5-Homeostasis and response (2) Flashcards
What is the role of the cereba cortex?
Controls intelligence, consciousness, memory and language.
What is the role of the cerebellum?
Controls muscular activity and balance.
What is the role of the medulla?
Controls unconscious activity e.g such as heart beat, breathing, digestion.
What is the role of the Lens?
Focuses the light rays by refraction onto the retina.
What is the role of the Cornea?
Protects the front of the eye and helps to focus the light.
What is the role of the Iris?
Made of muscle that can increase or decrease pupil size.
What is the role of the Pupil?
Gap between iris that allows light to reach the retina.
What is the role of the Retina?
Contains light-sensitive cells that receive an image and pass it to the brain.
What is the role of the Suspensory ligaments?
Hold the lens in position.
What is the role of the Ciliary muscles?
Contract to stretch the lens and relax to make the lens rounder.
What is the role of the Sclera?
Tough outer coating of the eye.
What is Myopia?
*Short-sightedness
*Caused by lens too round or long eyeball
*treated by concave lens glasses
What is hyperopia?
*Long-sightedness
*Cause by lens to flat or eyeball too short
*Fixed by convex lens glasses
How do the eyes adjust to bright light?
*Circular muscles contract
*Radial muscles relax
*Pupil constricts
How do eyes adjust to dim light?
*Circular muscles relax
*Radial muscles contract
*Pupil dilates
How do the eyes focus on near objects?
*Ciliary muscles contract
*Suspensory ligaments loosen
*Lens is then thicker and refract
*Light rays strongly
How do the eyes focus on distant objects?
*Ciliiary muscles relax
*Suspensory ligaments pulled tight
*Lens pulled thin and only slightly refracts light
How are lenses when they are relaxed?
*Lens spring, unless pulled will be fat
*Fat lenses refract more light
Describe the reflex arc?
Stimulus–> Receptor –> Coordinator –> Effector–> Response
What is the reflex arc?
Transmission of a nerve impulse from a receptor to the central nervous system and effector, to bring about a response to a stimulus.
How do scientists use patients with brain damage to study the brain?
*Study patients with brain damage-you can tell what area is damaged by the affect it has.
How do scientists use electronic stimulation of the brain to study it.
Pushing a tiny electrode into the tissue and giving it a small zap of electricity and observing the effects of different areas being stimulated.
How do scientists use MRI scans to study the brain?
It produces a very detailed picture of the brain’s structure to find out what areas are active during certain activities.
What are the problems with studying the brain?
*Incredibly complex and delicate
*Risks physical damage to the brain or problems with brain fuction.
How is body temperature controlled when body is too hot?
*Temperature receptors detects that the body is too hot
*Thermoregulatory centre acts as coordination centre, receiving information from the temperature receptors and triggers effectors automatically
*Effectors produce a response to counteract change
How is body temperature controlled when the body is too cold?
*Temperature receptors detect temperatures are too low
*Thermoregulatory centre acts as a coordination centre, receiving information from temp receptors and triggers effectors automatically
*Effectors produce a response and counteract change
How does the body cool itself down?
*Sweat produced by sweat glands and evaporates from skin, transferring energy to the environment
*Blood vessels supplying the skin dilate so more blood flows close to the surface to transfer energy from skin to environment (vasodilation)
*Hairs lie flat to allow heat to transfer to surroundings
How does the body warm itself up?
*No sweat produced
*Blood vessels constrict to prevent transfer of heat to the surroundings (vasocontriction)
*Hairs erect to trap an insulating layer of air
*Shiver to produce thermal energy from respiration of muscles
What is the endocrine system?
Sending chemical messengers known as hormones around the body via the bloodstream
What is the role of the pituitary gland?
- Produces many hormones that regulate body conditions
- sometimes called the ‘master gland’
- stimulates other glands
What is the role of the thyroid gland?
- Produced thyroxine
- regulating rate of metabolism, heart rate and temperature
What is the role of the adrenal gland?
- produces adrenaline
- prepares for ‘fight or flight’ responses
What is the role of the pancreas?
- produces insulin
- used to regulate blood glucose levels
What is the role of the ovaries?
- produce oestrogen
- involved in menstrual cycle
What is the role of the testes?
- produces testosterone
- controls puberty and sperm production
What is the difference between hormones and nerves?
- nerves very fast - hormones much slower
- nerves act for short tie - hormones act for long time
- nerves act on a very precise area - hormones act in a more general way
- nerves are electrical impulses - hormones diffuse through blood
How does the body respond when blood glucose is too high?
- insulin secreted by pancreas
- glucose moves from blood into liver and muscle cells
- insulin makes liver turn glucose into glycogen
How does the body respond when blood glucose is too low?
- glucagon secreted by pancreas
- but glucagon as well
- glucose released into blood by liver
- glucagon makes liver turn glycogen into gluucose
How are water levels maintained in the body?
