Significance of Autonomic Nervous System to Psychologists

                        

Significance of Autonomic Nervous System to Psychologists

The complex human nervous system is divided broadly into two major parts based upon the location of the nervous tissue. The central nervous system (CNS) is the first part which has a centrally located nervous tissue and consists of the brain and the spinal cord. The second part is the peripheral nervous system (PNS) which includes the remaining nervous tissue of the body. The PNS contains 12 pairs of cranial nerves and their branches which arise from the brain stem and 31 pairs of spinal nerves which transmit messages between the spinal cord and the body. The nerves which form a part of the PNS can transmit messages to the CNS, and send instructions from CNS to the end organs like muscles and glands. The peripheral nervous system is further divided into two sub systems which are the somatic nervous system and the autonomic nervous system (ANS). Out of the two, the ANS controls some of the vital involuntary jobs like maintenance of homeostasis, digestion, breathing, maintenance of posture, etc, which are not noticed by us (The Nervous System (Chapter 11), n.d.). This article provides information about the components of the somatic nervous system and autonomic nervous system.

The Somatic Nervous System

This system consists of nerves which carry sensory information from skin to the CNS and instructions from the CNS to the end organs like skeletal muscles and sensory receptors located in the head and extremities.

Sensory neurons. They are the afferent neurons which carry information from the receptors present on the skin to the brain or the spinal cord. They have short axon and long dendrites (which bring information to the cell body) and the cell body is located in the dorsal root ganglion.

Motor neurons. They are the efferent neurons which carry messages from the brain and the spinal cord to muscles and other end organs. These neurons contain long axons and short dendrites. The cell body and the dendrites are located in the spinal cord, whereas the axon lies outside to the spinal cord. One motor neuron can be connected to many muscle fibers through collateral branches of the axon forming a “motor unit” (Swenson, 2006) (The Human Nervous System, 2004).

Interneurons are the third type of neurons which transmit the messages from the sensory neurons to the motor neurons. Upon activation of the sensory receptors, the sensory information gets carried by the sensory neurons to the CNS where it synapses to the interneurons, which in turn synapse on motor neurons. Finally, the motor neurons carry the instructions to the effectors organs like muscles, which respond by contracting. This simple monosynaptic pathway involving the flow of information is known as the reflex arc (The Human Nervous System, 2004).

The Autonomic Nervous System

John Langley was the first person to give the name “autonomic nervous system” to the complex network of peripheral nerves and ganglia which control the functioning of the smooth muscles and the glands of the viscera. This involuntary control system can regulate the functioning of the cardiac and smooth muscles and control the glandular secretions (Berntson, Sarter, & Cacioppo, n.d.). The somatic nervous system helps in connecting the external sensory organs to muscles through brain whereas, ANS controls the direct connection between the visceral organs/glands and brain or the spinal cord. ANS is controlled by the hypothalamus and medulla oblongata, containing neurons bundled together with somatic system neurons in the spinal and cranial nerves. ANS consists of two main divisions which work in opposition to each other while regulating the involuntary processes of the body and they are the sympathetic and the parasympathetic nervous systems (The Nervous System (Chapter 11), n.d.).

The Sympathetic Nervous System (SNS)

The primary function of this system is to mobilize the body during stressful situations to generate fight-or-flight response. The central origin of this system lies in the thoracic and lumbar regions of the spinal cord, hence is considered to have a thoracolumbar outflow. The neurons of this system release a neurotransmitter known as norepinephrine, which can excite its target muscles as a part of neuronal response. These nerves can also trigger the adrenal glands stimulating the release of hormones, epinephrine and norepinephrine during stressful situation under hormonal response. This system raises precise organ specific reactions. For example, during a situation of emergency, it stimulates the acceleration of the heart rate, constriction of blood vessels, increase in blood pressure, etc. These activities meet the demand for extra energy by the skeletal muscles. But a few other processes which are not immediately required under stress are suppressed. For example, digestion takes place at a slower rate; sphincter controlling the bladder gets constricted, etc (The Nervous System (Chapter 11), n.d.). The neurotransmitter acetylcholine is released by the preganglionic sympathetic neurons which stimulates the action potential in the postganglionic neurons. However, the final transmission of messages to the end organs through the sympathetic nerves takes place in the presence of norepinephrine released by the postganglionic neurons. This system maintains a bidirectional flow of messages and controls various internal organs like heart, blood vessels, lungs, eyes, kidney, sweat glands, penis and the digestive system. Sensations like heat, cold and pain are felt through this system. Disorders in sympathetic nervous system can lead to symptoms like slurred speech, headache, hypertension, loss of muscle strength, breathing problems, etc. It generally counteracts the parasympathetic nervous system. The diseases caused by the malfunctioning of SNS are sympathicotonia, complex regional pain syndrome or reflex sympathetic dystrophy syndrome, fibromyalgia, Parkinson’s disease and diabetic neuropathy. (Berntson, Sarter, & Cacioppo, n.d.) (Sympathetic Nervous System & All About It, n.d.). Some drugs like Caffeine can stimulate the SNS.

