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Biol 432 > Endocrinology overview > Flashcards

Endocrinology overview Flashcards

1
Q

Endocrine glands:

A

specialized groups of cells that release hormones
internally within the body (typically into inters\al space/extracellular
fluid for entry into the bloodstream)

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2
Q

what is Molecular endocrinology

A

study of the molecular basis for the

synthesis, ac)ons and regula)on of hormones and their receptors

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3
Q

Hormones

A

chemicals that act as signaling molecules to traffic specific
informa)on from one cell to another

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4
Q

How do hormones travel?

A

• Hormones travel through a medium, such as the extracellular fluid or the
bloodstream.
• Therefore, can transmit information to distant parts of the body,
and cause responses far from the point of secretion.

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5
Q

what can a single hormone do?

A

A single hormone might regulate multiple physiological processes
(and have distinct effects in different target cells).
• Physiological process might be regulated by multiple different hormones.

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6
Q

12 general actions of hormones

A 
- fetal development
• cell growth (and cancer)
• digestion
• metabolism of carbohydrates, lipids, proteins/amino acids, nucleic acids
• ion and water balance (minerals and water)
• renal function
• cardiovascular func:on and circulatory system
• respiration
• skeletal function
• reproductive function
• immune system func:on
• central nervous system function
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7
Q

Dysregulation / dysfunction of hormone levels and in cellular responses

A

Dysregulation of hormone levels or dysfunction in cellular responses to
hormones can cause pathological changes (i.e., an endocrine disease or
endocrine disorder)

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8
Q

how are Hormone levels in circulation (and hormone actions) tightly
regulated.

A

This is accomplished by controlling hormone
synthesis/precursor processing/release; controlling ability of hormones to
access target cells; and through hormone removal (degradation)

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9
Q

can hormones regulate their own production ?

A

Hormones can regulate their own production and release

as well as that for other hormones

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10
Q

Juxtacrine

A

contact-dependent signaling
between neighboring cells (e.g., via gap
junctions, or between a membrane ligand of
one cell and the cell surface receptor or cell
adhesion molecule of an adjacent cell)

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11
Q

Autocrine

A

ligand is released by the signaling

cell, then acts on the same cell that produced it

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12
Q

Paracrine:

A

ligand is released by the signaling

cell, then acts on a nearby cell

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13
Q

Endocrine

A 
ligand is transported by the
circulatory system (acts on a distant cell)
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14
Q

Additional organs that also produce hormones

A 
Kidney
Heart
Adipose tissue
Gastrointestinal tract
Liver
Bone
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15
Q

Classic” endocrine organs contain..

A 
contain ductless
glandular structures (groups of cells) that
release hormones into the extracellular
space where they eventually access
circulating plasma
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16
Q

”nontraditional” endocrine organs

A

also secrete hormones (with important

physiological effects) into the bloodstream

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17
Q

hypothalamus

A

The hypothalamus is a primary link

between the two systems

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18
Q

Nervous system

A 
also communicates
between cells via chemical
messengers (ligands & receptors)
• Some chemical messengers (e.g.,
norepinephrine) can be considered as
both neurotransmitters and
hormones, depending on where they
are secreted and act
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19
Q

Key dif in endocrine and nervous system

A

unlike the endocrine system
(open system of circulating plasma carries
signals), the nervous system uses a combination
of electrical action potentials (along neuron)
plus neurotransmitters across small intercellular
distances

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20
Q

Nervous system vs endocrine system

- how are signals transmitted

A 
Nervous system: signals are transmitted
much faster (response times in seconds),
more specifically targeted, and generally shorter-lived

Endocrine system: wider range of signal distribution,
and tends to have higher-affinity receptors (therefore
can respond to lower concentrations of ligand), but
takes longer for signals to be spread (response time on
the order of minutes-hours)

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21
Q

Hormones can act in a ___ and __ ….

