Topic 5 - Homeostasis and Response Flashcards
What is homeostasis?
The process of maintaining a stable internal environment, despite changing conditions in order to maintain optimum conditions for enzyme and cellular function.
Why is it important to maintain a stable internal environment within the body?
So that our cells and enzymes can function optimally, and not get damaged.
Name 3 internal conditions that homeostasis regulates.
- Blood glucose concentration.
- Body temperature.
- Water levels.
(there are more, such as blood pH and ion levels)
What is the difference between internal conditions and external conditions?
- Internal conditions refer to the conditions inside the body, such as body temperature.
- External conditions refer to the conditions outside the body, such as room temperature.
What is the role of a receptor?
A receptor detects stimuli (a change in the internal or external environment).
What is the role of a coordination centre?
Interprets changes and organises a response.
Where are the coordination centres located in the body?
- Brain.
- Spinal Cord.
- Pancreas.
What is the role of an effector?
Brings about a response to restore optimum conditions.
What are the 2 types of effectors and what do they do when stimulated?
- Muscles contract.
- Glands release hormones.
What is the nervous system?
A complex network of nerves that carry messages from the brain and spinal cord to and from various parts of the body.
What is the endocrine system?
- Made up of glands that release hormones.
- These hormones act as chemical messengers that allow communication throughout the body.
What is negative feedback?
- When a change in a system causes an action that reverses the change.
- For example, a rise in temperature will cause a fall in temperature.
What are the key differences between the nervous system and the endocrine system?
Define Abstinence
Deliberately refraining from having sexual intercourse.
Define Adrenaline
A hormone that is produced by the adrenal glands in response to fear or stress which increases the heart rate and boosts the delivery of blood to the brain and muscles as a part of the ‘fight or flight’ response.
Define Contraception
Methods used to prevent pregnancy.
Define Coordination centres
Areas of the body like the brain, spinal cord and pancreas that receive and process information from receptors.
Define Effectors
Muscles or glands which bring about responses which restore optimum levels.
Define Follicle stimulating hormone (FSH)
A female reproductive hormone that causes the maturation of an egg in the ovary.
Define Gland
A group of cells that secrete chemicals called hormones directly into the bloodstream.
Define Glucagon
A hormone produced by the pancreas that causes glycogen to be converted into glucose and released into the blood.
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.
Define In Vitro Fertilisation (IVF)
Fertilising a woman’s egg using sperm outside of the body.
Define Luteinising hormone (LH)
A female reproductive hormone that stimulates the release of an egg.
Define Negative feedback cycle
A regulatory mechanism that reverses a change.
Define Oestrogen
The main female reproductive hormone which causes the uterus lining to grow and repair.
Define Receptors
Organs or cells that detect stimuli.
Define Reflex action
A rapid and automatic response to a stimulus.
Define Selective reabsorption
Reabsorbing certain useful molecules, like glucose, some ions and water, back into the blood after they have been filtered out.
Define Stimuli
Changes in the environment.
Define Target organ
The organ which a hormone acts on to produce an effect.
Define Testosterone
The main male reproductive hormone produced by the testes and it stimulates sperm production.
Define The central nervous system (CNS)
The brain and spinal cord which coordinate the response of effectors.
Define Thyroxine
A hormone produced by the thyroid gland that increases the metabolic rate in the body.
Define Type 1 diabetes
A disorder in which the pancreas fails to produce sufficient insulin which is characterised by uncontrolled high blood glucose levels.
Define Type 2 diabetes
A disorder where the body cells no longer respond to insulin produced by the pancreas.
Give examples of conditions maintained by homeostasis in the body.
- Blood glucose concentration.
- Body temperature.
- Water levels.
What 2 types of responses are used in body control systems?
Nervous and chemical.
What 3 components do all control systems have?
- Receptors
- Coordination centres
- Effectors
What is the function of a receptor?
Receptors detect changes in the environment (stimuli).
What is the function of a coordination centre?
Coordination centres obtain and process information from receptors.
What is the function of an effector?
Effectors, muscles or glands, bring about responses to stimuli.
What type of cells make up the nervous system?
Nerve cells, also known as ‘neurones’.
What is the central nervous system (CNS) composed of?
The brain and spinal cord.
What passes along nerve cells?
Electrical impulses.
What is the gap between nerve cells called?
A synapse.
How does a synapse transmit an electrical signal?
- When an electrical impulse reaches the end of a neurone, it causes the release of chemicals (neurotransmitters).
- These chemicals then diffuse across the synapse and stimulate the next neurone to carry another electrical impulse.
What is a reflex?
An automatic response to a stimulus.
Why are reflexes so fast?
Reflex actions are fast because they are automatic and don’t involve conscious parts of the brain.
Why is it important for reflexes to be rapid?