The Parasympathetic Nervous System (PNS)

This system gets activated when the body is in a resting state. The main purpose of this system is to restore and conserve energy. It allows the body to recover from a stressful situation as it stimulates the release of endorphins, a hormone that is called “feel good” hormone. This system stimulates the rest-and-digest response. PNS consists of 4 cranial nerves originating from the brain stem. PNS is also termed as craniosacral branch as its activity originates within the head to the sacral region. PNS also contains peripheral ganglia similar to SNS, but they do not get collected into coherent ganglionic chains. Instead, they lie near the visceral organs. Hence PNS is considered to raise a more localized response. Vagus nerve is mostly involved in the PNS activity. The afferent fibers of the vagus nerve convey the stimuli associated with the entry of food into the stomach to the vagus in the brain (which acts like a command station or nucleus). Later, the efferent fibers of the vagus nerve convey the messages from the brain to stomach to stimulate digestion. Both preganglionic neurons and post ganglionic neurons of PNS release the neurotransmitter, acetylcholine. PNS antagonizes the action of SNS and performs functions like lowering the heart rate, decreasing the blood pressure, constriction of the pupils, promotion of the digestion of food and functioning of the reproductive organs by dilating the blood vessels reaching the genitals (Berntson, Sarter, & Cacioppo, n.d.) (Sympathetic Nervous System & All About It, n.d.)

Opposing Versus Synergistic Actions of SNS and PNS

Many visceral organs are innervated by both PNS and SNS branches which are opposing in their actions. For example, sympathetic nerves stimulate the β-adrenergic receptors and increase the heart rate whereas, acetylcholine is released due to parasympathetic innervation, which acts on muscarinic receptors situated on the SA (sinoatrial node) and stimulates the lowering down of the heart rate. A perfect balance between these two systems leads to a balanced autonomic control of the target organs. These two systems perform synergistic action in some organs. For example, co-activation of sympathetic system along with parasympathetic system stimulates the salivary secretions when we eat something potentially noxious, like hot chilies. Even the penile erection and ejaculation requires the co-activation of both the systems (Berntson, Sarter, & Cacioppo, n.d.).

Conclusion

Changes in the activities of ANS can lead to diseases. Examining of the ANS is of special significance to psychologists, as ANS responses can be correlated with shifts in emotion, motivation, preferences and attention. They may also be linked to mental and physical health vulnerabilities. Autonomic nervous system responses can be measured with the help of electrodermal activity (EDA) (which measures the responses in the eccrine sweat glands), Electrocardiogram (ECG) (which measures the electric signal produced by the heart), impedance cardiography (which estimates the blood flow changes in the heart) and blood pressure detecting devices (Mendes, n.d.). ANS helps the body to respond to different stimuli and recover from it with time. A perfect functioning of the ANS is very essential for the maintenance of our day-to-day life.

