HOMEOSTASIS AND RESPONSE Flashcards
What is homeostasis?
The maintenance of a constant internal environment despite changes in the surroundings
What does homeostasis involve regulating in the body?
Blood glucose concentration
Water levels
Body temperature
What is a stimuli?
A change in the environment/surroundings
What are receptors?
Detects something (e.g. retina in eye which detects intensity and colour of light)
What are effectors?
Muscles or glands which carry out responses (muscles contract and glands secrete hormones)
What is the central nervous system (CNS) make up of?
Brain and spinal cord
What does the CNS do?
Collects all sensory information Processes/coordinates it
Responds by communicating with effectors
What is conducted on neurones?
Electrical impulses
What is the order of the nervous systems normal reaction?
Stimulus
Sensory receptor
Sensory neurone
CNS
Motor neurone
Effectors
Where does the sensory neurone carry its electrical impulse?
From sensory receptor to CNS
Where does the motor neurone carry its electrical impulse?
From CNS to effectors
What is a synapse?
The gap between the end of one neurone and the start of the next neurone
What happens at synapses?
Electrical pulses cannot be conducted (no conducting tissue) so chemical neurotransmitters diffuse across the synapse
What are reflex actions?
Automatic and rapid actions that do not involve the conscious part of the brain
What does a relay neurone do?
Connects the sensory and motor neurone (no brain)
What is the order of the nervous systems reflex reaction?
Stimulus
Sensory receptor
Sensory neurone
Relay neurone
Motor neurone
Effectors
What does the cerebrum in the brain do?
Controls voluntary movements, learning, memory and personality
What are the 2 hemispheres of the cerebrum (in brain) connected by?
Corpus callosum
What does the medulla in the brain do?
Controls involuntary muscles and automatic reactions
What is a stroke?
When the blood supply to the brain is cut off
How does an MRI (magnetic resonance imaging) work?
Uses radio waves and strong magnetic fields to generate images of the brain
What does the retina in the eye do?
Structure at the back of the eye
Contains receptors that are sensitive to light and colour
What does the cornea in the eye do?
The transparent front part of the eye
Protects the eye
Refracts the light rays entering the eye
What does the sclera in the eye do?
Tough, fibrous layer
Forms the supporting wall of the eyeball
What does the optic nerve do in the eye?
Conducts impulses from the eye to the brain
What is accommodation in the eye?
Allows the eye to focus light in a sharp image
The lens has to change shape to accommodate the difference (close and far objects)
What happens to the pupil in dim light?
Radial muscles contract
Circular muscles relax
Pupil is pulled bigger so dilates
Therefore more light can enter
What happens to the pupil in bright light?
Circular muscles contract
Radial muscles relax
Pupil constricts
Reduces amount of light entering eye to prevent damage to sensitve receptor cells in retina
What does the CNS act as?
A coordination centre (receives information from receptors and coordinates a response)
What do the ciliary muscles and suspensory ligaments do?
They control the shape of the lens
What happens to the eye when it looks at near/close objects?
Ciliary muscles contract
Suspensory ligaments relax
Lens becomes fat (more curved)
Increases the amount by which it refracts light
What happens to the eye when it looks at far/distant objects?
Ciliary muscles relax
Suspensory ligaments contract
Makes the lens go thin (less curved)
Refracts light by a smaller amount
Why are some people long-sighted?
They are unable to focus on close objects because the lens is the wrong shape and doesn’t refract the light enough or the eyeball is too short
What is long-sightedness called?
Hyperopia
Why are some people short-sighted?
They are unable to focus on distant objects because the lens is the wrong shape and refracts the light too much or the eyeball is too long
What is short-sightedness called?
Myopia
What are contact lenses?
Thin lenses that sit on the surface of the eye and are shaped to compensate for the fault in focusing
Light and almost invisible
More convenient for sport
Hard and soft lenses (soft more dangerous)
What is laser eye surgery?
Laser can be used to vaporise tissue, changing the shape of the cornea
Slimming it down to make it less powerful improves short sight
Changing the shape to make it more powerful improves long site
What is replacement lens surgery?
