es1730 - exam paper analysis

8/6/2019 ES1730 - Exam Paper Analysis

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ES173 - Past Paper Content

Body Chemistry and Cell Structure

Characteristics of life Organisation, Cellular composition, Metabolism, Responsiveness and movement, Homeostasis,

Development, Reproduction, Evolution (Page 15-16) Organelles

Nucleus Largest organelle Contains genetic information Produces RNA

Mitochondria Produce energy

Endoplasmic reticulum Rough

Produces protein Smooth

Produces lipids Golgi complex

Collects, packages, and distributes molecules which have been synthesised in one place andare needed in another

Ribosomes Read mRNA and interpret it Synthesise proteins from amino acids

Peroxisomes Neutralise free radicals Detoxify alcohol

Lysosomes Contain enzymes Hydrolyse substrates

Centrioles Assembly of microtubules which play a role in cell division

Size limitations Surface to area ratio decreased for larger cells Diffusion is limited by surface area Enough nutrients must be able to diffuse through the membrane to support the cell

Macromolecules

Carbohydrates Source of energy (and membrane components)

Lipids Source of energy Energy storage Cell membrane components Chemical messengers Coating of nerve cells

Proteins Function determined by shape Provide structure (collagen)

Communication Membrane transport Recognition and protection (antigens and antibodies)


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Cell adhesion (cell adhesion molecules) Catalysis (enzymes)

Nucleic acids Genetic code (DNA) Instruction carriers (RNA) Energy carriers (ATP/ADP)

Homeostasis The tendency of a living body to maintain relatively stable internal conditions in spite of greater

changes in its external environment

Na+- K+ pump Protein pump which uses ATP to pump 3 Na+ out of a cell, and 2 K+ into the cell Functions

Regulates cell volume reduces osmotic pressure Cell anions attract cations and cause osmosis Pumps open when cell swells

Maintains a steep concentration gradient of Na+ and K+ Secondary active transport

Symporters move Na+ into cells along with a second solute Heat production Maintains resting membrane potential

Essential for nerve and muscle function Negative inside cell, positive outside cell

Cellular metabolism Glucose Pyruvic acid + 2 ATP Anaerobic

Pyruvic acid Lactic acid Aerobic

Pyruvic acid CO2 + H2O + 36 ATP Visualisation instruments

Compound microscopes Transmission electron microscopes Scanning electron microscopes

Contrast improvement in microscopy Polarised light

Used on specimen which exhibit double refraction Phase contrast imaging

Small phase shifts in the light transmitted through the specimen are converted to amplitudeor contrast changes in the image

Differential interference contrast Polarised light is split into two rays which are polarised at 90o to each other Rays pass through the specimen at a slight separation Rays are recombined into one, which results in an interference pattern representing the

difference between adjacent areas of the image

Fluorescence illumination Specimen illuminated by one wavelength of light Another, longer, wavelength of light is produced by the specimen

Dark field illumination Unscattered light is not used to produce the image, only the light scattered by the specimen Leads to a black background

Rheinberg illumination Similar to dark field i llumination, but coloured filters are used and so coloured backgrounds

and higher contrast result


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Hoffman modulation contrast Phase gradients are converted to variation in light intensity Gives 3d appearance

Optical fibres AFM

Uses a probe attached to a cantilever Probe usually just a few atoms wide at the tip Scanned over the surface, repelled by the electron shells of the atoms in the specimen Achieves atomic resolution

STM Relies on quantum tunnelling Voltage bias between specimen and probe Probe is scanned across the surface Electrons tunnel from the probe to the specimen and the current is measured Achieves atomic resolution

Nucleotide components Phosphate group Ribose sugar (RNA), or deoxyribose sugar (DNA) Nitrogenous base

Major parts of a cell Genetic material

Stores hereditary information in the cell Cytoplasm

Fills the cell interior Plasma membrane

Encloses the cell Provides control over entry and exit of substances

DNA

Natural selection Some individuals have hereditary advantages over others Advantages which aid survival increase reproductive success, and so those genes passed on Darwin was inspired by the variations between beaks of finches on the Galapagos Islands

Each was adapted to suit the food that was available for the bird Evolution

Through time, species accumulate differences; as a result, when new species are formed, thedescendent species differ from their ancestors Charles Darwin

