Topic 5: Homeostasis Flashcards
What is homeostasis?
Homeostasis is the regulations of conditions to maintain a stable internal environment
What are the main components your automatic control systems are made up of?
- receptors
- coordination centre
- effectors
When is negative feedback used?
When a level is too high or too low, your body uses negative feedback to return it back to normal
What is a stimulus?
A change in environment
Describe how the body uses negative feedback to return the level back to normal when the level is too high
- receptors detect a stimulus, level is too high
- coordination centre receives and processes the information and organises a response
- the effector carries out the response to counteract the change and restore its optimum level - the level decreases
Describe how the body uses negative feedback to return the level back to normal when the level is too low
- receptors detect a stimulus, the level is too low
- coordination centre receives and processes the information and organises a response
- the effector carries out the response to counteract the change and restore optimum level - the level increases
What is the central nervous system made up of?
The brain and spinal cord
What is the spinal cord and body organs connected by?
They are connected by nerves. Nerves are made up of neurones
What are the three neurones and what are their functions?
- sensory neurone - transmits signals from receptors
- relay neurone - transmits signals between neurones
- motor neurone - transmits signals to the effector
What are the two types of responses that occur when your body detects a stimulus?
Voluntary response and involuntary response (also known as a reflex action)
Why is the nervous system important in humans?
It allows us to react to our surroundings and coordinate our behaviour
What happens in the nervous system when a voluntary response occurs?
- stimulated receptor detects a stimulus and sends a signal to the sensory neurone
- the sensory neurone then carries the signal and sends it to the spinal cord and then the brain
- the brain receives and processes the information and sends a response via the motor neurone to the effector
- the effector carries out the response
What happens in the nervous system when an involuntary response occurs? (Also known as a reflex action)
- stimulated receptor detects a stimulus and sends a signal to the sensory neurone
- the sensory neurone then sends the signal to the relay neurone in the spinal cord
- the relay neurone then connects to the motor neurone so the response travels via the motor neurone to the effector
- the effector carries out the response
What are the features found in a nerve cell?
- nucleus
- cell body
- dendrites
- dendron (if signal sent towards cell body)
- axon (if signals are carried away from the cell body)
- insulating sheath
- axon terminal
- myelin
What are some features of neurones?
Neurones are like wires. They carry electrical signals and are long so that the signals can travel long distances
They have an insulating sheath to stop electrical signals jumping onto other neurons
What are synapses and what do they do?
Synapses connect neurones - the connection between two neurones
How do synapses connect to neurons?
- the connection between two neurons is called a synapse
- the nerve signal is transferred by chemicals which diffuse across the gap
- these chemicals then set off a new electrical signal in the next hormone
What are reflexes and what do they do?
Reflexes are rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain
What is a reflex arc?
The passage of information in a reflex (from receptor to effector) is called a reflex arc
The reflex arc goes through the central nervous system
Describe what happens when the reflex arc goes through the central nervous system
- cheeky bee stings finger
- stimulation of the pain receptor
- impulses travel along the sensory neurons
- impulses are passed along a relay neurone via a synapse
- impulses travel along a motor neurone via a synapse
- when impulses reach muscle, it contracts
What are the two hormones that control blood glucose level?
Insulin and glucagon
Give one example on how glucose is put into the blood
Eating foods containing carbohydrates puts glucose into the blood from the gut
What are two things that removes/ reduces glucose from the blood?
- metabolism of cells
- vigorous exercise
Where and what can excess glucose be stored as?
Excess glucose can be stored as glycogen in the liver and in the muscles
How are changes of the level of glucose in the blood monitored and controlled?
The level of glucose in the blood must be kept steady
Changes are monitored and controlled by the pancreas, using hormones insulin and glucagon
What happens when the blood glucose level is too high?
blood glucose level is too high - insulin is added
- blood with too much glucose
- insulin secreted by pancreas
- too much glucose but insulin as well
- glucose moves from blood into liver and muscle cells
- insulin makes the liver turn glucose into glycogen
-Body glucose reduced
What happens when the blood glucose level is too low?
