The Endocrine Sytem Flashcards
What actually is the endocrine system?
Endocrine glands situated throughout the body that secrete hormones.
What is an endocrine gland?
A group of cells specialised to secrete hormones directly into the bloodstream.
How close are the pituitary gland and hypothamalus and why is this benefical?
Very close - both in the brain
Nervous and hormonal responses of the body are closely linked and coordinated.,
Pituitary gland:
Where is it?
What is its function?
1) Located at the base of the brain
2) - Secrete growth hormone for growth of muscles and bones
- Secrete ADH (antidiuretic hormone) for water reabsorption in
kidneys
- Secrete gonadorphins for development of ovaries and testes
Thyroid gland:
Where is it?
What is its function?
1) Beneath the neck, in front of the trachea (windpipe)
2) - Secrete thyroxine which controls the body’s rate of metabolism and the rate that glucose is taken up in respiration, and promotes growth.
Adrenal gland:
Where is it?
What is its function?
1) Located on top of each kidney (so 2 overall(
2) - Secrete adrenaline which increases heart rate and breathing rate and raises blood glucose/sugar level.
Testis gland:
Where is it?
What is its function?
1) Located within the scrotum
2) Produces testosterone which is responsible for sperm production and secondary sexual characteristics.
Pineal gland:
Where is it?
What is its function?
1) Located within the brain
2) Produces melatonin that affects reproductive development and daily cycles - e.g. sleep cycles.
Thymus gland:
Where is it?
What is its function?
1) Located in upper chest, behind the sternum
2) - Produces thymosine which takes part in the production and maturation of white blood cells.
Pancreas (atic) gland:
Where is it?
What is its function?
1) (Upper part of) Abdomen
2) - Produces Insulin
- Produces glucagon
Ovary gland:
Where is it?
What is its function?
1) Lower abdomen, behind pelvis
2) - Produces oestrogen which controls ovulation and secondary
characteristics.
- Produces progesterone which prepares the uterus lining for
recieving an embryo.
Differnece between endocrine glands vs exocrine glands:
Endocrine glands secrete hormones DIRECTLY INTO THE BLOODSTREAM.
Exocrine glands secrete hormones THROUGH DUCTS, to the surface of the body or organs.
Target cells (in the context of hormones)?
Target organs which have cells that have specific receptors (to the hormones) found on their membranes/cytoplasm.
So when the hormones in the bloodstream diffuse out of there - they can bind to receptors on these target cells.
State the 2 different types of hormones:
What actually makes these different?
Steroid hormones, Non - steroid hormones
What makes one different from the other is the way in which it causes an effect on the target cell.
Steroid hormones:
Example?
Lipid-soluble, pass through the lipid component of the cell membrane and bind to steroid hormone receptors to form a hormone-receptor complex. These receptors may be in either the cytoplasm or nucleus.
The hormone-receptor complex acts as a transcription factor as it in turn, facilitates or inhibits the transcription of a specific gene. An example is oestrogen.
Non-steroid hormones:
Example?
Hydrophillic so cannot pass throuh cell membrane.
Instead binds to specific non-steroid hormone receptors on the cell membrane of the target cell.
Triggers a cascade reaction, mediated by chemicals called second messengers. An example is adrenlaine.
Differences between hormonal and neuronal communcation system?
Hormonal system communicates via hormones, whereas with neuronal communcation it is via nerve impulses
Hormonal system communicates using the bloodstream whereas with neuronal communication it is with neurones.
Hormonal communication is less specific ( so like stimualting a particular gland can secrete several hormones/chemicals, but with a nervous impulse its a specific action) and slower than neuronal communication, which on the other hand is a more longer-lasting and widespread effect.
Why is hormonal communication regarded as a less specific form AND SLOWER form of communication than neuronal communication?
Since the hormones are not directly released on target cells - instead into the blood stream.
Thus, this leads to a slower form of communication. Also since hormones are not broken down as quickly as neurotransmitters, it can lead to a longer-lasting and more widespread effect.
Adrenal gland structure:
On the outside of the adrenal gland is the adrenal cortex. This produces essential hormones for life such as cortisol and aldosterone
On the inside of the adrenal gland is the adrenal medulla which produces non-essential hormones for life such as adrenaline which is in reponse to stress.
Adrenal Cortex:
What hormones do they produce?
(3 types)
1) Glucocorticoids - includes cortisol which helps to regulate metabolism by controlling how the body converts fats/proteins and carbohydrates into energy
Cortisol also helps to regulate blood pressure and caridiovascular function in response to stress.
Corticosterone is another glucocorticoid homrone released - this works with cortisol to regulate immune response and supress inflamatory reactions.
Both cortisol and corticosterone hormones release are controlled by the hypothamalus
2) Mineralocorticoids - Aldosterone helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and body fluids. Its release is mediated by signals detected in the kidney.
3) Androgens - small amounts of male and female sex hormones are released - important in women particualrly after the menopause
Adrenal Medulla:
What hormones do they produce?
(2 types)
Hormones of the adrenal medulla are released when the sympathetic nervous system is stimualted (increasing responses)
1) Adrenaline - increases heart rate sending blood quickly to brain and muscles. Converts glycogen to glucose in liver raising blood sugar concentrations
2) Noradrenaline - works along with adrenaline in responses to stress. Widening of pupils, Vasoconstriction (narrowing of blood vessels) in order to increase blood pressure, Widening of air passages in the lungs.
