Exam 3: Ch 11 Hormones Flashcards
Endocrine glands =
ductless & secrete hormones
hormones
- regulatory molecules secreted into the bloodstream by endocrine glands
- go to target cells that contain receptor proteins for it
Main endocrine glands are
discrete organs whose primary function is to produce and secrete hormones
The endocrine system includes
many other organ whose primary function is NOT to release hormones but do Neurohormones
Neurohormones
are secreted into blood by specialized neurons (e.g. hypothalamus)
Chemical Classification of Hormones:
Amino Acid Base
- Amine
- Polypeptide(<100 aa)/protein(>100 aa)
- Glycoproteins
Chemical Classification of Hormones:
Steroid Base
Steroids
Amine hormones are
derived from the amino acids tyrosine or tryptophan
Amine hormones include
Include hormones secreted by adrenal medulla and pineal glands (NE, Epi,melatonin)
Polypeptide(<100 aa)/protein(>100 aa)
hormones are chains of amino acids (Include AntiDiruetic Hormone, GH, insulin, oxytocin, glucagon, Adrenocorticotrophic hormone (ACTH), PTH)
Glycoproteins =
long polypeptide chains connected to 1 or more carbohydrate (include LH, FSH, TSH)
Steroids
are lipids derived (as are thyroid hormones) from cholesterol so they can diffuse into cells (include testosterone, estrogen, progesterone &; cortisol);
Steroids made only by
adrenal cortex and gonads
Prohormones
are precursors of hormones; E.g. proinsulin
Prehormones
are precursors of prohormones; E.g. preproinsulin
Some hormones are inactive until
- activated by target cells
- E.g. thyroxine (T4) is inactive until converted to T3 in target cells
Both NS & endocrine system use
chemicals to communicate
Difference between NTs & hormones:
- transport in blood
- more diversity of effects in hormone targets
Common Aspects of Neural & Endocrine Regulation
- Some chemicals are used as hormones & NTs
(e. g. norepinephrine) - Targets for both NTs & hormones must have specific receptor proteins
- Must be way to rapidly inactivate both
Hormone Interactions
A tissue usually responds to # of hormones
2 hormones are synergistic if
- work together to produce an effect
- produce a larger effect together than individual effects added together
A hormone has permissive effect if
if it enhances responsiveness of a target organ to 2nd hormone
antagonistic
If action of 1 hormone inhibits effect of another
Normal tissue responses are produced
only when hormones are in physiological range
High (pharmacological) doses
- can cause # of side effects; probably by binding to receptors of other hormones
Priming effect (upregulation)
occurs when a hormone induces more of its own receptors in target cells; results in greater response in target cell
Desensitization (downregulation)
occurs after long exposure to high levels of polypeptide hormone
Subsequent exposure to high levels of polypeptide hormone
produces a lesser response due to decrease in # of receptors on targets
Most peptide hormones have
pulsatile secretion
pulsatile secretion
(in spurts rather than continuously) which prevents downregulation
Target cell receptors show
- specificity (specific receptors)
- high affinity (high bonding strength), &
- low capacity (saturation) for a hormone
Lipid hormones have
receptors in target cell’s cytoplasm &/or nucleus because can they diffuse through plasma membrane
Receptors for water-soluble hormones are
on surface of target cell
Lipid hormones
(steroids and thyroid hormones) travel in blood attached to carrier proteins
Lipid hormones dissociate from
carriers to pass thru plasma membrane of target
Lipid hormones receptors are called
nuclear hormone receptors
Nuclear Hormone Receptors
serve as transcription factors (Activate transcription) when bound to hormone ligands
Nuclear Hormone Receptors Constitute a
a “superfamily” composed of steroid family & thyroid hormone family
Nuclear Hormone Receptors have
ligand (hormone)-binding & DNA-binding domains
Nuclear Hormone Receptors bind
hormone & translocate to nucleus
Nuclear Hormone Receptors binds to
hormone-response element (HRE) on DNA located adjacent to target gene