coordination and control - the human endocrine system Flashcards
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adrenal glands
definition
Glands located on top of the kidneys which produce adrenaline.
adrenaline
definition
Hormone produced by the adrenal gland and is released in times of fear or stress.
carbohydrate
definition
Food belonging to the food group consisting of sugars, starch and cellulose. Carbohydrates are vital for energy in humans and are stored as fat if eaten in excess. In plants, carbohydrates are important for photosynthesis.
gland
definition
An organ or tissue that makes a substance for release, such as a hormone.
glycogen
definition
Animals store glucose as glycogen in their liver and muscle tissues.
homeostasis
definition
The maintenance of steady conditions. The ability of the body to maintain a constant internal environment, eg temperature and blood glucose concentration.
hormone
definition
Chemical messenger produced in glands and carried by the blood to specific organs in the body.
hypothalamus
definition
Part of the brain which controls water balance, temperature and secretion of hormones by the pituitary gland.
negative feedback
definition
A mechanism where changes to conditions cause an action to reverse the change, to keep conditions stable.
negative feedback mechanism
definition
Mechanism to lower raised levels of something, and to raise reduced levels of something.
pancreas
definition
Large gland located in the abdomen near the stomach which produces digestive enzymes and the hormone insulin.
pituitary gland
definition
An endocrine gland that is located just below the centre of the brain. It releases a number of important hormones.
respiration
definition
The chemical change that takes place inside living cells, which uses glucose and oxygen to release the energy that organisms need to live. Carbon dioxide is a by-product of respiration.
target organ
definition
The organ with receptor molecules on its cell surfaces which recognise a specific hormone.
thyroid
definition
Gland located at the base of the neck which controls metabolic rate by releasing the hormone thyroxine.
thyroxine
definition
Hormone produced by the thyroid to control metabolism.
TRH
definition
Thyrotropin releasing hormone produced by the hypothalmus in response to a lack of thyroxine in the blood.
TSH
definition
Thyroid stimulating hormone produced by the pituitary gland in response to TRH.
Hormones and nerves
A hormone is a chemical substance, produced by a gland and carried in the bloodstream, which alters the activity of specific target organs. An example of this is the release of the hormone adrenaline, which is released by the adrenal glands. One of its target organs is the heart, where it increases the heart rate.
Like the nervous system, hormones can control the body. The effects are much slower than the nervous system, but they last for longer.
What happens to a hormone once it has been used?
Once a hormone has been used, it is destroyed by the liver.
There are important differences between nervous and hormonal control.
What is the type of signal for nervous and hormonal control?
Nervous: Electrical (chemical at synapses)
Hormonal: Chemical
There are important differences between nervous and hormonal control.
What is the transmission of signal for nervous and hormonal control?
Nervous: By nerve cells (neurones)
Hormonal: By the bloodstream
There are important differences between nervous and hormonal control.
What are the effectors for nervous and hormonal control?
Nervous: Muscles or glands
Hormonal: Target cells in particular organs
There are important differences between nervous and hormonal control.
What is the type of response for nervous and hormonal control?
Nervous: Muscle contraction or secretion
Hormonal: Chemical change
There are important differences between nervous and hormonal control.
What is the speed of response for nervous and hormonal control?
Nervous: Very rapid
Hormonal: Slower
There are important differences between nervous and hormonal control.
What is the duration of response for nervous and hormonal control?
Nervous: Short (until nerve impulses stop)
Hormonal: Long (until hormone is broken down)
Different hormones
The glands in the body produce a range of different chemical hormones that travel in the bloodstream and affect a number of different organs in the body. The diagram below shows this in detail.
Examples of important hormones released into the bloodstream.
Important hormones released into the bloodstream include ADH (anti-diuretic hormone), adrenaline and insulin.
What hormone does the thyroid gland produce?
thyroxine
What hormone does the pancreas produce?
insulin
What hormone do the testes produce?
testosterone
What hormone do the ovaries produce?
oestrogen
What hormone do the adrenal glands produce?
adrenaline
Pituitary gland
The ‘master gland’ situated at the base of the brain
What hormone does the pituitary gland produce?
ADH
What is the source of the hormone ADH?
Pituitary gland
What is the source of the hormone adrenaline?
Adrenal glands
What is the source of the hormone insulin?
Pancreas
What is the target organ(s) of AHD?
Kidneys