topic 6 Flashcards

Question

mouth

Answer 1

- mechanical digestion of food by chewing and mixing with saliva (contains lubricants and enzymes)

Answer 2

- movement of food by peristalsis from the mouth to the stomach

Answer 3

- churning and mixing with secreted water + acid which kills foreign pathogens in food - initial stages of protein digestion

Answer 4

- digestion of lipids, carbs, proteins, nucleic acids - neutralisation of stomach acid - absorption of nutrients

Answer 5

secretion of lipase, amylase, and protease

Answer 6

secretion of surfactants in bile to break up liquid droplets

Answer 7

storage and regulated release of bile

Answer 8

- re-absorption of water - further digestion by symbiotic bacteria (especially of carbs) - formation and storage of faces

Answer 9

- serosa (outer coat) - muscle layers (longitudinal muscle and inside it circular muscle) - sub-mucosa (tissue layer containing blood and lymph vessels) - mucosa (lining of SI, with epithelium that absorbs nutrients)

Answer 10

Starch can exist in one of two forms – amylose (linear, only 1,4) or amylopectin (branched, 1,4+1,6) The digestion of starch is initiated by salivary amylase in the mouth and continued by pancreatic amylase in the intestines Amylase digests amylose into maltose subunits (disaccharide) and digests amylopectin into branched chains called dextrins (it cannot break 1,6 bonds) Both maltose and dextrin are digested by enzymes (maltase) which are fixed to the epithelial lining of the small intestine

Answer 11

via the hepatic portal vein; excess glucose is absorbed by liver cells and converted to glycogen for storage

Answer 12

convey blood at high pressure from the ventricles to the tissues of the body

Answer 13

muscle and elastic fibres

Answer 14

- tunica externa: tough outer layer of connective tissue - tunica media: thick layer containing smooth muscle and elastic fibres made of the protein elastin - tunica intima: a smooth endothelium forming the lining of the artery

Answer 15

to assist in maintaining blood pressure between pump cycles

Answer 16

the peak pressure reached in an artery

Answer 17

the minimum pressure inside an artery

Answer 18

1. systolic pressure pushes the wall of the artery outwards, widening the lumen and stretching elastic fibres in the wall, thus storing potential energy 2. at the end of each heartbeat the pressure in the arteries falls sufficiently for the stretched elastic fibres to squeeze the blood in the lumen. This mechanism saves energy and prevents the diastolic pressure from becoming too low.

Answer 19

VASOCONSTRICTION circular muscles in the wall form a ring so when they contract, the circumference is reduced and the lumen is narrowed, blood pressure increase

Answer 20

so that they can respond to various hormone and neural signals to control blood flow to downstream tissues

Answer 21

- larger than 10µm - relatively thick wall and narrow lumen - 3 - abundant - none

Answer 22

to allow exchange of materials between cells in tissues and the blood in the capillary

Answer 23

help to form a rigid arterial wall that is capable of withstanding the high blood pressure without rupturing

Answer 24

allow the arterial wall to stretch and expand upon the flow of a pulse through the lumen

Answer 25

tissues of the lens and cornea in the eye- these must be transparent

Answer 26

- very small diameter which allows passage of only a single red blood cell at a time (optimal exchange) - capillary wall is made of a single layer of cells to minimise the diffusion distance for permeable materials - surrounded by a basement membrane which is permeable to necessary materials - may contain pores to further aid in the transport of materials between tissue fluid and blood

Answer 27

plasma is the fluid in which blood cells are suspended; tissue fluid contains oxygen, glucose, and all other substances in blood plasma apart from large protein molecules which cannot pass through capillary wall

Answer 28

fluid flows between the cells in a tissue, allowing the cells to absorb useful substances and excrete waste products as the tissue fluid then re-enters the capillary network

Answer 29

- wall may be continuous (eg nervous tissue in blood-brain barrier) with endothelial cells held together by tight junctions to limit permeability of large molecules - In tissues specialised for absorption (e.g. intestines, kidneys), the capillary wall may be fenestrated (contains pores) - some capillaries are sinusoidal and have open spaces between cells and be permeable to large molecules and cells (e.g. in liver)

Answer 30

arterioles; capillaries; increased; slowly; venules; veins

Answer 31

1. blood flows through the capillaries very slowly and at a very low pressure in order to allow for maximal material exchange 2. The higher hydrostatic pressure at the arteriole end of the capillary forces material from the bloodstream into the tissue fluid 3. The lower hydrostatic pressure at the venule end of the capillary allows materials from the tissues to enter the bloodstream

