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Unit 2 Physiology and Health Summary Notes Physiology and health Reproduction Testes Gametes are produced from germline cells Testes produce sperm in the seminiferous tubules (Seminiferous tubules = tiny tubules in the testes) Seminiferous tubules Link up into coiled tubes that connect to the sperm duct Sperm leave the testis through the sperm duct Interstitial cells Are found between the seminiferous tubules Produce testosterone = which into the bloodstream passes Motility of sperm Sperm are said to be motile = this motility requires a fluid and a source of energy Fertilisation is dependent on this motility as the sperm must be able to make their way up into the uterus, along the oviducts to a potential egg Prostate gland and seminal vesicles Secrete fluids that maintain the mobility and viability of the sperm Seminal vesicles Secrete a liquid high in fructose = this sugar provides the sperm with the energy needed for motility after ejaculation This liquid also contains hormone-like compounds that stimulate contractions of the female reproductive tract = these movements help the sperm to reach the oviduct faster than swimming along would Prostate gland Secretes a thin lubricating liquid that contains enzymes = these enzymes maintains the optimum viscosity of the fluid which allows the motility of the sperm Semen Semen = the name given to the mix of all of these liquids = milky liquid released in ejaculation Ovaries Female gamete eggs (ova) are produced in the ovaries by germline cells Contain immature ova in various stages of development Each ovum is surrounded by a follicle which o protects the developing ovum o secretes hormones (oestrogen) Once the ova has matured it is released (ovulation) into the oviduct where it may be fertilised by sperm to produce a zygote The follicle then develops into a corpus luteum = this structure releases the hormone progesterone Hormonal control of reproduction Hormones control the onset of puberty, sperm production and the menstrual cycle Hormonal onset of puberty The hypothalamus releases a hormone that stimulates the pituitary gland to release 2 hormones 1. FSH = follicle-stimulating hormone 2. In men = ICSH = interstitial cell-stimulating hormone or in women = LH = luteinising hormone These hormones which are released at puberty trigger Sperm production in men Menstrual cycle in women Hormonal control of sperm production FSH and ICSH are produced by the pituitary and travel in the bloodstream to the testes FSH = promotes sperm production in the seminiferous tubules ICSH = promotes interstitial cells to produce testosterone Testosterone also = stimulates sperm production and activates the prostate gland and seminal vesicles to produce secretions (see previous page!) Negative feedback control of testosterone by FSH and ICSH As the concentration of testosterone increases it reaches a level where it starts to inhibit the secretion of FSH and ICSH The decrease in FSH and ICSH will lead to a decrease in testosterone This will then allow the pituitary gland to produce FSH and ICSH again = which will then stimulate production of testosterone This self-regulating mechanism is known as negative feedback Hormonal control of the menstrual cycle Menstrual cycle Lasts for ~28days (this can vary from woman to woman) The first day of menstruation is regarded as day one of the cycle Every cycle is continuous with the cycle before and the cycle after Has 2 phases 1. Follicular phase 2. Luteal phase Follicular phase Is the first half of the cycle FSH from the pituitary stimulates o Development of a follicle o The production of oestrogen by the follicle Oestrogen stimulates proliferation of the endometrium = preparing it for implantation Oestrogen also affects the consistency of cervical mucus = making it more easily penetrated by sperm This high concentration of oestrogen (peak levels) stimulates a surge in the secretion of LH (by the pituitary) This surge of LH causes ovulation = release of the ovum Which is now moved slowly along the oviduct During a period ~3-4 in the oviduct is where fertilisation may take place Fertilisation is when the nuclei of the gametes fuse to produce a zygote Luteal phase Is the second half of the cycle LH stimulates the follicle (which remains inside the ovary after ovulation) to become the corpus luteum = this is a gland-like structure that secretes progesterone and oestrogen Progesterone concentration will increase and promotes further development and vascularisation (increase in blood vessels) of the endometrium = becomes thick and spongy This prepares the endometrium to receive a blastocyst (formed after repeated rounds of mitosis of the zygote) if fertilisation occurs The high concentrations of oestrogen and progesterone inhibit the production of FSH and LH by the pituitary gland = this means that no new follicles will develop at this time o Negative feedback If fertilisation doesn’t occur the lack of LH leads to the degeneration of the corpus luteum by ~day 22 This leads to a rapid drop in progesterone (and oestrogen) By day 28 the progesterone (and oestrogen) levels are at such a low concentration that the endometrium is no longer