Functional and Clinical Neuroanatomy

A Guide for Health Care Professionals

Jahangir Moini, Pirouz Piran

• Publisher: Academic Press
• Year: 2020
• Print ISBN: 9780128174241
• eBook ISBN: 9780128174258
• Topic: Biological Sciences
• Subtopic: Human Anatomy & Physiology
• Index: Biological Sciences

Functional and Clinical Neuroanatomy: A Guide for Health Care Professionals is a comprehensive, yet easy-to read, introduction to neuroanatomy that covers the structures and functions of the central, peripheral and autonomic nervous systems. The book also focuses on the clinical presentation of disease processes involving specific structures. It is the first review of clinical neuroanatomy that is written specifically for nurses, physician assistants, nurse practitioners, medical students and medical assistants who work in the field of neurology. It will also be an invaluable resource for graduate and postgraduate students in neuroscience.With 22 chapters, including two that provide complete neurological examinations and diagnostic evaluations, this book is an ideal resource for health care professionals across a wide variety of disciplines.- Written specifically for "mid-level" providers in the field of neurology- Provides an up-to-date review of clinical neuroanatomy based on the latest guidelines- Provides a logical, step-by-step introduction to neuroanatomy- Offers hundreds of full-color figures to illustrate important concepts- Highlights key subjects in "Focus On" boxes- Includes Section Reviews at critical points in the text of each chapter

Chapter 1

Histophysiology

Abstract

The human nervous system is the primary controlling and communicating system of the body. The nervous system includes multiple nervous organs, including the brain; spinal cord; receptors in complex sense organs such as the eye and ear; and nerves that link with other body systems. The complex sense organs receive collected information from external and internal stimuli, process it, and send signals to initiate required responses. Nervous tissue makes up the organs of the nervous system and supports blood vessels as well as connective tissues.

Keywords

Autonomic nervous system; Central nervous system; Cerebrospinal fluid; Peripheral nervous system; Peripheral nerves; Somatic nervous system

The human nervous system is the primary controlling and communicating system of the body. The nervous system includes multiple nervous organs, including the brain; spinal cord; receptors in complex sense organs such as the eye and ear; and nerves that link with other body systems. The complex sense organs receive collected information from external and internal stimuli, process it, and send signals to initiate required responses. Nervous tissue makes up the organs of the nervous system and supports blood vessels as well as connective tissues.

Neurons are the basic structural and functional units of the nervous system. They are specialized cells used for intercellular communication and serve as the transmitting cells of the nervous system. Nervous tissue contains another group of cells besides neurons. These supporting cells are called neuroglia, or glial cells, which are essential for neurons to survive and function. Neuroglia preserve physical and biochemical structures of nervous tissue. Glial cells are divided into microglia and macroglia (astrocytes, oligodendrocytes, and ependymal cells).

Anatomical divisions of the nervous system

The two divisions of the nervous system include the central nervous system (CNS) and peripheral nervous system (PNS) (see Fig. 1.1). The CNS consists of the brain and the spinal cord.

Fig. 1.1 The central nervous system and peripheral nervous system.

The CNS integrates, processes, and coordinates sensory data and motor commands. Sensory data concerns conditions inside or outside of the body. Motor commands regulate skeletal muscles and glands. The brain controls higher functions such as intelligence, memory, learning, cognition, and emotion.

The PNS includes the nervous tissue that is not the part of the CNS. The two PNS subdivisions are the somatic nervous system (SNS) and autonomic nervous system (ANS). The PNS brings sensory information to the CNS. It also uses motor commands to communicate with peripheral tissues and organs. Nerve fibers are made up by bundles of axons. These bundles carry sensory information and motor commands in the PNS. They are known as peripheral nerves, or more simply nerves. The nerves connected to the brain are referred to as cranial nerves, while the nerves attached to the spinal cord are called spinal nerves.

Functional divisions of the nervous system

The PNS is divided into afferent and efferent divisions, unlike the CNS, which does not have such divisions. The afferent division of the PNS carries sensory information to the CNS from peripheral tissue and organ receptors. These sensory structures detect changes in the internal or external environment and respond to certain stimuli. Receptors consist of simple and complex types. Single cells have thin extensions of cytoplasm as receptors. Complex receptor organs include the eye and ear. Neurons as well as specialized tissue cells may also serve as sensory receptors.