Answer 32

to collect blood at low pressure from the tissues of the body and return it to the atria of the heart

Answer 33

- around 10µm - extremely thin wall - only one layer, tunica intimate which is an endothelium consisting of a single layer of very thin cells - none - none

Answer 34

it carries blood from stomach and intestines to liver, not back to the heart

Answer 35

- very wide lumen (relative to wall thickness) to maximise blood flow for more effective return - thin wall containing less muscle and elastic fibres as blood is flowing at a very low pressure - pressure is low so veins possess valves to prevent backflow and stop the blood from pooling at the lowest extremities

Answer 36

as they facilitate venous blood flow via periodic contractions; it would otherwise be difficult for the blood to move against the downward force of gravity

Answer 37

- if blood starts to go backwards, it gets caught in the flaps of the pocket valve, which will with blood, blocking the lumen of the vein - when blood flows towards the heart, it pushes the flaps to the sides of the vein so the pocket valve opens

Answer 38

- variable but much larger than 10 - relatively thin wall with variable but often wide lumen - three layers - small amounts - present in many veins

Answer 39

in humans there is a separate circulation for the lungs: - pulmonary circulation, to and from the lungs - systemic circulation, to and from all other organs including the heart muscles

Answer 40

blood capillaries in the lungs cannot withstand high pressures so blood is pumped to them at relatively low pressure; after passing through the lung capillaries, pressure is still low so blood must return to the heart to be pumped again before it goes to other organs

Answer 41

systole; diastole

Answer 42

the atria are contracting the ventricles are contracting

Answer 43

Atrial systole forces blood from the atria into the ventricles During ventricular systole, blood is forced from the ventricles into the pulmonary artery and aorta

Answer 44

1. the heart beat is initiated by a group of cells in the wall of the right atrium called the sinoatrial node (SAN) 2. the cells of the sinoatrial node depolarise, reversing the charge across their membranes 3. Depolarisation of the cells in the sinoatrial node sends an electrical signal over the atria, causing them to contract in atrial systole 4. The electrical signal then reaches a region of non-conducting tissue which prevents it from spreading straight to the ventricles; this causes the signal to pause for around 0.1 s This delay means that the atria can complete their contraction before the ventricles begin to contract 5. The electrical signal is carried to the ventricles via the atrioventricular node (AVN), a region of conducting tissue between atria and ventricles 6. The signal then travels to the base of the heart via conductive fibres in the septum known as the bundle of His 7. it is then carried through conductive fibres called Purkyne fibres which spread around the sides of the ventricles, causing contraction of the ventricles from the apex, or base, of the heart upwards 8. Blood is forced out of the heart into the pulmonary artery and aorta

Answer 45

because it initiates the heart beat and so controls the speed at which the heart beats

Answer 46

it will beat without any external stimulus from other organs or the nervous system

Answer 47

with signals from branches of two nerves originating in the cardiovascular centre, a region in the medulla of the brain - signals from one of the nerves cause the pacemaker to increase the frequency of heartbeats - signals from the other decrease the rate

Answer 48

the heart rate needs to speed up to increase the flow rate of blood to the tissues, deliver more oxygen and remove more CO2 the heart rate may need to slow down

Answer 49

controlled by the brain, and increases the heart rate to prepare for vigorous physical activity because of a threat/opportunity

Answer 50

the sinoatrial node

Answer 51

- demonstrated blood flow through larger vessels is unidirectional, with valves to prevent back flow - showed the rate of flow through major vessels is too high for blood to be consumed in the body after being pumped out by the heart; it must therefore return to the heart and be recycled - showed the heart pumps blood out in arteries and returns it in veins - predicted presence of numerous fine vessels

Answer 52

1. Low density lipoproteins (LDL) containing fats and cholesterol accumulate in the artery wall of the coronary artery. 2. phagocytes are then attracted by signals from endothelium cells and smooth muscle. The phagocytes engulf the fats and cholesterol by endocytosis and grow very large. 3. Smooth muscle cells migrate to form a tough cap over the atheroma. The artery wall bulges into the lumen narrowing it and thus impeding blood flow.

Answer 53

Coronary occlusion is a narrowing of the arteries that supply blood containing oxygen and nutrients to the heart muscle. Lack of oxygen (anoxia) causes pain, known as angina, and impairs the muscle's ability to contract, so the heart beats faster as it tries to maintain blood circulation with some of its muscle out of action. The fibrous cap covering atheromas sometimes ruptures, which stimulates the formation of blood clots that can block arteries supplying blood to the heart and cause acute heart problems.