maintained and menstruation begins = loss of the inner layer of endometrium, this is accompanied by a small volume of blood This continues for a few days and the cycle starts again Influence of pituitary hormones on the ovaries FSH and LH are produced by the pituitary gland and travel in the bloodstream to the ovaries FSH = stimulates the development and maturation of each follicle and stimulates tissue in the ovary to secrete the sex hormone oestrogen LH = stimulates ovulation and it also stimulates the corpus luteum to secrete the sex hormone progesterone Oestrogen and progesterone are called ovarian hormones Influence of ovarian hormones on uterus and pituitary gland Oestrogen Stimulates proliferation (cell division) of the lining of the uterus = endometrium This allows the repair of the endometrium after menstruation which would then allow implantation of a blastocyst It also stimulates the secretion of LH by the pituitary gland Progesterone Promotes further development and vascularisation of the endometrium = endometrium becomes a spongy layer which has lots of blood vessels This ready’s the endometrium for implantation of the blastocyst It also inhibits the secretion of FSH and LH (by pituitary gland) Biology of controlling fertility Is used in the design of treatments for infertility and producing contraception Fertile periods Men are continuously fertile Due to the negative feedback effect of testosterone This maintains a relatively constant concentration of FSH and ICSH in the bloodstream = which means a fairly constant concentration of testosterone is secreted and thus sperm produced Women show cyclical fertility The interaction of pituitary and ovarian hormones results in a period of fertility which is restricted to ~1-2 days immediately after ovulation Calculation of the fertile period Temperature During the menstrual cycle menstruation and ovulation are separated by ~ 2 weeks ~1 day after ovulation (LH surge that causes the egg to be released) progesterone produced causes in increase in body temperature of ~0.2-0.5°C This increase in temperature continues for the rest of the luteal phase The period of fertility only lasts for ~1-2 days after ovulation After this the infertile phase is resumed After the 3rd daily recording of the higher temperature = the unfertilised egg will have disintegrated Mucus Cervical mucus is secreted into the vagina during the fertile period = it is thin and watery = this allows the sperm easy access to the uterus After ovulation the mucus gradually increases in viscosity (thickness) = this is due to the action of progesterone This indicates the return to the infertile phase Use of indicators Women can use body temperature and viscosity of mucus as an indicator to calculate her fertile period = this is useful for couples who are trying to get pregnant If the couple can identify the fertile period and have sex within this period it is more likely to result in fertilisation Treatments for infertility Stimulating ovulation Some women may not ovulate due to an underlying factor e.g. the pituitary gland fails to produce enough FSH or LH In these cases ovulation can be stimulated by drugs that prevent the negative feedback effect of oestrogen on FSH secretion (during the luteal phase) or drugs that mimic the action of FSH and LH Sometimes these drugs can cause ‘super-ovulation’ = this can lead to multiple births These drugs can also be used to promote the release of eggs that can then be used in IVF Artificial insemination Natural insemination = introduction of semen into the female reproductive tract by sexual intercourse Artificial insemination = introduction of semen into the female reproductive tract by some other means e.g. sperm in a syringe This can be used if a man has a low sperm count = several samples of semen can be collected over some time and preserved by being frozen The samples can then be defrosted and combined for release together into his partners reproductive tract This is done during her fertile period This can also be used to insert semen from a sperm donor (e.g. women who don’t have a partner or who’s partner is sterile) ICSI = intra-cytoplasmic sperm injection Used if mature sperm are defective or very low in number The head of the sperm is drawn into a needle and injected directly into the egg to achieve fertilisation Is quite commonly used in IVF In vitro fertilisation = IVF Can be used if a woman has a blocked oviduct so is unable to become pregnant without help The woman is given hormone treatment = this stimulates multiple ovulation These eggs are then removed surgically using a special syringe The eggs are then mixed with sperm in a culture dish (can also use ICSI) and fertilisation takes place The zygotes (fertilised eggs) are then incubated in nutrient medium for 2-3 days = this is to allow cell division = when it is ~8 or more cells it can then be used 2 or 3 embryos are picked and inserted into the woman’s uterus (via the vagina) for implantation The hormone treatment will also have made the endometrium ready for implantation The remaining embryos are frozen and stored = can be used in a 2nd attempt Before embryos are implanted pre-implantation genetic screening (PGS) is done o