HUBS 191 FINAL EXAM ACTUAL QUESTIONS AND CORRECT ANSWERS WITH COMPLETE SOLUTION. 2024/2025

HUBS 191 FINAL EXAM ACTUAL QUESTIONS AND CORRECT ANSWERS WITH COMPLETE SOLUTION. 2024/2025 Name the four basic types of tissue Connective tissue, epithelial tissue, muscle tissue and nervous tissue. Why do the four types of tissues have different structures and function? They are made up of different kinds of cells. They have different things that make up the extracellular matrix. They have varying amounts of extracellular matrix. Types of connective tissue Connective tissue proper - Loose connective tissue which keeps organs and epithelia in place. - Dense connective tissue forms ligaments and tendons. - Adipose tissue (fat) and reticular connective tissue (support lymph organs like the lymph nodes) Specialised connective tissue - Blood, bone and cartilage Main role of connective tissue - Transport substances - Provide support and structure Features of epithelial tissue - Tightly packed cells - Little extracellular matrix - Forms skin and lines internal cavities - Many glands are made of epithelial tissue Features of muscle tissue - Cells are stretched or fibre-like - Main role is contraction - Allows body and its organs to move - Cardiac muscle, skeletal muscle, smooth muscle. Nervous Tissue - Made up of neurons (conduct messages) and glia (support and protect nervous system) - Main role is to transmit electrical signals allowing for communication and coordination. Cells only survive if the following conditions are meet - Enough nutrients - Correct temprature - Correct pH - Can only tolerate smal amounts of toxic substance and waste. This is why maintaining a constant internal environment (homeostasis) is so important, along with exchange of nutrients and wast across the cell membrane. Total body fluid numbers to memorise 2/3 of total body fluid is intracellular fluid (ICF) 1/3 of total body fluid is extracellular fluid (ECF) 4/5 or 80% of extracellular fluid is interstitial fluid (between cells). 1/5 or 20% of extracellular fluid is plasma (50% of total blood volume). What are transcellular fluids? ECF also includes various 'transcellular fluids' contained within epithelial lined spaces e.g. synovial fluid in joints, ocular fluid in the eye, cerebrospinal fluid What does a unicellular organism depend on its immediate environment to provide? Nutrients Solute concentration Temperature pH Toxins (including own wastes) Lack of Predators This limits the environment a unicellular organism is able to survive. What is 'milieu interieur' Claude Bernard () recognised the importance of the body's internal environment or extracellular fluid. The constancy of the internal environment is the condition for a free and independent life. How did Walter Bradford Cannon () define homeostasis? The maintenance of relatively constant conditions in the internal environment (ECF) in the face of external (or internal) change. 1. In our bodies there are mechanisms that act to maintain constancy. 2. Any tendency toward change automatically meets with factors that resist change. 3. There are co-operating mechanisms which act simultaneously or successively to maintain homeostasis 4. Homeostasis does not occur by chance, but is the result of organised self-government. Normal concentration of sodium (Na+) in the ECF and why it needs to be controlled. Normal concentration in ECF is about 135 - 145 mmol/L. Main extracellular cation. Largely determines extracellular fluid volume so also influences blood pressure (BP). Important in action potential generation in nerve and muscle tissue. Normal concentration of calcium (Ca+) in the ECF and why it needs to be controlled. Normal total plasma conc. is about 2.2 - 2.6 mmol/L. Important structural component of bone and teeth. Involved in neurotransmission and muscle contraction. Essential for blood clotting. Regulates enzyme function. Normal concentration of potassium (K+) in the ECF and why it needs to be controlled. Normal concentration in ECF is about 3.5 - 5 mmol/L. Most abundant intracellular cation. Main determinant of the resting membrane potential (RMP). Particularly important in excitable tissue i.e. nerve and muscle. Normal concentration of glucose in the ECF and why it needs to be controlled. Normal fasHng glucose concentration ≈ 3.5 - 6 mmol/L. Non fasting (random) ≈ 3.5 - 8 mmol/L Used by cells (especially neurons) to