Cells of the Nervous System

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Systems Biology

The cells of the nervous system consist of neurons and glial cells. Neurons are responsible for electrical signaling and have a central body called soma, and extensions called dendrites that receive incoming signals and an outgoing single axon that synapses with other cells via a nerve terminal. The point where the axon joins the soma is known as the axon hillock. In the nervous system, a group of cell bodies is called a nucleus in the central nervous system (CNS), and ganglion in the peripheral nervous system (PNS). Axon bundles in the CNS and PNS are referred to as tracts and nerves respectively. Nerves can be classified as motor, sensory, or mixed.

Glial cells form the remaining neural tissue and include oligodendrocytes (CNS) and Schwann cells (PNS) that provide myelination, creating an insulating layer around axons for faster signal transmission. Between the insulated sections are the nodes of Ranvier, unmyelinated sections allowing for signal regeneration. Astrocytes contribute to forming the blood-brain barrier, ependymal cells help secrete cerebral spinal fluid, and microglia function as the immune cells of the central nervous system, removing waste, damaged cells, and pathogens.

Lesson Outline

<ul> <li>Introduction to cells of the nervous system <ul> <li>Neurons responsible for electrical signaling</li> <li>Glial cells provide support</li> </ul> </li> <li>Neurons <ul> <li>Soma: neuron's cell body</li> <li>Dendrites: receive incoming signals</li> <li>Axon: carries electrical signals to other cells</li> <li>Axon hillock: sums up incoming signals and generates action potential if threshold is reached</li> <li>Organization within the nervous system <ul> <li>Central nervous system: nucleus (group of cell bodies) and tract (bundle of axons)</li> <li>Peripheral nervous system: ganglion (group of cell bodies) and nerve (bundle of axons)</li> </ul> </li> <li>Types of nerves <ul> <li>Motor nerves: control movement</li> <li>Sensory nerves: bring information about the world</li> <li>Mixed nerves: combination of motor and sensory fibers</li> </ul> </li> </ul> </li> <li>Glial cells <ul> <li>Myelination: insulating wrap of glial cells around axons for faster signaling <ul> <li>Oligodendrocytes: myelination in the central nervous system</li> <li>Schwann cells: myelination in the peripheral nervous system</li> </ul> </li> <li>Astrocytes: form the blood-brain barrier and provide an energy source for neurons</li> <li>Ependymal cells: secrete watery cerebral spinal fluid (CSF)</li> <li>Microglia: immune glial cells that remove waste, damaged cells, and pathogens</li> </ul> </li> </ul>

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What are the main functions of neurons and glial cells in the nervous system?

Neurons are the primary communicators in the nervous system, responsible for transmitting information through electrical and chemical signals. Glial cells, on the other hand, have various supportive roles, including providing structural support, maintaining homeostasis, and offering protection for neurons. Both types of cells are essential for the proper functioning of the nervous system.

What is the role of axon hillock and dendrites in neurons?

The axon hillock is the part of the neuron where the initial segment of the axon connects to the cell body. It serves as the integration center, determining if the incoming inputs from other neurons are strong enough to generate an action potential. Dendrites are the branching structures that extend from the cell body and receive incoming signals from other neurons. They convert these incoming signals into electrical impulses to be transmitted to the cell body.

How is myelination important for the proper functioning of the nervous system?

Myelination is the process in which glial cells (oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system) form a myelin sheath around the axons of neurons. This myelin sheath contributes to faster and more efficient electrical signal transmission along the axon. It also provides insulation and protection for the axons and plays a crucial role in maintaining the health of the neurons.

What roles do astrocytes and oligodendrocytes play as types of glial cells in the nervous system?

Astrocytes have numerous functions, including providing structural support to neurons, maintaining the blood-brain barrier, regulating the extracellular environment, and modulating neurotransmission. They also play a role in repairing damaged neurons or tissue after injury. Oligodendrocytes, on the other hand, are responsible for myelination in the central nervous system. They create the myelin sheath that wraps around axons, providing insulation and ensuring the efficient transmission of electrical signals along neurons.