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Saturday, February 29, 2020

Biology Aqa

16. 8 – Genetic fingerprinting43 Section 9. 1 – Sensory Reception †¢ A stimulus is a detectable change in the internal or external environment of an organism that produces a response. The ability to respond to a stimulus increases an organism’s chances of survival. †¢ Receptors transfer the energy of a stimulus into a form that can be processed by the organism and leads to a response. †¢ The response is carried out by â€Å"effectors† which can include cells, tissues, organs and systems. Taxis – A simple response that’s direction is determined by the direction of the stimulus An organism can respond directly to a change in the environment by moving its body either: 1. Toward the stimulus (positive taxis) 2. Away from the stimulus (negative taxis) Kinesis – Results in an increase of random movements †¢ Organism does not move towards/away from the stimulus †¢ The more intense the stimulus the more rapid the movements †¢ Kinesis is important when the stimulus is less directional such as heat or humidity Tropism – a growth movement of part of a plant in response to a directional stimulus Positive phototropism – shoots/leaves Positive Geotropism – roots Section 9. 2 – Nervous Control Nervous organisation The nervous system can be thought of as having two main divisions: . The central nervous system (CNS) – brain and spinal cord 2. The peripheral nervous system (PNS) – Made up of pairs of nerves that originate either from the brain or the spinal cord The peripheral nervous system This is divided into: †¢ Sensory neurons which carry impulses away from receptors to the CNS †¢ Motor neurons which carry nervous impulses from the CNS to effectors The spinal cord is a column of nervous tissue A reflex – involuntary response to a stimulus (you do stop to consider an alternative) The pathway of neurons involved in a reflex is called a reflex arc. Reflex arcs contain just 3 neurons: 1. A sensory neuron 2. An intermediate neuron 3. A motor neuron There are several stages of a reflex arc: 1. Stimulus 2. Receptor 3. Sensory neuron 4. Synapse 5. Coordinator (intermediate neuron) 6. Synapse 7. Motor neuron 8. Effecter 9. Response Importance of the reflex arc †¢ Involuntary – does not require the decision making power of the brains †¢ Brain can override the response if necessary †¢ Protects the body from harmful stimuli Effective from birth – does not need to be learnt †¢ Short pathway – fewer synapses Synapses – slow Neurons – fast Section 9. 3 – Control of heart rate The Autonomic nervous system Controls subconscious activities of muscles and glands Has two main divisions: The sympathetic nervous system – Speeds up activities and thus allows us to cope with stressful situations (fight or flight r esponse) The parasympathetic nervous system – Inhibits effects and slows down activities. This allows energy to be conserved. Controls under normal resting conditions The two divisions are antagonistic meaning that their effects oppose one another Control of heart rate Changes of the heart rate are controlled by a region of the brain called the medulla oblongata which has two main divisions One division is connected to the sinoatrial node through the sympathetic nervous system The other is connected to the sinoatrial node via the parasympathetic nervous system Control by chemoreceptors Chemoreceptors are found in the wall of the carotid arteries and detect hanges in pH as a result of CO2 concentration When CO2 concentration in the blood is too low, chemoreceptors detect the drop in pH and send impulses to the section of the medulla oblongata responsible for increasing heart rate This section then increases the number of impulses sent to the S. A node via the sympathetic nervous system This results in an increase in heart rate which then causes blood pH to return to normal. Control by pressure receptors Pressure receptors occur in the wall of the carotid arteries and the aorta When blood pressure is too high – impulses are sent to the medulla oblongata which then sends impulses to the S. A node via the parasympathetic nervous system decreasing the heart rate When blood pressure is too low – impulses are sent to the medulla oblongata which then sends impulses to the S. A node via the sympathetic nervous system, increasing the heart rate Section 9. 4 – Role of receptors Features of sensory reception A sensory receptor will: †¢ Only respond to a specific type of stimulus (e. g. light, pressure, etc) †¢ Produce a generator potential by acting as a transducer. This means that it can convert the information to a form that the human body can interpret. This is achieved by using the energy of a stimulus into a nerve impulse called a generator potential. Structure and function of a pacinian corpuscle Responds to mechanical pressure Occurs in ligaments and joints so that it is possible to tell which direction a joint is changing The neuron of a pacinian corpuscle is in the centre of layers of tissue, each separated by gel The sensory neuron of a pacinian corpuscle has stretch-mediated sodium channels in its plasma membrane †¢ During its resting state, stretch-mediated sodium channels are too narrow to allow sodium through. The corpuscle therefore has a resting potential †¢ When pressure is applied, the membrane of the neuron is stretched causing sodium channels to widen therefore allowing sodium to diffuse into the neuron †¢ The influx of sodium ions cause a change in the polarity of the neuron, creating a resting potential †¢ The generator potential creates a action potential which moves along the neuron Receptors working together in the eye Different receptors respond to a different intensity of a stimulus Light receptors of the eye are found in the retina (the inner most layer) The light receptors in the eye can are of two types, rod and cone cells. Both receptors convert light energy into a nervous impulse and are therefore acting as transducers Rod cells Cannot distinguish between different wavelengths Many rod cells are connected to the same neuron and so can function at low light intensities. A threshold must be reached in the bipolar cells to which they are attached to and so since they can all contribute to reaching this threshold, they will function at lower light