Answer 54

- high blood concentrations of LDL (low density lipoprotein) - chronic high blood glucose concentrations, due to overeating, obesity or diabetes - chronic high blood pressure due to smoking, stress or any other cause - consumption of trans fats, which damage the endothelium of the artery. - infection of the artery wall with Chlamydia pneumoniae - production of trimethylamine N-oxide (TMAO) by microbes in the intestine.

Answer 55

the development of an atheroma - plaque, or fatty tissue that blocks arteries

Answer 56

0.0-0.1 seconds The atria contract causing a rapid but relatively small pressure increase, which pumps blood from the atria to the ventricles, through the open atrioventricular valves. The semilunar valves are closed and blood pressure in the arteries gradually drops to its minimum as blood continues to flow along them but no more is pumped in. 0.1-0.15 seconds The ventricles contract, with a rapid pressure build up that causes the atrioventricular valves to close. The semilunar valves remain closed. 0.15-0.4 seconds The pressure in the ventricles rises above the pressure in the arteries so the semilunar valves open and blood is pumped from the ventricles into the arteries, transiently maximizing the arterial blood pressure. Pressure slowly rises in the atria as blood drains into them from the veins and they fill. 0.4-0.45 seconds The contraction of the ventricular muscles wanes and pressure inside the ventricles rapidly drops below the pressure in the arteries, causing the semilunar valves to close. The atrioventricular valves remain closed. 0.45-0.8 seconds Pressure in the ventricles drops below the pressure in the atria so the atrioventricular valves open. Blood from the veins drains into the atria and from there into the ventricles, causing a slow increase in pressure.

Answer 57

the skin and mucous membranes form a primary defence mechanism against pathogens that cause infectious disease

Answer 58

- outermost layer is tough and provides a physical barrier against the entry of pathogens and physical/chemical damage - sebaceous glands are associated with hair follicles and secrete sebum, which maintains skin moisture and slightly lowering skin pH, which inhibits the growth of bacteria and fungi

Answer 59

thinner and softer type of skin found in airways and reproductive organs - the mucus secreted is a sticky solution of glycoproteins and traps pathogens, which are either swallowed or expelled, acting as a physical barrier - also has antiseptic properties due to the presence of the anti-bacterial enzyme lysozyme

Answer 60

1. platelets aggregate at the site forming a temporary plug 2. they release clotting factors that trigger off the cascade of reactions involved in the clotting process 3. this cascade results in the production of thrombin, an enzyme, which converts the soluble protein fibrinogen into the insoluble fibrin 4. the resulting clot is initially a gel but if exposed to the air dries to form a hard scab

Answer 61

- ingestion of pathogens by phagocytic white blood cells gives non-specific immunity to diseases - they engulf of pathogens by endocytosis and digest them with lysosomes (enzymes)

Answer 62

Production of antibodies by lymphocytes in response to particular pathogens gives specific immunity

Answer 63

any chemical that stimulates an immune response

Answer 64

- the production of one type of antibodies specific to a particular pathogen's antigens by lymphocytes

Answer 65

1. antigens on the pathogen stimulate cell division of the small group of lymphocytes that produce the appropriate antibody 2. plasma cells (large clones of lymphocytes) are produced within a few days and secrete large quantities of the antibody

Answer 66

antibodies are large proteins that have two functional regions: a hyper variable region that binds to a specific antigen and another that helps the body fight the pathogen by - making it more recognisable to phagocytes - preventing viruses from docking to and entering host cells

Answer 67

memory cells

Answer 68

either having antibodies against the pathogens or memory cells that allow rapid production of the antibody

Answer 69

block processes that occur in prokaryotic cells but not eukaryotic cells. For example, bacterial DNA replication, transcription, translation, ribosome function and cell wall formation.

Answer 70

some strains of bacteria have evolved with genes which confer resistance to antibiotics and some strains have multiple resistance

Answer 71

Being non-living, they rely on the host cell's enzymes for ATP synthesis and other metabolic pathways. These processes cannot be targeted by drugs as the host cell would also be damaged.

Answer 72

the formation of blood clots in the coronary arteries - this can be a fatal condition.

