Endocrine System Flashcards
Role of Endocrine system
Blood Glucose
Blood Osmorality
Menstrual Cycle
AND MORE!
Features of Endocrine System
- Ductless glands
- System is not connected physically
- Secretes hormones into bloodstream which act on target organs throughout body
Definition of Hormone
- Chemical substance secreted by endocrine glands directly into bloodstream
- Alters activity of one or more target cells
- Destroyed by liver after sometime
Features of Hormones
- Slow in action
- Needed in small amounts to bring about large changes at target cells
- Specific target site far away from gland
Features of Water Soluble Hormones
- Circulate in bloodstream as free hormones due to high solubility
- Large and polar -> Cannot pass cell membrane
- Binds to membrane bound receptors
Eg. ADH, Insulin, Glucagon
Features of Lipid Soluble Hormones
- Circulate bloodstream bound to binding proteins due to small size and low solubility
- Binds to nuclear receptor in target cell
Eg. Steroids
How do glands work?
- Release of hormones in short bursts, frequency according to stimulation of gland
- Regulated by nerve signals, chemical changes in blood and other hormones
In response to bodies internal environment (homeostatic)
Role of hypothalamus
- Processes nerve signals -> regulates the secretion of hormones from pituitary gland
Role of Pancreas
Contains pancreatic islets
- Alpha cells -> secretes glucagon -> increases blood glucose level (BGL)
- Beta cells -> secretes insulin -> decreases BGL
How does insulin and glucagon bind to target cells?
- They are peptide hormones and are too large and polar to pass through cell membrane
- Interacts with extracellular insulin/glucagon receptors
- Triggers actions within liver
Outline the homeostatic process when blood glucose concentration is too high
- High blood glucose above set norm detected by receptors in pancreas
- Stimulates secretion of insulin by beta cells in pancreas
- Insulin transported via bloodstream to target cells such as liver
- Decreases concentration through several processes
- Blood glucose concentration falls back to normal -> insulin secretion inhibited via negative feedback
Outline the homeostatic process when blood glucose concentration is low
- Low blood glucose concentration below set norm detected by receptors in pancreas
- Stimulates secretion of glucagon by alpha cells in pancreas
- Glucagon transported via bloodstream to target cells such as liver
- Increases concentration through several processes
- Blood glucose concentration increases back to set norm -> glucagon secretion inhibited via negative feedback
Actions at effectors when BGL is high
- Increased uptake of glucose into muscle cells by enhancing cell permability to glucose
- Increase conversion of glucose to glycogen
- Increase uptake of amino acids and increased protein syntheis
Actions at effectors when BGL is low
- Accelerate conversion of glycogen to glucose in liver and skeletal muscle cells
- Accelerate formation of glucose from lactic acid and amino acids
- Decrease conversion of glucose to glycogen
How is the endocrine system disrupted?
Level of hormone secretion too high/too low
OR
Level of responsiveness to hormone by target cell too high/toolow