To protect us from harm.
What are the stages of a reflex arc?
- Stimulus
- Receptor
- Sensory Neurone
- Relay Neurone
- Motor Neurone
- Effector
- Response
What is the role of a receptor?
To detect a stimulus.
What is the role of a sensory neurone?
To transfer a signal from a receptor to the CNS.
What is the role of a relay neurone?
To transfer a signal from a sensory neurone to a motor neurone.
What is the role of a motor neurone?
To transfer a signal from the CNS to an effector.
What are the 2 main types of effectors?
- Muscles
- Glands
Which structure is indicated in the above diagram of the reflex arc?
Effector.
Which structure is indicated in the above diagram of the reflex arc?
Receptor.
Which structure is indicated in the above diagram of the reflex arc?
Relay neurone.
Which structure is indicated in the above diagram of the reflex arc?
Sensory neurone
What is the function of the nervous system?
The nervous system allows the body to react to its surrounding and coordinate an appropriate response.
How does a stimulus lead to a response being carried out by the body?
- Stimulus is converted into an electrical impulse by the receptors.
- The electrical impulse passes along sensory neurones to the central nervous system (CNS).
- The CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector, which carries out the response.
What is a reflex action?
A reflex action is an automatic and rapid response which does not involve any conscious input from the brain.
Describe how a reflex action occurs via a reflex arc
- The stimulus is detected by a receptor.
- An electrical impulse passes along a sensory neurone to the spinal cord (part of the CNS).
- At a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone.
- The same process occurs at a synapse between a relay neurone and a motor neurone.
- At the effector, an appropriate response is carried out.
What is the difference between a reflex pathway and a conscious pathway?
Within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/unconscious parts of the brain while in a conscious pathway, the coordination centre is in the conscious part of the brain.
Give the name of the body’s coordination system which involves hormones
The endocrine system.
What is a hormone?
A hormone is a chemical messenger secreted by a gland. It travels in the blood to a target organ, where it causes a response.
What type of organ secretes hormones?
Glands
Which gland controls many other glands in the body?
The pituitary gland.
Why is the pituitary gland considered a ‘master gland’?
It secretes a wide range of hormones, some of which may stimulate other endocrine glands.
What is the role of the pituitary gland in the endocrine system?
- Secretes human growth hormone - controls human growth.
- Stimulates the thyroid gland.
- Stimulates ovulation and the production of oestrogen in the ovaries.
- Stimulates the production of sperm and testosterone in the testes.
What is the role of the thyroid gland in the endocrine system?
Secretes the hormone thyroxine - controls metabolism, heart rate and body temperature .
What is the role of the pancreas in the endocrine system?
Secretes the hormone insulin - controls blood glucose levels.
What is the role of the adrenal gland in the endocrine system?
Secretes adrenaline - controls the body’s ‘fight or flight’ response.
What is the role of the ovaries in the endocrine system?
Secrete oestrogen, which coordinates the menstrual cycle and the development of female secondary sexual characteristics.
What is the role of the testes in the endocrine system?
Secrete testosterone, which coordinates the production of sperm and the development of male secondary sexual characteristics.
Which organ monitors and controls blood glucose concentration?
The pancreas.
How does the pancreas respond when blood glucose levels are too high?
The pancreas secretes the hormone insulin.
Insulin binds to receptors on the liver and muscles, causing excess glucose to be converted into glycogen and stored.
What is a gland?
A gland is an organ that releases small chemicals called hormones. These chemicals are typically released into the bloodstream, allowing them to travel around the body.
What is a hormone?
A hormone is small chemical, released by a gland, that binds to a receptor on a target cell.
How does the endocrine system work?
The endocrine system is a network of glands.
Glands release hormones, these are typically released into the bloodstream, allowing them to travel around the body.
They can then bind to specific cells that have the correct receptors. This will bring about some change within the cells.
What is a target cell?
A target cell is any cell that has the correct receptor for a particular hormone to bind to.
What is the pituitary gland?
The pituitary gland in the brain is known as the ‘ master gland’; it secretes several hormones into the blood in response to body conditions.
These hormones, in turn, act on other glands to stimulate other hormones to be released to bring about effects.
Which hormone do the adrenal glands secrete?
Adrenaline
What is the role of adrenaline?
The role of the adrenal gland is to prepare the body for exercise. It does this by:
1. Increasing heart rate.
2. Increasing breathing rate.
3. Increasing blood pressure.
What hormone does the thyroid gland secrete?
The thyroid gland releases thyroxine.
What is the role of thyroxine?
To increase metabolic rate. It also plays a role in growth and development.
Which hormone does the pituitary gland release to stimulate the thyroid gland?
Thyroid stimulating hormone (TSH).
Which hormone do the testes produce?
