Hormones: are molecules that are released by endocrine glands directly into the blood. They act as messengers, carrying a signal from the endocrine gland to a specific target organ or tissue.
- Blood circulation is used to transport hormones
- Transported throughout the body
- Endocrine glands are ductless and release hormones straight into the capillaries running through them
ENDOCRINE gland: is a gland that secretes hormones directly into the blood. They have no ducts.
EXOCRINE gland: is a gland that secretes molecule into a duct that carries the molecules to where they are used e.g. salivary glands.
Adrenaline
- Adrenaline is an amino acid derivative, they cannot enter the target cell. Adrenaline receptor on outside of the plasma membrane ha a shape complimentary to the shape of the adrenaline molecule
Adenyl cyclase
- Adenyl cyclase is an enzyme associated with receptor for many hormones, including adrenaline. It is found on the inside of the plasma membrane.
- Adrenaline receptor is associated with this enzyme.
Action of adrenaline
- Adrenaline in blood binds to a specific receptor
- Adrenaline is first messenger
- Activate adenylcyclase enzyme which converts ATP to cyclic AMP
- cAMP is second messenger inside the cell
- cAMP causes effect inside cell by activating enzymes
Adrenal medulla
- Cells make and release adrenaline hormone in response to stress
- Most cells have adrenaline receptors
- Effect is to prepare for activity
Effects of adrenaline
- Relax smooth muscles in bronchioles
- Increase stroke volume of heart and increase heart rate
- Causes vasoconstriction to raise blood pressure
- Stimulate glycogen to convert to glucose
- Dilate pupils
- Increase mental awareness
- Inhibit action of gut and cause body hair to react
Target cells must have specific receptors as hormones binds to receptor and activates a process inside the cell receptors must be specific so the hormone only bind to the correct cells, receptors and hormones have shapes complementary to each other.
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