glands can perform?
1. Direct feedback loop
2. First-order feedback loop
3. Second-order feedback loop
4. Third-order feedback loop
71
Identify the sensor, integrator. and effector in a negative feedback loop for hormones
Stimulus
1. Sensor - endocrine gland
2. Integrator - endocrine gland
3. Effector - hormone
Response
72
What is a direct feedback loop?
Stimulus
1. Sensor - endocrine gland
2. Integrator - endocrine gland
3. Effector - hormone
Response
The hormone acts as an effector to produce a response that shuts off/counters the original stimulus
73
What is a first-order feedback loop?
Stimulus
1. Sensor - Sense organ
neuron
2. Integrator - Integrating centre
neuron
3. Effector - target organ
Response
Response produced by target organ shuts off the original stimulus
74
**What is a second-order feedback loop?
Stimulus
1. Sensor - Sense organ
neuron
2. Integrator - Integrating centre
neuron
3. Effector - endocrine gland
- circulatory system
- release of hormones
- target organ
Response triggered by hormones
Response produced by target organ shuts off the endocrine gland so that no more hormones are produced and also shuts down the original stimulus
75
**What is a third-order feedback loop?
Stimulus
1. Sensor - Sense organ
neuron
2. Integrator - Integrating centre
neuron
Endocrine gland 1
- releases hormones into circulatory system
- hormones cause a second endocrine gland to release hormones
Endocrine gland 2
- hormones are released into circulatory system
3. Effector - target organ
Response
Response produced by the second hormone shuts off the endocrine gland 2, which shuts off the endocrine 1, which shuts off the original stimulus
76
How do hormones participate in allostasis?
Allostasis = changing the set point in anticipation of a future need
77
How is sympathetic activation an example of allostasis with hormones?
Sympathetic activation including E secretion from the adrenal glands triggers the fight or flight response, which changes many physiological set points
78
True or False:
Target organs only have one type of receptor for one hormone at a time
FALSE
We have many different hormones, and so targets often have receptors to MORE THAN ONE HORMONE at the same time
79
What are the 8 organs that produce hormones with receptors in cells of the liver?
1. Pituitary gland
2. Adrenal
3. Ovary, placenta
4. Testes
5. Pancreas
6. Stomach
7. Thyroid and parathyroid
8. Pineal gland
80
Hormones on the same target can interact with each other in different ways: What are the four different effects?
1.
2.
3.
4.
81
What are additive effects?
Support each other = build upon each other
Hormone 1 and hormone 2 both interact with protein receptors to work together and increase cellular activity
82
What are antagonistic effects?
One increases, one decreases = opposing = subtract = cancel out
Hormone 1 interacts with the protein receptor and increases cellular activity
Hormone 2 interacts with the protein receptor and decreases cellular activity
= one increases activity and another decreases = cancels out
83
What are integrative effects?
Hormone 1 interacts with protein receptor and activates enzyme complex 1 = for one reaction
Hormone 2 interacts with protein receptor and activates enzyme complex 2
- triggers activity that is slightly different from hormone 1
Both responses work together towards a common goal even if they do not carry out the same pathways
84
What are permissive effects?
Two hormones, but only one receptor triggers a response
Hormone 1 binds to protein receptors and enables/gives permission to hormone 2 to bind to protein receptor and increase cellular activity
Hormone 2 does not happen unless hormone 1 is bound to its protein receptor
GIVES IT PERMISSION TO OCCUR ( ALLOWS IT )
