Section 39.1 (Exam 3/4) Hormones Flashcards
Hormones Circulate Around the Body and Affect Target Cells
What are endocrines?
chemical signals secreted by epithelial cells directly into the ECF
Where do endocrines go after they are secreted into the ECF?
Some diffuse locally and some go into the bloodstream where they circulate across the whole body
What are the 3 types of endocrines?
Hormones, Paracrines, and Autocrines
Do all endocrine cells exist as glands?
No, some exist as single cells
What are the two types of glands in the endocrine system?
Endocrine and exocrine glands
What are endocrine glands?
aggregations of endocrine cells that secrete hormones within the body
What are exocrine glands?
secrete substances through ducts to the outside of the body
What are neurohormones?
A type of hormone that are secreted by neurons and enter the bloodstream circulation
What are pheremones?
chemical signals released from the body of an animal to influence the behavior of other animals
What are the three classes of hormones?
Peptide/protein hormones, steroid hormones, and amine hormones
What are some characteristics of peptide/protein hormones (e.g. insulin)?
Water-soluble, easily transported in blood
Cannot cross the lipid bilayer of the cell membrane, is released from the secretory cell through vesicles (exocytosis)
What are some characteristics of steroid hormones (e.g. testosterone)?
Synthesized from cholesterol
Lipid-soluble; can pass through cell membranes
Travels through blood by binding to carrier molecules (not water-soluble, blood is mostly water)
What are some characteristics of amine hormones (e.g. epinephrine)?
Mostly synthesized from the amino acid tyrosine
Either water-soluble or lipid-soluble
Since they can’t pass through cell membranes, how do water-soluble hormones bind to the target cell?
To a large transmembrane glycoprotein receptor on the target cell with three domains
What are the 3 domains of a large transmembrane glycoprotein receptor on a target cell?
- binding domain (extracellular)
- transmembrane domain (within cell membrane)
- cytoplasmic domain that extends into the cytoplasm (intracellular)
From the point where a hormone binds to the binding domain on the receptor of a target cell, how does the hormone alter gene expression?
The signal travels from the binding domain to the transmembrane domain to the cytoplasmic domain.
The cytoplasmic domain alerts second messengers which can activate protein kinases or protein phosphatases.
Protein kinases phosphorylate or add a phosphate group to a protein and protein phosphatases dephosphorylate or remove a phosphate group from a protein.
The phosphate groups on these proteins ultimately alter gene expression.
How do lipid-soluble hormones alter gene expression?
They diffuse directly through the cell membrane and bind to receptors within the cell.
They can enter the nucleus as well, which allows them to alter gene expression directly
One hormone can trigger different responses in different types of cells. What response is a good example of this phenomena?
The fight-or-flight response
Which two amine hormones are released during the fight-or-flight response?
epinephrine and norepinephrine
What are the 4 places epinephrine and norepinephrine bind to during the fight-o-flight response, and what responses do they cause to each of the 4?
The heart – increasing the heart rate
Blood vessels (on organs not needed for survival) – constricting them and sending blood to heart and then muscles
Liver – break down glycogen and release glucose into the blood as a quick energy supply
Fat cells – stimulates breakdown of fats to fatty acids—another source of energy
Individual signaling molecules are highly evolutionarily conserved. What are their functions across different species?
the function of the same signaling molecule can vary across different species
What is the function of prolactin in fish, humans, birds, and amphibians?
In fishes – involved in osmoregulation
In humans – mammary gland development and milk production
In birds – nesting activity and incubation
In amphibians – “water drive” that returns terrestrial adults to water to breed