intensities Rod cells breakdown the pigment rhodopsin to generate an action potential. Rhodopsin is easily broken down in low light intensity Since more that one rod cell is connected to the same neuron, only one impulse will be generated. It is impossible for the brain to determine which rod cells were stimulate to begin with and so it is not possible to determine exactly the source of light This results in rod cells having a relatively poor visual acuity and so are not very effective in distinguishing between two points close together Cone cells There are three types of cone cells, each of which respond to a different avelength The colour interpreted depends of the proportion of each type of cone cell stimulated Cone cells are connected only to one bipolar cells, this means that they cannot combine to reach a threshold. As a result of this a high light intensity is required to create a generator potential Cone cells breakdown the pigment iodopsin to create a generator potential Iodopsin can only be broken down by a high light intensity Since cone cells are connected to a single bipolar cell, when two adjacent cells are stimulated, two separate nervous impulses will be sent to the brain. This means that it is easier to determine the source of the light. As a result, cone cells are responsible for higher visual acuity since they allow you to better distinguish between two points Light is concentrated by a lens to the centre of the eye called the fovea. This region receives a high light intensity and therefore has more cone cells. The peripheries of the eye receive a low light intensity and therefore consist mainly of rod cells. Section 10. 1 – Coordination Body systems cannot work in isolation and must therefore be integrated in a coordinated fashion. Principles of coordination In mammals, there are two main forms of coordination: 1. The nervous system – Uses nerve cells that can pass electrical impulses along their length. The result is the secretion of chemicals by the target cells called neurotransmitters. The response is quick, yet short lived and only acts on a localised region of the body. 2. The hormonal system – Chemicals are transported in the blood plasma which then reach target certain cells, thus stimulating them to carry out a function. The responses due to secretion of hormones often act over a longer period of time, yet are slower to act. Chemical mediators Nervous and hormonal forms of communication are only useful at coordinating the activities of the whole organism. At the cellular level they are complimented by chemical mediators. Chemical mediators are secreted by individual cells and affect other cells in the immediate vicinity. A common example of this type of coordination is the inflammation of certain tissues when they are damaged or exposed to foreign agents. Two examples of chemical mediators are: 1. Histamine – Stored in white blood cells and is secreted due to the presence of antigens. Histamine causes dilation of blood vessels, increased permeability of capillaries and therefore swelling the infected area. 2. Prostaglandins – Found in cell membranes and cause dilation of small arteries and arterioles. They release due to injuries and increase the permeability of capillaries. They also affect blood pressure and neurotransmitters. In doing so they relieve pain. Hormonal system |Nervous system | |Communication by chemicals |Communication by nervous impulses | Transmission takes place in the blood |Transmission is by neurons | |Transmission is generally slow |Transmission is very rapid | |Hormones travel to all areas of the body, but target only |Nerve impulses travel to specific areas of the body | |certain tissues/organs | | |Response is widespread |Response is localised | |Effect may be permanent/long lasting/ irreversible |Effect is temporary and reversible | Plant growth factors Plants respond to external stimuli by means of plant growth factors (plant hormones) Plant growth factors: †¢ Exert their influence by affecting growth †¢ Are not produced by a particular organ, but are instead produced by all cells †¢ affect the tissues that actually produce them, rather than other tissues in a different area of the plant. One plant hormone called indoleacetic acid (IAA) causes plant cells to elongate Control of tropisms by IAA IAA is used to ensure that plant shoots grow towards a light source. 1. Cells in the tip of the shoot produce IAA, which is then transported down the shoot. 2. The IAA is initial transported to all sides as it begins to move down the shoot 3. Light causes the movement of IAA from the light side to the shaded side of the shoot. 4. A greater concentration of IAA builds up on the shaded side of the shoot 5. The cells on the shaded side elongate more due to the higher concentration of IAA 6. The shaded side of the root therefore grows faster, causing the shoot to bend towards the source of light IAA can also effect the bending of roots towards gravity. However in this case it slows down growth rather than speeds it up. IAA decreases root growth and increases shoot growth Section 10. 2 – Neurons Specialised cells adapted to rapidly carry electrochemical changes (nerve impulses) from part of the body to another Neuron structure Cell body †¢ Nucleus †¢ Large amounts of rough endoplasmic reticulum to produce neurotransmitters Dendrons †¢ Extensions of the cell body sub-divided into dendrites †¢ Carry nervous impulses to the cell body Axon †¢ A single long fibre that carries nerve impulses away from the cell body Schwann cell †¢ Surrounds the axon †¢ Protection/electrical insulation/phagocytosis. Can remove cell debris and are associated with nerve regeneration. Myelin sheath †¢ Made up from the Schwann membrane which produces myelin (a lipid) †¢ Some neurons are unmyelinated and carry slower nerve impulses Nodes of Ranvier †¢ The gaps between myelinated areas †¢ 2 – 3 micrometers long and occur every 1 – 3mm Sensory Neuron †¢ Transmit impulses from a receptor to an intermediate neuron or motor neuron †¢ One Dendron towards the cell body, one axon away from the cell body Motor neuron †¢ Transmit impulses from the sensory/intermediate neuron to an effector †¢ Long axon, many short dendrites Intermediate neuron †¢ Transmit impulses between neurons †¢ Numerous short processes Section 10. 