References 

Berntson, G, G., Sarter, M., Cacioppo, T, J. (n.d.). Autonomic nervous sytem. Retrieved July 12, 2013, from http://psychology.uchicago.edu/people/faculty/cacioppo/jtcreprints/bsc.ans.03.pdf

Mendes, B,W. (n.d). Autonomic Nervous System. Retrieved July 12, 2013, from http://www.wendyberrymendes.com/cms/uploads/Mendes%20-%20Autonomic%20nervous%20sys.pdf

Swenson, R. (2006). Chapter 3 - Peripheral nervous system. Dartmouth.edu. Retrieved July 12, 2013, from http://www.dartmouth.edu/~rswenson/NeuroSci/chapter_3.html

Sympathetic Nervous System & All About It. (n.d.). Retrieved July 12, 2013, from http://www.sympatheticnervoussystem.net/

The Nervous System (Chapter 11). (n.d.). Retrieved July 12, 2013, from http://highered.mcgraw-hill.com/sites/dl/free/0070960526/323541/mhriib_ch11.pdf

The Human Nervous System. (2004). Biologymad.com. Retrieved July 12, 2013, from http://www.biologymad.com/nervoussystem/nervoussystemintro.htm

 

 

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How Does DNA Help To Solve Crimes?

 

How Does DNA Help To Solve Crimes?

 

Forensic science, alternatively known as legal medicine in many countries, aims to help the jury members to solve both criminal and civil cases. Advancements in the technologies of analysis of DNA have revolutionized this discipline of science. DNA or the Deoxyribonucleic acid is universally present in all the living beings. DNA is also known as the genetic blue print, as it stores information about an individual’s entire genetic makeup. It determines the physical features of an individual and various other attributes. This information stored in the DNA gets passed down from one generation to another. The unique nature of DNA in each individual (except identical twins) makes it to act as a powerful tool for law enforcement investigations. Apart from this, it can be extracted from various sources like blood, teeth, saliva, semen, hair, etc. DNA extracted from biological specimen acts as a lead to the investigators, especially in cases where there is no eyewitness (Butler, 2005). It is a very powerful tool, as the evidence collected form the scene of crime can be used as evidence even after decades, if it is properly preserved (Hart, 2002). Selected DNA sequences, called loci, are used to create a crime profile in the crime laboratory, which is later used for the identification of the suspect. Currently, DNA evidence is used to resolve criminal cases in two ways. Firstly, if the culprit is known, the DNA obtained from the crime scene can be matched with that of the culprit to establish that the culprit is involved/not involved, in the crime. Secondly, in cases where the suspect is unknown, the DNA obtained from the scene is matched with offender profiles obtained from the existing DNA databases. This helps to identify the culprit. This technology helps to link the evidence obtained from one crime scene with another, so that the same criminal responsible for both the crimes can be identified (James, 2012).

History of the Evolution of DNA Technology in Forensic Science

A forensic geneticist aims to identify the source of the biological specimen with high accuracy. Since the discovery of the human ABO blood group polymorphism by Landsteiner, it has been used to solve criminal cases. The main limitation of this system was that it can be used to prove an exclusion (that the specimen did not come from a particular individual), but cannot be used to ascertain the exact source of the material. Serological and protein electrophoretic methods were the only methods available till 1980s and the diversity in blood groups and polymorphic proteins were the only markers studied.

The application of DNA in forensic science began after the discovery of DNA fingerprinting by Alec Jefferies in 1984 (The History of DNA, n.d.). Detection of hypervariable loci, known as “minisatellites”, through hybridization of probes, increased the chances of finding an exact match. During the same period, differential lysis method, which enriches the sperm concentration in the vaginal fluid or semen mixture, was developed. This method facilitated the access of investigators to a surplus of suspect’s DNA, especially in the cases of rape. DNA fingerprinting technology was helpful in solving many paternity cases and criminal cases for some years. Later on, the focus shifted to the use of single-locus probes (SLPs), wherein each probe targeted a single, highly polymorphic, RFLP, making the interpretation highly specific. Development of PCR (polymerase chain reaction) methods in 1988 was another break through achievement, in the field of forensic science. Discovery of PCR technology which enables the rapid multiplication of a small fragment of DNA, made the analysis of minute quantities of degraded DNA possible. PCR based methods are currently widely used for all forensic DNA typing (Jobling and Gill, 2004). The practical application of DNA as an evidence was first noticed in 1987, when UK forensic investigators solved the ‘Black Pad’ murders and identified Colin Pitchfork as a killer. The launch of the national DNA database by FBI in 1998 was another major achievement (The History of DNA, n.d.).

