B3.2 The Endocrine System Flashcards
What are hormones?
Hormones are chemical messengers which travel in the blood and control body processes that need constant adjustment
What is homeostasis?
The maintenance of a constant internal environment
What are endocrine glands?
Glands that produce and secrete a hormone
What is the endocrine system
All endocrine glands and the hormones they produce
What are target organs?
Organs a hormone has an effect on
Differences between nervous impulses and hormones
Nerves travel to specific parts of the body, however hormones travel all around the body but only target organs respond. Nerves communicate very fast but hormones are slower. Nerves are short acting but hormones are long actingm
How do hormones work on target cells
Hormones diffuse out of blood to bind specific receptors on target cells. The receptors then stimulate the hormonal response.
Thyroid gland hormones
Thyroid gland secretes thyroid hormones which control the body’s metabolic rate
What is thyroxine
Thyroxine is a hormone produced in the thyroid gland, and it plays a vital role in regulating the body’s basal metabolic rate/
Function of thyroid gland
To take iodine and convert it into thyroxine by combining it with the amino acid tyrosine
What is negative feedback
Negative feedback is a system that detects a change in a condition. The system then acts to return conditions back to the desired level
Adrenal glands located
Adrenal glands are located on top of both kidneys
Adrenal gland hormones
At times of stress they secrete the hormone adrenaline, which prepares the body for intensive action, also known as ‘fight or flight’ response
Effects of adrenaline
Adrenaline increases rate of ATP production, increases rate of breathing, increases heart rate, and diverts blood to muscles.
What is the menstrual cycle
the menstrual cycle is the reproductive cycle of female humans which is controlled by reproductive hormones. It prepares the woman’s body for pregnancy.
Main stages of menstrual cycle
Menstruation - Day 1 to 5/7
Lining of uterus builds up - Day 5/7 to 14
Egg released - Day 14
Lining maintained - Day 14 to 28
After day 28, breaks down again
What reproductive hormones does the pituitary gland secrete, and what are their function?
Pituitary gland secretes luteinising hormone + follicle stimulating hormone. They stimulate the ovaries to produce oestrigen + progesterone.
FSH - causes one fillicle to mature in the ovaries
LH - stimulates ovulation
What reproductive hormones does the ovaries secrete, and what are their function?
Oestrogen and progesterone.
Oestrogen - stimulates the lining of the womb to build up for pregnancy.
progesterone - maintains the uterus lining for levels to stay hugh during pregnancy.
Hormone interactions order
- FSH stimulates the ovaries to produce oestrogen
- As oestrogen levels rise they inhibit FSH to prevent more than one egg maturing
- Oestrogen stimulates pituitary gland to release LH
- Progesterone inhibits LH
What are contraceptives and what are the types?
Techniques used to control fertility.
Non hormonal - barrier methods that prevent sperm from contacting the egg or pysical devices that release chemical compounds.
Hormonal - these use hormones to distrupt the normal female reproductive cycle
Describe what IUD, IUS, combined pill, and progesterone pill do.
IUD - inserted into the uterus. releases copper which prevents sperm surviving in the uterus and fallopian tubes. Can also prevent implantation of a fertalised ovum.
Combined pill - Prevents ovulation, thickens mucus from the cervix to stop sperm reaching an ovum, prevents implantation of a fertalised egg.
Progesterone pill - thickens mucus from the cervix to stop sperm reaching an ovum, thins lining of the uterus preventing implantation.
IUS - (hormonal) inserted into the uterus, has the same effect as progesterone pill.
Describe some causes of infertility
- blocked sperm ducts
- not enough sperm being produced in the testes
- a lack of mature eggs produced in the ovaries
- a failure of the ovaries to release an egg
describe how FSH and LH can be used as artificial fertility drugs
FSH stimulates eggs in the ovaries to mature
LH triggers ovulation.
Outline how IVF works (invitro fertalisation)
IVF involves doctors collecting eggs from the ovary of the mother and fertalising them with the sperm of the father outisde the body in the lab. FSH and LH are given to the mother to ensure that as many eggs as possible mature in her ovaries.
Disadvantages of IVF
Unsuccessful attempts to have a baby can be highly physically and emotionally stressful to the parents.
Increases the likelihood of multiple births.
Very expensive but does not guarantee pregnancy.
Relatively low success rates.
What is the function of plant hormones?
Plant hormones enable a plant to coordinate and control changes in growth and development in response to changes in the enviroment.
What is a tropism?
A tropism is a growth movement in response to a particular type of stimulus
What is phototropism and gravitropism?
Phototropism is a growth response to the stimulus of light.
Gravitropism is a growth response to the stimulus of gravity.
What is auxin?
Auxin is a plant hormone that enables a plant to grow towards or away from a stimulus. It stimulates shoot growth but inhibits root growth.
Explain how plants respond to light
When light hits one side of a shoot tip, the auxin moves to the other side of the shoot, causing the concentration of auxin to build up on the unlit side. The cells then respond by elongating, increasing the length of this side of the shoot, so the shoot bends towards the light.
Explain how plants respond to gravity
Auxin is gathered on the lower side of both the roots and shoots. The root grows more on the side with the least auxin, making it bend and grow down towards gravity. The shoot grows more on the side with the most auxin, making it bend and grow up away from gravity.
Main function of Auxins
Stimulate growth by causing cell elongation. Can also help to regulate fruit development.
Main function of Ethene
Causes plant fruits to ripen by stimulating the conversion of starch into sugar.
Main function of Gibberellins
promote growth, particularly stem elongation. Can also end the dormancy period of seeds and buds which leads to shoots and flowers opening.