3 – The nerve impulse A nerve impulse is not an electrical current! It is a self-propagating wave of electrical disturbance that travels along the surface of an axon membrane. Nerve impulse – temporary reversal of the electrical p. d across an axon membrane The reversal is between two states The resting potential no nerve impulse transmitted The action potential – nerve impulse transmitted Resting potential †¢ Sodium/potassium are not lipid soluble and cannot cross the plasma membrane. Transported via intrinsic proteins – ion channels †¢ Some intrinsic proteins actively transport potassium ions into the axon and sodium ions out. This is called the sodium potassium pump. Sodium potassium pump 3 sodium ions pumped out for every 2 potassium ions pump in †¢ Most gated potassium channels remain open – potassium ions move out of the axon down their chemical gradient †¢ Most gated sodium channels remain closed The action potential †¢ Temporary reversal of the charge of the membrane from (-65mV to +65mV). When the p. d is +65mV the axon is said to be depolarised †¢ Occurs because the ion channels open/close depending upon the voltage across the membrane †¢ When the generator potential is reached, sodium ion channels open and potassium close, allowing sodium to flood into the axon. Sodium being positively charged causes the axon to become more positive in charge The passage of an action potential along an unmyelinated axon †¢ Stimulus – some voltage – gated ion channels open, sodium ions move in down electrochemical gradient †¢ Causes more sodium channels to open †¢ When the action potential reaches ~ +40mV sodium channels close †¢ Voltage – gated potassium channels open and begin repolarisation of the axon Hyper – polarisation †¢ The inside of the axon becomes more negative than usual due to an â€Å"overshoot† in potassium ions moving out of the axon. †¢ Potassium channels close †¢ Sodium potassium pump re-established the -65mV resting potential Section 10. 5 – The speed of a nerve impulse Factors affecting speed 1. The myelin sheath – Prevents the action potential forming in myelinated areas of the axon. The action potential jumps from one node of Ranvier to another (salutatory conduction) – this increases the speed of the impulse as less action potentials need to occur 2. The greater the diameter of the axon the greater the speed of conductance – due to less leakage of ions from the axon 3. Temperature – Higher temperature, faster nerve impulse. Energy for active transport comes from respiration. Respiration like the sodium potassium pump is controlled by enzymes. Refractory period After an action potential, sodium voltage-gated channels are closed and sodium cannot move into the axon. It is therefore impossible during this time for a further action potential to be generated. This time period, called the refractory period serves two purposes: It ensures that an action potential can only be propagated in one direction – An action potential can only move from an active region to a resting region. It produces discrete impulses – A new action potential cannot be generated directly after the first. It ensures action potentials are separated from one another. It limits the number of action potentials – action potentials are separated from one another, therefore there is a limited amount that can pass along a neuron in a given time. All or nothing principle Nervous impulses are all or nothing responses A stimulus must exceed a certain threshold value to trigger an action potential A stimulus that exceeds the threshold value by a significant amount, will produce the same strength of action potential as if it has only just overcome the threshold value A stimulus can therefore only produce one action potential An organism can perceive different types of stimulus in two ways: The number of impulses in a given time (larger stimulus, more impulses per second) Having neurons with different threshold values – depending on which neurons are sending impulses, and how frequently impulses are sent, the brain can interpret the strength of the stimulus Section 10. 6/10. 7 – Structure and function of the synapse / Transmission across a synapse A synapse occurs where a dendrite of one neuron connects to the axon of another Structure of a synapse Synapses use neurotransmitters to send impulses between neurons The gap between two neurons is called the synaptic cleft The neuron that produces neurotransmitters is called the presynaptic neuron The axon of the presynaptic neuron ends in a presynaptic knob The presynaptic knob consists of many mitochondria and endoplasmic reticulum These organelles are required to produce neurotransmitters which are stored in synaptic vesicles Synaptic vesicles can fuse with the presynaptic membrane releases the neurotransmitter Functions of synapses †¢ A single impulse from neuron can be transmitted to several other neurons at a synapse. This means that one impulse can create a number of simultaneous responses †¢ A number of different impulses can be combined at a synapse. This means that several responses can be combined to give on single response Neurotransmitters are made in the presynaptic cleft only When an action potential reaches the presynaptic knob, it causes vesicles containing the neurotransmitter to fuse with the presynaptic membrane The neurotransmitter will the diffuse across the synaptic cleft The neurotransmitter then bind with receptors on the postsynaptic membrane, in doing so generating a new action potential in the postsynaptic neuron Features of synapses Unidirectionality Impulses can only be sent from the presynaptic membrane to the postsynaptic membrane Summation †¢ Spatial summation Different presynaptic neurons together will release enough neurotransmitter to exceed the threshold value to form an action potential †¢ Temporal summation – One neuron releasing neurotransmitter many times over a short period. Eventually the neurotransmitter will accumulate so as to overcome the threshold value of the postsynaptic membrane. Therefore generating a new action potential Inhibition Some postsynaptic membranes have protein channels that can allow chloride ions to diffuse into the axon making it more negative than usual at resting potential. This type of hyperpolarisation inhibits the postsynaptic neuron from generating a new action