 

Advancements in DNA Technology and Increased Forensic Applications

Since the discovery of polymorphism in certain areas of DNA (polymorphism is a character of DNA which means certain areas of DNA take different forms in different individuals), by Alec Jeffreys, these variable areas were used to differentiate one individual from another. Forensically important polymorphism is noticed in the non-expressed or junk DNA. The DNA present in the non-coding region of DNA exhibits high variability in length, as certain base sequences are repeated several times within these regions (Lyle, n.d.). Initially, only restriction fragment length polymorphism (RFLP) technology was used to solve forensic cases. In this technology, enzymes known as “restriction endonucleases” were used to cut DNA in a specific pattern. DNA fragments of variable lengths were generated due to the presence or absence of certain recognition sites in DNA tested. However, this technology is not widely used currently, as large quantity of DNA required for testing may not be available or degradation of the sample due to environmental factors may have rendered the DNA unfit for RFLP analysis. The newer technological advancements in DNA analysis have proven to be more efficient in solving cases (Hart, 2002).

STR analysis- Currently, a forensic scientist generally looks for two kinds of repeats, which are, variable number tandem repeats (VNTRs) or short tandem repeats (STRs). VNTRs are hundreds of base-pairs long and repeat along the length of the DNA. The number of repeats of these sequences differs from one person to another. STRs are very short, usually three to seven base-pairs long, which repeat in a fragment of DNA as long as 400 bases. Hence, STRs can be used to analyze very short fragments of DNA including those obtained from degraded samples (Lyle, n.d.). Federal Bureau of Investigation (FBI) has identified 13 specific STR loci and the chances of finding two different individuals (except identical twins) with same 13-loci DNA profile are very low (one in one billion). These 13 specific STR loci are universally used by all the forensic laboratories so that a uniform DNA database can be established across different regions (Hart, 2002).

PCR analysis - Minute quantities of DNA obtained as biological evidence can be enhanced using PCR as it produces exact copies of DNA present in the evidence. It does not affect the original sample during this process. As it has the potency to replicate very minute quantities of DNA, this technology can be used to multiply degraded samples obtained from the crime scene. However, care should be taken while collecting and preserving the sample as this technique can multiply the DNA of unwanted contaminants also (Hart, 2002).

Mitochondrial DNA analysis - Evidences which cannot be analyzed through RFLP or STR are subjected to mitochondrial DNA analysis. Evidences like hair shaft, bones or teeth lack nucleated cells; hence DNA obtained from mitochondria is used for analysis as STR, and PCR can multiply the DNA obtained from the nucleus. The limitation of this technology is that, all the maternal relatives have identical mitochondrial DNA, hence making the investigation difficult. However, the other supporting evidences obtained can help to solve the cases.

Y- Chromosome analysis -  Y-chromosome contains many genetic markers which can be used for forensic purposes. Analysis of these markers targets only the male suspects and it can prove to be a very valuable technique especially when the evidence contains a complex mixture containing the contributions from two or more male individuals. It can be used to trace family relationships amongst males, as the Y chromosome gets directly transmitted from father to sons.

A cooperative effort of police and crime laboratories will help to decide which method will suit better for a case.

 

Steps Involved In DNA Aided Investigation

FBI was authorized by Federal law to maintain a national DNA database, that is, National DNA Index System (NDIS), which works along with Combined DNA Index System (CODIS) software. Initially NDIS started with 9 participating states, but later it extended to almost 50 participating states (The FBI and DNA, 2011).

Collection of DNA samples - In order to establish such large database containing over 10 million DNA profiles, the first step is to obtain DNA samples legally. DNA sample can be acquired through any of the four fundamental legal strategies.

Voluntary - The suspects are asked to undergo DNA analysis voluntarily. Earlier, blood was drawn, but now-a-days buccal swab obtained from a tooth brush is used for analysis.

Court order - Depending upon the case, the court determines whether it is necessary to authorize a law enforcement agency to collect DNA sample from a particular suspect.

Law - Collection of a DNA sample from a defined group of individuals, like a group of arrestees or offenders, is made mandatory by the statute. This authorization is given when it is felt that the DNA samples of these criminals should be kept in a permanent record, that is, State or national DNA database.

Abandonment - The suspect himself handovers an item which contains his DNA sample during crime, unknowingly. For example, the suspect drinks beer and leaves the glass (Dale, Greenspan, and Orokos, 2006).

