Endocrinology overview Flashcards
Endocrine glands:
specialized groups of cells that release hormones
internally within the body (typically into inters\al space/extracellular
fluid for entry into the bloodstream)
what is Molecular endocrinology
study of the molecular basis for the
synthesis, ac)ons and regula)on of hormones and their receptors
Hormones
chemicals that act as signaling molecules to traffic specific
informa)on from one cell to another
How do hormones travel?
• 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.
what can a single hormone do?
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.
12 general actions of hormones
- 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
Dysregulation / dysfunction of hormone levels and in cellular responses
Dysregulation of hormone levels or dysfunction in cellular responses to
hormones can cause pathological changes (i.e., an endocrine disease or
endocrine disorder)
how are Hormone levels in circulation (and hormone actions) tightly
regulated.
This is accomplished by controlling hormone
synthesis/precursor processing/release; controlling ability of hormones to
access target cells; and through hormone removal (degradation)
can hormones regulate their own production ?
Hormones can regulate their own production and release
as well as that for other hormones
Juxtacrine
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)
Autocrine
ligand is released by the signaling
cell, then acts on the same cell that produced it
Paracrine:
ligand is released by the signaling
cell, then acts on a nearby cell
Endocrine
ligand is transported by the circulatory system (acts on a distant cell)
Additional organs that also produce hormones
Kidney Heart Adipose tissue Gastrointestinal tract Liver Bone
Classic” endocrine organs contain..
contain ductless glandular structures (groups of cells) that release hormones into the extracellular space where they eventually access circulating plasma
”nontraditional” endocrine organs
also secrete hormones (with important
physiological effects) into the bloodstream
hypothalamus
The hypothalamus is a primary link
between the two systems
Nervous system
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
Key dif in endocrine and nervous system
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
Nervous system vs endocrine system
- how are signals transmitted
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)
Hormones can act in a ___ and __ ….
Hormones can act in autocrine or paracrine fashion without entering circulation, or reach their target cells via the bloodstream (endocrine)
Neurotransmitters
Neurotransmitters: very
targeted/localized effects
Cytokines
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
what have similarties in function to peptide hormone receptors
Major histocompa)bility complex (MHC) class
receptors and Toll-like receptors have
similari)es in func)on to pep)de hormone
receptors
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)
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)