Replacing the natural lens of the eye with an artificial lens (clear plastic)
What are hormones?
Chemical molecules released directly into the blood and affect target organs
What hormones do the ovaries produce?
Oestrogen
Progesterone
What hormone does the testes produce?
Testosterone
What is the pituitary gland?
The master gland because these hormones act on other glands directing them to release hormones
What hormone does the thyroid produce?
Thyroxine
What does thyroxine do?
Regulates rate of metabolism, heart rate and temperature
What hormone does the adrenal gland produce?
Adrenaline
What hormones do the pancreas produce?
Insulin
Glucagon
Where are hormones produce?
Endocrine glands
What are the endocrine glands?
Pituitary gland
Thyroid
Adrenal gland
Pancreas
Ovaries
Testes
How are nerves different from hormones?
Faster
Act for a short time
Act on a very precise area
How are hormones different from nerves?
Slower
Act for a long time
Act in a more general way
What is the hormonal system?
Contains glands that secret hormones directly into the blood
What hormones do the pituitary gland produce?
FSH
TSH
LH
What is progesterone?
During ovulation
Ovum follicle left behind when egg pops out produces the hormone
What is THS?
Thyroid stimulating hormone
What is FSH?
Follicle stimulating hormone
What is LH?
Luteinising hormone (causes ovulation)
What target organ does adrenaline go to?
The heart muscle
What target organ does insulin and glucagon go to?
The liver
What target organ does FSH go to?
Ovary
What target organ does TSH go to?
Thyroid gland
What target organ does LH go to?
Ovary
What does insulin do?
Joins glucose monomers you form glycogen
What does glucagon do?
Breaks down glycogen into glucose monomers
What is adrenaline?
The fight or flight hormone
What does adrenaline do?
Increases heart and breathing rate
Increase rate of respiration
Redistributes blood to areas where it is most needed
What happens to glucose when it enters our body?
Removed from blood by metabolism of cells or exercise
What happens to excess glucose?
Stored as glycogen in the liver and muscles
What happens if blood glucose level is too high?
Insulin is secreted from pancreas
Insulin makes liver turn it into glycogen
Therefore glucose removed from blood
What happens if blood glucose level is too low?
Glucagon is secreted from pancreas
Glucagon makes liver turn glycogen into glucose
Glucose released into blood
What is Type 1 diabetes?
When the pancreas produces little or no insulin so glucose levels are high
What is insulin therapy?
Type 1 diabetes
Several injections of insulin throughout the day which removed glucose from blood after food has been digested
What is Type 2 diabetes?
Where a person becomes resistant to their own insulin (body cells don’t respond to hormone properly)
Causes blood sugar level to rise to a dangerous level
What does the thermoregulation centre do?
Balances amount of energy gained and lots to keep the core body temperature constant
How does thermoregulation system work?
In brain receptors are sensitive to the temperature of the blood flowing through brain
Received impulses from temperature receptors in the skin
What happens when temperature receptors detect that the core body temp is too high?
Receives information from receptors
Triggers effectors e.g. sweat glands
What happens when temperature receptors detect that the core body temp is too low?
Received information from receptors
Triggers effectors e.g. muscles
What happens when your too hot (sweat)?
Sweat is produced by sweat glands and evaporates from skin to transfers energy to the environment
Vasodilation occurs so more blood can flow close to the surface of skin to help transfer energy
What happens when your too cold (hairs)?
Hairs stand up on end to trap an insulating layer of air
No sweat produced
Vasoconstriction occurs to reduce energy transfer
What happens when your too cold (shiver)?
Body shivers (muscles contract)
This needs respiration so energy is transferred to warm body
What does thyroxine target?
All cells
What happens when adrenaline is secreted into the blood?
Increased oxygen and glucose delivery to muscles and brain via vasodilation
Decreased oxygen and glucose delivery to kidneys and digestive system via vasoconstriction
Why does breathing rate increase when adrenaline is secreted into the blood?