potential. The importance of these inhibitory synapses is that it allows for nervous impulses to be controlled and stopped if necessary Transmission across a synapse When the neurotransmitter across a synapse is the chemical acetylcholine it is called a cholinergic synapse Acetylcholine is made up of acetyl (ethanoic acid) and choline Cholinergic synapses are more common in vertebrates Cholinergic synapses occur in the central nervous system and at neuromuscular junctions 1. When an action potential reaches the presynaptic knob, calcium channels open allow calcium to diffuse into the presynaptic knob 2. The influx of calcium ions causes presynaptic vesciles containing acetylcholine to fuse with the presynaptic membrane, releasing the neurotransmitter into the synaptic cleft 3. Acetylcholine diffuses across the cleft and fuses with receptor sites on sodium channels found on the presynaptic membrane. When they do so, the sodium channels open, allowing sodium ions to diffuse along their concentration gradient into the postsynaptic knob. 4. The influx of sodium ions, generates a new action potential in the postsynaptic neuron 5. Acetylcholinesterase hydrolyses acetylcholine back into the acetyl and choline which will the diffuse back across the synaptic cleft into the presynaptic neuron. In this way acetylcholine can be recycles and reused and also is prevented from continuously generating new action potentials on the postsynaptic neuron. 6. ATP is released by mitochondria, providing energy to recombine acetyl and choline. Sodium channels on the postsynaptic membrane are now closed due to the absence of acetylcholine attached to receptor sites. Section 11. 1 – Structure of skeletal muscle There are three types of muscle in the body: Cardiac muscle which is found only in the heart Smooth muscle which is found in the walls of blood vessels Skeletal muscle which is attached to bone and is the only type of muscle under conscious control Muscles are made up of many muscle fibres called myofibrils If the cells of muscles were joined together from the end of one cell to another, the point between cells would be a point of weakness Because of this, the muscle cells are fused together into muscle fibres Cells of the same myofibrils share the same nuclei as well as cytoplasm (sarcosplasm). Within the sacroplasm are many mitochondria as well as endoplasmic reticulum Microscopic structure of skeletal muscle Myofibrils are made up of two types of protein filament Actin – thinner, consists of two strands twisted around each other Myosin – thicker and is made up of long rod shaped fibres with bulbous heads projecting outwards Myofibrils have coloured bands The isotropic (I) bands appears lighter since it consists only of actin (no overlap) The anisotropic (A) bands are darker since this is where acting and myosin overlap The H zone is the region in the centre of the sarcomere that is lighter in colour since there is only myosin The z line lies at the centre of the I bands Types of muscle fibre Slow-twitch fibres – Contract more slowly, less powerful. Adapted for endurance/aerobic respiration so less lactic acid forms Adaptations include: Large store of myoglobin, Supply of glycogen, Rich supply of blood vessels, Numerous mitochondria Fast-twitch – Contracts more rapidly with more power but only for a short period of time. Adapted for intense exercise by: Having hicker and more numerous myosin filaments, having a high concentration of enzymes used for anaerobic respiration, a large store of phosphocreatine to provide phosphate to make ATP Neuromuscular junctions Many neuromuscular junctions are spread through the muscle for simultaneous contraction Each muscle fibre has one motor neuron associated with it. The muscle fibre and the neuron make up one motor unit When only a small force is needed only a few motor units are stimulated When a nerve impulse reaches the neuromuscular junction, the synaptic vesicles join with the presynaptic membrane and release acetylcholine which diffuses across to the postsynaptic membrane and stimulates it to allow sodium ions to enter. The acetylcholine is then broken down by Acetylcholinesterase and then diffuses back into the presynaptic neuron. Section 11. 2 contraction of skeletal muscle During muscle contract, actin and myosin slide past each other; hence its name the sliding filament mechanism Evidence for the sliding filament mechanism When a muscle contract, the following changes occur to the sarcomere: The I band becomes narrower The z lines move close to one another The h band becomes narrower The a band does not change as this band is determined by the width of the myosin Myosin is made up of two different types of protein 1. A fibrous protein arranged into the filament called the tail 2. A globular protein that forms a head at each end Actin is a globular proteins thats molecules are arranged into two chains that twist around each other in a helical manner Tropomyosin forms long thin stands that s wound around the actin molecule The process of muscle contraction has a three main stages: Stimulation, contraction and relaxation Muscle stimulation When an action potential reaches the neuromuscular junctions, Calcium ion channels open and calcium ions move into the synaptic knob The Calcium ions cause the synaptic vesicles to move to the presynaptic membrane and fuse with it releasing acetylcholine Acetylcholine diffuses across the synaptic cleft and binds with receptors on the sodium voltage gated channels on the postsynaptic membrane causing it to depolarise Muscle contraction The action potential movies through the fibres by travelling through T – tubules that branch through the sarcoplasm The action potential moves through the tubules until it reach the sarcoplasmic reticulum The action potential opens calcium ions in the sarcoplasmic reticulum Calcium ions diffuse out into the muscle Calcium ions cause tropomyosin to change shape and so that the binding sites on the actin filament are exposed An ADP molecule that is attached to the myosin heads allows it to form a cross bridge with actin by binding with the receptor site Once the cross bridge is formed, the myosin head changes shape and slides the actin across. In doing so it loses the ADP An ATP molecule attaches to the myosin head and thus causes it to detach Calcium ions activate the enzyme ATPase which hydrolyses ATP and releases energy that allows the myosin head to resume its original shape. The myosin head now has a new ADP molecule that will allow it to bind with a new receptor site somewhere along the actin filament Muscle relaxation When the muscle is not being stimulated, the sarcoplasmic reticulum actively transport calcium ions back into it The lack of calcium ions means that tropomyosin can establish its original position, covering the myosin head binding sites Energy supply Energy is needed for the movement of myosin heads and the active transport of calcium ions ATP often needs to be generated anaerobically Phosphocreatine provides inorganic phosphate molecules to combine with ADP to form ATP Section 12. 