biology 7

homeostasis

important to regulate body levels to keep within the target levels, e.g. blood sugar and body temperature so that the enzymes are at the optimum temperature to maximise rate of reaction

osmoregulation regulates the concentration of water and mineral ions; to keep the concentrations the same inside the cells as around them. t

regulate blood sugar - keep in target range and avoid health issues

his protects cells by stopping too much water from entering or leaving them by osmosis.

thermoregulation - body temperature should be roughly 37 degrees, body temperature in the blood and dermis of skin is sensed and monitored by the hypothalamus (brain region)

warm skin - hairs flatten (epidermis), sweat appears from sweat glands (dermis) and evaporates using heat from the skin (epidermis), vasodilation (dermis)

cold skin - hairs stand on end (epidermis) to trap air and insulate (via contraction of erector hair muscles in the dermis), no sweat, vasoconstriction (dermis) of arterioles means less blood flow near skin so you are not losing as much heat energy to the atmosphere, shivering, rapid muscle contractions release heat energy from respiration

treating hypothermia - dry, gradually warm, sugar, warm intravenous fluids

diabetes/blood sugar

blood sugar can be tested with Benedict’s test, Benedict’s solution + urine + heating = red for lots of sugar, blue for no sugar, orange for moderate, green for traces

type 1 diabetes - caused by a deficiency or problem in the production of insulin (possibly even pancreatic disease) - controlled with insulin injections or monitoring - symptoms; thirsty, tired, thin because all glucose remains in the blood and isn’t being used for energy or fat stores and so it’s flushed out in the urine

type 2 diabetes - caused by obesity and over-consumption of sugary and starchy foods which causes the body to develop insulin resistance and thus the body doesn’t respond to insulin - healthy diet and exercise and some drugs can help reduce blood sugar or increase cell responsiveness to insulin - symptoms; thirsty, tired, thin because all glucose remains in the blood and isn’t being used for energy or fat stores and so it’s flushed out in the urine

waist : hip ratio = waist circumference/hip circumference

bmi (high bmi strongly correlates with type 2 diabetes) = mass (kg)/height (m²)

this is better than just mass because it takes other factors into account like height, however doesn’t take into account muscle mass

diabetes explanation - don’t produce or respond to insulin → target cells are not triggered to uptake glucose nor store it as glycogen → glucose stays in blood and is flushed out in urine → no energy

glucagon - the glycogen is the energy stored in the liver cells and when blood glucose falls too low, GLUCAGON is released from PANCREAS, which converts glycogen back to glucose which is released into the blood to raise glucose concentration, as blood glucose increases, the amount of glycogen being released lowers

menstrual cycle

days 1-4, stage 1 - uterus lining breaks down and is lost with an unfertilised egg causing a period

4-14, stage 2 - menstruation ends and uterus lining starts to thicken again until it is a spongy layer full of blood vessels

14, stage 3 - ovulation occurs when the ovary releases the egg

if that egg is fertilised it will lead to pregnancy (menstruation stops, egg embeds into uterus lining and uterus lining will not be shed)

if no fertilisation occurs, the egg will be maintained until day 28, before it starts to break down and it happens again

when progesterone and oestrogen levels are low the uterus lining will break down -> pituitary gland responds to the low levels of oestrogen and release FSH -> FSH causes the follicles to mature in the ovaries -> maturing follicles stimulates oestrogen levels -> oestrogen thickens and grows the uterus lining -> high oestrogen stimulates LH surge -> which then stimulates ovulation -> the follicle ruptures and the egg is released -> the follicles develop into a structure called corpus luteum (dead follicles) -> corpus luteum releases progesterone -> increase in progesterone inhibits FSH and LH -> causes progesterone to fall and when this happens at the same time as a low oestrogen level, the uterus lining breaks down

controlling pregnancy - barrier methods block STIs, don't affect natural body/hormones, can be less invasive, can break easily, can have less reliability

hormonal methods - more reliable, have to take every day, invasive, affect hormones, changes when coming off

hormonal contraception uses a progesterone-like hormone (either on its own or with oestrogen). this prevents the natural fall of concentrations at the end of the menstrual cycle which inhibits LH and FSH so a person's eggs can't mature and be released to the uterus