Increased demand for oxygen so increased heart rate to pump blood around the body so glucose and oxygen go to cells
Cells carry out respiration
Energy is released causing muscle movement
What does the thyroid need to produce thyroxine?
Idione and TSH
What does thyroxine do?
Increases basal metabolic rate
What is your basal metabolic rate?
How quickly energy is transferred from stores and becomes available for use by cells
How is thyroxine released?
Not enough energy for cells
Receptors in hypothalamus detect this
Pituitary gland releases TSH
TSH binds to thyroid gland and released thyroxine
Thyroxine causes metabolic rate to increase causing cells to transfer additional energy
Cells now have enough energy
What is the negative feedback loop?
Conditions change
Effectors
Condition return
Effectors switch off
REPEAT
What does the cerebellum control?
Balance
Posture
Fine movements
What is tropism (plants)?
Growth in response to stimulus
What is phototropism?
Response to light
What is geotropism?
Response to gravity
What is hydrotropism?
Response to water
What is auxin?
A plant growth hormone (produced on shaded side of plant)
What are roots sensitive to?
Negatively sensitive to light (moves away)
Positively sensitive to gravity (grows with gravity)
What are shoots sensitive to?
Positively sensitive to light (moves towards)
Negatively sensitive to gravity (grows away)
What does ethene do in plants?
Controls cell division and ripening of fruits
What do gibberellins do?
Promote flowering throughout dormancy
Ends seed dormancy
Increases fruit size
What is auxine used for?
Promote growth in tissue culture
Making root powders
Weed killers
What 3 ways do you lose water?
Sweating
Urinating
Breathing (water vapour)
What is deamination?
Removing amino group from amino acids in liver
What happens to amino acids in the liver?
Deamination occurs producing ammonia (toxic)
Converted into urea
Urea goes into blood into kidneys which is filtered out and excreted as urine
What happens to proteins in the body?
Proteins broken down by protease to produce amino acids
Amino acids broken down into ammonia in liver due to deamination
Ammonia broken into urea then sent to kidneys
What happens when we eat carbohydrates?
Glucose is put into the blood
How can glucose be removed from the blood?
By the normal metabolism of cells
Vigorous exercise
How can excess glucose be stored?
As glycogen in the liver and muscles
What monitors and controls the level of glucose in the blood?
The pancreas
How do the kidneys make urine?
By taking waste products out of your blood
What is filtration in the kidneys?
Substances are filtered out of the blood as they are passed through the kidneys
What useful substances are absorbed back into the blood when passed through the kidneys?
Glucose
Some ions
Right amount of water
What is selective reabsorption (kidneys)?
When useful substances are absorbed back into the blood when passed through the kidneys
What happens if the ion content of the body is wrong?
Could upset balance between ions and water meaning wrong amount of water is drawn into cells by osmosis
Can damage cells and cause them not to work
What happens when you lose ions through sweating?
Right amount of ions is reabsorbed into the blood after filtration in the kidneys (and the rest is made into urine
How do we balance the amount of water in our body?
Amount we consume
Amount removed by kidneys in the urine
What hormone controls the concentration of urine?
Anti-diuretic hormone (ADH)
What releases anti-diuretic hormone?
The pituitary gland
What happens when water level is too high?
Pituitary gland releases less ADH so less water is reabsorbed from the kidney tubules
What happens if your kidneys don’t work properly?
Waste substances build up in the blood
You lose your ability to control the levels of ions and water in your body
What does a kidney dialysis machine do?
Keeps the concentrations of dissolved substances in the blood at normal levels and removes waste substances
How does a kidney dialysis machine work?
Person’s blood flows through a partially permeable membrane surrounded by dialysis fluid
Dialysis fluid has same concentration of dissolved ions and glucose as healthy blood so useful ions and glucose won’t be lost
Waste substances and excess ions/water diffuse across membrane to lower concentration
What are the disadvantages of a kidney dialysis machine?
Patients have to go 3 times a week for 3-4 hours
May cause blood clots or infections
Expensive for NHS
What are the risks of kidney transplants?
