Chapter 5: Hormones and the Brain Flashcards
Hormones
are chemicals secreted by cells in one part of the body that travel through the bloodstream to act on targets in other parts of the body
Endocrine Glands
release hormones within the body
Exocrine Glands
use ducts to secrete fluids such as tears and sweat outside the body
Endocrine
a hormone is released into the bloodstream to act on target tissues
Synaptic (Neuocrine)
chemical release and diffusion across a synapse
Autocrine
released chemical acts on the releasing cell
Paracrine
the released chemical diffuses to nearby target cells
Pheromone
hormones used to communicate between individuals of the same species; pheromones are released into the environment.
Allomones
allomones are chemicals released by one species to affect the behavior of another species
Neuroendocrine Cells
are neurons that release hormones into the blood
Neuropeptides (Peptides used by Neurons)
can act as neuromodulators and alter sensitivity to transmitters
can modify the reactivity of cells to specific transmitters, they act more slowly than neurotransmitters and have longer lasting effects.
Chemical Structure of Hormones
Peptide, Amine, and Steroid
Peptide
short string of amino acids
Amine
modified amino acid (monoamine hormone)
Steroid
four rings of carbon atoms (derivatives of cholesterol)
Hormones have two Main Modes of Action:
- Protein and amine hormones bind to receptors on the cell surface, which causes release of a second messenger, which brings about changes in cellular function
- Steroid hormones pass through the cell membrane and bind to receptors inside the cell
Second Messengers:
- Cyclic adenosine monophosphate (cyclic AMP or cAMP)
- Cyclic guanosine monophosphate (cyclic GMP or cGMP)
- Inositol triphosphate
Steroid Receptor Cofactors
may be necessary for the cell to respond to the steroid-receptor complexes
Receptor Isoforms
some steroids act on more than one receptor
Nongenomic Effect
a rapid, brief effect involving neuronal membrane receptors
Neurosteroids
steroids made in the brain, including testosterone and estrogens
Aromatase
an enzyme, that can convert testosterone
into estrogens
Negative Feedback
output feeds back and inhibits further secretion
Autocrine Feedback Loop
endocrine cells release a hormone whose presence feeds back on the endocrine cells to inhibit further secretion.
Target Cell Feedback
hormone acts on its target cells; the biological effect is detected by the endocrine gland and further release is inhibited
Tropic Hormones
the anterior pituitary gland releases this and affects other endocrine glands
Releasing Hormones
used by the hypothalamus to regulate the pituitary’s release of tropic hormones