Hormonal Communication Flashcards
Specification reference: 5.1.4
Endocrine System
A system used to send information about the changes in environment around the body to give a designated response.
Endocrine Glands
Group of cells which are specialized to secrete chemicals (hormones) into the bloodstream.
Name examples of endocrine glands?
Adrenal glands and the Pancreas
Pituitary Glands (both sexes)
- Produces the growth hormone which controls the growth of bones and muscles.
- An anti-diuretic hormone which increases reabsorption of water in the kidneys
- Gonadotrophins which control the development of ovaries and testes.
Thyroid Gland (both sexes)
Produces thyroxine which controls the rate of metabolism and that glucose is used up in respiration and promotes growth
Adrenal Gland (both sexes)
Produces Adrenaline which increases heart and breathing rate + raises blood sugar levels.
Pineal Gland (both sexes)
Produces melatonin which affects reproductive development and daily cycles.
Thymus(both sexes)
Produces thymosin which promotes production and maturation of white blood cells.
Pancreas (both sexes)
- Produces insulin which converts excess glucose into glycogen in the liver
- And glucagon which converts glycogen back to glucose in the liver.
Testis
Produces testosterone which controls sperm production and secondary sexual characteristics
Overies
- Produces osetrogen which controls ovulation and sexual characteristics and progesterone, osetrogen which controls ovulation and secondary characteristics.
- Progesterone prepares the uterus lining for recieving an embryo
Why are hormones referred to as chemical messengers?
They carry information from one part of the body to another
Hormones can be …
Steroids, proteins glycoproteins, polypeptides, amines or tyrosine derivatives (Chemically different but share the same characteristic)
Hormones
Are secreted into the blood when a gland is stimulated which causes a change in the concentration of a particular substance (blood glucose concentration). It can also occur due to nerve impulses and another hormone.
Name two types of hormones?
Sterioid and Non steroid
Steroid hormones
- Are lipid soluble
- Can pass through the lipid component of a cell membrane and binds to the steroid hormoine receptors to form a hormone- receptor complex.
- Receptors may be present in the cytoplasm or the nucleus (depending on the hormone)
- The hormone- receptor complex acts as a transcription factor which inihibits the transcription of a specific gene (eg osetrogen)
What happens to hormones when they are secreted?
- They are transported into blood plasma all over the body.
- The hormones diffuse out and bind to specific receptors for that hormone found on the membrane or cytoplasm os that cell in target organs (target cells)
- Once bound on the receptors the hormones stimulate the target cells and produce a response.
Steroid hormones
- Are lipid soluble
- Can pass through the lipid component of a cell membrane and binds to the steroid hormone receptors to form a hormone- receptor complex.
- Receptors may be present in the cytoplasm or the nucleus (depending on the hormone)
- The hormone-receptor complex acts as a transcription factor which inhibits the transcription of a specific gene (eg oestrogen)
Non-steroid hormones
- Are hydrophilic so cant pass directly through the cell membrane
- They bind to specific receptors on the cell surface membrane of a target cell.
- This triggers a cascade reaction mediated by chemicals called second messengers (eg adrenaline)
Hormonal system differences
- Communication by chemical messengers - hormones
- Transmission in the bloodstream
- Transmission is slow
- Hormones travel to all parts but only target cells respond
- Response is widespread
- Response is slow
- The response is long lasting
- The effect may be permanent + irreversible
Nervous system differences
- Communication is by nerve impulses
- Transmission is by neurons
- Transmission is very rapid
- nerve impulses travel to specific parts of the body
- Response is localised
- Response is rapid
- Response is short lived
- The effect is temporary and reversible
Adrenal Glands
Located at top of each kidney made up of an: adrenal cortex and an adrenal medulla