Topic 5 Homeostasis And Response Flashcards
Homeostasis
Maintaining a stable internal environment
What three thins make up the automatic control system?
Receptors, coordination centres and effectors
What is the CNS (central nervous system)?
In vertebrates this is the brain and spinal cord and connected with sensory neurones and motor neurones
What are sensory neurones?
They carry electrical impulses from the receptors to the CNS
What are motor neurones?
They carry electrical impulses from the CNS to the effectors
What are effectors?
The muscles and glands which respond to nervous impulses eg muscle contraction
What are receptors?
Cells that detect stimuli. Taste, sound, light, pain.
The order of the CNS(central nervous system) to coordinate a response
Stimulus, receptor, sensory neurones, CNS, motor neurone, effector, response
What is a synapses?
Connection between two neurones nerve signals are transferred through diffusion then set of a new electrical signal in the next neurone
Reflexes
Automatic responses to prevent injury. Eg pupils get smaller if there is a bright light or getting a shock Adrenaline is released this Is a relflex arc
A reflex arc through the CNS
- Touch something hot
- Pain receptors stimulates pain
- Impulses Tavel along the sensory neurone
- Impulses pass on the relay neurone and across a synapse
- Impulses travel on a motor neurone
- Impulses reaches effected muscle contracts away
Cerebral cortex
Outer wrinkly bit responsible for consciousness, intelligence, memory and language
Medulla
Controls unconscious activities eg heartbeat and breathing
Cerebellum
Responsible for muscle coordination
Studying patients with brain damage
If a small part is damaged the effect it has on the person shows what the brain does
Electronically stimulating the brain
Pushing a tiny electrode into the tissue and stimulating different parts to get an idea of what the parts do
MRI (magnetic resonance scanner) scans
The scanner creates a detailed picture of the brains structure so can find out what areas are active when recalling a memory of listening to music
The consequences of messing with the brain
Has lead to helping Parkinson’s by reducing muscle tremors. However the brain is delicate and investigation of brain function is difficult and can cause physical damage or problems with brain function
Sclera
Tough supporting wall of the eye
Cornea
Transparent outer layer at the front of the eye and refracts light into the eye
Iris
Muscles that control the diameter of the pupil therefore the amount of light
Lens
Focuses the light onto the retina (which has receptor cells sensitive to intensity and colour)
The shape of the lens
Controlled by collard muscles and suspending ligaments
Optic nerve
Carries impulses from the receptors on the retina to the brain
Iris reflex bright light
If a light receptor detects bright light a reflex in the pupil makes it smaller. The circular muscles contract and the radial muscles relax and reduces the amazing of light
Iris reflex low light
In low light the radial muscles contract and circular muscles relax and makes the pupil wider
Looking at near objects
The ciliary muscles contract which slackens the suspensory ligaments. The lens becomes fat (more curves). And increase the amount of light refracted
Looking at distant objects
The ciliary muscles relax allowing the dispensary ligaments to pull tight. The lens becomes thinner(less curved). So refracts less light
Long sighted people (hyperopia)
Unable to focus on near objects. Happens when the lens is the wrong shape and doesn’t refract enough light. The images of the near objects focus behind the retina. A convex lens can correct it so it reflects the light rays so they focus on the retina
Short sighted people (myopia)
Unable to focus on distant objects. Happens when lens is the wrong shape and refracts to much or the eyeball is too long. Distant objects are brought into focus in front of the retina. A concave lens can solve this by getting the image to focus at the retina
Contact lenses
Thin lenses that sit on the eye that compensate for the fault in focusing. They are lightweight and invisible. More continent then glasses for sport. Two types of contact lenses soft ones are more comfortable but a higher chance of infection compared to hard ones
Laser eye surgery
Vaporises tissue changing the shape of the cornea. Slimming it makes less powerful and improves short sight. Changing the shape to be more powerful improves long sightedness. Can be complications like infections
Replacement lens surgery
The natural lens is removed and an artificial lens made of plastic is inserted. Has higher risks then laser eye surgery to the retina
The optimum temperature for enzymes in the body
37 degrees
What are the responses when the body is too cold?
Hairs stand up to provide an insulating later.
No sweat is produced.
Blood vessels close to the skin constrict called vasoconstriction.
Shivering to generate heat
What are the responses to being too hot?
hair lies flat.
Sweat is produced and evaporates transferring energy to ten environment.
