(5.4) Hormonal Communication Flashcards
What are exocrine glands?
Secrete substances into a duct
What are endocrine glands?
Ductless glands from which hormones are released directly into the blood
What are hormones?
Proteins or steroids that are released by the endocrine glands directly into the blood. They act as messengers carrying a signal from the doctrine glands to a specific target organ or tissue
Describe the structure of protein and peptide hormones
- derivative of amino acids
- not soluble in the phospholipid bilayer - don’t enter the cell
Describe how non-steroid hormones effect a cell
- non-steroid hormones are first messengers
- signal molecules outside of the cell to initiate an effect on the inside of the cell
- cause effect of second messenger - stimulates a change in cell activity
- acts via G protein in the membrane which is activated when a hormone binds to the receptor
- this activates an effector molecule (usually adenylyl cyclase)
- Adenylyl cyclase converts ATP to cyclic AMP
- May act directly to directly or initiate a cascade of enzyme controlled reactions
How does a steroid hormone act on a cell?
- steroid hormone act on a cell membrane of a target cell
- hormone binds with a specific receptor
- this creates a steroid hormone complex which enters the nucleus of the cell and binds to another receptor on the chromosomal material
- binding stimulates the production of mRNA
What does the adrenal cortex release?
Adrenaline (protein hormone)
What are the effects of adrenaline?
- relax smooth muscles
- increase stroke volume of heart
- increase heart rate
- vasoconstriction - raises blood pressure
- stimulate conversion of glycogen to glucose
- dilating pupils
- increasing mental awareness
- inhibiting gut action
- cause body hair to stand erect
What is the zona glomerulosa?
Outermost layer of the adrenal cortex which secretes mineralocorticoids
What is the job of mineralocorticoids?
- helps to control the concentrations of sodium and potassium in the blood
- acts on cells of distal tubules and collecting ducts in the kidney
What is the zona fasciculata?
The middle layer of the adrenal cortex which secretes glucocorticoids
What is the job of glucocorticoids?
- control metabolism of carbohydrates, fats and proteins in the liver
- released in a response to stress and low blood concentration
What is the zona reticularis?
Innermost layer of the adrenal cortex which precursor molecules to make sex hormones (cortisol)
If the correct enzymes are not present then precursor androgens are released
What is the role of precursor androgens?
Regulate production of gametes and secondary sexual characteristics
What is the exocrine function of the pancreas?
- secrete substances into a gland
- cells in a small group surrounding tubule
- acini grouped together in lobes separated by connective tissues
- cells secrete enzymes that synthesis into the tubules
- tubules join to form intralobular ducts that combine to make the pancreatic duct
