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Q16:
Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.
Solution :
1. Neurobiological Basis of Addiction
The persistence of alcohol and drug addiction is fundamentally rooted in the alteration of the brain's reward circuitry, specifically the mesolimbic dopamine pathway. Upon ingestion of psychoactive substances, there is an acute surge in dopamine release within the Nucleus Accumbens [Per the Dopamine Reward Hypothesis].
2. Physiological Adaptation and Tolerance
Repeated exposure to addictive substances forces the central nervous system to undergo homeostatic down-regulation. The brain reduces the number of dopamine receptors (specifically $D_2$ receptors) or decreases their sensitivity to compensate for the continuous chemical hyper-stimulation.
- Tolerance: The user requires progressively larger doses of the substance to achieve the initial "high" or reward effect [Pharmacological principle of Neuroadaptation].
- Dependence: The body’s physiological functioning becomes inextricably linked to the presence of the substance, leading to the internal belief that the drug is necessary for homeostasis.
3. Withdrawal Syndrome
When the substance is withheld, the brain—having adjusted to the presence of the toxin—exhibits a characteristic "rebound" effect known as Withdrawal Syndrome. This is marked by physiological and psychological distress, including anxiety, tremors, nausea, tachycardia, and severe cravings [Per the Opponent Process Theory].
4. Psychological and Environmental Reinforcement
| Mechanism | Impact on Habituation |
|---|---|
| Positive Reinforcement | The initial pleasurable euphoria acts as a powerful behavioral driver for repetition. |
| Negative Reinforcement | Continued use is driven by the urgent need to escape the painful symptoms of withdrawal. |
| Conditioning | Environmental cues, social settings, and emotional states become linked to the "reward," triggering cravings even after long periods of abstinence [Classical Conditioning principle]. |
5. Long-term Structural Changes
Chronic substance abuse affects the prefrontal cortex, the region responsible for executive function, impulse control, and decision-making. By damaging the neural pathways involved in self-regulation, the substance diminishes the individual's "willpower" to cease usage, effectively hijacking the brain's choice-making apparatus.
Final Solution: The difficulty in terminating alcohol or drug habits arises from a combination of neurochemical adaptation (tolerance), the emergence of painful physiological withdrawal symptoms, the conditioning of the brain’s reward systems to associate environmental cues with substance use, and the impairment of the prefrontal cortex, which erodes the cognitive ability to exercise inhibitory control.
More Questions from Class 12 Biology Human Health and Disease EXERCISES
- Q1: What are the various public health measures, which you would suggest as safeguard against infectious diseases?
- Q1: What are the various public health measures, which you would suggest as safeguard against infectious diseases?
- Q2: In which way has the study of biology helped us to control infectious diseases?
- Q2: In which way has the study of biology helped us to control infectious diseases?
- Q3(a): How does the transmission of each of the following diseases take place? (a) Amoebiasis
- Q3(a): How does the transmission of each of the following diseases take place? (a) Amoebiasis
- Q3(b): How does the transmission of each of the following diseases take place? (b) Malaria
- Q3(b): How does the transmission of each of the following diseases take place? (b) Malaria
- Q3(c): How does the transmission of each of the following diseases take place? (c) Ascariasis
- Q3(c): How does the transmission of each of the following diseases take place? (c) Ascariasis
- Q3(d): How does the transmission of each of the following diseases take place? (d) Pneumonia
- Q3(d): How does the transmission of each of the following diseases take place? (d) Pneumonia
- Q4: What measure would you take to prevent water-borne diseases?
- Q4: What measure would you take to prevent water-borne diseases?
- Q5: Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
- Q5: Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
- Q6: Name the primary and secondary lymphoid organs.
- Q6: Name the primary and secondary lymphoid organs.
- Q7(a): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (a) MALT
- Q7(a): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (a) MALT
- Q7(b): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (b) CMI
- Q7(b): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (b) CMI
- Q7(c): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (c) AIDS
- Q7(c): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (c) AIDS
- Q7(d): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (d) NACO
- Q7(d): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (d) NACO
- Q7(e): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (e) HIV
- Q7(e): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (e) HIV
- Q8(a): Differentiate the following and give examples of each: (a) Innate and acquired immunity
- Q8(a): Differentiate the following and give examples of each: (a) Innate and acquired immunity
- Q8(b): Differentiate the following and give examples of each: (b) Active and passive immunity
- Q8(b): Differentiate the following and give examples of each: (b) Active and passive immunity
- Q9: Draw a well-labelled diagram of an antibody molecule.
- Q9: Draw a well-labelled diagram of an antibody molecule.
- Q10: What are the various routes by which transmission of human immuno-deficiency virus takes place?
- Q10: What are the various routes by which transmission of human immuno-deficiency virus takes place?
- Q11: What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?
- Q11: What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?
- Q12: How is a cancerous cell different from a normal cell?
- Q12: How is a cancerous cell different from a normal cell?
- Q13: Explain what is meant by metastasis.
- Q13: Explain what is meant by metastasis.
- Q14: List the harmful effects caused by alcohol/drug abuse.
- Q14: List the harmful effects caused by alcohol/drug abuse.
- Q15: Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?
- Q15: Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?
- Q16: Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.
- Q17: In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
- Q17: In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
CBSE Solutions for Class 12 Biology Human Health and Disease
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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