Chapter 8 The Nervous System: Neuron Structure and Glial Cells

Mixed Nerves

Nerves that have the capability to carry both motor and sensory signals are called ________. They can carry AFFERENT signals--to the CNS-- and EFFERENT singals--away from the CNS to skeletal muscles.

Ganglia

Collections of nerve cell bodies found outside the CNS. They appear as knots around a nerve.

Sensory Nerves

Nerves that carry AFFERENT signals only from the peripheral nervous system to the central nervous system to determine if a response is needed is called_________

Motor Nerves

Nerves that carry out EFFERENT signals out from the central nervous system to skeletal muscles are called______

Nodes of Ranvier

The spaces on the axon are tiny gaps between the myelin sheaths. These segments of the axon are exposed the ECF but play an important role in the transmission of electrical signals along the axon.

Satellite Cells

These cells are nonmyelinating schwann cells and they form supportive capsules around a nerve cell's body located in the ganglia.

Astrocytes

These glial cells in the central nervous system are highly branched and carry out many jobs including: take up and release of chemicals, providing neurons with substrates for ATP production, and help to maintain homeostasis in the ECF. These cells also play an important role for forming the blood brain barrier.

Microglia

These specialized cells in the CNS are the part of the immune system. They remove damaged cells and foreign invades. But they can also release damage reactive oxygen species that form free radicals.

Oligodendrocytes

These specific cells form the myelin sheath around axons in the central nervous system. One of these cells branches out and forms myelin around several axons.

Schwann Cells

These specific cells form the myelin sheath around axons in the peripheral nervous system. A single axon may have hundreds of these cells around them.

Ependymal Cells

These specific glial cells in the CNS create a semipermeable layer that seperates the fluid compartments. This is also one source of neural stem cells--which are immature cells that can differentiate into a neuron and glial cells.

Enteric Nervous System

This "third" branch of the nervous system is a network of neurons that lines the walls of the digestive tract. This system is frequently controlled by the autonomic division of the nervous system, but it can also function as its own integrating center.

Central Nervous System

This division of the nervous system consists of the brain and the spinal cord. This part of the nervous system also acts as the integrating center to determine if a response is needed.

Glial Cells

This general kind of cell in the nervous system gets its name from the latin word meaning "glue". Thes cells are crucial for providing support for neurons and forming insulation for their axons. These cells are found within both the CNS and PNS. In the CNS there are four types of these cells called: Oligodendrocytes, Astrocytes, Microglia, and Ependymal cells. In the PNS there are two types of these cells: Schwann and Satellite cells.

Neuron

This general type of cell is the functional unit of the nervous system

Synaptic Cleft

This is a gap between two neurons where chemical messages are exchanged.

Axon Terminal

This is the most distal part of the neuron. It is the bulbous end of an axon where an electrical message is converted into a chemical message by the secretion of a neurotransmitter, neuromodulator, or neurohormone.

Axon

This long, thin, cellular extension lies between the myelin bundles of the neuron. This part of the neuron is specialized to convey electrical and chemical signals and it also conducts axon potentials.

Peripheral Nervous System

This part of the nervous system contains only sensory/afferent neurons and motor/efferent neurons. This part of the nervous system also divides from the efferent to the autonomic motor system, which further divides into the sympathetic and parasympathetic branches.

Myelin

This part of the neuron are several membrane bundles wrapped around the axon. These bundles serve as insulation for the axon. In the CNS this structure is created by Oligodendrocytes and in the PNS they are created by multiple Schwann Cells.

Axon Hillock

This part of the neuron is superior to the axon and myelin. It is a specialized area of the neuron that generates action potentials most commonly known as a neurons "trigger zone".

Dendrite

This part of the neuron physically resembles branches of a tree that ultimately receive incoming signals from other neurons

Cell Body

This part of the neuron resembles the body of a typical cell with a nucleus and organelles to direct cellular activity. The nucleus of this neuron structure is vital because it contains DNA which is the basis of protein synthesis

Interneurons

This specific type of neuron is kept completely within the CNS.