Motor commands from the CNS (brain and spinal cord) are carried by the efferent division of the PNS to the muscles, glands, and adipose tissues. These target effectors respond to these stimuli. The efferent division has two subdivisions:

• • The SNS regulates skeletal muscle contractions. Voluntary muscle contractions are consciously controlled. Involuntary contractions are controlled subconsciously. The automatic responses involved in involuntary contractions are called reflexes.
• • The ANS is also known as the visceral motor system. It subconsciously regulates cardiac muscle, smooth muscles, adipose tissues, and glandular secretions. The ANS includes two divisions: the parasympathetic nervous system and the sympathetic nervous system. These subdivisions usually have opposite actions. For example, sympathetic activity increases the heart rate while parasympathetic activity slows it.

The ANS within the gastrointestinal system is also called the enteric nervous system (ENS), a network of neurons and nerves in the walls of the digestive tract. The sympathetic and parasympathetic divisions affect ENS activities. However, the ENS is able to begin and regulate many local visceral reflexes with no input from the CNS. The ENS and the brain use identical neurotransmitters.

Section review

1. 1. What are the subdivisions of the nervous system?
2. 2. What are the functions of the ANS?
3. 3. What are the differences between the afferent and efferent divisions?

Neuroglia

The functions of neuroglia include the separation and the protection of neurons, providing support for nervous tissue, and assisting in the regulation of interstitial fluid composition (ependymal cells and astrocytes). There are different types of neuroglia with different functions as mentioned above. Approximately 90% of the nervous system consists of neuroglia. Therefore, there are more neuroglia than neurons. In the CNS, there four types of neuroglia, while in the PNS there are only two types. Table 1.1 summarizes various types of neuroglia and their functions.

Table 1.1

Types of neuroglia.

Central nervous system	1. Microglia	Small, stationary phagocytes that remove debris, wastes, and pathogens from cells. They can enlarge and move due to stimulation, and also eliminate synapses (synaptic pruning)
	2. Astrocytes	Have a central body with many radiating processes. They maintain the blood-brain barrier; provide structural support; control amounts of ions, nutrients, and dissolved gases; absorb and recycle neurotransmitters; form scar tissue after injuries
	3. Oligodendrocytes	Have a central body with processes that wrap around their neuron processes. They myelinate CNS axons; provide framework
	4. Ependymal cells	They form sheets with the motile cilia, and line ventricles of the brain and the central spinal cord canal; produce cerebrospinal fluid, and also propel it
Peripheral nervous system	1. Schwann cells	Each cell entirely wraps around the neuron processes, with an outer portion called the neurilemma. They provide myelination in the PNS; surround all PNS axons; assist in repairs following injuries
	2. Satellite cells	Also called satellite glial cells, they cover the surface of nerve cell bodies in sensory, sympathetic, and parasympathetic ganglia. In the neurons around ganglia, they control levels of neurotransmitters, oxygen, carbon dioxide, and nutrients; surround neuron cell bodies

Neuroglia of the CNS

The CNS contains four types of neuroglia: microglia, astrocytes, oligodendrocytes, and ependymal cells.

Microglia

Microglia are the least common and smallest CNS neuroglia. They are phagocytic cells with thin, finely branched processes. They migrate through nervous tissue, engulfing cellular debris, wastes, and pathogens. Microglia originate in early embryonic development from the mesodermal cell layer. Microglia migrate into the CNS while it is forming.

Astrocytes

Astrocytes are the most numerous and the largest neuroglia in the CNS. They are so named because of their star-like shape (see Fig. 1.2). Astrocytes have many thin cytoplasmic processes, which end in vascu...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• About the Authors
• Preface
• Acknowledgments
• Chapter 1: Histophysiology
• Chapter 2: Embryology
• Chapter 3: Gross anatomy of the brain
• Chapter 4: Meninges and ventricles
• Chapter 5: Blood supply of the CNS
• Chapter 6: Cerebral cortex
• Chapter 7: Basal nuclei
• Chapter 8: Diencephalon: Thalamus and hypothalamus
• Chapter 9: Brainstem
• Chapter 10: Cranial nerves
• Chapter 11: Trigeminal and facial nerves
• Chapter 12: Auditory system
• Chapter 13: Auditory system lesions and disorders
• Chapter 14: Visual system
• Chapter 15: Limbic, olfactory, and gustatory systems
• Chapter 16: Cerebellum
• Chapter 17: Autonomic nervous system
• Chapter 18: Neurotransmitters
• Chapter 19: Spinal cord
• Chapter 20: Spinal cord lesions and disorders
• Chapter 21: Complete neurological exam
• Chapter 22: Neurologic diagnostic procedures
• Glossary
• Index