B5:Homeostasis And Response Flashcards Preview

GCSE AQA BIOLOGY (PAPER 2) > B5:Homeostasis And Response > Flashcards

Flashcards in B5:Homeostasis And Response Deck (138):

What is Homeostasis?

Where your body maintains a constant internal environment.


Why is Homeostasis so important?

Because your cells need the right conditions to work properly.


You have loads of control systems that keep the conditions in your body steady. Give 4 examples:

1) keep your body temperature steady.2) blood glucose level steady.3) water level steady.4) salt level steady.


What are the control systems in your body like?

Automatic - you don't have to think about them.


What is used to help control conditions in the body?

The nervous systems or hormones.


What 3 parts are control systems made up of?

1) Receptors.2) Coordination centres (brain, spinal cord, pancreas)3) Effectors.


If the level of something in your body is too high, what does the control system do?

Decreases the level.


When the level of something in your body is too low, what does the control system do?

Increases the level.


What is a stimulus?

A change in the environment.


If the level of something changes, what happens? Step 1.

A receptor detects a stimulus and sends information to the COORDINATION CENTRE.


A receptor detects a stimulus and sends information to the COORDINATION CENTRE. Then what happens? STEP 2.

The coordination centre receives and processes the information and organised a response.


The coordination centre receives and processes the information and organised a response. Then what happens? STEP 3.

An effector produces a response and returns the level to its optimum level.


What does the receptor do?

Detects a stimulus (change in the environment.)


Give 3 examples of receptors and where they are found:

1) Light receptors - in eyes.2) Sound receptors - in ears.3) Smell receptors - in nose.


What does the NERVOUS SYSTEM mean we can do?

React to our surroundings and coordinate our behaviour.


What parts is the Nervous System made up of? (5)

1) Central Nervous System (CNS)2) Sensory Neurones.3) Motor Neurones.4) Receptors.5) Effectors.


What does the Central Nervous System consist of?

The brain and spinal cord.


How is the CNS connected to the body?

By sensory neurones and motor neurones.


What are neurones?

Nerve cells.


What do sensory neurones do?

They carry information as electrical impulses from the receptors on the CNS.


What do motor neurones do?

They carry electrical impulses from the CNS to the Effectors.


What do Effectors do?

They respond to electrical impulses and bring about a change.


Name the 2 Effectors:

Muscles and Glands.


How do the Effectors (muscle and glands) respond to electrical impulses?

Muscles contract & glands release hormones.


What are receptors?

Cells that detect stimuli. Different receptors detect different stimuli.


The CNS is a...

Coordination centre.


What does the CNS do when it receives information from receptors?

Decides what to do about it - coordinates a response which is carried out by the Effectors.


What is a synapse? (In Reflexes)

The connection between two neurones.


Why are Reflexes good?

They can help stop you getting injured because they are quick.


What is a Reflex Arc?

The passage of information from a receptor to the effector.


Where do the neurones in the reflex arcs go through?

The spinal cord or through an unconscious part of the brain. (The part of brain not involved in thinking)


Give the 7 bullet points that summarise how your CNS coordinates a response:

1) Stimulus.2) Receptor.3) Sensory Neurone.4) CNS.5) Motor Neurone.6) Effector.7) Response.


What is the only difference between Reflexes and CNS responses?

A relay neurone is involved instead of the CNS in Reflexes. The CNS doesn't coordinate the response.


Why does your body need to control the temperature in your body?

Because enzymes work best at specific temperatures - we don't want them to denature.


Why does your body need to control the amount of water in your body?

Because water is required for chemical reactions.


Why does your body need to control the amount of glucose in your body?

Because glucose is needed for energy.


Why does your body need to control the amount of ions inside (salt)?

Because ions are needed by the Nervous system.


What is reaction time?

The time it takes to respond to a stimulus.


How is Reaction Time measured?

Often less than a second so it is measured in milliseconds.


What can affect Reaction Time? (3)

Factors - age, drugs or gender.


How to measure reaction time: PRACTICAL:

Hold a ruler upright between someone's thumb and forefinger - they can't grip it. Let go and mark down where they catch it.


