An Introduction To Nervous System

The development of the brain A mass of neural tissue in a hollow tube

central cavity decreases in relative size; thickness of walls and diameter of the inclosed space vary from region to region

forms the central canal of SC and ventricle of brain

astrocytes Largest and most numerous glial cells

---maintain blood-brain barrier ---provide structural support ---absorb and recycle neurotransmitters ---from scar tissue after injury

oligodendrocytes have smaller cell bodies and fewer processes

---myelinate CNS axons 

myelin (multilayered membrane sheath)



nodes (nodes of Ranvier)



internodes

---provide structural framework

microglia accounts for 5% of the CNS glial cells; the processes have many fine branches

---remove cells debris, wastes, and pathogens

Ependymal cells Ventricles Cuboidal

of the brain and central canal of the SC are lined by ependyma.

or columnar shaped; have slender processes

---assist in producing, circulating, and monitoring of cerebrospinal fluid

Satellite cells Surround the neuron cell bodies in peripheral ganglia.

---regulate nutrients for neurons and ganglia

neuron

Schwann cells ---surround all axons whether it’s unmyelinated or myelinated ---responsible for myelination of peripheral axons

Myelinated axon

Unmyelinated axon

Formation of myelin

An Introduction to Nervous System Xu Jin Department of Anatomy Chongqing Medical University

Every minute of every day, your nervous system is sending and receiving countless messages about what is happening both inside and around your body.

Outline and Objectives Anatomical Organization Cellular Organization Synaptic Communication An Introductory Glossary

Anatomical Organization The nervous system has two anatomical subdivisions Central nervous system (CNS) Peripheral nervous system (PNS)

Central nervous system (CNS) ---responsible for integrating, processing, and coordinating sensory data and motor commands. It’s also the seat of higher functions, such as intelligence memory , learning, and emotion

CNS contains brain and spinal cord

development

Brain 

cerebrum



cerebellum



diencephalon



brain stem

Peripheral nervous system (PNS) ---includes all of the neural tissue outside the CNS

Afferent division Begins at receptors, brings ensory information to the CNS

Efferent division Begins inside the CNS; carries motor commands to effectors Both divisions have somatic and visceral components; the visceral component of the efferent division is autonomic nervous system (ANS) The basic unit of PNS is nerve; structurally and functionally, it’s can be divided into cranial nerves and spinal nerves.

Overview of the nervous system Central nervous system sensory information within afferent division

Information processing

includ es Somatic nervous system

motor commands within efferent Peripheral division nervous system Autonomic nervous system

parasympathetic sympathetic division division special sensory somatic receptors sensory receptors

visceral sensory receptors

skeletal muscle

-smooth muscle -cardiac muscle -glands

Cellular Organization (neuron and neuroglia) The nervous system includes all of the neural tissue 20billion

nerve cells (neurons)

100billion

(neuroglia)

supporting cells

Glial cells are smaller than the neurons.

neuron ---responsible for the transfer and processing of information in the nervous system

Basic structure of a representative neuron dendrites cell body (soma)

axon

synaptic terminals

Classification of neuron

anaxonic

bipolar

Structural classification    

unipolar anaxonic neurons bipolar neurons unipolar neurons (pseudounipolar neurons) multipolar neurons (most common type in CNS)

multipolar

Functional classification Sensory neurons (10million) ---located outside the CNS; deliver information to the CNS; axons of them called afferent fibers Motor neurons (half a million have been found in the body) ---located inside and outside the CNS; deliver motor commands to the effectors;

Interneurons (outnumber all other neurons) ---located inside the CNS; responsible for the analysis of sensory inputs and the coordination of motor outputs

neuroglia ---isolate the neurons, provide a supporting framework and act as phagocytes

Neuroglia of the CNS Astrocytes

Neuroglia of the PNS Satellite

Oligodendrocytes

cells

Schwann

cells

Microglia Ependymal

cells

All neuron cell bodies and axons in the PNS are completely insulated from their surroundings by the processes of glial cells.

The detailed structure of neuron Cell body----perikaryon/nucleus/ cytoskeleton/ organelles/ Nissl bodies/ axon hillock

A neuron may innervate

---neurons

---skeletal muscle fibers

---gland cells

Each synaptic terminal is part of a synapse which is a specialized site where the neuron communicates with another cell.

Synaptic Communication A synapse exists between neurons or a neuron and another cell type. If between neurons, a synapse consists of an axon terminal +an axon or an axon terminal + the soma or an axon terminal + a dendrite

Chemical synapses transfer information by neurotransmitter substance; Electrical synapses permit ion flow between the cells

Presynaptic Synaptic

membrane

cleft

Postsynaptic

membrane

An Introductory Glossary for the Nervous System Central Nervous System (CNS)

brain and spinal cord,which contain control centers responsible for processing and integrating sensory information, planning and coordinating responses to stimuli..

Peripheral Nervous System (PNS)

Neural tissue outside the CNS, whose function is to link the CNS with other systems

Autonomic Nervous System (ANS)

Components of the CNS and PNS that are concerned with the control of visceral functions

nucleus

a CNS center with discrete anatomical boundaries

tract

a bundle of axons within the CNS that share a common origin, destination ,and function

pathways

nucleus and tracts that connect the brain with other organs and systems in the body

ganglia

an anatomically distinct collection of sensory or motor neuron cell bodies within the PNS

nerve

a bundle of axons in the PNS

Gross anatomy

gray matter

neural tissue dominated by neuron cell bodies

white matter

neural tissue dominated by myelinated axons

neuron

the basic functional unit of the nervous system: a highly specialized cell

axon

a long , slender cytoplasmic process of a neuron; axons are capable of conducting nerve impulses

dendrites

neuronal processes that are specialized to respond to specific stimuli in the extracellular environment

myelin

a membranous wrapping, produced by glial cells

neuroglia

supporting cells that interact with neurons

Histology

Functional categories receptor

a specialized cell, dendrite, or organ that responds to specific stimuli in the extracellular environment

effector

a muscle, gland, or other specialized cell or organ that responds to neural stimulation by altering its activity and producing a specific effect

reflex

a rapid stereotyped response to a specific stimulus

somatic

pertaining to the control of skeletal muscle activity (somatic motor) or sensory information from skeletal muscles, tendons and joints (somatic sensory)

visceral

pertaining to the control of functions , such as digestion, circulation, etc. (visceral motor) or sensory information from visceral organs (visceral sensory)

voluntary

under direct conscious control

involuntary

not under direct conscious control

The end