Flashcards in Homeostasis and response Deck (75):
What is homeostasis?
The regulation of the conditions inside you body to maintain a stable internal environment, in response to changes in both internal and external conditions
What are the three main components that work together to maintain a steady condition?
Cells called receptors, coordination centers and effectors
What is stimuli?
A change in the environment which the body may need to respond to. his could be light, sound, touch, pressure, pain, chemical or temperature
What happens in the body when the levels of a stimulus are too high or low?
It is detected by the receptors, which then send the information to the coordination centre which organises a response. The effectors respond to counteract the change.
What is the mechanism that restores the optimum level called?
A negative feedback mechanism
What is the problem with the effectors and how is this solved?
They will keep on producing responses which can mean that they can change the level of stimuli too much, but this is detected by the receptors etc.
What does the nervous system do?
What allows you to react to your surroundings and coordinates your behaviour
How does the central nervous system send messages?
It is connected to the body by sensory and motor neurones, which electrical impulses can be transmitted on
How do muscles and glands respond to nervous impulses?
Muscles contract and glands secrete chemical substances called hormones
What are the three types of neurones?
Sensory, motor and relay
What are sensory neurones?
The neurones that carry information in electrical impulses from receptors to the central nervous system
What are relay neurones?
The neurones that send electrical impulses from sensory neurones to motor neurones. These are found in the central nervous system
What are motor neurones?
The neurones that carry electrical impulses from the central nervous system to the effectors
What is a synapse?
The connection between two neurones
How are nerve signals transferred across a synapse?
Chemicals which diffuse across the gap and then set off a new electrical impulse in the next neurone
What are reflexes?
Fast, automatic responses to certain stimuli; bypassed by the conscious brain when a quick response is necessary
What is the brain?
A part of the central nervous system, responsible for complex behaviours such as breathing and is made up of billions of interconnected neurones
What is the cerebral cortex responsible for?
Things like consciousness, intelligence, memory, and language; it is the outer, wrinkly bit
What is the medulla responsible for?
Controls unconscious activities such as breathing
What is cerebellum responsible for?
Muscle co-ordination (looks like a flower)
What are the three methods scientists use to study the brain and how?
Studying patients with brain damage to see the effect of the damaged part, electrically stimulating the brain by using electrodes to see how different parts react and MRI scans that can give a detailed picture of the brain
What is the sclera?
The tough, supporting wall of the eye
What is the cornea?
The transparent outer layer at the front of the eye which refracts light into the eye
What is the iris?
Contains muscles that controls pupil and how much light gets in
What is the lens?
Focuses the light onto the retina
What are the ciliary muscles and suspensory ligaments?
Control shape of lens
What is the optic nerve?
Carries impulses from the receptors of the retina to the brain
What is the iris reflex?
Light receptors detect bright light, so the circular muscles in the iris contract whilst the radial muscles relax, so less can get into the eye
How does the eye look at near objects?
Ciliary muscles contract, which slackens the suspensory ligaments, making the lens more curved and increases the amount of refracted light
How does the eye look at distant objects?
Ciliary muscles relax, which allows the suspensory ligaments to pull tight, making the lens thinner and refracting light less
What is the proper word for long-sightedness?
What is the proper word for short-sightedness?
How are people long-sighted?
Lens is the wrong shape so can't refract enough light, making the image of near-sighted objects focus behind the retina
How are people short-sighted?
Lens is the wrong shape so refracts light too much, bringing distant objects into focus in front of the retina
How can vision defects be fixed and?
Contact lenses which sit on the eye, laser eye surgery which changes the shape of the cornea by vaporising tissue and replacement lens surgery, where an artificial lens is inserted into the eye
What controls temperature in the brain?
The thermoregulatory centre
What happens when the body is too hot or cold?
Temperature receptors detect, thermoregulatory centre acts as a coordination centre and triggers effectors
What can the body do to cool down?
Glands produce sweat which evaporates and transfers energy to environment and blood vessels dilate so more blood gets closer to skin to transfer energy from skin to environment (vasodilation)
What can the body do to warm up?