Blood glucose level is too low - glucagon is added
- blood with too little glucose
- glucagon secreted by pancreas
- too little glucose, but glucagon as well
- glucose released into blood by the liver
- glucagon makes the liver turn glycogen into glucose
- blood glucose increases
What is diabetes?
The condition that affects your ability to control your blood sugar level
Describe the two types of diabetes
- Type 1: is where the pancreas produces little or no insulin
- Type 2: is where a person becomes resistant to their own insulin
Type 1 diabetes needs insulin therapy - what is insulin therapy?
Very effective treatment
Usually ensures several injections of insulin throughout the day
What does insulin therapy do?
Makes sure that glucose is removed from the blood quickly once the food has been digested, stopping the level getting too high
What do people with Type 1 diabetes need to keep in mind?
Limiting the intake of food rich in simple carbohydrates
Taking regular exercise
What can having type 2 diabetes cause?
Can cause a person’s blood sugar level to rise to a dangerous level
Give an example of what can cause type 2 diabetes
Being overweight increases the chance of developing type 2 diabetes, as obesity is a major risk factor
What can type 2 diabetes be controlled by and what do people with Type 2 diabetes need to keep in mind?
Can be controlled by eating carbohydrates, controlled diet and getting regular exercise
Describe the four stages of the menstrual cycle
Stage 1: Day 1 - menstruation starts - the uterus lining breaks down for about 4 days
Stage 2: the uterus lining builds up again, from day 4 to day 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg
Stage 3: An egg develops and is released from the ovary at day 14 - this is called ovulation
Stage 4: the wall is 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 again and the whole cycle starts again
What happens during puberty?
Your body starts releasing sex hormones that trigger off secondary sexual characteristics e.g. the development of facial hair in men and breasts in women
What’s the main reproductive hormone in men and how is it released?
In men, the main reproduction hormone is testosterone - it’s produced by the testes and stimulates sperm production
What’s the main reproductive hormone in women and how is it released?
In women, the main reproductive hormone is oestrogen - it’s produced in the ovaries
What are the four hormones the menstrual cycle is controlled by?
Oestrogen, FSH, LH, progesterone
What do the hormones FSH and Oestrogen do and where are they produced?
FSH (follicle - stimulating hormone):
- produced in the pituitary gland
- causes an egg to mature in one of the ovaries in a structure called follicle
- stimulates the ovaries to produce oestrogen
Oestrogen:
- produced in the ovaries
- causes 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
What do the hormones LH and Progesterone do and where are they produced?
LH (luteinising hormone):
- produced by the pituitary gland
- stimulated the release of an egg on day 14 (ovulation)
Progesterone:
- produced in the ovaries by the remains of the follicle after ovulation
- maintains the lining of the uterus during the second hand of the cycle
- when the level of progesterone falls, the lining breaks down
- inhibits the release of LH and FSH
Describe condoms and sterilisation surgery
Condoms:
- no hormones involved - barrier
- advantages: cheap and highly effective
- disadvantages: might be allergic, might tear
Sterilisation surgery:
- no hormones involved - culturing the ovarian duct and testes
- advantages: non-hormonal
- disadvantages: can’t reverse
Describe oral contraceptives and implants
Oral contraceptives:
- hormones involved - releases oestrogen and progesterone, so FSH and LH can’t be released
- advantages: free in the UK, very effective
- disadvantages: causes illness and weight gain, doesn’t protect against STDs
Implants:
- hormones involved - high levels of oestrogen and progesterone to prevent LH and FSH
- advantages: convenient
- disadvantages: side effects, doesn’t protect sexual transmitted infection
Describe copper UD
- no hormones - prevents implantation
- advantages: convenient
- disadvantages: painful periods
What is the eye? Name all the several parts in the eye
The eye is a sense organ
Several parts found in the eye: the sclera, the cornea, the iris and pupil, the lens, the ciliary muscles and suspensory ligaments, the optic nerve
What is the function of the cornea?
The transparent outer layer found at the front of the eye
It refracts light into the eye
What is the function of the suspensory ligaments?
