Biology - nerves, hormones and homeostasis Flashcards
what are hormones
chemical messengers released from endocrine glands that travel in blood plasma
hormones will only have an effect on specific cells, which we call target cells
how are nerves and hormones different
hormones are slower
act for a longer period of time
more general effects
hormones limited by speed of blood passing around the body
thyroxine
- important for regulating basal metabolic rate
- thyroid stimulating hormone (TSH) controls release of thyroxine through negative feedback
- level in blood monitored by hypothalamus
what happens when thyroxine is too high
- TSH released by pituitary gland is inhibited
- less thyroxine is released from thyroid gland
- level falls back to normal
what happens when thyroxine is too low
- TSH is released by pituitary gland
- more thyroxine is released from thyroid gland
- level increases back to normal
what is adrenaline
- released by adrenal glands
- responsible for fight or flight response
what does adrenaline do
- increases heart rate
- stimulate liver to break down glycogen to use glucose for energy
- increases breathing rate
- causes dilation of vessels to direct blood to muscles
- causes pupils to dilate
oestrogen
main female reproductive hormones and produced in the ovaries
testosterone
main male reproductive hormones and is produced in the testes
follicle stimulating hormone (FSH) function
- produced by pituitary gland
- acts in ovary
- stimulates ovaries to develop follicle containing an egg and produce oestrogen
oestrogen function
- produced by ovaries
- stimulates uterus lining to thicken
- inhibits FSH and LH
luteinising hormone (LH) function
- produced by pituitary gland
- acts on ovaries
- stimulates mature follicle to release egg around day 14 (ovulation)
progesterone function
- secreted by empty follicle in ovary (corpus luteum)
- maintains the lining of the uterus so that the fertilised egg can implant
- inhibits LH
- decrease levels cause the lining to break down (menstruation)
hormonal contraception
- oral pill
- skin patch
- implant
- injection
- intrauterine devices
oral pills (combined or progesterone only)
- not 100% effective
- side effects, e.g. nausea, headaches
- does not protect against STDs
- need to take every day
skin patch
- same hormones as combined pill
- patch changed every week
implant
- lasts up to 3 years
- continuous amount of progesterone
injection
lasts up to 3 months
intrauterine devices
- T-shaped device inserted into the uterus
- stops implantation and plastic IUDs release progesterone
non-hormonal methods
- barrier methods
- natural methods
- intrauterine devices
- surgical methods
barrier methods
- condoms, diaphragm, spermicide
- condoms protect against STDs
natural methods
- abstinence = 100% effective
- planning to avoid sex during most fertile time of ovulation = not very effective
intrauterine devices
- copper IUDs instead of plastic - can stop sperm surviving
surgical methods
- cutting/tying structures e.g. oviducts or sperm ducts
homeostasis
process of maintaining constant internal environment
negative feedback
process where a condition’s level becomes too high or too low, and this is fed back to the brain
brain then alters the level of this condition to bring back to the normal value
what is the thermoregulatory system
in hypothalamus
detects changes in temperature
what happens when body temperature is too high
- more sweating occurs to maintain body temperature
- kidneys respond to more water being lost in sweat by producing smaller volume of more concentrated urine to avoid dehydration
- vasodilation occurs to remove more heat from blood
what happens when body temperature is too low
- less sweating occurs
- kidneys respond by producing a higher volume of less concentrated urine
- this avoids excess water being taken by osmosis, causing the cells to burst
- hairs stand up on end to create an insulation layer
- vasoconstriction occurs to reduce heat loss from blood
- involuntary muscle contraction (shivering) occurs to raise body temperature
blood glucose is too high
- insulin hormone is released from pancreas into blood
- decreases glucose levels in blood
blood glucose is too high
when glucose is too low, hormone called glucagon is released to increase glucose levels
water content is controlled by
- water content of blood is controlled by a hormone called ADH
- released into blood by pituitary gland
water content is too high
less ADH is released so the kidneys reabsorb less water, and more urine is produced
alcohols affect on ADH
alcohol suppresses ADH production, so higher volumes of dilute urine are produced
ecstasy effect on ADH
ecstasy causes an increase of ADH production, so that smaller volumes of very concentrated urine are produced
what are communicable diseases
infectious diseases that are caused by pathogens
what are pathogens
viruses
bacteria
protists
fungi
HIV/AIDS
- retrovirus - RNA and contains reverse transcriptase
- HIV passes through infected body fluids
- reduces white blood cell count, meaning a weakened immune system which leads to AIDS (acquired immune deficiency syndrome)
- no cure but anti-retroviral drugs can control infection
influenza
- spread in airborne droplets
- vaccines containing inactive/weakened virus –> forms an immune response where antibodies to pathogen’s antigens are created and retained in memory cells
- when the person comes into contact with real virus, memory cells can produce antibody faster and in larger amounts so that the person doesnt have symptoms (secondary immune response)
measles
- spread by direct contact e.g. touching infected person, and by airborne mucus droplets (for example sneezing)
- red blotchy rash that spreads across skin
- mmR vaccine contain live attenuated version of virus
tobacco mosaic disease
attacks tobacco plants
salmonella food poisoning
- occurs when someone eats food contaminated with bacteria
- oral rehydration supplements can be given to replace lost electrolytes from diarrhoea and vomiting caused by the bacterium
what are non-communicable diseases
not infectious, and caused by interaction of many different factors
3 different cardiovascular diseases (CVD)
- coronary heart disease
- hypertension
- stroke
what is coronary heart disease
an atheroma or blood clot blocking the coronary arteries, stopping oxygen and glucose from reaching the heart and causing anaerobic respiration to occur, which leads to cell death
what is hypertension
consistently raised blood pressure (over 140/90mmHg), due to narrowing of artery lumen
what is stroke
narrowing or hardening of arteries supplying the brain tissue, which leads to part of the brain becoming deprived of oxygen and glucose and dying
CVD risk factors
- diet high in cholesterol/salt/fat
- too little exercise
- smoking
- obesity
- non-modifiable risk factors e.g. genetics, age, gender
3 kinds of treatment for CVD
- life long treatment
- surgical procedures
- lifestyle changes
how can life-long treatment treat CVD
- statins: reduce cholesterol production to avoid atheroma blocking arteries
- anticoagulants: reduce likelihood of blood clots
- anti-hypertensive drugs: relax blood vessels to reduce blood pressure
how can surgical procedures treat CVD
- stent: a mesh tube is placed into coronary arteries to increase the lumen diameter so that blood can flow freely
- bypass: a small part of a blood vessel is removed from elsewhere in the body
