Nervous System Chapter 13

Nervous System Overview

• The nervous system allows us to receive, integrate, and react to environmental stimuli to maintain homeostasis.
• It consists of two main components: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

Nervous Tissue

• Nervous tissue contains two types of cells: neurons and neuroglia.
• Neurons transmit nerve impulses between parts of the nervous system.
• Neuroglia (or glial cells) support, protect, and nourish neurons.

Neuron Structure

• Neurons are classified according to function: sensory, interneurons, and motor neurons.
• Sensory neurons take impulses from sensory receptors to the CNS.
• Interneurons receive input from sensory neurons and other neurons, and communicate with motor neurons.
• Motor neurons take nerve impulses away from the CNS to an effector that carries out responses to environmental change.

Neuron Components

• A neuron has three basic parts: cell body, dendrites, and axon.
• The cell body contains the nucleus and other organelles.
• Dendrites receive signals from sensory receptors or other neurons.
• The axon conducts nerve impulses away from the cell body.

Myelin Sheath

• Some axons are covered by a protective myelin sheath formed by Schwann cells.
• Nodes of Ranvier are gaps on the axon with no myelin sheath.

Neurotransmitters

• Neurotransmitters are substances that transmit signals between nerves.
• Examples of neurotransmitters include acetylcholine, norepinephrine, dopamine, serotonin, glutamate, and GABA.
• Acetylcholine and norepinephrine are active in both the CNS and PNS.

The Central Nervous System (CNS)

• The CNS is made up of the spinal cord and the brain.
• The CNS is wrapped in protective membranes called meninges, with spaces filled with cerebrospinal fluid.
• The CNS is composed of two types of nervous tissue: gray matter and white matter.
• Gray matter is composed of short, non-myelinated fibers.
• White matter is composed of myelinated axons.

The Spinal Cord

• The spinal cord extends from the base of the brain through the foramen magnum into the vertebral canal.
• The spinal cord has three main components: central canal, gray matter, and white matter.
• The central canal is filled with cerebrospinal fluid.
• The gray matter is "butterfly shaped" and contains interneurons.
• The white matter contains interneurons grouped in tracts (ascending and descending).

Functions of the Spinal Cord

• The spinal cord provides a means of communication between the brain and peripheral nerves.
• The spinal cord is a center for reflex actions.

Overview of the nervous system, including its functions, components, and parts. Learn about the central nervous system, peripheral nervous system, and more.