HUMAN BIOLOGY 1
Chapter 13 & 15, Physiology part 4
1.Neurons work through two mechanisms production of an _dopamine___and release of _neurotransmitter__. Which of these two mechanismsmakes one neuron different from another?
Neurotransmitters are responsible for making a neuron different fromanother.
2.What is the basic function of a hormone? Generally speaking, what isthe stimulus for their production (look at the example in f 15.8,then try to form a general conclusion)?
Hormonesare involved in development and growth, reproduction and sexualdifferentiation, maintaining the internal environment, andmaintaining and controlling different activities in the body (Starr &McMillan, 2013). Hormones are stimulated by an imbalance in thedifferent body process, for example, the hormone insulin is boostedby the increase of glucose in the blood, this causes insulin to bereleased to convert glucose to glycogen for storage and thusbalancing glucose levels in the blood.
3.For the following conditions speculate whether the sympathetic orparasympathetic systems predominates.
drivingon the I290 Sympatheticnervous system
reading Parasympathetic nervoussystem
napping Parasympathetic nervoussystem
skiingon narrow, hilly trails in the woods Sympathetic nervous system
4.Suggest a biological property or function that might be affected bydisorders in the following endocrine organs. What hormone would beinvolved in each case?
Thyroid The thyroid secretestriiodothyronine, thyroxine and calcitonin hormones. Disorders causedby infection of the thyroid would lead to small rates of growth anddevelopment and a lack of regulation of metabolism.
Pancreas The pancreas secreteinsulin, glucagon, and somatostatin. The infection of the pancreaswould result in lowering or rise of blood sugar level and influencethe carbohydrate metabolism.
Adrenals Glucocorticoids, andmineralocorticoids are secreted by the cortex whereas epinephrine andnorepinephrine by the medulla. A deficit in the hormones would resultin both a great protein breakdown, glucose conversion, and sodiumreabsorption and the control of salt-water balance would be affected.
5.Do the following statements accurately describe principals of hormoneaction?
Hormonesoften interact with one another to produce an effect Yes, hormones usually associate with one another to yield a responseexcept in the case of blood sugar balance.
Hormonesare usually part of positive feedback loops Hormones are usually part of positive feedback, for example,oxytocin. There is maintenance of the concentration of hormones asthey affect the body. The positive hormonal feedback systems areimportant because they are involved in the constant monitoring andmaking adjustments in the body to keep hormone levels stable.
Hormoneshelp the body respond to environmental cues No, hormones respond to changes that occur inside the body of theorganism.
6. The following questions are based on f 13.2 and f 13.3.
Panela of f 13.2 depicts the “resting state” of a neuronal axon. Whatis the distribution of electrical charge across the membrane?
Accordingto panel a of figure 13.2, the membrane of the neuron is at rest.Hence, the resting potential is negative due to the accumulation ofsodium ions ( Na+ ) outside the cell is more than thepotassium ions (K+) inside the cell.
Panel b of figure 13.2 depicts an action potential after stimulationof a neuron. What is the key event in this panel? What is theeffect on the distribution of electrical charge across the membrane.
The key event is the opening of the sodium gates to allow the sodiumions to flow inside the neuron reducing the negativity inside. Thisresults to more gates opening until it reaches the voltage and themembrane reverses. The distribution of charge, therefore, graduallydecreases from positive on the outside of the neuron
Panela of f 13.3 shows the continuation of an action potential and thefirst step in the recovery of the membrane after an action potential. What is the recovery step? What is the effect on the distributionof electrical charge across the membrane? (Note: the legend for thisfigure is incorrect. You will need to base your answer on what yousee in the figure itself.)
Action potential takes places due to the change in the polarity whenthe axon hillock`s membrane potential reaches the threshold and movesalong the axon. More gated ion channels, therefore, become open,allowing more sodium ions inside the cell, and the cell graduallydepolarizes. The charges across the membrane completely reverse. Theoutside becomes negatively charged and inside of the cell becomespositively charged.