1 – Principle of homeostasis The maintenance of a constant internal environment By maintaining a relatively constant environment (of the tissue fluid) for their cells, organisms can limit the external changed these cells experience thereby giving the organisms a degree of independence. What is homeostasis? Maintaining the volume, chemical make up and other factors of blood and tissue fluid within restricted limits There are continuous fluctuations; however, they occur around a set point Homeostasis is the ability to return to that set point thus maintaining equilibrium The importance of homeostasis Enzymes and other proteins are sensitive to changes in pH and temperature Water potential of blood and tissue fluid should be kept constant to ensure cells do not burst or shrink due to a net movement of water (osmosis) Maintaining a constant blood glucose concentration ensures that the water potential of the blood remains the same Independence of the external environment – a wider geographical range and therefore a greater chance of finding food shelter, etc Mammals – homeostasis allows them to tolerate a wide range of conditions Control mechanisms The set point is monitored by: 1. Receptor 2. Controller brain analyses and records information from a number of different sources and decides on the best course of action 3. Effector – brings about the change to return to set point 4. Feedback loop – informing the receptor of the changes in the system brought about by the effector Section 12. 2 Thermoregulation Mechanisms of heat loss and gain Production of heat – Metabolism of food during respiration Gain of heat from the environment – Conduction, convection (surrounding air/fluid), Radiation (electromagnetic waves particularly infrared) Mechanisms for losing heat Evaporation of water Conduction – to ground/solid Convection convection (to surrounding air/fluid), Radiation Endotherms derive most heat energy from metabolic activities Ectotherms – obtain most heat from the external environment Regulation of body temperature in Ectotherms Body temp fluctuates with the environment Controlled by exposure to the sun Shelter to the sun/burrows at night/obtains heat from the ground and very little from respiration. Can sometimes change colour to alter heat that is radiated Regulation of body temperature in Endotherms Most heat gained through internal metabolic activities Temperature range 35 – 44 oC – Compromise between higher temperature where enzymes work more rapidly and the amount of energy needed (hence food) to maintain that temperature Conserving and gaining heat in response to a cold environment Long term adaptations: Small SA:V ration Therefore mammals and birds in cold environments are relatively large Smaller extremities (e. g. ears) thick fur, feathers or fat reserves to insulate the body Rapid changes: Vasoconstriction – reducing the diameter of arteries/arterioles Shivering – in voluntary rapid movements and contractions that produce he energy from respiration Raising hair – enables a thick layer of still air to build up which acts as a good insulator. Behavioural mechanisms – bathing in the sun Decreased sweating Loss of heat in response to a warm environment Long term adaptations: Large SA:V ratio so smaller animals are found in warmer climates Larger extremities Light coloured fur to reflect heat Vasodilation – Arterioles increase in diameter, more blood reaches capillaries, more heat is therefore radiated away Increased sweating – Heat energy is required to evaporate sweat (water). Energy for this comes from the body. Therefore, removes heat energy to evaporate water Lower body hair – Hair erector muscles relax. Hairs flatten, reduces the insulating layer of air, so more heat can be lost to the environment Behavioural mechanisms – seeking shade, burrows, etc Control of body temperature Mechanisms to control body temperature are coordinated by the hypothalamus in the brain The hypothalamus has a thermoregulatory centre divided into two parts: A heat gain centre which is activated by a fall in body temperature And a heat loss centre which is activated by an increase in temperature The hypothalamus measures the temperature of blood passing through it Thermoreceptors in the skin also measure the temperature Impulses sent to the hypothalamus are sent via the autonomic nervous system The core temperature in the blood is more important that the temperature stimulating skin Thermoreceptors Section 12. 3/12/4 – Hormones and the regulations of blood glucose/Diabetes and its control Hormones are produced by glands (endocrine glands) which secrete the hormones into the blood The hormones are carried in the blood plasma to the target cells to which they act. The target cells have complementary receptors on the cell surface membrane Hormones are affective in small quantities set have widespread and long-lasting affects Some hormones work via the secondary messenger model: 1. The hormone (the first messenger) binds to receptors on the cell surface membrane, forming a hormone-receptor complex 2. The hormone-receptor complex activates an enzyme inside the cell that produces a secondary messenger chemical 3. The secondary messenger acts within the cell produces and a series of changes Both glucagon and adrenaline work by the secondary messenger model Adrenaline as a secondary messenger 1. The hormone adrenaline forms a hormone-receptor complex and therefore activates an enzyme inside the cell membrane 2. The activated enzyme the converts ATP to cyclic AMP which acts as the secondary messenger.

