Human central nervous system

Main

The human central nervous system (CNS) is the command center of the body, consisting of the brain and spinal cord, which process and integrate sensory information to control all bodily functions and behaviors. Neuroscientists and philosophers propose that the CNS, particularly the brain, is the seat of consciousness.

The CNS works in the following phases:

1. Sensory input: Sensory receptors detect stimuli and send signals to the CNS via sensory neurons.

2. Integration: The brain and spinal cord process and interpret the sensory information.

3. Motor output: The CNS sends signals via motor neurons to effector organs (muscles or glands) to produce a response.

The CNS interacts closely with the peripheral nervous system (PNS), which consists of sensory and motor neurons that connect the CNS to the rest of the body. The PNS relays sensory information to the CNS and carries out motor commands from the CNS.

Terms

• Nervous system: The complex network of neurons and supporting cells that transmit signals between different parts of the body, consisting of the central nervous system (CNS) and peripheral nervous system (PNS).

• Brain: The major functional unit of the CNS located at the anterior end of the spinal cord. It is encased in the skull and protected by the cranium.

• Spinal cord: A structure composed of nervous tissue positioned along the rostral to caudal axis of the body, continuous with and lying caudally to the brain.

• Brainstem: Consists of the medulla, pons, and midbrain. Involved in autonomic control of the body, such as blood pressure, breathing, balance, and relaying information between the cerebellum and cerebral cortex.

• PNS: The part of the nervous system that consists of the nerves and ganglia outside the brain and spinal cord, serving to connect the CNS to the limbs and organs.

• Consciousness: The state of being aware of one's own existence, thoughts, feelings, and surroundings.

• Neuron: The basic functional unit of the nervous system, consisting of a cell body, dendrites, and an axon, which transmits electrical and chemical signals.

Analogy

The CNS can be compared to an airport control tower that manages all the flights. Just as the control tower receives information about incoming and outgoing flights, processes it, and sends out instructions to guide the planes, the CNS receives sensory input, integrates the information, and sends out motor commands to control the body's functions and actions.

Misconception

A common misconception is that the brain is the only organ involved in the nervous system. In reality, the spinal cord is also a vital component of the CNS. It carries messages between the brain and the rest of the body and has some ability to process reflexes. Damage to the spinal cord can lead to paralysis and loss of sensation below the level of injury, demonstrating its crucial role.

History

1. 4th century BC: Aristotle and Herophilus study the nervous system, believing the brain to be the seat of intelligence.

2. 2nd century AD: Galen identifies seven pairs of cranial nerves and describes the structure of the nervous system.

3. 1664: Thomas Willis publishes Cerebri Anatome, providing the first detailed description of the brain and nerves.

4. 19th-20th century: Rapid advancements in understanding the microscopic structure and function of neurons and the CNS.

5. 1981: Roger Sperry is awarded the Nobel Prize for his work on split-brain research, demonstrating the functional specialization of the cerebral hemispheres.

6. 1990s-present: Advances in neuroimaging techniques, such as fMRI and PET scans, revolutionize the study of brain function and connectivity.

How to use it

1. Maintain a healthy lifestyle to support CNS function: Engage in regular exercise, eat a balanced diet rich in brain-healthy nutrients, get sufficient sleep, and manage stress through relaxation techniques like meditation or deep breathing exercises.

2. Protect your brain and spinal cord from injury: Always wear a seatbelt when driving, use proper protective gear when engaging in sports or activities with a risk of head or spinal trauma, and take steps to prevent falls, especially in older adults.

3. Stay mentally active to promote brain health: Engage in stimulating activities like reading, learning new skills, solving puzzles, or playing musical instruments to help maintain cognitive function and potentially reduce the risk of age-related cognitive decline.

Facts

• The human brain contains approximately 86 billion neurons and trillions of synapses.

• Information can travel along neurons in the CNS at speeds of up to 268 miles per hour.

• The spinal cord is about 18 inches long and 1/2 inch thick in adults.

• The brain consumes around 20% of the body's total energy despite accounting for only about 2% of body weight.

• The CNS is protected by the blood-brain barrier, a selective permeability barrier that helps maintain brain homeostasis and protects against toxins and pathogens.