Reaction Time PRACTICALThe higher the number on the ruler the...

Slower their reaction time.


What do you need to make sure to do in the reaction time practical?

Repeat the test several times and calculate the mean distance that the ruler fell.


3 variables to keep the same in the ruler practical:

1) Same person to catch the ruler each time.2) Same hand to catch the ruler (left/right.)3) Ruler should be dropped from the same height.


What are hormones?

Chemical messengers that are released in the blood by glands.


What are the glands called that release hormones? What do they make up?

Endocrine glands - they make up your Endocrine System.


Where are hormones carried to?

To particular cells in particular organs - called target organs.


What is the Pituitary Gland sometimes called?

The master gland.


Why is the Pituitary Gland known as the master Gland?

Because it produces many hormones that regulate body conditions.


What do the Hormones released by the Pituitary Gland do?

Act on other glands - they make the glands release hormones that bring about change.


What do the Ovaries (glands) produce and what do they do?

Oestrogen - involved in the menstrual cycle.


What do the Testes (glands) produce and what do they do?

Testosterone- controls puberty and sperm production in males.


What do the Thyroid Glands produce and what do they do? (3)

Thyroxine - involved in regulating things like the rate of metabolism, heart rate and temperature.


What do the Adrenal Gland produce and what do they do?

Adrenaline - prepare the body for a ‘flight or fight’ response.


What does the Pancreas produce and what do they do?

Insulin - to regulate the blood glucose level.


What are nerves like compared to hormones? (3)

Very fast, work for a very short time and act on a very precise area.


What are hormones like compared to nerves? (3)

Slower action, act for a long time and act in a more general way.


What does eating carbohydrates put into your blood?

Glucose (a type of sugar).


How and when is glucose removed from the blood?

By cells - they use it for energy.


What happens when you exercise? Why?

A lot more glucose is removed from the blood - this is because more energy is needed as you exercise.


Changes in blood glucose concentration are monitored and controlled by...

The Pancreas.


What happens if the blood glucose concentration gets too high?

The Pancreas releases the hormone ‘Insulin.’


What does Insulin do to glucose in the blood?

It causes glucose to move into cells - so it removes glucose from the blood.


What can glucose be stored as? Where does this happen?



Where is Glucose converted to Glycogen?

In the liver and muscle cells.


Give the 4 steps to there being too much glucose in the blood:

1) Insulin released by the Pancreas.2) Glucose moves from the blood into liver and muscle cells.3) Blood Glucose is reduced.4) Insulin makes liver turn glucose into glycogen.


What are the two types of diabetes?

- Type 1 & Type 2.


Type 1 diabetes is when...

The Pancreas produces little or no Insulin.


What can happen to someone with type 1 diabetes?

Their blood glucose level can rise to a level that can kill them.


What do people with Type 1 diabetes need to do? What does this do?

Need injections of insulin through the day - makes sure that glucose is removed from the blood quickly after the food is digested.


Type 2 diabetes is where...

A person becomes resistant to their own insulin.


People with type 2 diabetes produce insulin, so what’s the problem?

Their body’s cells don’t respond properly to it.


What can happen to someone with Type 2 diabetes?

Their blood sugar level can rise to a dangerous level.


What can increase your chance of developing Type 2 diabetes?

Being obese.


Give 2 things that can help people with Type 2 diabetes:

1) they can eat a carbohydrates controlled diet.2) they can have regular exercise.


People with Type 2 diabetes can have a carbohydrate controlled diet to help them. What does this mean?

The amount of carbohydrates they eat is carefully measured.


How can reaction time be measured more accurately?

By a computer game - computers can give a more precise time and remove the possibility of the person predicting when to respond using the throwers body language.


Give the 4 steps to there being too little glucose in the blood:

1) Glucagon released by the Pancreas.2) Glucagon released into blood by liver.3) Blood Glucose is increased.4) Glucagon makes liver turn glycogen into glucose.


What does the body release when there is too little glucose in the blood?



At puberty, what does your body start to release?

Sex hormones.


What do sex hormones do? (They are produced at Puberty.)

