B5- Homeostasis and response Flashcards Preview

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Flashcards in B5- Homeostasis and response Deck (82):

Define homeostasis.

The maintenance of a constant internal environment.


What is kept the same in the human body?

-Water levels.
-Glucose levels.


In short, explain the nervous system.

-Receptors detect a stimulus.
-An electrical nervous signal is sent via the sensory neuron to the CNS.
-The CNS co-ordinates a response.
-The response is sent as another electric signal via the motor neuron and is carried out by effectors.


What is a stimulus?

A change in external environment.


What is a reflex?

An automatic and instantaneous nervous response which does not require conscious thought. They help prevent injury.


What is a synapse?

A gap between neurons. Impulses are transmitted by chemicals diffusing across and setting of a new electrical signal in the next neuron.


What is the CNS?

Central nervous system- an unconscious part of the brain and spinal cord which coordinates a nervous response.


What is the part of the nervous system which contains only nerves?

The peripheral nervous system.


What is the peripheral nervous system (PNS)?

It contains nerves only.


Describe the reflex arc.

1. The receptor detects a stimulus, e.g. hot plate.
2. Impulses are sent along a sensory neuron.
3. The signal reaches a synapse between the PNS and CNS, between the sensory and relay neuron.
4. The signal triggers chemicals to diffuse to the relay neuron, where they set of a new electrical impulse.
5. The CNS coordinates a response.
6. When the impulse reaches the synapse between the relay and motor neuron, the same process occurs.
7. The signal travels along the motor neuron to the effector.
8. The effector responds to the signal.


How do nervous signals travel?

As electrical impulses.


What is an effector?

A muscle or gland which carries out a response.


What order do the neurons come in the reflex arc?

Sensory -> relay -> motor.


What is the hormone system called and what does it do?

The endocrine system - sends information around the body. It is slower than the nervous system.


How do hormones travel?

Through the bloodstream towards targeted organs.


What are hormones produced by?

Endocrine glands.


Do hormones have long or short lasting effects?

Long lasting.


What are the primary male and female hormones?

Testosterone in males. Oestrogen and progesterone in females. (Oestrogen and testosterone are produced by both sexes).


What is the role of oestrogen?

-Causes the uterus lining to grow.
-Stimulates the release of LH.
-Inhibits release of FSH.


Where is oestrogen produced?

In the ovaries.


Where is testosterone produced?

In the testes.


What is the role of testosterone?

Controls puberty and sperm production in males.


What are hormones? (3 points)

Chemical molecules which control things in organs and cells that need constant adjustment. They have long lasting effects and act in a general way.


Give 6 examples of endocrine glands. Where are they located?

-Pituitary gland, at the base of the brain.
-Thyroid, along the front of windpipe.
-Ovaries, in the lower abdomen.
-Adrenal glands, above each kidney.
-Testes, in the scrotum.
-Pancreas, behind the stomach.


What is the role of the pituitary gland?

Produces many hormones which regulate body conditions. Is sometimes called the "master gland" because these hormones act on other glands which produce other hormones.


What is the role of the ovaries?

Produce oestrogen, which is involved in the menstrual cycle.


What is the role of the testes?

Produce testosterone.


What is the role of the thyroid?

Produces thyroxine, which regulates things like rate of metabolism, heart rate and temperature.


What is the role of the adrenal glands?

Produce adrenaline in stressful or scary situations. Adrenaline triggers mechanisms which increase the supply of oxygen and glucose to cells in the brain and muscles, to prepare for a fight or flight response. E.g. adrenaline increases heart rate.


What is the role of the pancreas?

Produces insulin, which is used to regulate the level of glucose in the blood.


Describe nerves.

They are a very fast action which last a short time and on a very precise area.


What do red blood cells and plasma do?

Red blood cells supply oxygen to our organs and tissues.
Plasma transports everything in the bloodstream.


Which organ monitors and controls blood glucose levels?

The pancreas.


What happens when blood glucose levels are too high?

Insulin is secreted by the pancreas and is carried by the blood to the liver. Here, the insulin triggers the liver to turn excess glucose into glycogen, which is stored in the liver and muscle cells.


What happens when blood glucose levels are too low?

Glucagon is secreted by the pancreas and is carried by the blood to the liver. Glucagon triggers the liver to convert stored glycogen into glucose, which is released back into the blood.


Which hormone removes glucose from the blood?



Which hormone releases glucose back into the blood?



What does glucose become when it is stored?



What are the food groups?

Carbohydrates, lipids and proteins.


What are proteins made of?

Amino acids.


What are lipids made of?

Triglycerides: glycerol & 3 fatty acids.


What are the types of carbohydrates and what are they all made of?

Fibre, starch, glycogen and cellulose. All made of strings of glucose molecules.


What is diabetes?

A condition which affects ability to control levels of blood glucose. There are two types.


What is type 1 diabetes?

The pancreas produces little or no insulin, so glucose can rise to dangerous levels.


What is type 2 diabetes?

This is where someone becomes resistant to their own insulin. Their cells don't respond properly to it although they still produce it. This can cause blood glucose levels to rise dangerously.


How can type 1 diabetes be controlled?

Those with the disease need to regulate the simple carbohydrates they consume and need to be doing regular exercise.


What increases the chances of developing type 2 diabetes?



How can type 2 diabetes be controlled?

By eating a carbohydrate controlled diet and getting regular exercise.


How is type 1 diabetes treated?

Insulin therapy is needed, which involves several insulin injections a day, usually at mealtimes. This stops sugar levels getting too high. The amount of insulin that needs to be injected depends on diet and activity.


How many days long is the menstrual cycle?



