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HMS302 Endocrine System > Endocrine System Overview > Flashcards

Endocrine System Overview Flashcards

1
Q

Body contains 2 kinds of glands:

A
  • Exocrine glands
  • Endocrine glands
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2
Q

Exocrine glands
(exo - outside)

A

Secrete their products into ducts that carry the secretions into body cavities, into a lumen of an organ, or to other surfaces of the body.

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3
Q

Endocrine glands
(endo - within)

A

Secrete their products (hormones) into the interstitial fluid surrounding the secretory cells rather than into the ducts.

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4
Q

Endocrine gland + Hormone secreting cells =

A

Endocrine System

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5
Q

Classical endocrine glands - definition

A

Glands that have one function, which is to synthesize & release hormones into the bloodstream.

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6
Q

Classical endocrine glands - examples

A
  • Pituitary
  • Thyroid
  • Parathyroid
  • Adrenal glands
  • Pineal glands
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7
Q

The 2 major regulatory systems in the body

A
  • Neural system
  • Endocrine system
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8
Q

Hormones released from nerve endings

A

Neuro-hormones

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9
Q

Similarities between Neural & Endocrine systems

A
  • Both react to stimuli
  • Both help maintain homeostasis
  • Both are systems of the body than send messages
  • Hypothalamus is a link between the 2 systems
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10
Q

Differences between Neural & Endocrine system

A

Nervous System
- Mediator molecules = neurotransmitters released locally in response to nerve impulses.
- Site of mediator action = localized, binds to receptors in post-synaptic membranes.
- Types of target cells = muscle cells, gland cells, & other neurons.
- Onset of action = typically within milliseconds
- Duration of action = milliseconds

Endocrine System
- Mediator molecules = hormones delivered to tissues throughout the body by the blood.
- Site of mediator action = widespread, binds to receptors on or in target cells.
- Types of target cells = cells throughout the body
- Onset of action = seconds to hours to days
- Duration of action = generally longer

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11
Q

Hormones like _______ influence their ______ _________ by chemically bindings to specific ___ _______.

A

Neurotransmitter, target cells, protein receptors.

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12
Q

Only the _______ cells for a given hormone have ______ that bind & recognize this hormone.

A

target, receptors

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13
Q

Target cells has _______ to _______ receptors for a particular hormone.

A

2,000 to 100,000 receptors

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14
Q

Down-regulation

A

It is when the number of receptors decreases in response to high levels of a hormone, making the target cell less sensitive to the hormone.
- decreases cellular activity

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15
Q

Up-regulation

A

It is when the number of receptors increases in response to low levels of a hormone, making the target cell more sensitive to the hormone.
- increases cellular activity

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16
Q

Most endocrine hormones are _________ hormones

A

circulating

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17
Q

Circulating hormones

A
  • Hormones that travel in the blood & act on distant target cells.
  • Endocrines
  • Inactivated by the liver & excreted by the kidneys.
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18
Q

Local hormones

A

Hormones that act locally (neighboring or same cells) without first entering the bloodstream.
- affect target cells close to their release site.
- Paracrine & Autocrines
- inactivated quickly

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19
Q

In cases of liver & kidney failure, hormones may?

A

Build up in the blood

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20
Q

Paracrine
(Para = beside or near)

A

Hormones that act on neighboring cells

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21
Q

Autocrine
(Auto = self)

A

Hormones that act on the same cell that secreted them.

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22
Q

Functions of hormones

A

(1) Help regulated:
- chemical composition & interstitial fluid
- metabolism & energy balance
- contraction of smooth & cardiac muscle fibers
- glandular secretions
- some immune system activities
(2) Control growth & development
(3) Regulate the operation of reproductive systems
(4) Help establish circadian rhythms.

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23
Q

2 types of chemical classes of hormones

A
  1. Lipid-soluble hormones
  2. Water-soluble hormones
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24
Q