They trigger the development of secondary sexual characteristics e.g. development of breasts in women.


What happens at STAGE 1 of the Menstrual Cycle?

Menstruation starts. The uterus lining breaks down for about 4 days.


What happens at STAGE 2 of the Menstrual Cycle?

The uterus lining builds up again, from day 4 to 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg.


What happens at STAGE 3 of the Menstrual Cycle?

An egg develops and is released from the ovary at day 14 - this is called Ovulation.


What happens at STAGE 4 of the Menstrual Cycle?What happens if an egg is not fertilised?

The wall is then maintained for about 14 days until day 28. If no fertilised egg has landed on the uterus wall by day 28 - The spongy lining starts to break down. Cycle starts again...


Name the 4 hormones that control the Menstrual Cycle:

1) Oestrogen.2) Follicle Stimulating Hormone. (FSH)3) Progesterone.4) Luteinising Hormone. (LH)


Where is Oestrogen produced?



Oestrogen causes... (2)Stimulates...Inhibits...

The lining of the uterus to grow.Stimulates the release of LH (which causes the release of an egg) and inhibits the release of FSH.


Progesterone is produced in...

The Ovaries by the remains of the follicle after ovulation.


Progesterone maintains.... (2)Inhibits....

The lining of the uterus during the second half of the cycle, when the level of progesterone falls, the lining breaks down.Inhibits the release of LH and FSH.


FSH is produced in the P...

The Pituitary Gland.


FSH causes...It stimulates... (2)

An egg to mature in one of the ovaries in a structure called a follicle.Stimulates the ovaries to produce Oestrogen.


LH is produced in the P...

The Pituitary Gland.


LH stimulates...

The release of an egg at day 14 (Ovulation.)


What can Oestrogen be used for?

To prevent the release of an egg.


How does Oestrogen work as a contraception?

If it is taken every day to keep the level of it permanently high, it inhibits the production of FSH and after a while egg development and production stop and stay stopped.


How can Progesterone be used to reduce fertility?

By stimulating the production of thick mucus which prevents any sperm getting through and reaching an egg.


What is ‘The Pill’ ?

It is an oral contraceptive containing Oestrogen and Progesterone (known as the combined oral contraceptive pill)


How effective is The Pill?

Over 99% at preventing pregnancy.


What are the side effects of the Pill? (3)

Headaches, nausea and it doesn’t protect from STI’s.


Is there anything you can use that has fewer side effects than The Pill?

Progesterone-only pill - fewer side effects and is just as effective.


The Contraceptive PATCH....

Contains Oestrogen and Progesterone and it’s small (5cm x 5cm) and is stuck to the skin = lasts 1 week.


The Contraceptive IMPLANT...It stops...It can last...

Inserted under the skin of the arm. Releases a continuous amount of Progesterone = stops ovaries from releasing eggs and makes it harder for sperm to swim to the egg and stops any fertilised eggs implanting in the uterus. Can last for 3 years


An Contraceptive INJECTION...

Also contains Progesterone. Each dose lasts 2/3 months.


An Intrauterine Device..It is...

A T shaped device that is inserted into the uterus to kill sperm and prevent implantation of a fertilised egg.


Give the 2 main types of Intrauterine Devices:

- Plastic ones that release Progesterone.- Copper ones that prevent the sperm from surviving in the uterus.


Non-hormonal forms of Contraception are designed to...

Stop the sperm from getting to the egg.


Condoms are worn over the penis or inside the vagina. What’s the purpose?

They prevent the sperm from entering the vagina and they are the only forms of Contraception that will protect from STI’s.


How is a Diaphragm used as a non-hormonal form of Contraception?It has to be used with...

- It is a shallow plastic club that fits over the cervix (entrance to the uterus) to form a barrier.- Has to be used with a spermicide (substance that disabled or kills sperm.


How effective is a Spermicide if it is used alone as a form of Contraception?

Not as effective - only about 70/80%.


Drastic ways to avoid Pregnancy:Sterilisation involves...

Cutting or tying the Fallopian tubes (which connect the ovaries to the uterus) in a female or the sperm duct (tube between testes and penis). Permanent procedure with a small change that the tubes can rejoin.


