1. Organization of the Nervous System
Objectives
I will be able to:
List the general functions of the nervous system.
Explain the structural and functional classifications of the nervous system.
Define central nervous system and peripheral nervous system, and list the major parts of each.

2. Functions of the Nervous System
Sensory input – gathering information
to monitor changes occurring inside and outside the body (changes = stimuli)
Integration –
to process and interpret sensory input and decide if action is needed
Motor output –
A response to integrated stimuli
The response activates muscles or glands
Together, these functions work like a feedback loop.

3. Structural Classification of the Nervous System
The nervous system is composed of two separate systems:
Central nervous system (CNS)
Brain
Spinal cord
Peripheral nervous system (PNS)
Nerves outside the brain and spinal cord

4. Functional Classification of the Peripheral Nervous System
Sensory (afferent) division
Nerve fibers that carry information to the central nervous system
Motor (efferent) division
Nerve fibers that carry impulses away from the central nervous system

5. Functional Classification of the Peripheral Nervous System
Motor (efferent) division has two subdivisions:
Somatic nervous system = voluntary
Autonomic nervous system = involuntary
Has two parts:
sympathetic
parasympathetic

6. Organization of the Nervous System

7. 
How do the three functions of the nervous system work like a feedback loop?
Which system carries information to the CNS?
Which systems carries information away from the CNS?
Stimulus is received, evaluated, and responded to
Sensory
motor

8. Nervous Tissue: Support Cells (Neuroglia or Glia)
Nervous tissue is made up of two types of cells, supporting cells and neurons.
neuroglia: non-neuron tissue of the CNS that performs supportive and other functions for neurons
There are four types of neuroglia, astrocytes, microglia, ependymal cells, and oligodendrocytes.

9. Nervous Tissue: Support Cells (Neuroglia or Glia)
Astrocytes
Abundant, star-shaped cells
Brace neurons
Form barrier between capillaries and neurons
Control the chemical environment of the brain (CNS)

10. Nervous Tissue: Support Cells
Microglia (CNS)
Spider-like phagocytes
Dispose of debris
Ependymal cells (CNS)
Line cavities of the brain and spinal cord
Circulate cerebrospinal fluid

11. Nervous Tissue: Support Cells
Oligodendrocytes(CNS)
Produce myelin sheath around nerve fibers in the central nervous system

12.  Which support cell controls the chemical environment of the brain?
Which support cell disposes debris?
Which support cell creates the myelin sheath in brain cells?
astrocytes
microglia
oligodendrocytes

13. Nervous Tissue: Support Cells
glia: non-neuron tissue of the PNS that performs supportive and other functions for neurons
There are two types of glia in the PNS, Schwann cells and satellite cells.

14. Support Cells of the PNS
Satellite cells
Protect neuron cell bodies
Schwann cells
Form myelin sheath in the peripheral nervous system

15. Neuroglia vs. Neurons Neuroglia and glia can divide (mitosis).
Neurons cannot divide.
Most brain tumors are “gliomas.”
Most brain tumors involve the neuroglia cells, not the neurons.
Consider the role of cell division in cancer!

16. Nervous Tissue: Neurons
Neurons: cells of the nervous system specialized to transmit messages through-out the body
Different types of neurons have different structures but do share some features.
Common features of all neurons:
Cell body – nucleus and metabolic center of the cell
Processes – fibers that extend from the cell body (dendrites and axons)

17.  How are glia different from neuroglia?
What are the two types of glial cells?
Neuroglia = CNS, glia = PNS
Schwann cells and satellite cells

18. Neuron Anatomy The cell body is the metabolic center of a neuron.
Cell body contains a nucleus and the usual organelles in the surrounding cytoplasm.
The nucleus contains a large nucleolus.

19. Neuron Anatomy Processes outside the cell body:
Dendrites – conduct impulses toward the cell body (more than 1)
Axons – conduct impulses away from the cell body (only 1!)

20. Neuron Anatomy
Nissl bodies: consisting of granular ER and ribosomes that occurs in nerve cell bodies and dendrites and synthesize proteins.
neurofibrils: any of the long, thin microscopic fibrils that run through the body of a neuron and extend into the axon and dendrites
Neurofibrils are important in maintaining cell shape.
Neuroglia = CNS, glia = PNS
Schwann cells and satellite cells

21. Axons and Nerve Impulses
Axons end in axonal terminals
Axonal terminals contain vesicles with neurotransmitters
Axonal terminals are separated from the next neuron by a gap
synaptic cleft: the fluid-filled space at a synapse between axons and dendrites of a neuron
synapse: the region of communication between neurons

23. Nerve Fiber Coverings
Schwann cells – produce myelin sheaths in jelly-roll like fashion.
Nodes of Ranvier – gaps in myelin sheath between each Schwann cell along the axon.

24. Nerve Fiber Coverings
myelin: a white, fatty, lipid substance covering the axon of a neuron
Myelin Sheaths protect and insulate the axon fibers and increases the transmission rate of nerve impulses.
Axon fibers may be myelinated (having myelin sheaths) or unmyelinated (no myelin sheaths).

25. Neuron Cell Body Location
Most cell bodies are found in the central nervous system
ganglion: a group of nerve cell bodies located in the PNS
tract: a bundle of nerve fibers running through the CNS
Nerve fiber bundles running through the PNS are just called nerves.
gray matter: cell bodies and unmyelinated fibers
white matter: dense collections (tracts) of myelinated fibers in the CNS
nuclei: clusters of cell bodies within the white matter of the central nervous system

26.  What is the difference between gray matter and white matter?
Why would some of the CNS axons be unmyelinated?
Gray matter is unmyelinated, white matter is myelinated
Communication between brain cells is easier without the myelin sheaths

27. Application In Multiple Scleroses the myelin sheath is destroyed.
The myelin sheath hardens to a tissue called the scleroses.
This is considered an autoimmune disease.
Why does MS appear to affect the muscles?

28. 