Blood vessels supping the skin dilate so more flows near the surface this is Called Vasodilation
Hormones
Chemical messengers sent in the blood
Endocrine system
Endocrine glands produce and secret hormones and they make up the endocrine system
Pituitary gland
Produces many hormones that regulate body conditions. Sometimes called the master gland as the hormones act on each other
Ovaries
Produces oestrogen which is involved in the menstrual cycle
Testes
Produce testosterone which controls puberty and sperm production in males
Thyroid
Produces thyroxine which regulates rate of metabolism, heart rate and temperature
Adrenal Gland
This produces adrenaline which controls the fight or flight response
The Pancreas
Produces insulin which regulates the blood glucose level
Nerves
Very fast action.
Acts for a very short time.
Act on a precise area
Hormones
Slower action.
Act for a long time.
Act in a more general way
What do kidneys do?
Remove waste substances and control the level of ions and water
Why are Dialysis machines used?
To keep the contractions of dissolve substances in the blood at normal levels and remove waste
How Dialysis machines work?
The blood flows between partially permeable membranes surrounded by dialysis fluid. The concentration of ions and glucose is the same in the blood and fluid. So only waste produces like urea and excess water and ions will diffuse.
How often is dialysis needed?
Three times a week and it lasts from 3-4 hours
kidney transplants
Only cure for kidney failure. Has to be from someone who has a donor card. Can be transplanted from live donors. Risk the kidney is rejected. Transplants are cheaper then Dialysis
What controls blood glucose levels
Insulin and Glucagon
What is added if blood glucose levels are too high?
Insulin
What happens if blood glucose levels are too low?
Glucagon is added
Insulin and Glucagon
Carbohydrates put glucose into the blood. Metabolism removes glucose from the blood. Exercise removes glucose from the blood. Excess glucose is stored as glycogen in the liver and the muscles.
Type 1 diabetes
When the Pancreas produces no or little insulin. So they need injections throughout the day. People need to eat less carbohydrates and regular exercise. The amount of insulin needed depends on the diet and how active they are
Type 2 diabetes
When a person becomes resistant to their insulin. Causing the blood level to rise to high levels. Being overweight increases the chance of developing it. Can be controlled by having a carbohydrate-controlled diet and getting regular exercise
Filtering Urea
Protein can’t be stored in the body so is converted into fat and carbohydrates and occurs in the liver and is Calle deamination. Ammonia is produced as a waste product. Ammonia is toxic so is converted into urea then goes to the kidney where it is filtered and excreted as urine
Filtering ions
Ions is taken in by food. If the ion content is wrong it can damage the cells or mean they don’t work as well. Some ions are lost through sweat but this isn’t regulated so it is maintained by the kidneys as they reabsorb the right amount and filter the rest though urine
Filtering water
The body has a balance of water coming in against water coming out. Water is lost through sweat and from lungs when breathing. These can’t be controlled so the kidney controls how much is removed by the kidneys in urine
Concentration or urine
Controlled by ADH (anti-diuretic hormone) after being released into the bloodstream from the pituitary gland. The brain monitors the content of the blood. Controlled by negative feedback so if the content gets too high or low it will react to take it back to normal
The 4 stages of the menstrual cycle
- Day 1 the uterus lining breaks down for about four days
- From day 4 to day 14 uterus lining builds up again and into a thick spongy layer of blood vessels ready to receive a fertilised egg
- An egg develops and is released from the ovary at day 14 Called ovulation
- The wall is maintained from day 14-18 if there is no fertilised egg by day 28 the lining starts to break down
FSH (Follicle-Stimulating Hormone)
Produced in the pituitary gland. Causes an egg to mature in one of the ovaries in a 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 realist of FSH
LH (Luteinising Hormone)
Produced by the pituitary gland. Stimulates the release of an egg at day 14
Progesterone
Produced in the ovaries by the remains of the follicle after ovulation.maintains the lining of the uterus in the second half of the cycle when the level of progesterone falls the lining breaks down. Inhibits the release of LH and FSH
Hormones used to increase fertility
Some women have to low levels of FSH for the eggs to mature. FSH and LH are given to women to stimulate ovulation. It doesn’t always work and can be expensive. Too many eggs can be simulated resulting twins triplets etc
IVF (in vitro fertilisation)
Collects eggs from the women’s ovaries and fertilise them in a lab. The fertilised eggs are then grown into embryos in a lab. Once they are a bundle of cells one or two are transferred to the women’s uterus. FSH and LH are given before egg collection to stimulate eggs to mature
Pros and cons of IVF ( in vitro fertilisation)
Can give infertile couples a child. However multiple births could happen and are riskier for the mother or child. Success rate is low 26% so can be stressful. Can be physically stressful due to violent reactions to hormones eg abdominal pain, vomiting, dehydration
ICSI (intra-cytoplasmic sperm injection)
Where the sperm is injected directly to the egg and useful for men with low sperm counts
Why are people against IVF?
