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Chapter 16 - The Endocrine System part 1
Terms in this set (81)
The endocrine system acts with what to do what?
The endocrine system acts with the NERVOUS SYSTEM to coordinate and control and integrate activity of body cells
What does the endocrine system influence?
It influences metabolic activities via hormones
- compared to nervous system
- influences metabolic activities
- transported in the blood
- responses slower but lasts longer than the nervous system
What pathway do hormones use and why?
through the blood to make sure the hormones are spread evenly throughout the body
What is Endocrinology?
the study of hormones and endocrine organs
What does the endocrine system control and integrate? (5)
2. Growth and Development
3. Maintenance of electrolyte, water, and nutrient balance of blood
4. Regulation of cellular metabolism and energy balance
5. Mobilization of body defenses
What are exocrine glands and what do they do?
Glands the produce non hormonal substances (sweat and saliva) and use ducts to carry secretions to membrane surface
What are endocrine glands and what do they do?
glands the produce hormones from the surface and lack ducts
Name 5 examples of endocrine glands:
1. Pituitary gland
2. thyroid gland
3. Parathyroid gland
4. Adrenal gland
5. Pineal gland
What kind of organ is the hypothalamus?
A Neuroendocrine organ
What glands (3) have exocrine and endocrine functions?
What tissues and organs produce hormones? (6)
1. Adipose cells
3. Cells in the walls of the small intestines
Pineal gland location
Located in the brain behind the hypothalamus
Pituitary Gland location
Thyroid Gland location
Parathyroid Gland Location
Adrenal Gland Location
What are the 3 chemical messengers of the endocrine system?
What are hormones?
- Long-distance chemical signals
- Travel in blood or lymph
What are Autocrines?
A chemical messenger that exert effects on same cells that secrete them
* not considered part of endocrine system
What are Paracrines?
Locally acting chemical messenger that affect cells other than those that secrete them
*not considered part of endocrine system
What are the 3 major classes of molecules function as hormones in vertebrates?
1. Polypeptides (proteins and peptides)
2. Amines derived from amino acids
3. Steroid hormones
What are target cells?
Cells that hormones can affect due to their receptors for that specific hormones
What may hormone action on target cells cause? (5)
1. to alter plasma membrane permeability/membrane potential by opening or closing ion channels
2. Stimulate synthesis of enzymes or other proteins (transcription/translation)
3. Activate or deactivate enzymes
4. Induce secretory activity
5. stimulate mitosis (cell division)
What are the two ways that hormones act and what are the 2 depending factors?
Factors: chemical nature and receptor location
1. Water-soluble hormones
2. Lipid-soluble hormones
What are water-soluble hormones and what do they do?
They are: All amino acid-based hormones EXCEPT thyroid hormones
- They act on plasma membrane receptors
- act via G protein second messengers
** Cannot enter cell w/out receptor
What are lipid-soluble hormones and what do they do?
They are: Steroid and thyroid hormones
- They act on intracellular receptors that directly activate genes
** They can enter the cell
Which hormones exert their effects through second-messenger systems?
Amino acid-based hormones (except thyroid hormone)
Which hormones exert their effects through single messenger systems?
What are the 2 main second-messenger systems?
- cyclic AMP
- PIP2 - Calcium
What are the 5 steps for the Cyclic AMP (cAMP) signaling mechanism?
1. Hormone (first messenger) binds to receptor
2. Receptor activates a G protein
3. G protein activates or inhibits effector enzyme Adenylate cyclase
4. Adenylate cyclase then converts ATP to cAMP (second messenger) indicates a reaction happening
5. cAMP activates protein kinases that phosphorylate (add a phosphate) to other proteins thereby activating them
What are the 1st and 2nd messengers of the cyclic AMP messenger system?
1st: Hydrophilic Hormones
What is the role of the G protein in the cyclic AMP messenger system?
G protein activates or inhibits effector enzyme adenylate cyclase
What is the role of adenylate cyclase in the cyclic AMP messenger system?
It is activated by the G protein and converts ATP to cAMP
** this indicates that a reaction is happening
** it is an enzyme
What is the role of cAMP in the cyclic AMP messenger system?
cAMP activates protein kinases that phosphorylate (add a phosphate) to other proteins thereby activating them
What are the 5 steps for direct gene activation? What hormones do this?