Checks each embryo for single gene mutations and common chromosomal abnormalities o This is a non-specific broad screening Pre-implantation genetic diagnosis (PGD) can also be carried out o Specific screening that can be used to check for a known chromosomal abnormality or gene mutation Ethics Many people strongly agree with PGS and PGD as people who are at high risk of having a child with a genetic disorder are reassured that they can have a child who will not suffer from the specific genetic disorder Many of these people without IVF would simply choose to not have children due to the risk to the child Some people argue that this doesn’t only help these specific families but society on the whole as it reduces the frequency of these mutations in the gene pool Other people disagree with PGS and PGD as they believe it is morally wrong to interfere with the process of conception by making it selective These people argue that these procedures are the start of eugenics = humans selectively breeding to ‘improve quality’ They also argue that this is the doorway to ‘designer’ children = where people would start to select characteristics and not just select for health e.g. genetic defects Contraception Is when pregnancy/conception is prevented Physical methods of contraception Barrier methods Physically blocks sperm Condom Diaphragm o Dome shaped rubber cap inserted into the woman’s vagina o This blocks the cervix o Inserted before sex Cervical cap o Rubber structure that fits tightly round the cervix o Can be left in for a few days Intra-uterine devices (IUD) IUD is a T-shaped structure fitted into the uterus to prevent the implantation of a blastocyst into the endometrium Lasts months or even years Sterilisation procedures Vasectomy o Doctors cut and tie the two sperm ducts o This prevents sperm being released during sex o After a man has a vasectomy the sperm that are produced but can’t travel down the sperm ducts are destroyed by phagocytes Tubal ligation o Doctors cut and tie the two oviducts o This prevents eggs meeting sperm Sterilisation is highly effective but is usually irreversible Chemical methods of contraception Chemical contraceptives are based on combinations of synthetic hormones that Mimic negative feedback preventing the release of FSH/LH = combination pill Prevent implantation = ‘morning after pill’ Cause thickening of cervical mucus = ‘mini-pill’ Combination pill Pills containing a combination of hormones Oral contraceptive pills usually contain synthetic progesterone and synthetic oestrogen Usually a pill is taken every day for 3 week from the final day of the previous menstrual period This increases the concentration of progesterone and oestrogen = causing negative feedback This means that FSH and LH production by the pituitary is inhibited This low concentration of FSH and LH means that follicle maturation is inhibited and ovulation doesn’t occur During the 4th week of no pills the oestrogen and progesterone concentrations fall and allow menstruation to occur (e.g. bleeding) Mini-pill Only contain synthetic progesterone and not oestrogen Cause thickening of the cervical mucus This reduces the chance of the sperm ever reaching the uterus ‘Morning after’ pills This is also known as an emergency hormonal contraception pill Usually contain higher does of progesterone and oestrogen Taken after unprotected sex = ideally should be taken soon, however can be taken up to 72 hours after These pills prevent implantation from occurring if fertilisation has occurred Ante-natal A variety of techniques can be used to monitor the health of the mother and developing fetus Also known as prenatal Identifies risk of disorder so that further tests and prenatal diagnosis can be offered Include blood pressure, blood types, ultrasound, biochemical tests, diagnostic testing as well as routine blood and urine tests Ultra-sound imaging Ultra-sound scanner used Picks up high-frequency sounds that bounce off the fetus which are then converted to an ultrasound image on a computer screen A dating scan at 8-14 weeks determines the stage of pregnancy and due date An anomaly scan at 18-20 weeks may detect serious physical problems Dating scans are used with tests for marker chemicals which vary normally during pregnancy (measuring a substance at the wrong time could lead to a false positive result – see later) Biochemical tests Detect the normal physiological changes of pregnancy Medical conditions can be detected by a range of marker chemicals that indicate a condition but need not necessarily be part of the condition HCG = human chorionic gonadotrophin o (one of it’s jobs is to stimulate progesterone production = this thickens the endometrium and makes it rich in blood vessels = extremely important for a growing fetus) o Detection of HCG in blood and urine is used in early pregnancy tests A chemical marker AFP is used in assessing the risk of Down’s syndrome, the mother’s age is also taken into account False positives and false negatives Some chemical markers vary in concentration depending on the time in the pregnancy measuring the substance at the wrong time could lead to a false positive result HCG concentration Is high during weeks 6-10 It then decreases