P2- Homeostasis and response Flashcards
What is homeostasis?
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
Two examples of automatic control systems
Chemical (hormonal) and Nervous sytem
Examples of internal body conditions
Body temperature, blood sugar levels, blood pH, water concentration
What are the three main components of the automatic control system?
Receptor, effector and coordination centre
What is a receptor?
A cell that detects a stimulus
What is the coordination centre?
Receives and processes the information and organises a response
What is an effector?
The muscle (nervous) or gland (chemical) that produces a response to restore the optimum level by counteracting the change
What is a stimulus?
A change in environment
What are hormones?
Chemical messengers which are used in the body by the endocrine system, co-ordinate our organs and are produced by the glands.
What is the endocrine system?
Composed of glands which secrete hormones directly into the bloodstream
What is the blood’s role in the endocrine system?
Carry the hormones to a target organ where it produces an effect
Examples of what hormones control
Growth, sexual development, sugar levels, mood, metabolism
Which gland in the brain is the ‘Master Gland’?
Pituitary gland
What does the nervous system allow us to do?
The nervous system allows us to detect and react to changes in the environment. Humans can react to their surroundings and coordinate their behaviour
What are the 4 parts of the Nervous system?
Central nervous system (CNS), Sensory neurone, motor neurone and effector
What is the role of the Central Nervous (CNS)?
A coordination centre which receives information from the receptor and coordinates a response (which is carried out by the effector)
What is the Central Nervous system (CNS) made up of?
Brain and spinal cord only
What is the role of the sensory neurone?
Carry information as electrical impulses from the receptors to the CNS
What is the role of the motor neurone?
Carry information electrical impulses from the CNS to the effectors
What is a synapse?
The connection between two neurones where the impulses need to pass through
How does a synapse work?
1) When an electrical impulse reaches the end of an axon entering the synapse, the axon releases chemicals.
2) The chemicals diffuse across the gap.
3) These chemicals then set off a new electrical signal in the next neurone
What are reflexes?
Rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain
What is a benefit of having reflexes?
They can reduce the chances of injury
Give an example of one of your body’s reflexes that reduce injury
Your pupils automatically get smaller when bright light is shone on them to prevent the pupils getting damaged
What is the Reflex Arc?
The passage of information in a reflex
Stages of the Reflex Arc (full)
1) The stimulus (e.g a pin prick)
2) Pain receptors in the skin are stimulated
3) Nerve impulse travels along sensory neurone
4) Nerve impulse enters spinal cord
5) Nerve impulse passes across synapse into a relay neurone
6) Nerve impulse passes into motor neurone and travels along this, out of the spinal cord
7) When nerve impulse reaches finger, muscle (effector) contracts, pulling the finger away (response)
Stages of the reflex arc (words)
Stimulus- Receptor- Sensory neurone- Synapse- Relay neurone- Motor neurone- Effector- Response
What is reaction time?
The time it takes to respond to a stimulus
Examples that can affect reaction time?
Age, gender, drugs (e.g caffeine)
What is the role of the brain?
It controls complex behaviour, is part of the Control nervous system (CNS), made up of billions of interconnected neurones
Role of the cerebral cortex/cerebrum in the brain?
(Outer wrinkly bit) Responsible for conscious activity like memory, language/speech, thoughts, vision, intelligence
Where is the cerebral cortex/cerebrum located in the brain?
The top of your brain
Role of the cerebellum in the brain?
Resposible for muscle coordination and movement
Where is the cerebellum located in the brain?
Lower back of the brain
Role of the medulla (oblongata) in the brain?
Responsible for unconscious activity like your heart rate and breathing rate
Where is the medulla located in the brain?
Base/bottom part of the brain (connected to spinal cord)
Role of the hypothalamus?
To control the centre monitoring brain and helps maintain homeostasis
Where is the hypothalamus located?
In the brain
Role of the pituitary (master) gland?
Responsible for regulating many body functions and the activity of other glands
Where is the pituitary gland located?
