Hormones Flashcards
What is a hormone?
A chemical messenger released directly into the blood and are carried in the blood to other parts of the body.
They are relased from a range of endocrine glands.
Thyroid gland
This produces thyroxine, which is involved in regulating things like the rate of metabolism, heart rate and temperature
This gland is in our neck
It is regulated by a negative feedback loop
The pituitary gland
Produces many hormones that regulate body conditions. It is also called the master gland because these hormones act on other glands, dirceting them to release hormones to bring out change.
It is found in the brain and is linked to the hypothalamus
The pancreas
Produces insulin which is used to regulate the blood glucose level
Adrenal gland
Produce adrenaline which is used to prepare the body for a ‘fight or flight’ responce when an organism is presented with a dangerous situation Used in times of fear and stress
The two adrenal glands are situated above each kidney
Adrenaline enlarges the air passages of the lungs and alters metabloism to boost faster delivery of oxygen and glucose to the brain and muscles
Testes
Male only
They produce testosterone which controls puberty and sperm production in males
Ovaries
Female only
Produce oestrogen which is involved in the menstural cycle and controls pubery
Difference between hormones and neurones
Neurones have a very fast action whereas hormones have a slower action
Neurones act for a very short time whereas hormones act for a long time
Neurones act on a very precise area whereas hormones act in a more general way
What does adrenaline do?
Prepares the body for ‘fight or flight’ by activating processes that increase the supply of oxygen and glucose to cells
How does heart rate and blood pressure increase?
Adrenaline binds to specific receptors in the heart causing the heart muscle to contract more frequently and with more force do the heart rate and blood pressure increase
This increases blood flow to the muscles so the cells recive more oxygen and glucose for increased respiration
How increase to blood glucose level?
Adrenaline also binds to receptors in the liver causing the liver to brack down its gluogen stores to release glucose
This increases blood glucose level, so there’s more glucose in the blood to be transported to the cells
Negative feedback
A control mechanism reacting to change in a condition by trying to bring levels back to normal
What happens when blood thyroxine level is lower than usual?
The hypothalamus is stimulated to release thyrotropin releasing hormone (TRH).
TRH stimulates the pituitary gland to release thyroid stimulating hormone. (TSH)
TSH stimulates the thyroid gland to relase thyroxine so the blood thyroxine level rises back towards normal.
What happens when blood thyroxine level is higher than usual?
The release of TRH from the hypothalamus is inhibited, which reduces the production of TSH, so the blood thyroxine level falls.
What is the menstural cycle?
The monthly sequence of events in which the female body releases an egg and prepaers the uterus in case the egg is fertilised