However in Down’s syndrome it remains at a high concentration If HCG was measured at 10 weeks this result would mean nothing as normal and Down’s syndrome pregnancy would both be high If a marker is measured at the wrong time in a pregnancy this can lead to a false positive result = would show the fetus to have a condition when it doesn’t Measuring a marker at the wrong time can also give a false negative = marker measured and found to be low when during a normal pregnancy it is also low = suggest a fetus doesn’t have a condition when it actually does To avoid false positives and negatives chemical testing is used carefully in conjunction with scans so as to date the pregnancy and do chemical test at the correct times Diagnostic testing Is a screening test that is used to detect signs and symptoms of a specific condition or disorder If signs are found then the probability of the fetus having the condition is assessed as a degree of risk However a diagnostic test tells us whether or not the fetus has the condition without doubt Diagnostic tests are offered to pregnant woman if o Screening test has indicated a potential problem o Family history of genetic disorder o Belongs to t high-risk category e.g. women over 35 have higher chance of fetus having Down’s syndrome In deciding to proceed with these tests, the element of risk will be assessed as will the decisions the individuals concerned are likely to make if a test is positive Diagnostic tests use the fetus’s karyotype = picture of chromosome complement (chromosomes arranged in their matching pairs) Examples amniocentesis and chorionic villus sampling (CVS) Amniocentesis Done at ~14-16 weeks A needle removes a little amniotic fluid containing fetal cells These cells are then cultured, stained and examined Chromosome complement is photographed The chromosomes are then arranged in their matching pairs to give the karyotype Allows chromosomal abnormalities to be detected e.g. extra chromosome 21 = Down’s syndrome Some people may then decide to terminate the pregnancy Small risk associated with miscarriage = ~ 1 in 100 women Chorionic villus sampling (CVS) One advantage is that it can be done as early as 8 weeks = earlier than amniocentesis Fine tube is inserted through the vagina Takes a tiny sample of placental cells Karyotyping can be performed on the fetal cells immediately If there was something genetically wrong with the fetus many people find a termination at this stage less traumatic than at ~14-16 weeks with the amniocentesis However there is a slightly higher risk of miscarriages Rhesus antibody testing Generally mother show no immune response to their fetus If a Rhesus-negative woman is pregnant with a Rhesus-positive fetus this can cause huge problems The Rhesus antigens on the fetus’s red blood cells are recognised as foreign by the mother’s immune system if the cells come into contact e.g. during birth = the mother is said to have been ‘sensitised’ The mother would produce antibodies against the antigen and retain some of the immune cells involved as memory cells If the woman was to get pregnant with another Rhesus-positive fetus she would mount an immune response against the antigen = the memory cells would produce antibodies which could cross the placenta and attack the fetus After the first birth the mother is given antiRhesus antibodies = these destroy any Rhesus antigens left behind by the baby before the mothers immune system has time to respond If a woman is Rhesus-negative it is detected very early in the pregnancy so that these measures can be put in place Post-natal (after birth) Diagnostic testing for metabolic disorders Test for PKU = phenylketonuria Gene mutation that leads to the incorrect production of an enzyme in a metabolic pathway being produced Individuals who suffer from PKU cannot metabolise phenylalanine into tyrosine Suffers placed on a restricted diet = low in phenylalanine This is called an inborn error of metabolism Genetic screening and pedigree charts Pedigree charts are also known as family trees Shows the pattern of inheritance Gives information about a specific characteristic Most of the members genotypes can be deduced from the phenotypes Genetic counsellors can construct pedigree charts and counsel families who are worried about the risk/possibility of passing on an inherited genetic disorder (that exists in their family) to their children Patterns of inheritance Autosomal recessive inheritance Autosomes = chromosomes that are not sex chromosomes Trait expressed relatively rarely Trait skips generation Trait is expressed in some of the offspring of consanguineous marriage e.g. cousins Males and females are equally affected Geneticist can then deduce that o Sufferes of the trait are homozygous recessive o Non-sufferers are either homozygous dominant or heterozygous ex = cystic fibrosis Autosomal dominant inheritance Trait expressed in every generation Each person with the condition has a parent with the condition If a branch of the family tree doesn’t have the condition it doesn’t reappear in future generations Males and females are equally affected Geneticist can then deduce that o Non-sufferers are homozygous recessive o Sufferers are homozygous