- Water leaves body via lungs during exhalation
- water, ions and urea are lost from the skin in sweat
- no control over loss by the skins or lungs
- excess water, ions and urea removed via kidneys in the urine
How the kidney’s remove urea?
- proteins and amino acids can’t be stored by the body so any excess amino acids are converted into fats and carbohydrates in the liver, which can be stored
- ammonia produced as a waste product
- ammonia is toxic so converted to urea in the liver
- urea transported to kidneys where filtered out of blood and excreted as urine
How do the kidney’s remove ions?
- ions such as sodium taken in by food and absorbed into blood
- if ion content wrong, could upset balance between ions and water, meaning more or less water drawn in or out of the cell by osmosis
- some ions lost in sweat which is not regulated so balanced must be maintained by the kidneys
Why is kidney failure so dangerous?
Kidneys remove waste substances, waste substances build up and lose ability to control water and ion levels
How does dialysis work?
- blood flows between partially permeable membrane surrounded by dialysis fluid
- dialysis fluid contains same concentration of dissolved ions and glucose as healthy blood so no ions or glucose lost
- only waste substances such as urea and excess ions and water diffuse across
What are the disadvantages of dialysis?
- need sessions 3 times a week
- each session takes 3-4 hours
- may cause blood clots or infections
- more expensive in the long run
How do kidney transplants work?
- healthy kidneys usually transplanted from someone who has died suddenly
- kidneys can also be transplanted from people still alive
What are the disadvantages of kidney transplants?
- can be rejected by immune system
- need to take immunosuppressants to minimise risk of rejection which can cause other illnesses
- long wait
- risk to person donating
What is stage 1 of the menstrual cycle?
- menstruation starts and uterus lining breaks down for about 4 days
What is stage 2 of the menstrual cycle?
Uterus lining builds up again - from day 4 to 14 into thick spoungy layer of blood vessels to prepare for egg
What is stage 3 of the menstrual cycle?
An egg develops and is released from ovary at day 14 - ovulation
What is stage 4 of the menstrual cycle?
Wall is maintained for about 14 days until day 28 - if no fertilised egg received lining breaks down
What are the 4 hormones involved in the menstrual cycle?
- FSH
- Oestrogen
- LH
- Progesterone
What is the role of FSH in the menstrual cycle?
- produced in pituitary gland
- causes egg to mature in one of the ovaries as a follicle
- stimulates ovaries to produce oestrogen
What is the role of Oestrogen in the menstrual cycle?
- produced in the ovaries
- causes lining of the uterus to grow
- stimulates the release of LH (which causes egg release) and inhibits release of FSH
What is the role of LH in the menstrual cycle?
- produced by the pituitary gland
- stimulates release of egg at day 14
What is the role of Progesterone in the menstrual cycle?
- produced in ovaries by the remains of follicule after ovulation
- maintains lining of the uterus during second half of cycle - when progesterone levels fall, lining breaks down
- inhibits release of LH and FSH
How can hormones be used to reduce fertility?
- Oestrogen used to prevent release of egg as level kept permenantly high and inhibits FSH
- Progesterone causes thick mucus that prevents sperm reaching egg
- can be used as pill, patch, implant or IUD
How can barriers be used as contraception?
- stop sperm meeting egg
- condoms prevent sperm meeting egg and are the only contraception that protect against STD’s
How is sterilisation used to avoid pregnancy?
- cutting or tying fallopian tubes or sperm ducts - permenant procedure
Natural methods of contraception
- only having intercourse in the least fertile sections of cycle
What is the role of auxin?
- plant growth hormone
- controls growth near tips of shoots and roots
- controls growth in response to light (phototropism) and gravity (gravotropism)
How does auxin affect the shoots?
- shoot grows towards light
- when shoot tip exposed to light more auxin accumulates on the side that’s in the shade so shoot bends towards light - when a shoot growing sideways, gravity produces unequal distribution of auxin in the tip with more auxin on lower side
- lower side grows faster with more auxin on lower side
How does auxin affect roots?
- root growing sideways always has more auxin on lower side
- in a root extra auxin inhibits growth so cells on top elongate faster and root bends downwards
How can auxins kill weeds?
disturb normal growth patterns of broad-leaved plants which soon kills them
How can auxins cause growth from cuttings with rooting powder?
- add rooting powder and stick in soil - produce roots rapidly that start growing as new plants
- produce lots of clones very quickly
How can auxins be used to grow cells in tissue cultures?
- auxins added to growth medium to stimulate cells to divide
How can gibberelins be used?
- Controlling dormancy - make them germinate at different times of the year they normally wouldn’t
- Inducing flowering - flower without changes in environmental conditions
- Growing larger fruits
How can ethene be used in plants?
- influences growth of plant by controlling cell division and stimulates enzymes that cause fruit to ripen
- fruit can be picked unripe and ripened using ethene on the way to shops
- can also be delayed with chemicals that block ethenes effect