Risk to person who is donating it
Risk that the donor kidney can be rejected by the patients immune system
What are the advantages of kidney transplants?
Cheaper
Last longer
What are the disadvantages of kidney transplants?
Long waiting list
Risk of infection
Risk of rejection
What are the advantages of kidney dialysis?
Buys patients with kidney failure time until a donor organ is found
What does thyroxine do?
Regulating the basal metabolic rate
Important for processes in the body e.g. protein synthesis for growth/development
Why do shoots grow towards light?
More auxin accumulates on side that is shaded
This makes cells on that side grow faster so the shoot bends towards the light
Why do shoots grow away from gravity?
Shoot growing sideways auxin accumulates on the lower side
Causes the cells to grow faster so the shoot bends upwards
Why do roots grow towards gravity?
More auxin on lower side
Extra auxin inhibits growth so root bends downwards
How does auxin kill weeds?
Disrupts normal growth patterns which kills the weeds
Has been developed to be selective so only affects broad-leaved plants and not grass/crops
How can auxin be used as a rooting powder for cuttings?
Put on cuttings and into soil
Causes roots to produce rapidly and a new plant starts growing
How can auxin be used to grow cells in tissue culture?
Auxin is added to the growth medium to stimulate cells to divide to form roots and shoots
What is tissue culture?
Used to grow clones of a plant from a few of its cells
What do gibberellins do (hormone)?
Stimulates seed germination, stem growth and flowering
What can gibberellins be used for?
Controlling dormancy (allow seeds to germinate all year round)
Inducing flowering uses plants to flower without changing environment)
Growing larger fruit
What is ethene?
A gas produced by aging parts of a plant
What does ethene do to a plant?
Influences the growth of the plant by controlling cell division
Stimulates enzymes which cause fruit to ripen
How can ripening be delayed in fruit?
Adding chemicals that block ethene’s effect to fruit
Reduce amount of ethene a fruit can produce
What happens during days 1-7 of the menstrual cycle?
Menstruation
What happens during days 8-11 of the menstrual cycle?
Lining of the womb thickens in preparation for egg
What happens during day 14 of the menstrual cycle?
Ovulation
What happens during days 18-25 of the menstrual cycle?
Corpus luteum fades away
What happens during days 26-28 of the menstrual cycle?
Uterine lining detaches leading to menstruation
What is the first stage of the menstrual cycle?
The egg starts to mature inside the follicle
What is a follicle?
A fluid filled ball
What is the second stage of the menstrual cycle?
Ovulation occurs where the follicle bursts releasing mature egg into the oviduct
What is the third stage of the menstrual cycle?
Empty follicle forms corpus luteum (yellow body)
What is the forth stage of the menstrual cycle?
Corpus luteum breaks down into corpus albicans
What does FSH do?
Causes a follicle to develop in the ovary which triggers ovary to release oestrogen
What does oestrogen do?
Stimulates the lining of the uterus to thicken
What is oestrogen made from?
The developing follicle
What does progesterone do?
Stops the lining of the uterus from being broken down
What does LH do?
Causes ovulation
What is ovulation?
The release of the ovum from the ovary
What happens to body temperature during ovulation?
It increasing (roughly from 36 to 37)
When is oestrogen released?
During ovulation
When is progesterone released?
When the follicle develops into the corpus luteum
When is LH released?
During ovulation
When is FSH released?
When the follicle is made
What does the combined pill do?
Releases hormones which inhibit FSH production so no eggs mature
What does a progesterone patch do?
Slowly releases progesterone to inhibit maturation/release of an egg
What does a IUD do?
Coil inserted into the uterus which releases copper which prevents sperm from surviving and implantation of a fertilised egg
What does a condom do?
Prevents the sperm from entering the vagina
What does a diaphragm do?
Prevents the sperm from entering the uterus
What is fertilisation?
Fusion of sperm with an ovum
What is implantation?
When a fertilised ovum embeds into the lining of the uterus
What is sterilisation?
Medical methods of birth control which leaves the person unable to reproduce
What is sterilisation for women called?
Tubal ligation
