Human Biology Block 2-9 Notes PDF

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Tissues 1: Cell StructurePowerPoint SlidesAims: Explain the concepts of the dynamic cell and describe how it functions normally Describe the different routes of protein transport within a cell DynamismBasic cell organelles recap-Our cells are live in many ways and are actually moving dynamically, th...

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Tissues 1: Cell Structure PowerPoint Slides

Aims: - Explain the concepts of the dynamic cell and describe how it functions normally - Describe the different routes of protein transport within a cell Dynamism Basic cell organelles recap-

Our cells are live in many ways and are actually moving dynamically, things in the cell are not stationary and instead are forever changing and shifting around. In order to have effective compartmentalisation within the cell compartments must work together dynamically to maintain a healthy cell. Lipid distribution in the plasma membrane is not a product of random distribution, instead their distribution most of the time is asymmetric. One layer has different lipid composition in comparison to the opposing layer. While many proteins move within the plane of the membrane some are fixed. The mobility of different plasma membrane proteins is investigated using Fluorescence Recovery After Photobleaching (FRAP). Transporters, channels, anchors, receptors and enzymes are the things that sit within our plasma membrane that enable and promote dynamism in the cell. If they have different roles and functions, they will have different locations also. We absorb glucose in the gut with a glucose-sodium cotransporter, energy is required to get glucose into our cells from the intestinal lumen is comes from the sodium gradient. We transport it into the extracellular fluid using a transporter that mediates the passive transport of the glucose, the sodium exits via a sodium-potassium pump. The cell is doing a 1

dynamic job within the more complex functionally of the human body. These proteins in the membrane have to be distributed in a certain way to allow us to bring about that function. The apical membrane has a different distribution than the basal membrane.

Distribution and Translocation of Proteins In order for that specific distribution to take place proteins have to be synthesised and then put in place, we have a number of mechanisms that carry this out. It is also necessary that differentiation takes place e.g. if something is required to be sent down the secretary pathway, we do this by tagging. For example, a precursor protein that has a signal sequence allowing it to bind to receptors on the mitochondria (TOM complex) and import it into the cell. Once translocated into the membrane the signal peptide is cleaved by signal peptidase, this is to avoid the functional confirmation until it’s where you need it. Tags allow the protein to get to where it needs to be but also stops it taking up its final appropriate functional confirmation.

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BK channel location and dynamics are relative to secretory vesicles. Botox Botox stops the transport of vesicle fusion by disrupting the interaction between target proteins- soluble NSF attachment protein receptors (SNARE) which would allow the normal fusion of vesicles containing transmitter. In this case it’s the vesicles containing transmitter which releases onto the muscles resulting in wrinkles.

- v-SNAREs are incorporated into the membranes of transport vesicles during budding - t-SNAREs are located in the membranes of target compartments Components of the Cytoskeleton

Intermediate filaments are rope-like consisting fibrous Actin filaments are helicalfibres polymers of actinof and are flexible. Actin intermediate filament proteins. They come in different types, some the highest filaments are dispersed all through the cell, however, forming meshwork and others extending acrossthe thelayer cytoplasm, giving abundance is seen in the cortex, of the cytoplasm just below mechanical strength and distributing mechanical stresses. They are the plasma membrane. very flexible with great tensile strength; under stress they deform but do not rupture.

Microtubules are hollow cylinders made of tubulin, they are long and straight. Typically, they have one end attached to a centrosome. With a larger outer diameter, they are more rigid than actin filaments or intermediate filaments and rupture when stretched.

Microtubule Organisation In the cytoplasm, microtubules grow from specialised centres called microtubule organising centres, MTOCs. These control the number, position, and orientation of microtubules in the cytoplasm. In animal cells, the major MTOC is the centrosome, usually found at one side of the cell nucleus.

