Paper 2 Topic 5 Flashcards
Define Homeostasis
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes.
Maintaining a stable internal environment despite changing conditions
What is the role of a receptor?
Detects changes in the internal or external environment
To detect a stimulus
What is the role of an effector?
Brings about a response in the body
What is the role of the coordination centre?
Interprets changes and organises a response
Your automatic control systems keep your internal environment stable using a mechanism called ________ ________.
Negative feedback
Why does the body need to maintain optimal conditions?
For optimal enzyme action and cell function.
What does homeostasis maintain? 3 types
Body temperature
Water levels
Blood glucose concentration
In what order are signals passed along the control system?
receptor ➔ coordination centre ➔ effector
Where are the coordination centres located in the body? give the 2
Brain
Spinal cord
Name the two types of effectors and state what they do.
Muscles contract and relax to bring about movement.
Glands release hormones.
What is the nervous system?
Relies on electrical impulses that can travel very quickly.
What is the endocrine syststem?
Releasing hormones into the blood stream, which means they spread throughout the entire body.
What happens in the negative feedback system?
Any change in a system causes an action that reverses the change.
Example
Whenever the levels of something get too high, they’re brought back down.
Whenever the levels of something get too low, they’re brought back up.
What passes along nerve cells?
Electrical impulses
What is the gap between two neurones called?
Synapse
What is released across a synapse?
Chemicals
What is the role of a sensory neurone?
To transfer a signal from a receptor to the CNS
What is the role of a motor neurone?
To transfer a signal from the CNS to an effector
What does CNS stand for?
Central Nervous System
What is the role of a relay neurone?
To transfer a signal from a sensory neurone to a motor neurone
What is a reflex?
An automatic response to a stimulus
What is the pathway of a reflex arc/ reflex pathway?
Stimulus ➔ receptor ➔ sensory neurone ➔ relay neurone ➔ motor neurone ➔ effector ➔ response
What are the two main types of effectors?
Muscles and glands
Give an example of a reflex:
1) Blinking when you get dust in your eye
2) Sneezing
Why are reflexes important?
They protect us from harm
What do glands do?
Glands are organs that release small chemicals called hormones.
How the endocrine system work? 4 steps
1) Glands release hormones
2) These chemicals travel around the body in the bloodstream
3) They bind to specific cells that have the correct receptors
4) This will bring about some change within the cells.
Give 2 facts about the pituitary gland:
1) It’s often referred to as the ‘master gland’
2) It releases multiple hormones
3) The hormones it releases control what other glands do
Which gland releases thyroxine?
Thyroid
What is the role of thyroxine?
Regulates metabolism
What happens if the level of thyroxine in the blood is too low?
If the level of thyroxine in the blood is too low, the pituitary gland will release more thyroid stimulating hormone (TSH).
What is the role of adrenaline?
Stimulates fight or flight response (higher heart rate etc)
Which organ is adrenaline released from?
Adrenal glands
Which organ is insulin released from?
Pancreas
Name 2 sex hormones that stimulate puberty:
Oestrogen
Testosterone
Which organ is testosterone released from?
Testes
Which organ is oestrogen released from?
Ovaries
What is a stimuli?
A change in the environment
What happens if blood glucose concentrations fall too low?
There won’t be enough glucose for tissue cells to respire
After eating, how does our blood glucose concentration change and why?
Blood glucose levels will increase after a meal as we absorb glucose from the food.
Which organ detects changes in blood glucose concentration?
Pancreas
Which hormone decreases blood glucose levels?
Insulin
What are the two main organs that insulin stimulates to absorb glucose from the blood?
Liver and muscles
When glucose is absorbed by the liver for long term storage, what molecule is it converted to?
Glycogen
1) When blood glucose levels fall too ___, it’s detected by the ________.
2) This causes the pancreas to release the hormone ________ into the bloodstream.
3) This hormone then travels around the body, and binds mainly to cells in the _____.
4) This stimulates those liver cells to break down their stored ________ into _______ and release it into the blood.
5) This extra glucose increases blood glucose levels back up to normal.
1) When blood glucose levels fall too low, it’s detected by the pancreas.
2) This causes the pancreas to release the hormone glucagon into the bloodstream.
3) This hormone then travels around the body, and binds mainly to cells in the liver.
4) This stimulates those liver cells to break down their stored glycogen into glucose and release it into the blood.
5) This extra glucose increases blood glucose levels back up to normal.
What is puberty?
The period in which adolescents start to develop secondary sexual characteristics.
Give 2 examples of secondary sexual characteristics
Increase in height
Deepening voice
More muscle mass
How long is the average menstrual cycle?
