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Overview of the Nervous System
Central Nervous System (CNS) consists of the brain and spinal cord.
Peripheral Nervous System (PNS) connects the body to the CNS.
Divided into motor nerves (efferent) and sensory nerves (afferent).
Functions of the Nervous System
Three overlapping functions:
Sensory Input: Receptors detect changes (stimuli) in the environment inside or outside the body.
Integration: CNS processes and interprets sensory input.
Motor Output: CNS signals organs/muscles to elicit a response.
Nervous Tissue Components
Two main cell types in nervous tissue:
Neurons: Transmit electrical signals (action potentials).
Neuroglial Cells: Support, protect, and nourish neurons.
Types of Neurons
Multipolar Neurons: Many dendrites, one axon (common).
Bipolar Neurons: Two processes (rare, involved in special senses).
Unipolar Neurons: One process (mostly sensory neurons).
Synapse and Signal Transmission
Synapse: Junction between two neurons for signaling.
Neurotransmitters: Chemicals released across synaptic cleft.
Gray and White Matter
Gray Matter: Composed of neuron cell bodies, dendrites, and non-myelinated axons (CNS).
White Matter: Composed of myelinated axons (CNS), facilitating rapid signal transmission.
Neuroglial Cells Types
CNS: Astrocytes, Microglia, Ependymal Cells, Oligodendrocytes.
PNS: Satellite Cells, Schwann Cells (produce myelin).
Regeneration and Injury
PNS: Axons can regenerate through Schwann cells creating a regeneration tube.
CNS: Damage to cell bodies is typically irreversible.
Disorders of the Nervous System
Multiple Sclerosis (MS): Autoimmune disease attacking CNS myelin, causing symptoms like numbness and paralysis.
Development of the Nervous System
Develops from ectoderm, forming a neural tube (becomes spinal cord) and neural crest (forms sensory neurons).