Genetic mutation Occur due to imperfect nature of DNA replication Segments may be repeated or deleted Crossing over of DNA during meiosis Single nucleotides can be altered during replication Can occur due to environmental factors such as radiation, chemicals, or viruses

DNA Deoxyribonucleic acid Nucleotides are bonded via phosphate-sugar bonds and also by hydrogen bonds with their

complementary base

Twisted ladder - double alpha-helix Store of genetic information

RNA Ribonucleic acid


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Nucleotides bonded together via phosphate-sugar bonds Usually single stranded with a complex 3d shape Uracil instead of thymine mRNA carries information that directs protein synthesis

ATP Adenosine triphosphate Store of chemical energy Produced from ADP during respiration, used during any process requiring energy

Determination of DNA sequence Fluorescently labelled dideoxyribonucleic acids stop the polymerase enzyme from continuing on

the strand

Electrophoresis then used to determine the lengths at which the polymerase stopped at eachspecific nucleotide

Electrophoresis Uses an applied electric field to separate DNA fragments by size Utilises fluorescent markers at the end of DNA fragments to visualise the locations on the gel

DNA replication Semi-conservative DNA spilt into single strands by DNA helicase Single Strand Bonding proteins prevent DNA from reannealing Primase synthesises the short RNA sequences needed to start replication Polymerase then replicates the DNA using the complementary bases DNA is replicates continuously on the leading strand, and discontinuously on the lagging strand

Synthesis in the 5 to 3 direction (of new strand) RNase H removes the RNA strands which began the synthesis DNA ligase links short stretches together to form one long continuous strand

DNA amplification PCR

Amplified short sections of DNA DNA is split into single strands by heating, and is then replicated Uses Taq polymerase to allow DNA to be amplified exponentially

LightCycler Commercial automated implementation of PCR Rapid cycling and simultaneous closed tube detection

AFM in DNA sequencing DNA immobilised on either glass or gold and is placed under water The probe is tapped up and down to avoid damaging the DNA as it is scans

Atomic resolution is achieved and the DNA sequence can be interpreted Rosalind Franklin

Discovered that the phosphate groups were on the outside of the DNA molecule Created the x-ray crystallography photos which Watson and Crick used to determine the

structure of DNA

Watson and Crick Determined the structure of DNA from Rosalind Franklins photos Created a model of the DNA structure

Circulation and Respiration

Major parts of circulation system Lymphatic System

Lymph nodes Garrisons of B, T and other immune cells


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Act as filters for foreign particles Lymph capillaries

Tiny thin walled tubes which are spread throughout the body (except the centralnervous system and non-vascular tissues)

Drain excess fluid from tissues Interstitial fluid can flow into them but not out of them Attached to the surrounding tissue by elastic fibres which extend from the endothelial

cells

Lymph trunks Carries lymph from efferent lymph vessels Drains lymph into one of two lymph ducts

Vascular System Heart

Pulmonary circuit Right side of the heart Supplies blood to the lungs for gas exchange

Systemic circuit Left side of heart Supplies blood to all organs

Arteries Arterioles Capillaries

Diffusion through endothelium Lipid soluble substances

Steriods, O2, and CO2 Diffuse easily

Lipid insoluble substances Glucose and electrolytes Must pass through channels, fenestrations (proteins) or intercellular clefts

Large particles Large proteins are held back

Transcytosis Fatty acids, albumin, some hormones (insulin)

Filtration and reabsorption Venules Veins

Routing of blood flow Contraction of smooth muscle layer causes vasoconstriction which increase resistance and

decreases blood flow

Pressure downstream decreases, upstream pressure increases Relaxation of smooth muscle layer causes vasodilation which decreases resistance and increases

blood flow

Blood routing mainly controlled by arterioles as they are numerous, and more muscular bydiameter

Pulse oximetry Operation

Uses selected wavelength of light to determine the saturation of oxygen Pulsatile signal generated by arterial blood

What is measured? Directly measures the amount of light at specific wavelengths which is absorbed Indirectly measures pulse rate and oxygen saturation levels


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Basis of measurement Limitations

Motion artifacts Intravascular dyes Exposure to ambient light during operation Skin pigmentation Nail polish Less accurate below 83% saturation Cannot quantitate hyperoxemia False negatives for hypoxemia

Cannot be used on patients who have inhaled smoke as the probe cannot distinguishbetween carboxyhaemoglobin and oxyhaemoglobin.

