BackChapter 11: The Nervous System – Structure, Function, and Histology
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Nervous System Overview
Introduction to the Nervous System
The nervous system is the master controlling and communicating system of the body. It is responsible for regulating and coordinating all body activities by transmitting signals between different parts of the body.
Sensory input: Monitoring internal and external stimuli.
Integration: Interpretation and processing of sensory input.
Motor output: Initiating responses to stimuli by activating effector organs (muscles and glands).
Organization of the Nervous System
Central Nervous System (CNS)
The CNS consists of the brain and spinal cord. It serves as the integration and command center, processing information and issuing instructions.
Brain: The main control center for processing sensory information and directing responses.
Spinal cord: Conducts signals to and from the brain and controls reflex activities.
Peripheral Nervous System (PNS)
The PNS includes all neural structures outside the CNS, such as paired spinal and cranial nerves. It links all parts of the body to the CNS by carrying messages to and from the brain and spinal cord.
Spinal nerves: Carry impulses to and from the spinal cord.
Cranial nerves: Carry impulses to and from the brain.
Ganglia: Collections of neuron cell bodies in the PNS.
Functional Divisions of the Peripheral Nervous System
Sensory (Afferent) Division
The sensory division transmits impulses from sensory receptors to the CNS.
Sensory afferent fibers: Carry signals from skin, skeletal muscles, and joints.
Visceral afferent fibers: Carry signals from visceral organs (organs within the ventral body cavity).
Motor (Efferent) Division
The motor division transmits impulses from the CNS to effector organs (muscles and glands), causing a response.
Somatic Nervous System
Known as the voluntary nervous system.
Composed of somatic motor nerve fibers (axons) that conduct impulses from the CNS to skeletal muscles.
Allows conscious control of skeletal muscles.
Autonomic Nervous System (ANS)
Known as the involuntary nervous system.
Consists of visceral motor nerve fibers (axons).
Regulates smooth muscle, cardiac muscle, and glands.
Subdivided into sympathetic and parasympathetic branches.
Histology of Nerve Tissue
Principal Cell Types
Neurons: Excitable cells that transmit electrical signals.
Neuroglia (glial cells): Supporting cells that surround and wrap neurons.
Supporting Cells: Neuroglia
Neuroglia, or glial cells, are several types of cells that provide support for neurons. Their functions include:
Insulating neurons to speed up action potential (AP) conduction.
Promoting health and growth of neurons.
Additional info: Neuroglia include astrocytes, microglia, ependymal cells, oligodendrocytes (in the CNS), and Schwann and satellite cells (in the PNS). Each type has specialized functions in supporting and protecting neurons.