Controls the shape of the lens
What is the function of the sclera?
The tough, supporting wall of the eye
What is the function of the optic nerve?
Carries impulses from the receptors on the retina to the brain
What is the function of the ciliary muscles?
Controls the shape of the lens
What is the function of the retina?
Contains receptor cells sensitive to light intensity and colour
What is the function of the lens?
Focuses the light onto the retina (which contains receptor cells sensitive to light intensity and colour)
What is the function of the iris?
controls how much light enters the eye ( contains muscles that control the diameter of the pupil)
Describe what happens when light receptors in the eye detect a very bright light
- a reflex is triggered that makes the pupil smaller
- circular muscles in the iris contract
- the radial muscles relax
- this reduces the amount of light that can enter the eye
Describe what happens when light receptors in the eye detects dim light
- a reflex is triggered that makes the pupil smaller
- circular muscles in the iris relax
- radial muscles contract
- the pupil gets wider
Describe the term accommodation
The eye focuses light on the retina by changing the shape of the lens - this is known as accommodation
Describe what happens when the eye focuses on near objects
- the ciliary muscles contract
- which slackens the suspensory ligaments
- the lens becomes fat (more curved)
- this increases the amount by which it refracts light
Describe what happens when the eye focuses on distant objects
- the ciliary muscles relax
- which tightens the suspensary ligaments
- the lens is less curved (thin)
- less amount of light is refracted
What happens when the lens cannot refract the light by the right amount?
If the lens cannot refract the light by the right amount (so that it focuses on the retina) the person will be short or long-sighted
Describe and explain why people become long-sighted
-occurs when the lens is the wrong shape
- not enough light is refracted or the eye-ball is too short
- the image of near objects are brought into focus behind the retina
What lens can help someone who is long-sighted?
Glasses with a convex lens (a lens which curves outwards) can be used to correct long-sighted people
The lens refracts the light rays so they focus on the retina
What is the medical term for long-sightedness?
Hyperopia
What does it mean to be long-sighted?
Long-sighted people are unable to focus on near objects
Describe and explain why people become short-sighted?
- occurs when the lens is the wrong shape
- too much light is being refracted or the eye-ball is too long
- the image of distant objects are brought into focus infront of the retina
What lens can help someone who is short-sighted?
Glasses with a concave lens (a lens which curves inwards) can be used to correct it, so that the light rays focus on the retina
What is the medical term for short-sightedness?
Myopiea
What does it mean to be short-sighted?
Short-sighted people are unable to focus on distant objects
Name 3 treatments for vision defects
Contact lenses (2 types - hard and soft)
Laser-eye surgery
Replacement lens surgery
Describe how contact lenses work
Thin lenses that sit on the surface of the eye, are shaped to compensate the fault in focusing
What are the advantages for contact lenses?
- they are light-weight and almost invisible
- more convenient when playing sport
What are the disadvantages for contact lenses?
- soft lenses are more comfortable, but carry a higher risk of eye infections than hard lenses
Describe how laser-eye surgery works
- can be used to vaporise tissue, changing the shape of the cornea
- improves short sight - slims it down, makes it less powerful
- improves long sight - changing the shape so it’s more powerful
What are the advantages of laser eye surgery?
Surgeons can precisely control how much tissue the laser takes off, completely correcting vision
What are the disadvantages of laser eye surgery?
- eye can get infected
- reaction in the eye that makes your vision worse than before
Describe how replacement lens surgery works
Natural lens of eye is removed and an artificial lens, made of clear plastic, is inserted in its place
What are the advantages of replacement lens surgery?
- is more effective when treating long-sightedness (rather than alternating the shape of the cornea with laser eye surgery)
What are the disadvantages of replacement lens surgery?
Involves work inside the eye:
- replacing a lens carries higher risks than laser eye surgery
- possible damage to the retina - lead to loss of sight
What do the kidneys do?
Kidneys act as filters to clean blood
They make urine by taking waste products (and other unwanted substances) out of the blood
What is the process of filtration in the kidneys?