Answer 73

coronary occlusion, damage to the capillary epithelium, hardening of the arteries, rupture of an atheroma

Answer 74

Production of antibodies by the immune system is a complex process and includes different types of lymphocyte, including helper T-cells. The human immunodeficiency virus (HIV) invades and destroys helper T-cells. The consequence is a progressive loss of the capacity to produce antibodies. In the early stages of infection, the immune system makes antibodies against HIV. If these can be detected in a person's body, they are said to be HIV-positive. HIV is a retrovirus that has genes made of RNA and uses reverse transcriptase to make DNA copies of its genes once it has entered a host cell. The rate at which helper T-cells are destroyed by HIV varies considerably and can be slowed down by using anti-retroviral drugs. In most HIV-positive patients antibody production eventually becomes so ineffective that a group of opportunistic infections strike, which would be easily fought off by a healthy immune system. A collection of several diseases or conditions existing together is called a syndrome. When the syndrome of conditions due to HIV is present, the person is said to have acquired immune deficiency syndrome (AIDS). AIDS spreads by HIV infection. The virus only survives outside the body for a short time and infection normally only occurs if there is blood to blood contact between infected and uninfected people. There are various ways in which this can occur: - sexual intercourse, during which abrasions to the mucous membranes of the penis and vagina can cause minor bleeding - transfusion of infected blood, or blood products such as Factor VIII - sharing of hypodermic needles by intravenous drug users.

Answer 75

Florey and Chain tested penicillin on infected mice Eight mice were injected with hemolytic streptococci and four of these mice were subsequently injected with doses of penicillin The untreated mice died of bacterial infection while those treated with penicillin all survived – demonstrating its antibiotic potential

Answer 76

it maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries

Answer 77

pg311 - type 1 pneumocystis in alveolus walls - phagocyte - network of blood capillaries - type 2 pneumocystis in alveolus walls

Answer 78

1. ventilation rate - observation of number of times air is exhaled and inhaled in a minute - data logging with inflatable chest belt that is placed around the thorax 2. tidal volume - one normal breath is exhaled through a delivery tube into a vessel and the volume is measured. it is not safe to use this apparatus for repeatedly inhaling/exhaling air as the co2 concentration will rise too high - spirometers measure flow rate into and out of lungs and from these measurements lung volumes can be deduced

Answer 79

extremely thin alveolar cells that are adapted to carry out gas exchange - located in epithelium, in wall of alveolus - flattened cells - distance over which co2 and o2 have to diffuse is very small, which increases the rate of gas exchange

Answer 80

secrete a solution containing surfactant that creates a moist surface: - allows oxygen to dissolve and diffuse to blood - provides area from which co2 can evaporate into the air and be exhaled hydrophobic heads face the water and the hydrophobic tails face the air: - reduces surface tension and prevents water from causing the sides of the alveoli to adhere when air is exhaled from lungs, helping prevent the collapse of the lung

Answer 81

nose/mouth -> trachea -> two bronchi -> lung -> tree-like bronchioles -> groups of alveoli

Answer 82

rings of cartilage in their walls to keep it open even when air pressure inside is low or pressure in surrounding tissues is high

Answer 83

smooth muscle fibres in their walls, allowing the width of these airways to vary

Answer 84

- ribs upwards and outwards - air in - diaphragm down

Answer 85

- ribcage inwards and downwards - air out - diaphragm up

Answer 86

- if particles of gas spread out to occupy a larger volume, the pressure of gas becomes lower - if gas is compressed to occupy a smaller volume, the pressure rises - if gas is free to move, it will flow from regions of higher pressure to regions of lower pressure

Answer 87

1. muscle contractions cause pressure inside the thorax to drop below atmospheric pressure 2. air is drawn into the lungs from the atmosphere (inspiration) until lung pressure has risen to atmospheric pressure 3. muscle contractions then cause pressure inside the thorax to rise above atmospheric, so air is forced out from the lungs to the atmosphere (expiration)

Answer 88

contracting and relaxing

Answer 89

- muscles do work - exert a pulling force (tension) that causes a particular movement - become shorter

Answer 90

- muscles lengthen passively - pulled into an elongated state by the contraction of another muscle - do not exert a pushing force (compression) while relaxing so do no work

Answer 91

when one muscle contracts and causes a movement the second muscle relaxes and is elongated by the first . the opposite movement is caused by the second muscle contracting while the first relaxes

Answer 92

muscles can only cause movement in one direction. if movement in opposite directions is needed at different timed, at least two muscles will be required

Answer 93

- smoking: tobacco contains many mutagenic chemicals. - passive smoking - air pollution from diesel exhaust fumes, nitrogen oxides from all vehicle exhaust fumes, smoke from burning coal, wood, or other organic matter - radon gas: radioactive gas that leaks out of rocks like granite. accumulates in badly ventilated buildings so people inhale it - asbestos, silica, some other solids if dust or particles of them are inhaled, in construction sites, quarries, mines, or factories