Drastic ways to avoid Pregnancy:‘Natural Methods’

Avoiding sex on days when a woman is more fertile - based on the Menstrual Cycle. Not very effective but popular with people who think hormonal and barrier methods are unnatural.


Drastic ways to avoid Pregnancy:Abstinence...

Don’t have sex so the sperm and egg definettly won’t meet.


Some women have levels of FSH that is too low... what does this mean?

Their eggs can’t mature and no eggs are released so the woman can’t get pregnant.


What can be given to a woman to stimulate Ovulation? What is this called?

FSH and LH - a fertility drug.


Give an advantage of a Fertility Drug:

It helps a lot of women get pregnant.


Give 2 disadvantages of Fertility Drugs:

1) It doesn’t always work so women have to do it many times - this can be expensive.2) Too many eggs can be stimulated resulting in unexpected multiple pregnancies.


If a woman cannot get pregnant using medication, what can she use?



What does IVF involve?

Collecting eggs from the woman’s ovaries and fertilising them in a lab using the man’s sperm.


IVF treatment can also involve a technique called....

Intra Cytoplasmic Sperm Injection.


What does Intra Cytoplasmic Sperm Injection (a type of IVF) involve? When can this be useful?

The sperm is directly injected into an egg - this is useful if the man has a very low sperm count.


What are the final stages of IVF? (2)

1) The fertilised eggs are then grown into embryos in a laboratory incubator.2) Once the embryos are tiny balls of cells, one or two are transferred to the uterus to improve the chance of pregnancy.


Give an advantage of IVF:

It can give an infertile couple a child.


Give 3 disadvantages of IVF:

1) Low success rate - 26% stressful.2) Multiple births can happen if more than one embryos turn into babies.3) Physically stressful - some women get reactions to hormones , vomiting dehydration etc.


Advances for IVF using microscope techniques:Specialised micro tools have....

Been developed to use on the eggs and sperm under the microscope. Also used to remove single cells from the embryo for genetic testing (to check that it is healthy.)


Advances for IVF using microscope techniques:The development of...

Time-lapse imaging means that the growth of the embryos can be continuously monitored to help identify those that are more likely to result in a successful pregnancy.


Why are some people against IVF? (2)

- Unused embryos are eventually destroyed = bad because potential human life.- Genetic testing of embryos before implantation means it could lead to the selection of preferred characteristics such as gender / eye colour.


Adrenaline is...

A hormone released by the adrenal glands which are just above the kidneys.


When is Adrenaline released?Your brain detects...

In response to scary or stressful situations - your brain detects fear or stress and sends nervous impulses to the adrenal gland which response by secreting adrenaline.


How does Adrenaline prepare the body for ‘fight or flight’ mode?

By triggering mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscles e.g. increasing heart rate.


Thyroxine is...

A hormone released by the thyroid gland which is in the neck.


What is the Metabolic rate?

The speed a which chemical reactions in the body occur while the body is at rest.


Thyroxine is released in response to....

Thyroid Stimulating Hormone which is released from the Pituitary Gland.


Describe the response if the level of thyroxine in the blood gets too high:

1) The production of thyroid Stimulating Hormone from the Pituitary Gland is stooped.2) This reduces the amount of thyroxine released from the thyroid gland so the level in the blood falls back towards normal.


What happens when a stimulus is detected by the receptors? (REFLEX) STAGE 1

Impulses are sent along the sensory neurone to a relay neurone in the CNS.


What happens when a stimulus is detected by the receptors? (REFLEX) STAGE 2When the impulses reach a synapse between the sensory neurone and the relay neurone....

They trigger the chemicals to be released and these chemicals cause impulses to be sent along the sensory neurone.


What happens when a stimulus is detected by the receptors? (REFLEX) STAGE 3When the impulse reach a synapse between the relay neurone and a motor neurone....

The same thing happens - chemicals are released and cause impulses to be sent along the motor neurone.The impulses then travel along motor neurone to the effectors.


What is a reflex?

Automatic responses that are really quick.