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

astrocytesLargest and most numerous glial cells

---maintain blood-brain barrier

---provide structural support

---absorb and recycle neurotransmitters

---from scar tissue after injury

oligodendrocyteshave smaller cell bodies and fewer processes

---myelinate CNS axons

myelin (multilayered membrane sheath) nodes (nodes of Ranvier) internodes

---provide structural framework

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

---remove cells debris, wastes, and pathogens

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

Cuboidal or columnar shaped; have slender processes

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

Satellite cells

neuron

Surround the neuron cell bodies in peripheral ganglia.

---regulate nutrients for neurons and ganglia

Schwann cells

Myelinated axon

Unmyelinated axon

Formation of myelin

---surround all axons whether it’s unmyelinated or myelinated

---responsible for myelination of peripheral axons

An Introduction to Nervous System

Xu Jin

Department of AnatomyChongqing 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.

Anatomical Organization

Cellular Organization

Synaptic Communication

An Introductory Glossary

Outline and Objectives

Anatomical Organization

The nervous system has two anatomical subdivisions

Central nervous system (CNS)

Peripheral nervous system (PNS)

Central nervous system (CNS)

CNS contains brain and spinal cord

Brain

cerebrum

cerebellum

diencephalon

brain stem

---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

development

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

Afferent division

Efferent division

Begins at receptors, brings ensory information to the CNS

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.

Central nervous system

Information processingsensory

information within

afferent division

motor commands

within efferent division

Somatic nervous system

Autonomic nervous system

parasympathetic division

sympathetic division

skeletal muscle

-smooth muscle-cardiac muscle-glands

special sensory receptors

somatic sensory receptors

visceral sensory receptors

Peripheral nervous systemincludes

Overview of the nervous system

Cellular Organization (neuron and neuroglia)

The nervous system includes all of the neural tissue

20billion nerve cells (neurons)100billion supporting cells (neuroglia)

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)

axonsynaptic terminals

Classification of neuron

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

anaxonicbipolar

unipolar 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

Oligodendrocytes

Microglia

Ependymal cells

Neuroglia of the PNS

Satellite cells

Schwann 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 membrane

Synaptic 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

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

Functional categories

The end