          Storage of DNA profiles - The obtained DNA sample is subjected to the DNA analysis techniques mentioned above to achieve a DNA profile, which is just a series of numbers. Specific identification markers on the individuals DNA decide the numbers of the DNA profile (The FBI and DNA, 2011). These DNA profiles of different offenders are collected in a DNA database which is maintained by every state of the nation. The DNA databases can be maintained at three hierarchical levels, that is, local, state and national levels. The profiles obtained from the local cases are entered into the local databases (LDIS) and also recorded in the state level database (SDIS). A DNA profile obtained from a recent scene of crime may or may not match with DNA records obtained from the state level database. Hence, the state level information is uploaded into NDIS (national level database) on a weekly basis (The FBI and DNA, 2011).

Use of CODIS software - CODIS is a computer software which allows the law enforcement crime laboratories at national and state levels, to compare DNA profiles obtained from the crime scene with that of the profiles obtained from convicted offenders, electronically. Many criminals show recidivist nature and have a tendency to get involved in cases of sexual assault and burglary repeatedly. Hence, there is a high chance of existence of the DNA profile of such criminal in the database and can be used to match through CODIS (Hart, 2002). CODIS can be used to link one crime scene with another and can be helpful in identifying serial offenders. CODIS operates at three hierarchical levels, which are, local, state and national levels (Hart, 2002). Only criminal justice agencies meant for enforcement of law and identification of criminals, are authorized to use CODIS according to the federal law. The information in the database is not associated with any personal identifiers like name, date of birth, etc, to ensure that perfect confidentiality is maintained (The FBI and DNA, 2011).

 

Achievements of DNA Aided Investigation

The success of DNA aided investigation can be understood from the fact that a large number of criminal cases are presently being solved with the help of CODIS. A remarkable example of the application of DNA aided assistance is the identification of the victims of the September 11, World Trade Center attack, in 2001. It was a massive attack claiming the lives of a very large number of victims. Only bones or the tissue fragments were the remnants of many victims of the attack and identification of the victims was a biggest challenge. Professionals from the National Institutes of Health and other institutions were assigned the job of identification of victims from the degraded samples. Profiles were developed using SNPs and mitochondrial DNA and entered into the database of the victims. By the end of 2005, out of 2792 people claimed to be dead in the attack, 1585 people could be identified.  The remaining cases were abandoned as the samples were highly degraded. In 2007, this case was reopened with the help of more sophisticated technology to enable further identification (DNA Forensics, 2009).

The results obtained from a five-city field study, conducted by the National Institute of Justice in 2008, showed that use of DNA was effective in the investigation of ordinary property crimes also. Almost twice the number of property crime suspects were caught when DNA was used as evidence. As the rate of suspects being caught increases, the rate of crime tends to decrease, and hence, the DNA technology ultimately proves to be cost effective (DNA and Property Crimes, 2010). Crimes like burglary, assault, and larceny were not generally associated with DNA analysis. Under a pilot project conducted by New York City Police Department (NYPD), officials were trained to identify the items which might contain biological evidence like cigarette butts, drink glasses etc. These evidences were subjected to DNA analysis. The aim of this project was to determine the extent to which these cases can be linked to more serious offenses like rapes or homicides. This study shows that offenders committing fewer offensive crimes can be linked to cases of rapes or homicides (in more than 30% of incidences). The success of this pilot project redefines the methodology of solving serious crimes (Dale, Greenspan and Orokos, 2006).

The Missing Persons DNA Database, created in Texas using mitochondrial DNA, has helped in the search of missing persons. This database targets the identification of the skeletal remains of unidentified human beings, kidnapped children, etc. This database is managed by FBI and the DNA profiles of the missing persons are matched with unidentified human remains, for example, those obtained from uncovered graves, crime victim remains etc.

Two hijackers of American Airlines Flight 11, involved in the attack of World Trade Center, were investigated to be brothers through near-match searching, using DNA. Apart from human crimes DNA testing has also been used to protect endangered species of animals and to prevent animal poaching.

 

Limitations of the use of DNA Technology in Forensic Science

DNA database can act as an efficient tool in the course of law enforcement only when it has more data of the offenders. But many jurisdictions are still in the process of developing their database. Because of this and several other reasons, many cases remain unsolved, creating a backlog. This DNA backlog may prevent the prosecution of the actual culprit or imprisonment of wrongly convicted individuals. This might increase the chances of crime as the offender is left free. Moreover, as the DNA database expands, there is an increased demand for the experts who can analyze DNA and create profiles of a large number of offenders. Space limitations of the laboratories allow the processing of the samples obtained from the most serious crimes only.

