homeostasis and response

• homeostasis

  • maintaining stable internal environment - cells need right condition in order to function
  • automatic controls = nervous and hormonal communication regulate internal environment
  • made of three main component = receptors , coordination centres and effectors
• negative feedback

  • counteracts changes
  • receptor detects stimulus too high
  • coordination centre receives and processes information then organises response
  • effector produces a response
  • and vice versa
• central nervous system

  • consist of brain and spinal cords only in animals with back bones . in mammals cns is connected to the body by sensory neurones and motor neurones
• sensory neurones

  • neurones that carry information as electrical impulses from receptors to cns
• motor neurones

  • neurones that carry electrical impulses from cns to effector
• effectors

  • muscles and glands which respond to nervous impulses
• receptors

  • can be = taste , sound and balance , light , pain , smell
• central nervous system coordinates a response

  • stimulus = cat
  • receptor = light receptors in retina
  • sensory neurone
  • cns = brain
  • motor neurone
  • effector = muscle
• synapses

  • connects neurones
  • nerve signal is transferred by chemicals which diffuse across the gap
  • set of ned electrical signal in next neurone
• reflexes

  • prevent injury
  • rapid , automatic responses to certain stimuli that dont involve conscious part of Brain
• reaction time

  • measured by using drop test or computer
• brain

  • responsible for complex behaviours
  • made up of billions of interconnected neurones
  • cerebal cortex = outer layer - responsible for consciousness , intelligence , memory and language
  • cerebellum = responsible for muscle coordination
  • medula = controls unconscious activities - breathing
• studying the brain

  • patients with brain damage - see what the damage area has an effect one person

  electrically simulating = pushing tiny electrode in certain part and see what response is

  mri scans - produce pictures of brain structures

  complex and delicate carries risk , physical damage
• eye

  • sclera = tough supporting wall of eye
  • cornea = transparent outer layer at front of pupil - refracts light into eye
  • iris contains muscles that control diameter of pupil = how much light enters
  • shape of lens controlled by ciliary muscles and suspensory ligaments
  • optic nerve = carries impulses from receptors to brain
• light intensity

  • bright light = light receptors detect this , circular muscles contract , radial muscles relax
  • dim light = radial muscles contract , circular muscles relax
• sight

  • near objects = ciliary muscles contract , slacken suspensory ligament , lens fat , increase light refraction
  • distant objects = ciliary muscles relax , suspensory tighten , lens thin , les refracted light
• vision defects

  • long sighted (hyperopia) - unable to see near objects
  • lens wrong shape and doesn't refract eyeball enough , eyeball too short
  • images brought into focus behind retina
  • convex glasses fixing
  • shortsighted(myopia) - unable to see far
  • lens wrong shape and refract light too much eyeball too long
  • images brought into focus before retina
  • concave lenses = fixing
• fixing vison

  • contact lenses - risk of infection
  • laser eye surgery - vaporise tissue changing shape or cornea , risk of complication
  • replacement lens surgery - lens removes artificial inserted - risk of damage to retina
• optimum body temperature = 37 degrees
• too hot

  • sweat produced by sweat glands, evaporates from skin , transferring to environment
  • blood vessels supplying skin dilate - blood flows closer to surface - vasodilation
• too cold

  • hairs stand up to insulating layer of air
  • no sweat produced
  • blood vessels supplying skin capillaries constrict - close of skins blood supply - vasoconstriction
  • shiver , needs respiration which transfers energy
• negative feedback

  • temperature receptors detect core body temp too high
  • thermoregulatory centre acts as coordination centre - receives information from temp receptors and trigger effector
  • effector produce a response and counteract change
  • or vice versa
• endocrine system

  • hormones are chemical messengers sent in blood
  • tend to have long lasting effects
  • pituitary gland - produces many hormones that regulate body conditions called master gland
  • thyroid - produces thyroxine , involved in regulating metabolism , heart rate , temperature
  • ovaries - produce oestrogen , involved in menstrual cycle
  • testes - produce testosterone , controls puberty and sperm
  • adrenal gland - produces adrenaline , prepare body for fight or flight
  • pancreas - produces insulin , regulate blood glucose
• neves vs hormones

  • nerves = fast action , act for short amount of time , act on precise area
  • hormones = slower action , act for long time , act in general way
• blood glucose too high

  • glucose too high - insulin added
  • insulin secreted by pancreas
  • too much glucose but also insulin in blood
  • glucose moves from blood into liver and muscles cells
  • insulin makes liver turn glucose into glycogen
  • blood glucose reduced
• blood glucose

  • insulin and glucagon control blood glucose
  • excess glucose stored as glycogen in liver and muscles
  • changes monitored and controlled by pancreas
• blood glucose too low

  • glucagon is added
  • blood with too little glucose
  • glucagon secreted by pancreas
  • too little glucose but glucagon as well
  • glucagon makes liver turn glycogen into glucose
  • glucose released into blood by liver
  • blood glucose increased
• type 1 diabetes

  • where pancreas produce enough insulin
  • need insulin therapy , limiting intake of carbs and regular exercise
• type 2 diabetes

  • person is resistant to their own insulin
  • overweight can increase chance controlled by diet and exercise
• kidneys

  • filter clean blood
  • urea - proteins converted into fats and acrbohydrates sotred - happens ion liver - deamination
  • ammonia - waste products and toxic so converted to urea , transported in kidneys and filtered into urine
  • ions taken in body in food , absorbed into blood - can damage cells
  • ions lost in sweat , reabsorbed into blood after filtration
  • lose water via sweat and when we breathe out
  • balanced by what we consume , removed by kidneys
• negative feedback

  • receptor in brain detects water content too high
  • coordination centre in brain receives information and coordinates a response
  • pituitary gland releases adh , less water is reabsorbed from kidney tubules and vice versa
• kidney failure

  • remove waste substances from blood
  • dialysis machines filter blood - done regularly , blood flows between partially permeable membrane by dialysis fluid , has same concentration of ions and glucose as healthy blood , useful ions and glucose wont lost , waste products diffuse across barrier , cause blood cots or infection
  • kidney transplants are cure , can be rejected
• hormones

  promotes sexual characteristics at puberty

  development of facial hair in men , breast in women and eggs maturing
• menstrual cycle - four stages

  • stage 1 - menstruation starts , uterus lining breaks down for about 4 days
  • stage 2 - uterus lining build up again day 4 to 14
  • stage 3 - egg develops and is released - ovulation
  • stage 4 - wall is maintained day 14-28
  • controlled by 4 hormones
  • fsh follicule stimulating hormones
  • produced in pituitary gland
  • causes egg to mature in ovaries in a structure called follicule
  • stimulates ovaries to produce oestrogen
• oestrogen

  • produced in ovaries
  • causes lining of uterus to grow
  • stimulates release of lh and inhibits release of fsh
• lh (luteinising hormone)

  • produced by pituitary gland
  • stimulates release of egg
• progesterone

  • produced in ovaries
  • inhibits release of lh and fsh
  • maintains lining of the uterus
• hormones can reduce fertility

  • oestrogen - prevents the release of an egg
  • progesterone - produces thick mucus , preventing sperm
  • the pill - contains both , 99% effective , cause side effects doest protect stds
• controlling fertility

  • barriers stop eggs and sperm meeting
  • sterilisation involves cutting fallopian tubes or sperm duct
  • natural methods - avoiding sexual intercourse when most fertile
  • abstinence can increase fertility
• hormones increase fertility

  • fhs and lh can stimulate ovulation
  • pros - helps women get pregnant
  • cons - doesn't always work , unexpected multiple pregnancies