Panelb of f 13.3 shows the final step in recovery after an actionpotential. What is it?
Panel b of figure 13.3 depicts the neuron entering a refractoryperiod, which returns potassium ions to the inside of the celland sodium ions consequently to the outside of the cell.
Thesodium-potassium pump thus, moves the sodium+ ions to theoutside of the cell and +potassium ions to the inside,thereby restoring the neuron to its normal polarized state.
7.Examine f 15.2 carefully. Interpret the information in these figuresto fill in the table below. For column 1 use either “activatesgenes” or “activates enzymes” for column 2 use either “faster”or “slower” for column 3 use either “longer” or “shorter”. You should be able to explain your selections to me. For columns 2& 3 you will need to think carefully about the mechanisms in thefigure and draw your own conclusions.
Steroidsare hydrophobic hormones. Thus they will not be able to diffusethrough the plasma of the blood. They, therefore, have to betransported by carrier proteins to the target cells. On reaching thecell, diffusion through the plasma membrane of the cell is possible,and hence they bind to receptors on the cytoplasm. The steroidhormone goes to the nucleus where it regulates transcription. This iswhy the effects of steroid hormones have a slow response time andhave a longer response duration.
Peptide hormones, on the other hand, are hydrophilic hormones. Thusthey able to diffuse through the plasma of the blood, but not throughthe plasma membrane due to the lipid bilayer. The peptide hormonesattach to receptors on the cell surface and activate secondarymessengers. The secondary agents modify the activity of enzymes inthe cytoplasm. The peptide hormones do not regulate transcription(Starr & McMillan, 2013). Therefore the effects are immediate buthave a shorter response duration.
8.Nerve gas blocks the removal of acetylcholine from the synapsebetween motor neurons and skeletal muscle. Why does this lead tosuffocation?
Uponinhalation of nerve gas the neuromuscular signaling is interrupteddue to the inhibition of acetylcholine thus resulting in skeletalmuscle paralysis and eventual death from asphyxiation.
Chapter17 & 23, Development & Cancer
1.Development starts with a single cell, the zygote (fertilized egg). The billions of cells of the body are produced from the zygote bymitosis. What is the genetic process by which all these cellsdevelop specific functions?
Thegenetic process is through the various signaling pathways. Morphogensusually specify which type of cell will be generated at a particularanatomical location and direct the migration of cells and theirprocesses to their final destination (Starr & McMillan, 2013).Notch or Delta determines which cell fate the precursor cells willadopt and the transcription factors which activate or suppress genes.Receptor tyrosine kinases regulates cellular apoptosis,proliferation, and migration also the growth of new blood vessels andaxonal processes in the nervous system.
2.What are the fundamental biological and genetic problems with cancercells?
Cancer cells contain damaged DNA that is not apoptosized. Thisdamaged DNA and other factors give the cell an advantage of speed ofreplication more than healthy cells.
3.The body plan starts to take shape during gastrulation byestablishment of the three primary body layers- what are these layerscalled? Name an organ that forms from each of these three primarybody layers.
Endoderm-The inner layer which gives rise to the thyroid and parathyroidgland.
Mesoderm- The middle layer which gives rise to the cardiovascular system.
Ectoderm-The outermost layer which gives rise to the central and peripheralnervous system.
4.What is the difference between cell determination and celldifferentiation? Which process comes first as cells develop?
Cell determination is the progressive restriction of the cell’sdevelopmental potential thus the establishing the cell’sdevelopmental path (Starr & McMillan, 2013). Conversely, celldifferentiation is the process by which a less specialized cell turninto a more specialized cell.
Theprocess of cellular determination occurs prior the process ofcellular differentiation.
5.Describe two theories of aging. What’s the key difference betweenthem? Which would you say is a genetic theory?
