1. The Nervous System

2. The Nervous System The master controlling and communication system of
the body

3. Three Overlapping Functions
Sensory Input
Monitors internal and external stimuli (Changes)
Afferent pathway to the brain
receptors
Integration
Processes and interprets information
Decides the appropriate response
Motor Output
Efferent pathway to effector organs (muscles or glands), effects a response

5. Organization of the Nervous System
Central Nervous System (CNS)
Brain and spinal cord
Dorsal body cavity
Integrating command center
Peripheral Nervous System (PNS)
Nerves to and from brain and spinal cord
Communication links to the CNS
Spinal nerves and cranial nerves

6. Peripheral Nervous System
Sensory Afferent Division
Impulses to the brain and spinal cord (CNS)
Monitors internal and external changes
Somatic afferent
Skin, skeletal muscle, joints
Visceral afferent
Organs within ventral body cavity

7. Peripheral Nervous System
Motor Efferent Division
From CNS to effector muscle, organs, and glands
Somatic efferent nervous system
Voluntary nervous system
Autonomic nervous system
Involuntary
Visceral motor nerve fibers (to smooth and cardiac muscle and glands)
Sympathetic (emergency situations)
Parasympathetic (conserves energy, nonemergency functions)

9. Classification
P. 224

11. THE CELLS OF THE NERVOUS SYSTEM

12. Nervous Tissue-Types of Cells
Two Principal Cell Types-
Neurons: excitable nerve cells
Supporting cells: Neuroglia “Nerve Glue”
Support, insulate, and protect neurons by surrounding and wrapping neurons.
Central nervous system supporting cells
Astrocytes
Microglia
Ependymal cells
Oligodendrocytes
Peripheral nervous system supporting cells
Satellite cells
Schwann cells

13. Neuroglia-Supporting Cells of CNS

14. Astrocytes Most abundant *Star-shaped
Radiating processes cover neurons and anchor them to adjacent blood vessels
Controls exchange between blood vessels and neurons
Determines capillary permeability

15. Astrocytes (Cont) Controls chemical environment around neurons
Cleans up leaked potassium and recycling released neurotransmitter
Guide migration of young neurons

16. Microglia Small, ovoid cells, with thorny processes (spider-like)
Branches monitor health of neurons
Migrate toward injured neuron
Transform into a macrophage when invading microorganisms or dead neurons are present and dispose of debris
Protective role because cells of immune system are denied access to CNS

17. Ependymal cells Simple squamous to columnar in shape
Line the cavities of the brain and spinal cord
Beating of their cilia circulates cerebrospinal fluid that cushions brain and spinal cord

18. Oligodendrocytes
Wrap cytoplasmic extensions around neurons and form myelin sheaths in CNS
Insulates and protects

19. Supporting Cells of the PNS
Satellite cells
Surround neuron cell bodies within ganglia
Protective and cushioning cells
Schwann cells
Surround and form myelin sheaths around larger nerve fibers
Functionally similar to oligodendrocytes

20. Highly specialized to transmit nerve impulses
Neurons
Highly specialized to transmit nerve impulses

21. Neurons Nerve cells Structural units of the nervous system
Special characteristics of neurons:
Conduct nerve impulses
Extreme longevity
Amiotic (exceptions: olfactory and hippocampus) (become injured and do not regenerate)
High metabolic rate: requires abundant oxygen and glucose
All Neurons have cell bodies and processes, plus three functional components: receptive or input region, conducting component, and secretory or output component.

22. Cell Body Metabolic center No centrioles
Ribosomes and rough ER (Nissl Substance)most active of any cell in the body
Plasma membrane acts as part of the receptive surface
Most located within the CNS (called nuclei)
Cell body collections in the PNS are called ganglia

24. Cell Processes
Brain and spinal cord (CNS) contain both cell bodies and their processes
The PNS consists chiefly of neuron processes
Bundles of neuron processes are called tracts (CNS) and nerves (PNS).
Dendrites
Short, tapering, hundreds/cell
Receptive (input) region; convey incoming messages(electrical signals) toward the cell body
Large surface area

25. Cell Processes Axon (conducting component)
One Axon (Single process) per neuron
Axon arises from axon hillock of cell body
Generates nerve impulses and transmits them away from the cell body
Long axons called nerve fibers
Axon terminals –created where the axon branches at the terminal end
terminal branches per axon
Axon terminals are the secretory portion—secretes neurotransmitters

26. Myelin Sheath (neurilemma)
Myelin: whitish, fatty material covering long nerve fibers; has waxy appearance
Protects and provides an electrical insulation covering for large and long nerve fibers
Increases speed of transmission of nerve impulses
Unmyelinated fibers conduct impulses slowly
Associated only with axons; Dendrites always unmyelinated
Formed by Schwann cells in PNS—made of concentric layers of cell membranes (no channel or carrier proteins) called the neurilemma

28. Myelin (Cont)
Nodes of Ranvier are the gaps between Schwann cells—regularly spaced
Oligodendrocytes form CNS myelin sheaths—coils around 60 fibers at the same time—no neurilemma because of the absence of coiling of cells
Regions of the brain and spinal cord with myelinated fibers called white matter.
Gray matter contains mostly cell bodies and unmyelinated fibers

29. Classification of Neurons
Structural Classification
Multipolar neurons
Bipolar neurons
Unipolar Neurons
Functional Classification
Sensory (afferent) neurons
Motor (efferent) neurons
Association (interneurons) neurons

33. Nervous Tissue Structures
p. 227
CELL BODY
DENDRITE

34. Nervous Tissue Structures
AXON
AXON TERMINAL

35. Nervous Tissue Structures
SCHWANN CELLS
NODES OF RANVIER