In the brain
3 ways of treatment to study the brain
1) Studying patients with brain damage
2) Electrically stimulating different parts of the brain
3) Using MRI (magnetic resonance imaging) scanning techniques
What is the eye?
The eye is a sense organ containing receptors that are sensitive to light intensity and colour.
What is accommodation?
The process of changing the shape of the lens to focus on near or distant objects.
What is the retina in the eye?
A layer of cells at the back of the eye
Role of the retina in the eye
Contains receptors that are sensitive to light intensity and colour
Role of the sclera in the eye
The tough white outer layer of the eye which helps protect the eye from injury
Role of the cornea in the eye
The transparent outer layer at the front of the eye which refracts light (light bends as it enters the eye)
Role of the iris in the eye
Contain muscles which control the diameter/size of the pupil and therefore how much light enters the pupil
Role of the lens in the eye
Focuses the light onto the retina
Role of the ciliary muscles in the eye
Contracts or relaxes to move the suspensory ligaments
Role of the suspensory ligaments in the eye
Pulls the lens thin or allows the lens to widen
Role of the optic nerve in the eye
Carries impulses between the eye and the brain
What are the two types of muscles in the eye?
Circular muscles and radial muscles
Where are the circular and radial muscles found?
Iris
What happens to the eye in dim/low light?
1) Circular muscles in the iris relax
2) Radial muscles in the iris contract
3) Pupil dilates
4) More light enters the eye
What happens to the eye in bright light?
1) Circular muscles in the iris contract
2) Radial muscles in the iris relax
3) Pupil constricts
4) Less light enters the eye
What happens if a person’s lens cannot refract the light by the right amount?
They are either short or long sighted
Long sighted people are unable to focus on…
Near objects
What is the scientific name for long-sightedness?
Hyperopia
What happens in the lens of someone who is long-sighted (hyperopia)?
Their eyeball is too short/ lens cannot be thickened enough. The light rays aren’t refracted enough and the image of near focus objects are brought into focus behind the retina
How is being long-sighted (hyperopia) fixed?
Using convex lenses
How does the eye focus on near objects?
1) Ciliary muscles contract and have a smaller diameter
2) Suspensory ligaments loosen
3) Lens is then thicker, becomes more convergent which refracts light rays strongly onto the retina
Short sighted people are unable to focus on…
Distant objects
What is the scientific name for short-sightedness?
Myopia
What happens in the lens of someone who is short-sighted (myopia)?
Their eyeball is too wide/lens overthickens. The light rays refract too much and focus infront of the retina
How is being short-sighted (myopia) fixed?
Using concave lenses
How does the eye focus on distant objects?
1) Ciliary muscles relax and have a wider diameter
2) Suspensory ligaments pulled tight
3) Lens is then pulled thin, becomes more divergent which only slightly refracts light rays onto the retina
4 treatments for people with vision defects
1) Spectacle lenses (Glasses/ convex or concave)
2) Contact lenses (hard or soft)
3) Laser eye surgery (change shape of cornea)
4) Replacement lens surgery (artificial lens inserted)
What is a human’s optimum body temperature and why?
37 degrees as its the optimum temperature for enzymes to work in the body
What is the thermoregulatory centre?
Acts as a coordination centre, contains receptors that are sensitive to the temperature of blood flowing through the brain, receive impulses from temperature receptors in the skin
Where is the thermoregulatory centre located in the brain?
In the hypothalamus which is in the brain
What happens if body temperature is too high?
1) Temperature receptors decect body is too hot
2) Thermoregulatory centre receives info from receptors and triggers effectors automatically
3) Effectors (e.g sweat glands) produce a response to counteract the change
How do the effectors respond when you’re too hot?
1) Sweat produced by sweat glands and evaporates from skin which transfers energy to the surroundings
2) Vasolidation- Blood vessels supplying the skin dilate so more blood flows closer to surface of the skin
How do the effectors respond when you’re too cold?
