18.1
What is a Nervous System?
Overview
The nervous system is the collection of specialized cells responsible for maintaining an organism’s internal environment and coordinating the…
The nervous system allows a person to detect the outside world and make appropriate responses to it. Additionally, it controls functions ranging from breathing to advanced reasoning.
This system is divided into two parts, the central nervous system or CNS which contains the brain and spinal cord, and the peripheral nervous system, the PNS, which includes the nerves that travel between the CNS and the rest of the body.
The brain is subdivided into areas that have different functions such as processing visual information or coordinating movements, but it is also highly interconnected, allowing for integration of information.
Like the rest of the nervous system, the brain is composed of neurons, cells that generate and transmit neural signals, and glia, cells that support neural functioning.
Below the brain lies the spinal cord, CNS tissue that extends down the vertebral canal. It facilitates signaling between the brain and PNS and also controls some basic functions such as reflexes.
In the PNS, nerves, bundles of neuronal axons, transmit instructions out to skeletal muscles to control movement and to internal organs to regulate autonomic functions such as digestion. Nerves also carry sensory information from receptor cells such as those in the skin that detect touch to the CNS for analysis.
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Q1: What are the two main divisions of the nervous system?
The nervous system divides into the central nervous system (CNS), which contains the brain and spinal cord, and the peripheral nervous system (PNS), which includes nerves traveling between the CNS and the rest of the body. The CNS processes information and coordinates responses, while the PNS transmits motor commands and sensory information between the CNS and body tissues.
Q2: How does the spinal cord contribute to nervous system function?
The spinal cord extends down the vertebral canal below the brain and facilitates signaling between the brain and PNS. Beyond relaying information, the spinal cord independently controls basic functions such as reflexes without requiring input from the brain, enabling rapid responses to stimuli.
Q3: What types of cells make up the nervous system?
The nervous system comprises neurons, which generate and transmit neural signals, and glial cells, which support neural functioning. Neurons communicate at junctions called synapses using neurochemicals and ions. Glial cells roughly equal the number of neurons in the brain and include astrocytes, microglia, oligodendrocytes, and ependymal cells in the CNS.
Q4: What functions do peripheral nerves perform?
Peripheral nerves transmit motor instructions from the CNS to skeletal muscles, controlling movement, and to internal organs, regulating autonomic functions like digestion. Nerves also carry sensory information from receptor cells in the skin and other tissues back to the CNS for analysis and processing.
Q5: How is the brain organized and what are its main regions?
The brain subdivides into the cerebrum, cerebellum, and brainstem. The cerebrum, the largest region, processes visual information and coordinates movements through highly interconnected areas. The cerebellum coordinates muscle movement, while the brainstem connects the brain to the spinal cord and controls vital functions such as breathing and swallowing.
Q6: What is the autonomic nervous system and what does it control?
The autonomic nervous system, part of both the CNS and PNS, controls smooth muscles, cardiac muscles, and glands governing involuntary actions. It regulates functions including digestion, heart rate, and breathing through the sympathetic nervous system fight flight response and parasympathetic divisions that balance these involuntary processes.
Q7: How does the nervous system detect and respond to the external environment?
The nervous system detects the outside world through sensory receptor cells in the skin and other tissues that transmit information to the CNS. The CNS processes this sensory input and generates appropriate motor responses, enabling organisms to interact with their environment and escape danger through coordinated movement and autonomic adjustments.