Anatomy

Progressive loss or destruction of myelin in the CNS and PNS with preservation of the axons; often leads to loss of sensation and/or motor control

Imflammation of a nerve

Classical term for a disorder affecting any segment of the nervous system

Any poison that acts specifically on nervous tissue

The Nervous system includes all the nervous tissues in the body

1. The central nervous system is composed of the brain and the spinal cord.

2. The periphheral nervous system is composed of the cranial nerves, spinal nerves, and ganglia

The nervous system is functionally subdivided into a sensory nervous system that conveys sensory information to the CNS, and a motor nervous system that conducts motor commands to muscles and glands

Neurons are excitable cells that transmit nerve impulses, and glial cells completely surround neurons and support them.

A generalized neuron has a cell body and processes called dendrites and an axon. They are classified structurally by the number of processes attached to the cell body (unipolar, bipolar, or multipolar) and functionally as sensory neurons, motor neurons, or interneurons.

Glial cells support neurons in the CNS. Astrocytes help form the blood-brain barrier and regulate tissue fluid compostion; ependymal cells line CNS cavities and produce cerebrospinal fluid; microflial cells act as phagocytes in nervous tissue, and oligodendrocytes myelinate CNS axons. In the PNS, satellite cells support neuron cell bodies in ganlia, and neurolemmocytes myelinate PNS axons.

A nerve impulse is the rapid movement of a charge along a neuron's plasma membrane

Oligodendrocyes (CNS) and neurolemmocytes (PNS) wrap around acons of neurons, forming a discontinuous myelin sheath along the axon, with small gaps called neurofibril nodes.

1. The myelin sheath insulates the axonal membrane, resulting in faster nerve impulse conduction.

2. Unmyelinated azons are associated with a neurommocyte but not ensheathed by it

Regeneration of damages neurons is limited to PNS acons that are able to regrow under certain conditions by a process called wallerian degeneration.

A nerve is a bundle of many parallel axons organized in three layers: (1)  an endoneurim around a single axon, (2) a perineurium around a fascicle, (3) and an epineurium around all the fascicles.

(1) the specialized junction between two exitable cells where a nerve impulse is transmitted is called a synapse. (2) swelling of axons at their end branches are called synaptic knobs. (3) The space between the presynaptic and postsynaptic cells is the synaptic cleff (4) Synapses are classified according to the point of contact between the synaptic knob and the postsynaptic cell as axodendritic, axosomatic, or axoaxonic.

(1) Synapses are termed electrical when a flow of ions passes from the presynaptic cell to the postsynaptic cell through gap junctions; synapese are termed chemical when a nerve impulse causes the release of a chemical neurotransmitter from the presynaptic cell that induces a response in the postsynaptic cell. (2) A myelinated axon conducts impulses faster than an unmeylinated axon, and the larger the diameter of the axon, the faster is the rate of conduction.

(1) Interneurons are organized into neuronal pools, which are groups of interconnected neurons with specific funtions. (2) In a converging circuit, neurons synapse on the same postsynaptic neuron. (3) A diverging circuit spreads information to several neurons (4) In a reverberating circuit, neurons continue to restmulate presynaptic neurons in the circuit. (5) A parallel-after-discharge circuit involves parallel patheways that process the same information over different amounts of time and deliver that information to the same output cell.

(1) Nervous tissue development begins in the early embryo with the formation of the neural plate. As this plate frows and develops, a neural groove appears as a depression in the plate, prior to the elevation of neural folds along the lateral side of the plate. The fusion of the neural folds gives rise to neural tube, from which the brain and spinal cord develop. (2) A neural tube defect can result if part of the neural tube fails to fuse.

transmit motor information

Skeletal Muscle Fiber

makes myelin sheaths in CNS

Neuron part that usually receives incoming impulses

side branches of axons

Respond to CNS infection

Neurons with multiple dendrites

Sensory to motor neuron communication

Uses a neurotransmitter

Neuron part that usually receives incoming impulses