produce adenosine triphosphate (ATP). Neurons particularly affected by low glucose levels. High blood glucose causes other problems both acute and chronic. Normal pH range and conditions that result in pH being outside of the normal range. Normal pH range is 7.35 - 7.45. Acidosis is when pH is too low (acidic), decreased neuronal function and decreased level of consciousness. Alkalosis is when pH is too high (basic), over excitability of nerve and muscle tissue. Goes from 'pins and needles' → muscle spasms → convulsions. Typical core body temperature 'Core' Body Temperature is generally maintained between 36 to 37.5 C which allows for optimal metabolic and physiological functioning. Oral and axillary temperatures are usually about 0.5 C less than rectal (core). 'Peripheral temperature' is more variable. Core Body Temperature - Why is it so important? At higher temperatures proteins start to denature. At lower temperatures, chemical reactions slow down, preventing normal cell function. As cells of the nervous system become compromised, the ability to thermoregulate is lost. Rapid worsening of the initial condition and accelerated movement of temperature away from normal leading toward death. This is an example of a viscous cycle and a detrimental positive feedback loop. Diffusion Diffusion results from the random movement of individual molecules as a consequence of their thermal energy. Distance travelled is proportional to the square root of time - It takes four times as long to diffuse twice as far OR, quarter of the time to diffuse half the distance. Diffusion is therefore very rapid over the short distances within cells and between cells and capillaries. What substances are able to diffuse directly through the lipid bilayer of our cells from regions of high to low concentration (down their concentration gradient)? Oxygen Carbon dioxide Steroid hormones Anaesthetic agents Such diffusion is passive because the net direction of movement is 'downhill' and so requires no energy input from the body. Many other substances (because of their size or physiochemical properties) are not able to 'dissolve' in the lipid bilayer. How do they cross? Water diffuses through protein channels known as aquaporins. There are specific channels for many ions e.g. K+, Na+ and Ca++ Types of membrane channels used in simple diffusion Channels are usually specific and may be open/close spontaneously (leak channels) or in response to various stimuli e.g. chemicals (ligand gated), change in membrane potential (voltage gated). Carrier Mediated Passive Transport is also known as facilitated diffusion, what is this process? Substance binds to carrier on one side of the membrane which induces the carrier to change shape and release of substance to the other side. ("Downhill" i.e. down conc. gradient). For example, glucose entry into cells when insulin is present. Passive vs Active transport Passive transport moves molecules down their concentration gradient and requires no energy whereas active transport moves molecules against their concentration gradient and requirers energy. Primary Active Transport description, example and function. Energy from the hydrolysis of ATP used to move substances against their concentration gradient. e.g. The sodium-potassium pump which moves 3 Na+ out of the cell in exchange for 2 K+. - maintains ionic gradients - helps regulate cell volume Exocytosis and Endocytosis Substances transported out of (or into) the cell in membranous (bilayer) vesicles. Physiological examples: - Secretion of insulin by β cells of pancreas (exocytosis) - Phagocytosis of microbes by neutrophils (endocytosis) What is osmosis? Osmosis is the net movement of water across a membrane down its own concentration gradient (or toward the region of higher solute concentration). Differences in solute concentration across cell membranes can cause fluid shifts and create pressure that can damage cells. What is osmolarity and normal osmolarity in ECF and ICF. Osmolarity is a measure of the total number of solute particles per litre of solution. Units are osmol/L or mosmol/L. Normally 275-300 mosmol/L in ECF and ICF. What is tonicity and the three types of solutions? Tonicity specifically refers to the effect that a solution has on cell volume. HYPER tonic solutions will cause cells to SHRINK HYPO tonic solutions will cause cells to SWELL ISO tonic solutions cause NO CHANGE in