High levels of methaemoglobin (haemoglobin with Fe3+ instead of Fe2+)cause the probe toread 85% regardless of actual oxygen saturation.

Falsepositives for normoxmeia or hyperoxemia Probe misuse

Pressure sores Electrical shocks

Congenitally corrected transposition Can cause fainting and fatigue

Influencing factors of diffusion Surface area Concentration gradient Membrane permeability Molecular weight Temperature

Organs and Visualisation Organ systems

Regulation and Maintenance Digestive system Circulatory system Respiratory system Urinary system Lymphatic and immune systems

Support and Movement Skeletal system

Skeletal muscular system Integumentary system

Integration and Control Nervous system Endocrine system

Reproduction and Development Reproductive system

Resolution The smallest distance between two points on a specimen which can be distinguished as being

separate entities

Magnification Relative size of the image compared to the specimen

Endoscopy Construction


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Rigid or flexible tube Light source usually delivered via non-coherent bundles of optical fibres Either a lens system as in rigid endoscope, or a bundle or coherent optical fibres in the case

of flexible endoscopes

Eye piece or CCD camera Additional channel for tools to be inserted

Operation A small incision can be made if necessary, then the endoscope is inserted into the body The physician views the image produced for the purpose of diagnosis or surgery

Use Used to look inside the body either through an opening in the body such as the mouth or

anus, or through a small incision

Advantages Only a small incision is required

Pill camera Small camera fitted inside a transparent capsule Capsule contains its own light source, and some means of powering it The capsule is swallowed and relays its image via radio waves Allows for a video of the journey through the digestive tract to be recorded

OCT Similar to ultrasound, but uses light instead of sound A broad spectrum of light is split into a sample arm and a reference arm By combining the reflected light from the sample with the reference light, an interference

pattern can be formed

Scanning the mirror allows for a reflectivity profile of the sample to be produced (time domainOCT)

Tissue Definition

An aggregation of cells and extracellular materials, usually forming part of an organ andperforming some discrete function for it

Types Epithelial

One or more layers of closely adhering cells Flat sheet at the surface exposed to the environment or an internal cavity No blood vessels Specialised into glands (exocrine and endocrine)

Exocrine Endocrine

Sits on basement membrane Connective

Widely space cells connected by fibres and ground substance Most abundant and variable type Examples:

Tendons Bone, cartilage, lymphatic system

Bone is a calcified matrix of concentric lamellae around central (Haversian)canals containing blood vessels

Osteocytes in lacunae between lamellae, connected by canalculi Adipose tissue Blood (Fibres in soluble form polymerise when they leak. Ground substance is

plasma)


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Muscle Elongated cells that respond to stimuli by contracting Exert physical force on other tissues Source of body heat 3 types:

skeletal cardiac smooth

Nerve Neurons and neuroglia For internal communication between cells Found in brain, spinal cord, nerves, and ganglia

Medical Imaging

PET Positron emission tomography A positron-emitting tracer is introduced to the body on a biologically active molecule The radioactive decay of the tracer leads to the emission of pairs of gamma rays Computer analysis is then used to determine the position of the tracer and the concentration of

the biologically active molecule

Photons not arriving in temporal pairs are ignored Photons are emitted at almost 180o and so their origin can be determined to with a reasonable

degree of precision

CT X-ray computer tomography Generate a 3d image from a series of 2d images taken around a single axis Contrast agents can be used to highlight blood vessels

MRI Magnetic resonance imaging MRI scanners use a strong uniform magnetic field combined with a gradient field to align the

magnetic moments of hydrogen nuclei in water

An RF transmitter is used to flip some of the magnetic moments so that they are in anti -parallelwith the magnetic field

The hydrogen nuclei then return to their low energy state and release this energy in a photon Frequency of emitted photon is dependent on the position within the magnetic field

fMRI Used to show the change in blood flow related to neural activity in the brain or spinal cord MRI is sensitive to the change in oxygen concentration changes

Ultrasonic Used to visualise subcutaneous body structures such as tendons, muscles, joints, vessels,

internal organs, and foetuses

An ultrasound pulse is sent out and is reflected at boundaries between tissues of differentacoustic impedances

The time delay before pulse is returned is dependant upon the penetration depth, and so thedepth of the boundaries can be found

Functional imaging (define) The in vivo diagnosis of physiological states and of dynamic processes, such as metabolism and

blood flow, by imaging

Prosthesis and Biomimicking

Two examples


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Function Requirements History Cost Materials Manufacture Usage constraints Lifetime

