B3.2 The Endocrine System Flashcards
What are hormones?
Hormones are chemical messengers
Where are hormones produced?
They are produced in endocrine glands and are secreted into the blood.
Where in the blood do hormones travel in?
The blood transports the hormones in the plasma around the body
What do hormones control?
Hormones control body processes that need constant adjustment - such as body temperature
Define homeostasis
Maintaining a controlled internal environment
Name all the glands and the hormones they produce
thyroid gland produces thyroxine adrenal glands produces adrenaline Pancreas produce insulin and glucogen Reproductive glands: - ovaries produce oestrogen and progesterone - testes produce testosterone
What do the hypothalamus and pituitary gland produce?
These produce hormones that regulate production of other hormones
How do hormones travel to target organs?
Hormones diffuse out of the blood and bind to specific receptors for that hormone, found on membranes or in the cytoplasm of cells in the target organs, known as target cells. Once bound to their receptors the hormones stimulate the target cells to produce a response
Compares the nervous system to the endocrine system
The speed of communication for nerves is very fast whereas for hormones it is slower.
In the nervous system an electrical impulse travels along the axon of a neurone. In the endocrine system the hormones are transported in the blood.
The duration is response is short for nerves whereas for hormones it is long acting.
Nerves target a very precise area whereas hormones target a larger area
Where are the adrenal glands located?
The adrenal glands are located just above the kidneys
What does adrenaline do?
Adrenaline prepares the body for intensive action. It is called the ‘fight or flight’ response. They are secreted in times of stress.
It activates processes that increase the supply of oxygen and glucose to cells.
How do adrenaline prepare the body for ‘fight or flight’?
Adrenaline binds to specific receptors in the heart. This causes the heart muscle to contract more frequently and with more force, so heart rate and blood pressure is increased.
This increases blood flow to the muscles, so the cells receive more oxygen and glucose for increased respiration.
Adrenaline also binds to receptors in the liver. This causes the liver to break down its glycogen stores to release glucose.
This increases the blood glucose level, so there’s more glucose in the blood to be transported to the cells.
Where is the thyroid gland located?
In the neck
What is thyroxine for?
Thyroxine plays an important role in regulating metabolic rate
It controls how much energy is available to the cells.
How are thyroxine levels controlled?
When the body requires more energy, the hypothalamus causes the pituitary gland to releases thyroid-stimulating hormone (TSH). TSH stimulates the thyroid gland to release thyroxine. This increase the metabolic rate, allowing cells to transfer additional energy.
When cells have the required amount of energy, the hypothalamus inhibits TSH. The thyroid gland therefore stops releasing thyroxine.
Testosterone
Main sex hormone
Produced in the testes
Stimulates sperm production and is important for the development of the male reproductive system.
What is the menstrual cycle?
The menstrual cycle is a monthly cycle during which a woman’s body gets ready for pregnancy.
How long does the menstrual cycle last?
28 days
What happens in each stage of the menstruation cycle?
Day 1- The uterus lining breaks down and is released
From day 4 to day 14 the lining of uterus starts to thicken, to get ready to receive a fertilising egg.
About day 14 an egg develops and is released from an ovary. This is called ovulation.
The lining is then maintained for about 14 days, until day 28. If no fertilised egg has implanted into the uterus wall by day 28, the uterus lining starts to break down and then the whole cycle starts again.
How effective is the oestrogen and progesterone pill?
Over 99%
Ovary
Eggs mature here
Negative tropism
If a part of the plant grows away from the stimulus
cervix
entrance to uterus
vagina
Receives sperm from the penis during sexual intercourse
How effective is intrauterine device?
Over 99%
Oestrogen
made and secreted by the ovaries
Causes the lining of the uterus to thicken and grow
Stimulates the production of LH
Inhibits the production of FSH so that only one egg is released in each cycle
Peaks between day 4 and day 14
Explain the commercial use of plant hormones:
Producing seedless fruits
Fruits normally grow on plants which have been pollinated by insects. If the plant doesn’t get pollinated, the fruit and seeds don’t grow.
If auxins and gibberellins are applied to the unpollinated flowers of some types of plant, the fruit will grow but the seeds won’t.
This produces parthenocarpio fruit- fruit without any seeds
How effective is condom (female)?
95%