 

Overcoming the Technological Hurdles through New Developments in Molecular Biology

There have been major developments in the field of forensic science due to the developments in the field of molecular biology. Gone are the days when investigators used to rely on only physically observable large evidences. Now, it is possible to analyze samples obtained from a single strand of hair. Now-a-days, scientists are motivated to analyze more difficult samples like trace samples, termed touch DNA. Recent developments in molecular biology help the scientists to face tougher challenges. The use of mini-STRs, can enhance the efficacy of detection, especially when the DNA sample obtained is highly degraded. Because of the small size, the amplification products of mini-STRs have a tendency to overlap more in comparison to conventional STRs. Hence, reconfiguration of STR kits into mini STR kits, can promote betterment of the routine analysis. SNPs can be used as genetic markers to predict the appearance of the culprit in cases where the suspect is unidentifiable. These markers can be used to identify the individual’s facial features, height complexion, etc. This makes the investigation processes more focused. Post mortem analysis can be improved if genetic variation and its effects on metabolism are also considered. This will help to solve the cases which are usually considered as suicides or are categorized under unexplained deaths. The deaths in these cases can be due to various reasons like poisoning of the victim, making the victim incapable of performing any action, forcible intoxication of the victim by alcoholic drinks, etc. Present DNA typing techniques can only identify the source of the sample but, with the help of expression analysis, it is also possible to identify the tissue from which the source was obtained. Stains noticed in the crime scenes can be from both organic and inorganic sources and this technique might help to screen the samples from the human origin. This will prevent the unnecessary effort of subjecting all the stains to DNA typing (Budowle and van Daal, 2009).

 

There is no doubt that use of DNA in solving cases has significantly affected the speed and accuracy of investigation of criminal cases. A collective effort of the forensic scientists and police can help in catching criminals, hence reducing the crime rate. Due to the current advancements in this area, we might expect to see a group of highly trained and educated scientists with ultramodern devices meant for DNA profiling in their hand, at the scene of crime.

 

 

References

 

 

Butler, J, M. (2005). Forensic DNA typing : biology, technology, and genetics of STR markers. Amsterdam, Boston: Elsevier Academic Press.

Budowle, B and van Daal, A. (2009). Extracting evidence from forensic DNA analyses: future molecular biology directions. Biotechniques. 46(5), 339-40, 342-50. doi: 10.2144/000113136.

Dale, W,M., Greenspan, O and Orokos, D. (2006). DNA Forensics: Expanding Uses and Information Sharing. Retrieved April 17, 2013 from http://bjs.gov/index.cfm?ty=pbdetail&iid=774

DNA Forensics. (2009). Retrieved April 17, 2013 from http://www.ornl.gov/sci/techresources/Human_Genome/elsi/forensics.shtml

DNA and Property Crimes. (2010). Retrieved April 17, 2013 from http://www.nij.gov/topics/forensics/evidence/dna/property-crime/

Hart, S, V. (2002). Using DNA to Solve Cold Cases. Retrieved April 17, 2013 from https://www.ncjrs.gov/pdffiles1/nij/194197.pdf

Jobling, M,A and Gill, P. (2004). Encoded evidence: DNA in forensic analysis. Nat Rev Genet, 5(10), 739-51.

James, N. (2012). DNA Testing in Criminal Justice: Background, Current Law, Grants, and Issues. Retrieved April 17, 2013 from http://www.fas.org/sgp/crs/misc/R41800.pdf

Lyle, D, P. (n.d.). Forensics: Fingering Criminals Using DNA. Retrieved April 17, 2013 from http://www.dummies.com/how-to/content/forensics-fingering-criminals-using-dna.html

The FBI and DNA. (2011). Retrieved April 17, 2013 from http://www.fbi.gov/news/stories/2011/november/dna_112311

The History of DNA. (n.d.). Retrieved April 17, 2013 from http://www.forensicscience.ie/Services/Forensic-Areas/DNA/The-History-of-DNA/

 

 

 

 

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An interesting story about how DNA helps in solving crime