1) Hairs stand up to trap an insulating layer of air
2) No sweat produced
3) Vasoconstriction- Blood vessels supplying capillaries constrict to close off skin’s blood supply
4) Respiration is needed when you shiver which transfers some energy to warm the body
6 examples of glands that make up the endocrine system
1) Pituitary (master) gland
2) Thyroid gland
3) Ovaries (females only)
4) Testes (males only)
5) Adrenal gland
6) The pancreas
Role of the thyroid gland
Produces thyroxine which regulates things like metabolic rate, heart rate and temperature
Role of the adrenal gland
Produces adrenaline, preparing the body for ‘fight or flight’
Role of the ovaries
Produces oestrogen which is involved in the menstrual cycle
Role of the testes
Produces testosterone which controls puberty and sperm production in males
Role of the pancreas
Produces insulin which regulates the blood glucose level
3 differences between nerves (N) and hormones (H)
1) N: Very fast action, H: Slower action
2) N: Act for short time, H: Act for long time
3) N: Act on precise area, H: Act in more general way
What two hormones control blood glucose levels?
Insulin and glucagon
How are blood glucose monitored and controlled?
By the pancreas, using insulin and glucagon, in a negative feedback cycle
What is a negative feedback cycle?
The correction process to maintain optimum internal body conditions
What happens if the blood glucose level is too high?
1) Insulin is secreted by the pancreas into the blood
2) Insulin + glucose move from blood into liver and muscles
3) Insulin makes liver turn glucose into glycogen
4) Blood glucose is reduced, levels back to normal
What is the role of insulin?
Remove glucose from the blood
What happens if blood glucose is too low?
1) Glucagon is secreted by the pancreas into the blood
2) Glucagon+glycogen move from blood to liver and muscles
3) Glucagon makes liver turn glycogen into glucose
4) Blood glucose is increased, levels back to normal
What is the role of glucagon?
Increases your blood glucose level and prevents it from dropping too low
What is diabetes?
A condition that affects YOUR ability to control YOUR blood glucose level.
What is Type 1 Diabetes?
-Pancreas fails to produce sufficient insulin
-Uncontrolled high blood glucose levels
-Need several insulin injections throughout the day to make sure glucose is removed quickly once food has digested to stop the levels getting too high
-Amount of insulin injected depends on a person’s diet and activity
-Limit intake of food rich in simple carbohydrates (sugars)
-Regular excercise
What is Type 2 Diabetes?
-Person becomes resistant to their own insulin
-Body cells no longer respond to the insulin produced by the pancreas
-Controlled by eating a carbohydrate-controlled diet and regular exercise
-Obesity is a major risk factor of type 2 diabetes
What is the role of the kidneys?
They make urine by taking/filtering waste products out of your blood. This process is called filtration.
What is selective reabsorption?
Useful substances like glucose, some ions and the right amount of water are absorbed back into the blood whilst the waste products are filtered out
3 substances removed from the body in the urine
Urea
Ions
Water
How and why is urea filtered out by the kidneys? (6 steps)
1) Proteins and amino acids can’t be stored in the body
2) Any excess amino acids are converted into fats and carbohydrates, which can be stored
3) This occurs in the liver and involves a process called ‘Deamination’
4) Ammonia is produced as a waste product from this process
5) Ammonia is toxic, converted to urea in the liver
6) Urea transported to kidneys where its filtered and excreted
How and why are ions filtered out by the kidneys? (4 steps)
1) Ions like sodium are taken into body by food and then absorbed into the blood
2) If ion (or water) content of the body is wrong, it could upset the balance between ions and water meaning too much/little is drawn into cells by osmosis
3) Having the wrong amount of water can damage cells or mean they don’t work as well
4) The right amount of ions is reabsorbed into the blood after filtration and the rest is removed from the body in urine
How and why is water filtered out by the kidneys?
1) Body has to constantly balance water coming in against water going out
2) We lose water from the skin in sweat and from the lungs when breathing out
3) We can’t control how much we lose in these ways, so the amount of water is balanced by the amount we consume and the amount removed by the kidneys in the urine
What hormone controls the concentration of urine?
Anti-diuretic hormone (ADH)
Where is ADH released from?
