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

The evolutionary perspective explains the biological basis of behaviour by looking at gradual, orderly biological changes that occur in a species over long periods. These changes are adaptations to the changing demands of the environment, driven by natural selection. Physiological and biological modifications happen so slowly that they become apparent only after hundreds of generations.

Key evolutionary developments in modern humans include:

• A highly developed brain with enhanced cognitive capacities like perception, memory, thinking, and reasoning.
• The ability to walk upright on two legs (bipedalism).
• Free hands with opposable thumbs, allowing for manipulation and tool use.

These environmental pressures led to significant biological and behavioural changes over time. In terms of brain development, the oldest structures are the limbic system, brain stem, and cerebellum, while the most recently evolved is the cerebral cortex.

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 of the neuron:

1. Dendrites: These branch-like extensions receive neural impulses from adjacent neurons or directly from sense organs.
2. Soma (Cell Body): The nerve impulse is then passed on to the main body of the neuron, the soma.
3. Axon: From the soma, the impulse travels along the axon, a long projection that carries the information away from the cell body.
4. Terminal Buttons: At the end of the axon are the terminal buttons, which transmit the information to another neuron, a gland, or a muscle cell.

The sequence of information transmission is typically: Dendrites → Soma → Axon → Terminal Buttons.

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

1. Frontal Lobe: This lobe is primarily responsible for higher-level cognitive functions such as attention, thinking, memory, learning, and reasoning. It also plays a crucial role in regulating emotional responses and exerting inhibitory control over autonomic functions.
2. Parietal Lobe: The parietal lobe is mainly concerned with processing sensory information from the body, particularly touch (cutaneous sensations). It also integrates this information with visual and auditory inputs.
3. Temporal Lobe: This lobe is primarily involved in processing auditory information. It is also crucial for memory, especially for symbolic sounds and words, and plays a significant role in understanding both spoken and written language.
4. Occipital Lobe: Located at the back of the brain, the occipital lobe is dedicated to processing visual information. It is responsible for interpreting visual stimuli, recognizing colours, and maintaining visual orientation.

The endocrine system is a network of glands that secrete chemical substances called hormones directly into the bloodstream. These hormones regulate various bodily functions, influence development, and play a significant role in shaping personality and behaviour.

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

• Regulation of Body Functions: Hormones help control and coordinate body activities. For example, insulin, secreted by the pancreas, regulates blood sugar levels.
• Response to Stress: In situations of sudden fear or danger, the endocrine system releases hormones that prepare the body to face the challenge, coordinating diverse physiological activities.
• Maintaining Equilibrium: The endocrine glands work together to maintain a balance (homeostasis) within the body. If one gland secretes an excess hormone, another may release a hormone to counteract it, ensuring stability.
• Influence on Behaviour and Development: Hormones significantly influence an individual's behaviour, mood, growth, and overall personality development.