Tissues 2: Epith PowerPoint Slide

Aims: - Categorise the morphological features of the 4 main classes of tissue - Compare characteristics of simple & stratified epithelial tissues Tissue Types - Connective Tissues for packaging or supporting fabric - Nervous Tissue such as nerve and glial cells - Muscle tissue generates force and produces movement - Epithelia are sheets of cells covering the body’s surface 4

Epithelium

It is a layer of cells that sits on a basement membrane, they sit right next to each other forming a tight cohesive sheet, you don’t want gaps as they protect surfaces. It can be found on internal and external surfaces, such as internal cavities and vessels. Glands are also formed from epithelium cells and can combine with nervous tissue to create special senses such as taste. Epithelium is described as highly cellular as they are densely packed with cells, due to them being in such close proximity they tend to bind physically to one another and the basement membrane. These binding sites are called adhesions/junctions. Not present in epithelial cells are blood vessels, they are avascular. Blood vessels are not needed as they are rather thin, and diffusion can take place easily. It is capable of regeneration as it is present in places with high levels of friction and where physical trauma takes places. It is derived from all 3 germinal layers – ectoderm, endoderm & mesoderm of the developing embryo.

An epithelial cell has structu surface is not attached to ot cavities. The lateral surface i attached to the basement m

nct cell surfaces. The free apical ning in the lumen of ducts and ial cells and the basal surface is ithelia to underlying tissues.

Apical Specialisations Microvilli are cytoplasmic protrusions/projections that form a brush border on the surface of the cell, they are often found on the epithelium that lines internal passages that are used for exchange, secretion and diffusion. They increase surface area. Stereocilia are similar to microvilli but are longer and are non-motile. They have a niche function and bend in response to sound waves, they are found in the inner ear’s sensory hair cells. 5

Cilia are motile softer hair-like protrusions, each cell has several hundred and they beat in coordination with each other to move substances over them. They can be found in respiratory epithelium and the fallopian tubes. Smokers are seen to have reduced cilia movement, this in turn impairs the movement of mucus and results in reduced protection against bacteria. Basolateral Specialisations These specialisations are at the basolateral surface between cells or with underlying basement membranes, they are called junctions. They maintain a polarised state within the cell, join cells together and exchange information and metabolites. Occluding/Tight junctions seal cells together and prevent leaking, they inhibit the passage of substances between cells. Many tight junctions are necessary in places where we don’t want lots of exchange such as the blood vessels in the brain, the stomach and intestine. Conversely, where exchange is needed such as in the kidneys there is a lack of them. Anchoring junctions mechanically attach cells to their neighbours, there is a great abundance of them in tissues exposed to serve stress such as skin and cardiac muscle. Zona adherens or desmosomes are strong junctions in the lateral domain and hemidesmosomes are in the basel domain. Communicating/Gap junctions are where chemical/electrical signals pass between cells.

Classification of Epithelia

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Simple Epithelial Simple squamous-

Simple cuboidal-

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Simple columnar-

Smoking results in the destruction of epithelium, in the bronchiole smoking causes the normal columnar to turn into squamous metaplasia. This alters the cells ability to bring about its function and is one of the causes of the lungs blackening and degrading. Stratified Epithelial Stratified squamous-

Stratified squamous epithelium can be classified as nonkeratinized or keratinized, based on outermost layer of cells. Nonkeratinized (moist) have a layer of fluid covering the outermost layers of the cells which makes them moist, they are found in the mouth, throat, larynx, oesophagus, anus and vagina. Keratinized are living cells in deepest layers outer layers containing keratin- dead. The tissue is dry, durable and moisture-resistant, it is found in the skin, gums and the hard palate of the mouth.

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Stratified cuboidal-

Stratified columnar-

Pseudostratified Columnar

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Transitional Epithelium This is a unique type of stratified epithelium that lines the bladder, ureters, pelvis of the kidney and the superior part of the urethra. It’s found in places where there is considerable expansion, it tolerates stretching and recoil without damage. The number of cell layers and cell shape varies depending on how stretched it is. When not stretched it is cuboidal or columnar, when stretched it is flattened or squamous. As stretching takes place, cells shift on one another, so the number of layers decrease from 5/6 to 2/3.