Bones, Muscles and Diagnostic Instrumentation

Striated muscle Skeletal muscle Voluntary control Attached to bone

Universal characteristics of muscle Responsiveness

Responsive to chemical and electrical signals Conductivity

Local electrical change triggers a wave of excitation Contractibility Extensibility Elasticity

EMG Surface pads or intramuscular needles Measures the electrical activity of skeletal muscle

Cardiac Cycle Ventricular filling

AV valve opens and blood fills ventricle Atrial systole occurs and forces more blood into the ventricles

Isovolumetric contraction Atria remain in diastole for the remainder of the cycle Ventricles depolarise and generate QRS complex AV valves close

Ventricular ejection Ejection of blood begins Not all blood is ejected

Isovolumetric relaxation Ventricular diastole Slight pressure rebound

Diagnosis of Heart problems Mixture of ultrasound, ECG, chest x-rays, and MRI/CT

ECG Numerous pad placed around the body at key points Detects and amplifies tiny electrical changes caused when the heart depolarises in each cycle Produces a trace of heart activity

EMS Electrical muscle stimulation Electrical impulses mimic action potentials from the CNS and so stimulate the muscle Bike for disabled

Belts around the legs


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Synchronised pulses in a set pattern so that the muscles contract in the correct sequence tocycle the pedals

Provides better exercise than stationary EMS Joint types (Page 287)

Diarthrosis Freely moveable

Amphiarthrosis Slightly moveable

Synarthrosis Little or no movement

Fibrous Collagen fibres between two bones Joint between palatine processes in the roof of the mouth

Cartilaginous Two bones bound by cartilage Intervertebral discs of fibrocartilage

Bony Two bones joined by osseous tissue Right and left mandible bones fused together

Synovial Bones separated by fluid filled space Knee, hip, elbow, finger joints

Weakness in astronauts Bone volume decreases Muscle volume decreases Changes due to reduced loading in zero gravity

Four roles of skeletal muscles Movement Posture Joint stability Heat production

Brain and Nervous System

Structure of nerve cell Dendrites Soma (cell body) with nucleus Axon which may be wrapped by myelin sheath (due to Schwann cells) with nodes of Ranvier in

the gaps in the myelin sheath Ends with synaptic knobs

Fundamental properties Excitability

Respond to changes in the body and external environment (stimuli) Conductivity

Produce and propagate electrical signals Secretion

Chemical neurotransmitter secreted when the signal reaches the end of the fibre Conduction in nerves

Resting potential Maintained by Na+-K+ pumps, voltage-gated ion channels, and large negatively charged

molecules

Negative on inside, positive on the outside


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Action potential When activated, voltage-gated ion channels become more permeable and Na+ rushes into

the cell

Cell depolarised by influx of positive charges Causes a chain reaction to propagate down the axon

Unmyelinated fibres Self-propagating action potential propagates down the length of the axon Influx of Na+ depolarises the adjacent length, and so generates a new action potential

Myelinated fibres Myelin sheath insulates sections and so impulse travels by Na+ diffusing along the axon and

depolarising the node of Ranvier to produce a new action potential

Decremental and so nodes are needed at least every millimetre Comparison of nerves to electrical wires

Nerves are digital, wires are analogue Current flow is longitudinal in wires, and transverse in nerves

Transmission speed Depends on diameter and presence of myelin Large myelinated nerves are faster

EMG to diagnose problems For intramuscular EMG, the output is monitored as the needles are inserted because the

muscles react electrically

The electrical activity when the muscles are inactive should be zero the presence ofspontaneous signals suggests that there is a problem

EEG Records the electrical signals in the scalp PAGE 538

ERP Effective refractory period Once an action potential has been initiated, there is a period of time for which another action

potential cannot be generated

Local Anaesthetics Blocking of Na+ gates

Prevents depolarisation Stops the generation and propagation of action potentials Local anaesthetics occupy the Na+ channel and inhibit the rapid influx of Na+

Significance of squid to transmission Large neurons which could easily be isolated Larger, but similar in nature to human nerve cells Large enough for electrodes to be inserted in order to measure the membrane potential

Phineas Gage Had a bar blasted through his skull and damaged the left frontal lobe Had impaired planning, mood and social judgement Influenced 19th Century thinking about cerebral localisation of functions Demonstrated that the frontal lobe controls these things

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