Pituitary gland
What happens if a person’s water content/level is too high?
1) The receptor detects high water level
2) The coordination centre coordinates a response
3) Pituitary gland releases less ADH, so less water is reabsorbed from the kidney tubules
What happens if a person’s water content/level is too low?
1) The receptor detects low water level
2) The coordination centre coordinates a response
3) Pituitary gland releases more ADH, so more water is reabsorbed from the kidney tubules
2 treatments for a kidney failure
1) Dialysis treatment
2) Kidney transplant (the only cure)
Why does dialysis have to be done regularly? (2)
1) To keep the concentrations of dissolved substances in the blood at normal levels
2) To remove waste substances
How does a dialysis machine work? (3 steps)
1) The person’s blood flows between partially permeable membranes surrounded by dialysis fluid
2) Dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood meaning they won’t be lost from the blood during dialysis
3) Only waste substances and excess ions and water diffuse across the barrier
3 negatives of kidney dialysis
1) They happen 3 times a week for 3-4 hrs each
2) May cause blood clots or infections
3) It is expensive for the NHS to run
1 positive of kidney dialysis
It can buy a patient valuable time until a donor organ is found
2 risks of kidney transplants
1) It can be risky if the person donating one of their kidneys is still alive (infection, blood clots)
2) The donor kidney could be rejected by the person’s immune system
Why are kidney transplants better than kidney dialysis?
They are cheaper in the long run
What is the menstrual cycle?
The monthly hormonal cycle a female’s body goes through to prepare for pregnancy
What is the main reproductive hormone for men?
Testosterone
Where is testosterone produced?
Testes
What does testosterone do?
Stimulates sperm production
What is the main reproductive hormone for women?
Oestrogen
What happens in Stage 1 of the menstrual cycle?
Day 1- menstruation starts where the uterus lining breaks down for about 4-6 days
What happens in 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 in Stage 3 of the menstrual cycle?
Ovulation- An egg develops and is released from the ovary at day 14
What happens in Stage 4 of the menstrual cycle?
The wall is then maintained from about day 14 to 28. If no fertilised egg has landed on the uterus wall by 28, the lining starts to break down and the cycle repeats
What 4 hormones control the menstrual cycle?
1) FSH (Follicle-stimulating hormone)
2) Oestrogen
3) LH (Luteinising hormone)
4) Progesterone
Which gland produces FSH?
Pituitary gland
Where is the target of FSH?
Ovary
What are the 2 actions of the target of FSH?
1) Causes an egg to mature
2) Starts releasing oestrogen
Which gland produces oestrogen?
Ovary
Where is the target of oestrogen?
Uterus
What are the 2 actions of target of oestrogen?
1) Thickens the uterus lining
2) Tells pituitary to inhibit FSH and secrete LH instead
Which gland produces LH?
Pituitary gland
Where is the target of LH?
Ovary
What are the 2 actions of target of LH?
1) Ovulation (Stimulates release of an egg)
2) Starts progesterone
Which gland produces progesterone?
Ovary
Where is the target of progesterone?
Uterus
What are the 2 actions of target of progesterone?
1) Maintains uterus lining (during 2nd half of cycle)
2) When oestrogen and progesterone levels drop, period starts and also tells the pituitary to start releasing FSH again
How can oestrogen actually prevent the release of an egg?
If oestrogen is taken daily to keep the level permanently high, it inhibits the production of FSH, and after a while, egg development production stop and stay stopped
How can progesterone reduce fertility?
By stimulating the production of thick mucus which prevents any sperm getting through to reach an egg
What is ‘The pill’?
An oral contraceptive containing oestrogen and progesterone
2 negative of taking the pill?
1) Can cause headaches and nausea
2) Doesn’t protect against STD’s
What is the contraceptive patch?
A small patch stuck to the skin containing oestrogen and progesterone. Each patch lasts a week
What is the contraceptive implant?
An implant inserted under the skin. Releases a continuous amount of progesterone to stop the ovaries releasing the egg, harder for sperm to swim , and stops any fertilised egg implanting in the uterus. Can last 3 years.