The testes produce testosterone.
Which hormone do the ovaries produce?
Oestrogen and progesterone.
What is glucose?
Glucose is a simple sugar molecule.
It is broken down during respiration to release energy.
What would happen to your blood glucose levels following a meal?
Blood glucose levels would rise.
What will the pancreas do if the blood glucose concentrations rise too high?
It will produce insulin and release it into the bloodstream.
What 2 things will insulin cause cells to do?
- Absorb glucose from the blood into the cells.
- Convert excess glucose into glycogen.
This mostly happens in liver and muscle cells.
What will the pancreas do if blood glucose concentrations fall too low?
It will produce glucagon.
What 2 things will glucagon cause cells to do?
- Break glycogen down into glucose.
- Release that glucose into the bloodstream.
This mostly happens in liver and muscle cells.
What are the 2 forms of diabetes?
- Type 1 diabetes.
- Type 2 diabetes.
What is type 1 diabetes?
Type 1 diabetes is a disorder in which the body’s immune system damages the pancreas so it can no longer produce sufficient insulin.
This leads to high blood glucose concentrations.
Which group of people does type 1 diabetes normally affect?
Young people, such as children and teenagers.
What is the treatment for type 1 diabetes?
- Mainly insulin injections.
- Maintain a good diet and do regular exercise.
What is type 2 diabetes?
Type 2 diabetes is a disorder in which body cells no longer respond to the insulin produced by pancreas.
This leads to high blood glucose concentrations.
Which group of people does type 2 diabetes normally affect?
Generally older people with poor diets, who don’t exercise regularly.
What is the treatment for type 2 diabetes?
- A strict diet with limited carbohydrates and regular exercise.
- Insulin and other medications are sometimes also required.
Is obesity a risk factor for type 1 or type 2 diabetes?
Obesity is a risk for type 2 diabetes.
What is puberty?
Puberty is the period in which adolescents start to develop secondary sexual characteristics.
What causes puberty?
Hormones.
Mainly testosterone in males and oestrogen in females.
What secondary sexual characteristics do males develop during puberty?
- Increase in height.
- Deepening voice.
- More muscle mass.
- Testes start producing sperm.
- Growth of public hair.
What secondary sexual characteristics do females develop during puberty?
- Increase in height.
- Breasts grow.
- Hips become wider.
- Menstrual cycle starts.
- Growth of public hair.
Which organ is testosterone released from?
Testosterone is released from testes.
Which organ is oestrogen released from?
The ovaries
What is the menstrual cycle?
The menstrual cycle is a series of steps that prepares the uterus for the implantation of a fertilised egg.
What is the name of stage one (days 0 to 4) of the menstrual cycle?
Menstruation
What is menstruation?
Period of bleeding as the uterus lining breaks down.
What happens in stage two (days 5 to 14) of the menstrual cycle?
The uterus lining builds up and gets thicker.
Why must the uterus lining be thickened during the menstrual cycle?
So that a fertilised egg can implant into the wall.
What is the name of stage three (day 14) of the menstrual cycle?
Ovulation
What is ovulation?
Ovulation is the release of an egg from an ovary.
What happens in stage four (days 15-28) of the menstrual cycle?
The uterus lining is maintained.
What happens after stage four of the menstrual cycle if no fertilised egg implants into the uterus lining?
The cycle repeats.
What happens after stage four of the menstrual cycle if a fertilised egg does implant into the uterus lining?
The menstrual cycle will pause and the lining will be maintained to allow the fertilised egg cell to develop.
What does FSH stand for?
FSH- Follicle Stimulating Hormone.
What does LH stand for?
LH- Luteinising Hormone.
Which organ are FSH and LH released from?
FSH and LH are released from the pituitary gland.
What is the role of FSH in the menstrual cycle?
It stimulate eggs in the ovaries to mature.
What is the role of LH in the menstrual cycle?
It stimulates a mature egg to be released from the ovary (ovulation).
What is the role of oestrogen in the menstrual cycle?
It stimulates the uterus lining to thicken during stage two.
What is the role of progesterone in the menstrual cycle?
It maintains the lining of the uterus after ovulation, during stage four.
Which organ is progesterone released from?
Progesterone is released from the ovaries.
What is contraception?
Contraception refers to any method or device that is used to prevent pregnancy.
Which 2 hormones do hormonal methods of contraception use?
Oestrogen and/or progesterone.
How does the steady release of oestrogen and/or progesterone prevent pregnancy?
- They inhibit the release of FSH, which means that egg can’t mature and be released.
- Progesterone also stimulates the production of cervical mucus, which blocks the passage of sperm and so stops it from reaching the egg.
Name 5 hormonal methods of contraception.
- Oral contraceptive pills (e.g. combined oral contraceptive pill, or the progesterone-only pill.)