Answer 94

- difficulties with breathing, persistent coughing, coughing up blood, chest pain, loss of appetite, weight loss, general fatigue - may lead to secondary tumours - chemotherapy or radiotherapy

Answer 95

Emphysema is a lung condition whereby the walls of the alveoli lose their elasticity due to damage to the alveolar walls - The loss of elasticity results in the abnormal enlargement of the alveoli, leading to a lower total surface area for gas exchange - The degradation of the alveolar walls can cause holes to develop and alveoli to merge into huge air spaces (pulmonary bullae)

Answer 96

in smokers, the number of phagocytes in the lungs increases and they produce more elastase. - phagocytes inside alveoli normally prevent lung infections by engulfing bacteria and produce elastase, a protein-digesting enzyme, to kill them inside the vesicles formed by endocytosis. - alpha 1-antitrypsin (A1AT) is an enzyme inhibitor and prevents elastase and other proteases from digesting lung tissue. - genetic factors affect the quantity and effectiveness of A1AT produced in the lungs

Answer 97

- irreversible, chronic disease - low oxygen saturation in the blood and higher than normal co2 concentrations. - patient lacks energy - shortness of breath - ventilation laboured and more rapid than usual

Answer 98

volume in thorax increases and pressure consequently decreases volume in thorax decreases and pressure consequently increases

Answer 99

inspiration: - diaphragm contracts and so it moves downwards and pushes the abdomen wall out - muscles in the abdomen wall relax allowing pressure from the diaphragm to push it out expiration: - diaphragm relaxes so it can be pushed upwards into a more domed shape - muscles in the abdomen wall contract pushing the abdominal organs and diaphragm upwards

Answer 100

inspiration: - the external intercostal muscles contract, pulling the ribcage upwards and outwards - internal intercostal muscles relax and are pulled back into their elongated state expiration: - external intercostal muscles relax and are pulled back into their elongated state - internal intercostal muscles contract, pulling the ribcage inwards and downwards

Answer 101

endocrine system consists of glands that release hormones; nervous system consists of nerve cells called neurone

Answer 102

to transmit electrical impulses

Answer 103

short branched nerve fibres, for example those used to transmit impulses between neurone in one part of the brain or spinal cord

Answer 104

very elongated nerve fibres, for example those that transmit impulses from the fingers to the spinal cord

Answer 105

they are myelinated, which allows for saltatory conduction

Answer 106

in myelinated nerve fibres the nerve impulse can jump from one node of ranvier to the next

Answer 107

- consists of many layers of phospholipid bilayer - deposited by Schwann cells, which grow round and round the nerve fibre

Answer 108

gap between the myelin deposited by adjacent Schwann cells.

Answer 109

action potential to be conducted much faster and prevents the loss of the electrical signal through the cell membrane.

Answer 110

the potential difference or voltage across the membrane of a neuron that is not transmitting a signal

Answer 111

due to the imbalance of positive and negative charges across the membrane

Answer 112

- sodium-potassium pumps transfer sodium and potassium ions across the membrane. Na+ ions pumped out and K+ ions pumped in. The number of ions pumped is unequal - when 3 Na+ ions are pumped out, only two K+ ions are pumped in, creating concentration gradients for both ions - the membrane is about 50x more permeable to K+ ions than Na+ ions, so K+ ions leak back across the membrane faster than Na+ ions. As a result, the Na+ concentration gradient across the membrane is steeper than the K+ gradient, creating a charge imbalance - there are proteins inside the nerve fibre that are negatively charged (organic anions) which increase the charge imbalance

Answer 113

a rapid change in membrane potential, consisting of: - depolarisation - a change from negative to positive - repolarisation - a change back from positive to negative

Answer 114

due to the opening of sodium channels in the membrane, allowing Na+ ions to diffuse into the neuron down the concentration gradient. The entry of Na+ ions reverses the charge imbalance across the membrane, so the inside is positive relative to the outside. This raises the membrane potential to a positive value of about +30mV

Answer 115

happens rapidly after depolarisation and is due to the closing of the sodium channel and the opening of potassium channels in the membrane. This allows K+ ions to diffuse out of the neuron, down their concentration gradient, which makes the inside of the cell negative again relative to the outside. The potassium channels remain open until the membrane has fallen to a potential close to -70mV

Answer 116

the diffusion of potassium depolarises the neuron, but does not restore the resting potential as the concentration gradients of sodium and potassium ions have not yet been re-established.