Lipid soluble steroid hormones and thyroid hormones
1. The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor
2. The receptor- hormone complex enters the nucleus
3. The receptor- hormone complex binds a specific DNA region
4. Binding initiates transcription of the gene to mRNA
5. The mRNA directs protein synthesis
What is the first step of direct gene activation?
Hormones diffuse into target cell and bind with intracellular receptors creating the Receptor-hormone complex
What is the role of the receptor-hormone complex?
Its role is to enter the nucleus, bind to a specific region of DNA, and initiate DNA transcription
What is created during direct gene activation?
DNA transcription produces mRNA which is then translated into specific proteins
What controls hormone levels in the blood?
Negative feedback system.
- increased hormone effects on target organs can inhibit further hormone release
What type of glands release hormones?
Endocrine glands are stimulated to synthesize and release hormones
What 3 stimuli causes endocrine glands to release hormones?
1. Humoral stimuli
2. Neural stimuli
3. Hormonal stimuli
What causes Humoral stimuli and what is the effect?
- Changing blood levels of ions and nutrients
- Directly stimulates secretion of hormones
What is an example of Humoral Stimuli
Ca2+ in the blood
- declining concentrations stimulates parathyroid glands to secrete PTH
What is neural stimuli?
Nerve fibers stimulate hormone release
How does neural stimuli work?
Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines
What does neural stimuli stimulate and what is secreted?
Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines (epinephrine and nonepinephrine)
What is hormonal stimuli?
Hormones stimulate other endocrine organs to release their hormones
What do hypothalamic hormones stimulate?
Hormone stimulates the release of most anterior pituitary hormones
What do anterior pituitary hormones stimulate?
Hormones stimulates targets to secrete still more hormones
What can the nervous system contribute to endocrine glands? (3)
The nervous system can:
- make adjustments to hormone levels
- modify stimulation or inhibition of endocrine glands
- override normal endocrine controls
Target cell receptors
Target cells must have specific receptors to which hormones bind
What are the 3 factors that affect target cell activation?
1. Blood levels of hormone
2. Relative number of receptors on/in target cell
3. Affinity (strength) of binding between receptor and hormone
What affects receptor amounts?
Amount of hormone can influence number of receptors for that hormone
What is up-regulation?
Target cells form more receptors in response to low hormone levels
What is down-regulation?
Target cells lose receptors in response to high hormone levels
*desensitizes the target cells to prevent them from overreacting to persistently high levels of hormone
What 2 ways do hormones circulate in the body?
they circulate in blood wither free or bound (a carrier)
What hormones are attached to a carrier and what is that carrier?
Steroids and thyroid hormone are attached to plasma proteins
What hormones circulate without carriers?
All hormones other than steroids and thyroid hormones circulate without carriers
What does concentration of circulating hormones reflect?
1. Rate of release
2. Speed at which it is inactivated and removed from the body
How are hormones removed from the blood?
Degrading enzymes or kidneys or liver
What is half-life?
Time required for level of hormone in blood level to decrease by half.
** Varies anywhere from fraction of a minute to a week, depending on hormone
What are the response times for hormones?
They have different response times:
- Some respond immediately
- Some take hours to days
- Some are inactive until they enter target cells
What are the duration of response for hormones?
Ranges from 10 seconds to several hours
What decides half-life, onset, and duration for a hormone?
Whether the hormone is water or lipid soluble
Lipid - soluble hormone sources?
Adrenal cortex, gonads, and thyroid glands
Water- soluble hormone sources?
All endocrine glands other than the adrenal cortex, gonads, and thyroid glands
How are lipid - soluble hormones transported in blood? half life in blood?
They are bound to plasma proteins and have a long half-life metabolized by the liver
How are water - soluble hormones transported in blood? half life in blood?
They are free in plasma and have a short half-life, removed by kidneys
Where are receptors found in lipid- soluble hormones and what mechanism of action is used at the target cell?
Receptors are located inside the cell and activates genes causing synthesis of new proteins
Where are receptors found in water- soluble hormones and what mechanism of action is used at the target cell?
Receptors are located on the plasma membrane and act through second-messenger systems
What is permissiveness?
One hormone cannot exert its effects without another hormone being present
What is an example of permissiveness?
Reproductive hormones need thyroid hormone to have effect
What is synergism?
More than one hormone produces same effects on target cell, causing amplification
What is an example of synergism?
Glucagon and epinephrine both cause liver to release glucose
What is antagonism?
One or more hormones oppose(s) action of another hormone
What is an example of antagonism?
Insulin and glucagon
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