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Describe the difference between the endocrine system and the nervous system
- Nervous=electrical impulses
- Endocrine=hormones (chemical messengers)
- Both sense a problem and act upon it and are responsible for integration and control of bodily functions
What 5 things does the endocrine system control?
- Body defences
- Regulation of metabolism
- Growth and development
How do hormones reach their target cells?
Gland secretes blood bourne hormone (no ducts so can't go straight from gland to cell) which travels to target cell. Hornones only go to their target cells which is why the system is so slow.
What are the 2 types of hormone?
- (1) Steroid based = work quite quick
- (2) Amino acid (protein) based = work on 2nd messengers
Where is the pancreas?
Behind the stomach
What are the Islets of Langerhans and where are they located?
- Scattered within the pancreas
- Responsible for the production of two hormones:
- (1) Glucagon (alpha cell) - hypergylcemic hormone
- Gets blood sugar levels back UP to normal by breaking down sugar and putting back into blood
(2)Insulin (beta cell) - hypoglycemic hormone
Gets blood sugar levels back DOWN to normal by breaking down sugar and storing in muscle and liver
Where is the pituitary gland and what does it do?
- In the brain.
- Maintains water levels
- Produces at least 9 difference hormones
- ADH major hormone released with respect to exercise - causes kidneys to return more water to the blood
With respect to the pituitary gland, what is the major hormone released during exercise?
ADH - causes kidneys to return more water to the blood
Where are the Adrenal Glands and what are the two parts it is split into?
- Directly above each kidney.
- Split into Adrenal Medulla - releases epinephrine and norepinephrine (fight or flight)
- And Adrenal Cortex - releases hormones essential for life
Target cells - what does the strength of the effect depend on? (3 things)
- (1) Concentration of hormone in the blood
- (2) No. of target cells on the cell
- (3) Affinity of the target cell - liking the hormone to a greater extent
Are hormone secreted at a constant rate?
How do target cells regulate the no. of receptors for any given hormone?
- Down regulation = too much hormone, shuts receptors
- Up regulation = not enough hormone, opens up more receptors
Describe the negative feedback loop with regard to hormone control.
- Feedback loop controls synthesis and release of hormones
- Preset level - if drops below will kick in, if too high will shut down
- Hormones kept within narrow "desirable" range
What are the 3 major stimuli that stimulate the endocrine glands?
- Humoral stimuli = ion levels in the blood
- Hormonal stimuli = hormones don't always work independantly - can cause each other to start working
- Neural stimuli = fight or flight - parasympathetic/sympathetic
Concentration of any given hormone in the blood is a result of:
(1) rate of release of the hormone (2) speed of inactivation and removal of that hormone from the body
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