What happens at puberty?

The body starts releasing sex hormones which trigger secondary sexual characteristics and cause eggs to mature in women.


Give 2 examples of secondary sexual characteristics.

Development of facial hair in men and breasts in women.


What are the stages of the menstrual cycle?

1. DAY 1-4: menstruation starts and the uterus lining breaks down for about 4 days.
2. DAY 4-14: uterus lining builds up into a thick layer full of blood vessels.
3. DAY 14: ovulation. An egg has developed and is released from the ovary.
4. DAY 14-28: the wall is maintained and waits for a fertilised egg. If this doesn't happen, the cycle repeats.


What four hormones control the menstrual cycle?

FSH (follicle-stimulating hormone), LH (luteinising hormone), oestrogen and progesterone.


What does FSH do and where is it produced?

Produced in the pituitary gland.
Causes an egg to mature in the ovary, in a structure called a follicle.


What does LH do and where is it produced?

-Produced in the pituitary gland.
-Stimulates ovulation at day 14.


What does oestrogen do and where is it produced?

-Produced in the ovaries.
-Causes the uterus lining to build up.
-Stimulates the release of LH and inhibits the release of FSH.


What does progesterone do and where is it produced?

-Produced in the ovaries, by the remains of the follicle after ovulation.
-Maintains the uterus lining during the second half of the cycle.
-Inhibits the release of LH and FSH.


What are the hormonal methods of contraception?

-The 2 pills: the combined oral contraceptive pill and the progesterone pill.
-The contraceptive patch.
-The contraceptive implant.
-The contraceptive injection.
-The intrauterine device (IUD).


How does the combined oral contraceptive pill work? What does it contain?

Oestrogen inhibits release of FSH so taking it every day will cause egg production and development to remain stopped.
Progesterone reduces fertility, e.g. by stimulating the production of thick mucus which blocks sperm from getting to the egg.


How does the contraceptive patch work?

-It contains oestrogen and progesterone.
-It is a 5x5cm patch stuck to the skin.
-It lasts one week.


How does the contraceptive implant work?

-Inserted under the skin of the arm.
-Can last for 3 years.
-Releases a continuous amount of progesterone, which:
--Inhibits release of FSH and LH (so eggs are not released).
--Makes it hard for sperm to swim to the egg.
--Stops any fertilised egg implanting in the uterus.


How does the contraceptive injection work?

Contains progesterone. This reduces fertility, e.g. by stimulating the production of thick mucus which blocks sperm from getting to the egg.


How does the intrauterine device work?

-It is a T shaped device inserted into the uterus.
-2 main types:
--plastic IUDs that release progesterone, preventing implantation of a fertilised egg.
--copper IUDs that prevent sperm surviving in the uterus.


What are the non-hormonal methods of contraception?

More drastic methods:
-The natural method


How do condoms work?

Can be worn over the penis/inside the vagina during intercourse to prevent sperm getting to the egg.
They protect against STIs.


How do diaphragms work?

They are shallow plastic cups that fit over the cervix (entrance to the uterus) to form a barrier.
Has to be used with a spermicide.


How do spermicides work?

They are substances which disable/kill sperm. They are only 70-80% effective.


What does sterilisation involve?

The fallopian tubes (which connect the ovaries to the uterus) or the sperm duct (the tube between the testes and penis) can be cut or tied.
This is permanent procedure but there is a small chance that the tubes can rejoin.


What is the natural method of contraception?

Pregnancy may be avoided by finding out when in the menstrual cycle a woman is most fertile. Sexual intercouse is avoided on these days.
The method is not very effective.


What is abstinence?

The act of not having sex- it is 100% effective.


Why can't some women get pregnant? What is a solution?

They have FSH levels too low to cause their eggs to mature. No eggs are released- they cannot be fertilised.
The hormones LH and FSH can be given in a fertility drug to stimulate ovulation.


What are the pros and cons of the fertility drug?

-doesn't always work
-too many eggs can develop, causing unexpected multiple pregnancies.


What does IVF treatment involve?

-FSH and LH are given before egg collection so that several eggs mature.
-Eggs are collected from a woman's ovaries and are fertilised with the man's sperm.
-ICSI (intracytoplasmic sperm injection), where the sperm is directly injected into the egg. This is useful for men with a low sperm count.
-The fertilised eggs are grown into embryos in a laboratory incubator.
-Once the embryos have become tiny balls of cells, one or two (to improve the chance of pregnancy) are transferred to the woman's uterus.


What are the cons of IVF treatment?

-Multiple births are possible, which risk miscarriages or stillbirths.
-Low success rate: 26% in the UK.
-Some women react strongly to the hormones, e.g. with abdominal pain, vomiting and dehydration.


What has improved the techniques of IVF treatment?

Advances in microscope techniques and micro tools, used for genetic testing (checking an embryo is healthy).


What is time lapse imaging and why is it important for IVF treatment?

A microscope and camera are built into the incubator. The growth of embryos can be monitored to determine those that are more likely to result in a successful pregnancy.


Why are some people against IVF treatment?

It often results in unused embryos being destroyed- this is considered unethical because they are potential human lives.
The genetic testing of embryos before implantation is believed to risk leading to the selection of preferred characteristics.


How do hormones prevent pregnancy?

They reduce fertility.


How do barriers prevent pregnancy?

They stop the egg and sperm meeting.


Why is homeostasis important for the body?

Cells need the right conditions to function properly, e.g. enzyme action.


What is negative feedback?

Receptors detect stimuli, like levels of a hormone being to high. The coordination centre organises a response and the effector produces a response which counteracts the change. The optimum level is restored.