Overview: Nervous System
- Nervous system means the body system that receives information, processes it, and sends signals that control movement, organ function, sensation, and many automatic body activities.
- Anatomically, the nervous system consists of the central nervous system and the peripheral nervous system.
- Anatomical division means grouping nervous-system parts by physical location in the body.
- Functionally, the nervous system has sensory and motor components; the motor component is further divided into somatic and autonomic systems.
- Functional division means grouping nervous-system parts by what the signals do.
- Central nervous system (CNS) means the brain and spinal cord.
- Brain and spinal cord are protected inside bone: the brain is inside the skull, and the spinal cord is inside the vertebral column.
- Peripheral nervous system (PNS) means the nerves, ganglia, receptors, and motor components that lie outside the central nervous system.
- Ganglia are groups of neuron cell bodies outside the central nervous system.
- Receptors are sensory structures that detect changes such as touch, stretch, pain, temperature, or chemical signals.
- Motor components are parts of nerves that carry commands from the central nervous system to structures that respond.
- Sensory component means the part of the nervous system that carries electrical impulses toward the central nervous system.
- Electrical impulse is a rapid change in membrane voltage used by neurons to communicate.
- Motor component means the part of the nervous system that carries impulses away from the central nervous system to body structures.
- Somatic nervous system (SNS) is the motor system mainly involved in conscious voluntary actions.
- Voluntary action means a movement a person can usually choose, such as moving skeletal muscle.
- Somatic nervous system (SNS) does not control smooth muscle, cardiac muscle, reflex arcs, or glands.
- Smooth muscle is involuntary muscle in organs and blood vessels.
- Cardiac muscle is involuntary muscle in the heart.
- Reflex arc is a fast neural pathway that produces an automatic response without requiring conscious decision.
- Autonomic nervous system (ANS) regulates internal organs and involuntary body functions.
- Sympathetic division is the autonomic division that prepares the body for stress, action, danger, or freezing.
- Flight, fight, and freeze responses include changes such as increased heart activity, altered blood flow, and heightened readiness.
- Parasympathetic division is the autonomic division that supports calming, recovery, digestion, and many glandular secretions.
- Secretomotor innervation means nerve supply that stimulates glands to secrete.
- Exocrine glands release products through ducts or onto surfaces, such as saliva, sweat, or digestive secretions.
- Enteric nervous system is the autonomic nerve network that serves the digestive system.
- Enteric nervous system can operate independently, but sympathetic and parasympathetic signals can modify its activity.
- Nervous tissue consists of neurons and supporting cells.
- Nervous tissue contains neurons and supporting cells.
- Neurons are excitable cells that conduct impulses.
- Supporting cells protect, nourish, insulate, and maintain the environment around neurons.
- Glial cells are supporting cells in the central nervous system.
- Satellite cells, capsule cells, and Schwann cells are supporting cells associated with the peripheral nervous system.
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