A 
Hormones can act in autocrine
or paracrine fashion without
entering circulation, or reach
their target cells via the
bloodstream (endocrine)
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22
Q

Neurotransmitters

A

Neurotransmitters: very

targeted/localized effects

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23
Q

Cytokines

A 
are also important cell signaling
molecules (autocrine, paracrine, and
juxtacrine signaling func)ons) – but are
produced by a broad range of cells, and often
at lower concentrations than hormones
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24
Q

what have similarties in function to peptide hormone receptors

A

Major histocompa)bility complex (MHC) class
receptors and Toll-like receptors have
similari)es in func)on to pep)de hormone
receptors

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25
Cross-talk
the immune system is highly receptive to endocrine signals, and endocrine tissues are affected by immune modulators, such as cytokines e.g., immune cytokines cause release of adrenocor3cotropin (ACTH), prolac3n, and Gonadotrophin-releasing hormone (GnRH)
26
Aside from their functions, other ways to classify hormones… (7)
• By where they’re produced/secreted • By their receptor sub-type • By whether they act as a receptor agonist or receptor antagonist • By key intracellular messengers (e.g., cAMP, cGMP, inositol trisphosphate (IP3), Ca2+) & effector mechanisms in their signal transduc4on pathway • By their chemical structure (protein, pep5de, amino acid deriva5ve, monoamine, steroid, or fa8y acid deriva5ve) • By their solubility • By their receptor loca4on (cell surface vs. cytosolic/nuclear)
27
receptor sub-types (2)
Cell surface receptors: G-protein-coupled receptors, Receptor-enzymes, Type I cytokine receptors, Ligand-regulated transporters • Cytosolic or nuclear receptors (intracellular receptors)
28
Biological activity of a hormone depends on...
Biological activity of a hormone depends on its interactions with specific receptors Ligand binding to a specific receptor: causes signal transduction responses (effector systems) in the target cell
29
Receptor agonist
activates/triggers the effector mechanisms and elicit a biological response binds to the receptor - Often think of think when thinking of hormone signalling
30
Receptor antagonist:
binds to the receptor but does not activate the effector mechanisms; blocks/dampens a biological response (e.g., by occupying the receptor/blocking access of an agonist)
31
Partial agonist-partial antagonist
limited ability to activate the effector mechanisms (response is < half of a full agonist) has a less than half full agonist effect . By blocking full response you are damping system so its also antagonist
32
Mixed agonist-antagonist:
act as agonist in some cases, antagonist in others (depending on dose, cell type, and receptor)
33
Hormone chemical structures | 4
``` • Proteins & peptides - Might be glycosylated and/or dimerized to generate their full biological activity • Amino acid derivatives, monoamines • Steroids (derived from cholesterol) • Fatty acid derivatives Different synthesis & degradation pathways ```
34
Proteins & peptides
``` • Encoded by cellular genes; Increased gene expression is o^en a key part of biosynthesis • Precursor processing, post-translational modification, and/or assembly often required to generate mature, active forms • Hydrophilic • Often stored in secretory vesicles/granules in endocrine cells • Generally act via cell surface receptors (can’t enter the cell) ```
35
Amino acid derivatives, | monoamines
``` Many are derived from amino acids; Sequestering of precursors and increased activity of enzymes responsible for hormone production is often a key part of biosynthesis • Precursor processing, posttranslational modification, and/or assembly often required to generate mature, active forms • Monoamines are hydrophilic; Thyroid hormones are hydrophobic • Monoamines generally act via cell surface receptors; Thyroid hormones generally act via nuclear receptors ```
36
Steroids | derived from cholesterol
``` Derived from cholesterol; Sequestering of cholesterol and increased activity of enzymes responsible for hormone production is often a key part of biosynthesis • Hydrophobic (pass through lipid membranes; not stored in secretory vesicles: synthesized on demand) • Generally act via nuclear receptors, but some activate cell surface receptors ```
37
Fatty acid derivatives
``` Derived enzymatically from fatty acids • Hydrophobic (synthesized on demand) • Very short half-life (autocrine or paracrine signalling; not long-range)… “hormone-like” • Prostaglandins: involved in mediating responses to injury/illness (control inflammation, blood flow, etc.) • Generally act via cell surface receptors ```
38
Additivity