Thursday, February 13, 2020

Public health law. (summary topic about marijuana legalization ) for Scholarship Essay

Public health law. (summary topic about marijuana legalization ) for scholarly paper. not full scholarly paper but only one page summary topic - Scholarship Essay Example In addition, it is also argued that decriminalizing the use and sale of marijuana would reduce the processing and enforcement tasks for criminal justice agencies that are associated with marijuana use. Thirdly, proponents for decriminalization of marijuana contend that a direct correlation exist between the number of cases or arrests that the criminal justice system processes for marijuana sale and use and the funds used by criminal justice agencies (Brownstein, 2013). Finally, there is an argument that elimination or reduction of events related to marijuana would portend a proportionate decline in the expenses for criminal justice agencies. However, opponents of this argument claim that the increased use of marijuana that will result from legalization (Pacula & Kilmer, 2013), which may result in additional crime and a subsequent increase in costs for non-criminal justice agencies like mental health facilities. In addition, it is also claimed that legalizing marijuana could result in lower worker productivity due to the depressant-effects of marijuana. Finally, statistics show that a high proportion of those in adult correctional facilities have an ongoing marijuana habit and, therefore, legalizing marijuana would result in increased rates of crime (Hoobler & Hoobler, 2012). In conclusion, it seems that the decriminalization or legalization of marijuana may only portend marginal effects on costs to the criminal justice system. However, it could allow the criminal justice system to focus on public safety issues of more

Sunday, February 9, 2020

Subtopics For Digital Downloading - What to Look For

Subtopics For Digital Downloading - What to Look ForSubtopics for digital downloading are similar to other books, except they are called sub topics. In some cases you can find these books online or you can buy them, but there are some things that you should consider before buying them.Most of the books are written by experts in the field of the subject matter and are designed for expert students or teachers to use as teaching materials. You should expect that the book will contain things that a general reader will not understand. Many times they are created by people who do not have experience teaching the subject they are writing about, and are therefore liable to make a number of mistakes and/or omit important facts.If you are going to buy a subtopic for digital downloading research paper then you should be very careful when making your decision. This is because you are going to use this as your academic reading material for your own learning. You should make sure that the content is sound and that it will help you pass your final exams. In addition to this, you should make sure that the book is taught in such a way that it does not leave out any important facts.In addition to this, you should know the author and publisher of the book before buying it. You need to get their feedback if they believe that the content is useful or necessary to the reading material of your choice. You may also check out the review section of some good selling books on the internet.If you want to use a book as your own reading material then you need to go through it with a fine tooth comb. You should also examine it for spelling and grammar errors and if there are any typos that you might find to be quite annoying.Many publishers will include a section where they will reply to all the questions that have been raised by their readers. This will give you an opportunity to compare and contrast the various book reviews of their book and also allow you to get an insight into the overal l quality of the book. There will be different opinions that can be found in different reviews and you will need to assess them to get the best one.You should go online to find out more about subtopics for digital downloads. You can read online reviews of these books and decide whether they are worth spending your money on. All these will help you choose the right one.