What is the contraceptive injection?
An injection containing progesterone lasting 2-3 months
What is an Intrauterine device (IUD)?
A T-Shaped device inserted into the uterus to kill sperm and prevent implantation of a fertilised egg.
What are the two main types of IUDs?
1) Plastic IUDs releasing progesterone
2) Copper IUDs preventing sperm surviving in uterus
4 examples of non-hormonal methods of contraception?
1) Condoms
2) Diaphragms
3) Copper IUDs
4) Spermicides
What is a diaphragm?
A shallow plastic cup that fits over the cervix to form a barrier. Has to be used with a spermicide.
What is the only form of contraception that prevents STDs
Condoms
What is sterilisation?
Cutting/tying fallopian tubes in a female, or the sperm duct in a male. This is a permanent procedure
What are natural methods of avoiding pregnancy?
Avoiding sexual intercourse when the women is most fertile in her menstrual cycle. Not very effective.
What is abstinence in avoiding pregnancy?
Not having intercourse
Why can’t some women get pregnant?
Their FSH levels are too low to cause their eggs to mature meaning no egg is released
What is the fertility drug?
A drug containing the hormones FSH and LH to stimulate ovulation
What does IVF stand for?
In Vitro Fertilisation
Explain the stages of IVF
1) Eggs collected from woman’s ovaries, fertilised in a lab with man’s sperm
2) Fertilised egg grown into embryos in lab incubator
3) Once embryos are tiny balls of cells, 1 or 2 are transferred to woman’s uterus
4) FSH and LH given before egg collection to stimulate several eggs to mature
3 negatives of IVF
1) Multiple births (higher risk of miscarriage, stllbirth)
2) Success rate is low
3) Physically stressful (vomiting, dehydration)
2 reasons why some are against IVF
1) Unused embryos are eventually destroyed
2) Genetic testing could lead to selecting preferred characteristics
Why and how is adrenaline released?
In response to stressful or scary situations- your brain detects stress and sends nervous impulses to the adrenal glands which then secrete adrenaline
What does adrenaline trigger?
‘Fight or flight’ mode, increases supply of oxygen and glucose to the brain and muscles
Why is thyroxine released?
To regulate basal metabolic rate and stimulating proteinsynthesis for growth and development
When the level of thyroxine in the blood is too high, what happens?
The secretion of the Thyroid Stimulating hormone (TSH) released from the pituitary gland is inhibited
What is the role of plant hormones?
They make sure that plants grow in the right direction
What is auxin?
A plant hormone that controls growth near the tips of the shoots and roots of a plant. It moves backwards to stimulate the cell elongation process which occurs in cells just behind the tips
What does auxin control the growth of a plant in response to?
1) Light (phototropism)
2) Gravity (gravitropism/geotropism)
What happens if the tip of a shoot in a plant is removed?
No auxin is available and the shoot may stop growing
What happens when a shoot tip is exposed to light/grows towards light?
1) More auxin accumulates on the side that’s in the shade than the side in the light
2) This makes the cells grow/ elongate faster on the shaded side so the shoot bends towards the light
What happens when a shoot grows away from gravity and roots grow towards gravity?
1) When a shoot grows sideways, gravity produces unequal distribution of auxin in the tip, with more auxin on the lower side
2) Causes lower side to grow faster, bending the shoot up
3) A root growing sideways will also have more auxin on its lower side
4) In a root, the extra auxin inhibits growth meaning cells on top elongate faster, so root bends downwards
3 uses of auxin
1) Killing weeds
2) Growing from cuttings with rooting powder
3) Growing cells in tissue culture
3 uses of Gibberellin
1) End seed dormancy
2) Promotes/induces flowering
3) Increases/ grows larger fruits
2 uses of Ethene
1) Influences the growth of plants by controlling cell division
2) Controls/speeds up the ripening of fruits
3 examples of plant growth hormones
1) Auxin
2) Gibberellin
3) Ethene
