03 The Human Brain

The neuron is the basic unit of information processing in the human brain, capable of sending and receiving messages throughout the body. How does the neuron’s formrelate to its function?

What characteristics describe the human brain?

• The human brain has three major characteristics: integration, sophistication, and adaptability.

How is the nervous system organized?

• The nervous system consists of the central nervous system (the brain and the spinal cord) and the peripheral nervous system (the neurons and nerves that serve every other part of the body).
• The peripheral nervous system is divided into the somatic nervous system, which registers stimuli and regulates conscious actions, and the autonomic nervous system, which controls involuntary actions.
• Within the autonomic nervous system, the sympathetic system stimulates organs and responds to stress, and the parasympathetic system calms the organs and maintains normal functioning.

How does the nervous system operate at the cellular level?

• The brain is made up of neurons and glial cells. Neurons are communication cells that receive, process, and pass on neural signals. Glia support and insulate neurons.
• Neuron signaling is an all-or-nothing event. When the number of positive inputs exceeds a certain threshold, the neuron fires an action potential—an electrochemical signal that travels down the axon. In the synapse, neurotransmitters pass on information to the next neuron or gland.

What are the different parts of the human brain, and what role does each part play?

• The brain stem is connected to the spinal cord and houses the structures that maintain basic life functions.
• The limbic system regulates emotion, motivation, and social and emotional learning.
• The cerebral cortex performs most information processing. It has four lobes: The occipital lobe processes visual information, the temporal lobe handles auditory input and language, the parietal lobe interprets sensory information, and the frontal lobe coordinates memory, reasoning, problem solving, social behavior, language, and movement.