Due to high pressures, small molecules are filtered out of the blood and pass into the nephron
Describe what happens in selective reabsorption
The kidneys selectively reabsorb only those molecules which the body needs back in the bloodstream
What are the substances that are removed from the body in the urine?
Urea, ions, water
For the beginning of the process to form urea, what can’t be stored by the body?
Proteins (and amino acids that they are broken down into)
What are amino acids converted into to be able to be stored by the body?
Any excess amino acids are converted into fats and carbohydrates
When amino acids are being converted into fats and carbohydrates, where does this occur and what is the process known as?
Occurs in the liver and involves a process known as deamination
What is produced as a waste product from deamination?
Ammonia
Why can’t ammonia be stored?
Ammonia is toxic, so it is converted into urea in the liver
What happens to urea after being formed?
Urea is then transported to the kidneys, where it is filtered out of the blood and excreted from the body in urine
How can urea also be lost?
A small unregulated amount of urea is also lost from the skin in sweat
How are ions taken into the body?
Ions such as sodium ions are taken into the body in food, and then absorbed into the blood
What does it mean if the ion (or water) content of the body is wrong?
Upsets the balance between ions and water, meaning too much or too little water is drawn into cells by osmosis
What effects of having the wrong amount of water do to your body?
Can damage cells or mean they don’t work as well as normal
How can some ions be lost?
Lost in sweat - this amount is not regulated, so the right balance of ions in the body must be maintained by the kidneys
Describe what happens to the right amount of ions
The right amount of ions is reabsorbed into the blood after filtration and the rest is removed from the body in urine
What does the body have to do with water?
The body has to constantly balance the water coming in against the water going out
How do we lose water?
We lose water from the skin in sweat and the lungs when breathing out
Since we can’t control how much water we lose, what do our bodies do?
The amount of water is balanced by the amount we consume and the amount removed by the kidneys in urine
What is the concentration of urine controlled by?
concentration of urine is controlled by a hormone called anti-diuretic hormone (ADH)
Where is ADH released?
Released into the bloodstream by the pituitary gland
What does the brain do when ADH is being released?
The brain monitors the water content of the blood and instructs the pituitary gland to release ADH into the blood according to how much is needed
What is the whole process of water content regulation controlled by?
Negative feedback - means that if water content gets too high or too low, a mechanism will be triggered that brings it back to normal
In terms of negative feedback, how does the body respond if the water content is too high?
- a receptor in the brain detects that the water content is too high
- the coordination centre in the brain receives the information and coordinates a response
- the pituitary gland releases less ADH, so less water is reabsorbed from the kidney tubules, water content decreases
In terms of negative feedback, how does the body respond if the water content is too low?
- a receptor in the brain detects that the water content it took low
- the coordination centre in the brain receives the information and coordinates a response
- the pituitary gland releases more ADH , so more water is reabsorbed from the kidney tubules, water content increases
What is dialysis?
The machine used to filter a patient’s blood
What does the dyalisis need to be in order for it to work?
Sterile and at body temperature
What are the disadvantages for dyalisis?
Inconvenient
Diet restrictions
Increase risk of infections
Very expensive
What are the disadvantages of kidney transplants?
Major surgery involved
Must be a ‘match’ - waiting for a doner
Problem of rejection
Immunosuppressant drugs must be taken
What are some reasons for infertility?
STDs can make you infertile
Blocked fallopian tubes
Older mothers
Male infertility
Ovarian cysts make it difficult for an ovary to make an egg
Premature menopause
Thyroid problems
Medicines and drugs
Low sperm count or deformed sperm
Too much alcohol
What is infertility in males?
Poor quality semon
Scarring from surgery on the reproductive organs
Side effects of other medical treatments
Low levels of testosterone
What is infertility in females?
Problems during ovulation
Scarring from surgery on the reproductive organs
Endometiosis
Side effects of other medical treatments
Describe the process of IVF
- FSH and LH increase fertility by stimulating ovulation and maturation - the mother has to take drugs to release FSH and LH to release eggs
- the egg is then collected through surgery and is fertilised by the father in a petri-dish
- 1-2 embryos are then inserted back into the mother’s uterus
What are the advantages of IVF?