Hair stands up as insulating layer, no sweat, blood vessels constrict (vasoconstriction) and shivering, which needs respiration and transfers energy to warm body
What is the endocrine system?
Various different glands which secrete hormones
What does the pituary gland do?
Produces hormones that regulate body temperature and trigger other hormones
What do the ovaries do?
Produce oestrogen for the menstrual cycle
What do the testes do?
Produce testosterone which controls puberty and sperm production
What does the thyroid do?
Produces thyroxine which regulates metabolism, heart rate and temperature
What does the adrenaline gland do?
What does the pancreas do?
Produces insulin to regulate glucose level
What are properties of nerves?
Fast action, short time, precise area
What are properties of hormones?
Slower action, long time, general way
How is the level of glucose int he blood kept steady?
Changes are monitored and controlled by the pancreas, using the hormones insulin and glucagon, in a negative feedback cycle
How can type 1 diabetes be helped?
Insulin therapy, regular exercise and limiting the intake of foods rich in simple carbohydrates
How can type 2 diabetes be helped?
Regular exercise and eating a carbohydrate controlled diet
What is the difference between type 1 and 2 diabetes?
Type 1 is where the body produces little to no insulin and type 2 is where a person becomes resistant to their own insulin
Why is urea removed from the body?
Proteins cannot be stored so are converted by deanimation and stored in the liver, amonia is a waste product which is toxic so is converted to urea which is filtered out.
Why are ions removed from the body?
if the ion or water content in the body is wrong, too much or too little water is drawn into the cells through osmosis which can damage cells, so the right amount of ions are reabsorbed then the rest are removed
Why is water removed from the body?
Water is lost in sweat and breathing, which can't be controlled so is balanced with consuming and removing some in the kidneys
How is the concentration of urine controlled?
Brain instructs pituary gland to release ADH (anti-diuretic hormone) according to how much is needed, which is controlled by negative feedback
How does kidney dialysis work?
Dialysis fluid has same conc of ions and glucose as healthy blood, which means only waste substances diffuse across partially-permeable barrier
What is the cure for kidney failure?
A kidney transplant, but it can be rejected by the immune system so the patient has to use drugs
What are the four stages of the menstrual cycle?
Uterus lining breaks down, uterus lining builds up again, an egg develops and is released and the wall is then maintained
What does FSH (follicle-stimulating hormone) do?
Causes egg to mature and triggers oestrogen production
What does oestrogen do?
Causes lining of uterus to grow and triggers release of LH
What does LH (luteinising hormone) do?
Stimulates release of an egg
What does progesterone do?
Maintains lining and inhibits release of LH and FSH
How can hormones be used to reduce fertility?
Oestrogen (prevents release of egg) and progesterone (reduces fertility) can be combined and used in a contraceptive pill
What are other methods of avoiding pregnancy?
Condoms, spermicide, sterilisation and abstinence
What are the cons of fertility drugs?
It doesn't always work and too many eggs can be stimulated
How does IVF work?
eggs are collected, sperm is added, grown in tubes, FSH and LF are added, then put back in woman
What are the cons of IVF?
Multiple births, low success rate, emotionally stressful and physically stressful
What does adrenaline do?
Increases supply of oxygen and glucose to cells in the brain and muscles
What is auxin?
A plant hormone that controls growth near the tips of shoots and roots
How does auxin affect when shoots grow towards light?
More auxin accumulates on the side that is in the shade, which makes it elongate on the shaded side, so the root bends towards the light
How does auxin affect when shoots grow away from gravity?
Gravity produces an unequal distribution of auxin on the tip, with more auxin on the lower side, causing the root to grow bending upwards
How does auxin affect when roots grow towards gravity?
It will have more auxin on it's lower side, so the growth is inhibited and the cells on top elongate faster, so that the root bends downwards
What are some of the uses of auxin?
Killing weeds by disrupting growth patterns, growing cuttings from rooting powders as it produces roots rapidly into a new plant and growing cells in tissue culture by stimulating cells to divide