The theory of programmed life span postulates that every type ofcell, tissue, and organ is like a clock that operates at its geneticpace. A study done by Hayflick revealed that cells duplicate theirchromosomes before dividing and telomeres made of DNA and proteinscap the chromosomes end. These telomeres keep the chromosome endsfrom unraveling. However, a small piece of each chromosome is lostwith each nuclear division and when a crux is left, the cell ceasesdividing and die. Germ cells and cancer cells are the only exceptionsas they make their telomerase thus go on dividing past the normallife span.
Thecumulative assaults hypothesis postulates that aging is the outcomeof cumulative damage both at the cellular and molecular levelgradually over an extended period. Several factors contribute to thistheory. Firstly, damage to DNA from environmental assaults and adecline in the repairing process of DNA have helped to aging. Thestructural changes resulting from the DNA damage disrupts enzyme andprotein synthesis required for normal life processes. Secondly,Werner`s syndrome, which is an aging disorder, which is brought aboutby harmful mutation caused by the gene that specifies a helicasewhich unwinds nucleotide strands causes affected people to age fastin their thirties and eventually die before the age of fifty.
Thedifference between the two hypotheses is that in the cumulativeassaults hypothesis, aging is the outcome of damage at the cellularor molecular level whereas in programmed life span theory the lifespan is genetically determined.
6.What is the most important difference between a tumor and cancer?
A tumor is a defined mass of tissue. These tissues may be cancerous(malignant tumor) or non-cancerous (benign tumor). The most obvioustrait between the cancerous tumors from the non-cancerous tumors isthat the malignant tumors invade the surrounding tissues throughmetastasizing via the bloodstream and the lymphatic system, whereasthe benign tumors expand in the same tissue do not invade thesurrounding tissue and they do not spread (Starr & McMillan,2013).
7.What are the causes of cancer? What is the common mechanism behindthese causes?
Some of the causes of cancer are the oncogene, faulty tumorsuppression genes, viral infections, carcinogens, radiation, andimpaired immunity (Starr & McMillan, 2013).
Oncogenes alter control of cell division whereas defective tumorsuppressor genes fail to halt runaway cell division. On the otherhand, viral infection switches pro-oncogene to oncogene it alsoinserts an oncogene into the host cell DNA. Lastly, bothe carcinogensand radiation damage the DNA structure and a faulty immunity fail toflag cancer cell for destruction.
8.How is the immune system implicated in cancer?
Cancer weakens the immune system thus rendering it ineffective. Forexample. Leukemia (cancer of blood cells) impairs the bone marrow`sability to produce blood cells, especially leukocytes, as efficientlyhence reduced immune cells to fight which leaves the body vulnerableto invasion of cancer cells. Also, cancer destroys the number of Tcells available for causing an amplified reaction against the foreignantigens. Therefore, the less the amplification cascade, the lowerthe effectiveness of the immune system.
9.Describe three life style choices that would have the greatest effectin reducing the risk of cancer. Explain your reasoning.
Avoiding tobacco is the first most important lifestyle choice inreducing the risk of cancer. Smoking is the primary cause of lungcancer, bladder cancer, and head and neck cancer as the carcinogenscontained in tobacco damage the cells lining the lungs. Secondly,observing a desirable weight is vital. Obesity predisposes overweightwomen to breast and womb cancers especially after menopause due tothe high estrogen levels which result in an uncontrolled celldivision. Lastly, alcohol causes a broad range of cancers includingmouth, throat, liver, breast, colon and rectum. The cancersassociated with alcohol intake result from a lowering of the body’sability to absorb folate from foodstuff, raising the level ofestrogen in the body and a defect in the gene for alcoholdehydrogenase that breaks down ethanol. Therefore, observing analcohol-free life is more expedient than risking.
10.Chemotherapy works against cells that
Chemotherapy works against dividing cells by disrupting DNAreplication during the S phase of the cell cycle or by restrictingthe formation of spindle fibers.
11.When cells differentiate they develop specific structures andfunctions. What type of biological molecule do cells need to produceto develop specific functions (see chapter 2)?