Answer 117

action potentials propagated along the axons of neutrons

Answer 118

because the sodium ion movements that depolarise one part of the neutron trigger depolarisation in the neighbouring part of the neuron

Answer 119

prevents propagation of an action potential backwards along an axon

Answer 120

1. depolarisation of part of the axon reduces the concentration of sodium ions outside the axon and increases it inside 2. depolarised part of the axon therefore has different sodium ion concentrations to the neighbouring part of the axon that has not yet depolarised 3. inside the axon sodium ions diffuse along inside the axon to the neighbouring part that is still polarised 4. outside the axon the sodium ions diffuse from the polarised part back to the part that has just depolarised

Answer 121

reduce the concentration gradient in the part of the neuron that has not yet depolarised. this makes the membrane potential rise from the resting potential of -70mV to about -50mV. sodium channels in the axon membrane are voltage-gated and open when a membrane potential of -50mV is reached (known as threshold potential). this causes depolarisation

Answer 122

a junction between neurons and between neurone and receptor or effector cells

Answer 123

a neurotransmitter into the synapse

Answer 124

1. a nerve impulse is propagated along the pre-synaptic neuron until it reaches the end of the neuron and the pre-synaptic membrane 2. depolarization of the pre-synaptic membrane causes calcium ions (Ca2+) to diffuse through channels in the membrane into the neuron 3. influx of calcium causes vesicles containing neurotransmitter to move to the pre-synaptic membrane and fuse with it 4. neurotransmitter is released into the synaptic cleft by exocytosis 5. the neurotransmitter diffuses across the synaptic cleft and binds to receptors on the post-synaptic membrane 6. the binding of the neurotransmitter to the receptors causes adjacent sodium ion channels to open 7. sodium ions diffuse down their concentration gradient into the post-synaptic neuron, causing the post-synaptic membrane to reach the threshold potential 8. an action potential is triggered in the post-synaptic membrane and is propagated on along the neuron 9. the neurotransmitter is rapidly broken down and removed from the synaptic cleft

Answer 125

used as the neurotransmitter in many synapses

Answer 126

in the presynaptic neuron by combining choline, absorbed from the diet, with an acetyl group produced during aerobic respiration

Answer 127

- loaded into vesicles and then released into the synaptic cleft during synaptic transmission - receptors for acetylcholine in the post-synaptic membrane have a binding site to which acetylcholine will bind - acetylcholine only remains bound to receptor for a short time, during which only one action potential is initiated in the post-synaptic neuron - enzyme acetylcholinesterase is present in the cleft and rapidly breaks down acetylcholine down into choline and acetate - choline reabsorbed into pre-synaptic neuron, where it is converted back into active neurotransmitter by recombining it with an acetyl group

Answer 128

insecticides: - they bind to the acetylcholine receptor in cholinergic synapses in the CNS of insects - acetylcholinesterase does not break them down, so binding is irreversible - receptors blocked so acetylcholine is unable to bind and synaptic transmission is prevented - results in insect paralysis and death

Answer 129

+ not highly toxic to humans and other mammals: greater proportion of synapses in CNS are cholinergic in insects than in mammals and neonicotinoids bind less strongly to acetylcholine receptors in mammals than insects - effects on honeybees and other beneficial insects

Answer 130

the threshold potential is reached

Answer 131

all or nothing principle; only at the threshold potential do voltage-gated sodium channels start to open, causing depolarisation

Answer 132

the amount of neurotransmitter secreted following depolarisation of the pre-synaptic membrane may not be enough to cause the threshold potential to be reached in the post-synaptic membrane, which then does not depolarise.

Answer 133

sodium ions that have entered the post-synaptic neuron are pumped out by sodium-potassium pumps and the post-synaptic membrane returns to the resting potential

Answer 134

- a typical post-synaptic neuron in the brain or spinal cord has synapses with many pre-synaptic neurone - it may be necessary for several of these to release neurotransmitter at the same time for the threshold potential to be reached and nerve impulse to be initiated

Answer 135

to respond to changes in blood glucose levels

Answer 136

small regions of endocrine tissue islets of Langerhans

Answer 137

synthesise and secrete glucagon if blood glucose levels fall below set point.

