topic b5- homeostasis and response

• homeostasis

  • maintaining a stable internal environment (inside body)
  • regulation of the conditions in response to change in internal + external conditions
• component of control system

  • receptors- to detect stimuli (changes in environment)
  • coordination centres- receive/ process info from receptors + organise a response
  • effectors- produce a response to counteract change + restore optimal conditions
  • when the level of something becomes too high or too low the body uses negative feedback to bring it back to normal
• three things that are maintained by control system

  • body temperature
  • blood glucose levels
  • water content
• the nervous system

  it detects and reacts to stimuli
• neurones

  cells that carry info as electrical impulses in the nervous system
• the nervous system:

  • stimuli- the change
  • receptor- detect the change
  • sensory neurone- carries info from receptor to cns (electrical impulses)
  • cns- decides a response and brain + spinal cord, connects to neurones
  • motor neurone- carries info as electrical impulses from cns to effector
  • effector- muscles, contract; glands, secrete hormones
  • response- respond to the change
• the nervous system- e.g. burning your hand (touching something hot)

  • receptor- detect it's too hot
  • cns- decides to move hand away
  • effector- tells response to move hand away
  • motor/ sensory neurone carry info via electrical impulse
• synapse

  • the connection between 2 neurones
  • a nerve signal is transferred across a synapse by the diffusion of chemicals
• synapse example:

  
• reflexes

  • rapid, automatic response to certain stimuli that don't involve the conscious part of the brain
  • it reduces the chance of injury (example on previous card)
• relay neurones connect sensory neurones to motor neurones chemicals diffuse across

  • sensory
  • synapse
  • relay
  • synapse
  • motor
• PRACTICAL- investigating reaction time (how quickly you respond)

  1. a person should sit with their arm resting on the edge of a table
  2. hold a ruler between their thumb and finger, making sure the 0 is level
  3. let go of the ruler without warning
  4. the person should catch the ruler as quick as they can
  5. the number on the ruler where it's caught is the reaction time; the higher the number, the slower the reaction time
  6. repeat and calculate a mean
• PRACTICAL- investigating reaction time (how quickly you respond)

  caffeine can speed up reaction time:

  7. drink caffeine and repeat experiment keeping the variables the same

  • the reaction time should become quicker
• the endocrine system

  • made up of glands that secrete chemicals (hormones) into the bloodstream, which carries them to the target organs
  • the pituitary gland
  • thyroid gland
  • adrenal gland
  • the pancreas
  • ovaries
  • testes
  • nerves
  • hormones
• the pituitary gland

  • master gland
  • regulates body conditions
  • stimulates other glands
• thyroid gland

  • produces thyroxine which regulates:
  • HR
  • temp
  • rate of reaction
• adrenal gland

  • produces adrenaline
  • prepare for fight or flight
• the pancreas

  • produces insulin
  • which regulates the blood glucose level
• ovaries

  • produces oestrogen
  • which is involved in the menstrual cycle
• testes

  • produces testosterone
  • which controls puberty + sperm production
• nerves: -------DIFFERENCES-------- hormones:

  • very fast reaction - slower action
  • act for a very short time - act for a very long time
  • act on a very precise area - act in a more general way
• to reduce blood glucose- INSULIN is added

  1. blood with too much glucose
  2. pancreas detects high blood glucose and secretes insulin
  3. insulin causes glucose to move into cells
  4. insulin causes liver to turn glucose into glycogen (stored in liver + muscles)
  5. blood glucose reduces
• to increase blood glucose- GLUCAGON is added

  1. blood with too little glucose
  2. glucagon secreted by the pancreas
  3. too little glucose but glucagon as well
  4. glucagon causes liver to turn glycogen to glucose, (released from the liver)
  5. blood glucose increased
• insulin + glucagon work in a negative feedback system/ cycle
• diabetes

  • a condition that affects your ability to control your blood sugar level
• type 1 diabetes

  • cause- pancreas produces little or no insulin
  • effect- blood glucose can rise to dangerously high levels
  • treatment- insulin injections
• type 2 diabetes

  • cause- cells no longer respond to insulin properly (own insulin)
  • effect- blood glucose can rise to dangerously high levels
  • treatment- carbohydrate-controlled diet + regular exercise
• obesity

  • is a major risk factor for type 2 diabetes
  • diet- sedentary lifestyle
• puberty

  sex hormones are released which promote sexual characteristics
• puberty- men

  • testosterone stimulates sperm production
• puberty- women

  • oestrogen, menstrual cycle
• stage 1 of the menstrual cycle

  day 1- menstruation starts- the uterus lining breaks down for 4 days
• stage 2 of the menstrual cycle

  • uterus lining builds up again from day 4-14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg
• stage 3 of the menstrual cycle

  an egg develops and is released from the ovary at day 14- ovulation
• stage 4 of the menstrual cycle

  • wall is maintained for about 14 days until day 28
  • if no fertilised egg has landed on the uterus by day 28, the wall breaks down and the cycle starts again
• the menstrual cycle is controlled by 4 hormones

  • FSH
  • oestrogen
  • LH
  • progesterone
• FSH (follicle stimulating hormone)

  • produced in pituitary gland
  • causes an egg to mature in one of the ovaries, structure is called a follicle
  • stimulates ovaries to produce oestrogen
• oestrogen

  • produced in the ovaries
  • causes uterus lining to grow
  • stimulates the release of LH and inhibits release of FSH
• LH (luteinising hormone)

  • produced in pituitary gland
  • stimulates the release of an egg at day 14- ovulation
• progesterone

  • produced in the ovaries after ovulation
  • maintains uterus lining in the 2nd half of the cycle
  • inhibits release of LH and FSH