Gene expression causes cell differentiation. Genes may be expressedor suppressed. The expression and suppression of genes is determinedby what signals the cell gets.
12.Chemotherapy patients typically suffer from nausea, anemia, and aweaker immune response. What tissues underlie these symptoms (seechapter 4)? What is the common link between these tissues?
Chemotherapy damages the genes inside the nucleus of cells. Chemotherapeutic process damages the bone marrow, thus limiting thesynthesis of erythrocytes which predisposes one to the risk ofanemia. All the tissues that are most targeted by anemia are usuallyendothelial tissues as they divide and replace themselves more oftenthan most tissues.
13.Speculate on why epithelial tissues (see chapter 4) are commonsources of cancer.
Epithelial tissues are made up of cells that cover body surfaces andform glands that are developmentally resulting from the bodysurfaces. The epithelial cells retain the potential to undergomitosis, and new epithelial cells can quickly replace the old ones.The cells that undergo an abnormal division become cancerous andthus, just as epithelial cells, they spread faster as the surroundingepithelial cells have microscopic extracellular matrix between themmaking the cancerous cells move migrate to other healthy body cellsfaster. This ability to undergo mitosis and a more rapid replacementof body lining cells make the cells a common source of cancer asexcess division might result in mutations which consecutively, havethe potential of becoming cancerous
1.In simplest terms what does evolutionary theory state about theliving world?
Thetheory reveals how the living world is always changing.
2.Define evolution in genetic terms.
Theevolution occurs when remarkable changes occur in the relativefrequency of alleles over time in a population.
3.What is natural selection?
Thisis the tendency of the best-adapted organisms to survive in theirenvironment and produce offsprings while the less-suited organismsget eliminated over time (Starr & McMillan, 2013).
4.Natural selection occurs because there is competition betweenorganisms for survival and reproduction. What factor gives rise tocompetition?
Thedesire to acquire a living space sparks competition in situationswhere there is limited space (Starr & McMillan, 2013). Often,organisms compete for food especially when there is limitedavailability. Moreover, organisms compete for mates. Therefore, theweak have limited chances to mate and are gradually eliminated.
5.Why is genetic variability in a population of similar creaturesimportant, according to the theory of natural selection?
Geneticvariation is beneficial to the members of a population since itenables the members to survive in different environmental conditions.Moreover, a high genetic diversity makes the members of thepopulation less susceptible to diseases due to the varied resistance.Therefore, genetic variation among members of a population isnecessary for their survival.
6. Abird’s wing, dog’s leg, and human arm all have differentfunctions but similar internal structures, what is thisrelationship called? What does the similarity imply?
Therelationship is Morphological divergence (Starr & McMillan,2013). The homologous structures are similar in a way since theyshare a common ancestor. The structures perform differentiatedfunctions such as grasping in humans, flight in birds and walking indogs.
7.Circle the sentence that best summarizes natural selection.
a.Natural selection produces ever greater “perfection” oforganisms.
b.Natural selection produces organisms adapted to an environmentalcontext.
8.What genetic processes give rise to genetic variations (refer back tochapters 19, 20)?
Mutationis capable of bringing about genetic variation once the mutated genesbecome transferred to transferred to the offspring (Starr &McMillan, 2013).
Across-over between chromosome during meiosis causes a variation inthe genetic composition. During this process, genetic content istransferred between the two chromosomes leading to genetic variation.
9.Imagine a disease wipes out most of the population and only a fewindividuals survive. What problem does that population face in termsof evolving and adapting to changes in the environment?
Limitedgenetic variationis characterizes the population such that asignificant proportion of the population has traits that are lessresistant to diseases (Starr & McMillan, 2013). In other words,natural selection has not taken root such that the individuals failto adapt to the environment.
10.Can you think of any examples of evolution evident over a shortperiod?
ThePlasmodium species have evolved to become drug resistant.
Starr,C., & McMillan, B. (2013). Human biology. CengageLearning.
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