Module 5: Hormonal Communication Flashcards
Endocrine glands
Produce and secrete hormones directly into the blood.
They have no ducts.
Exocrine glands
Do not produce hormones- they secrete molecules into a duct which carries them to where they are needed.
Adrenal medulla
Centre of adrenal gland.
Makes and secretes adrenaline and noradrenaline.
Adrenaline causes
- Relaxes smooth muscle in bronchioles
- Increases stroke volume of heart
- Increase heart rate
- Vasoconstriction
- Glycogen–>Glucose
- Dilates pupils
- Increase mental awareness
- Body hair erection
Noradrenaline
Reverse of adrenaline
Function of adrenaline
Non-steroid hormone- these cant dissolve in the cell surface membrane of target cells and get inside and must bind to a receptor.
Non-steroid hormones are known as first messengers- they cause an effect on the cell when they bind to a receptor. The binding causes a G-protein to activate adenyl cyclase which converts ATP into cyclic AMP (cAMP) which is the second messenger because it transmits the signal inside the cell and initiates a change inside the cell.
Adrenal cortex
Adrenal cortex ‐ uses cholesterol to produce steroid hormones:
3 layers:
‐ Zona Glomerulosa (nearest outside)
secretes mineralocorticoids ‐ help to control sodium and potassium levels in blood and blood pressure
‐ Zona Fasciculata secretes glucocorticoids e.g. cortisol ‐ helps to control metabolism of carbs, fats and protein in liver
‐ Zona Reticularis (nearest medulla) secretes precursors to the sex hormones
Steroid hormones
Steroid hormones enter cells by dissolving in the cell surface membrane.
They then bind with a receptor in the cytoplasm, the receptor‐hormone complex enters the nucleus, binds to another receptor on the chromosome. This causes mRNA to be made which then produces proteins.
Using the example of the adrenal glands, describe how different types of hormones are released and take affect on their target cells. (8)
- endocrine glands release hormones
- hormones travel in blood
- to target cells
- adrenal medulla releases non‐steroid hormones/adrenaline
- (adrenaline) acts as first messenger
- G‐protein activates adenyl cyclase
- converts ATP into cyclic AMP (cAMP)
- cAMP is the second messenger ‐ causes effect in cell
- adrenal cortex releases steroid hormones
- dissolve in cell surface membrane (of target cells)
- bind with a receptor in the cytoplasm
- receptor‐hormone complex binds to receptor on the chromosome/DNA
- causes mRNA/proteins to be made
- AVP: correct reference to Zona Glomerulosa, Zona Fasciculata, Zona Reticularis
- AVP: ref to complementary shapes
How can hormones travel all around the body in the blood yet still have such specific effects on body tissue?
Endocrine glands make and secrete hormones and release them directly into the blood.
Hormones bind to specific complementary receptors on the cell surface membranes of their target cells.
The hormones will not affect cells without these receptors.
Target cells are grouped into target tissues.
Exocrine action of the pancreas
The majority of the cells produce digestive enzymes- ‘pancreatic juice’.
These cells form groups (called acini) secrete enzymes into tubules which lead to the pancreatic duct which takes them to the small intestine.
In the ‘juice’:
- Amylase
- Trypsinogen
- Lipase
- Sodium hydrogen carbonate (alkali)
Endocrine action of the pancreas
- The islets of Langerhans contain alpha and beta cells
- The cells detect changes in blood glucose levels (normal = 90mg per100cm3)
- Alpha cells ‐ produce and secrete glucagon (hormone)
- Beta cells ‐ produce and secrete insulin (hormone)
- They secrete the hormones directly into closely associated capillaries
Pancreas on a micrograph
- Most cells = exocrine
- Groups of cells surrounding smallest hollow tubes - acini
- Slightly larger circular hollow tubes- tubules leading to pancreatic duct
- Circular patches with different staining- islets of Langerhans
Blood glucose too high
1) Beta cells detect rise in blood glucose level.
2) Stimulates production of insulin by beta cells.
3) Glucagon production by alpha cells is inhibited.
4) Insulin secreted into blood.
5) Insulin binds to receptors of target cells (hepatocytes and muscle cells).
6) Causes:
- More glucose channels inserts into plasma membrane
- more glucose enters the cells
- glucose converted to glycogen
- glucose converted to fats
- increased rate of glucose used in respiration.
7) This results in less glucose in the blood This is an example of negative feedback.
Blood glucose too low
1) Alpha cells detect fall in blood glucose level.
2) Stimulates production of glucagon by alpha cells
3) Insulin production by beta cells inhibited.
4) Glucagon secreted into blood.
5) Glucagon binds to receptors on target cells (hepatocytes).
6) Causes:
- hydrolysis of glycogen to glucose (glycogenolysis)
- conversion of fats and amino acids to glucose (gluconeogenesis)
- use more fatty acids in respiration
7) The glucose is released into the blood = more glucose in the blood.