dominant or heterozygous ex = Huntington’s disease Autosomal incomplete dominance Fully expressed form of the disorder is relatively rare Partially expressed form of the disorder occurs more frequently Someone who has the fully expressed form has both parents suffering from the partially expressed form Males and females are equally affected Geneticist can then deduce that o Non-sufferers are homozygous for one incompletely dominant allele o Sufferers of the fully expressed form are homozygous for the other incompletely dominant allele o Sufferers of the partially expressed form are heterozygous for the two alleles ex = sickle-cell disease Sex-linked recessive trait Far more males affected than females Trait carried on the X chromosome An affected male cannot pass the condition onto his sons as he passes on the Y chromosome that doesn’t carry the trait If a mother is affected (it can happen rarely) or if the mother is a carrier she can pass the condition onto her son If an affected male and an unaffected female have a son and a daughter o Daughter will be a carrier o Male will be unaffected o The daughter may then go on to produce sons who are affected The geneticist can deduce that o Sufferers of the trait are homozygous recessive o Non-sufferers are homozygous dominant or heterozygous carrier females Cardiovascular system Blood circulates from the heart through the arteries to the capillaries, to the veins and back to the heart. There is a decrease in blood pressure as blood moves away from the heart Structure and function of blood vessels The lumen is the central cavity of a blood vessel The lumen is lined with a thin layer of epithelial cells = called the endothelium The endothelium lining the central lumen of blood vessels is surrounded by layers of tissue that differ between arteries, capillaries and veins Arteries Carry blood away from the heart Have a thick middle layer of muscle This middle layer of muscle is found in between an outer and inner layer of elastic fibres The elastic walls of the arteries stretch and recoil to accommodate the surge of blood after each contraction of the heart Have a narrow lumen Vasoconstriction and vasodilation o Arterioles are small arteries o The smooth muscle in the walls of arterioles can contract or relax to control blood flow, depending on the body’s needs at a particular time o During strenuous exercise arterioles that connect to the muscles working go through vasodilation = this increases blood flow to these muscles o Whereas the arterioles that connect to organs involved in digestion go through vasoconstriction = this reduces blood flow to these parts during this period of strenuous exercise Capillaries Allow exchange of substances with tissues Made of epithelium that is only one cell thick Have a muscle inner The wall along a Have a Have backflow Veins Carry blood back to the heart thin middle layer of between an outer and layer of elastic fibres is thinner as blood flows vein at low pressure wide lumen = reduces resistance of blood flow valves to prevent the of blood Exchange of materials Blood contains red blood cells, white blood cells, platelets all suspended in plasma Plasma is a yellow substance that contains many dissolved substances – glucose, amino acids, respiratory gases, plasma proteins etc. Blood arrives at the capillary bed from an arteriole = so the blood is at high pressure The blood is forced into the narrow capillary vessels and goes through pressure filtration Pressure filtration results in a lot of the plasma being squeezed out through the one cell thick epithelium This liquid is now called tissue fluid The difference between plasma and tissue fluid is that the tissue fluid contains little/no plasma proteins Tissue fluid has a high concentration of dissolved food molecules and dissolved oxygen which will diffuse from a high concentration in the tissue fluid to the low concentration in the tissue cells down the concentration gradient CO2 and other metabolic waste products will diffuse from a high concentration in the tissue cells to a low concentration in the tissue fluid to be excreted Most of the tissue fluid returns to the capillaries by osmosis = water moves from high water concentration (tissue fluid with no plasma proteins) to low water concentration (blood plasma rich in plasma proteins) CO2 and other metabolic waste products diffuse into the blood in the capillaries Lymphatic vessels absorb excess tissue fluid = this fluid is now called lymph The lymph fluid is then returned to the circulatory system by the lymphatic vessels Lymphatic system = specialised part of the cardiovascular system o Carries lymph fluid – collected all over the body o System of vessels that returns the lymph to the bloodstream o Disorders of lymphatic systems ex. Kwashiorkor and Elephantiasis Structure and function of the heart Structure 4 chambers 2 atria and 2 ventricles Deoxygenated blood is taken to the heart by 2 main veins called the venae cavae Blood enters the right atrium Flows through the atrio-ventricular (AV) valve to the right ventricle Blood is pumped through the semi-lunar (SL) valve into the pulmonary arteries to be taken to the lungs Oxygenated blood returns to the heart in