Tissues 3: Connective Tissue PowerPoint Slides

Aims: - Connective Tissue - is the most abundant and the most widely distributed of the tissues - Connective tissues perform a variety of functions including support and protection - Classify connective tissue types Connective Tissue Basics It is abundant and is widely distributed across the body and it makes up a part of every organ in the body. Connective tissue cells are separated from each other by extracellular matrix (ECM). They come in three main classes (with several subclasses) connective tissue proper, supporting connective tissue and fluid connective tissue. 10

They have multiple functions: Connection Support Enclosing/Protection Separation Cushioning/Insulation Storage Transportation

Tendons and Ligament Bones and Cartilage Capsules and Bones Sheaths Adipose Tissue Adipose Tissue Blood

Connective tissue can only be differentiated from the middle layer of the embryo- the mesoderm. This layer provides mesenchyme stem cells. Components of Connective Tissue- Cells Each major class of connective tissue has resident cells which create, maintain or breakdown the ECM. - “blasts’ CREATE the ECM - “cytes” MAINTAIN the ECM - “clasts” BREAKDOWN the ECM e.g. Osteoblasts - create bone Osteocytes - maintain bone Osteoclasts – break down bone

Chondroblasts - create cartilage Chondrocytes - maintain cartilage Chondroclasts - break down cartilage

Undifferentiated mesenchymal stem cells help with regeneration. 11

Components of Connective Tissue- ECM The ECM is very important as it fundamentally determines the properties of the connective tissue, depending on its properties it will allow connective tissue to bear weight and withstand tension or trauma. It isn’t just water; it contains ground substance and extracellular protein fibres. ECM is very useful in the creation of artificial tissue and organ regeneration, recellularizing an ECM scaffold with a patient’s own cells eliminates adverse immune responses and in turn makes it better than a donor heart. ECM: Ground Substance The ground substance is a gel-like substances that contains water and two main groups of soluble proteins. Cell adhesion proteins are the connective tissue gel, examples include fibronectin and osteonectin, all cell adhesion proteins’ names end in -nectin. Proteoglycans are macromolecules with a protein core to which glycosaminoglycans (GAGs) are attached. This arrangement of proteins provides high viscosity and low compressibility, the higher GAG content, the more viscous the fluid, high GAG counts are seen around the joints. ECM: Fibres The fibres of the connective tissue provide support and they come in three types collagen, elastic and reticular. Collagen fibre is the thickest and most abundant of the three, making up 6% of your body weight. Collagen fibres are created by fibroblasts. 3 chains of amino acids wind around each other forming a rope-like collagen molecule called tropocollagen in the ECM, this process requires vitamin C. Tropocollagen assembles into fibrils which are then bundled into thick collagen fibres.

There are 25 types of collagen depending on their amino acid combination. Type I is the most abundant, these include tendons and ligaments. Type II is found in cartilage and reticular fibres are mainly Type III.

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Elastic fibres contain elastin and are long and thin, they too are created by fibroblasts. They form branching networks in the ECM and are found in places where stretching recoil takes place (greater elasticity is needed) such as the lungs, blood vessel walls. Reticular fibres are short, fine fibres made up of Type III collagen. They branch extensively, forming networks that fill spaces between tissues and organs, e.g. the basement membrane of epithelial tissue and around capillaries. They allow more “give” than collagen fibres and are found in abundance in the liver, spleen and lymph nodes. Connective Tissue Classifications: Connective Tissue Proper Connective tissue proper comes in two type loose and dense, these are further subdivided loose into areolar, reticular or adipose and dense into regular collagenous, regular elastic, irregular collagenous and irregular elastic. A) Loose, fewer fibres more ground substance i) Areolar, fatty layer found under the dermis ii) Adipose, fat tissue iii) Reticular, found in lymph nodes and the spleen Scurvy develops when there is an abundance of defective collagen fibres, this is caused by the lack of vitamin C in the diet. Vitamin C is vital in the three amino acids forming tropocollagen. It leads to teeth falling out, the small blood vessels in the eye bursting and bleeding from the capillaries into the skin. B) Dense, more fibre less ground substance i) Regular collagenous, found in tendons ii) Regular elastic, found in vocal cords iii) Irregular collagenous, found in the dermis iv) Irregular elastic, found in the heart Marfan’s syndrome is a resultant of defective elastic fibres, it comes about when there is an abnormal production Fibrillin-1, as a result the elastic fibres become inefficient/weak and there is an overgrowth of tissues. Sufferers have an arm span greater than their height, tall stature, scoliosis, lens subluxation and mitral valve prolapse. The latter leads to the backflow of blood and the dilation of large arties that risk rupturing. Pulmonary emphysema is also caused by defective elastic fibres, an increase of elastase activity results in the destruction of elastic tissue. Excess elastase activity can be stimulated by air pollution and tobacco. Fibrosis (scar tissue formation) is the formation of excess fibrous connective tissue in an organ or tissue. Scarring is confluent fibrosis that obliterates the architecture of the underlying organ or tissue and scars cause the tissues to harden reducing flow of fluids through affected tissues.

