biology p1

• homeostasis is the regulation of the conditions inside your body, to maintain a stable environment.
• receptors detect a stimulus ( change in environment )
• coordination centre receives and processes information then organises a response
• effector produces a response which counteracts the change
• multicellular organisms evolved, and develop nervous and hormonal communication systems
• central nervous system consists of brain and spinal cord, only in mammals, connects to the body by sensory and motor neurones
• sensory neurones carry information as electrical impulses from receptors to the cns
• motor neurones carry electrical impulses from cns to effectors
• effectors are all your muscles and glands responding to nervous impulses
• synapses connect two neurones, nerve signal is transferred by chemicals which diffuse across the gap, the chemicals then set off a new electrical signal in the next neurone
• reflexes are rapid and an automatic response to a certain stimuli
• neurones in reflex arc go through spinal cord or through unconscious part of the brain, when a stimulus is detected by receptors, impulses are sent along a sensory neurone to the cns, impulses reach the synapse and trigger chemicals to be released, impulses travel along motor neurone to the effector, muscle then contracts and moves body
• practical- reaction time person to be sitting down with arm resting on edge of table, holding a ruler vertically between thumb and forefinger let go without any warning, the person catching the ruler should do so as quickly as they can, repeat test several times then calculate mean distance that ruler fell
• caffeine speeds up a persons reaction time, and it is a drug
• hormones are chemical molecules released directly into the blood they are carried in the blood to other parts of the body, but only affect target organs, hormones control things in organs and cells which need constant adjustment , hormones are produced in various glands called the endocrine glands, hormones tend to have long-lasting effects
• pituitary gland produces many hormones that regulate body conditions, hormones act on other glands directing them to release hormones that bring about change
• ovaries are in a female only, produces oestrogen which is involved in menstrual cycle
• thyroid produces thyroxine which is involved in regulating things like rate of metabolism and heart rate and temperature
• adrenal gland produces adrenaline which prepares the body for 'fight' or 'flight'
• pancreas produce insulin which regulates glucose levels in the blood
• nerves are very fast, act for a short amount of time and act on a precise area
• hormones are slower, act for a long time, and act in more of a general way
• blood with too much glucose- insulin which is secreted by the pancreas is added and glucose moves from blood into liver and muscle levels, blood glucose reduced
• blood with too little glucose- glucagon secreted by the pancreas is released, glucose is released into blood by liver and blood glucose increases
• type 1 diabetes is where the pancreas produces little or no insulin, cared with insulin therapy which involves several injections but also limiting intake of food rich in simple carbohydrates which cause blood glucose to rise rapidly, and also taking regular exercise to remove excess glucose
• type 2 diabetes is where a person is resistant to their own insulin, body produces insulin but their cells don't respond properly to the hormone, being overweight increases chance of developing type 2 diabetes, can be controlled by eating a carbohydrate controlled diet and regular exercise
• in men, testosterone is produced by the testes and stimulates sperm production
• in women, oestrogen is produced in the ovaries
• day1 of menstruation cycle, uterus lining breaks down for about four days, stage2 uterus lining builds up again from days 4 to 14 and turns into a thick spongy layer ready to receive a fertilised egg, stage3 egg develops and is released from ovary ( ovulation ), stage4 wall is maintained for about 14 days until day 28, if no fertilised egg is landed on the uterus wall by day 28 spongy lining breaks down and cycle starts again
• fsh ( follicle stimulating hormone )- produced in pituitary gland and causes an egg to mature in one of the ovaries , stimulates ovaries to produce oestrogen
• oestrogen, produced in the ovaries, causes lining of the uterus to grow and stimulates the release of lh and inhibits release of fsh
• lh ( luteinising hormone ), produced by the pituitary gland and stimulates the release of an egg at day 14
• progesterone, produced in the ovaries and maintains the lining of the uterus , when progesterone levels decrease lining breaks down, inhibits release of lh and fsh
• oestrogen can be used as a contraception, as it prevents the release of an egg, as it inhibits the production of fsh
• progesterone reduces fertility by stimulating the production of thick mucus which prevents any sperm getting through and reaching an egg
• pill is an oral contraceptive with both oestrogen and progesterone , 99% effective and can cause side effects like headaches and nausea
• progesterone only pill, has fewer sider effects and is as effective as the combined oral contraceptive pill
• contraceptive patch contains oestrogen and progesterone and sticks to the skin lasting around a week
• contraceptive implant is inserted under the skin of the arm, releases continuous amount of progesterone stopping ovaries releasing egg and makes it harder for sperm to swim to the egg, can last around three years
• contraceptive injection contains progesterone can last 2-3 months