ART - hormones and other techniques to increase the chance of pregnancy

clomiphene therapy - increases FSH and LH which increases likelihood of a mature egg being released

IVF - helps blocked oviducts or few sperm cells, insert sperm cells into egg

urine/kidneys

general kidney - to balance water and mineral salts in the blood. to filter out urea (made from excess animo acids in the liver)

each kidney functions separately (have two but can live with one)

without kidneys, toxic urea builds in the blood ad osmoregulation fails

each kidney consists of thousands of functioning units called nephrons

the process of urine production takes place in the kidneys

(urine is made up of 95% water, 2% urea, small amount of different salts)

filtration - blood flows into kidney through renal artery -> artery divides into a network of capillaries called glomerulus (surrounded by blood vessels) -> the blood exits the kidney through the renal vein

what happens in the glomerulus and bowman's capsule  - the capillaries are 'leaky' due to small spaces between cells

bowman's capsule and glomerulus are adapted to only allow small molecules, urea, water and glucose but not proteins, blood cells which stay in the blood

These move down the nephron where selective reabsorption occurs - reabsorb useful substances that body needs, glucose and some mineral ions

useful substances pumped through first convoluted tubule of the nephron by active transport (no glucose usually left in urine)

water is reabsorbed by osmosis depending on how much the body needs (happens in the loop of Henley and the collecting duct)

at the end of nephron, remaining fluid flow into ureter called urine

if you are dehydrated, you have less water, then your hypothalamus tells the pituitary gland to release ADH - which changes the permeability of collecting duct (if ADH is present the collecting duct will be very permeable so reabsorb more water in the nephron)

if ADH present small volume of concentrated urine and vice versa

KIDNEY FAILURE - treatments include dialysis (hospital process where your blood is removed and manually filtered) and organ donation

UREA - the liver breaks down amino acids and proteins, etc. the urea is the waste products of this

metabolic rate/hormones

adrenaline (adrenal glands) - prepares the body for fight or flight

1. pupil dilation - improves eyesight

2. activating glycogen - providing your muscles with more energy quickly, as it breaks down the glycogen into glucose (energy) in the liver

3. top intestinal motility - blood supply is diverted to muscles rather than being used in the rest of your body for digestion, etc. - capillary muscles open

4. breathing rate increases- carrying more oxygen and glucose around the body - work harder and faster

5. euphoria - means that your mental state is more positive and confident, increasing awareness in situation and ability to assess the situation rather than being scared

thyroxine - negative feedback loop; low levels of thyroxine → TRH produced in hypothalamus → TSH released from pituitary gland → thyroid released thyroxine → inhibits TRH and TSH

thyroxine is released by the thyroid to control metabolic rate → rate at which energy is stored and released in bodily reactions

hyperthyroidism - very high metabolism, rapidly lose weight but be very hungry, high heart rate, anxious, little sleep

hypothyroidism - gain weight, lethargic, depression

treatments - supplement the thyroid with medication, block TRH or TSH, reduce the size of the thyroid itself through radioactive therapy or surgery

transportation of hormones

only the target organs are affected by a given hormone because only those organs have receptors for the hormone

adrenaline - adrenal gland → heart, lungs, eyes, liver

thyroxine - pituitary gland → thyroid gland → brain, liver, muscle, heart, adipose tissue

insulin - pancreas → kidneys

the endocrine system

consists of glands throughout the body which secrete different types of hormones into the blood

whilst in the blood the hormones come into contact with many tissues, some of which have receptors (hormone specific) which means the hormone can bind to it and act as a signal for changes

pituitary gland - TSH, etc.

thyroid gland - thyroxine

adrenal gland - insulin

pancreas - insulin

testes - testosterone

ovaries - oestrogen