Blood Supply of the Central Nervous System (Gross Anatomy of the Brain) Part 2

The Basilar Artery The two vertebral arteries join at the caudal border of the pons to form the single basilar artery (Fig. 4-1). The major branches of the basilar artery are described in the following sections. The Anterior Inferior Cerebellar Artery The anterior inferior cerebellar artery (AICA) is the most caudal branch arising from the […]

Histology of the Nervous System (The Neuron) Part 1

The Neuron Signals from one nerve cell to another are transferred across special zones of contact between the neurons that are known as synapses. The mechanism by which neurons communicate with each other is called synaptic transmission. Chemical neurotransmission is the most prevalent mechanism of communication between neurons. It involves release of chemical substances (neurotransmit-ters) […]

Histology of the Nervous System (The Neuron) Part 2

Types of Neurons Based on morphological characteristics, the neurons have been classified into the following groups: multipolar, bipolar, pseudo-unipolar, and unipolar. Multipolar Neurons Multipolar neurons are most common in the brain and spinal cord. They possess three or more dendrites and one long axon issuing from the cell body (Fig. 5-3A). A large motor neuron […]

Histology of the Nervous System (The Neuron) Part 3

Composition of Peripheral Nerves Each peripheral nerve consists of the following components: 1. Epineurium, which consists of a dense connective tissue layer enclosing several bundles of nerve fibers (Fig. 5-8); 2. Perineurium, which is a sheath of connective tissue enclosing each bundle of nerve fibers (Fig. 5-8); and 3. Endoneurium, which consists of a loose, […]

Electrophysiology of Neurons (The Neuron) Part 1

To understand the mechanisms by which the nervous system regulates complex functions and behaviors, it is important to have knowledge of the structure and function of its basic unit, the neuron. The most striking properties of neurons are their excitability and ability to conduct electrical signals. This topic will first describe the organization of the […]

Electrophysiology of Neurons (The Neuron) Part 2

Ion Channels A brief description of ion channels is presented in this section.Ion channels are made up of proteins that are embedded in the lipid bilayer of the neuronal membrane across which they span (Fig. 6-1). They are characterized by the following general properties. 1. The flow of ions through the channels does not require […]

Electrophysiology of Neurons (The Neuron) Part 3

Ionic Basis of the Action Potential As stated earlier, the resting membrane potential of a neuron is usually -65 mV. At rest, Na+ influx into the neuron through open nongated Na+ channels is balanced by the efflux of K+ through open nongated K+ channels. Thus, the membrane potential remains constant closer (but not equal) to […]

Electrophysiology of Neurons (The Neuron) Part 4

Guillain-Barre Syndrome   Multiple Sclerosis The cause of multiple sclerosis (MS) is unknown. It may be an autoimmune disease with inflammatory features that affect the CNS. It should be recalled that oligodendrocytes (not Schwann cells) provide myelination in the CNS. The body erroneously directs antibodies against proteins in the myelin sheath in the CNS. Thus, demyelination […]

Synaptic Transmission (The Neuron) Part 1

One of the unique features of nerve cells is their capability to communicate with each other with great precision even when they are separated by long distances. The mechanism by which neurons communicate with each other is called synaptic transmission, which is defined as the transfer of signals from one cell to another. A synapse […]

Synaptic Transmission (The Neuron) Part 2

Clinical Considerations Diseases Affecting the Chemical Transmission at the Nerve-Muscle Synapse Myasthenia Gravis Myasthenia gravis means "severe muscle weakness." It is an autoimmune disease in which the number of functional nAChRs in the postsynaptic membrane at the motor end-plate is reduced.In this disorder, antibodies against the nAChRs (probably produced by T and B lymphocytes) are […]