IVF can lead to unused embryos which are unethical to some. Genetic testing of embryos before implantation raise ethical issues as the selection of preferred characteristics such as gender or eye colour
Adrenaline
Released by the adrenal gland and is released by stressful or scary situations and the brain sends electrical impulses to the adrenal gland. It triggers the fight or flight reaction by increasing oxygen and glucose to cells in the brains and muscles
Thyroxine
Realised by the thyroid gland in the neck. It regulates the metabolic rate. Important for protein synthesis, growth and development. Thyroxine is released in response to TSH.
Auxin
A plant hormone which controls the growth near the tips of shoots and roots.
Uses of Auxin (killing weeds)
Weeds are normally broad leaved however grasses and cereals are narrow leaved. Selective weedkillers have been developed to only affect broad leaved plants and disrupt their growth and cause them to die but not affecting the crops
Uses of Auxins (growing from cuttings with rooting powder)
If a cutting is put in the ground and rooting powder is included the plant grows roots rapidly. This enables the plant to produce copies of itself so can reproduce quickly
Uses of Auxin (growing cells in tissue culture)
Used to grow clones to do this auxin is added to the growth medium to stimulate the cells to divide to form roots and shoots
Uses of Gibberellin (controlling dormancy)
Lots of seeds won’t germinate without certain conditions. Seeds can be treated with gibberellin to alter dormancy and make the seeds germinate at certain times of the year
Uses of Gibberellin (inducing flowering)
Some plants require certain conditions to flower. Such as longer days or low temperatures. So they can flower without a change in environment and can grow bigger flowers
Uses of Gibberellin (growing larger fruits)
Seedless fruit don’t grow as well as seeded fruit. If Gibberellin is added to these fruit they grow larger then normal types
Uses of Ethene (ripening fruit)
A gas produced by aging parts of a plant. Controls cell division. Stimulates enzymes the cause fruit to ripen. Fruit can be picked unripe and be ripened before sale. Ripening can be delayed by adding chemicals to block ethenes effects
Condoms
Worn over the penis stops sperm making to the vagina. Only form of contraception that protects against STDs
Diaphragm
Shallow plastic cup that fits in the cervix to form a barrier and is coated in spermicide to kill sperm
Spermicide
Can be used as contraception on its own but only 70-80% effective
Sterilisation
Cutting or tying the Fallopian tubes in a female or the sperm duct in a male. Is permanent however there is a small chance they can rejoin
Natural methods
By finding when the women is most fertile and avoid sex however not very effective
Abstinence
Only way to ensure there is no pregnancy is to not have sex
Oestrogen used as contraception
Inhibits FSH so after a while egg development and production stop
Progesterone as a contraceptive
Stimulates the production of thick mucus which prevents sperm reaching the egg
The pill as a contraceptive
Oral contraceptive containing oestrogen and progesterone. 99% effective but can have side effects like headache and nausea and doesn’t protect against STDs
Progesterone only pill as a contraceptive
Just as effective as the pill but has less side effects
Contraceptive patch
5 by 5 cm patch that is stuck to the skin that contains oestrogen and progesterone and lasts for one week
Contraceptive implant
Inserted under the skin and releases a constant supply of progesterone which stops the ovaries releasing eggs so the sperm struggle to swim to the egg. Stops fertilised eggs implanting in the uterus and can lest for three years
IUD (intrauterine device)
A T-shaped device inserted into the uterus to kill sperm and prevent implantation. Two types- plastic that release progesterone or copper that prevent the sperm surviving in the uterus
Shoots growing towards lights with Auxin (phototropism)
If a shoot tip is exposed to light more Auxin accumulates in the side that is in shade. So the shoot grows faster on the shaded side so the shoot bends towards the light
Shoots growing away from gravity (gravitropism)
When a shoot grows sideways gravity creates an unequal distribution of Auxin at the tip. More Auxin at the lower side causing it to grow faster and bending the shoot upwards
Roots growing towards gravity (gravitropism)
In a root there will be more Auxin on the lower side but in a root the extra Auxin inhibits growth so the cells on top grow faster and roots Ben downwards
