CBSE Class 11 Psychology Chapter 3: The Bases of Human Behaviour - NCERT Solutions

Solution: The evolutionary perspective explains the biological basis of behavior by looking at gradual, orderly biological changes that occur in a species over long periods. These changes are driven by the need to adapt to environmental demands. Physiological and biological modifications resulting from evolution happen very slowly, often becoming apparent only after hundreds of generations. Key features of modern humans that evolved include a highly developed brain with enhanced cognitive capacities (like perception, memory, and reasoning), the ability to walk upright on two legs, and hands with opposable thumbs, which facilitated tool use and manipulation. The evolution of the human brain shows a progression from older structures like the limbic system, brain stem, and cerebellum to the more recently developed cerebral cortex, reflecting increasing complexity in cognitive functions.

Solution: Neurons are the fundamental units of the nervous system, specialized for converting stimuli into electrical impulses and transmitting information. This process involves several key parts: dendrites, soma (cell body), axon, and terminal buttons. The transmission pathway is typically: Dendrites → Soma → Axon → Terminal buttons.

1. Dendrites: These branch-like structures receive incoming neural impulses from adjacent neurons or directly from sensory organs.
2. Soma (Cell Body): The nerve impulse is then relayed to the soma, which integrates the signals.
3. Axon: From the soma, the impulse travels along the axon, a long projection that conducts the electrical signal away from the cell body.
4. Terminal Buttons: At the end of the axon are the terminal buttons. These structures are responsible for transmitting the information to the next neuron, a gland, or a muscle cell, usually via chemical messengers called neurotransmitters.

This conversion of stimuli into electrical impulses and their subsequent transmission allows for rapid communication throughout the nervous system.

Solution: The cerebral cortex, the outermost layer of the brain, is divided into four major lobes, each associated with distinct functions:

1. Frontal Lobe: Located at the front of the brain, this lobe is primarily responsible for higher-level cognitive functions. These include attention, thinking, planning, problem-solving, memory, learning, and reasoning. It also plays a crucial role in regulating and inhibiting emotional and autonomic responses, allowing for more controlled behavior.
2. Parietal Lobe: Situated behind the frontal lobe, the parietal lobe is mainly concerned with processing sensory information from the body, particularly touch, temperature, and pain (cutaneous sensations). It also integrates sensory input with visual and auditory information, contributing to spatial awareness and navigation.
3. Temporal Lobe: Located below the parietal lobe on the sides of the brain, the temporal lobe is primarily involved in processing auditory information. It is crucial for recognizing sounds, understanding spoken language, and plays a significant role in memory, particularly for symbolic sounds and words.
4. Occipital Lobe: Found at the back of the brain, the occipital lobe is dedicated to processing visual information. It interprets visual stimuli received from the eyes, enabling us to perceive shapes, colors, and movement, and is involved in visual memory and orientation.

Solution: The endocrine system is a network of glands that secrete chemical substances called hormones directly into the bloodstream. These hormones act as chemical messengers, influencing a wide range of bodily functions, development, and personality. The endocrine system significantly affects our behavior by regulating physiological processes and coordinating responses to various stimuli.

While the source text doesn't list all specific endocrine glands and hormones, it explains their general function:

• Hormonal Influence: Hormones regulate metabolism, growth, mood, and stress responses. For example, insulin, secreted when blood sugar is high, lowers it to normal levels, demonstrating a direct impact on physiological balance that can indirectly affect behavior.
• Coordination of Body Activities: In situations of sudden danger or stress (like 'fight or flight'), the endocrine system releases hormones (e.g., adrenaline) that prepare the body for action, leading to physiological changes like increased heart rate and alertness, which directly influence behavior.
• Homeostasis: The endocrine glands work together to maintain internal equilibrium (homeostasis). If one gland secretes an excess hormone, another may release a counteracting hormone to restore balance. This intricate regulation ensures that the body's internal environment remains stable, which is essential for consistent and adaptive behavior.

The coordinated action of these glands ensures that body activities are managed effectively, impacting everything from mood and energy levels to stress responses and overall personality development.