- Skin patch.
- Injection.
- Implant.
- Intrauterine device (IUD).
What is the combined oral contraceptive pill?
- It is a pill containing oestrogen and progesterone to prevent pregnancy.
- It is 99% effective, but can have side effects such as headaches or nausea.
- The pill has to be taken every day for 21 days, followed by a 7-day break, then repeat.
What is the progesterone-only pill?
- It is a pill containing progesterone to prevent pregnancy.
- It is 99% effective, and often has fewer side effects than the combined oral contraceptive pill.
- The pill has to be taken every day.
What is a contraceptive skin patch?
- It is a patch that can be placed on the skin and slowly releases hormones to prevent pregnancy.
- Each patch lasts 1 week.
What is a contraceptive injection?
- It is an injection of hormones to prevent pregnancy.
- Each injection lasts roughly 3 months.
What is a contraceptive implant?
- It is a small device, injected under the skin, that slowly releases hormones to prevent pregnancy.
- Each implants last roughly 3 years.
What is an intrauterine device (IUD)?
- It is a small device, placed in the uterus, that slowly releases hormones to prevent pregnancy.
- Each IUD can last up to 5 years.
Name 7 non-hormonal methods of contraception.
- Condoms.
- Diaphragms.
- Copper.
- Intrauterine device.
- Spermicides.
- Abstaining from intercourse.
- Sterilisation.
Name 2 barrier methods of contraception. How do they work?
- Condoms and Diaphragms.
- Barrier methods work by preventing the sperm from reaching an egg.
- Condoms cover the penis.
- Diaphragms cover the cervix (entrance to the uterus).
What is a spermicide?
A chemical that kills sperm cells.
How does sterilisation work for males?
The sperm cord is cut and tied, so that sperm cannot be ejaculated.
How does sterilisation work for females?
The fallopian tubes (oviducts) are cut and tied, so that eggs from ovaries cannot reach the uterus.
What is infertility?
Infertility is when a couple cannot get pregnant (conceive) despite having regular unprotected sex.
What is the purpose of fertility treatment?
To help a person become pregnant.
What are the main 2 causes of female infertility?
- The eggs do not mature properly.
- The eggs are not released properly.
What is the main cause of male infertility?
The sperm cannot swim well enough to reach the egg.
Which 2 hormones are generally used in fertility treatment?
- Follicle stimulating hormone (FSH).
- Luteinising hormone (LH).
How can follicle stimulating hormone (FSH) help with infertility?
It stimulates the eggs in the ovary to develop and mature.
How can luteinising hormone (LH) help with infertility?
It stimulates eggs to be released (ovulation).
What does IVF stand for?
IVF-In Vitro Fertilisation.
What are the stages of In Vitro Fertilisation (IVF)?
- A woman is given FSH and LH to stimulate her eggs to mature.
- The eggs are collected from the woman’s ovaries.
- Sperm is gathered from the male .
- The eggs are then fertilised by the sperm in a laboratory to form zygotes.
5.The zygotes are then left to grow into embryos in a laboratory incubator. - Once the embryos are large enough, they are transferred to the woman’s uterus to develop into a foetus.
What is Intra-Cytoplasmic Sperm Injection (ICSI)?
Sperm is injected into an egg cell with a tiny needle. This is generally done when the sperm cells are not fit enough to swim to the egg cell themselves.
What are 5 drawbacks of IVF?
- There is a high chance of multiple births and associated complications.
- It can cause abdominal pain and vomiting.
- It has a low success rate (roughly 30%).
- It can be stressful and emotionally upsetting.
- It is expensive.
Why does some people think IVF is unethical?
- Some embryos (which had potential for human life) are destroyed.
- It could lead to ‘designer babies’ if parents can select embryos with specific traits.
Where is adrenaline released from?
Adrenaline is released from the adrenal glands.
What 4 effects does adrenaline have on the body?
- Increases heart rate.
- Increases blood pressure.
- Increases blood flow to muscles.
- Increases blood glucose concentrations.
How does adrenaline increase blood glucose levels?
Adrenaline stimulates liver cells to break glycogen down into glucose and release it into the bloodstream.
Where is thyroxine released from?
Thyroxine is released from the thyroid gland.
Where is the thyroid gland?
In the neck.
What does thyroxine do?
Thyroxine has lots of roles in the body, including growth and development, but the main role is to increase your metabolic rate (the rate at which chemical reactions are taking place).
Which hormone stimulates the thyroid gland to release thyroxine?
Thyroid stimulating hormone (TSH).
Which gland releases thyroid stimulating hormone (TSH)?
The pituitary gland.
What will cause the pituitary gland to release thyroid stimulating hormone?
Low levels of thyroxine cause the pituitary gland to release TSH.