cell volume Osmolarity vs Tonicity Osmolarity is a property of a particular solution (independent of any membrane). Tonicity is a property of a solution with reference to a specific membrane. If the osmolarity of one compartment changes what happens? Use an example. Water will diffuse by osmosis until equilibrium has been restored. For example, intravenous distilled water would 'dilute' the plasma and cause water to move firstly to the interstitial compartment, then the ICF until equilibrium reached. Clinical solutions should not produce unwanted fluid shifts! Calculate the osmolarity of a 0.9% solution of sodium chloride (normal saline) and consider how it would affect the volume of a red blood cell. 0.9% sodium chloride means 0.9 g of NaCl in 100 ml = 9g of NaCl in 1000ml = 9g/L But, this does not tell us anything about the number of particles present. We need to know how many mol (6.022 x 10^23 particles) 9g of NaCl represents. We know that a mole of a substance is its relative molecular mass (MR) in grams. MR of NaCl = 23+35.5 = 58.5g. So 58.5 g of NaCl would contain 6.022 x 10^23 particles. But, we have only got 9g of NaCl per litre - how many mol does this represent? 9 g/L ÷ 58 g/mol = 0.154 mol/L or 154 mmol/L. This is the concentration of NaCl but we need to be aware that NaCl is ionic and so will dissociate in water to give 2 separate particles ie. NaCl → Na+ and Cl- So, the osmolarity (total number of solute particles) will be double the sodium chloride concentration and different units i.e 308 mosmol/L. How will this affect cell volume? i.e. what is the TONICITY of this solution? The osmolarity of our intracellular (and extracellular) fluid is normally between 275-300 mosmol/L. Normal Saline @ 308 mosmol/L is pretty close to this and so in practice will not cause significant changes in cell volume. Also, the effective osmolarity is slightly less than calculated due to 'non-ideal' behavior of solute particles. Normal saline is therefore frequently used in a variety of clinical settings. It is essentially ISO- OSMOTIC and ISOTONIC. However, you need to appreciate that some substances can cross the cell membrane much more easily than sodium and chloride so they could be ISOSMOTIC but not ISOTONIC. Remember that charged ions like Na+ and Cl- Don't readily cross the cell membrane (unless specific channels are opened). A 300 mmol/L solution of urea has approximately the same concentration of solute particles as our body fluids (isosmotic) but it is not ISOTONIC - Why? Is it ISO-osmotic? YES, urea does not dissociate in water and remains a single molecule so concentration = osmolarity but different units (300 mosmol/L) Is it iso-tonic? - NO - Why not?? 1. Urea is able to diffuse across the cell membrane via urea transporters 2. There is not much urea inside the cell. This solution is therefore HYPOtonic because its effect on cells is to cause them to swell. Resting Membrane Potential (RMP) RMP refers to the fact that the inside of the cell membrane is negatively charged compared to its external surface. The magnitude of this negativity is typically about -70 millivolts (mV). This assumes the the outside of the membrane is taken as zero mV. The RMP results from the separation of a small number of oppositely charged ions across the lipid bilayer. Overall concentrations of ions in the ICF and ECF are not significantly affected! The resting membrane potential is an electrical potential that exists across the cell membrane and is due to different of ions on each side of the membrane and their respective permeabilites to it. The cell membrane is normally much more permeable to K+ than other ions and so K+ is the major determinant of the RMP Consider a hypothetical cell with ICF [K+] = 150 mmol/L and ECF [K+]= 4mmol/L (assume that no membrane potential initially exists). What will happen over time?? When the amount of K+ leaving the cell down its conc. gradient is balanced by that moving back in due to the electrical gradient we have the RMP. Why is it very important to control ECF [K+]? For most cells the membrane potential remains constant over time i.e. around -70mV. However, for 'excitable' tissues (i.e. nerve and muscle) the membrane potential must change in order for them to function. This usually occurs via the opening or closing of specific channels. Because K+ is the major determinant of the RMP it is very important to control ECF