the pulmonary veins Blood enters the left atrium Flows through the AV valve into the left ventricle Blood is pumped through the SL valve into the aorta (largest artery in the body) to be taken all over the body The left ventricle wall is thicker than the right ventricle wall as the left has to pump blood all round the body whereas the right only has to pump blood to the lungs AV and SL valves prevent backflow of blood Cardiac function The left and right ventricles pump the same volume of blood through the aorta and pulmonary artery Heart rate (pulse) (HR) Number of heartbeats per minute Stoke volume (SV) Volume of blood pumped out by each ventricle on contraction The stronger the contraction the greater the stoke volume Cardiac output (CO) The volume of blood pumped through each ventricle per minute is the cardiac output CO = HR x SV Cardiac cycle Is the pattern of contraction (systole) and relaxation (diastole) by the heart in one heartbeat Diastole Blood returning to the atria Volume of blood in atria increases This increases atrial pressure, the AV valves are pushed open and blood begins to enter the ventricles Atrial systole The right and left atria contract at the same time and pump blood into the ventricles through the open AV valves Ventricle systole The ventricles contract The AV valves close This increases pressure = pressure of blood in the ventricles is higher than the blood in the arteries The SL valves are pushed open Blood is pumped out of the hear and into the aorta and pulmonary arteries Diastole The higher pressure in the arteries closes the SL valves The next cardiac cycle begins AV and SL valves Responsible for the heart sounds heard with a stethoscope Cardiac conducting system The heartbeat originates in the heart itself but is regulated by both nervous and hormonal control The pacemaker and conducting system of the heart bring about the heartbeat The pacemaker is also known as the sino-atrial node (SAN) SAN is found in the wall of the right atrium SAN is made of autorhythmic cells The SAN sets the rate at which cardiac muscle cells contract It does this by emitting an electrical impulse that spreads out from the SAN through the atria, making them contract simultaneously = atrial systole Then travelling to the atrioventricular node (AVN) = found in the middle at the base between the two atria Then into a bundle of conducting fibres which branches into the left and right ventricle The stimulation of the conducting fibres by the impulse causes the simultaneous contraction of the ventricles = ventricular systole This cardiac conducting system ensures that ventricular systole occurs just after atrial systole = allows time for the ventricles to completely fill with blood before contracting These impulses generate currents that can be detected by an electrocardiogram (ECG) ECG See diagram of normal ECG pattern P wave shows the electrical impulse from the SAN spreading through the atria QRS complex shows the electrical impulse stimulating the AVN and passes down through the ventricles T wave shows the electrical recovery (relaxation) of the ventricles = happens towards the end of ventricular systole See diagram of atrial flutter The waves occur in the same way as the normal ECG however they occur much more rapidly See diagram of ventricular fibrillation Heart muscle cells contracting at different times = not coordinated If the heart doesn’t resume coordinated contraction the person will die See diagram of ventricular tachycardia Abnormal cells in ventrical walls act like pacemakers = causes the ventricles to beat rapidly and not in coordination with atria No P wave and QRS waves are not normal Emergency situations A defibrillator gives an electric shock to patients heart = can allow the muscle cells to start contracting in coordination again Regulation The medulla regulates the rate of the SAN It does this through two different parts of the autonomic nervous system (ANS) that act antagonistically = they have opposite effects on the heart Cardio-accelerator centre sends nerve impulses to the heart via a sympathetic accelerator nerve Impulses arriving at the SAN from the sympathetic nerve results in an increase in heart rate Due to the release of the neurotransmitter norepinephrine (noradrenaline) Cardio-inhibitor centre sends impulses to the heart via a slowing parasympathetic nerve Impulses arriving at the SAN from the parasympathetic nerve results in a decrease in heart rate Due to the release of the neurotransmitter acetylcholine The actual heart rate depends on part of the ANS exerts the greater influence Hormonal control During stress and exercise the sympathetic nervous system stimulates the adrenal gland to release the hormone epinephrine Epinephrine also Blood pressure Is the force exerted by the blood against the walls of blood vessels Measured using a sphygmomanometer in millimetres of mercury (mmHg) Blood pressure changes, in response to cardiac cycle, and its measurement Blood pressure is generated by the ventricles contracting This means blood pressure will be highest in arteries e.g. aorta and pulmonary artery Blood pressure changes in the aorta during the cardiac cycle As the heart goes through systole and diastole