28 days
Stage 1?
Menstruation - Period of bleeding as the uterus lining breaks down
Stage 2?
Building up of the uterus lining
Stage 3?
Ovulation - Release of the egg from the ovaries
Stage 4?
Maintenance of uterus lining
What happens after stage four if there is no fertilised egg?
Cycle starts again
If a fertilised egg implants into the uterus lining then the menstrual cycle…
… stops and the lining is maintained.
Which hormone stimulates the uterus lining to develop?
Oestrogen
Which organ are both luteinising hormone (LH) and follicle stimulating hormone (FSH) released from?
Pituitary gland
Which hormone stimulates the egg to be released around day 14 (ovulation)?
Luteinising hormone (LH)
Which hormone stimulates the egg follicle to mature?
Follicle stimulating hormone (FSH)
Which hormone maintains the lining of the uterus?
Progesterone
What is contraception?
A method or device used to prevent pregnancy
Which hormones can hormonal contraceptives contain?
Oestrogen and Progesterone
How can oestrogen act as a contraceptive?
Inhibit FSH production, so that eggs can’t mature
How can progesterone act as a contraceptive?
Stimulate the production of mucus in the cervix, so sperm can’t enter the uterus
Does the combined oral contraceptive pill (‘the pill’) contain oestrogen, progesterone, or both?
Both
Which is longest and which is shortest lasting?
Intrauterine device
Contraceptive implant
Contraceptive injection
Contraceptive patch
Shortest: Patch
Longest: Device
How does a spermicide act as a contraceptive?
Destroys sperm cells
The diaphragm sits over the ______ to prevent sperm from entering the uterus.
cervix
If a women undergoes sterilisation, which structure is cut and tied?
Fallopian tubes / oviducts
If a man undergoes sterilisation, which structure is cut and tied?
Sperm duct
What does follicle stimulating hormone do?
Stimulate an egg to mature
What does luteinising hormone do?
Stimulate an egg to be released (ovulation)
If a woman cannot conceive naturally, she can be given ___ and __, which in many cases will restore fertility.
FSH
LH
IVF stands for:
In Vitro Fertilisation
The stages of in vitro fertilisation (5)
1) A woman is given FSH and LH to stimulate their eggs to mature.
2) These eggs can then be collected from the woman’s ovaries. Sperm is also collected from the male.
3) The eggs are then fertilised by the sperm.
4) These fertilised eggs are then left to grow into embryos in a laboratory incubator.
5) Once the embryos are large enough, they are transferred to the women’s uterus, so that they can develop into a foetus.
What is Intra-Cytoplasmic Sperm Injection (ICSI)?
Sperm is injected into an egg cell with a tiny needle
Why are embryos kept in an incubator whilst in the laboratory?
To provide the optimum temperature for enzymes and thus cell growth
Give 3 cons of IVF:
-> It can be stressful and emotionally upsetting
-> Can cause abdominal pain and vomiting
-> It doesn’t always work
-> High chance of multiple births and associated complications
Why do some people think IVF is unethical? Give 1
-> It could lead to ‘designer babies’ if parents can select embryos with certain traits
-> Some embryos (which had the potential for human life) are destroyed
During IVF, where are the egg and sperm mixed?
In a laboratory
Which organ is adrenaline released from?
Adrenal gland
When is adrenaline released?
When you’re scared
Adrenaline causes changes in the body to prepare for a ‘fight or flight’ response.
Give 3 of these changes.
Increase heart rate
Increase blood pressure
Increase blood flow to muscles
Increases blood sugar (glucose) levels
Adrenaline causes the conversion of which substances?
Glycogen ➔ glucose
Where is the thyroid gland located?
In the neck
What does thyroxine do?
Increase your metabolic rate (the rate at which chemical reactions are taking place).
How is the production of thyroxine regulated?
The pituitary gland produces Thyroid Stimulating Hormone (TSH), which stimulates the thyroid gland to produce thyroxine.
Thyroxine then inhibits the production of TSH from the pituitary gland.
What happens if thyroxine levels are -> too low?
-> too high?
1) If thyroxine levels are too low - the pituitary gland will release TSH. This then stimulates the thyroid gland to release more thyroxine. So thyroxine levels in the blood increase back up to normal.
2) If thyroxine levels are too high - the thyroxine will inhibit the pituitary gland from producing TSH. Less TSH means that the thyroid gland won’t release as much thyroxine. So thyroxine levels in the blood fall back to normal.
Which organ is TSH released from?
Pituitary gland