Answer 138

stimulates breakdown of glycogen into glucose in liver cells and its release into the blood, increasing the concentration

Answer 139

synthesise insulin and secrete it when the blood glucose concentration rises above the set point

Answer 140

stimulates uptake of glucose by various tissues, particularly skeletal muscle and liver, in which it also stimulates conversion of glucose to glycogen, reducing blood glucose concentration

Answer 141

it is broken down by the cells it acts upon

Answer 142

a condition where a person has consistently elevated blood glucose levels

Answer 143

- damages tissues, particularly their proteins - impairs water reabsorption from urine while it is forming in the kidney, resulting in an increase in the volume of urine and body dehydration

Answer 144

- urinate more frequently - constantly thirsty - feels tired - cares sugary drinks

Answer 145

- characterised by an inability to produce sufficient quantities of insulin - autoimmune disease arising from the destruction of beta cells in the islets of Langerhans by the body's own immune system

Answer 146

- characterised by an inability to process or respond to insulin because of a deficiency of insulin receptors or glucose transporters on target cells

Answer 147

- sugary, fatty diets - prolonged obesity due to habitual obesity and lack of exercise - genetic factors that affect energy metabolism

Answer 148

- testing blood glucose concentration regularly and injecting insulin when it is too high or likely to become too high - injections often done before a meal to prevent peak of blood glucose as the food is digested/absorbed

Answer 149

- adjusting diet to reduce peaks and troughs of blood glucose. - small amounts of food eaten frequently rather than infrequent large meals - foods with high sugar content avoided; starchy foods only allowed if low glycemic index (digested slowly); high-fibre foods included to slow digestion of other foods - strenuous exercise and weight loss

Answer 150

thyroid gland (in neck) §

Answer 151

- chemical structure - contains four atoms of iodine - almost all cells in body are targets

Answer 152

prolonged deficiency of iodine in the diet

Answer 153

- regulates body's metabolic rate, so all cells need to respond - main targets are most metabolically active such as liver, muscle and brain - control of body temperature

Answer 154

more protein synthesis and growth and increases the generation of body heat

Answer 155

increased thyroxin secretion by the thyroid gland, which stimulates heat production so body temperature rises

Answer 156

thyroxin deficiency: - lack of energy/persistent tiredness - forgetfulness and depression - weight gain - persistent feeling cold - constipation - impaired brain development

Answer 157

less glucose and fat are being broken down to release energy by cell respiration

Answer 158

contractions of muscle in the wall of the gut slow down

Answer 159

a protein hormone secreted by adipose cells (fat storage cells)

Answer 160

food intake and amount of adipose tissue in the body

Answer 161

group of cells in the hypothalamus of the brain that contribute to the control of appetite - leptin binds to receptors in the membrane of these cells.

Answer 162

blood leptin concentrations rise, causing long-term appetite inhibition and reduced food intake

Answer 163

- they had two copies of recessive allele, ob, causing their adipose cells to be unable to produce leptin - feed ravenously, become inactive and gain body weight, mainly through increased adipose tissue - when these mice were injected with leptin their appetite declined, energy expenditure increased, and body mass dropped

Answer 164

- in contrast to ob/ob mice, most obese humans have exceptionally high blood leptin concentrations - target cells in hypothalamus have become resistant to leptin so fail to respond to it, even at high concentrations - appetite not inhibited and food intake is excessive - more adipose tissue develops, causing a rise in blood leptin concentration but leptin resistance prevents inhibition of appetite

Answer 165

mutations in the genes for leptin synthesis or its various receptors on target cells

Answer 166

significant weight loss while the leptin injections are continuing; however, leptin is a short lived protein and has to be injected several times a day. also affects the development and functioning of the reproductive system, so is not suitable to children and YAs

Answer 167

humans are adapted to live in a 24-hour cycle and have rhythms in behaviour that fit this cycle

Answer 168

two groups of cells in the hypothalamus - suprachiasmatic nuclei (SCN).

Answer 169

control secretion of melatonin (hormone) by pineal gland.

Answer 170

increases in the evening and drops to a low level at dawn

Answer 171

the hormone is rapidly removed from the blood by the liver

Answer 172

- the sleep-wake cycle: high levels of melatonin cause drowsiness and promote sleep through the night. falling levels encourage waking at the end of the night - night-time drop in core body temperature - decreased urine production at night: melatonin receptors have been discovered in the kidney

Answer 173

a special type of ganglion cell in the retina of the eye detects light of wavelength 460-480nm and passes impulses to cells in the SCN. This indicates to the SCN the timing of dusk and dawn and allows it to adjust melatonin secretion so that it corresponds to the day-night cycle.

Answer 174

the SCN and pineal gland are continuing to set a circadian rhythm to suit the timing of day and night at the point of departure rather than destination.

Answer 175

the same in all embryos and embryonic gonads develop that could either become ovaries or testes

Answer 176

the presence or absence of one gene

Answer 177

the embryonic gonads develop into testes.