Effects of two (or more) hormones together is equivalent to the sum of the effects of those hormones alone 1+1 = 2 Example: Combined effect (on blood glucose) of Glucagon + Epinephrine together
39
Synergy
Effects of two (or more) hormones together is greater than the sum of the effects of those hormones alone 1 + 1 > 2 Example: Combined effect (on blood glucose) of Glucagon + Epinephrine + Cortisol together
40
Hormone levels and actions must be tightly regulated. Accomplished by:
* Controlling hormone synthesis/precursor processing/release * Controlling ability of hormones to access target cells/receptors * Hormone metabolism
41
Controlling hormone synthesis/precursor processing/release
• Synthesis (e.g., gene expression, precursor availability, enzyme activity) • Processing (e.g., prohormone conversion/cleavage, modification or assembly) • Secretion (controlled by signaling events triggered by exogenous regulators/2nd messengers)
42
Controlling ability of hormones to access target cells/receptors
* Hormone transport (e.g., blood binding proteins) * Changes to receptor expression or cellular localization * Interactions with other regulatory proteins/hormones (e.g., receptor antagonists)
43
Hormone metabolism
* Conversions/structural changes that increase or decrease activity of hormone * Degradation of ligand (and/or receptor) over time
44
Many hormone levels are controlled ___ or ___ by the biological activity they control (output)
directly, indirectly
45
Negative feedback loop:
``` Response tends to return variable back to original level (holding a set point to maintain homeostasis) ```
46
Positive feedback loop:
``` Response changes further changes from a set point… amplifies changes. Specific threshold or separate input is needed to limit the positive feedback loop. ```
47
Feedback loop
effector -> variable (External influence | or disturbance) -> sensor -> back to effector
48
There may be ___ in a feedback loop
multiple steps/levels
49
The “product” feeding back can be levels of ....
an inorganic ion | or metabolite, or a hormone in an endocrine cascade
50
Tropic hormone:
a hormone that cause the release of another hormone
51
Input
Input: change in extracellular environment or innervation
52
Only ___ glands involved (no CNS) - Feedback loops
Only peripheral endocrine glands involved (no CNS)
53
Hormones in plasma
either free form (= biologically active form) or bound to other molecules, e.g. blood binding proteins
54
Blood binding proteins affect the controlled release | and stability of the pool of hormones by
Make the hormone soluble in plasma (e.g., steroid hormones are hydrophobic – low solubility in aqueous solutions on their own) • Provides reservoir of hormone that exchanges with free hormone fraction (making hormone pool more stable, less dependent on synthesis/release) - More uniform/distant distribution - Slowing hormone metabolism/breakdown
55
what is not limited to hydrophobic hormones
Blood binding proteins affect the controlled release and stability of the pool of hormones e.g., Growth Hormone and Insulin-like growth factor 1 are proteins with specific blood binding proteins.
56
Albumins:
a family of water-soluble globular | proteins
57
Serum albumin
• Produced by the liver • The most abundant blood protein in mammals • Binds to a range of molecules (with varying degrees of affinity), including steroids, fatty acids, & thyroid hormones
58
Globulins
another family of globular proteins
59
Interactions between hormones and their receptors depends on:
* Number of receptors * Affinity of the hormone for the receptor * Concentration of circulating hormone
60
Regulation at the level of the receptors is also an important point of endocrine function control..
Increasing or decreasing receptor synthesis • Internalization vs. cell membrane localization of cell surface receptors • Desensitization of receptors (“uncoupled” from signal transduction pathway, due to such mechanisms as phosphorylation of the receptor)
61
Hormone receptors vs. blood binding proteins - Concentration
Receptor -low Blood Binding Protein -high
62
Hormone receptors vs. blood binding proteins - binding affinity
Receptor -high Blood Binding Protein -low
63
Hormone receptors vs. blood binding proteins - specificity
Receptor -high Blood Binding Protein -low
64
Hormone receptors vs. blood binding proteins saturability at physiological concentrations
Receptor - yes Blood Binding Protein - no
65
Hormone receptors vs. blood binding proteins reversibility
Receptor - yes but not as readily Blood Binding Protein - yes
66
Hormone receptors vs. blood binding proteins signal transduction
Receptor - yes Blood Binding Protein - no
67
Endocrine system
``` Coordinates and integrates the activities of physiological processes in diverse target cells, in response to environmental and internal changes ```

Biol 432 (8 decks)

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