Friday, February 7, 2020

Reported News on Freedom of Speech College Essay Discovered

Reported News on Freedom of Speech College Essay Discovered The Ugly Side of Freedom of Speech College Essay The modern notion of speech isn't restricted to speaking or writing. People today see their meaning inside this word. Freedom of speech is vital portion of democratic government, as the only way truth can emerge is whenever there is an open competition of ideas. Freedom of views and speech is easily the most important kind of interaction as without sharing there would not be any history and science in any respect. We've kept the language of this essay simple to comprehend yet good enough to provide you with the insights of the topic. Your essay has to be between 700-900 words. As a result of important elements of speech, thus, this essay explains the liberty of speech, its importance, and limitations. Here are essays of varying lengths on the subject Freedom of Speech to assist you with the exact same in your exam. The Basics of Freedom of Speech College Essay Speech is built in to our lives as a means to communicate with other individuals. That organisation has done some substantial work to boost the dignity of gay individuals, but surely the Government aren't bound to accept its whole agenda. Students have to be allowed to discuss the new world they've just entered and to speak about it freely. They lead busy lives and often forget about an upcoming deadline. Getting the Best Freedom of Speech College Essay The people who do voice their opinions attempt to maintain a very low profi le. However, these sounds form language and possess the certain sense. A nation full of people full of discontent cannot grow in the ideal direction. All About Freedom of Speech College Essay This function of free speech is a type of safety valve. Freedom of Speech gives way to open discussions that assists in exchange of ideas that's necessary for the increase of the society. It is essential for the all round growth and development of a person as well as a nation as a whole. It however can end up breaking an individual depending on how an individual is using it. The content-neutral regulation demands an extremely careful distinction and so may at times be misinterpreted. Care ought to be taken by the many communities that fascism isn't promoted in the guise of freedom. One of the absolute most important benefits of the freedom of speech is it will help to bring in peaceful changes without muzzling the government. Both bodily and mental freedoms are important and ought to be used equally to be certain they bring about an excellent health to the person. Who Else Wants to Learn About Freedom of Speech College Essay? Excellent in the feeling that it was nonviolent, but an extremely effective protest. Sadly, this type of challenge to campus free speech is currently widespread. Further, it is an essential point of connection as it is done consciously. Zoning speech is troubling, especially when it reduces the general quantity of speech on campus. Freedom of Speech College Essay Can Be Fun for Everyone Another theoretical ground to support the liberty of speech is known as tolerance theory. Among the obvious shortages of an excessive amount of freedom of speech is the terrible influence on public. This freedom includes the capacity to express one's opinion, irrespective of its nature good or bad. The liberty of speech has an important impact in our social life. We'll deal with them, and for a sensible price, as we understand that students typi cally don't have lots of money to spare. It's also vital to express one's opinion about the political system of the nation. You should have your reasons, and our primary concern is that you wind up getting a great grade. In this instance, a student criticized the erection of two parking garages which he thought would damage the surroundings and increase the already prominent health problems of the nation. For instance, the Congress can't make a rule prohibiting certain varieties of speech, but an individual may. Limitations, like withdrawing the liberty of speech to some individuals, are however enforced for the interest of protecting different persons, besides creating law and order. Furthermore, having freedom of speech is vital as it aids in pointing out various kinds of harassments that junior officials could possibly be subjected to by their seniors. It comes along with different responsibilities that an individual should be aware of the best way of dealing with them. W hat Freedom of Speech College Essay Is - and What it Is Not Flag burning is an instance of symbolic speech that's protected under the First Amendment. However, the world has decided that freedom of speech is vital, and it has been proven by the introduction of the First Amendment. In conclusion, freedom of speech has many exceptions and isn't defined just as it's stated. The liberty of speech isn't an absolute in any nation and it's rightly common subject to limitations. The Awful Secret of Freedom of Speech College Essay Prior to any speech is punished on the grounds of incitement, there's an obligatory three-part criterion that needs to be met. Quite simply, while the government couldn't prohibit protesting the Vietnam War, it might punish this system of protest which served to curtail the operation of the draft. Democratic countries can easily deal with the dissent as they offer an outlet in the type of free speech. In the majority of instances, freedom of expression cou ld be restricted only if it is going to cause direct and imminent harm.