Answer 178

it codes for a DNA binding protein called TDF (testis determining factor(, which stimulates the expression of other genes that cause testis development

Answer 179

on the Y chromosome

Answer 180

when embryos have 2 X chromosomes and so do not have a copy of the SRY gene. TDF is not produced and the embryonic gonads develop as ovaries

Answer 181

in about the eighth week of pregnancy

Answer 182

testosterone-secreting cells testosterone

Answer 183

the secretion of testosterone increases

Answer 184

- sperm production in the testes (primary sexual characteristic of males) - secondary sexual characteristics: enlargement of the penis, growth of pubic hair, deepening of voice due to growth of the larynx

Answer 185

- estrogen and progesterone are always present in pregnancy - at first they are secreted by the mother's ovaries and later by the placenta - in the absence of fetal testosterone and the presence of maternal oestrogen and progesterone, female reproductive organs develop

Answer 186

- female secondary secondary sexual characteristics: enlargement of the breasts, growth of pubic and underarm hair

Answer 187

produce sperm and testosterone

Answer 188

hold testes at lower than core body temperature

Answer 189

store sperm until ejaculation

Answer 190

secrete fluid containing alkali, proteins and fructose that is added to sperm to make semen

Answer 191

transfer seen during ejaculation and urine during urination

Answer 192

penetrates the vagina for ejaculation of semen near the cervix

Answer 193

produce eggs, oestrogen, and progesterone

Answer 194

collect eggs at ovulation, provide a site for fertilisation then move the embryo to the uterus

Answer 195

provide the needs of the embryo and then foetus during pregnancy

Answer 196

protect the foetus during pregnancy and then dilate to provide a birth canal

Answer 197

stimulate the penis to cause ejaculation and provide a birth canal

Answer 198

protect internal parts of the female reproductive system

Answer 199

negative and positive feedback mechanisms involving ovarian and pituitary hormones

Answer 200

follicular phase luteal phase

Answer 201

- a group of follicles is developing in the ovary - in each follicle an egg is stimulated to grow - at the same time the lining of the uterus (endometrium) is repaired and starts to thicken - the most developed follicle breaks open, releasing its eggs into the oviduct - the other follicles degenerate

Answer 202

- the wall of the follicle that released an egg becomes the corpus luteum - continued development of the endometrium prepares it for the implantation of an embryo - if fertilisation does not occur the corpus lute in the ovary breaks down - the thickening of the endometrium in the uterus also breaks down and is shed during menstruation

Answer 203

protein hormones produced by the pituitary gland that bind to FSH and LH receptors in the membranes of follicle cells

Answer 204

ovarian hormones produced by the wall of the follicle and corpus lute. they are absorbed by many cells in the female body, where they influence gene expression and therefore development

Answer 205

rises to a peak towards the end of the menstrual cycle - stimulates the development of follicles, each containing an oocyte and follicular fluid - stimulates the secretion of oestrogen by the follicle wall

Answer 206

rises to a peak towards the end of the follicular phase - stimulates repair and thickening of the endometrium after menstruation and an increase in FSH receptors that make the follicles more receptive to FSH, boosting oestrogen production (positive feedback) - at high levels, oestrogen inhibits FSH secretion (negative feedback) and stimulates LH secretion

Answer 207

rises to a sudden and sharp peak towards the end of the follicular phase - stimulates the completion of meiosis in the oocyte and partial digestion of the follicle wall allowing it to burst open at ovulation - LH promotes development of wall of follicle after ovulation into corpus luteum, which secretes oestrogen (positive feedback) and progesterone

Answer 208

rise at the start of the luteal phase, reach a peak and then drop back to a low level by the end of this phase - promotes thickening and maintenance of endometrium - inhibits FSH and LH secretion by pituitary gland

Answer 209

1. down-regulation: woman takes a drug each day (usually nasal spray) to stop her pituitary gland secreting FSH or LH. secretion of oestrogen and progesterone therefore also stops. menstrual cycle suspended and doctors can control timing and amount of egg production in woman's ovaries 2. superovulation- intramuscular injections of FSH and LH given daily for ~10 days, to stimulate follicles to develop. FSH injections are of higher concentration than usual so far more follicles develop than usual. 3. injection of HCG- stimulates follicles to mature 4. micropipette mounted on an ultrasound scanner is passed through uterus wall to wash eggs out of the follicles 5. each egg is mixed with 50-100,000 sperm cells in sterile conditions in a shallow dish, which is then incubated at 37'C until the next day 6. if fertilisation occurs then one or more embryos are placed in the uterus when they are ~48 hours old 7. extra progesterone usually given as a tablet placed inside vagina, to ensure uterus lining is maintained

topic 6 Flashcards

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