arterial pressure rises and falls During ventricular systole = blood pressure in the aorta rises e.g. 120 During ventricular diastole it drops e.g. 80 A typical reading for a young adult is 120/70 mmHg Hypertension = also called high blood pressure Usually ~ 140/90 mmHg Hypertension is a major risk factor for many diseases including coronary heart disease and strokes Risk factors of hypertension o Being overweight o Not exercising regularly o Eating a diet rich in fat/salt o Drinking too much alcohol o Continued stress Cardiovascular disease (CVD), diabetes and obesity Atherosclerosis Formation of plaques called atheromas These plaques form underneath the endothelium in the wall of an artery The plaques start of as fatty material = cholesterol As the plaques become larger fibrous material, calcium and more cholesterol are added Atheromas lead to o Diameter of the artery’s lumen is reduced o Blood flow to the capillary bed the artery supplies is reduced/restricted o Blood pressure increases When large atheromas become hardened by calcium this causes the artery wall to become thicker = which reduces elasticity This is also known as hardening of the arteries Atherosclerosis can lead to o Coronary heart disease (including angina) o Strokes o Heart attacks (myocardial infarctions) o Peripheral vascular disease Blood clotting Usually occurs to prevent blood loss at the site of a wound Damage of cells leads to blood clotting factors being released Prothrombin inactive enzyme present in plasma, is converted into the active form thrombin Thrombin promotes conversion of fibrinogen (soluble plasma protein) into threads of fibrin (insoluble protein) Fibrin threads are interwoven = this allows platelets to adhere and form a blood clot The wound is now sealed = scar tissue begins to be formed Thrombosis Formation of a blood clot (thrombus) in a vessel = see events above! This can happen if an atheroma enlarges to a point where it causes damage e.g. bursts through the endothelium Embolus Thrombus breaks loose = called an embolus Embolus is carried in the blood stream until it blocks a narrow vessel = this will cause blood flow to be extremely restricted or stopped altogether If this occurs in a coronary artery = coronary thrombosis This could then deprive part of the heart muscle of oxygen = leads to a myocardial infarction (heart attack) If a thrombus/embolus causes a blockage in an artery in the brain = leads to a stroke Stroke normally results in death of some of the tissues that are supplied by that artery due to oxygen deprivation Peripheral vascular disorders Peripheral arteries = any artery that is not the; aorta, coronary and carotid arteries When peripheral arteries have an atheroma and are narrowed Most commonly affects the legs Blood flow is restricted = leads to pain in leg muscles due to oxygen deprivation Deep vein thrombosis Also known as DVT Thrombus formed in a vein Most commonly in calf muscles Leads to swelling and pain Pulmonary embolism Embolus carried vena cava to the heart and subsequently to the lungs in the pulmonary artery Blocks a branch of the pulmonary artery in the lungs = pulmonary embolism Symptoms = chest pains, breathing difficulties and palpitations Treatment = antigoagulant If untreated can lead to collapse and sudden death Cholesterol Lipids are a huge group of organic compounds which include o Saturated and unsaturated fats o Steroids Cholesterol is produced by liver cells from saturated fats in the diet Cholesterol is extremely important as it’s a component of cell membranes and is a precursor for steroid synthesis Transport of cholesterol High-density lipoprotein (HDL) transports excess cholesterol from the body cells to the liver for elimination This prevents accumulation of cholesterol in the blood = prevents it from being taken into artery walls and contributing to atherosclerosis Low-density lipoprotein (LDL) transports cholesterol to body cells Most cells have LDL receptors that take LDL into the cell where it releases cholesterol Once a cell has sufficient cholesterol a negative feedback system inhibits the synthesis of new LDL receptors and LDL circulates in the blood where it may deposit cholesterol in the arteries forming atheromas A higher ratio of HDL to LDL will result in lower blood cholesterol and a reduced chance of atherosclerosis and CVD People who exercise regularly usually have a higher concentration of HDL in the blood and so have decreased risk of CVD A diet with saturated fat swapped for unsaturated fat and less fat in general may also result in a higher concentration of HDL Medicine Statins are prescribed drugs that can reduce blood cholesterol They inhibit an enzyme that is involved in the synthesis of cholesterol by liver cells Familial hypercholesterolaemia (FH) Inherited disorder = autosomal dominant Gene mutation that causes a decrease in number of LDL receptors or a change in LDL receptor structure so that it no longer functions LDL carrying cholesterol are unable to deposit cholesterol inside cells This causes a very high concentration of LDL-cholesterol in the blood If untreated large quantities of cholesterol are deposited inside artery walls in a young age This means individuals suffering