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Connective Tissue Classification: Fluid Connective Tissue Bone marrow is in the soft spongy material in the central cavity of larger bones and small spaces of spongy bone. It produces all three types of blood cells- red, white and platelets as well as lymphocytes. Red bone marrow produces blood for the growth of the skull, vertebrae, ribs, sternum and the heads of long bones, whereas yellow bone marrow no longer produces blood. As we age, we see a decrease in red bone marrow as it is replaced by yellow bone marrow. Bone marrow diseases and blood cancers: LEUKAEMIA – high numbers of immature / abnormal WBC’s Symptoms – anaemia, reduced clotting, excess bruising, tiredness, increased infections LYMPHOMA – abnormal lymphocytes MYELOMA – abnormal plasma cells Treatments include radiotherapy, chemotherapy and bone marrow transplants.

Tissues 4: Nervous Tissue PowerPoint Slides

Aims: - Outline the organisation of the nervous system - Describe the properties of neurons and relate these to their function - Describe the categories and properties of glial cells, and outline their roles within the nervous system - Describe the etiopathology of some disorders of the nervous system Nervous System The nervous system (NS) is split up into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS contains the brain and the spinal cord, the PNS contains the cranial and spinal nerves as well as the ganglia. White matter is found in all of the nerves of the PNS and much of the interior of the brain and spinal cord, grey matter is found in clusters of neurons in the brain and spinal cords. Nervous tissue ether comes under neurones or glial cells, neurons consist of nerve cells that are the functional unit of the nervous system, they send signals around the body and are found all over the CNS and PNS. Glial cells are the support cells of the NS, they protect, provide nutrients and immune functions to the neurons.

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Neurons Neurons are irritable, meaning they have the capacity to react in a graded manner to physical or chemical stimuli. Receptors on the neuron allow them to be excited by stimuli form the outside (exteroceptors) or inside (interoceptors or proprioceptors). The flux of energy ether mechanical, thermal or chemical is transduced into electrical energy to create nerve impulses. They are conductive and have the ability to rapidly transmit excitation from

one place to another. Trains of impulses are created throughout neurons; they signal to nerve centres where they evoke additional patterns to activity in other nerve cells that result in sensations or motor responses. The cell body (soma) mirrors a ‘normal cells’ function and is the biosynthetic centre and receptive region. It contains a central nucleus and the usual organelles, however, is differentiated by Nissl bodies, these are clusters of free ribosomes and rough ER. Their cytoskeleton has neurofibrils with microtubules and neurofilaments. Unlike other cells it has no centrioles. Dendrites are the receivers of signals from axon terminals. They are highly branched like trees and are the location of synapses, the cytoplasm contains Nissl bodies, mitochondria and other organelles. Axons are long thin, cylindrical projections, the electoral impulse passes long the axon to stimulate synaptic transmission at the axon terminal. There is only one per neuron and can be up to one metre long, this length provides fast transmission like reflexes that bypass other chemical signals to respond quickly towards stimuli. They are specialised to conduct action potentials and contain mitochondria and cytoskeletal proteins. Glial Cells Neuroglia are ‘support’ cells to neurons, they are smaller however, are more numerous. They are not responsible for the conductivity of electrochemical signals and do not 15

propagate action potentials. They are determinates of the flow of signals through the neuronal circuit and modulate synaptic and non-synaptic transmission. Capable of division and multiplication, in disease or injury they multiple to fill spaces once occupied by neuronsthis is normally referred to as scarring of the NS. There are different neuroglial cells in the CNS and PNS: A) CNS i) Astrocytes ii) Microglia iii) Ependymal cells iv) Oligodendrocytes B) PNS i) Satellite cells ii) Schwann cells Astrocytes are named because of their star-shape and provide nutrients to neuron. They help maintain the chemical microenvironment in the blood brain barrier, however, are not exclusive to the blood brain barrier. They function also to...