- allows people to have babies of their own
- embryos can be screened for genetic diseases
- unused eggs can be donated to other couples
What are the disadvantages of IVF?
- side effects of the fertility drugs
- possibility of multiple pregnancies
- emotionally and physically stressful
- low success rate
- expensive
- excess embryos may be destroyed
Where is thyroxine produced?
The thyroid gland
Where is adrenaline produced?
Adrenal gland
What does thyroxine do?
- stimulates the body’s basal metabolic rate - it increases the metabolism of all the body’s cells
- also controls our growth and development - starting in the uterus
- stimulates protein synthesis - responsible for growth and development
- also involved in the development of animals
When is adrenaline released?
When we are excited or frightened
What does adrenaline do?
- raises our body temperature
- increases heart rate, increases breathing rate
- sends more blood to the muscles and the brain
- increases sugar levels
- dilates the pupils so more light enters the eye
What happens to the release of adrenaline when our body temperatures get too high?
The hormones’ secretion is blocked
What are auxins?
a plant hormone that causes cells to elongate and promotes cell division
Name the three tropisms and their stimulus
Geotropism: stimulus - gravity
Hydrotropism: stimulus - water
Phototropism: stimulus - light
Other than auxins, what are 2 other plant hormones?
Ethene
Giberellins
Describe what happens during phototropism
- auxins are highly concentrated on the shaded side of the stem
- auxins stimulate cell elongation and the shaded side of the shoot will grow faster than the unshaded side
- this causes the shoot to bend towards the light
Why do weed killers contain auxins?
Higher concentrations of auxins disrupt cell metabolism and kill plants
Plants with broad leaves are more susceptible to auxins than plants with narrow leaves
So farmers can kill weeds in a field
What can auxins be used for in industry?
Weed killers
Rooting powders
Promoting growth in tissue culture
How can the ripening of fruits be controlled?
- fruit can be picked unripe
- fruit can be transported at cool temperatures to reduce ethene production
- fruit can then be sprayed with ethene to ripen, then ready to go on the shelves
What do giberellins do?
- giberellins are involved in seed germination
- they can be used to increase fruit size, promote flowering, and end seed dormancy
What is urine formation in the kidneys?
The molecules which are not selectively reabsorbed (the urea, excess warmer and ions) from urine
Describe what happens when ADH is released when hydrated
- ADH is released by the pituitary gland
- ADH causes more water to be reabsorbed and concentrated urine to form
- when hydrated, less ADH is released and diluted urine is produced
- this is an example of negative feedback
Describe what happens when ADH is released when dehydrated
- ADH is released by the pituitary gland
- ADH causes more water to be reabsorbed and concentrated urine to form
- when dehydrated, more ADH is released and concentrated urine is produced
- this is an example of negative feedback
Name the different parts found in the brain
Cerebrum
Hypothalamus
Medulla oblongata
Cerebellum
Spinal cord
What does the cerebrum control?
Intelligence
Memory
Speech
Emotion
Vision
What does the hypothalamus control?
Regulates temperature
What does the medulla oblongata control?
Controls unconscious activities e.g. heart rate
What does the cerebellum control?
Controls balance and coordination
What is the thermoregulatory centre and what does it do?
The thermoregulatory centre is in the hypothalamus of the brain. It detects the temperature of the blood flowing through it
If body temperature rises this triggers vasodilation
Describe what happens during vasodilation
- blood vessels dilate allowing more blood to flow to capillaries in the skin
- more blood flows through capillaries close to the surface of the skin
- rate of heat loss from the body increases
- less blood is stunted away
If body temperature decreases this triggers vasoconstriction
Describe what happens during vasoconstriction
- smooth muscle in wall of arteriole contracts
- more blood flows through capillaries away from the surface of the skin less blood flows through capillaries nearer to the surface of the skin
- rate of heat loss from body decreases
- so more heat is lost