from FH will be more likely to suffer from CVD at a much younger age than normal If FH runs in a family genetic screening can determine if they have inherited the gene mutation and start treatment Treatment = healthy lifestyle e.g. low fat diet and regular exercise AND medication e.g. statins Blood glucose levels and obesity Blood glucose levels Regulation Blood glucose concentration is regulated by insulin and glucagon = negative feedback Pancreatic receptors respond to high blood glucose levels by causing secretion of insulin Insulin activates the conversion of glucose to glycogen in the liver = decreasing blood glucose concentration Pancreatic receptors respond to low blood glucose levels by producing glucagon Glucagon activates the conversion of glycogen to glucose in the liver = increasing blood glucose concentration Adrenaline/epinephrine In exercise and fight or flight responses adrenal glands release adrenaline/epinephrine Adrenaline/epinephrine stimulates glucagon secretion and inhibits insulin secretion = increasing blood glucose concentration Diabetes A diabetic is unable to control their glucose concentration Can result in chronic elevation of blood glucose concentration Type 1 diabetes Usually occurs in childhood Person unable to produce insulin Can be treated with regular doses of insulin Type 2 diabetes Sometimes referred to as adult onset diabetes Usually develops later in life Occurs mainly in overweight individuals Person is able to produce insulin but their cells are less sensitive to it = sometimes referred to as insulin resistance This insulin resistance is linked to a decrease in the number of insulin receptors in the liver Leads to a failure to convert glucose to glycogen In both cases blood glucose concentration rise rapidly after a meal Kidneys are unable to cope resulting in glucose being lost in the urine Testing urine for glucose is often used as an indicator of diabetes The glucose tolerance test is used to diagnose diabetes The blood glucose levels of the individual are measured after fasting and two hours after drinking 250-300ml of glucose solution Vascular disease can be a chronic complication of diabetes = see next page Vascular disease Complication associated with diabetes Chronic elevation of blood glucose concentrations leads to the endothelium cells in blood vessels taking in more glucose than normal = damages the blood vessels This damage can then lead to atherosclerosis which can cause = CVD, stroke or peripheral vascular disease Small blood vessels damaged by elevated glucose concentrations may result in o Haemorrhage of blood vessels in the retina = the blood vessels burst and bleed o Renal failure o Peripheral nerve dysfunction Obesity Characterised by excess body fat in relation to lean body tissue (muscle) Is a major risk factor for cardiovascular disease, type 2 diabetes, kidney failure and osteoarthritis Body mass index = weight divided by height squared See table Limitations = if a person has an unusually high percentage of muscle e.g. a body builder they could be wrongly classified as obese if BMI was used To measure body fat accurately = measure body density Body density Can be measured in the following ways Densitometry Individuals are weighed in air and while submerged in a tank Researchers use formulas to estimate body volume, body density, and body fat percentage Fat is more buoyant (less dense) than water, so someone with high body fat will have a lower body density than someone with low body fat This method is typically only used in a research setting Skin-fold thickness Use a special calliper to measure the thickness of a “pinch” of skin and the fat beneath it in specific areas of the body e.g. back of upper arm Equations are used to predict body fat percentage based on these measurements Waste/hip ratio Is used to measure abdominal obesity It’s calculated by measuring the waist and the hip (at the widest diameter of the buttocks), and then dividing the waist measurement by the hip measurement This is used as distribution of fat is important in measuring health risks ‘Apple-shaped’ people = carry excess fat round their abdominal area ‘Pear-shaped’ people = carry excess fat round their hips ‘Apple-shaped’ people are at greater risk of type 2 diabetes and CVD than ‘pear-shaped’ people Bioelectrical impedance BIA equipment sends a small, imperceptible, safe electric current through the body, measuring the resistance The current faces more resistance passing through body fat than it does passing through lean body mass and water Equations are used to estimate body fat percentage and fat-free mass Causes of obesity and treatments Linked to genetic, physiological, environmental, metabolic and dietary factors Most common cause = diet rich in fat and sugar AND a decrease in physical activity The energy intake in the diet should limit fats and free sugars Fats have a high calorific value per gram Free sugars require no metabolic energy to be expended in their digestion Exercise increases energy expenditure and preserves lean tissue Exercise can help to reduce risk factors for CVD by o Keeping weight under control o Minimising stress o Reducing hypertension o Increasing HDL levels in the blood