Lipid-soluble hormones

A
  • steroid hormones
  • thyroid hormones
  • nitric oxide
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25
Water-soluble hormones
- amine hormones - peptide hormones - protein hormones - eicosanoid hormones
26
Steroid hormones
- derived from cholesterol - each steroid hormone is unique due to the presence of different chemical groups attached at various sites on the 4 rings at the core of it's structure.
27
Thyroid hormones
- T3 & T4 - the presence of the 2 benzene rings makes these molecules very lipid soluble.
28
Nitric Oxide (NO)
- both a hormone & neurotransmitter - produced by endothelial cells that lines blood vessels & causes vasodilation.
29
Amine hormones
- called amines because they retain an amino group (-NH3+).
30
Peptide & Protein Hormones
- amino acid polymers - smaller peptide hormones consist of chains of 3 - 49 amino acids. - larger protein hormones include 50 - 200 amino acids.
31
Eicosanoid hormones
- Eicos = 20 forms oid = resembling - derived from arachidonic acid (20-carbon fatty acid). - circulating & local hormones - 2 major kinds: 1. Prostaglandins (PGs) 2. Leukotrienes (LTs)
32
Hormone transport in the blood
- Water-soluble hormones = circulate in the watery blood plasma in a free form. - most Lipid-soluble hormones = are bound to transport proteins.
33
Transport proteins are synthesized by?
cells in the liver
34
Transport proteins have 3 functions:
1. They make lipid-soluble hormones temporarily water-soluble, thus increasing their solubility in blood. 2. They delay the passage of small hormone molecules through the filtering mechanism in the kidneys ------ this slows down the rate of hormone loss in the urine. 3. They provide a ready reserve of hormones, already present in the bloodstream.
35
___________ of the molecules of a lipid-soluble hormone aren't bound to a transport protein.
0.1 - 10%
36
What happens to the free fraction (0.1 - 10%) of a lipid-soluble hormone?
It diffuses out of capillaries, binds to receptors, & triggers responses. - afterwards, transport proteins release new ones to replenish (fill) the free fraction.
37
Why are steroids & thyroid hormones effective when taken by mouth?
This is because they aren't split apart during digestion & they easily cross the intestinal lining.
38
Why are peptide & protein hormones not effective when taken orally?
This is because digestive enzymes will destroy them by breaking their peptide bonds. Instead they are taken by injection.
39
The response to a hormone depends on both the _________ itself & the _______ cell.
hormone, target
40
Hormonal effects (4)
- Changes the permeability of the plasma membrane - Stimulates the transport of a substance into or out of the target cells - Alters the rate of specific metabolic reactions. - Causes contraction of smooth muscle or cardiac muscle.
41
Receptors for lipid-soluble hormones
inside target cells
42
Receptors for water-soluble hormones
outside the target cells = part of the plasma membrane of target cells
43
Action of lipid-soluble hormone (4) - 1st
(1) A free lipid-soluble hormone molecule diffuses from the blood, through the lipid bilayer of the plasma membrane into a cell.
44
Action of lipid-soluble hormone (4) - 2nd
(2) If the cell is a target cell, the hormone binds to & activates receptors located within the cytosol or nucleus. The activated receptor-hormone complex then alters gene expression = which turns specific genes of the nuclear DNA on or off.
45
Action of lipid-soluble hormone (4) - 3rd
As the DNA is transcribed, new mRNA forms, leaves the nucleus, & enters the cytosol. There it directs synthesis of a new protein, often an enzyme, on the ribosome.
46
Action of lipid-soluble hormone (4) - 4th
The new proteins alter the cell's activity & causes the responses typical of that hormone.
47
Action of water-soluble hormones (6) - 1st
(1) Binding of hormone (1st messenger) to its receptor (outside the cell) activates G protein, which activates adenylate cyclase.
48
Action of water-soluble hormones (6) - 2nd
(2) Activated adenylate cyclase converts ATP to cAMP.
49
Action of water-soluble hormones (6) - 3rd
(3) cAMP serves as a 2nd messenger to activate protein kinases.
50
Action of water-soluble hormones (6) - 4th
(4) Activated protein kinases phosphorylate cellular proteins.
51
Action of water-soluble hormones (6) - 5th
Millions of phosphorylated proteins cause reactions that produce physiological responses.
52
Action of water-soluble hormones (6) - 6th
Phosphodiesterase inactivates cAMP
53
Protein Kinases
Are intracellular enzymes that: - regulate cell growth & proliferation - triggering & regulating immune responses.
54
Protein kinases are important therapeutic targets in cancer because?
Of their critical role in signaling mechanisms that drive malignant cell characteristics.
55
Explain the statement - different protein kinases exist within different target cells & within different organelles of the same target cell.
Meaning - 1 protein kinase might trigger glycogen synthesis, a 2nd might cause the breakdown of triglyceride, & a 3rd may promote protein synthesis, & so forth.
56
Examples of second messengers
- Calcium ions (Ca2+) - CGMP = cyclic guanosine monophosphate - IP3 = inositol triphosphate - DAG = diacylglycerol
57
Hormones that bind to plasma membrane receptors can? Give an example
induce their effects at very low concentrations, & initiate a cascade or chain reaction where each step amplifies the initial effect. Example = the binding of a single molecule of epinephrine to its receptor on a liver cell may activate a hundred or so G proteins, each of which activates an adenylate cyclase molecule.
58
The responsiveness of a target cell to a hormone depends on: (3)
- the hormone's concentration in the blood - abundance of the target cell's hormone receptors. - influences exerted by other hormones
59
A target cell responds more vigorously when: (3)
- level of a hormone rises - has more receptors (up-regulation) - simultaneous or recent exposure to a 2nd hormone.
60
Permissive effect - define & example
- The presence of one hormone is required in order for another hormone to exert its full effects on a target cell. (increases the # of receptors for the other hormone) - e.g. epinephrine alone only weakly stimulates lipolysis but when small amounts of thyroid hormones are present, the same amount of epinephrine stimulates lipolysis much more powerfully.
61
Synergistic effect - define & example
When the effect of 2 hormones acting together is greater than the effect of each hormone acting alone. - e.g. normal development of oocytes in the ovaries requires both FSH (from the anterior pituitary) & estrogens (from the ovaries). Neither hormone alone is sufficient.
62
Antagonistic effect - define & example
When one hormone opposes the actions of another hormone. - e.g. insulin & glucagon - insulin = promotes synthesis of glycogen by liver cells. - glucagon = stimulates breakdown of glycogen in the liver.
63
The release of most hormones occurs in _____ ____ with _____ or _____ secretion between ______.
short bursts, little, no, bursts.
64
When stimulated, an endocrine gland will release its hormone in more _____ _____, _____ the concentration of the hormone in the blood.
frequent bursts, increasing
65
Hormone secretion is regulated by? (3)
- signals from the nervous system - chemical changes in the blood - other hormones
66
If the response reverses the stimulus, a system is operating by?
negative feedback
67
If the response enhances or intensifies the stimulus, a system is operating by?
positive feedback

HMS302 Endocrine System (14 decks)

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