Wednesday, February 5, 2020

Unbiased Report Exposes the Unanswered Questions on Term Papers on Person-environment Fit

Unbiased Report Exposes the Unanswered Questions on Term Papers on Person-environment Fit Key Pieces of Term Papers on Person-environment Fit My background is just one of an individual in a very long term sobriety, having passed the sign of 27 years last December 7th. For instance, training programs are found to raise the interest and performance in math and science for young ladies. The student is supposed to concentrate on the robust and the weak sides of sports management and rate the relevance of the issue in the human life. Furthermore, the teacher will want to devote much time to the maturation of the student's interest towards sports and physical training solely for the maintenance of his wellbeing, regardless of whether the student would like to earn sportsman's career or not. Term Papers on Person-environment Fit Secrets That No One Else Knows About Reading totally free essays may give students realistic goals about the kind of writing they are able to aim for in the brief term. A totally free report differs from a customized essay in a lot of ways. A totally free essay on the internet is often presented as a model for students unsure of how to compose an essay or the way to compose an essay on a certain topic. There are a number of reasons why a student might have to reference a free essays'' term paper for a class. The Little-Known Secrets to Term Papers on Person-environment Fit Within organizations, fit can be assessed in a multitude of ways with a lot of characteristics of the work atmosphere. It is very important to match abilities with demands. There are many choices to select from. As mentioned above, the ideal way of assessment of the environment isn't agreed upon. The Secret to Term Papers on Person-environment Fit Thus, when you have conducted your literature review, you're going to be in a place to present your research findings. While there is very good value in having the capacity to incorporate career testing equipment a nd scoring, within my practice, I feel it to be totally focused in that area would be damaging to the practice. Review the case studies and select one that you want to analyze. Based on your topic you might need to depend on the scientific report style or literature review styles, or a mix of the two. When students are requested to prepare a term paper, they are usually nervous, because don't understand how to begin or develop their paper, don't have any ideas concerning the topic or cannot create interesting and smart solutions. Some students try to find term papers for free so they can use samples of term papers to make their own documents. They may use a free term paper in order to learn more about the proper format. We'll request a duplicate of the book from the publisher. Free book reports are offered from a number of sources. Because of this, it's almost always a great notion to explore what research is already done on your topic before you start to construct your own argument. Guided by an appropriate theory, you're supplied a foundation for your hypotheses and choice of research procedures. Hollands theory on the surface may appear easy, but the interest in his theory are useful and can indicate a great deal more than only the forms of work an individual will enjoy. The person-in-environment (PIE) theory is the essential idea and philosophy in the specialty of social work that states that an individual's behavior can largely be understood by taking a look at their environment, including their previous atmosphere. The Importance of Term Papers on Person-environment Fit Students who are trying to get such reports online ought to be discriminating in their selection. There are a large number of resources online where students can find term papers at no cost. We always encourage students to request a no cost Turnitin report. Students should remain sure the totally free dissertations they're using are accurate, higher quality, and contain the suitable formatting requirements. Many students search for term papers for free when they want to see an illustration of what a report appears like. When employing a completely free student essay as an essay model, learners need to try to ascertain the method by which the report works. So as to compose high-scoring and well-written reports, many learners not only have to review thesis requirements, but they might also want to review completely free thesis paper examples. What to Expect From Term Papers on Person-environment Fit? Best quality for a moderate price is getting a reality now! It must be noted that person-environment fit models have been successfully applied to a wide selection of behavior settings. These two kinds of fit can overlap. Person-Environment fit has been a subject of greater interest over the last two decades.

Saturday, February 1, 2020

Histology Case Study Example | Topics and Well Written Essays - 500 words - 1

Histology - Case Study Example This patient had shoulder pains and later was diagnosed with carcinoma of scapula and spine. It was found that the metastasis was from the lung. Identification of Metastatic tissues: The Fourier transform-infrared statistical models are able to identify the changes in structure of DNA at different levels of development of tumors. The DNA structures that are connected to the development of metastasis are usually foreordained in the progenitor cells much earlier in several steps of tumorigenesis. Biopsy and immunoglobulin methods used to diagnose cancer. People having metastasis in lungs may not show symptoms early but through medical examination and with using imaging techniques can be used to diagnose primary cancer that lead to the diagnosis of pulmonary metastasis. In case of slow developing primary tumor, metastasis can be noticed much early at the initial stages of the disease. The spread is usually through blood, lymphatic vessels or both. Identified cells in sample of lung tissue and their characteristics: The affected cells in the lung tissues are like the goblet cell, epithelial cells basal cells etc. The epithelia cells have a define shape. The following are the characteristics of the epithelia cells i.e. they can be polygonal or cuboidal or rectangular. Few are irregular. They are compactly arranged on a tiny membrane. They usually lack intercellular spaces. They have a lot of cytoplasm. They are uninucleate. They can undergo mitotic divisions. Goblet cells have the following characteristics i.e. they are cup shaped and produce mucous fluid composed of a protein called mucin that is bonded with an electrolyte solution. Identifying cells responsible for the tumor: Melanoma pigment is found on these epithelia cells once they are metastasized. Melanoma can be described as a cancer of cells that produce pigments and are found on the mucous membranes. Their presence is an indication cancer and should therefore